Mechanical design criteria for intervertebral disc tissue engineering.

PubMed

Nerurkar, Nandan L; Elliott, Dawn M; Mauck, Robert L

2010-04-19

Due to the inability of current clinical practices to restore function to degenerated intervertebral discs, the arena of disc tissue engineering has received substantial attention in recent years. Despite tremendous growth and progress in this field, translation to clinical implementation has been hindered by a lack of well-defined functional benchmarks. Because successful replacement of the disc is contingent upon replication of some or all of its complex mechanical behaviors, it is critically important that disc mechanics be well characterized in order to establish discrete functional goals for tissue engineering. In this review, the key functional signatures of the intervertebral disc are discussed and used to propose a series of native tissue benchmarks to guide the development of engineered replacement tissues. These benchmarks include measures of mechanical function under tensile, compressive, and shear deformations for the disc and its substructures. In some cases, important functional measures are identified that have yet to be measured in the native tissue. Ultimately, native tissue benchmark values are compared to measurements that have been made on engineered disc tissues, identifying where functional equivalence was achieved, and where there remain opportunities for advancement. Several excellent reviews exist regarding disc composition and structure, as well as recent tissue engineering strategies; therefore this review will remain focused on the functional aspects of disc tissue engineering. Copyright 2009 Elsevier Ltd. All rights reserved.

Translation of an Engineered Nanofibrous Disc-like Angle Ply Structure for Intervertebral Disc Replacement in a Small Animal Model

PubMed Central

Martin, John T.; Milby, Andrew H.; Chiaro, Joseph A.; Kim, Dong Hwa; Hebela, Nader M.; Smith, Lachlan J.; Elliott, Dawn M.; Mauck, Robert L.

2015-01-01

Intervertebral disc degeneration has been implicated in the etiology of low back pain; however the current surgical strategies for treating symptomatic disc disease are limited. A variety of materials have been developed to replace disc components, including the nucleus pulposus (NP), the annulus fibrosus (AF), and their combination into disc-like engineered constructs. We have previously shown that layers of electrospun poly(ε-caprolactone) scaffold, mimicking the hierarchical organization of the native AF, have functional parity with native tissue. Likewise, we have combined these structures with cell-seeded hydrogels (as an NP replacement) to form disc-like angle ply structures (DAPS). The objective of this study was to develop a model for the evaluation of DAPS in vivo. Through a series of studies, we developed a surgical approach to replace the rat caudal disc with an acellular DAPS and then stabilize the motion segment by external fixation. We then optimized cell infiltration into DAPS by including sacrificial poly(ethylene oxide) layers interspersed throughout the angle-ply structure. Our findings illustrate that DAPS are stable in the caudal spine, are infiltrated by cells from the peri-implant space, and that infiltration is expedited by providing additional routes for cell migration. These findings establish a new in vivo platform in which to evaluate and optimize the design of functional disc replacements. PMID:24560621

Ulf Fernström (1915-1985) and his Contributions to the Development of Artificial Disc Replacements.

PubMed

Fisahn, Christian; Burgess, Brittni; Iwanaga, Joe; Chapman, Jens R; Oskouian, Rod J; Tubbs, R Shane

2017-02-01

Artificial disc replacements, which serve the function of separating vertebrae to allow for proper spinal alignment, can help treat debilitating low back pain in patients who have failed other conservative methods of treatment. A Swedish surgeon, Ulf Fernström, was the pioneer of artificial disc replacement, and his contribution in the form of Fernström balls dramatically altered spinal surgery and technique by showing the proper technique and implant that should be used for areas requiring motion in many planes. Ulf Fernström created his artificial disc inspired by the movement of the hip and knee joints. His implants attempted to restore disc spacing and articulation in patients who had failed conservative measures of treatment. Fernström balls were the first implants of their kind and represent the first attempt at artificial disc replacement. However, many surgeons and researchers questioned Fernström balls, claiming that their lack of elastic properties could damage patients. Of the wide range of implants on the market for the intervertebral disc space, all designs and applications of products stem from the initial discovery made by Fernström, thus making him a pioneer in disc replacement. Copyright © 2016 Elsevier Inc. All rights reserved.

Cost-effectiveness of lumbar artificial intervertebral disc replacement: driven by the choice of comparator.

PubMed

Parkinson, Bonny; Goodall, Stephen; Thavaneswaran, Prema

2013-09-01

Lower back pain is a common and costly condition in Australia. This paper aims to conduct an economic evaluation of lumbar artificial intervertebral disc replacement (AIDR) compared with lumbar fusion for the treatment of patients suffering from significant axial back pain and/or radicular (nerve root) pain, secondary to disc degeneration or prolapse, who have failed conservative treatment. A cost-effectiveness approach was used to compare costs and benefits of AIDR to five fusion approaches. Resource use was based on Medicare Benefits Schedule claims data and expert opinion. Effectiveness and re-operation rates were based on published randomized controlled trials. The key clinical outcomes considered were narcotic medication discontinuation, achievement of overall clinical success, achievement of Oswestry Disability Index success and quality-adjusted life-years gained. AIDR was estimated to be cost-saving compared with fusion overall ($1600/patient); however, anterior lumbar interbody fusion and posterolateral fusion were less costly by $2155 and $807, respectively. The incremental cost-effectiveness depends on the outcome considered and the comparator. AIDR is potentially a cost-saving treatment for lumbar disc degeneration, although longer-term follow-up data are required to substantiate this claim. The incremental cost-effectiveness depends on the outcome considered and the comparator, and further research is required before any firm conclusions can be drawn. © 2012 The Authors. ANZ Journal of Surgery © 2012 Royal Australasian College of Surgeons.

Translation of an engineered nanofibrous disc-like angle-ply structure for intervertebral disc replacement in a small animal model.

PubMed

Martin, John T; Milby, Andrew H; Chiaro, Joseph A; Kim, Dong Hwa; Hebela, Nader M; Smith, Lachlan J; Elliott, Dawn M; Mauck, Robert L

2014-06-01

Intervertebral disc degeneration has been implicated in the etiology of low back pain; however, the current surgical strategies for treating symptomatic disc disease are limited. A variety of materials have been developed to replace disc components, including the nucleus pulposus (NP), the annulus fibrosus (AF) and their combination into disc-like engineered constructs. We have previously shown that layers of electrospun poly(ε-caprolactone) scaffold, mimicking the hierarchical organization of the native AF, can achieve functional parity with native tissue. Likewise, we have combined these structures with cell-seeded hydrogels (as an NP replacement) to form disc-like angle-ply structures (DAPS). The objective of this study was to develop a model for the evaluation of DAPS in vivo. Through a series of studies, we developed a surgical approach to replace the rat caudal disc with an acellular DAPS and then stabilized the motion segment via external fixation. We then optimized cell infiltration into DAPS by including sacrificial poly(ethylene oxide) layers interspersed throughout the angle-ply structure. Our findings illustrate that DAPS are stable in the caudal spine, are infiltrated by cells from the peri-implant space and that infiltration is expedited by providing additional routes for cell migration. These findings establish a new in vivo platform in which to evaluate and optimize the design of functional disc replacements. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Cervical facet force analysis after disc replacement versus fusion.

PubMed

Patel, Vikas V; Wuthrich, Zachary R; McGilvray, Kirk C; Lafleur, Matthew C; Lindley, Emily M; Sun, Derrick; Puttlitz, Christian M

2017-05-01

Cervical total disc replacement was developed to preserve motion and reduce adjacent-level degeneration relative to fusion, yet concerns remain that total disc replacement will lead to altered facet joint loading and long-term facet joint arthrosis. This study is intended to evaluate changes in facet contact force, pressure and surface area at the treated and superior adjacent levels before and after discectomy, disc replacement, and fusion. Ten fresh-frozen human cadaveric cervical spines were potted from C2 to C7 with pressure sensors placed into the facet joints of C3-C4 and C4-C5 via slits in the facet capsules. Moments were applied to the specimens to produce axial rotation, lateral bending and extension. Facet contact force and pressure were measured at both levels for intact, discectomy at C4-C5, disc replacement with ProDisc-C (Synthes Spine, West Chester, Pennsylvania, USA) at C4-C5, and anterior discectomy and fusion with Cervical Spine Locking Plate (Synthes Spine, West Chester, Pennsylvania, USA) at C4-C5. Facet contact area was calculated from the force and pressure measurements. An analysis of variance was used to determine significant differences with P-values <0.05 indicating significance. Facet contact force was elevated at the treated level under extension following both discectomy and disc replacement, while facet contact pressure and area were relatively unchanged. Facet contact force and area were decreased at the treated level following fusion for all three loading conditions. Total disc replacement preserved facet contact force for all scenarios except extension at the treated level, highlighting the importance of the anterior disco-ligamentous complex. This could promote treated-level facet joint disease. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biomechanics of a Fixed–Center of Rotation Cervical Intervertebral Disc Prosthesis

PubMed Central

Crawford, Neil R.; Baek, Seungwon; Sawa, Anna G.U.; Safavi-Abbasi, Sam; Sonntag, Volker K.H.; Duggal, Neil

2012-01-01

Background Past in vitro experiments studying artificial discs have focused on range of motion. It is also important to understand how artificial discs affect other biomechanical parameters, especially alterations to kinematics. The purpose of this in vitro investigation was to quantify how disc replacement with a ball-and-socket disc arthroplasty device (ProDisc-C; Synthes, West Chester, Pennsylvania) alters biomechanics of the spine relative to the normal condition (positive control) and simulated fusion (negative control). Methods Specimens were tested in multiple planes by use of pure moments under load control and again in displacement control during flexion-extension with a constant 70-N compressive follower load. Optical markers measured 3-dimensional vertebral motion, and a strain gauge array measured C4-5 facet loads. Results Range of motion and lax zone after disc replacement were not significantly different from normal values except during lateral bending, whereas plating significantly reduced motion in all loading modes (P < .002). Plating but not disc replacement shifted the location of the axis of rotation anteriorly relative to the intact condition (P < 0.01). Coupled axial rotation per degree of lateral bending was 25% ± 48% greater than normal after artificial disc replacement (P = .05) but 37% ± 38% less than normal after plating (P = .002). Coupled lateral bending per degree of axial rotation was 37% ± 21% less than normal after disc replacement (P < .001) and 41% ± 36% less than normal after plating (P = .001). Facet loads did not change significantly relative to normal after anterior plating or arthroplasty, except that facet loads were decreased during flexion in both conditions (P < .03). Conclusions In all parameters studied, deviations from normal biomechanics were less substantial after artificial disc placement than after anterior plating. PMID:25694869

Investigation of Product Performance of Al-Metal Matrix Composites Brake Disc using Finite Element Analysis

NASA Astrophysics Data System (ADS)

Fatchurrohman, N.; Marini, C. D.; Suraya, S.; Iqbal, AKM Asif

2016-02-01

The increasing demand of fuel efficiency and light weight components in automobile sectors have led to the development of advanced material parts with improved performance. A specific class of MMCs which has gained a lot of attention due to its potential is aluminium metal matrix composites (Al-MMCs). Product performance investigation of Al- MMCs is presented in this article, where an Al-MMCs brake disc is analyzed using finite element analysis. The objective is to identify the potentiality of replacing the conventional iron brake disc with Al-MMCs brake disc. The simulation results suggested that the MMCs brake disc provided better thermal and mechanical performance as compared to the conventional cast iron brake disc. Although, the Al-MMCs brake disc dissipated higher maximum temperature compared to cast iron brake disc's maximum temperature. The Al-MMCs brake disc showed a well distributed temperature than the cast iron brake disc. The high temperature developed at the ring of the disc and heat was dissipated in circumferential direction. Moreover, better thermal dissipation and conduction at brake disc rotor surface played a major influence on the stress. As a comparison, the maximum stress and strain of Al-MMCs brake disc was lower than that induced on the cast iron brake disc.

Lumbar Disc Replacement for Junctional Decompensation After Fusion Surgery: Clinical and Radiological Outcome at an Average Follow-Up of 33 Months

PubMed Central

Sliwa, Karen; Weinberg, Ian R.; Sweet, Barry MBE; de Villiers, Malan; Candy, Geoffrey P.

2007-01-01

Background Failed fusion surgery remains difficult to treat. Few published data on disc replacement surgery after failed fusion procedures exist. Our objective was to evaluate outcomes of junctional lumbar disc replacement after previous fusion surgery and to correlate outcome with radiological changes to parameters of sagittal balance. Methods Out of a single-center prospective registry of 290 patients with 404 lumbar disc replacements, 27 patients had had a previous lumbar fusion operation on 1 to 4 lumbar segments and had completed a mean follow- up of 33 months (range: 18–56). We correlated the clinical outcome measures (patient satisfaction, 10-point pain score, and Oswestry Disability Index [ODI] score) to parameters of spinal sagittal alignment (sacral tilt, pelvic tilt, pelvic incidence, and lumbar lordosis). Results Postoperative hospital stay averaged 3.3 days (range: 2–8). Previously-employed patients went back to their jobs with a mean of 32 days (range: 21–42) after the procedure. At the latest follow-up, 1 of the patients considered the outcome to be poor, 3 fair, 8 good, and 15 excellent. Twenty-four patients “would undergo the operation again.” Average pain score decreased from 9.1 ± 1.0 (SD) to 3.2 ± 2.1 (P < .01). Average ODI decreased from 50.2 ± 9.9 preoperatively to 21.7 ± 14.2 (P ≤ .01). We found the change in pelvic tilt to be an independent predictor of better clinical outcome by multivariate analysis (P < .05). Conclusions In patients with junctional failure adjacent to a previous posterolateral fusion, disc replacement at the junctional level(s), compared with osteotomy and fusion surgery, offers the advantage of maintaining segmental mobility and correcting the flat-back deformity through a single approach with less operative time and blood loss. Early- to intermediate-term results are promising. The influence of changes in spinal sagittal alignment on clinical outcome needs to be addressed in future research. Clinical Relevance This is the first study on “junctional disc replacement patients” correlating clinical outcome to changes in spinal/pelvic alignment. PMID:25802584

Valve assembly having remotely replaceable bearings

DOEpatents

Johnson, Evan R.; Tanner, David E.

1980-01-01

A valve assembly having remotely replaceable bearings is disclosed wherein a valve disc is supported within a flow duct for rotation about a pair of axially aligned bearings, one of which is carried by a spindle received within a diametral bore in the valve disc, and the other of which is carried by a bearing support block releasably mounted on the duct circumferentially of an annular collar on the valve disc coaxial with its diametrical bore. The spindle and bearing support block are adapted for remote removal to facilitate servicing or replacement of the valve disc support bearings.

An evaluation of information on the Internet of a new device: the lumbar artificial disc replacement.

PubMed

Garcia, Ryan M; Messerschmitt, Patrick J; Ahn, Nicholas U

2009-02-01

An analysis of websites, accessible to the public, was conducted pertaining to the lumbar artificial disc replacement. The objective was to investigate the content of information available on the Internet pertaining to the lumbar artificial disc replacement. The Internet is widely used by patients as an educational tool for health care information. Additionally, the Internet is used as a medium for direct-to-consumer marketing. Recent approval of the lumbar artificial disc replacement has led to the emergence of numerous websites offering information about this procedure. It is thought that patients can be influenced by information found on the Internet; therefore, it is imperative that this information be accurate and as complete as possible. Three commonly used search engines were used to locate 105 (35/search engine) websites providing information about the lumbar artificial disc replacement. Each website was evaluated with regard to authorship and content. Fifty-nine percent of the websites reviewed were authorized by a private physician group, 9% by an academic physician group, 6% by industry, 11% were news reports, and 15% were not otherwise categorized. Seventy-two percent offered a mechanism for direct contact and 30% provided clear patient selection criteria. Benefits were expressed in 87% of websites, whereas associated risks were described in 28% or less. European experiences were noted in 53%, whereas only 22% of websites detailed the current US experience. The results of this study demonstrate that much of the content of Internet-derived information pertaining to the lumbar artificial disc replacement is potentially misleading. Until long-term data are available, patients should be cautioned when using the Internet as a source for health care information, particularly with regard to the lumbar artificial disc replacement.

Transforaminal Endoscopic Decompression for Foot Drop Twelve Years After Lumbar Total Disc Replacment: Technical Note.

PubMed

Telfeian, Albert E; Oyelese, Adetokunbo; Fridley, Jared; Gokaslan, Ziya L

2018-05-19

Lumbar total disc replacement (LTDR) is considered for the treatment of lumbar degenerative disc disease with the hope that by preserving motion the long-term fusion complication of adjacent segment disease can be avoided. The complications of LTDR can be divided into approach-related and long-term complications. Very little has been described about the complications and treatment for complications more than 10 years after the device has been implanted. Here we describe a tranforaminal endoscopic discectomy procedure for a patient presenting with foot drop twelve years after a L5-S1 total disc replacement. Copyright © 2018. Published by Elsevier Inc.

ProDisc-L total disc replacement: a comparison of 1-level versus 2-level arthroplasty patients with a minimum 2-year follow-up.

PubMed

Hannibal, Matthew; Thomas, Derek J; Low, Jeffrey; Hsu, Ken Y; Zucherman, James

2007-10-01

This is a retrospective analysis of data that was collected prospectively from 2 concurrent FDA IDE lumbar arthroplasty clinical trials performed at a single center. To determine if there is a clinical difference between the 1-level ProDisc patients versus the 2-level ProDisc patients at a minimum of 2 years of follow-up. Marnay's work with ProDisc I prompted the U.S. Clinical Trials of the ProDisc II under the direction of the FDA. Disc replacement surgery in the United States has shown promising results for all types of prostheses up to 6 months. Marnay and colleagues showed that their results at 10 years were still promising, and they saw no significant difference between 1-level and multilevel disc replacements. The findings of Ipsen and colleagues suggest that multilevel arthroplasty cases may be less successful than disc replacement at a single level. Patients were part of the FDA clinical trial for the Prodisc II versus circumferential fusion study at a single institution. We identified 27 patients who received ProDisc at 1 level and 32 who received it at 2 levels with at least a 2-year follow-up, for a total of 59 patients. Unpaired t tests were performed on the mean results of Visual Analog Scale, Oswestry Disability Index, SF-36 Healthy Survey Physical Component Summary, and satisfaction using 10-cm line visual scale scores to determine a clinical difference if any between the 2 populations. While patients receiving ProDisc at 2 levels scored marginally lower in all evaluation indexes, score differences in each category were also found to hold no statistical significance. This study was unable to identify a statistically significant difference in outcome between 1- and 2-level ProDisc arthroplasty patients in a cohort from a single center. The equality of clinical effectiveness between 1- and 2-level ProDisc has yet to be determined.

Focal hypermobility observed in cervical arthroplasty with Mobi-C.

PubMed

Kerferd, Jack William; Abi-Hanna, David; Phan, Kevin; Rao, Prashanth; Mobbs, Ralph J

2017-12-01

In recent decades cervical arthroplasty, or cervical disc replacement, has been steadily increasing in popularity as a procedure for the treatment of degenerative pathologies of the cervical spine. This is based on an evolving body of literature that documents superior outcomes in cervical disc replacement over fusion, for both single and double level pathologies, in well selected patients. One of the more recent and popular implants currently on the market is the Mobi-C cervical artificial disc (LDR Medical; Troyes, France). In this paper we report on two cases where focal hypermobility was observed following total disc replacement using the Mobi-C cervical artificial disc. This is followed by a discussion as to potential contributing factors to this hypermobility in relation to both implant design, and operative technique, suggesting potential changes that might prevent this in future patients.

Cost-effectiveness of cervical total disc replacement vs fusion for the treatment of 2-level symptomatic degenerative disc disease.

PubMed

Ament, Jared D; Yang, Zhuo; Nunley, Pierce; Stone, Marcus B; Kim, Kee D

2014-12-01

Cervical total disc replacement (CTDR) was developed to treat cervical spondylosis, while preserving motion. While anterior cervical discectomy and fusion (ACDF) has been the standard of care for 2-level disease, a randomized clinical trial (RCT) suggested similar outcomes. Cost-effectiveness of this intervention has never been elucidated. To determine the cost-effectiveness of CTDR compared with ACDF. Data were derived from an RCT that followed up 330 patients over 24 months. The original RCT consisted of multi-institutional data including private and academic institutions. Using linear regression for the current study, health states were constructed based on the stratification of the Neck Disability Index and a visual analog scale. Data from the 12-item Short-Form Health Survey questionnaires were transformed into utilities values using the SF-6D mapping algorithm. Costs were calculated by extracting Diagnosis-Related Group codes from institutional billing data and then applying 2012 Medicare reimbursement rates. The costs of complications and return-to-work data were also calculated. A Markov model was built to evaluate quality-adjusted life-years (QALYs) for both treatment groups. The model adopted a third-party payer perspective and applied a 3% annual discount rate. Patients included in the original RCT had to be diagnosed as having radiculopathy or myeloradiculopathy at 2 contiguous levels from C3-C7 that was unresponsive to conservative treatment for at least 6 weeks or demonstrated progressive symptoms. Incremental cost-effectiveness ratio of CTDR compared with ACDF. A strong correlation (R2 = 0.6864; P < .001) was found by projecting a visual analog scale onto the Neck Disability Index. Cervical total disc replacement had an average of 1.58 QALYs after 24 months compared with 1.50 QALYs for ACDF recipients. Cervical total disc replacement was associated with $2139 greater average cost. The incremental cost-effectiveness ratio of CTDR compared with ACDF was $24,594 per QALY at 2 years. Despite varying input parameters in the sensitivity analysis, the incremental cost-effectiveness ratio value stays below the threshold of $50,000 per QALY in most scenarios (range, -$58,194 to $147,862 per QALY). The incremental cost-effectiveness ratio of CTDR compared with traditional ACDF is lower than the commonly accepted threshold of $50,000 per QALY. This remains true with varying input parameters in a robust sensitivity analysis, reaffirming the stability of the model and the sustainability of this intervention.

Biomechanics of Hybrid Anterior Cervical Fusion and Artificial Disc Replacement in 3-Level Constructs: An In Vitro Investigation

PubMed Central

Liao, Zhenhua; Fogel, Guy R.; Pu, Ting; Gu, Hongsheng; Liu, Weiqiang

2015-01-01

Background The ideal surgical approach for cervical disk disease remains controversial, especially for multilevel cervical disease. The purpose of this study was to investigate the biomechanics of the cervical spine after 3-level hybrid surgery compared with 3-level anterior cervical discectomy and fusion (ACDF). Material/Methods Eighteen human cadaveric spines (C2-T1) were evaluated under displacement-input protocol. After intact testing, a simulated hybrid construct or fusion construct was created between C3 to C6 and tested in the following 3 conditions: 3-level disc plate disc (3DPD), 3-level plate disc plate (3PDP), and 3-level plate (3P). Results Compared to intact, almost 65~80% of motion was successfully restricted at C3-C6 fusion levels (p<0.05). 3DPD construct resulted in slight increase at the 3 instrumented levels (p>0.05). 3PDP construct resulted in significant decrease of ROM at C3-C6 levels less than 3P (p<0.05). Both 3DPD and 3PDP caused significant reduction of ROM at the arthrodesis level and produced motion increase at the arthroplasty level. For adjacent levels, 3P resulted in markedly increased contribution of both upper and lower adjacent levels (p<0.05). Significant motion increases lower than 3P were only noted at partly adjacent levels in some conditions for 3DPD and 3PDP (p<0.05). Conclusions ACDF eliminated motion within the construct and greatly increased adjacent motion. Artificial cervical disc replacement normalized motion of its segment and adjacent segments. While hybrid conditions failed to restore normal motion within the construct, they significantly normalized motion in adjacent segments compared with the 3-level ACDF condition. The artificial disc in 3-level constructs has biomechanical advantages compared to fusion in normalizing motion. PMID:26529430

Biomechanics of Hybrid Anterior Cervical Fusion and Artificial Disc Replacement in 3-Level Constructs: An In Vitro Investigation.

PubMed

Liao, Zhenhua; Fogel, Guy R; Pu, Ting; Gu, Hongsheng; Liu, Weiqiang

2015-11-03

The ideal surgical approach for cervical disk disease remains controversial, especially for multilevel cervical disease. The purpose of this study was to investigate the biomechanics of the cervical spine after 3-level hybrid surgery compared with 3-level anterior cervical discectomy and fusion (ACDF). Eighteen human cadaveric spines (C2-T1) were evaluated under displacement-input protocol. After intact testing, a simulated hybrid construct or fusion construct was created between C3 to C6 and tested in the following 3 conditions: 3-level disc plate disc (3DPD), 3-level plate disc plate (3PDP), and 3-level plate (3P). Compared to intact, almost 65~80% of motion was successfully restricted at C3-C6 fusion levels (p<0.05). 3DPD construct resulted in slight increase at the 3 instrumented levels (p>0.05). 3PDP construct resulted in significant decrease of ROM at C3-C6 levels less than 3P (p<0.05). Both 3DPD and 3PDP caused significant reduction of ROM at the arthrodesis level and produced motion increase at the arthroplasty level. For adjacent levels, 3P resulted in markedly increased contribution of both upper and lower adjacent levels (p<0.05). Significant motion increases lower than 3P were only noted at partly adjacent levels in some conditions for 3DPD and 3PDP (p<0.05). ACDF eliminated motion within the construct and greatly increased adjacent motion. Artificial cervical disc replacement normalized motion of its segment and adjacent segments. While hybrid conditions failed to restore normal motion within the construct, they significantly normalized motion in adjacent segments compared with the 3-level ACDF condition. The artificial disc in 3-level constructs has biomechanical advantages compared to fusion in normalizing motion.

Does location of rotation center in artificial disc affect cervical biomechanics?

PubMed

Mo, Zhongjun; Zhao, Yanbin; Du, Chengfei; Sun, Yu; Zhang, Ming; Fan, Yubo

2015-04-15

A 3-dimensional finite element investigation. To compare the biomechanical performances of different rotation centers (RCs) in the prevalent artificial cervical discs. Various configurations are applied in artificial discs. Design parameters may influence the biomechanics of implanted spine. The RC is a primary variation in the popular artificial discs. Implantation of 5 prostheses was simulated at C5-C6 on the basis of a validated finite element cervical model (C3-C7). The prostheses included ball-in-socket design with a fixed RC located on the inferior endplate (BS-FI) and on the superior endplate (BS-FS), with a mobile RC at the inferior endplate (BS-MI), dual articulation with a mobile RC between the endplates (DA-M), and sliding articulation with various RCs (SA-V). The spinal motions in flexion and extension served as a displacement loading at the C3 vertebrae. Total disc replacements reduced extension moment. The ball-in-socket designs required less flexion moment, whereas the flexion stiffness of the spines with DA-M and SA-V was similar to that of the healthy model. The contributions of the implanted level to the global motions increased in the total disc replacements, except in the SA-V and DA-M models (in flexion). Ball-in-socket designs produced severe stress distributions in facet cartilage, whereas DA-M and SA-V produced more severe stress distribution on the bone-implant interface. Cervical stability was extremely affected in extension and partially affected in flexion by total disc replacement. With the prostheses with mobile RC, cervical curvature was readjusted under a low follower load. The SA-V and BS-FS designs exhibited better performances in the entire segmental stiffness and in the stability of the operative level than the BS-MI and BS-FI designs in flexion. The 5 designs demonstrated varying advantages relative to the stress distribution in the facet cartilages and on the bone-implant interface. 5.

Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease.

PubMed

Murrey, Daniel; Janssen, Michael; Delamarter, Rick; Goldstein, Jeffrey; Zigler, Jack; Tay, Bobby; Darden, Bruce

2009-04-01

Cervical total disc replacement (TDR) is intended to address radicular pain and preserve functional motion between two vertebral bodies in patients with symptomatic cervical disc disease (SCDD). The purpose of this trial is to compare the safety and efficacy of cervical TDR, ProDisc-C (Synthes Spine Company, L.P., West Chester, PA), to anterior cervical discectomy and fusion (ACDF) surgery for the treatment of one-level SCDD between C3 and C7. The study was conducted at 13 sites. A noninferiority design with a 1:1 randomization was used. Two hundred nine patients were randomized and treated (106 ACDF; 103 ProDisc-C). Visual analog scale (VAS) pain and intensity (neck and arm), VAS satisfaction, neck disability index (NDI), neurological exam, device success, adverse event occurrence, and short form-36 (SF-36) standardized questionnaires. A prospective, randomized, controlled clinical trial was performed. Patients were enrolled and treated in accordance with the US Food and Drug Administration (FDA)-approved protocol. Patients were assessed pre- and postoperatively at six weeks, 3, 6, 12, 18, and 24 months. Demographics were similar between the two patient groups (ProDisc-C: 42.1+/-8.4 years, 44.7% males; Fusion: 43.5 +/- 7.1 years, 46.2% males). The most commonly treated level was C5-C6 (ProDisc-C: 56.3%; Fusion=57.5%). NDI and SF-36 scores were significantly less compared with presurgery scores at all follow-up visits for both the treatment groups (p<.0001). VAS neck pain intensity and frequency as well as VAS arm pain intensity and frequency were statistically lower at all follow-up timepoints compared with preoperative levels (p<.0001) but were not different between treatments. Neurologic success (improvement or maintenance) was achieved at 24 months in 90.9% of ProDisc-C and 88.0% of Fusion patients (p=.638). Results show that at 24 months postoperatively, 84.4% of ProDisc-C patients achieved a more than or equal to 4 degrees of motion or maintained motion relative to preoperative baseline at the operated level. There was a statistically significant difference in the number of secondary surgeries with 8.5% of Fusion patients needing a re-operation, revision, or supplemental fixation within the 24 month postoperative period compared with 1.8% of ProDisc-C patients (p=.033). At 24 months, there was a statistically significant difference in medication usage with 89.9% of ProDisc-C patients not on strong narcotics or muscle relaxants, compared with 81.5% of Fusion patients. The results of this clinical trial demonstrate that ProDisc-C is a safe and effective surgical treatment for patients with disabling cervical radiculopathy because of single-level disease. By all primary and secondary measures evaluated, clinical outcomes after ProDisc-C implantation were either equivalent or superior to those same clinical outcomes after Fusion.

In Vitro Maturation and In Vivo Integration and Function of an Engineered Cell-Seeded Disc-like Angle Ply Structure (DAPS) for Total Disc Arthroplasty.

PubMed

Martin, J T; Gullbrand, S E; Kim, D H; Ikuta, K; Pfeifer, C G; Ashinsky, B G; Smith, L J; Elliott, D M; Smith, H E; Mauck, R L

2017-11-17

Total disc replacement with an engineered substitute is a promising avenue for treating advanced intervertebral disc disease. Toward this goal, we developed cell-seeded disc-like angle ply structures (DAPS) and showed through in vitro studies that these constructs mature to match native disc composition, structure, and function with long-term culture. We then evaluated DAPS performance in an in vivo rat model of total disc replacement; over 5 weeks in vivo, DAPS maintained their structure, prevented intervertebral bony fusion, and matched native disc mechanical function at physiologic loads in situ. However, DAPS rapidly lost proteoglycan post-implantation and did not integrate into adjacent vertebrae. To address this, we modified the design to include polymer endplates to interface the DAPS with adjacent vertebrae, and showed that this modification mitigated in vivo proteoglycan loss while maintaining mechanical function and promoting integration. Together, these data demonstrate that cell-seeded engineered discs can replicate many characteristics of the native disc and are a viable option for total disc arthroplasty.

Surgical Treatment for Discogenic Low-Back Pain: Lumbar Arthroplasty Results in Superior Pain Reduction and Disability Level Improvement Compared With Lumbar Fusion

PubMed Central

2007-01-01

Background The US Food and Drug Administration approved the Charité artificial disc on October 26, 2004. This approval was based on an extensive analysis and review process; 20 years of disc usage worldwide; and the results of a prospective, randomized, controlled clinical trial that compared lumbar artificial disc replacement to fusion. The results of the investigational device exemption (IDE) study led to a conclusion that clinical outcomes following lumbar arthroplasty were at least as good as outcomes from fusion. Methods The author performed a new analysis of the Visual Analog Scale pain scores and the Oswestry Disability Index scores from the Charité artificial disc IDE study and used a nonparametric statistical test, because observed data distributions were not normal. The analysis included all of the enrolled subjects in both the nonrandomized and randomized phases of the study. Results Subjects from both the treatment and control groups improved from the baseline situation (P < .001) at all follow-up times (6 weeks to 24 months). Additionally, these pain and disability levels with artificial disc replacement were superior (P < .05) to the fusion treatment at all follow-up times including 2 years. Conclusions The a priori statistical plan for an IDE study may not adequately address the final distribution of the data. Therefore, statistical analyses more appropriate to the distribution may be necessary to develop meaningful statistical conclusions from the study. A nonparametric statistical analysis of the Charité artificial disc IDE outcomes scores demonstrates superiority for lumbar arthroplasty versus fusion at all follow-up time points to 24 months. PMID:25802574

The Discover artificial disc replacement versus fusion in cervical radiculopathy--a randomized controlled outcome trial with 2-year follow-up.

PubMed

Skeppholm, Martin; Lindgren, Lars; Henriques, Thomas; Vavruch, Ludek; Löfgren, Håkan; Olerud, Claes

2015-06-01

Several previous studies comparing artificial disc replacement (ADR) and fusion have been conducted with cautiously positive results in favor of ADR. This study is not, in contrast to most previous studies, an investigational device exemption study required by the Food and Drug Administration for approval to market the product in the United States. This study was partially funded with unrestricted institutional research grants by the company marketing the artificial disc used in this study. To compare outcomes between the concepts of an artificial disc to treatment with anterior cervical decompression and fusion (ACDF) and to register complications associated to the two treatments during a follow-up time of 2 years. This is a randomized controlled multicenter trial, including three spine centers in Sweden. The study included patients seeking care for cervical radiculopathy who fulfilled inclusion criteria. In total, 153 patients were included. Self-assessment with Neck Disability Index (NDI) as a primary outcome variable and EQ-5D and visual analog scale as secondary outcome variables. Patients were randomly allocated to either treatment with the Depuy Discover artificial disc or fusion with iliac crest bone graft and plating. Randomization was blinded to both patient and caregivers until time for implantation. Adverse events, complications, and revision surgery were registered as well as loss of follow-up. Data were available in 137 (91%) of the included and initially treated patients. Both groups improved significantly after surgery. NDI changed from 63.1 to 39.8 in an intention-to-treat analysis. No statistically significant difference between the ADR and the ACDF groups could be demonstrated with NDI values of 39.1 and 40.1, respectively. Nor in secondary outcome measures (EQ-5D and visual analog scale) could any statistically significant differences be demonstrated between the groups. Nine patients in the ADR group and three in the fusion group underwent secondary surgery because of various reasons. Two patients in each group underwent secondary surgery because of adjacent segment pathology. Complication rates were not statistically significant between groups. Artificial disc replacement did not result in better outcome compared to fusion measured with NDI 2 years after surgery. Copyright © 2015 Elsevier Inc. All rights reserved.

Hybrids: good for cars and the environment-are they good for the spine too?

PubMed

Bono, Christopher M

2009-10-01

Erkan S, Rivera Y, Wu C, et al. Biomechanical comparison of a two-level Maverick disc replacement with a hybrid one-level disc replacement and one-level anterior lumbar interbody fusion. Spine J 2009;9:830-835 (in this issue).

[LOCATION CHANGE OF ROTATION CENTER AFTER SINGLE SEGMENTAL CERVICAL DISC REPLACEMENT WITH ProDisc-C].

PubMed

Lou, Jigang; Liu, Hao; Rong, Xin; Gong, Quan; Song, Yueming; Li, Tao

2015-01-01

To evaluate the effectiveness of the single segmental cervical disc replacement with ProDisc-C, and to explore the location change of the flexion/extension center of rotation (COR) of the target level as well as its clinical significance. Between June 2010 and February 2012, 23 patients underwent single segmental cervical disc replacement with ProDisc-C, and the clinical data were retrospectively analyzed. Of 23 patients, 9 were male, and 14 were female with the age range from 27 to 65 years (mean, 45 years), and the disease duration ranged from 10 to 84 months (mean, 25 months). There were 15 patients with radiculopathy, 5 patients with myelopathy, and 3 patients with mixed cervical spondylosis. The involved segments were C4,5 in 5 cases, C5,6 in 14 cases, and C6,7 in 4 cases. Japanese Orthopaedic Association (JOA) score and neck disability index (NDI) were adopted to evaluate the effectiveness. Preoperative and Postoperative radiographic parameters, such as cervical overall range of motion (ROM), target segmental ROM, the adjacent segmental ROM, and intervertebral height were compared. Besides, the location changes of the COR of the target level were further analyzed by the alteration of its coordinates (COR-X, COR-Y), and the relationships between the location changes of the COR and the effectiveness or the radiographic results were analyzed. All the operations were completed successfully; 1 case had hoarseness after operation, which disappeared at 3 months after operation. All cases were followed up 18.3 months on average (range, 6-36 months). There was no device migration, loosening, subsidence, or fracture at last follow-up. The JOA score increased significantly and the NDI score decreased significantly at last follow-up when compared with preoperative scores (P < 0.05). No difference was found in the cervical overall ROM, target segmental ROM, the adjacent segmental ROM, and the COR-Y of the target level between pre-operation and last follow-up (P > 0.05); while the intervertebral height and the COR-X increased significantly (P < 0.05). The change of the COR-X had no obvious correlation with the postoperative JOA, NDI, and target segmental ROM (P > 0.05). According to whether the difference of the COR-X between pre- and post-operation was less than the average value 1.86 mm or not, the patients were divided into 2 groups; significant difference was shown in the postoperative target segmental ROM between 2 groups (P < 0.05), but no significant difference was found in the postoperative JOA, NDI, cervical overall ROM, adjacent segmental ROM, and the intervertebral height between 2 groups (P > 0.05). Single segmental cervical disc replacement with ProDisc-C can obtain satisfactory outcomes. The cervical overall ROM, target segmental ROM, and adjacent segmental ROM can be effectively maintained, and the intervertebral height is increased. The location of the flexion/extension COR of the target segment shifts forward after insertion of the ProDisc-C prosthesis, and the postoperative target segmental ROM becomes smaller as the distance of the displacement of the COR becomes greater.

37 CFR 1.52 - Language, paper, writing, margins, compact disc specifications.

Code of Federal Regulations, 2013 CFR

2013-07-01

... permanent dark ink or its equivalent; and (v) Presented in a form having sufficient clarity and contrast... statement that the replacement compact disc contains no new matter. The compact disc and copy must be...

Cervical disc arthroplasty: Pros and cons.

PubMed

Moatz, Bradley; Tortolani, P Justin

2012-01-01

Cervical disc arthroplasty has emerged as a promising potential alternative to anterior cervical discectomy and fusion (ACDF) in appropriately selected patients. Despite a history of excellent outcomes after ACDF, the question as to whether a fusion leads to adjacent segment degeneration remains unanswered. Numerous US investigational device exemption trials comparing cervical arthroplasty to fusion have been conducted to answer this question. This study reviews the current research regarding cervical athroplasty, and emphasizes both the pros and cons of arthroplasty as compared with ACDF. Early clinical outcomes show that cervical arthroplasty is as effective as the standard ACDF. However, this new technology is also associated with an expanding list of novel complications. Although there is no definitive evidence that cervical disc replacement reduces the incidence of adjacent segment degeneration, it does show other advantages; for example, faster return to work, and reduced need for postoperative bracing.

An evaluation of information on the internet about a new device: the cervical artificial disc replacement.

PubMed

Qureshi, Sheeraz A; Koehler, Steven M; Lin, James D; Bird, Justin; Garcia, Ryan M; Hecht, Andrew C

2012-05-01

Cross-sectional survey. The objective of this study was to investigate the authorship, content, and quality of information available to the public on the Internet pertaining to the cervical artificial disc replacement device. The Internet is widely used by patients as an educational tool for health care information. In addition, the Internet is used as a medium for direct-to-consumer marketing. Increasing interest in cervical artificial disc replacement has led to the emergence of numerous Web sites offering information about this procedure. It is thought that patients can be influenced by information found on the Internet. A cross section of Web sites accessible to the general public was surveyed. Three commonly used search engines were used to locate 150 (50/search engine) Web sites providing information about the cervical artificial disc replacement. Each Web site was evaluated with regard to authorship and content. Fifty-three percent of the Web sites reviewed were authorized by a private physician group, 4% by an academic physician group, 13% by industry, 16% were news reports, and 14% were not otherwise categorized. Sixty-five percent of Web sites offered a mechanism for direct contact and 19% provided clear patient eligibility criteria. Benefits were expressed in 80% of Web sites, whereas associated risks were described in 35% or less. European experiences were noted in 17% of Web sites, whereas only 9% of Web sites detailed the current US experience. CONCLUSION.: The results of this study demonstrate that much of the content of the Internet-derived information pertaining to the cervical artificial disc replacement is for marketing purposes and may not represent unbiased information. Until we can confirm the content on a Web site to be accurate, patients should be cautioned when using the Internet as a source for health care information related to cervical disc replacement.

37 CFR 1.52 - Language, paper, writing, margins, compact disc specifications.

Code of Federal Regulations, 2014 CFR

2014-07-01

... by a typewriter or machine printer in permanent dark ink or its equivalent; and (v) Presented in a... accompanied by a statement that the replacement compact disc contains no new matter. The compact disc and copy...

Barriers to and Budget Impact of Lumbar Total Disc Replacement Utilization.

PubMed

Sandhu, Faheem; Blumenthal, Scott; Grunch, Betsy; Kimball, Bent; Ferko, Nicole; Hollmann, Sarah

2017-12-15

: Evidence on the favorable efficacy, safety, and cost effectiveness of lumbar total disc replacement (TDR) compared with fusion for lumbar degenerative disc disease is mounting; however, a key barrier identified for TDR utilization is lack of coverage by US health insurers. Although economic considerations in a fee-for-service model should not be a determining factor in patient access, concerns regarding the budget impact of lumbar TDR surgery may unfortunately underlie coverage decisions. On the basis of the data available and economic modeling, the panel agreed that there is no indication that there would be a dramatic increase in patients seeking lumbar TDR. Considering several possible scenarios on potential growth in TDR utilization with coverage, as well as growth in the overall surgical pool of patients, economic modeling demonstrated that adoption of lumbar TDR would result in minimal or no budget impact for commercial insurance plans. Considering these model results and the economic literature, the panel concluded that adopting lumbar TDR within a coverage policy is expected to remain cost neutral for the insurer.

The Correlation between Insertion Depth of Prodisc-C Artificial Disc and Postoperative Kyphotic Deformity: Clinical Importance of Insertion Depth of Artificial Disc.

PubMed

Lee, Do-Youl; Kim, Se-Hoon; Suh, Jung-Keun; Cho, Tai-Hyoung; Chung, Yong-Gu

2012-09-01

This study was designed to investigate the correlation between insertion depth of artificial disc and postoperative kyphotic deformity after Prodisc-C total disc replacement surgery, and the range of artificial disc insertion depth which is effective in preventing postoperative whole cervical or segmental kyphotic deformity. A retrospective radiological analysis was performed in 50 patients who had undergone single level total disc replacement surgery. Records were reviewed to obtain demographic data. Preoperative and postoperative radiographs were assessed to determine C2-7 Cobb's angle and segmental angle and to investigate postoperative kyphotic deformity. A formula was introduced to calculate insertion depth of Prodisc-C artificial disc. Statistical analysis was performed to search the correlation between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity, and to estimate insertion depth of Prodisc-C artificial disc to prevent postoperative kyphotic deformity. In this study no significant statistical correlation was observed between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity regarding C2-7 Cobb's angle. Statistical correlation between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity was observed regarding segmental angle (p<0.05). It failed to estimate proper insertion depth of Prodisc-C artificial disc effective in preventing postoperative kyphotic deformity. Postoperative segmental kyphotic deformity is associated with insertion depth of Prodisc-C artificial disc. Anterior located artificial disc leads to lordotic segmental angle and posterior located artificial disc leads to kyphotic segmental angle postoperatively. But C2-7 Cobb's angle is not affected by artificial disc location after the surgery.

78 FR 24426 - Orthopaedic and Rehabilitation Devices Panel of the Medical Devices Advisory Committee; Notice of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-25

... application for the Kineflex/C Cervical Artificial Disc sponsored by SpinalMotion. The Kineflex/C is a metal-on-metal (cobalt chrome molybdenum alloy) cervical total disc replacement device. The Kineflex/C is... degenerative disc disease (DDD) where DDD is defined as discogenic back pain with degeneration of the disc as...

Fatigue based design and analysis of wheel hub for Student formula car by Simulation Approach

NASA Astrophysics Data System (ADS)

Gowtham, V.; Ranganathan, A. S.; Satish, S.; Alexis, S. John; Siva kumar, S.

2016-09-01

In the existing design of Wheel hub used for Student formula cars, the brake discs cannot be removed easily since the disc is mounted in between the knuckle and hub. In case of bend or any other damage to the disc, the replacement of the disc becomes difficult. Further using OEM hub and knuckle that are used for commercial vehicles will result in increase of unsprung mass, which should be avoided in Student formula cars for improving the performance. In this design the above mentioned difficulties have been overcome by redesigning the hub in such a way that the brake disc could be removed easily by just removing the wheel and the caliper and also it will have reduced weight when compared to existing OEM hub. A CAD Model was developed based on the required fatigue life cycles. The forces acting on the hub were calculated and linear static structural analysis was performed on the wheel hub for three different materials using ANSYS Finite Element code V 16.2. The theoretical fatigue strength was compared with the stress obtained from the structural analysis for each material.

Cervical disc arthroplasty: Pros and cons

PubMed Central

Moatz, Bradley; Tortolani, P. Justin

2012-01-01

Background: Cervical disc arthroplasty has emerged as a promising potential alternative to anterior cervical discectomy and fusion (ACDF) in appropriately selected patients. Despite a history of excellent outcomes after ACDF, the question as to whether a fusion leads to adjacent segment degeneration remains unanswered. Numerous US investigational device exemption trials comparing cervical arthroplasty to fusion have been conducted to answer this question. Methods: This study reviews the current research regarding cervical athroplasty, and emphasizes both the pros and cons of arthroplasty as compared with ACDF. Results: Early clinical outcomes show that cervical arthroplasty is as effective as the standard ACDF. However, this new technology is also associated with an expanding list of novel complications. Conclusion: Although there is no definitive evidence that cervical disc replacement reduces the incidence of adjacent segment degeneration, it does show other advantages; for example, faster return to work, and reduced need for postoperative bracing. PMID:22905327

Prospective study on serum metal levels in patients with metal-on-metal lumbar disc arthroplasty.

PubMed

Gornet, Matthew F; Burkus, J K; Harper, M L; Chan, F W; Skipor, A K; Jacobs, J J

2013-04-01

Metal-on-metal total disc replacement is a recent alternative treatment for degenerative disc disease. Wear and corrosion of these implants can lead to local and systemic transport of metal debris. This prospective longitudinal study examined the serum chromium and cobalt levels in 24 patients with cobalt-chromium alloy metal-on-metal lumbar disc replacements. Serum was assayed for chromium (Cr) and cobalt (Co) using high-resolution inductively-coupled plasma-mass spectrometry. Detection limits were 0.015 ng/mL for Cr and 0.04 ng/mL for Co. Median serum Co levels at pre-op, 3, 6, 12, 24, and 36-months post-op were 0.10, 1.03, 0.96, 0.98, 0.67, and 0.52 ng/mL, respectively. Median serum Cr levels were 0.06, 0.49, 0.65, 0.43, 0.52, and 0.50 ng/mL, respectively. In general, these results indicated that serum Co and Cr levels are elevated at all postoperative time points and are of the same order of magnitude as those observed in well-functioning metal-on-metal surface replacements of the hip and in metal-on-metal total hip replacements at similar postoperative time points.

Defining the Ideal Lumbar Total Disc Replacement Patient and Standard of Care.

PubMed

Gornet, Matthew; Buttermann, Glenn; Guyer, Richard; Yue, James; Ferko, Nicole; Hollmann, Sarah

2017-12-15

: Lumbar total disc replacement, now in use since 2004, was determined by the panel to be a standard of care for the treatment of symptomatic single-level lumbar degenerative disc disease in the active patient subpopulation as outlined by the investigational device exemption study criteria. The large body of evidence supporting this statement, including surgeons' experiences, was presented and discussed. Consensus statements focusing on decision-making criteria reflected that efficacy, long-term safety, clinical outcomes with validated measures, and cost-effectiveness should form the basis of decision-making by payers. Diagnostic challenges with lumbar degenerative disc disease patients were discussed among the panel, and it was concluded that although variably used among surgeons, reliable tools exist to appropriately diagnose discogenic back pain.

Cost Utility Analysis of the Cervical Artificial Disc vs Fusion for the Treatment of 2-Level Symptomatic Degenerative Disc Disease: 5-Year Follow-up.

PubMed

Ament, Jared D; Yang, Zhuo; Nunley, Pierce; Stone, Marcus B; Lee, Darrin; Kim, Kee D

2016-07-01

The cervical total disc replacement (cTDR) was developed to treat cervical degenerative disc disease while preserving motion. Cost-effectiveness of this intervention was established by looking at 2-year follow-up, and this update reevaluates our analysis over 5 years. Data were derived from a randomized trial of 330 patients. Data from the 12-Item Short Form Health Survey were transformed into utilities by using the SF-6D algorithm. Costs were calculated by extracting diagnosis-related group codes and then applying 2014 Medicare reimbursement rates. A Markov model evaluated quality-adjusted life years (QALYs) for both treatment groups. Univariate and multivariate sensitivity analyses were conducted to test the stability of the model. The model adopted both societal and health system perspectives and applied a 3% annual discount rate. The cTDR costs $1687 more than anterior cervical discectomy and fusion (ACDF) over 5 years. In contrast, cTDR had $34 377 less productivity loss compared with ACDF. There was a significant difference in the return-to-work rate (81.6% compared with 65.4% for cTDR and ACDF, respectively; P = .029). From a societal perspective, the incremental cost-effective ratio (ICER) for cTDR was -$165 103 per QALY. From a health system perspective, the ICER for cTDR was $8518 per QALY. In the sensitivity analysis, the ICER for cTDR remained below the US willingness-to-pay threshold of $50 000 per QALY in all scenarios (-$225 816 per QALY to $22 071 per QALY). This study is the first to report the comparative cost-effectiveness of cTDR vs ACDF for 2-level degenerative disc disease at 5 years. The authors conclude that, because of the negative ICER, cTDR is the dominant modality. ACDF, anterior cervical discectomy and fusionAWP, average wholesale priceCE, cost-effectivenessCEA, cost-effectiveness analysisCPT, Current Procedural TerminologycTDR, cervical total disc replacementCUA, cost-utility analysisDDD, degenerative disc diseaseDRG, diagnosis-related groupFDA, US Food and Drug AdministrationICER, incremental cost-effectiveness ratioIDE, Investigational Device ExemptionNDI, neck disability indexQALY, quality-adjusted life yearsRCT, randomized controlled trialRTW, return-to-workSF-12, 12-Item Short Form Health SurveyVAS, visual analog scaleWTP, willingness-to-pay.

Intervertebral disc regeneration or repair with biomaterials and stem cell therapy--feasible or fiction?

PubMed

Chan, Samantha C W; Gantenbein-Ritter, Benjamin

2012-05-31

The "gold standard" for treatment of intervertebral disc herniations and degenerated discs is still spinal fusion, corresponding to the saying "no disc - no pain". Mechanical prostheses, which are currently implanted, do only have medium outcome success and have relatively high re-operation rates. Here, we discuss some of the biological intervertebral disc replacement approaches, which can be subdivided into at least two classes in accordance to the two different tissue types, the nucleus pulposus (NP) and the annulus fibrosus (AF). On the side of NP replacement hydrogels have been extensively tested in vitro and in vivo. However, these gels are usually a trade-off between cell biocompatibility and load-bearing capacity, hydrogels which fulfill both are still lacking. On the side of AF repair much less is known and the question of the anchoring of implants is still to be addressed. New hope for cell therapy comes from developmental biology investigations on the existence of intervertebral disc progenitor cells, which would be an ideal cell source for cell therapy. Also notochordal cells (remnants of the embryonic notochord) have been recently pushed back into focus since these cells have regenerative potential and can activate disc cells. Growth factor treatment and molecular therapies could be less problematic. The biological solutions for NP and AF replacement are still more fiction than fact. However, tissue engineering just scratched the tip of the iceberg, more satisfying solutions are yet to be added to the biomedical pipeline.

Biomechanics of Artificial Disc Replacements Adjacent to a 2-Level Fusion in 4-Level Hybrid Constructs: An In Vitro Investigation

PubMed Central

Liao, Zhenhua; Fogel, Guy R.; Wei, Na; Gu, Hongsheng; Liu, Weiqiang

2015-01-01

Background The ideal procedure for multilevel cervical degenerative disc diseases remains controversial. Recent studies on hybrid surgery combining anterior cervical discectomy and fusion (ACDF) and artificial cervical disc replacement (ACDR) for 2-level and 3-level constructs have been reported in the literature. The purpose of this study was to estimate the biomechanics of 3 kinds of 4-level hybrid constructs, which are more likely to be used clinically compared to 4-level arthrodesis. Material/Methods Eighteen human cadaveric spines (C2–T1) were evaluated in different testing conditions: intact, with 3 kinds of 4-level hybrid constructs (hybrid C3–4 ACDR+C4–6 ACDF+C6–7ACDR; hybrid C3–5ACDF+C5–6ACDR+C6–7ACDR; hybrid C3–4ACDR+C4–5ACDR+C5–7ACDF); and 4-level fusion. Results Four-level fusion resulted in significant decrease in the C3–C7 ROM compared with the intact spine. The 3 different 4-level hybrid treatment groups caused only slight change at the instrumented levels compared to intact except for flexion. At the adjacent levels, 4-level fusion resulted in significant increase of contribution of both upper and lower adjacent levels. However, for the 3 hybrid constructs, significant changes of motion increase far lower than 4P at adjacent levels were only noted in partial loading conditions. No destabilizing effect or hypermobility were observed in any 4-level hybrid construct. Conclusions Four-level fusion significantly eliminated motion within the construct and increased motion at the adjacent segments. For all 3 different 4-level hybrid constructs, ACDR normalized motion of the index segment and adjacent segments with no significant hypermobility. Compared with the 4-level ACDF condition, the artificial discs in 4-level hybrid constructs had biomechanical advantages compared to fusion in normalizing adjacent level motion. PMID:26694835

Biomechanics of Artificial Disc Replacements Adjacent to a 2-Level Fusion in 4-Level Hybrid Constructs: An In Vitro Investigation.

PubMed

Liao, Zhenhua; Fogel, Guy R; Wei, Na; Gu, Hongsheng; Liu, Weiqiang

2015-12-23

BACKGROUND The ideal procedure for multilevel cervical degenerative disc diseases remains controversial. Recent studies on hybrid surgery combining anterior cervical discectomy and fusion (ACDF) and artificial cervical disc replacement (ACDR) for 2-level and 3-level constructs have been reported in the literature. The purpose of this study was to estimate the biomechanics of 3 kinds of 4-level hybrid constructs, which are more likely to be used clinically compared to 4-level arthrodesis. MATERIAL AND METHODS Eighteen human cadaveric spines (C2-T1) were evaluated in different testing conditions: intact, with 3 kinds of 4-level hybrid constructs (hybrid C3-4 ACDR+C4-6 ACDF+C6-7ACDR; hybrid C3-5ACDF+C5-6ACDR+C6-7ACDR; hybrid C3-4ACDR+C4-5ACDR+C5-7ACDF); and 4-level fusion. RESULTS Four-level fusion resulted in significant decrease in the C3-C7 ROM compared with the intact spine. The 3 different 4-level hybrid treatment groups caused only slight change at the instrumented levels compared to intact except for flexion. At the adjacent levels, 4-level fusion resulted in significant increase of contribution of both upper and lower adjacent levels. However, for the 3 hybrid constructs, significant changes of motion increase far lower than 4P at adjacent levels were only noted in partial loading conditions. No destabilizing effect or hypermobility were observed in any 4-level hybrid construct. CONCLUSIONS Four-level fusion significantly eliminated motion within the construct and increased motion at the adjacent segments. For all 3 different 4-level hybrid constructs, ACDR normalized motion of the index segment and adjacent segments with no significant hypermobility. Compared with the 4-level ACDF condition, the artificial discs in 4-level hybrid constructs had biomechanical advantages compared to fusion in normalizing adjacent level motion.

Comparative Study Between M6-C and Mobi-C Cervical Artificial Disc Replacement: Biomechanical Outcomes and Comparison with Normative Data.

PubMed

Pham, My; Phan, Kevin; Teng, Ian; Mobbs, Ralph J

2018-05-01

Cervical spondylosis affects a huge proportion of the middle-aged population. Degenerative changes can occur in multiple regions of the cervical spine typically affecting the joints, intervertebral discs and endplates. These changes lead to compression of adjacent nervous structures, which results in radiculopathic and myelopathic pain. Various treatment modalities are currently available with non-surgical approaches the initial go to if there is no symptomatic cord compression. Anterior cervical discectomy and fusion, or arthroplasty are the two common surgical approaches if non-surgical treatments fail to relieve symptoms of the patients or there are signs of central cord compression. However, studies have shown that there is an increased risk of adjacent segment disease related to fusion. Cervical disc arthroplasty aims to restore normal range of motion (ROM) in patients with pain and disability due to degenerative disc disease resistant to conservative care. Two common disc prostheses used include M6-C and Mobi-C. Both prostheses comprise a mobile polymer segment sandwiched between two metal endplates with mechanisms resembling an actual intervertebral disc. This study aims to compare the kinematics associated with these prostheses, against the normal range of motion in the non-degenerative population. Patients who underwent M6-C or Mobi-C disc replacements by the senior author from 2012 to 2015 were identified at a single tertiary institution. Routine 3-month postoperative lateral radiographs were analyzed for flexion and extension ROM angles at the involved vertebral level by two independent authors. Data was compared to previous published studies investigating cervical spine ROM of asymptomatic patients. There was no statistical significance in the difference of overall flexion range between M6-C and Mobi-C prostheses. However, overall range of extension of Mobi-C was greater compared to M6-C (P = 0.028). At C 5-6 , the range of flexion for both implants were similar but lesser compared to asymptomatic patients (P < 0.001). Range of extension was greater in the Mobi-C group (14.2° ± 5.1°) compared to the M6-C (7.3° ± 4.6°) (P = 0.0009). At C 6-7 , there were no statistical differences in both range of flexion and extension between the two prostheses and asymptomatic patients (P > 0.05). The early results regarding restoration of ROM following cervical arthroplasty using either M6-C or Mobi-C prosthesis are encouraging. Long-term follow-up studies are necessary to observe the change in ROM over time with physiological loading and wear patterns. © 2018 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces.

PubMed

MacBarb, Regina F; Lindsey, Derek P; Bahney, Chelsea S; Woods, Shane A; Wolfe, Mark L; Yerby, Scott A

2017-01-01

An aging society and concomitant rise in the incidence of impaired bone health have led to the need for advanced osteoconductive spinal implant surfaces that promote greater biological fixation ( e.g. for interbody fusion cages, sacroiliac joint fusion implants, and artificial disc replacements). Additive manufacturing, i.e. 3D-printing, may improve bone integration by generating biomimetic spinal implant surfaces that mimic bone morphology. Such surfaces may foster an enhanced cellular response compared to traditional implant surfacing processes. This study investigated the response of human osteoblasts to additive manufactured (AM) trabecular-like titanium implant surfaces compared to traditionally machined base material with titanium plasma spray (TPS) coated surfaces, with and without a nanocrystalline hydroxyapatite (HA) coating. For TPS-coated discs, wrought Ti6Al4V ELI was machined and TPS-coating was applied. For AM discs, Ti6Al4V ELI powder was 3D-printed to form a solid base and trabecular-like porous surface. The HA-coating was applied via a precipitation dip-spin method. Surface porosity, pore size, thickness, and hydrophilicity were characterized. Initial cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium production of hFOB cells ( n =5 per group) were measured. Cells on AM discs exhibited expedited proliferative activity. While there were no differences in mean ALP expression and calcium production between TPS and AM discs, calcium production on the AM discs trended 48% higher than on TPS discs ( p =0.07). Overall, HA-coating did not further enhance results compared to uncoated TPS and AM discs. Results demonstrate that additive manufacturing allows for controlled trabecular-like surfaces that promote earlier cell proliferation and trends toward higher calcium production than TPS coating. Results further showed that nanocrystalline HA may not provide an advantage on porous titanium surfaces. Additive manufactured porous titanium surfaces may induce a more osteogenic environment compared to traditional TPS, and thus present as an attractive alternative to TPS-coating for orthopedic spinal implants.

Postero-Lateral Disc Prosthesis Combined With a Unilateral Facet Replacement Device Maintains Quantity and Quality of Motion at a Single Lumbar Level

PubMed Central

Nayak, Aniruddh N.; Doarn, Michael C.; Gaskins, Roger B.; James, Chris R.; Cabezas, Andres F.; Castellvi, Antonio E.

2014-01-01

Background Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent. Purpose The purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels. Study Design In-vitro study using human cadaveric lumbar spines. Methods Six (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions. Results Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc space Conclusion Biomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level. PMID:25694929

The predisposing factors for the heterotopic ossification after cervical artificial disc replacement.

PubMed

Yi, Seong; Shin, Dong Ah; Kim, Keung Nyun; Choi, Gwihyun; Shin, Hyun Chul; Kim, Keun Su; Yoon, Do Heum

2013-09-01

Heterotopic ossification (HO) is defined as a formation of bone outside the skeletal system. The reported HO occurrence rate in cervical artificial disc replacement (ADR) is unexpectedly high and is known to vary. However, the predisposing factors for HO in cervical ADR have not yet been elucidated. Investigation of the predisposing factors of HO in cervical arthroplasty and the relationship between degeneration of the cervical spine and HO occurrence. Retrospective study to discover predisposing factors of HO in cervical arthroplasty. A total of 170 patients who underwent cervical ADR were enrolled including full follow-up clinical and radiologic data. Radiologic outcomes were assessed by identification of HOs according to McAfee's classifications. This study enrolled a total of 170 patients who underwent cervical ADR. Pre-existing degenerative change included anterior or posterior osteophytes, ossification of the anterior longitudinal ligament, posterior longitudinal ligament, or ligamentum nuchae. The relationships between basic patient data, pre-existing degenerative change, and HO were investigated using linear logistic regression analysis. Among all 170 patients, HO was found in 69 patients (40.6%). Among the postulated predisposing factors, only male gender and artificial disc device type were shown to be statistically significant. Unexpectedly, preoperative degenerative changes in the cervical spine exerted no significant influence on the occurrence of HOs. The odds ratio of male gender compared with female gender was 2.117. With regard to device type, the odds ratios of Mobi-C (LDR medical, Troyes, France) and ProDisc-C (Synthes, Inc., West Chester, PA, USA) were 5.262 and 7.449, respectively, compared with the Bryan disc. Definite differences in occurrence rate according to the gender of patients and the prosthesis type were identified in this study. Moreover, factors indefinably expected to influence HO in the past were not shown to be risk factors thereof, the results of which may be meaningful to future studies. Copyright © 2013 Elsevier Inc. All rights reserved.

The First Wave: CD-ROM Adoption in Offices and Libraries: I.

ERIC Educational Resources Information Center

Paisley, William; Butler, Matilda

1988-01-01

The first of two articles provides an overview of four revolutions in publishing--the movable-type printing press, mechanization, the computer, and optical disc technology. The first phases of CD-ROM development--demonstration of feasibility and testing of replacement functions--are described and compared with earlier technologies. (3 references)…

Neurological complications of lumbar artificial disc replacement and comparison of clinical results with those related to lumbar arthrodesis in the literature: results of a multicenter, prospective, randomized investigational device exemption study of Charité intervertebral disc. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004.

PubMed

Geisler, Fred H; Blumenthal, Scott L; Guyer, Richard D; McAfee, Paul C; Regan, John J; Johnson, J Patrick; Mullin, Bradford

2004-09-01

Arthrodesis is the gold standard for surgical treatment of lumbar degenerative disc disease (DDD). Solid fusion, however, can cause stress and increased motion in the segments adjacent to the fused level. This may initiate and/or accelerate the adjacent-segment disease process. Artificial discs are designed to restore and maintain normal motion of the lumbar intervertebral segment. Restoring and maintaining normal motion of the segment reduces stresses and loads on adjacent level segments. A US Food and Drug Administration Investigational Device Exemptions multicentered study of the Charité artificial disc was completed. The control group consisted of individuals who underwent anterior lumbar interbody fusion involving BAK cages and iliac crest bone graft. This is the first report of Class I data in which a lumbar artificial disc is compared with lumbar fusion. Of 304 individuals enrolled in the study, 205 were randomized to the Charité disc-treated group and 99 to the BAK fusion-treated (control) group. Neurological status was equivalent between the two groups at 6, 12, and 24 months postoperatively. The number of patients with major, minor, or other neurological complications was equivalent. There was a greater incidence of both major and minor complications in the BAK fusion group at 0 to 42 days postoperatively. Compared with data reported in the lumbar fusion literature, the Charité disc-treated patients had equivalent or better mean changes in visual analog scale and Oswestry Disability Index scores. The Charité artificial disc is safe and effective for the treatment of single-level lumbar DDD, resulting in no higher incidence of neurological complications compared with BAK-assisted fusion and leading to equivalent or better outcomes compared with those obtained in the control group and those reported in the lumbar fusion literature.

Successful treatment of a patient after sudden loss of the disc in a Björk-Shiley convexo-concave mitral prosthesis.

PubMed

Scalia, D; Giacomin, A; Da Col, U; Valfre, C

1987-10-01

The patient's survival after minor strut fracture and migration of a Björk-Shiley mitral prosthetic disc is presented. The operation was carried out in two stages: first emergency replacement of the mitral prosthesis and, later, elective removal of the dislocated disc.

Replacing Shox2 with human SHOX leads to congenital disc degeneration of the temporomandibular joint in mice

PubMed Central

Li, Xihai; Liu, Hongbing; Gu, Shuping; Liu, Chao; Sun, Cheng; Zheng, Yuqian; Chen, YiPing

2013-01-01

The temporomandibular joint (TMJ) consists of the glenoid fossa arising from the otic capsule through intramembranous ossification, the fibrocartilaginous disc and the condyle, derived from the secondary cartilage by endochondral ossification. We have reported previously that cranial neural crest-specific inactivation of the homeobox gene Shox2, which is expressed in the mesenchymal cells of maxilla-mandibular junction and later in the progenitor cells and perichondrium of the developing chondyle, led to dysplasia and ankylosis of the TMJ, and replacement of the mouse Shox2 with the human SHOX gene rescued the dysplastic and ankylosis phenotypes but developed a prematurely worn out articular disc. In this study, we investigated the molecular and cellular bases for the premature wear out articular disc in the TMJ of mice carrying the human SHOX replacement allele in the Shox2 locus (referred as Shox2SHOX-KI/KI). We found that the developmental process and expression of several key genes in the TMJ of Shox2SHOX-KI/KI mice appeared similar to the controls. However, the disc of the Shox2SHOX-KI/KI TMJ exhibited a reduced level of Col I and Aggrecan, accompanied by increased activities of matrix metalloproteinases (MMPs) and a down-regulation of Ihh expression. Dramatically increased cell apoptosis in the disc was also observed. These combinatory cellular and molecular defects appear to contribute to the observed disc phenotype, suggesting that while the human SHOX can exert similar function as the mouse Shox2 in regulating early TMJ development, it apparently has a distinct function in the regulation of those molecules that are involved in tissue homeostasis. PMID:24248941

Biological intervertebral disc replacement: an in vivo model and comparison of two surgical techniques to approach the rat caudal disc

PubMed Central

Gebhard, Harry; James, Andrew R.; Bowles, Robby D.; Dyke, Jonathan P.; Saleh, Tatianna; Doty, Stephen P.; Bonassar, Lawrence J.; Härtl, Roger

2011-01-01

Study design: Prospective randomized animal study. Objective: To determine a surgical technique for reproducible and functional intervertebral disc replacement in an orthotopic animal model. Methods: The caudal 3/4 intervertebral disc (IVD) of the rat tail was approached by two surgical techniques: blunt dissection, stripping and retracting (Technique 1) or incising and repairing (Technique 2) the dorsal longitudinal tendons. The intervertebral disc was dissected and removed, and then either discarded or reinserted. Outcome measures were perioperative complications, spontaneous tail movement, 7T MRI (T1- and T2-sequences for measurement of disc space height (DSH) and disc hydration). Microcomputed tomographic imaging (micro CT) was additionally performed postmortem. Results: No vascular injuries occurred and no systemic or local infections were observed over the course of 1 month. Tail movements were maintained. With tendon retraction (Technique 1) gross loss of DSH occurred with both discectomy and reinsertion. Tendon division (Technique 2) maintained DSH with IVD reinsertion but not without. The DSH was demonstrated on MRI measurement. A new scoring system to assess IVD appearances was described. Conclusions: The rat tail model, with a tendon dividing surgical technique, can function as an orthotopic animal model for IVD research. Mechanical stimulation is maintained by preserved tail movements. 7T MRI is a feasible modality for longitudinal monitoring for the rat caudal disc. PMID:22956934

A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering

PubMed Central

Choy, Andrew Tsz Hang; Chan, Barbara Pui

2015-01-01

Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering. PMID:26115332

Complications of Lumbar Artificial Disc Replacement Compared to Fusion: Results From the Prospective, Randomized, Multicenter US Food and Drug Administration Investigational Device Exemption Study of the Charité Artificial Disc

PubMed Central

Majd, Mohammed E.; Isaza, Jorge E.; Blumenthal, Scott L.; McAfee, Paul C.; Guyer, Richard D.; Hochschuler, Stephen H.; Geisler, Fred H.; Garcia, Rolando; Regan, John J.

2007-01-01

Background Previous reports of lumbar total disc replacement (TDR) have described significant complications. The US Food and Drug Administration (FDA) investigational device exemption (IDE) study of the Charité artificial disc represents the first level I data comparison of TDR to fusion. Methods In the prospective, randomized, multicenter IDE study, patients were randomized in a 2:1 ratio, with 205 patients in the Charité group and 99 patients in the control group (anterior lumbar interbody fusion [ALIF] with BAK cages). Inclusion criteria included confirmed single-level degenerative disc disease at L4-5 or L5-S1 and failure of nonoperative treatment for at least 6 months. Complications were reported throughout the study. Results The rate of approach-related complications was 9.8% in the investigational group and 10.1% in the control group. The rate of major neurological complications was similar between the 2 groups (investigational = 4.4%, control = 4.0%). There was a higher rate of superficial wound infection in the investigational group but no deep wound infections in either group. Pseudarthrosis occurred in 9.1% of control group patients. The rate of subsidence in the investigational group was 3.4%. The reoperation rate was 5.4% in the investigational group and 9.1% in the control group. Conclusions The incidence of perioperative and postoperative complications for lumbar TDR was similar to that of ALIF. Vigilance is necessary with respect to patient indications, training, and correct surgical technique to maintain TDR complications at the levels experienced in the IDE study. PMID:25802575

Disc replacement adjacent to cervical fusion: a biomechanical comparison of hybrid construct versus two-level fusion.

PubMed

Lee, Michael J; Dumonski, Mark; Phillips, Frank M; Voronov, Leonard I; Renner, Susan M; Carandang, Gerard; Havey, Robert M; Patwardhan, Avinash G

2011-11-01

A cadaveric biomechanical study. To investigate the biomechanical behavior of the cervical spine after cervical total disc replacement (TDR) adjacent to a fusion as compared to a two-level fusion. There are concerns regarding the biomechanical effects of cervical fusion on the mobile motion segments. Although previous biomechanical studies have demonstrated that cervical disc replacement normalizes adjacent segment motion, there is a little information regarding the function of a cervical disc replacement adjacent to an anterior cervical decompression and fusion, a potentially common clinical application. Nine cadaveric cervical spines (C3-T1, age: 60.2 ± 3.5 years) were tested under load- and displacement-control testing. After intact testing, a simulated fusion was performed at C4-C5, followed by C6-C7. The simulated fusion was then reversed, and the response of TDR at C5-C6 was measured. A hybrid construct was then tested with the TDR either below or above a single-level fusion and contrasted with a simulated two-level fusion (C4-C6 and C5-C7). The external fixator device used to simulate fusion significantly reduced range of motion (ROM) at C4-C5 and C6-C7 by 74.7 ± 8.1% and 78.1 ± 11.5%, respectively (P < 0.05). Removal of the fusion construct restored the motion response of the spinal segments to their intact state. Arthroplasty performed at C5-C6 using the porous-coated motion disc prosthesis maintained the total flexion-extension ROM to the level of the intact controls when used as a stand-alone procedure or when implanted adjacent to a single-level fusion (P > 0.05). The location of the single-level fusion, whether above or below the arthroplasty, did not significantly affect the motion response of the arthroplasty in the hybrid construct. Performing a two-level fusion significantly increased the motion demands on the nonoperated segments as compared to a hybrid TDR-plus fusion construct when the spine was required to reach the same motion end points. The spine with a hybrid construct required significantly less extension moment than the spine with a two-level fusion to reach the same extension end point. The porous-coated motion cervical prosthesis restored the ROM of the treated level to the intact state. When the porous-coated motion prosthesis was used in a hybrid construct, the TDR response was not adversely affected. A hybrid construct seems to offer significant biomechanical advantages over two-level fusion in terms of reducing compensatory adjacent-level hypermobility and also loads required to achieve a predetermined ROM.

Mixed reality simulation of rasping procedure in artificial cervical disc replacement (ACDR) surgery.

PubMed

Halic, Tansel; Kockara, Sinan; Bayrak, Coskun; Rowe, Richard

2010-10-07

Until quite recently spinal disorder problems in the U.S. have been operated by fusing cervical vertebrae instead of replacement of the cervical disc with an artificial disc. Cervical disc replacement is a recently approved procedure in the U.S. It is one of the most challenging surgical procedures in the medical field due to the deficiencies in available diagnostic tools and insufficient number of surgical practices For physicians and surgical instrument developers, it is critical to understand how to successfully deploy the new artificial disc replacement systems. Without proper understanding and practice of the deployment procedure, it is possible to injure the vertebral body. Mixed reality (MR) and virtual reality (VR) surgical simulators are becoming an indispensable part of physicians' training, since they offer a risk free training environment. In this study, MR simulation framework and intricacies involved in the development of a MR simulator for the rasping procedure in artificial cervical disc replacement (ACDR) surgery are investigated. The major components that make up the MR surgical simulator with motion tracking system are addressed. A mixed reality surgical simulator that targets rasping procedure in the artificial cervical disc replacement surgery with a VICON motion tracking system was developed. There were several challenges in the development of MR surgical simulator. First, the assembly of different hardware components for surgical simulation development that involves knowledge and application of interdisciplinary fields such as signal processing, computer vision and graphics, along with the design and placements of sensors etc . Second challenge was the creation of a physically correct model of the rasping procedure in order to attain critical forces. This challenge was handled with finite element modeling. The third challenge was minimization of error in mapping movements of an actor in real model to a virtual model in a process called registration. This issue was overcome by a two-way (virtual object to real domain and real domain to virtual object) semi-automatic registration method. The applicability of the VICON MR setting for the ACDR surgical simulator is demonstrated. The main stream problems encountered in MR surgical simulator development are addressed. First, an effective environment for MR surgical development is constructed. Second, the strain and the stress intensities and critical forces are simulated under the various rasp instrument loadings with impacts that are applied on intervertebral surfaces of the anterior vertebrae throughout the rasping procedure. Third, two approaches are introduced to solve the registration problem in MR setting. Results show that our system creates an effective environment for surgical simulation development and solves tedious and time-consuming registration problems caused by misalignments. Further, the MR ACDR surgery simulator was tested by 5 different physicians who found that the MR simulator is effective enough to teach the anatomical details of cervical discs and to grasp the basics of the ACDR surgery and rasping procedure.

Mixed reality simulation of rasping procedure in artificial cervical disc replacement (ACDR) surgery

PubMed Central

2010-01-01

Background Until quite recently spinal disorder problems in the U.S. have been operated by fusing cervical vertebrae instead of replacement of the cervical disc with an artificial disc. Cervical disc replacement is a recently approved procedure in the U.S. It is one of the most challenging surgical procedures in the medical field due to the deficiencies in available diagnostic tools and insufficient number of surgical practices For physicians and surgical instrument developers, it is critical to understand how to successfully deploy the new artificial disc replacement systems. Without proper understanding and practice of the deployment procedure, it is possible to injure the vertebral body. Mixed reality (MR) and virtual reality (VR) surgical simulators are becoming an indispensable part of physicians’ training, since they offer a risk free training environment. In this study, MR simulation framework and intricacies involved in the development of a MR simulator for the rasping procedure in artificial cervical disc replacement (ACDR) surgery are investigated. The major components that make up the MR surgical simulator with motion tracking system are addressed. Findings A mixed reality surgical simulator that targets rasping procedure in the artificial cervical disc replacement surgery with a VICON motion tracking system was developed. There were several challenges in the development of MR surgical simulator. First, the assembly of different hardware components for surgical simulation development that involves knowledge and application of interdisciplinary fields such as signal processing, computer vision and graphics, along with the design and placements of sensors etc . Second challenge was the creation of a physically correct model of the rasping procedure in order to attain critical forces. This challenge was handled with finite element modeling. The third challenge was minimization of error in mapping movements of an actor in real model to a virtual model in a process called registration. This issue was overcome by a two-way (virtual object to real domain and real domain to virtual object) semi-automatic registration method. Conclusions The applicability of the VICON MR setting for the ACDR surgical simulator is demonstrated. The main stream problems encountered in MR surgical simulator development are addressed. First, an effective environment for MR surgical development is constructed. Second, the strain and the stress intensities and critical forces are simulated under the various rasp instrument loadings with impacts that are applied on intervertebral surfaces of the anterior vertebrae throughout the rasping procedure. Third, two approaches are introduced to solve the registration problem in MR setting. Results show that our system creates an effective environment for surgical simulation development and solves tedious and time-consuming registration problems caused by misalignments. Further, the MR ACDR surgery simulator was tested by 5 different physicians who found that the MR simulator is effective enough to teach the anatomical details of cervical discs and to grasp the basics of the ACDR surgery and rasping procedure PMID:20946594

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces

PubMed Central

Lindsey, Derek P.; Bahney, Chelsea S.; Woods, Shane A.; Wolfe, Mark L.; Yerby, Scott A.

2017-01-01

Background An aging society and concomitant rise in the incidence of impaired bone health have led to the need for advanced osteoconductive spinal implant surfaces that promote greater biological fixation (e.g. for interbody fusion cages, sacroiliac joint fusion implants, and artificial disc replacements). Additive manufacturing, i.e. 3D-printing, may improve bone integration by generating biomimetic spinal implant surfaces that mimic bone morphology. Such surfaces may foster an enhanced cellular response compared to traditional implant surfacing processes. Methods This study investigated the response of human osteoblasts to additive manufactured (AM) trabecular-like titanium implant surfaces compared to traditionally machined base material with titanium plasma spray (TPS) coated surfaces, with and without a nanocrystalline hydroxyapatite (HA) coating. For TPS-coated discs, wrought Ti6Al4V ELI was machined and TPS-coating was applied. For AM discs, Ti6Al4V ELI powder was 3D-printed to form a solid base and trabecular-like porous surface. The HA-coating was applied via a precipitation dip-spin method. Surface porosity, pore size, thickness, and hydrophilicity were characterized. Initial cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium production of hFOB cells (n=5 per group) were measured. Results Cells on AM discs exhibited expedited proliferative activity. While there were no differences in mean ALP expression and calcium production between TPS and AM discs, calcium production on the AM discs trended 48% higher than on TPS discs (p=0.07). Overall, HA-coating did not further enhance results compared to uncoated TPS and AM discs. Conclusions Results demonstrate that additive manufacturing allows for controlled trabecular-like surfaces that promote earlier cell proliferation and trends toward higher calcium production than TPS coating. Results further showed that nanocrystalline HA may not provide an advantage on porous titanium surfaces. Clinical Relevance Additive manufactured porous titanium surfaces may induce a more osteogenic environment compared to traditional TPS, and thus present as an attractive alternative to TPS-coating for orthopedic spinal implants. PMID:28765799

Heart valve replacement with the Sorin tilting-disc prosthesis. A 10-year experience.

PubMed

Milano, A; Bortolotti, U; Mazzucco, A; Mossuto, E; Testolin, L; Thiene, G; Gallucci, V

1992-02-01

From 1978 to 1988, 697 patients with a mean age of 48 +/- 11 years (range 5 to 75 years) received a Sorin tilting-disc prosthesis; 358 had had aortic valve replacement, 247 mitral valve replacement, and 92 mitral and aortic valve replacement. Operative mortality rates were 7.8%, 11.3%, and 10.8%, respectively, in the three groups. Cumulative duration of follow-up is 1650 patient-years for aortic valve replacement (maximum follow-up 11.4 years), 963 patient-years for mitral valve replacement (maximum follow-up 9.9 years) and 328 patient-years for mitral and aortic valve replacement (maximum follow-up 9.4 years). Actuarial survival at 9 years is 72% +/- 4% after mitral valve replacement, 70% +/- 3% after aortic valve replacement, and 50% +/- 12% after mitral and aortic valve replacement, and actuarial freedom from valve-related deaths is 97% +/- 2% after mitral valve replacement, 92% +/- 2% after aortic valve replacement, and 62% +/- 15% after mitral and aortic valve replacement. Thromboembolic events occurred in 21 patients with aortic valve replacement (1.3% +/- 0.2%/pt-yr), in 12 with mitral valve replacement (1.2% +/- 0.3% pt-yr), and in seven with mitral and aortic valve replacement (2.1% +/- 0.8%), with one case of prosthetic thrombosis in each group; actuarial freedom from thromboembolism at 9 years is 92% +/- 3% after mitral valve replacement, 91% +/- 3% after aortic valve replacement, and 74% +/- 16% after mitral and aortic valve replacement. Anticoagulant-related hemorrhage was observed in 15 patients after aortic valve replacement (0.9% +/- 0.2%/pt-yr), in 9 after mitral valve replacement (0.9% +/- 0.3%/pt-yr), and in 6 with mitral and aortic valve replacement (0.9% +/- 0.5%/pt-yr); actuarial freedom from this complication at 9 years is 94% +/- 2% after aortic valve replacement, 91% +/- 4% after mitral valve replacement, and 68% +/- 16% after mitral and aortic valve replacement. Actuarial freedom from reoperation at 9 years is 97% +/- 2% after mitral and aortic valve replacement, 92% +/- 4% after mitral valve replacement, and 89% +/- 3% after aortic valve replacement, with no cases of mechanical fracture. The Sorin valve has shown a satisfactory long-term overall performance, comparable with other mechanical prostheses, and an excellent durability that renders it a reliable heart valve substitute for the mitral and aortic positions.

[Displacement and tissue remodeling of temporomandibular joint disc].

PubMed

Wang, M Q

2017-03-09

Sounding takes the highest prevalence of the signs of temporomandibular disorders (TMD). The well accepted theory of the mechanism for temporomandibular joint (TMJ) sounding is the internal derangement typically characterized by disc displacement. However, according to literature, there are approximately one third of asymptomatic joints in population had disc displacement, and, on the other hand, there are one fourth of TMJ sounding patients had not signs or very limited signs of disc displacement. Replacing the displaced disc to the normal position via methods like surgical operation did not achieve satisfactory long-term outcomes. In this review, we discuss and analyze the possible remodeling of the joint disc displacement diagnosed with imaging based on the anatomy and pathophysiology.

Difference in occurrence of heterotopic ossification according to prosthesis type in the cervical artificial disc replacement.

PubMed

Yi, Seong; Kim, Keung Nyun; Yang, Moon Sul; Yang, Joong Won; Kim, Hoon; Ha, Yoon; Yoon, Do Heum; Shin, Hyun Chul

2010-07-15

Retrospective study of the difference of heterotopic ossification (HO) occurrence according to 3 different types of prosthesis. This study was designed to investigate the difference of HO occurrence according to different type of prosthesis. HO is defined as formation of the bone outside the skeletal system. Reported HO occurrence rate in cervical artificial disc replacement (ADR) was unexpectedly high and varied. But the influencing factors of HO in cervical ADR have not been elucidated well. The prosthesis-related factors for making difference of HO occurrence were investigated in this study. A total of 170 patients undergoing cervical arthroplasty with the Bryan cervical disc prosthesis (Medtroic Sofamor Danek, Memphis, TN), Mobi-C disc prosthesis (LDR Medical, Troyes, France), and ProDisc-C (Synthes, Inc., West Chester, PA) were included. Cervical lateral radiographs obtained before and after surgery were used to identify HO. Occurrence rate, occurrence-free period, location, and grade of HOs were investigated according to the different prosthesis. Each prosthesis group included patients as follows: Bryan disc, 81 patients; Mobi-C, 61 patients; and ProDisc-C, 28 patients. Overall HO rate was 40.6% (69 of 170 patients). Each HO occurrence rate by prosthesis was as follows: the Bryan disc group, 21.0%; Mobi-C group, 52.5%; and the ProDisc-C group, 71.4%. In the survival analysis, all patients showed 27.1 +/- 3.7 months as the median survival. The Bryan disc group showed statistically longer survival (48.4 +/- 7.4 months) than the other groups. Occurrence of HO is an inevitable postoperative complication after cervical ADR. The occurrence rate of HO was higher than our expectation. Moreover, definite differences in occurrence rate according to the prosthesis type were identified by this study.

A 6-DOF parallel bone-grinding robot for cervical disc replacement surgery.

PubMed

Tian, Heqiang; Wang, Chenchen; Dang, Xiaoqing; Sun, Lining

2017-12-01

Artificial cervical disc replacement surgery has become an effective and main treatment method for cervical disease, which has become a more common and serious problem for people with sedentary work. To improve cervical disc replacement surgery significantly, a 6-DOF parallel bone-grinding robot is developed for cervical bone-grinding by image navigation and surgical plan. The bone-grinding robot including mechanical design and low level control is designed. The bone-grinding robot navigation is realized by optical positioning with spatial registration coordinate system defined. And a parametric robot bone-grinding plan and high level control have been developed for plane grinding for cervical top endplate and tail endplate grinding by a cylindrical grinding drill and spherical grinding for two articular surfaces of bones by a ball grinding drill. Finally, the surgical flow for a robot-assisted cervical disc replacement surgery procedure is present. The final experiments results verified the key technologies and performance of the robot-assisted surgery system concept excellently, which points out a promising clinical application with higher operability. Finally, study innovations, study limitations, and future works of this present study are discussed, and conclusions of this paper are also summarized further. This bone-grinding robot is still in the initial stage, and there are many problems to be solved from a clinical point of view. Moreover, the technique is promising and can give a good support for surgeons in future clinical work.

Factors affecting the process of CO2 replacement of CH4 from methane hydrate in sediments - Constrained from experimental results

NASA Astrophysics Data System (ADS)

Lu, H.; Hu, G.; Vanderveen, J.; Liu, C.; Ratcliffe, C.; Ripmeester, J.

2011-12-01

CO2 replacement of CH4 from methane hydrate has been proposed as a method to produce gas from natural gas hydrate by taking advantage of both the production of natural gas and the sequestration of CO2. To examine the validity of this method DOE/Conoco-Philips is considering having a field test in Alaska. The reaction of CO2 replacing CH4 from methane hydrate has been confirmed to be thermodynamically feasible, but concern is always raised about the reaction kinetics. Some kinetic studies in the system of methane hydrate and liquid or gaseous CO2 have found that the reaction proceeds at a very low rate. Natural gas hydrate occurs in sediments with multi-components and complex structure, so matters will be even more complicated. Up to now, few investigations have been carried out concerning the factors affecting the reaction process of CO2 replacing CH4 from methane hydrate. Experiments were implemented with sands, which were recovered from Mallik 5L-38 well, Mackenzie Delta, Northwest Territory, Canada, sediment that previously contained hydrate although it had been dried completely before our experiments. The water-saturated sands were tightly charged into a plastic bottle (90 mm deep and 60 mm wide), and then this test specimen was sealed in a pressure cell. After methane hydrate was synthesized in the test specimen for 108 days under a pressure of 11 to 8 MPa and a temperature of 3 degrees Celsius, liquid CO2 was introduced into the pressure cell. The conditions under which CO2 was reacted with methane hydrate were ~5.3 MPa and 5 degrees Celsius. After reacting for 15 days, the test specimen was recovered. The test specimen was cut into ~10 mm thick discs, and sub-samples were further taken from each of the discs. In addition to the determination of hydrate saturation and the gas composition, Raman spectroscopic studies were carried out for the sub-samples obtained. The results revealed: 1) less CO2 replacement in the bottom disc of the test specimen as compared with that in the top disc, implying that diffusion was a factor that controlled the movement of CO2 in the sediments, 2) an inhomogeneous replacement reaction even within the same disc, indicating that the contact area between methane hydrate and CO2 was a factor that determined the degree of replacement of CH4 from methane hydrate 3) the separate appearance of CO2 Raman intensities and CH4 Raman intensities in some portions of the test specimen, suggesting that CO2 was present in the form of CO2 hydrate in addition to being together with CH4 in other parts of the hydrate. Further analysis found that both CO2 diffusion and the contact area for reaction were associated with the pore structure of the sediments, which were heterogeneous both in pore size and in pore shape as observed with high resolution X-ray CT.

Biomechanical Effects of the Geometry of Ball-and-Socket Artificial Disc on Lumbar Spine: A Finite Element Study.

PubMed

Choi, Jisoo; Shin, Dong-Ah; Kim, Sohee

2017-03-15

A three-dimensional finite element model of intact lumbar spine was constructed and four surgical finite element models implanted with ball-and-socket artificial discs with four different radii of curvature were compared. To investigate biomechanical effects of the curvature of ball-and-socket artificial disc using finite element analysis. Total disc replacement (TDR) has been accepted as an alternative treatment because of its advantages over spinal fusion methods in degenerative disc disease. However, the influence of the curvature of artificial ball-and-socket discs has not been fully understood. Four surgical finite element models with different radii of curvature of ball-and-socket artificial discs were constructed. The range of motion (ROM) increased with decreasing radius of curvature in extension, flexion, and lateral bending, whereas it increased with increasing radius of curvature in axial torsion. The facet contact force was minimum with the largest radius of curvature in extension, flexion, and lateral bending, whereas it was maximum with the largest radius in axial torsion. It was also affected by the disc placement, more with posterior placement than anterior placement. The stress in L4 cancellous bone increased when the radius of curvature was too large or small. The geometry of ball-and-socket artificial disc significantly affects the ROM, facet contact force, and stress in the cancellous bone at the surgical level. The implication is that in performing TDR, the ball-and-socket design may not be ideal, as ROM and facet contact force are sensitive to the disc design, which may be exaggerated by the individual difference of anatomical geometry. N/A.

Cross-Shear Implementation in Sliding-Distance-Coupled Finite Element Analysis of Wear in Metal-on-Polyethylene Total Joint Arthroplasty: Intervertebral Total Disc Replacement as an Illustrative Application

PubMed Central

Goreham-Voss, Curtis M.; Hyde, Philip J.; Hall, Richard M.; Fisher, John; Brown, Thomas D.

2010-01-01

Computational simulations of wear of orthopaedic total joint replacement implants have proven to valuably complement laboratory physical simulators, for pre-clinical estimation of abrasive/adhesive wear propensity. This class of numerical formulations has primarily involved implementation of the Archard/Lancaster relationship, with local wear computed as the product of (finite element) contact stress, sliding speed, and a bearing-couple-dependent wear factor. The present study introduces an augmentation, whereby the influence of interface cross-shearing motion transverse to the prevailing molecular orientation of the polyethylene articular surface is taken into account in assigning the instantaneous local wear factor. The formulation augment is implemented within a widely-utilized commercial finite element software environment (ABAQUS). Using a contemporary metal-on-polyethylene total disc replacement (ProDisc-L) as an illustrative implant, physically validated computational results are presented to document the role of cross-shearing effects in alternative laboratory consensus testing protocols. Going forward, this formulation permits systematically accounting for cross-shear effects in parametric computational wear studies of metal-on-polyethylene joint replacements, heretofore a substantial limitation of such analyses. PMID:20399432

Total disc replacement using a tissue-engineered intervertebral disc in vivo: new animal model and initial results

PubMed Central

Gebhard, Harry; Bowles, Robby; Dyke, Jonathan; Saleh, Tatianna; Doty, Stephen; Bonassar, Lawrence; Härtl, Roger

2010-01-01

Study type: Basic science Introduction: Chronic back pain due to degenerative disc disease (DDD) is among the most important medical conditions causing morbidity and significant health care costs. Surgical treatment options include disc replacement or fusion surgery, but are associated with significant short- and long-term risks.1 Biological tissue-engineering of human intervertebral discs (IVD) could offer an important alternative.2 Recent in vitro data from our group have shown successful engineering and growth of ovine intervertebral disc composites with circumferentially aligned collagen fibrils in the annulus fibrosus (AF) (Figure 1).3 Figure 1 Tissue-engineered composite disc a Experimental steps to generate composite tissue-engineered IVDs3 b Example of different AF formulations on collagen alignment in the AF. Second harmonic generation and two-photon excited fluorescence images of seeded collagen gels (for AF) of 1 and 2.5 mg/ml over time. At seeding, cells and collagen were homogenously distributed in the gels. Over time, AF cells elongated and collagen aligned parallel to cells. Less contraction and less alignment is noted after 3 days in the 2.5 mg/mL gel. c Imaging-based creation of a virtual disc model that will serve as template for the engineered disc. Total disc dimensions (AF and NP) were retrieved from micro-computer tomography (CT) (left images), and nucleus pulposus (NP) dimensions alone were retrieved from T2-weighted MRI images (right images). Merging of MRI and micro-CT models revealed a composite disc model (middle image)—Software: Microview, GE Healthcare Inc., Princeton, NJ; and slicOmatic v4.3, TomoVision, Montreal, Canada. d Flow chart describing the process for generating multi-lamellar tissue engineered IVDs. IVDs are produced by allowing cell-seeded collagen layers to contract around a cell-seeded alginate core (NP) over time Objective: The next step is to investigate if biological disc implants survive, integrate, and restore function to the spine in vivo. A model will be developed that allows efficient in vivo testing of tissue-engineered discs of various compositions and characteristics. Methods: Athymic rats were anesthetized and a dorsal approach was chosen to perform a microsurgical discectomy in the rat caudal spine (Fig. 2,Fig. 3). Control group I (n = 6) underwent discectomy only, Control group II (n = 6) underwent discectomy, followed by reimplantation of the autologous disc. Two treatment groups (group III, n = 6, 1 month survival; group IV, n = 6, 6 months survival) received a tissue-engineered composite disc implant. The rodents were followed clinically for signs of infection, pain level and wound healing. X-rays and magnetic resonance imaging (MRI) were assessed postoperatively and up to 6 months after surgery (Fig. 6,Fig. 7). A 7 Tesla MRI (Bruker) was implemented for assessment of the operated level as well as the adjacent disc (hydration). T2-weighted sequences were interpreted by a semiquantitative score (0 = no signal, 1 = weak signal, 2 = strong signal and anatomical features of a normal disc). Histology was performed with staining for proteoglycans (Alcian blue) and collagen (Picrosirius red) (Fig. 4,Fig. 5). Figure 2 Disc replacement surgery a Operative situs with native disc that has been disassociated from both adjacent vertebrae b Native disc (left) and tissue-engineered implant (right) c Implant in situ before wound closureAF: Annulus fi brosus, nP: nucleus pulposus, eP: endplate, M: Muscle, T: Tendon, s: skin, art: artery, GP: Growth plate, B: Bone Figure 3 Disc replacement surgery. Anatomy of the rat caudal disc space a Pircrosirius red stained axial cut of native disc space b Saffranin-O stained sagittal cut of native disc space Figure 4 Histologies of three separate motion segments from three different rats. Animal one = native IVD, Animal two = status after discectomy, Animal three = tissue-engineered implant (1 month) a–c H&E (overall tissue staining for light micrsocopy) d–f Alcian blue (proteoglycans) g–i Picrosirius red (collagen I and II) Figure 5 Histology from one motion segment four months after implantation of a bio-engineered disc construct a Picrosirius red staining (collagen) b Polarized light microscopy showing collagen staining and collagen organization in AF region c Increased Safranin-O staining (proteoglycans) in NP region of the disc implant d Higher magnification of figure 5c: Integration between implanted tissue-engineered total disc replacement and vertebral body bone Figure 6 MRI a Disc space height measurements in flash/T1 sequence (top: implant (714.0 micrometer), bottom: native disc (823.5 micrometer) b T2 sequence, red circle surrounding the implant NP Figure 7 7 Tesla MRI imaging of rat tail IVDs showing axial images (preliminary pilot data) a Diffusion tensor imaging (DTI) on two explanted rat tail discs in Formalin b Higher magnification of a, showing directional alignment of collagen fibers (red and green) when compared to the color ball on top which maps fibers' directional alignment (eg, fibers directing from left to right: red, from top to bottom: blue) c Native IVD in vivo (successful imaging of top and bottom of the IVD (red) d Gradient echo sequence (GE) showing differentiation between NP (light grey) and AF (dark margin) e GE of reimplanted tail IVD at the explantation level f T1Rho sequence demonstrating the NP (grey) within the AF (dark margin), containing the yellow marked region of interest for value acquisition (preliminary data are consistent with values reported in the literature). g T2 image of native IVD in vivo for monitoring of hydration (white: NP) Results: The model allowed reproducible and complete discectomies as well as disc implantation in the rat tail spine without any surgical or postoperative complications. Discectomy resulted in immediate collapse of the disc space. Preliminary results indicate that disc space height was maintained after disc implantation in groups II, III and IV over time. MRI revealed high resolution images of normal intervertebral discs in vivo. Eight out of twelve animals (groups III and IV) showed a positive signal in T2-weighted images after 1 month (grade 0 = 4, grade 1 = 4, grade 2 = 4). Positive staining was seen for collagen as well as proteoglycans at the site of disc implantation after 1 month in each of the six animals with engineered implants (group III). Analysis of group IV showed positive T2 signal in five out of six animals and disc-height preservation in all animals after 6 months. Conclusions: This study demonstrates for the first time that tissue-engineered composite IVDs with circumferentially aligned collagen fibrils survive and integrate with surrounding vertebral bodies when placed in the rat spine for up to 6 months. Tissue-engineered composite IVDs restored function to the rat spine as indicated by maintenance of disc height and vertebral alignment. A significant finding was that maintenance of the composite structure in group III was observed, with increased proteoglycan staining in the nucleus pulposus region (Figure 4d–f). Proteoglycan and collagen matrix as well as disc height preservation and positive T2 signals in MRI are promising parameters and indicate functionality of the implants. PMID:23637671

Total disc replacement using a tissue-engineered intervertebral disc in vivo: new animal model and initial results.

PubMed

Gebhard, Harry; Bowles, Robby; Dyke, Jonathan; Saleh, Tatianna; Doty, Stephen; Bonassar, Lawrence; Härtl, Roger

2010-08-01

 Basic science Introduction:  Chronic back pain due to degenerative disc disease (DDD) is among the most important medical conditions causing morbidity and significant health care costs. Surgical treatment options include disc replacement or fusion surgery, but are associated with significant short- and long-term risks.1 Biological tissue-engineering of human intervertebral discs (IVD) could offer an important alternative.2 Recent in vitro data from our group have shown successful engineering and growth of ovine intervertebral disc composites with circumferentially aligned collagen fibrils in the annulus fibrosus (AF) (Figure 1).3 Figure 1 Tissue-engineered composite disc a Experimental steps to generate composite tissue-engineered IVDs3b Example of different AF formulations on collagen alignment in the AF. Second harmonic generation and two-photon excited fluorescence images of seeded collagen gels (for AF) of 1 and 2.5 mg/ml over time. At seeding, cells and collagen were homogenously distributed in the gels. Over time, AF cells elongated and collagen aligned parallel to cells. Less contraction and less alignment is noted after 3 days in the 2.5 mg/mL gel. c Imaging-based creation of a virtual disc model that will serve as template for the engineered disc. Total disc dimensions (AF and NP) were retrieved from micro-computer tomography (CT) (left images), and nucleus pulposus (NP) dimensions alone were retrieved from T2-weighted MRI images (right images). Merging of MRI and micro-CT models revealed a composite disc model (middle image)-Software: Microview, GE Healthcare Inc., Princeton, NJ; and slicOmatic v4.3, TomoVision, Montreal, Canada. d Flow chart describing the process for generating multi-lamellar tissue engineered IVDs. IVDs are produced by allowing cell-seeded collagen layers to contract around a cell-seeded alginate core (NP) over time Objective:  The next step is to investigate if biological disc implants survive, integrate, and restore function to the spine in vivo. A model will be developed that allows efficient in vivo testing of tissue-engineered discs of various compositions and characteristics.  Athymic rats were anesthetized and a dorsal approach was chosen to perform a microsurgical discectomy in the rat caudal spine (Fig. 2,Fig. 3). Control group I (n = 6) underwent discectomy only, Control group II (n = 6) underwent discectomy, followed by reimplantation of the autologous disc. Two treatment groups (group III, n = 6, 1 month survival; group IV, n = 6, 6 months survival) received a tissue-engineered composite disc implant. The rodents were followed clinically for signs of infection, pain level and wound healing. X-rays and magnetic resonance imaging (MRI) were assessed postoperatively and up to 6 months after surgery (Fig. 6,Fig. 7). A 7 Tesla MRI (Bruker) was implemented for assessment of the operated level as well as the adjacent disc (hydration). T2-weighted sequences were interpreted by a semiquantitative score (0 = no signal, 1 = weak signal, 2 = strong signal and anatomical features of a normal disc). Histology was performed with staining for proteoglycans (Alcian blue) and collagen (Picrosirius red) (Fig. 4,Fig. 5). Figure 2 Disc replacement surgery a Operative situs with native disc that has been disassociated from both adjacent vertebrae b Native disc (left) and tissue-engineered implant (right) c Implant in situ before wound closureAF: Annulus fi brosus, nP: nucleus pulposus, eP: endplate, M: Muscle, T: Tendon, s: skin, art: artery, GP: Growth plate, B: BoneFigure 3 Disc replacement surgery. Anatomy of the rat caudal disc space a Pircrosirius red stained axial cut of native disc space b Saffranin-O stained sagittal cut of native disc spaceFigure 4 Histologies of three separate motion segments from three different rats. Animal one = native IVD, Animal two = status after discectomy, Animal three = tissue-engineered implant (1 month) a-c H&E (overall tissue staining for light micrsocopy) d-f Alcian blue (proteoglycans) g-i Picrosirius red (collagen I and II)Figure 5 Histology from one motion segment four months after implantation of a bio-engineered disc construct a Picrosirius red staining (collagen) b Polarized light microscopy showing collagen staining and collagen organization in AF region c Increased Safranin-O staining (proteoglycans) in NP region of the disc implant d Higher magnification of figure 5c: Integration between implanted tissue-engineered total disc replacement and vertebral body boneFigure 6 MRI a Disc space height measurements in flash/T1 sequence (top: implant (714.0 micrometer), bottom: native disc (823.5 micrometer) b T2 sequence, red circle surrounding the implant NPFigure 7 7 Tesla MRI imaging of rat tail IVDs showing axial images (preliminary pilot data) a Diffusion tensor imaging (DTI) on two explanted rat tail discs in Formalin b Higher magnification of a, showing directional alignment of collagen fibers (red and green) when compared to the color ball on top which maps fibers' directional alignment (eg, fibers directing from left to right: red, from top to bottom: blue) c Native IVD in vivo (successful imaging of top and bottom of the IVD (red) d Gradient echo sequence (GE) showing differentiation between NP (light grey) and AF (dark margin) e GE of reimplanted tail IVD at the explantation level f T1Rho sequence demonstrating the NP (grey) within the AF (dark margin), containing the yellow marked region of interest for value acquisition (preliminary data are consistent with values reported in the literature). g T2 image of native IVD in vivo for monitoring of hydration (white: NP) Results:  The model allowed reproducible and complete discectomies as well as disc implantation in the rat tail spine without any surgical or postoperative complications. Discectomy resulted in immediate collapse of the disc space. Preliminary results indicate that disc space height was maintained after disc implantation in groups II, III and IV over time. MRI revealed high resolution images of normal intervertebral discs in vivo. Eight out of twelve animals (groups III and IV) showed a positive signal in T2-weighted images after 1 month (grade 0 = 4, grade 1 = 4, grade 2 = 4). Positive staining was seen for collagen as well as proteoglycans at the site of disc implantation after 1 month in each of the six animals with engineered implants (group III). Analysis of group IV showed positive T2 signal in five out of six animals and disc-height preservation in all animals after 6 months.  This study demonstrates for the first time that tissue-engineered composite IVDs with circumferentially aligned collagen fibrils survive and integrate with surrounding vertebral bodies when placed in the rat spine for up to 6 months. Tissue-engineered composite IVDs restored function to the rat spine as indicated by maintenance of disc height and vertebral alignment. A significant finding was that maintenance of the composite structure in group III was observed, with increased proteoglycan staining in the nucleus pulposus region (Figure 4d-f). Proteoglycan and collagen matrix as well as disc height preservation and positive T2 signals in MRI are promising parameters and indicate functionality of the implants.

Design limitations of Bryan disc arthroplasty.

PubMed

Fong, Shee Yan; DuPlessis, Stephan J; Casha, Steven; Hurlbert, R John

2006-01-01

Disc arthroplasty is gaining momentum as a surgical procedure in the treatment of spinal degenerative disease. Results must be carefully scrutinized to recognize benefits as well as limitations. The aim of this study was to investigate factors associated with segmental kyphosis after Bryan disc replacement. Prospective study of a consecutively enrolled cohort of 10 patients treated in a single center using the Bryan cervical disc prosthesis for single-level segmental reconstruction in the surgical treatment of cervical radiculopathy and/or myelopathy. Radiographic and quality of life outcome measures. Static and dynamic lateral radiographs were digitally analyzed in patients undergoing Bryan disc arthroplasty throughout a minimum 3-month follow-up period. Observations were compared with preoperative studies looking for predictive factors of postoperative spinal alignment. Postoperative end plate angles through the Bryan disc in the neutral position were kyphotic in 9 of 10 patients. Compared with preoperative end plate angulation there was a mean change of -7 degrees (towards kyphosis) in postoperative end plate alignment (p=.007, 95% confidence interval [CI] -6 degrees to -13 degrees). This correlated significantly with postoperative reduction in posterior vertebral body height of the caudal segment (p=.011, r2=.575) and postoperative functional spine unit (FSU) kyphosis (p=.032, r2=.46). Despite intraoperative distraction, postoperative FSU height was significantly reduced, on average by 1.7 mm (p=.040, 95% CI 0.5-2.8 mm). Asymmetrical end plate preparation occurs because of suboptimal coordinates to which the milling jig is referenced. Although segmental motion is preserved, Bryan disc arthroplasty demonstrates a propensity towards kyphotic orientation through the prosthesis likely as a result of intraoperative lordotic distraction. FSU angulation tends towards kyphosis and FSU height is decreased in the postoperative state from lack of anterior column support. Limitations of Bryan cervical disc arthroplasty should be carefully considered when reconstruction or maintenance of cervical lordosis is desirable.

Determination of the intervertebral disc space from CT images of the lumbar spine

NASA Astrophysics Data System (ADS)

Korez, Robert; Å tern, Darko; Likar, Boštjan; Pernuš, Franjo; Vrtovec, Tomaž

2014-03-01

Degenerative changes of the intervertebral disc are among the most common causes of low back pain, where for individuals with significant symptoms surgery may be needed. One of the interventions is the total disc replacement surgery, where the degenerated disc is replaced by an artificial implant. For designing implants with good bone contact and continuous force distribution, the morphology of the intervertebral disc space and vertebral body endplates is of considerable importance. In this study we propose a method for the determination of the intervertebral disc space from three-dimensional (3D) computed tomography (CT) images of the lumbar spine. The first step of the proposed method is the construction of a model of vertebral bodies in the lumbar spine. For this purpose, a chain of five elliptical cylinders is initialized in the 3D image and then deformed to resemble vertebral bodies by introducing 25 shape parameters. The parameters are obtained by aligning the chain to the vertebral bodies in the CT image according to image intensity and appearance information. The determination of the intervertebral disc space is finally achieved by finding the planes that fit the endplates of the obtained parametric 3D models, and placing points in the space between the planes of adjacent vertebrae that enable surface reconstruction of the intervertebral disc space. The morphometric analysis of images from 20 subjects yielded 11:3 +/- 2:6, 12:1 +/- 2:4, 12:8 +/- 2:0 and 12:9 +/- 2:7 cm3 in terms of L1-L2, L2-L3, L3-L4 and L4-L5 intervertebral disc space volume, respectively.

ALIF and total disc replacement versus 2-level circumferential fusion with TLIF: a prospective, randomized, clinical and radiological trial.

PubMed

Hoff, Eike K; Strube, Patrick; Pumberger, Matthias; Zahn, Robert K; Putzier, Michael

2016-05-01

Prospective, randomized trial. The treatment of degenerative disc disease (DDD) with two-level fusion has been associated with a reasonable rate of complications. The aim of the present study was to compare (Hybrid) stand-alone anterior lumbar interbody fusion (ALIF) at L5/S1 with total disc replacement at L4/5 (TDR) as an alternative surgical strategy to (Fusion) 2-level circumferential fusion employing transforaminal lumbar interbody fusion (TLIF) with transpedicular stabilization at L4-S1. A total of 62 patients with symptomatic DDD of segments L5/S1 (Modic ≥2°) and L4/5 (Modic ≤2°; positive discography) were enrolled; 31 were treated with Hybrid and 31 with Fusion. Preoperatively, at 0, 12, and a mean follow-up of 37 months, clinical (ODI, VAS) and radiological evaluations (plain/extension-flexion radiographs evaluated for implant failure, fusion, global and segmental lordosis, and ROM) were performed. In 26 of 31 Hybrid and 24 of 31 Fusion patients available at the final follow-up, we found a significant clinical improvement compared to preoperatively. Hybrid patients had significantly lower VAS scores immediately postoperatively and at follow-up compared to Fusion patients. The complication rates were low and similar between the groups. Lumbar lordosis increased in both groups. The increase was mainly located at L4-S1 in the Hybrid group and at L1-L4 in the Fusion group. Hybrid patients presented with increased ROM at L4/5 and L3/4, and Fusion patients presented with increased ROM at L3/4, with significantly greater ROM at L3/4 compared to Hybrid patients at follow-up. Hybrid surgery is a viable surgical alternative for the presented indication. Approach-related inferior trauma and the balanced restoration of lumbar lordosis resulted in superior clinical outcomes compared to two-level circumferential fusion with TLIF.

Symptomatic adjacent segment disease after cervical total disc replacement: re-examining the clinical and radiological evidence with established criteria.

PubMed

Nunley, Pierce D; Jawahar, Ajay; Cavanaugh, David A; Gordon, Charles R; Kerr, Eubulus J; Utter, Phillip Andrew

2013-01-01

Although several publications in the last decade have proved equality in safety and efficacy of the total disc replacement (TDR) to the anterior fusion procedure in cervical spine, the claim that TDR may reduce the incidence of adjacent segment disease (ASD) has not been corroborated by clinical evidence. We attempt to predict the true incidence of symptomatic ASD after TDR surgery in the cervical spine at one or two levels at a median follow-up period of 4 years. A total of 763 patients were screened to participate in four different Food and Drug Administration device exemption trials for artificial cervical disc replacement at three collaborating institutions. Two hundred seventy-one patients qualified and enrolled in the trials. One hundred seventy-three randomized to receive artificial disc replacement surgery, and 167 have completed a 4-year or longer follow-up. Patients experiencing cervical radiculopathy symptoms in the follow-up period were worked-up with clinical examinations, magnetic resonance imaging of the cervical spine, and other diagnostic studies. Once a clinical correlation was established with the imaging evidence of adjacent segment degeneration, a careful record was maintained to document the subsequent medical and/or surgical treatment received by these patients. Statistical analysis was performed to determine the true incidence of and factors affecting the ASD after cervical disc replacement in these patients. Twenty-six patients (15.2%) were identified to satisfy our criteria for ASD at the median follow-up of 51 months, with the annual incidence of 3.1% as calculated by life tables. The actuarial 5-year freedom from ASD rate was 71.6%±0.6%, and the mean period for freedom from ASD was 70.4±2.1 months. The incidence of symptomatic ASD after cervical TDR is 3.1% annually regardless of the patient's age, sex, smoking habits, and design of the TDR device. The presence of osteopenia and lumbar degenerative disease significantly increase the risk of developing ASD after anterior cervical surgery. Copyright © 2013 Elsevier Inc. All rights reserved.

Comparative Analysis between Total Disc Replacement and Posterior Foraminotomy for Posterolateral Soft Disc Herniation with Unilateral Radiculopathy : Clinical and Biomechanical Results of a Minimum 5 Years Follow-up

PubMed Central

Kim, Kyoung-Tae; Cho, Dae-Chul; Sung, Joo-Kyung; Kim, Young-Baeg; Kim, Du Hwan

2017-01-01

Objective To compare the clinical outcomes and biomechanical effects of total disc replacement (TDR) and posterior cervical foraminotomy (PCF) and to propose relative inclusion criteria. Methods Thirty-five patients who underwent surgery between 2006 and 2008 were included. All patients had single-level disease and only radiculopathy. The overall sagittal balance and angle and height of a functional segmental unit (FSU; upper and lower vertebral body of the operative lesion) were assessed by preoperative and follow-up radiographs. C2–7 range of motion (ROM), FSU, and the adjacent segment were also checked. Results The clinical outcome of TDR (group A) was tended to be superior to that of PCF (group B) without statistical significance. In the group A, preoperative and postoperative upper adjacent segment level motion values were 8.6±2.3 and 8.4±2.0, and lower level motion values were 8.4±2.2 and 8.3±1.9. Preoperative and postoperative FSU heights were 37.0±2.1 and 37.1±1.8. In the group B, upper level adjacent segment motion values were 8.1±2.6 and 8.2±2.8, and lower level motion values were 6.5±3.3 and 6.3±3.1. FSU heights were 37.1±2.0 and 36.2±1.8. The postoperative FSU motion and height changes were significant (p<0.05). The patient’s satisfaction rates for surgery were 88.2% in group A and 88.8% in group B. Conclusion TDR and PCF have favorable outcomes in patients with unilateral soft disc herniation. However, patients have different biomechanical backgrounds, so the patient’s biomechanical characteristics and economic status should be understood and treated using the optimal procedure. PMID:28061490

Material Science in Cervical Total Disc Replacement.

PubMed

Pham, Martin H; Mehta, Vivek A; Tuchman, Alexander; Hsieh, Patrick C

2015-01-01

Current cervical total disc replacement (TDR) designs incorporate a variety of different biomaterials including polyethylene, stainless steel, titanium (Ti), and cobalt-chrome (CoCr). These materials are most important in their utilization as bearing surfaces which allow for articular motion at the disc space. Long-term biological effects of implanted materials include wear debris, host inflammatory immune reactions, and osteolysis resulting in implant failure. We review here the most common materials used in cervical TDR prosthetic devices, examine their bearing surfaces, describe the construction of the seven current cervical TDR devices that are approved for use in the United States, and discuss known adverse biological effects associated with long-term implantation of these materials. It is important to appreciate and understand the variety of biomaterials available in the design and construction of these prosthetics and the considerations which guide their implementation.

Material Science in Cervical Total Disc Replacement

PubMed Central

Pham, Martin H.; Mehta, Vivek A.; Tuchman, Alexander; Hsieh, Patrick C.

2015-01-01

Current cervical total disc replacement (TDR) designs incorporate a variety of different biomaterials including polyethylene, stainless steel, titanium (Ti), and cobalt-chrome (CoCr). These materials are most important in their utilization as bearing surfaces which allow for articular motion at the disc space. Long-term biological effects of implanted materials include wear debris, host inflammatory immune reactions, and osteolysis resulting in implant failure. We review here the most common materials used in cervical TDR prosthetic devices, examine their bearing surfaces, describe the construction of the seven current cervical TDR devices that are approved for use in the United States, and discuss known adverse biological effects associated with long-term implantation of these materials. It is important to appreciate and understand the variety of biomaterials available in the design and construction of these prosthetics and the considerations which guide their implementation. PMID:26523281

Severe impingement of lumbar disc replacements increases the functional biological activity of polyethylene wear debris.

PubMed

Baxter, Ryan M; Macdonald, Daniel W; Kurtz, Steven M; Steinbeck, Marla J

2013-06-05

Wear, oxidation, and particularly rim impingement damage of ultra-high molecular weight polyethylene total disc replacement components have been observed following surgical revision. However, neither in vitro testing nor retrieval-based evidence has shown the effect(s) of impingement on the characteristics of polyethylene wear debris. Thus, we sought to determine (1) differences in polyethylene particle size, shape, number, or biological activity that correspond to mild or severe rim impingement and (2) in an analysis of all total disc replacements, regardless of impingement classification, whether there are correlations between the extent of regional damage and the characteristics of polyethylene wear debris. The extent of dome and rim damage was characterized for eleven retrieved polyethylene cores obtained at revision surgery after an average duration of implantation of 9.7 years (range, 4.6 to 16.1 years). Polyethylene wear debris was isolated from periprosthetic tissues with use of nitric acid and was imaged with use of environmental scanning electron microscopy. Subsequently, particle size, shape, number, biological activity, and chronic inflammation scores were determined. Grouping of particles by size ranges that represented high biological relevance (<0.1 to 1-μm particles), intermediate biological relevance (1 to 10-μm particles), and low biological relevance (>10-μm particles) revealed an increased volume fraction of particles in the <0.1 to 1-μm and 1 to 10-μm size ranges in the mild-impingement cohort as compared with the severe-impingement cohort. The increased volume fractions resulted in a higher specific biological activity per unit particle volume in the mild-impingement cohort than in the severe-impingement cohort. However, functional biological activity, which is normalized by particle volume (mm3/g of tissue), was significantly higher in the severe-impingement cohort. This increase was due to a larger volume of particles in all three size ranges. In both cohorts, the functional biological activity correlated with the chronic inflammatory response, and the extent of rim penetration positively correlated with increasing particle size, number, and functional biological activity. The results of this study suggest that severe rim impingement increases the production of biologically relevant particles from motion-preserving lumbar total disc replacement components. Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Severe Impingement of Lumbar Disc Replacements Increases the Functional Biological Activity of Polyethylene Wear Debris

PubMed Central

Baxter, Ryan M.; MacDonald, Daniel W.; Kurtz, Steven M.; Steinbeck, Marla J.

2013-01-01

Background: Wear, oxidation, and particularly rim impingement damage of ultra-high molecular weight polyethylene total disc replacement components have been observed following surgical revision. However, neither in vitro testing nor retrieval-based evidence has shown the effect(s) of impingement on the characteristics of polyethylene wear debris. Thus, we sought to determine (1) differences in polyethylene particle size, shape, number, or biological activity that correspond to mild or severe rim impingement and (2) in an analysis of all total disc replacements, regardless of impingement classification, whether there are correlations between the extent of regional damage and the characteristics of polyethylene wear debris. Methods: The extent of dome and rim damage was characterized for eleven retrieved polyethylene cores obtained at revision surgery after an average duration of implantation of 9.7 years (range, 4.6 to 16.1 years). Polyethylene wear debris was isolated from periprosthetic tissues with use of nitric acid and was imaged with use of environmental scanning electron microscopy. Subsequently, particle size, shape, number, biological activity, and chronic inflammation scores were determined. Results: Grouping of particles by size ranges that represented high biological relevance (<0.1 to 1-μm particles), intermediate biological relevance (1 to 10-μm particles), and low biological relevance (>10-μm particles) revealed an increased volume fraction of particles in the <0.1 to 1-μm and 1 to 10-μm size ranges in the mild-impingement cohort as compared with the severe-impingement cohort. The increased volume fractions resulted in a higher specific biological activity per unit particle volume in the mild-impingement cohort than in the severe-impingement cohort. However, functional biological activity, which is normalized by particle volume (mm3/g of tissue), was significantly higher in the severe-impingement cohort. This increase was due to a larger volume of particles in all three size ranges. In both cohorts, the functional biological activity correlated with the chronic inflammatory response, and the extent of rim penetration positively correlated with increasing particle size, number, and functional biological activity. Conclusions: The results of this study suggest that severe rim impingement increases the production of biologically relevant particles from motion-preserving lumbar total disc replacement components. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence. PMID:23780545

77 FR 16917 - Airworthiness Directives; Rolls-Royce Deutschland Ltd & Co KG Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-23

... turbofan engines. This AD requires replacement of the high-pressure (HP) turbine spanner retaining nut... stage 2 high-pressure turbine (HPT) disc spanner retaining nuts did not receive the proper heat... HPT disc failure, possibly leading to release of high energy debris, resulting in damage to the...

Disc dislodgment in Björk Shiley mitral valve prosthesis: two successfully operated cases.

PubMed

Dubernet, J; Irarrázaval, M J; Urzúa, J; Maturana, G; Morán, S; Lema, G; Asenjo, F; Fajuri, A

1986-02-01

Two patients with Björk Shiley mitral valve replacement had migration and embolization of the occluding disc. One patient suffered migration of the disc a few hours after surgery and the other had a strut fracture with disc translocation six years after the initial operation. Clinical signs in both cases were pulmonary edema, cardiogenic shock, and absence of prosthetic sounds. Both patients were reoperated on an emergency basis, recovering after a complicated postoperative course. They are on functional Class I, 8 and 1 years later, respectively, with their dislodged discs still in the abdominal aorta. The only hope for survival in these patients is emergency reoperation, once the prosthetic mitral valve dysfunction is confirmed.

Development of injectable hydrogels for nucleus pulposus replacement

NASA Astrophysics Data System (ADS)

Thomas, Jonathan D.

Intervertebral disc degeneration has been reported as the underlying cause for 75% of cases of lower back pain and is marked by dehydration of the nucleus pulposus within the intervertebral disc. There have been many implant designs to replace the nucleus pulposus. Some researchers have proposed the replacement of the nucleus pulposus with hydrogel materials. The insertion of devices made from these materials further compromises the annulus of the disc. An ideal nucleus replacement could be injected into the disc space and form a solid in vivo. However, injectable replacements using curing elastomers and thermoplastic materials are not ideal because of the potentially harmful exothermic heat evolved from their reactions and the toxicity of the reactants used. We propose a hydrogel system that can be injected as a liquid at 25°C and solidified to yield a hydrogel within the intervertebral disc at 37°C. In aqueous solutions, these polymers have Lower Critical Solution Temperatures (LCST) between 25-37°C, making them unique candidate materials for this application. Poly(N-isopropylacrylamide) (PNIPAAm) is the most widely studied LCST polymer due to its drastic transition near body temperature. However, by itself, pure PNIPAAm forms a hydrogel that has low water content and can readily undergo plastic deformation. To increase the water content and impart elasticity to PNIPAAm hydrogels, grafted and branched hydrogel systems were created that incorporated the thermogelling PNIPAAm and hydrophilic poly(ethylene glycol) (PEG). In this research, the effects of polymer composition and monomer to initiator ratio, which controls polymer MW, on the in vitro swelling properties (mass, chemical, and compressive mechanical stability) of hydrogels formed from aqueous solutions of these polymers were evaluated. Immersion studies were also conducted in solutions to simulate the osmotic environment of the nucleus pulposus. The effects of repeated compression and unloading cycles on the water content and dimensional recovery of hydrogels made from three candidate polymer formulations were also determined. Unlike PNIPAAm and PEG grafted PNIPAAm hydrogels, PEG branched hydrogels have covalently linked networks. Addition of 7 mol% PEG branches to PNIPAAm resulted in a hydrogel with a higher water content and better elastic recovery than hydrogels made from pure PNIPAAm. PEG branched PNIPAAm hydrogels were shown to have mass, chemical, and compressive mechanical stability in vitro. Furthermore, these hydrogels showed superior dimensional recovery after compressive cycling than pure PNIPAAm and PEG grafted PNIPAAm hydrogels. The 7 mol% PEG branched PNIPAAm hydrogels have suitable swelling and mechanical properties to potentially serve as a nucleus pulposus replacement.

Disc erosion in Models 103 and 104 of Beall mitral valve prostheses

PubMed Central

Gómez, Ricardo; Verduras, María José; Lopez-Quintana, Alfonso; Riera, Luis; Zerolo, Ignacio; Martinez-Bordiu, Cristóbal

1981-01-01

Three cases of severe disc variance and erosion of the Teflon-disc Beall mitral valve prosthesis (Models 103 and 104) are reported. In two patients, the Beall mitral valves were excised and replaced with two Björk-Shiley mitral valves. The remaining patient did not survive, and at autopsy, the lens was found at the aortic bifurcation level. Because of this potentially lethal complication, careful follow-up of patients with Beall mitral valve prostheses (Models 103 and 104) is recommended. Images PMID:15216211

In vivo performance of an acellular disc-like angle ply structure (DAPS) for total disc replacement in a small animal model.

PubMed

Martin, John T; Kim, Dong Hwa; Milby, Andrew H; Pfeifer, Christian G; Smith, Lachlan J; Elliott, Dawn M; Smith, Harvey E; Mauck, Robert L

2017-01-01

Total intervertebral disc replacement with a biologic engineered disc may be an alternative to spinal fusion for treating end-stage disc disease. In previous work, we developed disc-like angle ply structures (DAPS) that replicate the structure and function of the native disc and a rat tail model to evaluate DAPS in vivo. Here, we evaluated a strategy in which, after in vivo implantation, endogenous cells could colonize the acellular DAPS and form an extracellular matrix organized by the DAPS topographical template. To do so, acellular DAPS were implanted into the caudal spines of rats and evaluated over 12 weeks by mechanical testing, histology, and microcomputed tomography. An external fixation device was used to stabilize the implant site and various control groups were included to evaluate the effect of immobilization. There was robust tissue formation within the DAPS after implantation and compressive mechanical properties of the implant matched that of the native motion segment. Immobilization provided a stable site for fibrous tissue formation after either a discectomy or a DAPS implantation, but bony fusion eventually resulted, with segments showing intervertebral bridging after long-term implantation, a process that was accelerated by the implanted DAPS. Thus, while compressive mechanical properties were replicated after DAPS implantation, methods to actively prevent fusion must be developed. Future work will focus on limiting fusion by remobilizing the motion segment after a period of integration, delivering pro-chondrogenic factors, and pre-seeding DAPS with cells prior to implantation. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:23-31, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

M6-C artificial disc placement.

PubMed

Coric, Domagoj; Parish, John; Boltes, Margaret O

2017-01-01

There has been a steady evolution of cervical total disc replacement (TDR) devices over the last decade resulting in surgical technique that closely mimics anterior cervical discectomy and fusion as well as disc design that emphasizes quality of motion. The M6-C TDR device is a modern-generation artificial disc composed of titanium endplates with tri-keel fixation as well as a polyethylene weave with a polyurethane core. Although not yet approved by the FDA, M6-C has finished a pilot and pivotal US Investigational Device Exemption (IDE) study. The authors present the surgical technique for implantation of a 2-level M6-C cervical TDR device. The video can be found here: https://youtu.be/rFEAqINLRCo .

Retrieval of a leaflet escaped in a Tri-technologies bileaflet mechanical prosthetic valve.

PubMed

Cianciulli, Tomás F; Lax, Jorge A; Saccheri, María C; Guidoin, Robert; Salvado, César M; Fernández, Adrián J; Prezioso, Horacio A

2008-01-01

The escape of the prosthetic heart valve disc is one of the causes of prosthetic dysfunction that requires emergency surgery. The removal of the embolized disc should be carried out because of the risk of a progressive extrusion on the aortic wall. Several imaging techniques can be used for the detection of the missing disc localization. In this report we describe a 32-year-old man who underwent mitral valve replacement with a Tri-technologies bileaflet valve three years ago, and was admitted in cardiogenic shock. Transesophageal echocardiography showed acute-onset massive mitral regurgitation. The patient underwent emergency replacement of the prosthetic valve. Only one of the two leaflets remained in the removed prosthetic valve. The missing leaflet could not be found within the cardiac cavity. The abdominal fluoroscopic study and plain radiography were unable to detect the escaped leaflet. The abdominal computed tomography scan and the ultrasound showed the escaped leaflet in the terminal portion of the aortic bifurcation. To retrieve the embolized disc laparotomy and aortotomy were performed three months later. The escaped leaflet shows a fracture of one of the pivot systems caused by structural failure. This kind of failure mode is usually the result of high stress concentration.

The biomechanics of a multilevel lumbar spine hybrid using nucleus replacement in conjunction with fusion.

PubMed

Dahl, Michael C; Ellingson, Arin M; Mehta, Hitesh P; Huelman, Justin H; Nuckley, David J

2013-02-01

Degenerative disc disease is commonly a multilevel pathology with varying deterioration severity. The use of fusion on multiple levels can significantly affect functionality and has been linked to persistent adjacent disc degeneration. A hybrid approach of fusion and nucleus replacement (NR) has been suggested as a solution for mildly degenerated yet painful levels adjacent to fusion. To compare the biomechanical metrics of different hybrid implant constructs, hypothesizing that an NR+fusion hybrid would be similar to a single-level fusion and perform more naturally compared with a two-level fusion. A cadaveric in vitro repeated-measures study was performed to evaluate a multilevel lumbar NR+fusion hybrid. Eight cadaveric spines (L3-S1) were tested in a Spine Kinetic Simulator (Instron, Norwood, MA, USA). Pure moments of 8 Nm were applied in flexion/extension, lateral bending, and axial rotation as well as compression loading. Specimens were tested intact; fused (using transforaminal lumbar interbody fusion instrumentation with posterior rods) at L5-S1; with a nuclectomy at L4-L5 including fusion at L5-S1; with NR at L4-L5 including fusion at L5-S1; and finally with a two-level fusion spanning L4-S1. Repeated-measures analysis of variance and corrected t tests were used to statistically compare outcomes. The NR+fusion hybrid and single-level fusion exhibited no statistical differences for range of motion (ROM), stiffness, neutral zone, and intradiscal pressure in all loading directions. Compared with two-level fusion, the hybrid affords the construct 41.9% more ROM on average. Two-level fusion stiffness was statistically higher than all other constructs and resulted in significantly lower ROM in flexion, extension, and lateral bending. The hybrid construct produced approximately half of the L3-L4 adjacent-level pressures as the two-level fusion case while generating similar pressures to the single-level fusion case. These data portend more natural functional outcomes and fewer adjacent disc complications for a multilevel NR+fusion hybrid compared with the classical two-level fusion. Copyright © 2013 Elsevier Inc. All rights reserved.

In vitro biomechanical comparison after fixed- and mobile-core artificial cervical disc replacement versus fusion

PubMed Central

Lou, Jigang; Li, Yuanchao; Wang, Beiyu; Meng, Yang; Wu, Tingkui; Liu, Hao

2017-01-01

Abstract In vitro biomechanical analysis after cervical disc replacement (CDR) with a novel artificial disc prosthesis (mobile core) was conducted and compared with the intact model, simulated fusion, and CDR with a fixed-core prosthesis. The purpose of this experimental study was to analyze the biomechanical changes after CDR with a novel prosthesis and the differences between fixed- and mobile-core prostheses. Six human cadaveric C2–C7 specimens were biomechanically tested sequentially in 4 different spinal models: intact specimens, simulated fusion, CDR with a fixed-core prosthesis (Discover, DePuy), and CDR with a mobile-core prosthesis (Pretic-I, Trauson). Moments up to 2 Nm with a 75 N follower load were applied in flexion–extension, left and right lateral bending, and left and right axial rotation. The total range of motion (ROM), segmental ROM, and adjacent intradiscal pressure (IDP) were calculated and analyzed in 4 different spinal models, as well as the differences between 2 disc prostheses. Compared with the intact specimens, the total ROM, segmental ROM, and IDP at the adjacent segments showed no significant difference after arthroplasty. Moreover, CDR with a mobile-core prosthesis presented a little higher values of target segment (C5/6) and total ROM than CDR with a fixed-core prosthesis (P > .05). Besides, the difference in IDP at C4/5 after CDR with 2 prostheses was without statistical significance in all the directions of motion. However, the IDP at C6/7 after CDR with a mobile-core prosthesis was lower than CDR with a fixed-core prosthesis in flexion, extension, and lateral bending, with significant difference (P < .05), but not under axial rotation. CDR with a novel prosthesis was effective to maintain the ROM at the target segment and did not affect the ROM and IDP at the adjacent segments. Moreover, CDR with a mobile-core prosthesis presented a little higher values of target segment and total ROM, but lower IDP at the inferior adjacent segment than CDR with a fixed-core prosthesis. PMID:29019902

The Yucatan Minipig Temporomandibular Joint Disc Structure-Function Relationships Support Its Suitability for Human Comparative Studies.

PubMed

Vapniarsky, Natalia; Aryaei, Ashkan; Arzi, Boaz; Hatcher, David C; Hu, Jerry C; Athanasiou, Kyriacos A

2017-11-01

Frequent involvement of the disc in temporomandibular joint (TMJ) disorders warrants attempts to tissue engineer TMJ disc replacements. Physiologically, a great degree of similarity is seen between humans and farm pigs (FPs), but the pig's rapid growth confers a significant challenge for in vivo experiments. Minipigs have a slower growth rate and are smaller than FPs, but minipig TMJ discs have yet to be fully characterized. The objective of this study was to determine the suitability of the minipig for TMJ studies by extensive structural and functional characterization. The properties of minipig TMJ discs closely reproduced previously reported morphological, biochemical, and biomechanical values of human and FP discs. The width/length dimension ratio of the minipig TMJ disc was 1.95 (1.69 for human and 1.94 for FP). The biochemical evaluation revealed, on average per wet weight, 24.3% collagen (22.8% for human and 24.9% for FP); 0.8% glycosaminoglycan (GAG; 0.5% for human and 0.4% for FP); and 0.03% DNA (0.008% for human and 0.02% for FP). Biomechanical testing revealed, on average, compressive relaxation modulus of 50 kPa (37 kPa for human and 32 kPa for FP), compressive instantaneous modulus of 1121 kPa (1315 kPa for human and 1134 kPa for FP), and coefficient of viscosity of 13 MPa·s (9 MPa·s for human and 3 MPa·s for FP) at 20% strain. These properties also varied topographically in accordance to those of human and FP TMJ discs. Anisotropy, quantified by bidirectional tensile testing and histology, again was analogous among minipig, human, and FP TMJ discs. The minipig TMJ's ginglymoarthrodial nature was verified through cone beam computer tomography. Collectively, the similarities between minipig and human TMJ discs support the use of minipig as a relevant model for TMJ research; considering the practical advantages conferred by its growth rate and size, the minipig may be a preferred model over FP.

Quality of systematic reviews: an example of studies comparing artificial disc replacement with fusion in the cervical spine.

PubMed

Tashani, Osama A; El-Tumi, Hanan; Aneiba, Khaled

2015-01-01

Cervical artificial disc replacement (C-ADR) is now an alternative to anterior cervical discectomy and fusion (ACDF). Many studies have evaluated the efficacy of C-ADR compared with ACDF. This led to a series of systematic reviews and meta-analyses to evaluate the evidence of the superiority of one intervention against the other. The aim of the study presented here was to evaluate the quality of these reviews and meta-analyses. Medline via Ovid, Embase, and Cochrane Library were searched using the keywords: (total disk replacement, prosthesis, implantation, discectomy, and arthroplasty) AND (cervical vertebrae, cervical spine, and spine) AND (systematic reviews, reviews, and meta-analysis). Screening and data extraction were conducted by two reviewers independently. Two reviewers then assessed the quality of the selected reviews and meta-analysis using 11-item AMSTAR score which is a validated measurement tool to assess the methodological quality of systematic reviews. Screening of full reports of 46 relevant abstracts resulted in the selection of 15 systematic reviews and/or meta-analyses as eligible for this study. The two reviewers' inter-rater agreement level was high as indicated by kappa of >0.72. The AMSTAR score of the reviews ranged from 3 to 11. Only one study (a Cochrane review) scored 100% (AMSTAR 11). Five studies scored below (AMSTAR 5) indicating low-quality reviews. The most significant drawbacks of reviews of a score below 5 were not using an extensive search strategy, failure to use the scientific quality of the included studies appropriately in formulating a conclusion, not assessing publication bias, and not reporting the excluded studies. With a significant exception of a Cochrane review, the methodological quality of systematic reviews evaluating the evidence of C-ADR versus ACDF has to be improved.

The 5-year cost-effectiveness of two-level anterior cervical discectomy and fusion or cervical disc replacement: a Markov analysis.

PubMed

Overley, Samuel C; McAnany, Steven J; Brochin, Robert L; Kim, Jun S; Merrill, Robert K; Qureshi, Sheeraz A

2018-01-01

Anterior cervical discectomy and fusion (ACDF) and cervical disc replacement (CDR) are both acceptable surgical options for the treatment of cervical myelopathy and radiculopathy. To date, there are limited economic analyses assessing the relative cost-effectiveness of two-level ACDF versus CDR. The purpose of this study was to determine the 5-year cost-effectiveness of two-level ACDF versus CDR. The study design is a secondary analysis of prospectively collected data. Patients in the Prestige cervical disc investigational device exemption (IDE) study who underwent either a two-level CDR or a two-level ACDF were included in the study. The outcome measures were cost and quality-adjusted life years (QALYs). A Markov state-transition model was used to evaluate data from the two-level Prestige cervical disc IDE study. Data from the 36-item Short Form Health Survey were converted into utilities using the short form (SF)-6D algorithm. Costs were calculated from the payer perspective. QALYs were used to represent effectiveness. A probabilistic sensitivity analysis (PSA) was performed using a Monte Carlo simulation. The base-case analysis, assuming a 40-year-old person who failed appropriate conservative care, generated a 5-year cost of $130,417 for CDR and $116,717 for ACDF. Cervical disc replacement and ACDF generated 3.45 and 3.23 QALYs, respectively. The incremental cost-effectiveness ratio (ICER) was calculated to be $62,337/QALY for CDR. The Monte Carlo simulation validated the base-case scenario. Cervical disc replacement had an average cost of $130,445 (confidence interval [CI]: $108,395-$152,761) with an average effectiveness of 3.46 (CI: 3.05-3.83). Anterior cervical discectomy and fusion had an average cost of $116,595 (CI: $95,439-$137,937) and an average effectiveness of 3.23 (CI: 2.84-3.59). The ICER was calculated at $62,133/QALY with respect to CDR. Using a $100,000/QALY willingness to pay (WTP), CDR is the more cost-effective strategy and would be selected 61.5% of the time by the simulation. Two-level CDR and ACDF are both cost-effective strategies at 5 years. Neither strategy was found to be more cost-effective with an ICER greater than the $50,000/QALY WTP threshold. The assumptions used in the analysis were strongly validated with the results of the PSA. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of total lumbar disc replacement on lumbosacral lordosis.

PubMed

Kasliwal, Manish K; Deutsch, Harel

2012-10-01

Original article : To study effect of lumbar disc replacement on lumbosacral lordosis. There has been a growing interest in total disc replacement (TDR) for back pain with the rising concern of adjacent segment degeneration. Lumbar fusion surgery has been shown to lead to decrease in lumbar lordosis, which may account for postfusion pain resulting in less acceptable clinical outcome after successful fusion. TDR has recently emerged as an alternative treatment for back pain. There have been very few studies reporting lumbar sagittal outcome after TDR. Retrospective study of radiographic data of 17 patients who underwent TDR for single level degenerative disc disease at the author's institution was carried out. Study included measurement of preoperative and postoperative segmental and global lumbar lordosis and angle of lordosis. Patients age varied from 19 to 54 (mean, 35) years. Follow-up ranged from 12 to 24 months. TDR was performed at L4-5 level in 3 patients and L5-S1 level in 14 patients. The average values for segmental lordosis, global lordosis, and angle of lordosis at the operated level before and after surgery were 17.3, 49.7, and 8.6 degrees and 21.6, 54, and 9.5 degrees, respectively. There was a trend toward significant (P=0.02) and near significant (P=0.057) increase in segmental and global lordosis, respectively after TDR. Although prosthesis increased angle of lordosis at the level implanted in majority of the patients, the difference in preoperative and postoperative angle of lordosis was not significant (P=0.438). In addition, there was no correlation between the angle of implant of chosen and postoperative angle of lordosis at the operated level. The effect of TDR on sagittal balance appears favorable with an increase in global and segmental lumbar lordosis after single level TDR for degenerative disc disease. The degree of postoperative angle of lordosis was not affected by the angle of implant chosen at the operated level and varied independently of the implant angle.

ReWritable Data Storage on DVD by Using Phase Change Technology

NASA Astrophysics Data System (ADS)

Kleine, H.; Martin, F.; Kapeller, M.; Cord, B.; Ebinger, H.

It is expected that the next few years the VHS casette will be replaced by rewritable Digital Versatile Discs (DVD) for home video recording. At this moment three different standards DVD+RW, DVD-RW and DVD-RAM exist, out of which the DVD+RW is expected to dominate the market in Europe and the United States. The disc holds 4.7 GB of computer data, which is equivalent to several hours of high quality video content. At the heart of the disc is a thin film layer stack with a special phase change recording layer. By proper laser irradiation the disc can be overwritten up to 1000 times without noticeable quality loss. A shelf lifetime of 20-50 years is anticipated. With these characteristics the disc is well suited for consumer applications. The present article illuminates how a process engineer can control the disc recording sensitivity, the recording speed and the number of overwriting cycles by the design of the thin film layer stack.

Clinical experience and two-year follow-up with a one-piece viscoelastic cervical total disc replacement.

PubMed

Chin, Kingsley Richard; Lubinski, Jacob Ryan; Zimmers, Kari Bracher; Sands, Barry Eugene; Pencle, Fabio

2017-12-01

The purpose of this study is to present clinical outcome data from a 2-year post-market study of a viscoelastic one-piece cervical total disc replacement (TDR) in Europe. Thirty-nine patients were implanted at five surgical sites in an European post-market clinical study. Clinical outcomes included improvement of neck disability index (NDI) and visual analog scale scores for neck and arm pain from baseline to 2-year follow-up, neurological examinations, patients view on the success of surgery, complications, and subsequent surgical interventions. Thirty patients had the Freedom ® Cervical Disc (FCD) implanted at a single level, and nine patients were implanted at two adjacent levels. The population had a similar distribution of male [20] and female [19] subjects, with a mean age of 45 years. All self-administered outcome measures showed significant clinically important improvements from baseline to the 2-year follow-up. Mean preoperative NDI score improved from 48% to 20%, 13%, 8%, 6% and 4% at 6 weeks, 3, 6, 12, and 24 months, respectively. Average preoperative visual analog scale (VAS) scores of the neck, right and left arm pain intensity and frequency showed significant improvement. All neurological outcome measurements showed immediate improvement from preoperative values and continued improvement throughout 2 years follow-up. From pre-op to 24 months, neurological deficits declined in the population from 21% to 6% for reflex function, 62% to 17% for sensory function, and 38% to 3% for motor function. No patients experienced a deterioration in any measured outcomes compared with the preoperative situation. Patient satisfaction increased over 2 years post-op, with 83% of patients responding that they would "definitely" choose to have the same treatment for their neck/arm condition and another 11% responding that they would "probably" choose to have the same treatment. The FCD performs as expected in patients with single-level and two-level degenerative disc disease.

[Self-assembly tissue engineering fibrocartilage model of goat temporomandibular joint disc].

PubMed

Kang, Hong; Li, Zhen-Qiang; Bi, Yan-Da

2011-06-01

To construct self-assembly fibrocartilage model of goat temporomandibular joint disc and observe the biological characteristics of the self-assembled fibrocartilage constructs, further to provide a basis for tissue engineering of the temporomandibular joint disc and other fibrocartilage. Cells from temporomandibular joint discs of goats were harvested and cultured. 5.5 x 10(6) cells were seeded in each agarose well with diameter 5 mm x depth 10 mm, daily replace of medium, cultured for 2 weeks. One day after seeding, goat temporomandibular joint disc cells in agarose wells were gathered and began to self-assemble into a disc-shaped base, then gradually turned into a round shape. When cultured for 2 weeks, hematoxylin-eosin staining was conducted and observed that cells were round and wrapped around by the matrix. Positive Safranin-O/fast green staining for glycosaminoglycans was observed throughout the entire constructs, and picro-sirius red staining was examined and distribution of numerous type I collagen was found. Immunohistochemistry staining demonstrated brown yellow particles in cytoplasm and around extracellular matrix, which showed self-assembly construct can produce type I collagen as native temporomandibular joint disc tissue. Production of extracellular matrix in self-assembly construct as native temporomandibular joint disc tissue indicates that the use of agarose wells to construct engineered temporomandibular joint disc will be possible and practicable.

Analysis of the Function of Apoptosis during Imaginal Wing Disc Regeneration in Drosophila melanogaster.

PubMed

Diaz-Garcia, Sandra; Ahmed, Sara; Baonza, Antonio

2016-01-01

Regeneration is the ability that allows organisms to replace missing organs or lost tissue after injuries. This ability requires the coordinated activity of different cellular processes, including programmed cell death. Apoptosis plays a key role as a source of signals necessary for regeneration in different organisms. The imaginal discs of Drosophila melanogaster provide a particularly well-characterised model system for studying the cellular and molecular mechanisms underlying regeneration. Although it has been shown that signals produced by apoptotic cells are needed for homeostasis and regeneration of some tissues of this organism, such as the adult midgut, the contribution of apoptosis to disc regeneration remains unclear. Using a new method for studying disc regeneration in physiological conditions, we have defined the pattern of cell death in regenerating discs. Our data indicate that during disc regeneration, cell death increases first at the wound edge, but as regeneration progresses dead cells can be observed in regions far away from the site of damage. This result indicates that apoptotic signals initiated in the wound spread throughout the disc. We also present results which suggest that the partial inhibition of apoptosis does not have a major effect on disc regeneration. Finally, our results suggest that during disc regeneration distinct apoptotic signals might be acting simultaneously.

Complete Transversal Disc Fracture in a Björk-Shiley Delrin Mitral Valve Prosthesis 43 Years After Implantation.

PubMed

González-Santos, Jose María; Arnáiz-García, María Elena; Dalmau-Sorlí, María José; Sastre-Rincón, Jose Alfonso; Hernández-Hernández, Jesús; Pérez-Losada, María Elena; Sagredo-Meneses, Víctor; López-Rodríguez, Javier

2016-10-01

A patient who underwent previous implantation of a mitral valve replacement with a Björk-Shiley Delrin (BSD) mitral valve prosthesis during infancy was admitted to our institution 43 years later after an episode of syncope and cardiac arrest. Under extreme hemodynamic instability, a mitral valve prosthetic dysfunction causing massive mitral regurgitation was identified. The patient underwent an emergent cardiac operation, and a complete disc fracture with partial disc migration was found. Exceptional cases of mechanical prosthetic heart valve fracture exist. We report the first case of complete transversal disc rupture of a BSD mitral valve prosthesis after the longest period of implantation ever reported in that position. Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Biomechanics of the L5-S1 motion segment after total disc replacement - Influence of iatrogenic distraction, implant positioning and preoperative disc height on the range of motion and loading of facet joints.

PubMed

Dreischarf, Marcel; Schmidt, Hendrik; Putzier, Michael; Zander, Thomas

2015-09-18

Total disc replacement has been introduced to overcome negative side effects of spinal fusion. The amount of iatrogenic distraction, preoperative disc height and implant positioning have been considered important for surgical success. However, their effect on the postoperative range of motion (RoM) and loading of the facets merits further discussion. A validated osteoligamentous finite element model of the lumbosacral spine was employed and extended with four additional models to account for different disc heights. An artificial disc with a fixed center of rotation (CoR) was implemented in L5-S1. In 4000 simulations, the influence of distraction and the CoR's location on the RoM, facet joint forces (FJFs) and facet capsule ligament forces (FCLFs) was investigated. Distraction substantially altered segmental kinematics in the sagittal plane by decreasing range of flexion (0.5° per 1mm of distraction), increasing range of extension (0.7°/mm) and slightly affecting complete sagittal RoM (0.2°/mm). The distraction already strongly increased the FCLFs during surgery (up to 230N) and in flexion (~12N/mm), with higher values in models with larger preoperative disc heights, and increased FJFs in extension. A more anterior implant location decreased the RoM in all planes. In most loading cases, a more posterior location of the implant's CoR increased the FJFs and FCLFs, whereas a more caudal location increased the FCLFs but decreased the FJFs. The results of this study may explain the worse clinical results in patients with overdistraction after TDR. The complete RoM in the sagittal plane appears to be insensitive to detecting surgery-related biomechanical changes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dynamic biomechanical examination of the lumbar spine with implanted total disc replacement using a pendulum testing system.

PubMed

Daniels, Alan H; Paller, David J; Koruprolu, Sarath; McDonnell, Matthew; Palumbo, Mark A; Crisco, Joseph J

2012-11-01

Biomechanical cadaver investigation. To examine dynamic bending stiffness and energy absorption of the lumbar spine with and without implanted total disc replacement (TDR) under simulated physiological motion. The pendulum testing system is capable of applying physiological compressive loads without constraining motion of functional spinal units (FSUs). The number of cycles to equilibrium observed under pendulum testing is a measure of the energy absorbed by the FSU. Five unembalmed, frozen human lumbar FSUs were tested on the pendulum system with axial compressive loads of 181 N, 282 N, 385 N, and 488 N before and after Synthes ProDisc-L TDR implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5º resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and bending stiffness (N·m/º) was calculated and compared for each testing mode. In flexion/extension, the TDR constructs reached equilibrium with significantly (P < 0.05) fewer cycles than the intact FSU with compressive loads of 282 N, 385 N, and 488 N. Mean dynamic bending stiffness in flexion, extension, and lateral bending increased significantly with increasing load for both the intact FSU and TDR constructs (P < 0.001). In flexion, with increasing compressive loading from 181 N to 488 N, the bending stiffness of the intact FSUs increased from 4.0 N·m/º to 5.5 N·m/º, compared with 2.1 N·m/º to 3.6 N·m/º after TDR implantation. At each compressive load, the intact FSU was significantly stiffer than the TDR (P < 0.05). Lumbar FSUs with implanted TDR were found to be less stiff, but absorbed more energy during cyclic loading with an unconstrained pendulum system. Although the effects on clinical performance of motion-preserving devices are not fully known, these results provide further insight into the biomechanical behavior of these devices under approximated physiological loading conditions.

Cervical Disk Replacement With Discover Versus Fusion in a Single-Level Cervical Disk Disease: A Prospective Single-Center Randomized Trial With a Minimum 2-Year Follow-up.

PubMed

Rožanković, Marjan; Marasanov, Sergej M; Vukić, Miroslav

2017-06-01

Prospective randomized study. To compare the clinical outcome after Discover arthroplasty versus anterior cervical discectomy and fusion (ACDF) in patients treated for symptomatic single-level cervical disk disease. ACDF is still the gold standard for surgical treatment of cervical spine degenerative disk disease. However, results of many studies suggest that it may cause degenerative changes at levels immediately above and below the fusion, known as adjacent segment degenerative disease. Cervical arthroplasty has recently been introduced as an alternative to standard procedure of ACDF. It showed decreased surgical morbidity, decreased complications from postoperative immobilization, and an earlier return to previous level of function. A total of 105 consecutive patients with single-level cervical disk disease, producing radiculopathy and/or myelopathy were randomly divided into groups to undergo ACDF or Discover arthroplasty. All patients were evaluated with preoperative and postoperative serial radiographic studies and clinically, using Neck Disability Index, Visual Analog Scale and neurological status at 3, 6, 12, and 24 months. The results of our study indicate that cervical arthroplasty using Discover Artificial Cervical Disc provides favorable clinical and radiologic outcomes in a follow-up period of 24 months. There has been significant improvement in clinical parameters, Visual Analog Scale and Neck Disability Index, at 3, 6, 12, and 24 months in arthroplasty group comparing to control group. The Discover artificial cervical disc replacement offers favorable outcome compared with ACDF for a single-level cervical disk disease at short-term and long-term follow-up.

Wear characteristics of an unconstrained lumbar total disc replacement under a range of in vitro test conditions

PubMed Central

Fisher, John; Hall, Richard M.

2015-01-01

Abstract The effect of kinematics, loading and centre of rotation on the wear of an unconstrained total disc replacement have been investigated using the ISO 18192‐1 standard test as a baseline. Mean volumetric wear rate and surface morphological effects were reported. Changing the phasing of the flexions to create a low (but finite) amount of crossing path motion at the bearing surfaces resulted in a significant fall in wear volume. However, the rate of wear was still much larger than previously reported values under zero cross shear conditions. Reducing the load did not result in a significant change in wear rate. Moving the centre of rotation of the disc inferiorly did significantly increase wear rate. A phenomenon of debris re‐attachment on the UHMWPE surface was observed and hypothesised to be due to a relatively harsh tribological operating regime in which lubricant replenishment and particle migration out of the bearing contact zone were limited. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 46–52, 2017. PMID:26411540

[Surgical treatment of thoracic disc herniation].

PubMed

Hrabálek, L; Kalita, O; Langová, K

2010-08-01

The aim of this study was to compare the efficiency of different surgical approaches to thoracic disc herniation, and to show the role of segmental fusion and selection of an appropriate microsurgical decompression technique for the successful outcome of surgery. A group of 27 patients, 10 men and 17 women, between 31 and 70 years (average age, 49.33 years) were included in this prospective study. They underwent surgery for thoracic degeneration disc disease in the period from June 1994 to August 2008. In all patients, the severity of myelopathy was assessed using the grading Frankel system and JOA score, axial and radicular pain intensity was evaluated with VAS and ODI rating systems. The diagnosis was established on the basis of thoracic spine radiography, thoracic spine MRI and a CT scan of the segment. A total of 30 thoracic segments, in the range of Th4/Th5 to Th12/L1, were indicated for surgery. Localisation of the hernia was medial at 19 segments, mediolateral at three and lateral at eight segments. Soft disc herniation was found in 17 cases and hard disc protrusion at the remaining 13 segments. Surgery for significant myelopathy was carried out in 23 patients and for pain in four patients. According to the surgical procedure used, the patients were allocated to two groups: group A comprised 10 patients treated without disc replacement through a laminectomy or a costotransversectomy exposure, and group B consisted of 17 patients undergo- ing intersomatic fusion via a thoracotomy. Clinical and radiographic examinations were made at regular intervals for at least 1 year of follow-up. The results of clinical assessment, including JOA scores, JOA Recovery Rate, VAS scores at rest and after exercise and ODI, were statistically analysed for each group and compared. There was a statistically significant difference in JOA evaluation of myelopathy between the groups in group A, the mean JOA score declined from 7.9 to 7.0, i.e., -0.9 point, while in group B it increased from 6.71 to 9.12, i.e., +2.41 points. The mean JOA Recovery Rate did not reach a plus value in group A, while in group B it improved by 55 %. JOA Recovery Rate: Of the seven patients in group A evaluated for myelopathy, a fair result was in one, unchanged in two and worse in four patients. Of the 16 patients evaluated for myelopathy in group B, the results were excellent in four, good in six, fair in four and unchanged in two patients. Frankel grade function: In group A, one patient improved by one grade, two remained unchanged, two deteriorated by one grade and two by two grades. In group B, five patients improved by one grade, two patients by two grades and two patients by three grades. Eight patients remained unchanged and no patient deteriorated. The post-operative pain intensity, as assessed by the mean VAS score, was lower at rest and after exercise in both groups; the score was better in group B, but the difference was not statistically significant. The ODI was evaluated only in group B its mean value improved from 41.4% to 26.1%, i.e., by 15.3%. Between 7 to 15 % of the patients have asymptomatic thoracic disc herniation, while symptomatic herniation is very rare and accounts for only 0.25 % to 0.57 % of herniated discs in the whole spine. Severe or progressive myelopathy is a clear indication for surgical intervention in thoracic disc herniation, but the role of surgery in pain control is controversial. There are five approaches for thoracic disc herniation. Transpleural anterolateral thoracotomy has an advantage over the other methods because it permits the treatment of all types of herniation, whether localised centrally, laterally or contralaterally, i.e., soft, calcified or sequestered intradural disc herniation. The results of treatment will depend on the outcome of surgical spinal cord decompression and the degree of spinal stabilisation achieved. The surgical procedure via thoracotomy with intersomatic fusion resulted in a statistically more significant improvement of myelopathy than the posterior approach without disc replacement, and it provided greater pain relief. The authors recommend to treat thoracic disc herniation by discectomy via a thoracotomy and by intersomatic fusion.

Cost-effectiveness of total disc replacement versus multidisciplinary rehabilitation in patients with chronic low back pain: a Norwegian multicenter RCT.

PubMed

Johnsen, Lars Gunnar; Hellum, Christian; Storheim, Kjersti; Nygaard, Øystein P; Brox, Jens Ivar; Rossvoll, Ivar; Rø, Magne; Andresen, Hege; Lydersen, Stian; Grundnes, Oliver; Pedersen, Marit; Leivseth, Gunnar; Olafsson, Gylfi; Borgström, Fredrik; Fritzell, Peter

2014-01-01

Randomized clinical trial with 2-year follow-up. To evaluate the cost-effectiveness of total disc replacement (TDR) versus multidisciplinary rehabilitation (MDR) in patients with chronic low back pain (CLBP). The existing studies on CLBP report cost-effectiveness of fusion surgery versus disc replacement and fusion versus rehabilitation. This study evaluated the cost-effectiveness of TDR versus MDR. Between April 2004 and May 2007, 173 patients with CLBP (>1 yr) were randomized to TDR (n = 86) or MDR (n = 87). Treatment effects (Euro Qol 5D [EQ-5D] and Short Form 6D [SF-6D]) and relevant direct and indirect costs at 6 weeks and at 3, 6, 12, and 24 months after treatment were assessed. Gain in quality-adjusted life years (QALYs) after 2 years was estimated. Cost-effectiveness was expressed as an incremental cost-effectiveness ratio. The mean QALYs gained (standard deviation) using EQ-5D was 1.29 (0.53) in the TDR group and 0.95 (0.52) in the MDR group, a significant difference of 0.34 (95% confidence interval 0.18-0.50). The mean total cost per patient in the TDR group was &OV0556;87,622 (58,351) compared with &OV0556;74,116 (58,237) in the MDR group, which was not significantly different (95% confidence interval: -4041 to 31,755). The incremental cost-effectiveness ratio for the TDR procedure varied from &OV0556;39,748 using EQ-5D (TDR cost-effective) to &OV0556;128,328 using SF-6D (TDR not cost-effective). The dropout rate was 20% (15% TDR group, 24% MDR group). Five patients moved from the MDR to the TDR group, whereas 9 patients randomized to TDR declined surgery. Using per-protocol analysis instead of intention-to-treat analysis indicated that TDR was not cost-effective, irrespective of the use of EQ-5D or SF-6D. In this study, TDR was cost-effective compared with MDR after 2 years when using EQ-5D for assessing QALYs gained and a willingness to pay of &OV0556;74,600 (kr500,000/QALY). TDR was not cost-effective when SF-6D was used; therefore, our results should be interpreted with caution. Longer follow-up is needed to accurately assess the cost-effectiveness of TDR. 2.

Disc-halo interactions in ΛCDM

NASA Astrophysics Data System (ADS)

Bauer, Jacob S.; Widrow, Lawrence M.; Erkal, Denis

2018-05-01

We present a new method for embedding a stellar disc in a cosmological dark matter halo and provide a worked example from a Λ cold dark matter zoom-in simulation. The disc is inserted into the halo at a redshift z = 3 as a zero-mass rigid body. Its mass and size are then increased adiabatically while its position, velocity, and orientation are determined from rigid-body dynamics. At z = 1, the rigid disc (RD) is replaced by an N-body disc whose particles sample a three-integral distribution function (DF). The simulation then proceeds to z = 0 with live disc (LD) and halo particles. By comparison, other methods assume one or more of the following: the centre of the RD during the growth phase is pinned to the minimum of the halo potential, the orientation of the RD is fixed, or the live N-body disc is constructed from a two rather than three-integral DF. In general, the presence of a disc makes the halo rounder, more centrally concentrated, and smoother, especially in the innermost regions. We find that methods in which the disc is pinned to the minimum of the halo potential tend to overestimate the amount of adiabatic contraction. Additionally, the effect of the disc on the subhalo distribution appears to be rather insensitive to the disc insertion method. The LD in our simulation develops a bar that is consistent with the bars seen in late-type spiral galaxies. In addition, particles from the disc are launched or `kicked up' to high galactic latitudes.

Water and Salt Stresses, Kinetin and Protein Synthesis in Tobacco Leaves 1

PubMed Central

Ben-Zioni, Aliza; Itai, C.; Vaadia, Y.

1967-01-01

The capacity of tobacco (Nicotiana rustica) leaf discs to incorporate l-leucine 14C into proteins was measured. Leaf discs were obtained from plants which experienced soil water depletion, or which were exposed to a saline or osmotic stress in the root medium. The stresses were brief of relatively short duration and water potential did not decrease below 4 bars in the root media. Leaf discs were sampled 2 hours after stress removal, achieved by reirrigation, or replacement of saline and osmotic solutions with normal nutrient solution. Plants were always turgid when leaves were sampled. All stressed tissues showed reduced capacity to incorporate l-leucine 14C into protein. The reduction was about 50% and could not be attributed either to reduced uptake into the discs, or to possible isotopic dilution. Incorporation decreased progressively with leaf age in control discs as well as in stressed leaf discs. At all ages tested, incorporation in stressed discs was lower than that of the control. Full recovery of incorporation capacity in stressed discs was obtained when discs were sampled 72 hours after stress removal but not earlier. Kinetin pretreatment prior to incubation with labelled leucine partially restored incorporation in stressed discs. The differences in response to kinetin of stressed and control discs suggest a lower endogenous level of cytokinins in the stressed discs. The results were qualitatively similar regardless of the kind of stress given to the plants during pretreatment. This supports the hypothesis that the normal supply of root cytokinins is important in shoot metabolism. PMID:16656515

Cervical Laminoplasty

MedlinePlus

... Medicine Acupuncture Herbal Supplements Surgical Options Anterior Cervical Fusion Artifical Disc Replacement (ADR) Bone Graft Alternatives Bone ... Percutaneous Vertebral Augmentation (PVA) Posterior Cervical Foraminotomy Spinal ... Nonsurgical Treatments Activity Modification Chiropractic – A Conversation with ...

Cervical hybrid arthroplasty with 2 unique fusion techniques.

PubMed

Cardoso, Mario J; Mendelsohn, Audra; Rosner, Michael K

2011-07-01

Multilevel cervical arthroplasty achieved using the Prestige ST disc can be challenging and often unworkable. An alternative to this system is a hybrid technique composed of alternating total disc replacements (TDRs) and fusions. In the present study, the authors review the safety and radiological outcomes of cervical hybrid arthroplasty in which the Prestige ST disc is used in conjunction with 2 unique fusion techniques. After obtaining institutional review board approval, the authors completed a retrospective review of all hybrid cervical constructs in which the Prestige ST disc was used between August 2007 and November 2009 at the Walter Reed Army Medical Center. A Prestige ST total disc replacement was performed in 119 patients. Thirty-one patients received a hybrid construct defined as a TDR and fusion (TDR-anterior cervical decompression and fusion [ACDF]) or as 2 TDRs separated by a fusion (TDR-ACDF-TDR). A resorbable plate and graft system (Mystique) or stand-alone interbody spacer (Prevail) was implanted at the fusion levels. Plain radiographs were compared and evaluated for cervical lordosis, range of motion, implant complications, development of adjacent-level disease, and pseudarthrosis. In addition, charts were reviewed for clinical complications related to the index surgery. Thirty-one patients (18 men and 13 women; mean age 50 years, range 32-74 years) received a hybrid construct. All patients were diagnosed with radiculopathy and/or myelopathy. Twenty-four patients received a 2-level and 7 a 3-level hybrid construct. In 2 patients in whom a 2-level hybrid construct was implanted, a noncontiguous TDR was also performed. The mean clinical and radiological follow-up duration was 18 months. There was no significant difference in preoperative (19.3° ± 13.3°) and postoperative (19.7° ± 10.5°) cervical lordosis (p = 0.48), but there was a significant decrease in range in motion (from 50.0° ± 11.8° to 38.9° ± 12.7°) (p = 0.003). There were no instances of screw backout, implant dislodgement, progressive kyphosis, formation of heterotopic bone, pseudarthrosis, or symptomatic adjacent-level disease. Seven patients had dysphasia and 1 patient had vocal cord paralysis at 6 weeks. By 3 months, both the dysphasia and the vocal cord paralysis were resolved in all patients. Hybrid cervical arthroplasty involving the placement of a Prestige ST disc and either the Mystique resorbable plate or Prevail stand-alone interbody device is a safe and effective alternative to multilevel fusion for the management of cervical radiculopathy and myelopathy.

Prospective, Randomized Comparison of One-level Mobi-C Cervical Total Disc Replacement vs. Anterior Cervical Discectomy and Fusion: Results at 5-year Follow-up

PubMed Central

Zigler, Jack E.; Jackson, Robert; Nunley, Pierce D.; Bae, Hyun W.; Kim, Kee D.; Ohnmeiss, Donna D.

2016-01-01

Introduction There is increasing interest in the role of cervical total disc replacement (TDR) as an alternative to anterior cervical discectomy and fusion (ACDF). Multiple prospective randomized studies with minimum 2 year follow-up have shown TDR to be at least as safe and effective as ACDF in treating symptomatic degenerative disc disease at a single level. The purpose of this study was to compare outcomes of cervical TDR using the Mobi-C® with ACDF at 5-year follow-up. Methods This prospective, randomized, controlled trial was conducted as a Food and Drug Administration regulated Investigational Device Exemption trial across 23 centers with 245 patients randomized (2:1) to receive TDR with Mobi-C® Cervical Disc Prosthesis or ACDF with anterior plate and allograft. Outcome assessments included a composite overall success score, Neck Disability Index (NDI), visual analog scales (VAS) assessing neck and arm pain, Short Form-12 (SF-12) health survey, patient satisfaction, major complications, subsequent surgery, segmental range of motion, and adjacent segment degeneration. Results The 60-month follow-up rate was 85.5% for the TDR group and 78.9% for the ACDF group. The composite overall success was 61.9% with TDR vs. 52.2% with ACDF, demonstrating statistical non-inferiority. Improvements in NDI, VAS neck and arm pain, and SF-12 scores were similar between groups and were maintained from earlier follow-up through 60 months. There was no significant difference between TDR and ACDF in adverse events or major complications. Range of motion was maintained with TDR through 60 months. Device-related subsequent surgeries (TDR: 3.0%, ACDF: 11.1%, p<0.02) and adjacent segment degeneration at the superior level (TDR: 37.1%, ACDF: 54.7%, p<0.03) were significantly lower for TDR patients. Conclusions Five-year results demonstrate the safety and efficacy of TDR with the Mobi-C as a viable alternative to ACDF with the potential advantage of lower rates of reoperation and adjacent segment degeneration, in the treatment of one-level symptomatic cervical degenerative disc disease. Clinical Relevance This prospective, randomized study with 5-year follow-up adds to the existing literature indicating that cervical TDR is a viable alternative to ACDF in appropriately selected patients. Level of Evidence This is a Level I study. PMID:27162712

Physiotherapeutic Rehabilitation Following Lumbar Total Disc Replacement: A Retrospective Study.

PubMed

Green, Adeline; Gilbert, Philippa; Scott-Young, Matthew; Abbott, Allan

2016-09-01

This study sought to answer the following questions: What are the outcomes of physiotherapy post lumbar total disc replacement (LTDR) compared with patient self-mediated rehabilitation? Is a difference in outcomes related to the number of physiotherapy sessions? This is a retrospective observational study of 600 patients post TDR. Patient outcomes for self-mediated rehabilitation (Group 1), 1-3 sessions of clinic-based physiotherapy (Group 2) and ≥4 sessions of clinic-based physiotherapy (Group 3) were analysed. Outcomes measures included the Oswestry Disability Index (ODI), Roland Morris Disability Questionnaire (RMQ), Short Form-36 Physical (SF-36 PCS) and Mental Subscale Components (SF-36 MCS), Visual Analogue Scale (VAS) for back and leg pain intensity. Patient's pre-operative baseline measures and post-operative follow-up measures at 3, 6, 12 and 24 months post-operatively were analysed. Oswestry Disability Index and RMQ had significantly lower scores in Group 3 compared with Group 1 at 3, 6, 12 and 24 months follow-up. Significantly lower scores for Group 2 compared with Group 1 were observed for the ODI at 3 months follow-up and for the RMQ at 3 and 6 months follow-up. Significantly lower scores were observed in Group 3 compared with Group 1 for VAS back pain at 3 months and VAS leg pain at 6 months follow-up. Significantly higher scores in Group 3 compared with Group 1 were also observed in the SF-36 PCS at 6, 12 and 24 months. Significantly higher scores in Group 2 compared with Group 1 were observed at 6 months follow up. These trends were also observed when investigating the percentage of patients with a greater 50% improvement in the outcome measure. Physiotherapy post-LTDR produces statistically significant and possibly clinically important improvements in functional disability, pain and quality of life outcomes compared with self-mediated rehabilitation. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Artificial Disc Replacement

MedlinePlus

... Cervical Foraminotomy Spinal Fusion Nonsurgical Treatments Activity Modification Chiropractic – A Conversation with Dr. Jordan Gliedt, DC Directional ... with non-operative care such as medication, injections, chiropractic care and/or physical therapy. Typically, you will ...

The use of polyurethane materials in the surgery of the spine: a review.

PubMed

St John, Kenneth R

2014-12-01

The spine contains intervertebral discs and the interspinous and longitudinal ligaments. These structures are elastomeric or viscoelastic in their mechanical properties and serve to allow and control the movement of the bony elements of the spine. The use of metallic or hard polymeric devices to replace the intervertebral discs and the creation of fusion masses to replace discs and/or vertebral bodies changes the load transfer characteristics of the spine and the range of motion of segments of the spine. The purpose of the study was to survey the literature, regulatory information available on the Web, and industry-reported device development found on the Web to ascertain the usage and outcomes of the use of polyurethane polymers in the design and clinical use of devices for spine surgery. A systematic review of the available information from all sources concerning the subject materials' usage in spinal devices was conducted. A search of the peer-reviewed literature combining spinal surgery with polyurethane or specific types and trade names of medical polyurethanes was performed. Additionally, information available on the Food and Drug Administration Web site and for corporate Web sites was reviewed in an attempt to identify pertinent information. The review captured devices that are in testing or have entered clinical practice that use elastomeric polyurethane polymers as disc replacements, dynamic stabilization of spinal movement, or motion limitation to relieve nerve root compression and pain and as complete a listing as possible of such devices that have been designed or tested but appear to no longer be pursued. This review summarizes the available information about the uses to which polyurethanes have been tested or are being used in spinal surgery. The use of polyurethanes in medicine has expanded as modifications to the stability of the polymers in the physiological environment have been improved. The potential for the use of elastomeric materials to more closely match the mechanical properties of the structures being replaced and to maintain motion between spinal segments appears to hold promise. The published results from the use of the devices that are discussed show early success with these applications of elastomeric materials. Copyright © 2014 Elsevier Inc. All rights reserved.

Biomechanical changes of the lumbar segment after total disc replacement : charite(r), prodisc(r) and maverick(r) using finite element model study.

PubMed

Kim, Ki-Tack; Lee, Sang-Hun; Suk, Kyung-Soo; Lee, Jung-Hee; Jeong, Bi-O

2010-06-01

The purpose of this study was to analyze the biomechanical effects of three different constrained types of an artificial disc on the implanted and adjacent segments in the lumbar spine using a finite element model (FEM). The created intact model was validated by comparing the flexion-extension response without pre-load with the corresponding results obtained from the published experimental studies. The validated intact lumbar model was tested after implantation of three artificial discs at L4-5. Each implanted model was subjected to a combination of 400 N follower load and 5 Nm of flexion/extension moments. ABAQUS version 6.5 (ABAQUS Inc., Providence, RI, USA) and FEMAP version 8.20 (Electronic Data Systems Corp., Plano, TX, USA) were used for meshing and analysis of geometry of the intact and implanted models. Under the flexion load, the intersegmental rotation angles of all the implanted models were similar to that of the intact model, but under the extension load, the values were greater than that of the intact model. The facet contact loads of three implanted models were greater than the loads observed with the intact model. Under the flexion load, three types of the implanted model at the L4-5 level showed the intersegmental rotation angle similar to the one measured with the intact model. Under the extension load, all of the artificial disc implanted models demonstrated an increased extension rotational angle at the operated level (L4-5), resulting in an increase under the facet contact load when compared with the adjacent segments. The increased facet load may lead to facet degeneration.

ISASS Policy Statement – Lumbar Artificial Disc

PubMed Central

Garcia, Rolando

2015-01-01

Purpose The primary goal of this Policy Statement is to educate patients, physicians, medical providers, reviewers, adjustors, case managers, insurers, and all others involved or affected by insurance coverage decisions regarding lumbar disc replacement surgery. Procedures This Policy Statement was developed by a panel of physicians selected by the Board of Directors of ISASS for their expertise and experience with lumbar TDR. The panel's recommendation was entirely based on the best evidence-based scientific research available regarding the safety and effectiveness of lumbar TDR. PMID:25785243

Subsequent surgery rates after cervical total disc replacement using a Mobi-C Cervical Disc Prosthesis versus anterior cervical discectomy and fusion: a prospective randomized clinical trial with 5-year follow-up.

PubMed

Jackson, Robert J; Davis, Reginald J; Hoffman, Gregory A; Bae, Hyun W; Hisey, Michael S; Kim, Kee D; Gaede, Steven E; Nunley, Pierce Dalton

2016-05-01

OBJECTIVE Cervical total disc replacement (TDR) has been shown in a number of prospective clinical studies to be a viable treatment alternative to anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic degenerative disc disease. In addition to preserving motion, evidence suggests that cervical TDR may result in a lower incidence of subsequent surgical intervention than treatment with fusion. The goal of this study was to evaluate subsequent surgery rates up to 5 years in patients treated with TDR or ACDF at 1 or 2 contiguous levels between C-3 and C-7. METHODS This was a prospective, multicenter, randomized, unblinded clinical trial. Patients with symptomatic degenerative disc disease were enrolled to receive 1- or 2-level treatment with either TDR as the investigational device or ACDF as the control treatment. There were 260 patients in the 1-level study (179 TDR and 81 ACDF patients) and 339 patients in the 2-level study (234 TDR and 105 ACDF patients). RESULTS At 5 years, the occurrence of subsequent surgical intervention was significantly higher among ACDF patients for 1-level (TDR, 4.5% [8/179]; ACDF, 17.3% [14/81]; p = 0.0012) and 2-level (TDR, 7.3% [17/234]; ACDF, 21.0% [22/105], p = 0.0007) treatment. The TDR group demonstrated significantly fewer index- and adjacent-level subsequent surgeries in both the 1- and 2-level cohorts. CONCLUSIONS Five-year results showed treatment with cervical TDR to result in a significantly lower rate of subsequent surgical intervention than treatment with ACDF for both 1 and 2 levels of treatment. Clinical trial registration no.: NCT00389597 ( clinicaltrials.gov ).

Return to Sports After Cervical Total Disc Replacement.

PubMed

Reinke, Andreas; Behr, Michael; Preuss, Alexander; Villard, Jimmy; Meyer, Bernhard; Ringel, Florian

2017-01-01

Total disc replacement (TDR) is typically indicated in young patients with a cervical soft disc herniation. There are few data on the activity level of patients after cervical TDR, in particular from young patients who are expected to have a high activity level with frequent exercising. The expectation is that returning to active sports after cervical TDR is not restricted. Fifty patients were treated with a monosegmental cervical TDR at our department between May 2006 and March 2012. Clinical status and radiographic parameters were evaluated preoperatively and during follow-up. In addition, information was gathered regarding neck disability index, pain, a questionnaire concerning athletic aspects, and a modified Tegner activity score. The study design was a prospective case series. All patients were treated with the Prestige artificial cervical disc for a single-level soft disc herniation with radiculopathy. The average age was 40 years, and the mean follow-up period was 53 months (range, 26-96). The median neck disability index during follow-up was 5, and median visual analog scale for pain was 2. Two professional athletes, 20 semiprofessionals, 24 hobby athletes, and 5 patients with a very low activity level were treated. The median time to resumption of sporting activity was 4 weeks after surgery. All professionals and semiprofessionals recovered to their previous activity level. All of the 20 hobby athletes recovered to resume their sport participation. The modified Tegner preoperative score was 4 and the postoperative score was 3.5 (P = 0.806). We found that cervical TDR did not prohibit sporting activities. All patients recovered and were able to take part in their previous activities at an appropriate intensity level. Copyright © 2016 Elsevier Inc. All rights reserved.

Doughnut strikes sandwich: the geometry of hot medium in accreting black hole X-ray binaries

NASA Astrophysics Data System (ADS)

Poutanen, Juri; Veledina, Alexandra; Zdziarski, Andrzej A.

2018-06-01

We study the effects of the mutual interaction of hot plasma and cold medium in black hole binaries in their hard spectral state. We consider a number of different geometries. In contrast to previous theoretical studies, we use a modern energy-conserving code for reflection and reprocessing from cold media. We show that a static corona above an accretion disc extending to the innermost stable circular orbit produces spectra not compatible with those observed. They are either too soft or require a much higher disc ionization than that observed. This conclusion confirms a number of previous findings, but disproves a recent study claiming an agreement of that model with observations. We show that the cold disc has to be truncated in order to agree with the observed spectral hardness. However, a cold disc truncated at a large radius and replaced by a hot flow produces spectra which are too hard if the only source of seed photons for Comptonization is the accretion disc. Our favourable geometry is a truncated disc coexisting with a hot plasma either overlapping with the disc or containing some cold matter within it, also including seed photons arising from cyclo-synchrotron emission of hybrid electrons, i.e. containing both thermal and non-thermal parts.

Biomechanical Characterization of an Annulus Sparing Spinal Disc Prosthesis

PubMed Central

Buttermann, Glenn R.; Beaubien, Brian P.

2009-01-01

Background Context Current spine arthroplasty devices, require disruption of the annulus fibrosus for implantation. Preliminary studies of a unique annulus sparing intervertebral prosthetic disc (IPD), found that preservation of the annulus resulted in load sharing of the annulus with the prosthesis. Purpose Determine flexibility of the IPD versus fusion constructs in normal and degenerated human spines. Study design/Setting Biomechanical comparison of motion segments in the intact, fusion and mechanical nucleus replacement states for normal and degenerated states. Patient setting Thirty lumbar motion segments. Outcomes Measures Intervertebral height; motion segment range-of-motion (ROM), neutral zone (NZ), stiffness. Methods Motion segments had multi-directional flexibility testing to 7.5 Nm for intact discs, discs reconstructed using the IPD (n=12), or after anterior/posterior fusions (n=18). Interbody height and axial compression stiffness changes were determined for the reconstructed discs by applying axial compression to 1500 N. Analysis included stratifying results to normal mobile vs. rigid degenerated intact motion segments. Results The mean interbody height increase was 1.5 mm for IPD reconstructed discs. vs 3.0 mm for fused segments. Axial compression stiffness was 3.0 ± 0.9 kN/mm for intact compared to 1.2 ± 0.4 kN/mm for IPD reconstructed segments. Reconstructed disc ROM was 9.0° ± 3.7° in flexion-extension, 10.6° ± 3.4° in lateral bending and 2.8° ± 1.4° in axial torsion which was similar to intact values and significantly greater than respective fusion values (p<0.001). Mobile intact segments exhibited significantly greater rotation after fusion vs. their more rigid counterparts (p<0.05), however, intact motion was not related to motion after IPD reconstruction. The NZ and rotational stiffness followed similar trends. Differences in NZ between mobile and rigid intact specimens tended to decrease in the IPD reconstructed state. Conclusion The annulus sparing IPD generally reproduced the intact segment biomechanics in terms of ROM, NZ, and stiffness. Furthermore, the IPD reconstructed discs imparted stability by maintaining a small neutral zone. The IPD reconstructed discs were significantly less rigid than the fusion constructs and may be an attractive alternative for the treatment of DDD. PMID:19540816

Are PEEK-on-Ceramic Bearings an Option for Total Disc Arthroplasty? An In Vitro Tribology Study.

PubMed

Siskey, Ryan; Ciccarelli, Lauren; Lui, Melissa K C; Kurtz, Steven M

2016-11-01

Most contemporary total disc replacements (TDRs) use conventional orthopaedic bearing couples such as ultrahigh-molecular-weight polyethylene (polyethylene) and cobalt-chromium (CoCr). Cervical total disc replacements incorporating polyetheretherketone (PEEK) bearings (specifically PEEK-on-PEEK bearings) have been previously investigated, but little is known about PEEK-on-ceramic bearings for TDR. (1) What is the tribologic behavior of a PEEK-on-ceramic bearing for cervical TDR under idealized, clean wear test conditions? (2) How does the PEEK-on-ceramic design perform under impingement conditions? (3) How is the PEEK-on-ceramic bearing affected by abrasive wear? (4) Is the particle morphology from PEEK-on-ceramic bearings for TDRs affected by adverse wear scenarios? PEEK-on-ceramic cervical TDR bearings were subjected to a 10 million cycle ideal wear test based on ASTM F2423 and ISO 181912-1 using a six-station spine wear simulator (MTS, Eden Prairie, MN, USA) with 5 g/L bovine serum concentration at 23° ± 2° C (ambient temperature). Validated 1 million cycle impingement and 5 million cycle abrasive tests were conducted on the PEEK-on-ceramic bearings based, in part, on retrieval analysis of a comparable bearing design as well as finite element analyses. The ceramic-on-PEEK couple was characterized for damage modes, mass and volume loss, and penetration and the lubricant was subjected to particle analysis. The resulting mass wear rate, volumetric wear rate, based on material density, and particle analysis were compared with clinically available cervical disc bearing couples. The three modes of wear (idealized, impingement, and abrasive) resulted in mean mass wear rates of 0.9 ± 0.2 mg/MC, 1.9 ± 0.5 mg/MC, and 2.8 ± 0.6 mg/MC, respectively. The mass wear rates were converted to volumetric wear rates using density and found to be 0.7 ± 0.1 mm 3 /MC, 1.5 ± 0.4 mm 3 /MC, and 2.1 ± 0.5 mm 3 /MC, respectively. During each test, the PEEK endplates were the primary sources of wear and demonstrated an abrasive wear mechanism. Under idealized and impingement conditions, the ceramic core also demonstrated slight polishing of the articulating surface but the change in mass was unmeasurable. During abrasive testing, the titanium transfer on the core was shown to polish over 5 MC of testing. In all cases and consistent with previous studies of other PEEK bearing couples, the particle size was primarily < 2 µm and morphology was smooth and spheroidal. Overall, the idealized PEEK-on-ceramic wear rate (0.7 ± 0.1 mm 3 /MC) appears comparable to the published wear rates for other polymer-on-hard bearing couples (0.3-6.7 mm 3 /MC) and within the range of 0.2 to 1.9 mm 3 /MC reported for PEEK-on-PEEK cervical disc designs. The particles, based on size and morphology, also suggest the wear mechanism is comparable between the PEEK-on-ceramic couple and other polymer-on-ceramic orthopaedic couples. The PEEK-on-ceramic bearing considered in this study is a novel bearing couple for use in total disc arthroplasty devices and will require clinical evaluation to fully assess the bearing couple and total disc design. However, the wear rates under idealized and adverse conditions, and particle size and morphology, suggest that PEEK-on-ceramic bearings may be a reasonable alternative to polyethylene-on-CoCr and metal-on-metal bearings currently used in cervical TDRs.

Biological treatment strategies for disc degeneration: potentials and shortcomings

PubMed Central

Nerlich, Andreas G.; Boos, Norbert

2006-01-01

Recent advances in molecular biology, cell biology and material sciences have opened a new emerging field of techniques for the treatment of musculoskeletal disorders. These new treatment modalities aim for biological repair of the affected tissues by introducing cell-based tissue replacements, genetic modifications of resident cells or a combination thereof. So far, these techniques have been successfully applied to various tissues such as bone and cartilage. However, application of these treatment modalities to cure intervertebral disc degeneration is in its very early stages and mostly limited to experimental studies in vitro or in animal studies. We will discuss the potential and possible shortcomings of current approaches to biologically cure disc degeneration by gene therapy or tissue engineering. Despite the increasing number of studies examining the therapeutic potential of biological treatment strategies, a practicable solution to routinely cure disc degeneration might not be available in the near future. However, knowledge gained from these attempts might be applied in a foreseeable future to cure the low back pain that often accompanies disc degeneration and therefore be beneficial for the patient. PMID:16983559

Comparison of animal discs used in disc research to human lumbar disc: torsion mechanics and collagen content.

PubMed

Showalter, Brent L; Beckstein, Jesse C; Martin, John T; Beattie, Elizabeth E; Espinoza Orías, Alejandro A; Schaer, Thomas P; Vresilovic, Edward J; Elliott, Dawn M

2012-07-01

Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these with the human disc. To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar discs, and cow, rat, and mouse caudal discs. Collagen content was measured and normalized by dry weight for the same discs except the rat and the mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human discs. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Disc torsion mechanics are comparable with human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented are useful for selecting and interpreting results for animal disc models. Structural organization of the fiber angle may explain the differences that were noted between species after geometric normalization.

Comparison of Animal Discs Used in Disc Research to Human Lumbar Disc: Torsion Mechanics and Collagen Content

PubMed Central

Showalter, Brent L.; Beckstein, Jesse C.; Martin, John T.; Beattie, Elizabeth E.; Orías, Alejandro A. Espinoza; Schaer, Thomas P.; Vresilovic, Edward J.; Elliott, Dawn M.

2012-01-01

Study Design Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these to the human disc. Objective To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. Summary of Background Data There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Methods Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar, and cow, rat, and mouse caudal. Collagen content was measured and normalized by dry weight for the same discs except the rat and mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Results Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Conclusion Disc torsion mechanics are comparable to human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented is useful for selecting and interpreting results for animal models of the disc. Structural composition of the disc, such as initial fiber angle, may explain the differences that were noted between species after geometric normalization. PMID:22333953

Dynamic Biomechanical Examination of the Lumbar Spine with Implanted Total Disc Replacement (TDR) Utilizing a Pendulum Testing System

PubMed Central

Daniels, Alan H; Paller, David J; Koruprolu, Sarath; McDonnell, Matthew; Palumbo, Mark A; Crisco, Joseph J

2013-01-01

Study Design Biomechanical cadaver investigation Objective To examine dynamic bending stiffness and energy absorption of the lumbar spine with and without implanted Total Disc Replacement (TDR) under simulated physiologic motion. Summary of background data The pendulum testing system is capable of applying physiologic compressive loads without constraining motion of functional spinal units (FSUs). The number of cycles to equilibrium observed under pendulum testing is a measure of the energy absorbed by the FSU. Methods Five unembalmed, frozen human lumbar FSUs were tested on the pendulum system with axial compressive loads of 181N, 282N, 385N, and 488N before and after Synthes ProDisc-L TDR implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5° resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and bending stiffness (N-m/°) was calculated and compared for each testing mode. Results In flexion/extension, the TDR constructs reached equilibrium with significantly (p<0.05) fewer cycles than the intact FSU with compressive loads of 282N, 385N and 488N. Mean dynamic bending stiffness in flexion, extension, and lateral bending increased significantly with increasing load for both the intact FSU and TDR constructs (p<0.001). In flexion, with increasing compressive loading from 181N to 488N, the bending stiffness of the intact FSUs increased from 4.0N-m/° to 5.5N-m/°, compared to 2.1N-m/° to 3.6N-m/° after TDR implantation. At each compressive load, the intact FSU was significantly more stiff than the TDR (p<0.05). Conclusion Lumbar FSUs with implanted TDR were found to be less stiff, but also absorbed more energy during cyclic loading with an unconstrained pendulum system. Although the effects on clinical performance of motion preserving devices are not fully known, these results provide further insight into the biomechanical behavior of this device under approximated physiologic loading conditions. PMID:22869057

The Formation and Fragmentation of Primordial Protostellar Discs

NASA Astrophysics Data System (ADS)

Clark, Paul C.; Glover, Simon C. O.; Smith, Rowan J.; Greif, Thomas H.; Klessen, Ralf S.; Bromm, Volker

2010-11-01

We study the formation and evolution of the protostellar discs that form around the first stars in the Universe. Using sink particles, we replace the gravitationally bound gas at densities higher than 1015 cm-3 and radii greater than 3 AU from the central protostellar core, with an accreting point mass that is able to gravitationally interact with the surrounding gas. We find the disc is gravitationally (or `Toomre') unstable, and is dominated by a strong m = 2 spiral mode. Although the angular momentum transport is dominated by a combination of gravitational torques and Reynolds stresses, which are extremely efficient mechanisms, the disc is unable to process the infalling material and grows increasingly gravitationally unstable. During the build-up of the disc, the temperature in the gas is regulated by a combination of H2 line cooling, collision-induced emission and H2 dissociation, which together help to offset heating from the gravitational collapse and feedback from the protostar. Once the disc starts to fragment, H2 dissociation keeps the gas almost isothermal as the collapse of the fragment progresses. The fragmentation occurs when the protostar/disc system is only 230 yr old and at a distance of ~20 AU from its sibling, by which point the central protostar has a mass of ~1 Msolar. Given the angular momentum of the new protostellar system, it is likely that the protostars will grow to become a massive binary system.

Geometry of the intervertebral volume and vertebral endplates of the human spine.

PubMed

van der Houwen, E B; Baron, P; Veldhuizen, A G; Burgerhof, J G M; van Ooijen, P M A; Verkerke, G J

2010-01-01

Replacement of a degenerated vertebral disc with an artificial intervertebral disc (AID) is currently possible, but poses problems, mainly in the force distribution through the vertebral column. Data on the intervertebral disc space geometry will provide a better fit of the prosthesis to the vertebrae, but current literature on vertebral disc geometry is very scarce or not suitable. In this study, existing CT-scans of 77 patients were analyzed to measure the intervertebral disc and vertebral endplate geometry of the lumbar spine. Ten adjacent points on both sides of the vertebrae (S1-superior to T12-inferior) and sagittal and transverse diameters were measured to describe the shape of the caudal and cranial vertebral planes of the vertebrae. It was found that the largest endplate depth is located in the middle or posterior regions of the vertebra, that there is a linear relationship between all inferior endplate depths and the endplate location (p < 0.0001) within the spinal column, and that the superior endplate depth increases with age by about 0.01 mm per year (p < 0.02). The wedge angle increases from T12-L1 to L5-S1. The results allow for improvement of the fit of intervertebral disc-prostheses to the vertebrae and optimized force transmission through the vertebral column.

Are periprosthetic tissue reactions observed after revision of total disc replacement comparable to the reactions observed after total hip or knee revision surgery?

PubMed Central

Punt, Ilona M.; Austen, Shennah; Cleutjens, Jack P.M.; Kurtz, Steven M.; ten Broeke, René H.M.; van Rhijn, Lodewijk W.; Willems, Paul C.; van Ooij, André

2011-01-01

Study design Comparative study. Objective To compare periprosthetic tissue reactions observed after total disc replacement (TDR), total hip arthroplasty (THA) and total knee arthroplasty (TKA) revision surgery. Summary of background data Prosthetic wear debris leading to particle disease, followed by osteolysis, is often observed after THA and TKA. Although the presence of polyethylene (PE) particles and periprosthetic inflammation after TDR has been proven recently, osteolysis is rarely observed. The clinical relevance of PE wear debris in the spine remains poorly understood. Methods Number, size and shape of PE particles, as well as quantity and type of inflammatory cells in periprosthetic tissue retrieved during Charité TDR (n=22), THA (n=10) and TKA (n=4) revision surgery were compared. Tissue samples were stained with hematoxylin/eosin and examined by using light microscopy with bright field and polarized light. Results After THA, large numbers of PE particles <6 µm were observed, which were mainly phagocytosed by macrophages. The TKA group had a broad size range with many larger PE particles and more giant cells. In TDR, the size range was similar to that observed in TKA. However, the smallest particles were the most prevalent with 75% of the particles being <6 µm, as seen in revision THA. In TDR, both macrophages and giant cells were present with a higher number of macrophages. Conclusions Both small and large PE particles are present after TDR revision surgery compatible with both THA and TKA wear patterns. The similarities between periprosthetic tissue reactions in the different groups may give more insight in the clinical relevance of PE particles and inflammatory cells in the lumbar spine. The current findings may help to improve TDR design as applied from technologies previously developed in THA and TKA with the goal of a longer survival of TDR. PMID:21336235

Cervical artificial disc extrusion after a paragliding accident

PubMed Central

Niu, Tianyi; Hoffman, Haydn; Lu, Daniel C.

2017-01-01

Background: Cervical total disc replacement (TDR) is an established alternative to anterior cervical discectomy and fusion (ACDF) with excellent long-term outcomes and low failure rates. Cases of implant failure and migration are scarce and primarily limited to several years postoperatively. The authors report a case of anterior extrusion of a C4-C5 ProDisc-C (DePuy Synthes, West Chester, PA, USA) cervical artificial disc (CAD) 14 months after placement due to minor trauma. Case Description: A 33-year-old female who had undergone C4-C5 CAD implantation presented with neck pain and spasm after experiencing a paragliding accident. A 4 mm anterior protrusion of the CAD was seen on x-ray. She underwent removal of the CAD followed by anterior fusion. Other cases of CAD extrusion in the literature are discussed and the device's durability and testing are considered. Conclusion: Overall, CAD extrusion is a rare event. This case is likely the result of insufficient osseous integration. Patients undergoing cervical TDR should avoid high-risk activities to prevent trauma that could compromise the disc's placement, and future design/research should focus on how to enhance osseous integration at the interface while minimizing excessive heterotopic ossification. PMID:28781915

Cervical artificial disc extrusion after a paragliding accident.

PubMed

Niu, Tianyi; Hoffman, Haydn; Lu, Daniel C

2017-01-01

Cervical total disc replacement (TDR) is an established alternative to anterior cervical discectomy and fusion (ACDF) with excellent long-term outcomes and low failure rates. Cases of implant failure and migration are scarce and primarily limited to several years postoperatively. The authors report a case of anterior extrusion of a C4-C5 ProDisc-C (DePuy Synthes, West Chester, PA, USA) cervical artificial disc (CAD) 14 months after placement due to minor trauma. A 33-year-old female who had undergone C4-C5 CAD implantation presented with neck pain and spasm after experiencing a paragliding accident. A 4 mm anterior protrusion of the CAD was seen on x-ray. She underwent removal of the CAD followed by anterior fusion. Other cases of CAD extrusion in the literature are discussed and the device's durability and testing are considered. Overall, CAD extrusion is a rare event. This case is likely the result of insufficient osseous integration. Patients undergoing cervical TDR should avoid high-risk activities to prevent trauma that could compromise the disc's placement, and future design/research should focus on how to enhance osseous integration at the interface while minimizing excessive heterotopic ossification.

Cervical anterior hybrid technique with bi-level Bryan artificial disc replacement and adjacent segment fusion for cervical myelopathy over three consecutive segments.

PubMed

Chen, Jiang; Xu, Lin; Jia, Yu-Song; Sun, Qi; Li, Jin-Yu; Zheng, Chen-Ying; Bai, Chun-Xiao; Yu, Qin-Sheng

2016-05-01

This study aimed to assess the preliminary clinical efficacy and feasibility of the hybrid technique for multilevel cervical myelopathy. Considering the many shortcomings of traditional treatment methods for multilevel cervical degenerative myelopathy, hybrid surgery (bi-level Bryan artificial disc [Medtronic Sofamor Danek, Memphis, TN, USA] replacement and anterior cervical discectomy and fusion) should be considered. Between March 2006 and November 2012, 108 patients (68 men and 40 women, average age 45years) underwent hybrid surgery. Based on the Japanese Orthopaedic Association (JOA) score, Neck Disability Index (NDI), and Odom's criteria, the clinical symptoms and neurological function before and after surgery were evaluated. Mean surgery duration was 90minutes, with average blood loss of 30mL. Mean follow-up duration was 36months. At the final follow-up, the mean JOA (± standard deviation) scores were significantly higher compared with preoperative values (15.08±1.47 versus 9.18±1.22; P<0.01); meanwhile, NDI values were markedly decreased (12.32±1.03 versus 42.68±1.83; P<0.01). Using Odom's criteria, the clinical outcomes were rated as excellent (76 patients), good (22 patients), fair (six patients), and poor (four patients). These findings indicate that the hybrid method provides an effective treatment for cervical myelopathy over three consecutive segments, ensuring a good clinical outcome. Copyright © 2015 Elsevier Ltd. All rights reserved.

Anterior surgical management of single-level cervical disc disease: a cost-effectiveness analysis.

PubMed

Lewis, Daniel J; Attiah, Mark A; Malhotra, Neil R; Burnett, Mark G; Stein, Sherman C

2014-12-01

Cost-effectiveness analysis with decision analysis and meta-analysis. To determine the relative cost-effectiveness of anterior cervical discectomy with fusion (with autograft, allograft, or spacers), anterior cervical discectomy without fusion (ACD), and cervical disc replacement (CDR) for the treatment of 1-level cervical disc disease. There is debate as to the optimal anterior surgical strategy to treat single-level cervical disc disease. Surgical strategies include 3 techniques of anterior cervical discectomy with fusion (autograft, allograft, or spacer-assisted fusion), ACD, and CDR. Several controlled trials have compared these treatments but have yielded mixed results. Decision analysis provides a structure for making a quantitative comparison of the costs and outcomes of each treatment. A literature search was performed and yielded 156 case series that fulfilled our search criteria describing nearly 17,000 cases. Data were abstracted from these publications and pooled meta-analytically to estimate the incidence of various outcomes, including index-level and adjacent-level reoperation. A decision analytic model calculated the expected costs in US dollars and outcomes in quality-adjusted life years for a typical adult patient with 1-level cervical radiculopathy subjected to each of the 5 approaches. At 5 years postoperatively, patients who had undergone ACD alone had significantly (P < 0.001) more quality-adjusted life years (4.885 ± 0.041) than those receiving other treatments. Patients with ACD also exhibited highly significant (P < 0.001) differences in costs, incurring the lowest societal costs ($16,558 ± $539). Follow-up data were inadequate for comparison beyond 5 years. The results of our decision analytic model indicate advantages for ACD, both in effectiveness and costs, over other strategies. Thus, ACD is a cost-effective alternative to anterior cervical discectomy with fusion and CDR in patients with single-level cervical disc disease. Definitive conclusions about degenerative changes after ACD and adjacent-level disease after CDR await longer follow-up. 4.

Preferential superior surface motion in wear simulations of the Charité total disc replacement.

PubMed

Goreham-Voss, Curtis M; Vicars, Rachel; Hall, Richard M; Brown, Thomas D

2012-06-01

Laboratory wear simulations of the dual-bearing surface Charité total disc replacement (TDR) are complicated by the non-specificity of the device's center of rotation (CoR). Previous studies have suggested that articulation of the Charité preferentially occurs at the superior-bearing surface, although it is not clear how sensitive this phenomenon is to lubrication conditions or CoR location. In this study, a computational wear model is used to study the articulation kinematics and wear of the Charité TDR. Implant wear was found to be insensitive to the CoR location, although seemingly non-physiologic endplate motion can result. Articulation and wear were biased significantly to the superior-bearing surface, even in the presence of significant perturbations of loading and friction. The computational wear model provides novel insight into the mechanics and wear of the Charité TDR, allowing for better interpretation of in vivo results, and giving useful insight for designing future laboratory physical tests.

[Minor strut fracture of the Björk-Shiley mitral valve].

PubMed

Sugita, T; Yasuda, R; Watarida, S; Onoe, M; Tabata, R; Mori, A

1990-06-01

In May, 1982, a 49-year-old man underwent mitral valve replacement (MVR) in our hospital with a 31 mm Björk-Shiley prosthesis for mitral regurgitation. He had been doing well until his episode of palpitation and dyspnea of sudden onset, and was transferred to our ICU with severe cardiogenic shock in Aug, 1986. Chest X-ray film revealed pulmonary edema and breakage of the valve with migration of the disc and the minor strut of the prosthesis. He was operated upon 5 hours after the onset of his complaints. The minor strut was removed from the left upper pulmonary vein and mitral valve re-replacement was done with a 29 mm Björk-Shiley Monostrut valve. The disc which had dislocated into the abdominal aorta was also recovered on the twenty-third post operative day. His postoperative course was uneventful. Immediate diagnosis and subsequent re-operation is absolute indication for rescue from acute cardiac failure due to mechanical failure of any prosthetic valve.

Parametric modeling of the intervertebral disc space in 3D: application to CT images of the lumbar spine.

PubMed

Korez, Robert; Likar, Boštjan; Pernuš, Franjo; Vrtovec, Tomaž

2014-10-01

Gradual degeneration of intervertebral discs of the lumbar spine is one of the most common causes of low back pain. Although conservative treatment for low back pain may provide relief to most individuals, surgical intervention may be required for individuals with significant continuing symptoms, which is usually performed by replacing the degenerated intervertebral disc with an artificial implant. For designing implants with good bone contact and continuous force distribution, the morphology of the intervertebral disc space and vertebral body endplates is of considerable importance. In this study, we propose a method for parametric modeling of the intervertebral disc space in three dimensions (3D) and show its application to computed tomography (CT) images of the lumbar spine. The initial 3D model of the intervertebral disc space is generated according to the superquadric approach and therefore represented by a truncated elliptical cone, which is initialized by parameters obtained from 3D models of adjacent vertebral bodies. In an optimization procedure, the 3D model of the intervertebral disc space is incrementally deformed by adding parameters that provide a more detailed morphometric description of the observed shape, and aligned to the observed intervertebral disc space in the 3D image. By applying the proposed method to CT images of 20 lumbar spines, the shape and pose of each of the 100 intervertebral disc spaces were represented by a 3D parametric model. The resulting mean (±standard deviation) accuracy of modeling was 1.06±0.98mm in terms of radial Euclidean distance against manually defined ground truth points, with the corresponding success rate of 93% (i.e. 93 out of 100 intervertebral disc spaces were modeled successfully). As the resulting 3D models provide a description of the shape of intervertebral disc spaces in a complete parametric form, morphometric analysis was straightforwardly enabled and allowed the computation of the corresponding heights, widths and volumes, as well as of other geometric features that in detail describe the shape of intervertebral disc spaces. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cervical total disc replacement exhibits similar stiffness to intact cervical functional spinal units tested on a dynamic pendulum testing system.

PubMed

Esmende, Sean M; Daniels, Alan H; Paller, David J; Koruprolu, Sarath; Palumbo, Mark A; Crisco, Joseph J

2015-01-01

The pendulum testing system is capable of applying physiologic compressive loads without constraining the motion of functional spinal units (FSUs). The number of cycles to equilibrium observed under pendulum testing is a measure of the energy absorbed by the FSU. To examine the dynamic bending stiffness and energy absorption of the cervical spine, with and without implanted cervical total disc replacement (TDR) under simulated physiologic motion. A biomechanical cadaver investigation. Nine unembalmed, frozen human cervical FSUs from levels C3-C4 and C5-C6 were tested on the pendulum system with axial compressive loads of 25, 50, and 100 N before and after TDR implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5°, resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and the bending stiffness (Newton-meter/°) was calculated and compared for each testing mode. In flexion/extension, with increasing compressive loading from 25 to 100 N, the average number of cycles to equilibrium for the intact FSUs increased from 6.6 to 19.1, compared with 4.1 to 12.7 after TDR implantation (p<.05 for loads of 50 and 100 N). In flexion, with increasing compressive loading from 25 to 100 N, the bending stiffness of the intact FSUs increased from 0.27 to 0.59 Nm/°, compared with 0.21 to 0.57 Nm/° after TDR implantation. No significant differences were found in stiffness between the intact FSU and the TDR in flexion/extension and lateral bending at any load (p<.05). Cervical FSUs with implanted TDR were found to have similar stiffness, but had greater energy absorption than intact FSUs during cyclic loading with an unconstrained pendulum system. These results provide further insight into the biomechanical behavior of cervical TDR under approximated physiologic loading conditions. Copyright © 2015 Elsevier Inc. All rights reserved.

Automated volumetric evaluation of stereoscopic disc photography

PubMed Central

Xu, Juan; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A; Kagemann, Larry; Craig, Jamie E; Mackey, David A; Hewitt, Alex W; Schuman, Joel S

2010-01-01

PURPOSE: To develop a fully automated algorithm (AP) to perform a volumetric measure of the optic disc using conventional stereoscopic optic nerve head (ONH) photographs, and to compare algorithm-produced parameters with manual photogrammetry (MP), scanning laser ophthalmoscope (SLO) and optical coherence tomography (OCT) measurements. METHODS: One hundred twenty-two stereoscopic optic disc photographs (61 subjects) were analyzed. Disc area, rim area, cup area, cup/disc area ratio, vertical cup/disc ratio, rim volume and cup volume were automatically computed by the algorithm. Latent variable measurement error models were used to assess measurement reproducibility for the four techniques. RESULTS: AP had better reproducibility for disc area and cup volume and worse reproducibility for cup/disc area ratio and vertical cup/disc ratio, when the measurements were compared to the MP, SLO and OCT methods. CONCLUSION: AP provides a useful technique for an objective quantitative assessment of 3D ONH structures. PMID:20588996

Is the behavior of disc replacement adjacent to fusion affected by the location of the fused level in hybrid surgery?

PubMed

Wu, Ting-Kui; Meng, Yang; Wang, Bei-Yu; Hong, Ying; Rong, Xin; Ding, Chen; Chen, Hua; Liu, Hao

2018-04-27

Hybrid surgery (HS), consisting of cervical disc arthroplasty (CDA) at the mobile level, along with anterior cervical discectomy and fusion at the spondylotic level, could be a promising treatment for patients with multilevel cervical degenerative disc disease (DDD). An advantage of this technique is that it uses an optimal procedure according to the status of each level. However, information is lacking regarding the influence of the relative location of the replacement and the fusion segment in vivo. We conducted the present study to investigate whether the location of the fusion affected the behavior of the disc replacement and adjacent segments in HS in vivo. This is an observational study. The numbers of patients in the arthroplasty-fusion (AF) and fusion-arthroplasty (FA) groups were 51 and 24, respectively. The Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores were evaluated. Global and segmental lordosis, the range of motion (ROM) of C2-C7, and the operated and adjacent segments were measured. Fusion rate and radiological changes at adjacent levels were observed. Between January 2010 and July 2016, 75 patients with cervical DDD at two contiguous levels undergoing a two-level HS were retrospectively reviewed. The patients were divided into AF and FA groups according to the locations of the disc replacement. Clinical outcomes were evaluated according to the JOA, NDI, and VAS scores. Radiological parameters, including global and segmental lordosis, the ROM of C2-C7, the operated and adjacent segments, and complications, were also evaluated. Although the JOA, NDI, and VAS scores were improved in both the AF and the FA groups, no significant differences were found between the two groups at any follow-up point. Both groups maintained cervical lordosis, but no difference was found between the groups. Segmental lordosis at the fusion segment was significantly improved postoperatively (p<.001), whereas it was maintained at the arthroplasty segment. The ROM of C2-C7 was significantly decreased in both groups postoperatively (AF p=.001, FA p=.014), but no difference was found between the groups. The FA group exhibited a non-significant improvement in ROM at the arthroplasty segment. The ROM adjacent to the arthroplasty segment was increased, although not significantly, whereas the ROM adjacent to the fusion segment was significantly improved after surgery in both groups (p<.001). Fusion was achieved in all patients. No significant difference in complications was found between the groups. In HS, cephalic or caudal fusion segments to the arthroplasty segment did not affect the clinical outcomes and the behavior of CDA. However, the ROM of adjacent segments was affected by the location of the fusion segment; segments adjacent to fusion segments had greater ROMs than segments adjacent to arthroplasty segments. Copyright © 2018 Elsevier Inc. All rights reserved.

TTK Chitra tilting disc heart valve model TC2: An assessment of fatigue life and durability.

PubMed

Subhash, N N; Rajeev, Adathala; Sujesh, Sreedharan; Muraleedharan, C V

2017-08-01

Average age group of heart valve replacement in India and most of the Third World countries is below 30 years. Hence, the valve for such patients need to be designed to have a service life of 50 years or more which corresponds to 2000 million cycles of operation. The purpose of this study was to assess the structural performance of the TTK Chitra tilting disc heart valve model TC2 and thereby address its durability. The TC2 model tilting disc heart valves were assessed to evaluate the risks connected with potential structural failure modes. To be more specific, the studies covered the finite element analysis-based fatigue life prediction and accelerated durability testing of the tilting disc heart valves for nine different valve sizes. First, finite element analysis-based fatigue life prediction showed that all nine valve sizes were in the infinite life region. Second, accelerated durability test showed that all nine valve sizes remained functional for 400 million cycles under experimental conditions. The study ensures the continued function of TC2 model tilting disc heart valves over duration in excess of 50 years. The results imply that the TC2 model valve designs are structurally safe, reliable and durable.

In vitro-analysis of kinematics and intradiscal pressures in cervical arthroplasty versus fusion--A biomechanical study in a sheep model with two semi-constrained prosthesis.

PubMed

Daentzer, Dorothea; Welke, Bastian; Hurschler, Christof; Husmann, Nathalie; Jansen, Christina; Flamme, Christian Heinrich; Richter, Berna Ida

2015-03-24

As an alternative technique to arthrodesis of the cervical spine, total disc replacement (TDR) has increasingly been used with the aim of restoration of the physiological function of the treated and adjacent motions segments. The purpose of this experimental study was to analyze the kinematics of the target level as well as of the adjacent segments, and to measure the pressures in the proximal and distal disc after arthrodesis as well as after arthroplasty with two different semi-constrained types of prosthesis. Twelve cadaveric ovine cervical spines underwent polysegmental (C2-5) multidirectional flexibility testing with a sensor-guided industrial serial robot. Additionally, pressures were recorded in the proximal and distal disc. The following three conditions were tested: (1) intact specimen, (2) single-level arthrodesis C3/4, (3) single-level TDR C3/4 using the Discover® in the first six specimens and the activ® C in the other six cadavers. Statistical analysis was performed for the total range of motion (ROM), the intervertebral ROM (iROM) and the intradiscal pressures (IDP) to compare both the three different conditions as well as the two disc prosthesis among each other. The relative iROM in the target level was always lowered after fusion in the three directions of motion. In almost all cases, the relative iROM of the adjacent segments was almost always higher compared to the physiologic condition. After arthroplasty, we found increased relative iROM in the treated level in comparison to intact state in almost all cases, with relative iROM in the adjacent segments observed to be lower in almost all situations. The IDP in both adjacent discs always increased in flexion and extension after arthrodesis. In all but five cases, the IDP in each of the adjacent level was decreased below the values of the intact specimens after TDR. Overall, in none of the analyzed parameters were statistically significantly differences between both types of prostheses investigated. The results of this biomechanical study indicate that single-level implantation of semi-constrained TDR lead to a certain hypermobility in the treated segments with lowering the ROM in the adjacent levels in almost all situations.

Does T2 mapping of the posterior annulus fibrosus indicate the presence of lumbar intervertebral disc herniation? A 3.0 Tesla magnetic resonance study.

PubMed

Messner, Alina; Stelzeneder, David; Trattnig, Stefan; Welsch, Götz H; Schinhan, Martina; Apprich, Sebastian; Brix, Martin; Windhager, Reinhard; Trattnig, Siegfried

2017-03-01

Indicating lumbar disc herniation via magnetic resonance imaging (MRI) T2 mapping in the posterior annulus fibrosus (AF). Sagittal T2 maps of 313 lumbar discs of 64 patients with low back pain were acquired at 3.0 Tesla (3T). The discs were rated according to disc herniation and bulging. Region of interest (ROI) analysis was performed on median, sagittal T2 maps. T2 values of the AF, in the most posterior 10% (PAF-10) and 20% of the disc (PAF-20), were compared. A significant increase in the T2 values of discs with herniations affecting the imaged area, compared to bulging discs and discs with lateral herniation, was shown in the PAF-10, where no association to the NP was apparent. The PAF-20 exhibited a moderate correlation to the nucleus pulposus (NP). High T2 values in the PAF-10 suggest the presence of disc herniation (DH). The results indicate that T2 values in the PAF-20 correspond more to changes in the NP.

Protoplanetary disc `isochrones' and the evolution of discs in the M˙-Md plane

NASA Astrophysics Data System (ADS)

Lodato, Giuseppe; Scardoni, Chiara E.; Manara, Carlo F.; Testi, Leonardo

2017-12-01

In this paper, we compare simple viscous diffusion models for the disc evolution with the results of recent surveys of the properties of young protoplanetary discs. We introduce the useful concept of 'disc isochrones' in the accretion rate-disc mass plane and explore a set of Monte Carlo realization of disc initial conditions. We find that such simple viscous models can provide a remarkable agreement with the available data in the Lupus star forming region, with the key requirement that the average viscous evolutionary time-scale of the discs is comparable to the cluster age. Our models produce naturally a correlation between mass accretion rate and disc mass that is shallower than linear, contrary to previous results and in agreement with observations. We also predict that a linear correlation, with a tighter scatter, should be found for more evolved disc populations. Finally, we find that such viscous models can reproduce the observations in the Lupus region only in the assumption that the efficiency of angular momentum transport is a growing function of radius, thus putting interesting constraints on the nature of the microscopic processes that lead to disc accretion.

Understanding United States Investigational Device Exemption Studies-Clinical Relevance and Importance for Healthcare Economics.

PubMed

Ament, Jared D; Mollan, Scott; Greenan, Krista; Binyamin, Tamar; Kim, Kee D

2017-06-01

The US Food and Drug Administration allows a previously unapproved device to be used clinically to collect safety and effectiveness data under their Investigational Device Exemption (IDE) category. The process usually falls under 3 different trial categories: noninferiority, equivalency, and superiority. To confidently inform our patients, understanding the basic concepts of these trials is paramount. The purpose of this manuscript was to provide a comprehensive review of these topics using recently published IDE trials and economic analyses of cervical total disc replacement as illustrative examples. In 2006, an IDE was initiated to study the safety and effectiveness of total disc replacement controlled against the standard of care, anterior cervical discectomy, and fusion. Under the IDE, randomized controlled trials comparing both 1 and 2 level cervical disease were completed. The sponsor designed the initial trial as noninferiority; however, using adaptive methodology, superiority could be claimed in the 2-level investigation. Healthcare economics are critical in medical decision making and reimbursement practices. Once both cost- and quality-adjusted life-year (QALY) are known for each patient, the incremental cost-effectiveness ratio is calculated. Willingness-to-pay is controversial, but a commonly cited guideline considers interventions costing below 20 000 $/QALY strongly cost effective and more than 100 000 $/QALY as not cost effective. While large Food and Drug Administration IDE studies are often besieged by complex statistical considerations and calculations, it is fundamentally important that clinicians understand at least the terminology and basic concepts on a practical level. Copyright © 2017 by the Congress of Neurological Surgeons

Biologic canine and human intervertebral disc repair by notochordal cell-derived matrix: from bench towards bedside.

PubMed

Bach, Frances C; Tellegen, Anna R; Beukers, Martijn; Miranda-Bedate, Alberto; Teunissen, Michelle; de Jong, Willem A M; de Vries, Stefan A H; Creemers, Laura B; Benz, Karin; Meij, Björn P; Ito, Keita; Tryfonidou, Marianna A

2018-05-29

The socioeconomic burden of chronic back pain related to intervertebral disc (IVD) disease is high and current treatments are only symptomatic. Minimally invasive strategies that promote biological IVD repair should address this unmet need. Notochordal cells (NCs) are replaced by chondrocyte-like cells (CLCs) during IVD maturation and degeneration. The regenerative potential of NC-secreted substances on CLCs and mesenchymal stromal cells (MSCs) has already been demonstrated. However, identification of these substances remains elusive. Innovatively, this study exploits the regenerative NC potential by using healthy porcine NC-derived matrix (NCM) and employs the dog as a clinically relevant translational model. NCM increased the glycosaminoglycan and DNA content of human and canine CLC aggregates and facilitated chondrogenic differentiation of canine MSCs in vitro . Based on these results, NCM, MSCs and NCM+MSCs were injected in mildly (spontaneously) and moderately (induced) degenerated canine IVDs in vivo and, after six months of treatment, were analyzed. NCM injected in moderately (induced) degenerated canine IVDs exerted beneficial effects at the macroscopic and MRI level, induced collagen type II-rich extracellular matrix production, improved the disc height, and ameliorated local inflammation. MSCs exerted no (additive) effects. In conclusion, NCM induced in vivo regenerative effects on degenerated canine IVDs. NCM may, comparable to demineralized bone matrix in bone regeneration, serve as 'instructive matrix', by locally releasing growth factors and facilitating tissue repair. Therefore, intradiscal NCM injection could be a promising regenerative treatment for IVD disease, circumventing the cumbersome identification of bioactive NC-secreted substances.

The relationship between quantitative measures of disc height and disc signal intensity with Pfirrmann score of disc degeneration.

PubMed

Salamat, Sara; Hutchings, John; Kwong, Clemens; Magnussen, John; Hancock, Mark J

2016-01-01

To assess the relationship between quantitative measures of disc height and signal intensity with the Pfirrmann disc degeneration scoring system and to test the inter-rater reliability of the quantitative measures. Participants were 76 people who had recently recovered from their last episode of acute low back pain and underwent MRI scan on a single 3T machine. At all 380 lumbar discs, quantitative measures of disc height and signal intensity were made by 2 independent raters and compared to Pfirrmann scores from a single radiologist. For quantitative measures of disc height and signal intensity a "raw" score and 2 adjusted ratios were calculated and the relationship with Pfirrmann scores was assessed. The inter-tester reliability of quantitative measures was also investigated. There was a strong linear relationship between quantitative disc signal intensity and Pfirrmann scores for grades 1-4, but not for grades 4 and 5. For disc height only, Pfirrmann grade 5 had significantly reduced disc height compared to all other grades. Results were similar regardless of whether raw or adjusted scores were used. Inter-rater reliability for the quantitative measures was excellent (ICC > 0.97). Quantitative measures of disc signal intensity were strongly related to Pfirrmann scores from grade 1 to 4; however disc height only differentiated between grade 4 and 5 Pfirrmann scores. Using adjusted ratios for quantitative measures of disc height or signal intensity did not significantly alter the relationship with Pfirrmann scores.

Morphological Features and Important Parameters of Large Optic Discs for Diagnosing Glaucoma

PubMed Central

Okimoto, Satoshi; Yamashita, Keiko; Shibata, Tetsuo; Kiuchi, Yoshiaki

2015-01-01

Purpose To compare the optic disc parameters of glaucomatous eyes to those of non-glaucomatous eyes with large discs. Methods We studied 225 consecutive eyes with large optic discs (>2.82 mm2): 91 eyes with glaucoma and 134 eyes without glaucoma. An eye was diagnosed with glaucoma when visual field defects were detected by the Humphrey Field Analyzer. All of the Heidelberg Retina Tomograph II (HRT II) parameters were compared between the non-glaucomatous and glaucomatous eyes. A logistic regression analysis of the HRT II parameters was used to establish a new formula for diagnosing glaucoma, and the sensitivity and specificity of the Moorfields Regression Analysis (MRA) was compared to the findings made by our analyses. Results The mean disc area was 3.44±0.50 mm2 in the non-glaucomatous group and 3.40±0.52 mm2 in the glaucoma group. The cup area, cup volume, cup-to-disc area ratio, linear cup/disc ratio, mean cup depth, and the maximum cup depth were significantly larger in glaucomatous eyes than in the non-glaucomatous eyes. The rim area, rim volume, cup shape measurement, mean retinal nerve fiber layer (RNFL) thickness, and RFNL cross-sectional area were significantly smaller in glaucomatous eyes than in non-glaucomatous eyes. The cup-to-disc area ratio, the height variation contour (HVC), and the RNFL cross-sectional area were important parameters for diagnosing the early stage glaucoma, and the cup-to-disc area ratio and cup volume were useful for diagnosing advanced stage glaucoma in eyes with a large optic disc. The new formula had higher sensitivity and specificity for diagnosing glaucoma than MRA. Conclusions The cup-to-disc area ratio, HVC, RNFL cross-sectional area, and cup volume were important parameters for diagnosing glaucoma in eyes with a large optic disc. The important disc parameters to diagnose glaucoma depend on the stage of glaucoma in patients with large discs. PMID:25798580

Comparison of optic disc topography in non-glaucomatous eyes of children with juvenile diabetes mellitus and normal children.

PubMed

Elgin, Ufuk; Cankaya, Bülent; Simsek, Tulay; Batman, Aygen

2010-01-01

To compare the optic disc topography parameters of children with juvenile diabetes mellitus and normal children using the Heidelberg Retinal Tomograph (HRT III) (Heidelberg Engineering, Heidelberg, Germany). The topographic optic disc parameters (cup volume, cup area, rim volume, rim area, disc area, mean cup-to-disc ratio, and mean cup depth) of 28 non-glaucomatous eyes of 28 children with type 1 diabetes mellitus and 28 eyes of 28 age-matched healthy children were compared using the nonparametric Mann-Whitney U test. No statistically significant differences were found between cup volume (P = .782), cup area (P = .878), rim volume (P = .853), disc area (P = .452), mean cup-to-disc ratio (P = .852), and mean cup depth (P = .711) of eyes of cases with diabetes mellitus and normal subjects. This result suggests that non-glaucomatous eyes of children with type 1 diabetes mellitus and healthy subjects have similar topographic optic disc characteristics. Copyright 2010, SLACK Incorporated.

Quantitating Human Optic Disc Topography

NASA Astrophysics Data System (ADS)

Graebel, William P.; Cohan, Bruce E.; Pearch, Andrew C.

1980-07-01

A method is presented for quantitatively expressing the topography of the human optic disc, applicable in a clinical setting to the diagnosis and management of glaucoma. Pho-tographs of the disc illuminated by a pattern of fine, high contrast parallel lines are digitized. From the measured deviation of the lines as they traverse the disc surface, disc topography is calculated, using the principles of optical sectioning. The quantitators applied to express this topography have the the following advantages : sensitivity to disc shape; objectivity; going beyond the limits of cup-disc ratio estimates and volume calculations; perfect generality in a mathematical sense; an inherent scheme for determining a non-subjective reference frame to compare different discs or the same disc over time.

Clinical Evaluation and Magnetic Resonance Imaging Assessment of Intradiscal Methylene Blue Injection for the Treatment of Discogenic Low Back Pain.

PubMed

Zhang, XiaoJun; Hao, Jie; Hu, Zhenming; Yang, HaiTao

2016-01-01

Low back pain is a common worldwide health problem and has a significant socioeconomic impact on public health. Internal disc disruption has been considered as the most common cause of low back pain. Various therapies, including interbody fusion, disc replacement, injection therapies, and thermal annular procedures have been utilized for the treatment of discogenic low back pain. Recently, a new method of intradiscal methylene blue injection has been introduced to treat discogenic low back pain, but the clinical outcomes are controversial. To investigate the clinical outcomes and magnetic resonance imaging changes of intradiscal methylene blue injection for the treatment of discogenic low back pain. Observational study. An interventional low back pain management practice in a university hospital. A total of 33 patients were selected to be treated with intradiscal methylene blue injection. The clinical outcomes were evaluated by numeric rating scale and Oswestry Disability Index at pretreatment, one month, 3, 6, and 12 months after treatment. The magnetic resonance imaging changes of involved intervertebral discs were assessed by apparent diffusion coefficient and T2 values at pretreatment, 3, 6, and 12 months after treatment. All of the patients got a follow-up period up to 12 months. The mean numeric rating scale scores at pretreatment, one month, 3, 6, and 12 months after treatment were 6.54, 2.98, 3.23, 3.66, and 4.72, respectively. There was a minimum of 2 points reduction at one month, 3, and 6 months after treatment, but less than 2 points reduction at 12 months. There was at least 50% improvement on the Oswestry Disability Index at one month, 3, and 6 months after treatment, but not at 12 months. The mean apparent diffusion coefficient and T2 value were significantly higher at 6 and12 months after treatment compared to pretreatment, but there was no significant difference between pretreatment and 3 months after treatment. This is an observational study with a relatively small sample size and short-term follow-up. The intradiscal methylene blue injection might be an effective therapy for discogenic low back pain for the short-term and could improve disc degeneration condition to some extent.Key words: Low back pain, discogenic pain, internal disc disruption, provocation discography, methylene blue, intradiscal injection, disc degeneration, magnetic resonance, imaging.

Low rate loading-induced convection enhances net transport into the intervertebral disc in vivo.

PubMed

Gullbrand, Sarah E; Peterson, Joshua; Mastropolo, Rosemarie; Roberts, Timothy T; Lawrence, James P; Glennon, Joseph C; DiRisio, Darryl J; Ledet, Eric H

2015-05-01

The intervertebral disc primarily relies on trans-endplate diffusion for the uptake of nutrients and the clearance of byproducts. In degenerative discs, diffusion is often diminished by endplate sclerosis and reduced proteoglycan content. Mechanical loading-induced convection has the potential to augment diffusion and enhance net transport into the disc. The ability of convection to augment disc transport is controversial and has not been demonstrated in vivo. To determine if loading-induced convection can enhance small molecule transport into the intervertebral disc in vivo. Net transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to in vivo cyclic low rate loading. Animals were administered the MRI contrast agent gadodiamide intravenously and subjected to in vivo low rate loading (0.5 Hz, 200 N) via a custom external loading apparatus for either 2.5, 5, 10, 15, or 20 minutes. Animals were then euthanized and the lumbar spines imaged using postcontrast enhanced MRI. The T1 constants in the nucleus, annulus, and cartilage endplates were quantified as a measure of gadodiamide transport into the loaded discs compared with the adjacent unloaded discs. Microcomputed tomography was used to quantify subchondral bone density. Low rate loading caused the rapid uptake and clearance of gadodiamide in the nucleus compared with unloaded discs, which exhibited a slower rate of uptake. Relative to unloaded discs, low rate loading caused a maximum increase in transport into the nucleus of 16.8% after 5 minutes of loading. Low rate loading increased the concentration of gadodiamide in the cartilage endplates at each time point compared with unloaded levels. Results from this study indicate that forced convection accelerated small molecule uptake and clearance in the disc induced by low rate mechanical loading. Low rate loading may, therefore, be therapeutic to the disc as it may enhance the nutrient uptake and waste product clearance. Copyright © 2015 Elsevier Inc. All rights reserved.

Clinical and radiographic analysis of an artificial cervical disc: 7-year follow-up from the Prestige prospective randomized controlled clinical trial: Clinical article.

PubMed

Burkus, J Kenneth; Traynelis, Vincent C; Haid, Regis W; Mummaneni, Praveen V

2014-10-01

The authors assess the long-term safety and efficacy of cervical disc replacement with the Prestige Cervical Disc in a prospective, randomized, multicenter trial at 7 years of follow-up. At 31 investigational sites, 541 patients with single-level cervical disc disease with radiculopathy were randomized to 1 of 2 treatment groups: 276 investigational group patients underwent anterior cervical discectomy and arthroplasty with the Prestige disc, and 265 control group patients underwent anterior cervical discectomy and fusion. Clinical outcomes included Neck Disability Index, the 36-Item Short-Form Health Survey, and neck and arm pain scores. Radiographs were assessed for angle of motion and fusion. Clinical and radiographic outcomes were evaluated preoperatively, intraoperatively, and at 1.5, 3, 6, 12, 24, 36, 60, and 84 months. Of the 541 patients treated, 395 patients (73%; 212 investigational and 183 control patients) completed 7 years of clinical follow-up. Significant improvements achieved by 1.5 months in both groups were sustained at 7 years. In the investigational group, mean Neck Disability Index improvements from preoperative scores were 38.2 and 37.5 at 60 and 84 months, respectively. In the control group, the corresponding means were 33.8 and 31.9. The differences between the investigational and control groups at the 60-month and 84-month periods were significant (p = 0.014 and 0.002, respectively). The overall rates of maintenance or improvement in neurological status in the investigational group were significantly higher: 92.2% and 88.2% at 60 months and 84 months, respectively, compared with 85.7% and 79.7% in the control group (p = 0.017 and 0.011, respectively). At 84 months, the percentage of working patients in the investigational group was 73.9%, and in the control group, 73.1%. Postoperatively, the implant effectively maintained average angular motion of 6.67° at 60 months and 6.75° at 84 months. Cumulative rates for surgery at the index level were lower (p < 0.001) in the investigational group (11 [4.8%] of 276) when compared with the control group (29 [13.7%] of 265) (based on life-table method), and there were statistical differences between the investigational and control groups with specific regard to the rate of subsequent revision and supplemental fixation surgical procedures. Rates for additional surgical procedures that involved adjacent levels were lower in the investigational group than in the control group (11 [4.6%] of 276 vs. 24 [11.9%] of 265, respectively). Cervical disc arthroplasty has the potential for preserving motion at the operated level while providing biomechanical stability and global neck mobility and may result in a reduction in adjacent-segment degeneration. The Prestige Cervical Disc maintains improved clinical outcomes and segmental motion after implantation at 7-year follow-up. Clinical trial registration no. NCT00642876 ( ClinicalTrials.gov ).

Comparison of the incidence of patient-reported post-operative dysphagia between ACDF with a traditional anterior plate and artificial cervical disc replacement.

PubMed

Yang, Yi; Ma, Litai; Liu, Hao; Liu, Yilian; Hong, Ying; Wang, Beiyu; Ding, Chen; Deng, Yuxiao; Song, Yueming; Liu, Limin

2016-09-01

Compared with anterior cervical discectomy and fusion (ACDF), cervical disc replacement (CDR) has provided satisfactory clinical results. The incidence of post-operative dysphagia between ACDF with a traditional anterior plate and CDR remains controversial. Considering the limited studies and knowledge in this area, a retrospective study focusing on post-operative dysphagia was conducted. The Bazaz grading system was used to assess the severity of dysphagia at post-operative intervals including 1 week, 1 month, 3 months, 6 months, 12 months and 24 months respectively. The Chi-square test, Student t-test, Mann-Whitney U tests and Ordinal Logistic regression were used for data analysis when appropriate. Statistical significance was accepted at a probability value of <0.05. Two hundred and thirty-one patients in the CDR group and one hundred and fifty-eight patients in Plate group were included in this study. The total incidences of dysphagia in the CDR and plate group were 36.58% and 60.43% at one week, 29.27% and 38.85% at one month, 21.95% and 31.65% at three months, 6.83% and 17.99% at six months, 5.85% and 14.39% at 12 months, and 4.39% and 10.07% at the final follow-up respectively (All P<0.05, Mann-Whitney U test). Ordinal Logistic regression analysis showed that female patients, two-level surgery, C4/5 surgery, and anterior cervical plating were significant risk factors for post-operative dysphagia (all P<0.05). Comparing ACDF with a plate, CDR with a Prestige LP can significantly reduce both transient and persistent post-operative dysphagia. Female patients, two-level surgery, C4/5 surgery and anterior cervical plating were associated with a higher incidence of dysphagia. Future prospective, randomized, controlled studies are needed to further validate these findings. Copyright © 2016 Elsevier B.V. All rights reserved.

A case of industrial safety appraisal for extension of service life of GTK-10-4 gas turbines used at gas transmission stations

NASA Astrophysics Data System (ADS)

Rybnikov, A. I.; Kovalev, A. G.; Kryukov, I. I.; Leont'ev, S. A.; Moshnikov, A. V.

2017-04-01

It is shown that the extended life and enhanced operational reliability of parts and subassemblies of the most popular GTK-10-4 gas transmission plants are determined by the enhanced efficiency of the control over technical condition and operational safety of turbine plants in conformity with industrial safety requirements imposed on gas pipeline compressor stations. It has been established that the materials of parts and subassemblies of gas turbine plants with different, especially with maximal operating time, shall be exposed to NDT for the purpose of determining the actual mechanical characteristics of these materials with different operating time and calculating residual life. The analysis of damageability and operating conditions has helped to identify parts and subassemblies for repair or replacement with the highest frequency of unacceptable defects. These parts and subassemblies have been shown to include base members of the axial compressor (AC), a turbine housing, an axial compressor rotor, high- and low-pressure turbine (HPT and LPT) discs, a 12-part holder, the housing of the holder of HPT and LPT guiding blades, a sealed baffler, and working and guiding AC, LPT and HPT blades. The most typical operational defects have been enumerated and analyzed. It has been determined that the primary task of the industrial safety appraisal for extending the life of GTK-10-4 with limit-exceeding operating time is to thoroughly examine HPT and LPT discs with more than 130,000 hours of operating time and establish by DT methods characteristics of materials for evaluation, taking account of their degradation, and residual life of critical turbine elements. In addition, it has been shown that the service life of HP turbine discs can be extended by replacing the disc material (EP-428 12% chromium steel) with a material with a higher linear expansion factor that somewhat exceeds the expansion factor of EI-893 nickel alloy used to melt out working blades.

Effects of Neonatal Enzyme Replacement Therapy and Simvastatin Treatment on Cervical Spine Disease in Mucopolysaccharidosis I Dogs

PubMed Central

Chiaro, Joseph A; O’Donnell, Patricia; Shore, Eileen M; Malhotra, Neil R; Ponder, Katherine P; Haskins, Mark E; Smith, Lachlan J

2014-01-01

Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease characterized by deficient α-L-iduronidase activity, leading to the accumulation of poorly degraded glycosaminoglycans (GAGs). Children with MPS I exhibit high incidence of spine disease, including accelerated disc degeneration and vertebral dysplasia, which in turn lead to spinal cord compression and kypho-scoliosis. In this study we investigated the efficacy of neonatal enzyme replacement therapy (ERT), alone or in combination with oral simvastatin (ERT+SIM) for attenuating cervical spine disease progression in MPS I, using a canine model. Four groups were studied: normal controls; MPS I untreated; MPS I ERT treated; and MPS I ERT+SIM treated. Animals were euthanized at one year-of-age. Intervertebral disc condition and spinal cord compression were evaluated from MRIs and plain radiographs, vertebral bone condition and odontoid hypoplasia were evaluated using microcomputed tomography, and epiphyseal cartilage to bone conversion was evaluated histologically. Untreated MPS I animals exhibited more advanced disc degeneration and more severe spinal cord compression than normal animals. Both treatment groups resulted in partial preservation of disc condition and cord compression, with ERT+SIM not significantly better than ERT alone. Untreated MPS I animals had significantly lower vertebral trabecular bone volume and mineral density, while ERT treatment resulted in partial preservation of these properties. ERT+SIM treatment demonstrated similar, but not greater, efficacy. Both treatment groups partially normalized endochondral ossification in the vertebral epiphyses (as indicated by absence of persistent growth plate cartilage), and odontoid process size and morphology. These results indicate that ERT begun from a very early age attenuates the severity of cervical spine disease in MPS I, particularly for the vertebral bone and odontoid process, and that additional treatment with simvastatin does not provide a significant additional benefit over ERT alone. PMID:24898323

Rat disc torsional mechanics: effect of lumbar and caudal levels and axial compression load.

PubMed

Espinoza Orías, Alejandro A; Malhotra, Neil R; Elliott, Dawn M

2009-03-01

Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior to evaluate changes after model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Cadaveric biomechanical study. Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. The apparent torsional modulus was higher in the lumbar region than in the caudal region: 0.081+/-0.026 (MPa/degrees, mean+/-SD) for lumbar axially loaded; 0.066+/-0.028 for caudal axially loaded; 0.091+/-0.033 for lumbar in pure torsion; and 0.056+/-0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/degrees. Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics.

Novel Human Intervertebral Disc Strain Template to Quantify Regional Three-Dimensional Strains in a Population and Compare to Internal Strains Predicted by a Finite Element Model

PubMed Central

Showalter, Brent L.; DeLucca, John F.; Peloquin, John M.; Cortes, Daniel H.; Yoder, Jonathon H.; Jacobs, Nathan T.; Wright, Alexander C.; Gee, James C.; Vresilovic, Edward J.; Elliott, Dawn M.

2017-01-01

Tissue strain is an important indicator of mechanical function, but is difficult to noninvasively measure in the intervertebral disc. The objective of this study was to generate a disc strain template, a 3D average of disc strain, of a group of human L4–L5 discs loaded in axial compression. To do so, magnetic resonance images of uncompressed discs were used to create an average disc shape. Next, the strain tensors were calculated pixel-wise by using a previously developed registration algorithm. Individual disc strain tensor components were then transformed to the template space and averaged to create the disc strain template. The strain template reduced individual variability while highlighting group trends. For example, higher axial and circumferential strains were present in the lateral and posterolateral regions of the disc, which may lead to annular tears. This quantification of group-level trends in local 3D strain is a significant step forward in the study of disc biomechanics. These trends were compared to a finite element model that had been previously validated against the disc-level mechanical response. Depending on the strain component, 81–99% of the regions within the finite element model had calculated strains within one standard deviation of the template strain results. The template creation technique provides a new measurement technique useful for a wide range of studies, including more complex loading conditions, the effect of disc pathologies and degeneration, damage mechanisms, and design and evaluation of treatments. PMID:26694516

Rationale, principles and experimental evaluation of the concept of soft stabilization.

PubMed

Mulholland, Robert C; Sengupta, Dilip K

2002-10-01

The apparent clinical success of spinal stabilization methods that restrict rather than abolish movement in relieving mechanical back pain indicates that the concept of the aetiology of back pain should be reviewed. Further understanding of how degeneration affects disc biomechanics, and an understanding of how current soft stabilization systems alters them, may allow us to define more precisely what are the essential requirements of an ideal soft stabilization system. It appears that abnormal patterns of loading rather than abnormal movement are the reason that disc degeneration causes back pain in some patients. Abnormal load transmission is the principal cause of pain in osteoarthritic joints, and both osteotomy and, indeed, joint replacement succeed because they alter the load transmission across the joint. This concept is supported by the fact that abnormal patterns of stress distribution measured across the disc correlate with painful discs on discography. Clinically, it is often noted that back pain is primarily related to position or posture, rather than movement of the lumbar spine. Clinical success after solid fusion is unpredictable because it does not necessarily prevent painful loading across the disc, and also it may interfere with maintenance of sagittal balance in varying postures. The Graf ligament restricted flexion, and was modestly successful. It unfortunately increased the load over the posterior annulus. The Dynesys system reduces movement both in flexion and extension, and appears to be more successful. However, often it also unloads the disc to a degree that is unpredictable. The authors believe that this unloading of the disc is an important feature of a flexible stabilization system. A new a design of a flexible stabilization system has recently been described in an in vitro study, which unloads the disc by introduction of a load-sharing fulcrum near the axis of movement together with an elastic posterior ligament. This design produces maximal unloading of the disc, whilst allowing a restricted range of movement, which serves the important purpose of allowing the patient to maintain sagittal balance in varying postures.

Polar alignment of a protoplanetary disc around an eccentric binary II: Effect of binary and disc parameters

NASA Astrophysics Data System (ADS)

Martin, Rebecca G.; Lubow, Stephen H.

2018-06-01

In a recent paper Martin & Lubow showed that a circumbinary disc around an eccentric binary can undergo damped nodal oscillations that lead to the polar (perpendicular) alignment of the disc relative to the binary orbit. The disc angular momentum vector aligns to the eccentricity vector of the binary. We explore the robustness of this mechanism for a low mass disc (0.001 of the binary mass) and its dependence on system parameters by means of hydrodynamic disc simulations. We describe how the evolution depends upon the disc viscosity, temperature, size, binary mass ratio, orbital eccentricity and inclination. We compare results with predictions of linear theory. We show that polar alignment of a low mass disc may occur over a wide range of binary-disc parameters. We discuss the application of our results to the formation of planetary systems around eccentric binary stars.

Rat Disc Torsional Mechanics: Effect of Lumbar and Caudal Levels and Axial Compression Load

PubMed Central

Elliott, Dawn M; Espinoza Orías, Alejandro A; Malhotra, Neil R

2009-01-01

Background Context Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior in order to evaluate changes following model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Purpose Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Study Design Cadaveric biomechanical study. Methods Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. Results The apparent torsional modulus was higher in the lumbar region than in the caudal region,: 0.081±0.026 (MPa/°, Mean±SD) for lumbar axially loaded; 0.066±0.028 caudal axially loaded; 0.091±0.033 for lumbar in pure torsion; and 0.056±0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/°. Conclusions Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics. PMID:18495544

The comparative analysis of rocks' resistance to forward-slanting disc cutters and traditionally installed disc cutters

NASA Astrophysics Data System (ADS)

Zhang, Zhao-Huang; Fei, Sun; Liang, Meng

2016-08-01

At present, disc cutters of a full face rock tunnel boring machine are mostly mounted in the traditional way. Practical use in engineering projects reveals that this installation method not only heavily affects the operation life of disc cutters, but also increases the energy consumption of a full face rock tunnel boring machine. To straighten out this issue, therefore, a rock-breaking model is developed for disc cutters' movement after the research on the rock breaking of forward-slanting disc cutters. Equations of its displacement are established based on the analysis of velocity vector of a disc cutter's rock-breaking point. The functional relations then are brought forward between the displacement parameters of a rock-breaking point and its coordinate through the analysis of micro displacement of a rock-breaking point. Thus, the geometric equations of rock deformation are derived for the forward-slanting installation of disc cutters. With a linear relationship remaining between the acting force and its deformation either before or after the leap breaking, the constitutive relation of rock deformation can be expressed in the form of generalized Hooke law, hence the comparative analysis of the variation in the resistance of rock to the disc cutters mounted in the forward-slanting way with that in the traditional way. It is discovered that with the same penetration, strain of the rock in contact with forward-slanting disc cutters is apparently on the decline, in other words, the resistance of rock to disc cutters is reduced. Thus wear of disc cutters resulted from friction is lowered and energy consumption is correspondingly decreased. It will be useful for the development of installation and design theory of disc cutters, and significant for the breakthrough in the design of full face rock tunnel boring machine.

Dysfunction of mechanical heart valve prosthesis: experience with surgical management in 48 patients

PubMed Central

Ma, Wei-Guo; Hou, Bin; Abdurusul, Adiljan; Gong, Ding-Xu; Tang, Yue; Chang, Qian; Xu, Jian-Ping

2015-01-01

Background Dysfunction of mechanical heart valve prostheses is an unusual but potentially lethal complication after mechanical prosthetic valve replacement. We seek to report our experience with mechanical valve dysfunction regarding etiology, surgical techniques and early outcomes. Methods Clinical data of 48 patients with mechanical valve dysfunction surgically treated between October 1996 and June 2011 were analyzed. Results Mean age was 43.7±10.9 years and 34 were female (70.8%). The median interval from primary valve implantation to dysfunction was 44.5 months (range, 1 hour to 20 years). There were 21 emergent and 27 elective reoperations. The etiology was thrombosis in 19 cases (39.6%), pannus in 12 (25%), thrombosis and pannus in 11 (22.9%), improper disc orientation in 2 (4.1%), missing leaflet in 1 (2.1%), excessively long knot end in 1 (2.1%), endogenous factor in 1 (2.1%) and unidentified in 1 (2.1%). Surgical procedure was mechanical valve replacement in 37 cases (77.1%), bioprosthetic valve replacement in 7 (14.9%), disc rotation in 2 (4.2%) and excision of excessive knot end in 1 (2.1%). Early deaths occurred in 7 patients (14.6%), due to low cardiac output in 3 (6.3%), multi-organ failure in 2 (4.2%) and refractory ventricular fibrillation in 2 (4.2%). Complications occurred in 10 patients (20.8%). Conclusions Surgical management of mechanical valve dysfunction is associated with significant mortality and morbidity. Earlier identification and prompt reoperation are vital to achieving better clinical outcomes. The high incidence of thrombosis in this series highlights the need for adequate anticoagulation and regular follow-up after mechanical valve replacement. PMID:26793354

Early UV emission from disc-originated matter (DOM) in Type Ia supernovae in the double-degenerate scenario

NASA Astrophysics Data System (ADS)

Levanon, Naveh; Soker, Noam

2017-09-01

We show that the blue and UV excess emission in the first few days of some Type Ia supernovae (SNe Ia) can be accounted in the double-degenerate (DD) scenario by the collision of the SN ejecta with circumstellar matter that was blown by the accretion disc formed during the merger process of the two white dwarfs (WDs). We assume that in cases of excess early light, the disc blows the circumstellar matter, that we term disc-originated matter (DOM), hours to days before explosion. To perform our analysis, we first provide a model-based definition for early excess light, replacing the definition of excess light relative to a power-law fit to the rising luminosity. We then examine the light curves of the SNe Ia iPTF14atg and SN 2012cg, and find that the collision of the ejecta with a DOM in the frame of the DD scenario can account for their early excess emission. Thus, early excess light does not necessarily imply the presence of a stellar companion in the frame of the single-degenerate scenario. Our findings further increase the variety of phenomena that the DD scenario can account for, and emphasize the need to consider all different SN Ia scenarios when interpreting observations.

Adaptive alterations of elastic fibers in the bilaminar zone of rabbit temporomandibular joint following disc displacement.

PubMed

Gu, Zhiyuan; Wu, Huiling; Feng, Jianying; Shibata, Takanori; Hu, Ji'an; Zhang, Yinkai; Xie, Zhijian

2002-12-01

To study the adaptive alterations of elastic fibers in the bilaminar zone (BZ) of rabbit temporomandibular joint (TMJ) following disc displacement. Twenty-eight Japanese white rabbits were used in this study. The right temporomandibular joints of 20 of 28 rabbits were subjected to the surgical procedure of anterior disc displacement (ADD). Four rabbits in the surgical group were sacrificed at 2, 4, 6, 8 and 12 weeks after operation. Their temporomandibular joints were studied histochemically. Elastic fibers were reduced in number and ran irregularly in the superior lamina of BZ from ADD rabbits. The jungly elastic fibers (EFs) could still be seen at 2 weeks after operation. At 4 weeks, the number of EFs decreased significantly; EFs lost their jungly arrangement and were shaped like rough dots, of which the arrangement and the lengths were different. Six weeks after operation, many EFs were replaced by distorted, uneven, non-oriented fine EFs, distributed unevenly and some thick or fine EFs that ran irregularly. The number of EFs decreased further and their arrangement was more deranged at 8 weeks. At 10 and 12 weeks, EFs in the superior lamina of BZ were similar to those at 8 weeks. Our results show that EFs lost their function as well as their distribution and arrangement after disc displacement.

Expression of DISC1-interactome members correlates with cognitive phenotypes related to schizophrenia.

PubMed

Rampino, Antonio; Walker, Rosie May; Torrance, Helen Scott; Anderson, Susan Maguire; Fazio, Leonardo; Di Giorgio, Annabella; Taurisano, Paolo; Gelao, Barbara; Romano, Raffaella; Masellis, Rita; Ursini, Gianluca; Caforio, Grazia; Blasi, Giuseppe; Millar, J Kirsty; Porteous, David John; Thomson, Pippa Ann; Bertolino, Alessandro; Evans, Kathryn Louise

2014-01-01

Cognitive dysfunction is central to the schizophrenia phenotype. Genetic and functional studies have implicated Disrupted-in-Schizophrenia 1 (DISC1), a leading candidate gene for schizophrenia and related psychiatric conditions, in cognitive function. Altered expression of DISC1 and DISC1-interactors has been identified in schizophrenia. Dysregulated expression of DISC1-interactome genes might, therefore, contribute to schizophrenia susceptibility via disruption of molecular systems required for normal cognitive function. Here, the blood RNA expression levels of DISC1 and DISC1-interacting proteins were measured in 63 control subjects. Cognitive function was assessed using neuropsychiatric tests and functional magnetic resonance imaging was used to assess the activity of prefrontal cortical regions during the N-back working memory task, which is abnormal in schizophrenia. Pairwise correlations between gene expression levels and the relationship between gene expression levels and cognitive function and N-back-elicited brain activity were assessed. Finally, the expression levels of DISC1, AKAP9, FEZ1, NDEL1 and PCM1 were compared between 63 controls and 69 schizophrenic subjects. We found that DISC1-interactome genes showed correlated expression in the blood of healthy individuals. The expression levels of several interactome members were correlated with cognitive performance and N-back-elicited activity in the prefrontal cortex. In addition, DISC1 and NDEL1 showed decreased expression in schizophrenic subjects compared to healthy controls. Our findings highlight the importance of the coordinated expression of DISC1-interactome genes for normal cognitive function and suggest that dysregulated DISC1 and NDEL1 expression might, in part, contribute to susceptibility for schizophrenia via disruption of prefrontal cortex-dependent cognitive functions.

Expression of DISC1-Interactome Members Correlates with Cognitive Phenotypes Related to Schizophrenia

PubMed Central

Rampino, Antonio; Walker, Rosie May; Torrance, Helen Scott; Anderson, Susan Maguire; Fazio, Leonardo; Di Giorgio, Annabella; Taurisano, Paolo; Gelao, Barbara; Romano, Raffaella; Masellis, Rita; Ursini, Gianluca; Caforio, Grazia; Blasi, Giuseppe; Millar, J. Kirsty; Porteous, David John; Thomson, Pippa Ann; Bertolino, Alessandro; Evans, Kathryn Louise

2014-01-01

Cognitive dysfunction is central to the schizophrenia phenotype. Genetic and functional studies have implicated Disrupted-in-Schizophrenia 1 (DISC1), a leading candidate gene for schizophrenia and related psychiatric conditions, in cognitive function. Altered expression of DISC1 and DISC1-interactors has been identified in schizophrenia. Dysregulated expression of DISC1-interactome genes might, therefore, contribute to schizophrenia susceptibility via disruption of molecular systems required for normal cognitive function. Here, the blood RNA expression levels of DISC1 and DISC1-interacting proteins were measured in 63 control subjects. Cognitive function was assessed using neuropsychiatric tests and functional magnetic resonance imaging was used to assess the activity of prefrontal cortical regions during the N-back working memory task, which is abnormal in schizophrenia. Pairwise correlations between gene expression levels and the relationship between gene expression levels and cognitive function and N-back-elicited brain activity were assessed. Finally, the expression levels of DISC1, AKAP9, FEZ1, NDEL1 and PCM1 were compared between 63 controls and 69 schizophrenic subjects. We found that DISC1-interactome genes showed correlated expression in the blood of healthy individuals. The expression levels of several interactome members were correlated with cognitive performance and N-back-elicited activity in the prefrontal cortex. In addition, DISC1 and NDEL1 showed decreased expression in schizophrenic subjects compared to healthy controls. Our findings highlight the importance of the coordinated expression of DISC1-interactome genes for normal cognitive function and suggest that dysregulated DISC1 and NDEL1 expression might, in part, contribute to susceptibility for schizophrenia via disruption of prefrontal cortex-dependent cognitive functions. PMID:24940743

A RCT comparing 7-year clinical outcomes of one level symptomatic cervical disc disease (SCDD) following ProDisc-C total disc arthroplasty (TDA) versus anterior cervical discectomy and fusion (ACDF).

PubMed

Loumeau, Thomas P; Darden, Bruce V; Kesman, Thomas J; Odum, Susan M; Van Doren, Bryce A; Laxer, Eric B; Murrey, Daniel B

2016-07-01

The objective of this trial was to compare the safety and efficacy of TDA using the ProDisc-C implant to ACDF in patients with single-level SCDD between C3 and C7. We report on the single-site results from a larger multicenter trial of 13 sites using an approved US Food and Drug Administration protocol (prospective, randomized controlled non-inferiority design). Patients were randomized one-to-one to either the ProDisc-C device or ACDF. All enrollees were evaluated pre- and post-operatively at regular intervals through month 84. Visual Analog Scale (VAS) for neck and arm pain/intensity, Neck Disability Index (NDI), Short-Form 36 (SF-36), and satisfaction were assessed. Twenty-two patients were randomized to each arm of the study. Nineteen additional patients received the ProDisc-C via continued access. NDI improved with the ProDisc-C more than with ACDF. Total range of motion was maintained with the ProDisc-C, but diminished with ACDF. Neck and arm pain improved more in the ProDisc-C than ACDF group. Patient satisfaction remained higher in the ProDisc-C group at 7 years. SF-36 scores were higher in the TDA group than ACDF group at 7 years; the difference was not clinically significant. Six additional operations (two at the same level; four at an adjacent level) were performed in the ACDF, but none in the ProDisc-C group. The ProDisc-C implant appears to be safe and effective for the treatment of SCDD. Patients with the implant retained motion at the involved segment and had a lower reoperation rate than those with an ACDF.

Accessing Suomi NPP OMPS Products through the GES DISC Online Data Services

NASA Technical Reports Server (NTRS)

Johnson, J.; Wei, J.; Gerasimov, I.; Vollmer, Bruce E.

2017-01-01

This presentation will provide an overview of the OMPS products available at the GES DISC archive, as well as demonstrate the various data services provided by the GES DISC. Since the TOMS, SBUV, and EOS Aura (OMI, MLS, HIRDLS) data products are also available from the GES DISC archive, these can be easily accessed and compared with the OMPS data.

Topographic optic disc analysis by Heidelberg retinal tomography in ocular Behçet's disease

PubMed Central

Berker, Nilufer; Elgin, Ufuk; Ozdal, Pinar; Batman, Aygen; Soykan, Emel; Ozkan, Seyhan S

2007-01-01

Aim To compare the topographic characteristics of the optic discs in patients with severe and mild ocular Behçet's disease by using Heidelberg retinal tomographaphy (HRT). Methods This prospective study included 47 eyes of 47 patients with ocular BD who were being followed‐up at the Uveitis Clinic of the Ankara Ulucanlar Eye Research Hospital, Ankara, Turkey. The patients were divided into two groups. Group 1 consisted of 21 eyes with mild uveitis, and group 2 consisted of 26 eyes with severe uveitis. All patients underwent topographic optic disc analysis by HRT II, and the quantitative optic disc parameters of both groups were compared by non‐parametric Mann‐Whitney U test. Results The mean cup volume, rim volume, cup area, disc area and cup depth in group 1 were found to be statistically significantly greater than those in group 2 (p<0.0001, p = 0.03, p = 0.021, p = 0.01 and p = 0.017, respectively), while the difference between the mean cup‐to‐disc ratios in group 1 and group 2 were found to be statistically insignificant (p = 0.148). Conclusion A relationship was found between the severity of ocular BD and optic disc topography determined by HRT. In eyes with smaller optic discs, uveitis was observed to have a more severe course with more frequent relapses than those with larger discs. PMID:17475703

Topographic optic disc analysis by Heidelberg retinal tomography in ocular Behcet's disease.

PubMed

Berker, Nilufer; Elgin, Ufuk; Ozdal, Pinar; Batman, Aygen; Soykan, Emel; Ozkan, Seyhan S

2007-09-01

To compare the topographic characteristics of the optic discs in patients with severe and mild ocular Behçet's disease by using Heidelberg retinal tomographaphy (HRT). This prospective study included 47 eyes of 47 patients with ocular BD who were being followed-up at the Uveitis Clinic of the Ankara Ulucanlar Eye Research Hospital, Ankara, Turkey. The patients were divided into two groups. Group 1 consisted of 21 eyes with mild uveitis, and group 2 consisted of 26 eyes with severe uveitis. All patients underwent topographic optic disc analysis by HRT II, and the quantitative optic disc parameters of both groups were compared by non-parametric Mann-Whitney U test. The mean cup volume, rim volume, cup area, disc area and cup depth in group 1 were found to be statistically significantly greater than those in group 2 (p<0.0001, p = 0.03, p = 0.021, p = 0.01 and p = 0.017, respectively), while the difference between the mean cup-to-disc ratios in group 1 and group 2 were found to be statistically insignificant (p = 0.148). A relationship was found between the severity of ocular BD and optic disc topography determined by HRT. In eyes with smaller optic discs, uveitis was observed to have a more severe course with more frequent relapses than those with larger discs.

Planetesimal formation in self-gravitating discs - dust trapping by vortices

NASA Astrophysics Data System (ADS)

Gibbons, P. G.; Mamatsashvili, G. R.; Rice, W. K. M.

2015-11-01

The mechanism through which metre-sized boulders grow to km-sized planetesimals in protoplanetary discs is a subject of active research, since it is critical for planet formation. To avoid spiralling into the protostar due to aerodynamic drag, objects must rapidly grow from cm-sized pebbles, which are tightly coupled to the gas, to large boulders of 1-100 m in diameter. It is already well known that overdensities in the gaseous component of the disc provide potential sites for the collection of solids, and that significant density structures in the gaseous component of the disc (e.g. spiral density waves) can trap solids efficiently enough for the solid component of the disc to undergo further gravitational collapse due to their own self-gravity. In this work, we employ the PENCIL CODE to conduct local shearing sheet simulations of massive self-gravitating protoplanetary discs, to study the effect of anticyclonic transient vortices, or eddies, on the evolution of solids in these discs. We find that these types of structures are extremely efficient at concentrating small and intermediate-sized dust particles with friction times comparable to, or less than, the local orbital period of the disc. This can lead to significant over-densities in the solid component of the disc, with density enhancements comparable to, and even higher, than those within spiral density waves; increasing the rate of gravitational collapse of solids into bound structures.

Effect of ligamenta flava hypertrophy on lumbar disc herniation with contralateral symptoms and signs: a clinical and morphometric study

PubMed Central

Yildizhan, Ahmet; Atar, Elmas K.; Yaycioglu, Soner; Gocmen-Mas, Nuket; Yazici, Canan

2010-01-01

Introduction The purpose of this study was to determine whether ligamentum flavum hypertrophy among disc herniated patients causes contralateral pain symptoms. For this reason we measured the thickness of the ligament in disc herniated patients with ipsilateral or contralateral symptoms. Material and methods Two hundred disc herniated patients with ipsilateral symptoms as group I were compared with five disc herniated patients with only contralateral symptoms as group II. Ligamenta flava thicknesses and spinal canal diameters of both groups were measured on magnetic resonance imaging (MRI) with a micro-caliper. Results Both groups underwent surgery only on the disc herniated side. The total thicknesses of the ligamenta flava in group II was thicker than in group I. There was no spinal stenosis in either group and no significance difference between the groups. Statistically significant differences were found for both ipsilateral and contralateral thickness of the ligament flava in both groups. We also compared thickness of the ligamenta flava for each level of disc herniation in group I; ligamenta flava hypertrophy was more common at L3-L4 and L4-L5 levels of vertebrae in females. Conclusions Aetiology of contralateral sciatica among disc herniated patients may be related to hypertrophy of the ligamenta flava, especially on the opposite side. Surgical approaches of the disc herniated side alone may be sufficient for a good outcome. PMID:22371809

Evolution of Information Management at the GSFC Earth Sciences (GES) Data and Information Services Center (DISC): 2006-2007

NASA Technical Reports Server (NTRS)

Kempler, Steven; Lynnes, Christopher; Vollmer, Bruce; Alcott, Gary; Berrick, Stephen

2009-01-01

Increasingly sophisticated National Aeronautics and Space Administration (NASA) Earth science missions have driven their associated data and data management systems from providing simple point-to-point archiving and retrieval to performing user-responsive distributed multisensor information extraction. To fully maximize the use of remote-sensor-generated Earth science data, NASA recognized the need for data systems that provide data access and manipulation capabilities responsive to research brought forth by advancing scientific analysis and the need to maximize the use and usability of the data. The decision by NASA to purposely evolve the Earth Observing System Data and Information System (EOSDIS) at the Goddard Space Flight Center (GSFC) Earth Sciences (GES) Data and Information Services Center (DISC) and other information management facilities was timely and appropriate. The GES DISC evolution was focused on replacing the EOSDIS Core System (ECS) by reusing the In-house developed disk-based Simple, Scalable, Script-based Science Product Archive (S4PA) data management system and migrating data to the disk archives. Transition was completed in December 2007

Pannus-related prosthetic valve dysfunction. Case report

PubMed Central

MOLDOVAN, MARIA-SÎNZIANA; BEDELEANU, DANIELA; KOVACS, EMESE; CIUMĂRNEAN, LORENA; MOLNAR, ADRIAN

2016-01-01

Pannus-related prosthetic valve dysfunction, a complication of mechanical prosthetic valve replacement, is rare, with a slowly progressive evolution, but it can be acute, severe, requiring surgical reintervention. We present the case of a patient with a mechanical single disc aortic prosthesis, with moderate prosthesis-patient mismatch, minor pannus found on previous ultrasound examinations, who presented to our service with angina pain with a duration of 1 hour, subsequently interpreted as non-ST segment elevation myocardial infarction (NSTEMI) syndrome. Coronarography showed normal epicardial coronary arteries, an ample movement of the prosthetic disc, without evidence of coronary thromboembolism, and Gated Single-Photon Emission Computerized Tomography (SPECT) with Technetium (Tc)-99m detected no perfusion defects. Transthoracic echocardiography (TTE) evidenced a dysfunctional prosthesis due to a subvalvular mass; transesophageal echocardiography (TOE) showed the interference of this mass, with a pannus appearance, with the closure of the prosthetic disc. Under conditions of repeated angina episodes, under anticoagulant treatment, surgery was performed, with the intraoperative confirmation of pannus and its removal. Postoperative evolution was favorable. This case reflects the diagnostic and therapeutic management problems of pannus-related prosthetic valve dysfunction. PMID:27004041

Pannus-related prosthetic valve dysfunction. Case report.

PubMed

Moldovan, Maria-Sînziana; Bedeleanu, Daniela; Kovacs, Emese; Ciumărnean, Lorena; Molnar, Adrian

2016-01-01

Pannus-related prosthetic valve dysfunction, a complication of mechanical prosthetic valve replacement, is rare, with a slowly progressive evolution, but it can be acute, severe, requiring surgical reintervention. We present the case of a patient with a mechanical single disc aortic prosthesis, with moderate prosthesis-patient mismatch, minor pannus found on previous ultrasound examinations, who presented to our service with angina pain with a duration of 1 hour, subsequently interpreted as non-ST segment elevation myocardial infarction (NSTEMI) syndrome. Coronarography showed normal epicardial coronary arteries, an ample movement of the prosthetic disc, without evidence of coronary thromboembolism, and Gated Single-Photon Emission Computerized Tomography (SPECT) with Technetium (Tc)-99m detected no perfusion defects. Transthoracic echocardiography (TTE) evidenced a dysfunctional prosthesis due to a subvalvular mass; transesophageal echocardiography (TOE) showed the interference of this mass, with a pannus appearance, with the closure of the prosthetic disc. Under conditions of repeated angina episodes, under anticoagulant treatment, surgery was performed, with the intraoperative confirmation of pannus and its removal. Postoperative evolution was favorable. This case reflects the diagnostic and therapeutic management problems of pannus-related prosthetic valve dysfunction.

[Design and research progress of zero profile cervical Interbody cage].

PubMed

Zhu, Jia; Wang, Song; Liao, Zhenhua; Liu, Weiqiang

2017-02-01

Zero profile cervical interbody cage is an improvement of traditional fusion products and necessary supplement of emerging artificial intervertebral disc products. When applied in Anterior Cervical Decompression Fusion(ACDF), zero profile cervical interbody cage can preserve the advantages of traditional fusion and reduce the incidence of postoperative complications. Moreover, zero profile cervical interbody cage can be applied under the tabu symptoms of Artificial Cervical Disc Replacement(ACDR). This article summarizes zero profile interbody cage products that are commonly recognized and widely used in clinical practice in recent years, and reviews the progress of structure design and material research of zero profile cervical interbody cage products. Based on the latest clinical demands and research progress, this paper also discusses the future development directions of zero profile interbody cage.

Biomechanical analysis of disc pressure and facet contact force after simulated two-level cervical surgeries (fusion and arthroplasty) and hybrid surgery.

PubMed

Park, Jon; Shin, Jun Jae; Lim, Jesse

2014-12-01

The objective of this study was designed to compare 2-level cervical disc surgery (2-level anterior cervical discectomy and fusion [ACDF] or disc arthroplasty) and hybrid surgery (ACDF/arthroplasty) in terms of postoperative adjacent-level intradiscal pressure (IDP) and facet contact force (FCF). Twenty-four cadaveric cervical spines (C3-T2) were tested in various modes, including extension, flexion, and bilateral axial rotation, to compare adjacent-level IDP and FCF after specified treatments as follows: 1) C5-C6 arthroplasty using ProDisc-C (Synthes Spine, West Chester, Pennsylvania, USA) and C6-C7 ACDF, 2) C5-C6 ACDF and C6-C7 arthroplasty using ProDisc-C, 3) 2-level C5-C6/C6-C7 disc arthroplasties, and 4) 2-level C5-C6/C6-C7 ACDF. IDPs were recorded at anterior, central, and posterior disc portions. After 2-level cervical arthrodesis (ACDF), IDP increased significantly at the anterior annulus of distal adjacent-level disc during flexion and axial rotation and at the center of proximal adjacent-level disc during flexion. In contrast, after cervical specified treatments, including disc arthroplasty (2-level disc arthroplasties and hybrid surgery), IDP decreased significantly at the anterior annulus of distal adjacent-level disc during flexion and extension and was unchanged at the center of proximal adjacent-level disc during flexion. Two-level cervical arthrodesis also tended to adversely impact facet loads, increasing distal rather than proximal adjacent-level FCF. Both hybrid surgery and 2-level arthroplasties seem to offer significant advantages over 2-level arthrodesis by reducing IDP at adjacent levels and approximating FCF of an intact spine. These findings suggest that cervical arthroplasties and hybrid surgery are an alternative to reduce IDP and facet loads at adjacent levels. Copyright © 2014 Elsevier Inc. All rights reserved.

Solid radiographic fusion with a nonconstrained device 5 years after cervical arthroplasty.

PubMed

Heary, Robert F; Goldstein, Ira M; Getto, Katarzyna M; Agarwal, Nitin

2014-12-01

Cervical disc arthroplasty (CDA) has been gaining popularity as a surgical alternative to anterior cervical discectomy and fusion. Spontaneous fusion following a CDA is uncommon. A few anecdotal reports of heterotrophic ossification around the implant sites have been noted for the BRYAN, ProDisc-C, Mobi-C, PRESTIGE, and PCM devices. All CDA fusions reported to date have been in devices that are semiconstrained. The authors reported the case of a 56-year-old man who presented with left C-7 radiculopathy and neck pain for 10 weeks after an assault injury. There was evidence of disc herniation at the C6-7 level. He was otherwise healthy with functional scores on the visual analog scale (VAS, 4.2); neck disability index (NDI, 16); and the 36-item short form health survey (SF-36; physical component summary [PSC] score 43 and mental component summary [MCS] score 47). The patient underwent total disc replacement in which the DISCOVER Artificial Cervical Disc (DePuy Spine, Inc.) was used. The patient was seen at regular follow-up visits up to 60 months. At his 60-month follow-up visit, he had complete radiographic fusion at the C6-7 level with bridging trabecular bone and no motion at the index site on dynamic imaging. He was pain free, with a VAS score of 0, NDI score of 0, and SF-36 PCS and MCS scores of 61 and 55, respectively. Conclusions This is the first case report that identifies the phenomenon of fusion around a nonconstrained cervical prosthesis. Despite this unwanted radiographic outcome, the patient's clinical outcome was excellent.

Percutaneous laser disc decompression versus conventional microdiscectomy for patients with sciatica: Two-year results of a randomised controlled trial.

PubMed

Brouwer, Patrick A; Brand, Ronald; van den Akker-van Marle, M Elske; Jacobs, Wilco Ch; Schenk, Barry; van den Berg-Huijsmans, Annette A; Koes, Bart W; Arts, Mark A; van Buchem, M A; Peul, Wilco C

2017-06-01

Background Percutaneous laser disc decompression is a minimally invasive treatment, for lumbar disc herniation and might serve as an alternative to surgical management of sciatica. In a randomised trial with two-year follow-up we assessed the clinical effectiveness of percutaneous laser disc decompression compared to conventional surgery. Materials and methods This multicentre randomised prospective trial with a non-inferiority design, was carried out according to an intent-to-treat protocol with full institutional review board approval. One hundred and fifteen eligible surgical candidates, with sciatica from a disc herniation smaller than one-third of the spinal canal, were randomly allocated to percutaneous laser disc decompression ( n = 55) or conventional surgery ( n = 57). The main outcome measures for this trial were the Roland-Morris Disability Questionnaire for sciatica, visual analogue scores for back and leg pain and the patient's report of perceived recovery. Results The primary outcome measures showed no significant difference or clinically relevant difference between the two groups at two-year follow-up. The re-operation rate was 21% in the surgery group, which is relatively high, and with an even higher 52% in the percutaneous laser disc decompression group. Conclusion At two-year follow-up, a strategy of percutaneous laser disc decompression, followed by surgery if needed, resulted in non-inferior outcomes compared to a strategy of microdiscectomy. Although the rate of reoperation in the percutaneous laser disc decompression group was higher than expected, surgery could be avoided in 48% of those patients that were originally candidates for surgery. Percutaneous laser disc decompression, as a non-surgical method, could have a place in the treatment arsenal of sciatica caused by contained herniated discs.

Computational Fluid Dynamics (CFD) investigation onto passenger car disk brake design

NASA Astrophysics Data System (ADS)

Munisamy, Kannan M.; Kanasan Moorthy, Shangkari K.

2013-06-01

The aim of this study is to investigate the flow and heat transfer in ventilated disc brakes using Computational Fluid Dynamics (CFD). NACA Series blade is designed for ventilated disc brake and the cooling characteristic is compared to the baseline design. The ventilated disc brakes are simulated using commercial CFD software FLUENTTM using simulation configuration that was obtained from experiment data. The NACA Series blade design shows improvements in Nusselt number compared to baseline design.

Intervertebral disc-derived stem cells: implications for regenerative medicine and neural repair.

PubMed

Erwin, W Mark; Islam, Diana; Eftekarpour, Eftekhar; Inman, Robert D; Karim, Muhammad Zia; Fehlings, Michael G

2013-02-01

An in vitro and in vivo evaluation of intervertebral disc (IVD)-derived stem/progenitor cells. To determine the chondrogenic, adipogenic, osteogenic, and neurogenic differentiation capacity of disc-derived stem/progenitor cells in vitro and neurogenic differentiation in vivo. Tissue repair strategies require a source of appropriate cells that could be used to replace dead or damaged cells and tissues such as stem cells. Here we examined the potential use of IVD-derived stem cells in regenerative medicine approaches and neural repair. Nonchondrodystrophic canine IVD nucleus pulposus (NP) cells were used to generate stem/progenitor cells (NP progenitor cells [NPPCs]) and the NPPCs were differentiated in vitro into chondrogenic, adipogenic, and neurogenic lineages and in vivo into the neurogenic lineage. NPPCs were compared with bone marrow-derived mesenchymal (stromal) stem cells in terms of the expression of stemness genes. The expression of the neural crest marker protein 0 and the Brachyury gene were evaluated in NP cells and NPPCs. NPPCs contain stem/progenitor cells and express "stemness" genes such as Sox2, Oct3/4, Nanog, CD133, Nestin, and neural cell adhesion molecule but differ from mesenchymal (stromal) stem cells in the higher expression of the Nanog gene by NPPCs. NPPCs do not express protein 0 or the Brachyury gene both of which are expressed by the totality of IVD NP cells. The percentage of NPPCs within the IVD is 1% of the total as derived by colony-forming assay. NPPCs are capable of differentiating along chondrogenic, adipogenic, and neurogenic lineages in vitro and into oligodendrocyte, neuron, and astroglial specific precursor cells in vivo within the compact myelin-deficient shiverer mouse. We propose that the IVD NP represents a regenerative niche suggesting that the IVD could represent a readily accessible source of precursor cells for neural repair and regeneration.

Survivorship and clinical outcomes after multi-level anterior lumbar reconstruction with stand-alone anterior lumbar interbody fusion or hybrid construct.

PubMed

Chen, Benjamin; Akpolat, Yusuf T; Williams, Paul; Bergey, Darren; Cheng, Wayne K

2016-06-01

In multilevel disc disease, there is still uncertainty regarding whether multiple total disc replacement is more effective and safer than fusion. Our objective was to measure and compare the clinical outcome of multilevel hybrid constructs with stand-alone anterior lumbar interbody fusion (ALIF) using a retrospective analysis. Sixty-four patients with chronic low back pain determined to be from two or three-level degenerative disc disease were included. Thirty-three patients were treated with hybrid fusion and 31 with ALIF. Several parameters were retrospectively reviewed, including blood loss, operation time, hospital stay, Visual Analog Scale (VAS) score, Oswestry Disability Index (ODI), and survivorship without the need for revision surgery. Telephone follow-ups were conducted to ascertain survivorship, clinical outcomes (VAS, ODI) and patient satisfaction. Operation time was longer in the hybrid group (p=0.021). The hybrid group showed a significant improvement in VAS and ODI with 52.2% and 50.0% improvement versus 28.3% and 25.5% in the ALIF group (p<0.05). At the telephone follow-up for patient satisfaction, 95.7% (n=22) of the hybrid group were satisfied and 95.2% (n=21) of the ALIF group were satisfied. Seventy-four percent (n=17) in the hybrid group and 85.7% (n=18) in the ALIF group would choose to do the initial surgery again. Kaplan-Meier analysis showed 80.5% survivorship for hybrids and 75.9% for ALIF at 5years. With our clinical outcomes in VAS and ODI scores, these results, when taken together, indicate that hybrid fusion is a valid and viable alternative to ALIF fusion, with at least equal if not better clinical outcomes in terms of survivorship, back pain, and disability scores. Copyright © 2015 Elsevier Ltd. All rights reserved.

Silk-based multilayered angle-ply annulus fibrosus construct to recapitulate form and function of the intervertebral disc.

PubMed

Bhunia, Bibhas K; Kaplan, David L; Mandal, Biman B

2018-01-16

Recapitulation of the form and function of complex tissue organization using appropriate biomaterials impacts success in tissue engineering endeavors. The annulus fibrosus (AF) represents a complex, multilamellar, hierarchical structure consisting of collagen, proteoglycans, and elastic fibers. To mimic the intricacy of AF anatomy, a silk protein-based multilayered, disc-like angle-ply construct was fabricated, consisting of concentric layers of lamellar sheets. Scanning electron microscopy and fluorescence image analysis revealed cross-aligned and lamellar characteristics of the construct, mimicking the native hierarchical architecture of the AF. Induction of secondary structure in the silk constructs was confirmed by infrared spectroscopy and X-ray diffraction. The constructs showed a compressive modulus of 499.18 ± 86.45 kPa. Constructs seeded with porcine AF cells and human mesenchymal stem cells (hMSCs) showed ∼2.2-fold and ∼1.7-fold increases in proliferation on day 14, respectively, compared with initial seeding. Biochemical analysis, histology, and immunohistochemistry results showed the deposition of AF-specific extracellular matrix (sulfated glycosaminoglycan and collagen type I), indicating a favorable environment for both cell types, which was further validated by the expression of AF tissue-specific genes. The constructs seeded with porcine AF cells showed ∼11-, ∼5.1-, and ∼6.7-fold increases in col I α 1 , sox 9, and aggrecan genes, respectively. The differentiation of hMSCs to AF-like tissue was evident from the enhanced expression of the AF-specific genes. Overall, the constructs supported cell proliferation, differentiation, and ECM deposition resulting in AF-like tissue features based on ECM deposition and morphology, indicating potential for future studies related to intervertebral disc replacement therapy.

Effect of five-membered ring and heteroatom substitution on charge transport properties of perylene discotic derivatives: A theoretical approach.

PubMed

Navarro, Amparo; Fernández-Liencres, M Paz; Peña-Ruiz, Tomás; García, Gregorio; Granadino-Roldán, José M; Fernández-Gómez, Manuel

2016-08-07

Density functional theory calculations were carried out to investigate the evolvement of charge transport properties of a set of new discotic systems as a function of ring and heteroatom (B, Si, S, and Se) substitution on the basic structure of perylene. The replacement of six-membered rings by five-membered rings in the reference compound has shown a prominent effect on the electron reorganization energy that decreases ∼0.2 eV from perylene to the new carbon five-membered ring derivative. Heteroatom substitution with boron also revealed to lower the LUMO energy level and increase the electron affinity, therefore lowering the electron injection barrier compared to perylene. Since the rate of the charge transfer between two molecules in columnar discotic systems is strongly dependent on the orientation of the stacked cores, the total energy and transfer integral of a dimer as a disc is rotated with respect to the other along the stacking axis have been predicted. Aimed at obtaining a more realistic approach to the bulk structure, the molecular geometry of clusters made up of five discs was fully optimized, and charge transfer rate and mobilities were estimated for charge transport along a one dimensional pathway. Heteroatom substitution with selenium yields electron transfer integral values ∼0.3 eV with a relative disc orientation of 25°, which is the preferred angle according to the dimer energy profile. All the results indicate that the tetraselenium-substituted derivative, not synthetized so far, could be a promising candidate among those studied in this work for the fabrication of n-type semiconductors based on columnar discotic liquid crystals materials.

Rapid surface colony counts determination with three new miniaturised techniques.

PubMed

Malik, K A

1977-01-01

Three different miniaturised methods for the rapid surface viable counting are described. The methods were tried in parallel to seven different existing methods (Table 1) for viable counts and were found to be easier, quicker and insome cases more accurate. The techniques require about 10% of the material and time needed for conventional spread-plates method and the results were in no way inferior to that (Table 1 and 2). Mini agar discs were cut aseptically with an especially designed stainless steel agar disc cutter (25 mm internal and 28 mm external diameter, Fig. 1b) or with a test tube of similar diameter. The area of the resulted mini-agar-disc of 25 mm diameter was kept such (about 1/10th of the normal plate) that the ratio of the colony-bearing area to the inoculm remained the same as on big plates in spread-plate-method (Table 2). In normal Petri dishes (about 90 mm diameter) up to seven mini agar discs were possible to cut. Each small agar disc was seperated from the other mini-disc by a distance of at least 6 mm (Fig. 1a). The empty place around the disc was still enlarged during over drying of the plates and during incubation. This created complete isolation from the neighbouring disc. For micro-determination of surface viable counts 10 micronl from each dilution was delivered on a well-dired mini-disc with a piston micropipette. The inoculm was immediately spread on the whole mini-disc with a specially designed flame sterilizable platinum-Mini-spreader (Fig. 2a). No spinning of the plate was needed. Alternatively the dropping pipette and spreader was replaced by a calibrated platinum wire Loop-spreader (Fig. 2b). A loop of 3 mm internal diameter made from a platinum-iridium wire of 0.75 mm thickness proved most useful and carried a drop of 10 micronl. Differences especially in surface tension of various diluting fluids did not influence to drop of this size and no recalibration was needed for water and nutrient broth. The loop was further shaped to Loop-spreader form. From each bacterial suspension 10 micronl were carried and spread on each mini-disc. The method is useful for pathogenic organisms as the loop can readily be flame sterilized. For routine purposes where only approximate numbers of bacteria need to be known a still rapid semiquantitative method was deviced making use of a calibrated stainless steel Stamping-disc (Fig. 2c). A disc of 25mm diameter and 1 mm thickness delivered approximateyl 10 microlitres of supensions and was found to be most useful to stamp seven dilutions on a single plate. In collections and bacteriology laboratories where by conventional methods large number of plates are to be plated and counted the presented techniques could prove most convenient, rapid and economical.

Organotypic three-dimensional assays based on human leiomyoma–derived matrices

PubMed Central

Dourado, Mauricio Rocha; Sundquist, Elias; Apu, Ehsanul Hoque; Alahuhta, Ilkka; Tuomainen, Katja; Vasara, Jenni; Al-Samadi, Ahmed

2018-01-01

Alongside cancer cells, tumours exhibit a complex stroma containing a repertoire of cells, matrix molecules and soluble factors that actively crosstalk between each other. Recognition of this multifaceted concept of the tumour microenvironment (TME) calls for authentic TME mimetics to study cancer in vitro. Traditionally, tumourigenesis has been investigated in non-human, three-dimensional rat type I collagen containing organotypic discs or by means of mouse sarcoma-derived gel, such as Matrigel®. However, the molecular compositions of these simplified assays do not properly simulate human TME. Here, we review the main properties and benefits of using human leiomyoma discs and their matrix Myogel for in vitro assays. Myoma discs are practical for investigating the invasion of cancer cells, as are cocultures of cancer and stromal cells in a stiff, hypoxic TME mimetic. Myoma discs contain soluble factors and matrix molecules commonly present in neoplastic stroma. In Transwell, IncuCyte, spheroid and sandwich assays, cancer cells move faster and form larger colonies in Myogel than in Matrigel®. Additionally, Myogel can replace Matrigel® in hanging-drop and tube-formation assays. Myogel also suits three-dimensional drug testing and extracellular vesicle interactions. To conclude, we describe the application of our myoma-derived matrices in 3D in vitro cancer assays. This article is part of the discussion meeting issue ‘Extracellular vesicles and the tumour microenvironment’. PMID:29158312

Organotypic three-dimensional assays based on human leiomyoma-derived matrices.

PubMed

Salo, Tuula; Dourado, Mauricio Rocha; Sundquist, Elias; Apu, Ehsanul Hoque; Alahuhta, Ilkka; Tuomainen, Katja; Vasara, Jenni; Al-Samadi, Ahmed

2018-01-05

Alongside cancer cells, tumours exhibit a complex stroma containing a repertoire of cells, matrix molecules and soluble factors that actively crosstalk between each other. Recognition of this multifaceted concept of the tumour microenvironment (TME) calls for authentic TME mimetics to study cancer in vitro Traditionally, tumourigenesis has been investigated in non-human, three-dimensional rat type I collagen containing organotypic discs or by means of mouse sarcoma-derived gel, such as Matrigel ® However, the molecular compositions of these simplified assays do not properly simulate human TME. Here, we review the main properties and benefits of using human leiomyoma discs and their matrix Myogel for in vitro assays. Myoma discs are practical for investigating the invasion of cancer cells, as are cocultures of cancer and stromal cells in a stiff, hypoxic TME mimetic. Myoma discs contain soluble factors and matrix molecules commonly present in neoplastic stroma. In Transwell, IncuCyte, spheroid and sandwich assays, cancer cells move faster and form larger colonies in Myogel than in Matrigel ® Additionally, Myogel can replace Matrigel ® in hanging-drop and tube-formation assays. Myogel also suits three-dimensional drug testing and extracellular vesicle interactions. To conclude, we describe the application of our myoma-derived matrices in 3D in vitro cancer assays.This article is part of the discussion meeting issue 'Extracellular vesicles and the tumour microenvironment'. © 2017 The Authors.

Segmentation of optic disc and optic cup in retinal fundus images using shape regression.

PubMed

Sedai, Suman; Roy, Pallab K; Mahapatra, Dwarikanath; Garnavi, Rahil

2016-08-01

Glaucoma is one of the leading cause of blindness. The manual examination of optic cup and disc is a standard procedure used for detecting glaucoma. This paper presents a fully automatic regression based method which accurately segments optic cup and disc in retinal colour fundus image. First, we roughly segment optic disc using circular hough transform. The approximated optic disc is then used to compute the initial optic disc and cup shapes. We propose a robust and efficient cascaded shape regression method which iteratively learns the final shape of the optic cup and disc from a given initial shape. Gradient boosted regression trees are employed to learn each regressor in the cascade. A novel data augmentation approach is proposed to improve the regressors performance by generating synthetic training data. The proposed optic cup and disc segmentation method is applied on an image set of 50 patients and demonstrate high segmentation accuracy for optic cup and disc with dice metric of 0.95 and 0.85 respectively. Comparative study shows that our proposed method outperforms state of the art optic cup and disc segmentation methods.

[The Autocad system for planimetric study of the optic disc in glaucoma: technique and reproducibility study].

PubMed

Sánchez Pérez, A; Honrubia López, F M; Larrosa Poves, J M; Polo Llorens, V; Melcon Sánchez-Frieras, B

2001-09-01

To develop a lens planimetry technique for the optic disc using AutoCAD. To determine variability magnitude of the optic disc morphological measurements. We employed AutoCAD R.14.0 Autodesk: image acquisition, contour delimitation by multiple lines fitting or ellipse adjustment, image sectorialization and measurements quantification (optic disc and excavation, vertical diameters, optic disc area, excavation area, neuroretinal sector area and Beta atrophy area). Intraimage or operator and interimage o total reproducibility was studied by coefficient of variability (CV) (n=10) in normal and myopic optic discs. This technique allows to obtain optic disc measurement in 5 to 10 minutes time. Total or interimage variability of measurements introduced by one observer presents CV range from 1.18-4.42. Operator or intraimage measurement presents CV range from 0.30-4.21. Optic disc contour delimitation by ellipse adjustment achieved better reproducibility results than multiple lines adjustment in all measurements. Computer assisted AutoCAD planimetry is an interactive method to analyse the optic disc, feasible to incorporate to clinical practice. Reproducibility results are comparable to other analyzers in quantification optic disc morphology. Ellipse adjustment improves results in optic disc contours delimitation.

BP Piscium: its flaring disc imaged with SPHERE/ZIMPOL★

NASA Astrophysics Data System (ADS)

de Boer, J.; Girard, J. H.; Canovas, H.; Min, M.; Sitko, M.; Ginski, C.; Jeffers, S. V.; Mawet, D.; Milli, J.; Rodenhuis, M.; Snik, F.; Keller, C. U.

2017-03-01

Whether BP Piscium (BP Psc) is either a pre-main sequence T Tauri star at d ≈ 80 pc, or a post-main sequence G giant at d ≈ 300 pc is still not clear. As a first-ascent giant, it is the first to be observed with a molecular and dust disc. Alternatively, BP Psc would be among the nearest T Tauri stars with a protoplanetary disc (PPD). We investigate whether the disc geometry resembles typical PPDs, by comparing polarimetric images with radiative transfer models. Our Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE)/Zurich IMaging Polarimeter (ZIMPOL) observations allow us to perform polarimetric differential imaging, reference star differential imaging, and Richardson-Lucy deconvolution. We present the first visible light polarization and intensity images of the disc of BP Psc. Our deconvolution confirms the disc shape as detected before, mainly showing the southern side of the disc. In polarized intensity the disc is imaged at larger detail and also shows the northern side, giving it the typical shape of high-inclination flared discs. We explain the observed disc features by retrieving the large-scale geometry with MCMAX radiative transfer modelling, which yields a strongly flared model, atypical for discs of T Tauri stars.

MRI evaluation of spontaneous intervertebral disc degeneration in the alpaca cervical spine.

PubMed

Stolworthy, Dean K; Bowden, Anton E; Roeder, Beverly L; Robinson, Todd F; Holland, Jacob G; Christensen, S Loyd; Beatty, Amanda M; Bridgewater, Laura C; Eggett, Dennis L; Wendel, John D; Stieger-Vanegas, Susanne M; Taylor, Meredith D

2015-12-01

Animal models have historically provided an appropriate benchmark for understanding human pathology, treatment, and healing, but few animals are known to naturally develop intervertebral disc degeneration. The study of degenerative disc disease and its treatment would greatly benefit from a more comprehensive, and comparable animal model. Alpacas have recently been presented as a potential large animal model of intervertebral disc degeneration due to similarities in spinal posture, disc size, biomechanical flexibility, and natural disc pathology. This research further investigated alpacas by determining the prevalence of intervertebral disc degeneration among an aging alpaca population. Twenty healthy female alpacas comprised two age subgroups (5 young: 2-6 years; and 15 older: 10+ years) and were rated according to the Pfirrmann-grade for degeneration of the cervical intervertebral discs. Incidence rates of degeneration showed strong correlations with age and spinal level: younger alpacas were nearly immune to developing disc degeneration, and in older animals, disc degeneration had an increased incidence rate and severity at lower cervical levels. Advanced disc degeneration was present in at least one of the cervical intervertebral discs of 47% of the older alpacas, and it was most common at the two lowest cervical intervertebral discs. The prevalence of intervertebral disc degeneration encourages further investigation and application of the lower cervical spine of alpacas and similar camelids as a large animal model of intervertebral disc degeneration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Patterns of lumbar disc degeneration are different in degenerative disc disease and disc prolapse magnetic resonance imaging analysis of 224 patients.

PubMed

Kanna, Rishi M; Shetty, Ajoy Prasad; Rajasekaran, S

2014-02-01

Existing research on lumbar disc degeneration has remained inconclusive regarding its etiology, pathogenesis, symptomatology, prevention, and management. Degenerative disc disease (DDD) and disc prolapse (DP) are common diseases affecting the lumbar discs. Although they manifest clinically differently, existing studies on disc degeneration have included patients with both these features, leading to wide variations in observations. The possible relationship or disaffect between DDD and DP is not fully evaluated. To analyze the patterns of lumbar disc degeneration in patients with chronic back pain and DDD and those with acute DP. Prospective, magnetic resonance imaging-based radiological study. Two groups of patients (aged 20-50 years) were prospectively studied. Group 1 included patients requiring a single level microdiscectomy for acute DP. Group 2 included patients with chronic low back pain and DDD. Discs were assessed by magnetic resonance imaging through Pfirmann grading, Schmorl nodes, Modic changes, and the total end-plate damage score for all the five lumbar discs. Group 1 (DP) had 91 patients and group 2 (DDD) had 133 patients. DP and DDD patients differed significantly in the number, extent, and severity of degeneration. DDD patients had a significantly higher number of degenerated discs than DP patients (p<.000). The incidence of multilevel and pan-lumbar degeneration was also significantly higher in DDD group. The pattern of degeneration also differed in both the groups. DDD patients had predominant upper lumbar involvement, whereas DP patients had mainly lower lumbar degeneration. Modic changes were more common in DP patients, especially at the prolapsed level. Modic changes were present in 37% of prolapsed levels compared with 9.9% of normal discs (p<.00). The total end-plate damage score had a positive correlation with disc degeneration in both the groups. Further the mean total end-plate damage score at prolapsed level was also significantly higher. The results suggest that patients with disc prolapse, and those with back pain with DDD are clinically and radiologically different groups of patients with varying patterns, severity, and extent of disc degeneration. This is the first study in literature to compare and identify significant differences in these two commonly encountered patient groups. In patients with single-level DP, the majority of the other discs are nondegenerate, the lower lumbar spine is predominantly involved and the end-plate damage is higher. Patients with back pain and DDD have larger number of degenerate discs, early multilevel degeneration, and predominant upper lumbar degeneration. The knowledge that these two groups of patients are different clinically and radiologically is critical for our improved understanding of the disease and for future studies on disc degeneration and disc prolapse. Copyright © 2014 Elsevier Inc. All rights reserved.

Stress in Lumbar Intervertebral Discs during Distraction

PubMed Central

Gay, Ralph E.; Ilharreborde, Brice; Zhao, Kristin D.; Berglund, Lawrence J.; Bronfort, Gert; An, Kai-Nan

2008-01-01

BACKGROUND CONTEXT The intervertebral disc is a common source of low back pain. Prospective studies suggest that treatments that intermittently distract the disc might be beneficial for chronic low back pain. Although the potential exists for distraction therapies to affect the disc biomechanically their effect on intradiscal stress is debated. PURPOSE To determine if distraction alone, distraction combined with flexion or distraction combined with extension can reduce nucleus pulposus pressure and posterior anulus compressive stress in cadaveric lumbar discs compared to simulated standing or lying. STUDY DESIGN Laboratory study using single cadaveric motion segments. OUTCOME MEASURES Strain gauge measures of nucleus pulposus pressure and compressive stress in the anterior and posterior annulus fibrosus METHODS Intradiscal stress profilometry was performed on 15 motion segments during 5 simulated conditions: standing, lying, and 3 distracted conditions. Disc degeneration was graded by inspection from 1 (normal) to 4 (severe degeneration). RESULTS All distraction conditions markedly reduced nucleus pressure compared to either simulated standing or lying. There was no difference between distraction with flexion and distraction with extension in regard to posterior annulus compressive stress. Discs with little or no degeneration appeared to distributed compressive stress differently than those with moderate or severe degeneration. CONCLUSIONS Distraction appears to predictably reduce nucleus pulposus pressure. The effect of distraction therapy on the distribution of compressive stress may be dependent in part on the health of the disc. PMID:17981092

Incidence and rates of visual field progression after longitudinally measured optic disc change in glaucoma.

PubMed

Chauhan, Balwantray C; Nicolela, Marcelo T; Artes, Paul H

2009-11-01

To determine whether glaucoma patients with progressive optic disc change have subsequent visual field progression earlier and at a faster rate compared with those without disc change. Prospective, longitudinal, cohort study. Eighty-one patients with open-angle glaucoma. Patients underwent confocal scanning laser tomography and standard automated perimetry every 6 months. The complete follow-up was divided into initial and subsequent periods. Two initial periods-first 3 years (Protocol A) and first half of the total follow-up (Protocol B)-were used, with the respective remainder being the subsequent follow-up. Disc change during the initial follow-up was determined with liberal, moderate, or conservative criteria of the Topographic Change Analysis. Subsequent field progression was determined with significant pattern deviation change in >or=3 locations (criterion used in the Early Manifest Glaucoma Trial). As a control analysis, field change during the initial follow-up was determined with significant pattern deviation change in >or=1, >or=2, or >or=3 locations. Survival time to subsequent field progression, rates of mean deviation (MD) change, and positive and negative likelihood ratios. The median (interquartile range) total follow-up was 11.0 (8.0-12.0) years with 22 (18-24) examinations. More patients had disc changes during the initial follow-up compared with field changes. The mean time to field progression was consistently shorter (protocol A, 0.8-1.7 years; protocol B, 0.3-0.7 years) in patients with prior disc change. In the control analysis, patients with prior field change had statistically earlier subsequent field progression (protocol A, 2.9-3.0 years; protocol B, 0.7-0.9). Similarly, patients with either prior disc or field change always had worse mean rates of subsequent MD change, although the distributions overlapped widely. Patients with subsequent field progression were up to 3 times more likely to have prior disc change compared with those without, and up to 5 times more likely to have prior field change compared with those without. Longitudinally measured optic disc change is predictive of subsequent visual field progression and may be an efficacious end point for functional outcomes in clinical studies and trials in glaucoma.

Differences in Optical Coherence Tomography Assessment of Bruch Membrane Opening Compared to Stereoscopic Photography for Estimating Cup-to-Disc Ratio.

PubMed

Mwanza, Jean-Claude; Huang, Linda Y; Budenz, Donald L; Shi, Wei; Huang, Gintien; Lee, Richard K

2017-12-01

To compare the vertical and horizontal cup-to-disc ratio (VCDR, HCDR) by an updated optical coherence tomography (OCT) Bruch membrane opening (BMO) algorithm and stereoscopic optic disc photograph readings by glaucoma specialists. Reliability analysis. A total of 195 eyes (116 glaucoma and 79 glaucoma suspect) of 99 patients with stereoscopic photographs and OCT scans of the optic discs taken during the same visit were compared. Optic disc photographs were read by 2 masked glaucoma specialists for VCDR and HCDR estimation. Intraclass correlation coefficient (ICC) and Bland-Altman plots were used to assess the agreement between photograph reading and OCT in estimating CDR. OCT images computed significantly larger VCDR and HCDR than photograph reading before and after stratifying eyes based on disc size (P < .001). The difference in CDR estimates between the 2 methods was equal to or greater than 0.2 in 29% and 35% of the eyes for VCDR and HCDR, respectively, with a mean difference of 0.3 in each case. The ICCs between the readers and OCT ranged between 0.50 and 0.63. The size of disagreement in VCDR correlated weakly with cup area in eyes with medium (r 2  = 0.10, P = .008) and large (r 2  = 0.09, P = .007) discs. OCT and photograph reading by clinicians agree poorly in CDR assessment. The difference in VCDR between the 2 methods was depended on cup area in medium and large discs. These differences should be considered when making conclusions regarding CDRs in clinical practice. Copyright © 2017 Elsevier Inc. All rights reserved.

Peripapillary choroidal thickness in healthy controls and patients with focal, diffuse, and sclerotic glaucomatous optic disc damage.

PubMed

Roberts, Kenneth F; Artes, Paul H; O'Leary, Neil; Reis, Alexandre S C; Sharpe, Glen P; Hutchison, Donna M; Chauhan, Balwantray C; Nicolela, Marcelo T

2012-08-01

To examine peripapillary choroidal thickness in healthy controls and in patients with glaucoma who have focal, diffuse, and sclerotic optic disc damage. Healthy controls (n=92) and patients with glaucoma who have focal (n=34), diffuse (n=35), and sclerotic (n=34) optic disc damage were imaged with spectral-domain optical coherence tomography (12° circular scan protocol centered on optic nerve head). Peripapillary choroidal thickness was measured as the distance between the automatically segmented retinal pigment epithelium/Bruch's membrane and the manually outlined interface between the posterior choroid and the anterior border of the sclera in eyes in which the anterior scleral border was visible over more than 85% of the scan circumference. The anterior scleral border was visible in 76 controls (83%) and 89 patients (86%). Peripapillary choroidal thickness in healthy controls decreased linearly with age (-11 μm/decade; P.001; r2=0.16), with a predicted value of 137 μm at age 70 years (95% prediction interval, 62-212 μm). While this value was similar in patients with focal and diffuse optic disc damage (126 and 130 μm, respectively; P=.22 compared with controls), it was approximately 30% lower in patients with sclerotic optic disc damage (96 μm; P.001 compared with controls). The peripapillary choroid of patients with glaucoma who have sclerotic optic disc damage was approximately 25% to 30% thinner compared with that in patients with focal and diffuse optic disc damage and with that in healthy controls. The role of the choroid in the pathophysiology of sclerotic glaucomatous optic disc damage needs further investigation.

What is the superior surgical strategy for bi-level cervical spondylosis-anterior cervical disc replacement or anterior cervical decompression and fusion?: A meta-analysis from 11 studies.

PubMed

Zhao, He; Duan, Li-Jun; Gao, Yu-Shan; Yang, Yong-Dong; Tang, Xiang-Sheng; Zhao, Ding-Yan; Xiong, Yang; Hu, Zhen-Guo; Li, Chuan-Hong; Yu, Xing

2018-03-01

Nowadays, anterior cervical artificial disc replacement (ACDR) has achieved favorable outcomes in treatment for patients with single-level cervical spondylosis. However, It is still controversial that whether or not it will become a potent therapeutic alternation in treating 2 contiguous levels cervical spondylosis compared with anterior cervical decompression and fusion (ACDF). Therefore, we conducted a systematic review and meta-analysis to compare the efficacy and safety of ACDR and ACDF in patients with 2 contiguous levels cervical spondylosis. According to the computer-based online search, PubMed, Embase, Web of Science, and Cochrane Library for articles published before July 1, 2017 were searched. The following outcome measures were extracted: neck disability index (NDI), visual analog scale (VAS) neck, VAS arm, Short Form (SF)-12 mental component summary (MCS), SF-12 physical component summary (PCS), overall clinical success (OCS), patient satisfaction (PS), device-related adverse event (DRAE), subsequent surgical intervention (SSI), neurological deterioration (ND), and adjacent segment degeneration (ASD). Methodological quality was evaluated independently by 2 reviewers using the Furlan for randomized controlled trial (RCT) and MINORS scale for clinical controlled trials (CCT). The chi-squared test and Higgin I test were used to evaluate the heterogeneity. A P < .10 for the chi-squared test or I values exceeding 50% indicated substantial heterogeneity and a random-effect model was applied; otherwise, a fixed-effect model was used. All quantitative data were analyzed by the Review Manager 5.2 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). Nine RCTs and 2 CCT studies containing 2715 patients were included for this meta-analysis. The pooled analysis indicated that the ACDR group is superior to ACDF in NDI, VAS neck, PCS score, OCS, PS, DRAE, ASD, and SSI. However, the pooled results indicate that there was no significant difference in the ND, VAS arm and in MCS score. The present meta-analysis suggests that for bi-level cervical spondylosis, ACDR appears to provide superior clinical effectiveness and safety effects than ACDF. In the future, more high-quality RCTs are warranted to enhance this conclusion.

How do accretion discs break?

NASA Astrophysics Data System (ADS)

Dogan, Suzan

2016-07-01

Accretion discs are common in binary systems, and they are often found to be misaligned with respect to the binary orbit. The gravitational torque from a companion induces nodal precession in misaligned disc orbits. In this study, we first calculate whether this precession is strong enough to overcome the internal disc torques communicating angular momentum. We compare the disc precession torque with the disc viscous torque to determine whether the disc should warp or break. For typical parameters precession wins: the disc breaks into distinct planes that precess effectively independently. To check our analytical findings, we perform 3D hydrodynamical numerical simulations using the PHANTOM smoothed particle hydrodynamics code, and confirm that disc breaking is widespread and enhances accretion on to the central object. For some inclinations, the disc goes through strong Kozai cycles. Disc breaking promotes markedly enhanced and variable accretion and potentially produces high-energy particles or radiation through shocks. This would have significant implications for all binary systems: e.g. accretion outbursts in X-ray binaries and fuelling supermassive black hole (SMBH) binaries. The behaviour we have discussed in this work is relevant to a variety of astrophysical systems, for example X-ray binaries, where the disc plane may be tilted by radiation warping, SMBH binaries, where accretion of misaligned gas can create effectively random inclinations and protostellar binaries, where a disc may be misaligned by a variety of effects such as binary capture/exchange, accretion after binary formation.

Utility of Digital Stereo Images for Optic Disc Evaluation

PubMed Central

Ying, Gui-shuang; Pearson, Denise J.; Bansal, Mayank; Puri, Manika; Miller, Eydie; Alexander, Judith; Piltz-Seymour, Jody; Nyberg, William; Maguire, Maureen G.; Eledath, Jayan; Sawhney, Harpreet

2010-01-01

Purpose. To assess the suitability of digital stereo images for optic disc evaluations in glaucoma. Methods. Stereo color optic disc images in both digital and 35-mm slide film formats were acquired contemporaneously from 29 subjects with various cup-to-disc ratios (range, 0.26–0.76; median, 0.475). Using a grading scale designed to assess image quality, the ease of visualizing optic disc features important for glaucoma diagnosis, and the comparative diameters of the optic disc cup, experienced observers separately compared the primary digital stereo images to each subject's 35-mm slides, to scanned images of the same 35-mm slides, and to grayscale conversions of the digital images. Statistical analysis accounted for multiple gradings and comparisons and also assessed image formats under monoscopic viewing. Results. Overall, the quality of primary digital color images was judged superior to that of 35-mm slides (P < 0.001), including improved stereo (P < 0.001), but the primary digital color images were mostly equivalent to the scanned digitized images of the same slides. Color seemingly added little to grayscale optic disc images, except that peripapillary atrophy was best seen in color (P < 0.0001); both the nerve fiber layer (P < 0.0001) and the paths of blood vessels on the optic disc (P < 0.0001) were best seen in grayscale. The preference for digital over film images was maintained under monoscopic viewing conditions. Conclusions. Digital stereo optic disc images are useful for evaluating the optic disc in glaucoma and allow the application of advanced image processing applications. Grayscale images, by providing luminance distinct from color, may be informative for assessing certain features. PMID:20505199

A Systematic Review of the Safety and Efficacy of Mesenchymal Stem Cells for Disc Degeneration: Insights and Future Directions for Regenerative Therapeutics

PubMed Central

Yim, Rita Lok-Hay; Lee, Juliana Tsz-Yan; Bow, Cora H.; Meij, Björn; Leung, Victor; Cheung, Kenneth M.C.; Vavken, Patrick

2014-01-01

Intervertebral disc degeneration is associated with low-back pain. Mesenchymal stem cells (MSCs) have been used to “regenerate” the disc. The aim of this study was to perform a systematic review of comparative controlled studies that have assessed the safety and efficacy of using MSCs for disc regeneration. Literature databases were extensively searched. Trial design, subject-type, MSC sources, injection method, disc assessment, outcome intervals, and complication events were assessed. Validity of each study was performed. Twenty-four animal studies were included with 20.8% of the studies reporting randomization of groups. Trials in humans fulfilling inclusion criteria were not noted. The studies represented 862 discs that were injected with MSCs and 1,603 discs as controls. All three types of MSCs (ie, bone marrow, synovial, and adipose tissues) showed successful inhibition of disc degeneration. Bone-marrow-derived MSCs demonstrated superior quality of repair compared with other non-MSC treatments. A 2.7% overall complication rate was noted, whereby complications were noted only in rabbits. Overall, evidence suggested that MSCs increased disc space height in the majority of animal models. This is the first systematic review to assess the safety and efficacy of MSCs for the treatment of disc degeneration. Short-term MSC transplantation is safe and effective; however, additional, larger, and higher-quality studies are needed to assess the long-term safety and efficacy. Inconsistencies in methodological design and outcome parameters prevent any robust conclusions. Human-based clinical trials are needed. Recommendations are further made to improve efficacy, reduce potential complications, and standardize techniques for future studies. PMID:25050446

The effect of parental factors in children with large cup-to-disc ratios.

PubMed

Park, Hae-Young Lopilly; Ha, Min Ji; Shin, Sun Young

2017-01-01

To investigate large cup-to-disc ratios (CDR) in children and to determine the relationship between parental CDR and clinical characteristics associated with glaucoma. Two hundred thirty six children aged 6 to 12 years with CDR ≥ 0.6 were enrolled in this study. Subjects were classified into two groups based on parental CDR: disc suspect children with disc suspect (CDR ≥0.6) parents and disc suspect children without disc suspect parents. Ocular variables were compared between the two groups. Of the 236 disc suspect children, 100 (42.4%) had at least one disc suspect parent. Intraocular pressure (IOP) was higher in disc suspect children with disc suspect parents (16.52±2.66 mmHg) than in disc suspect children without disc suspect parents (14.38±2.30 mmHg, p = 0.023). In the group with disc suspect parents, vertical CDR significantly correlated with IOP (R = -0.325, p = 0.001), average retinal nerve fiber layer (RNFL) thickness (R = -0.319, p = 0.001), rim area (R = -0.740, p = 0.001), and cup volume (R = 0.499, p = 0.001). However, spherical equivalent (R = 0.333, p = 0.001), AL (R = -0.223, p = 0.009), and disc area (R = 0.325, p = 0.001) significantly correlated with vertical CDR in disc suspect children without disc suspect parents, in contrast to those with disc suspect parents. Larger vertical CDR was associated with the presence of disc suspect parents (p = 0.001), larger disc area (p = 0.001), thinner rim area (p = 0.001), larger average CDR (p = 0.001), and larger cup volume (p = 0.021). Family history of large CDR was a significant factor associated with large vertical CDR in children. In children with disc suspect parents, there were significant correlations between IOP and average RNFL thickness and vertical CDR.

Sports Medicine and Rehabilitation Team Clinic: Comparative Model Analysis of Navy and Marine Corps Options

DTIC Science & Technology

2003-05-01

Spondylosis of unspecified site BARI Brown Field OCS 19 722.1 Lumbar invertebral disc without myelopathy (spine) BARI Brown Field OCS 1 722.52 Lumbar or...lumbosacral invertebral disc (spine) BARI Brown Field OCS 1 722.93 Other & unspecified disc disorder, Lumbar region BARI Brown Field OCS 8 723.4 Other...TBS 1 �.9 Spondylosis of unspecified site BARJ Ray Hall TBS 19 722 Displacement of cervical invertebral disc without myelopathy (spine) BARJ Ray Hall

Lumbar spine intervertebral disc gene delivery: a pilot study in lewis rats.

PubMed

Damle, Sheela R; Rawlins, Bernard A; Boachie-Adjei, Oheneba; Crystal, Ronald G; Hidaka, Chisa; Cunningham, Matthew E

2013-02-01

Basic research toward understanding and treating disc pathology in the spine has utilized numerous animal models, with delivery of small molecules, purified factors, and genes of interest. To date, gene delivery to the rat lumbar spine has only been described utilizing genetically programmed cells in a matrix which has required partial disc excision, and expected limitation of treatment diffusion into the disc. This study was designed to develop and describe a surgical technique for lumbar spine exposure and disc space preparation, and use of a matrix-free method for gene delivery. Naïve or genetically programmed isogeneic bone marrow stromal cells were surgically delivered to adolescent male Lewis rat lumbar discs, and utilizing quantitative biochemical and qualitative immunohistological assessments, the implanted cells were detected 3 days post-procedure. Statistically significant differences were noted for recovery of the β-galactosidase marker gene comparing delivery of naïve or labeled cells (10(5) cells per disc) from the site of implantation, and between delivery of 10(5) or 10(6) labeled cells per disc at the site of implantation and the adjacent vertebral body. Immunohistology confirmed that the β-galactosidase marker was detected in the adjacent vertebra bone in the zone of surgical implantation. The model requires further testing in larger cohorts and with biologically active genes of interest, but the observations from the pilot experiments are very encouraging that this will be a useful comparative model for basic spine research involving gene or cell delivery, or other locally delivered therapies to the intervertebral disc or adjacent vertebral bodies in rats.

Optic disc size and other parameters from optical coherence tomography in Vietnamese-Americans.

PubMed

Peng, Pai-Huei; Fu, Sheena; Nguyen, Ngoc; Porco, Travis; Lin, Shan C

2011-08-01

To investigate the optic disc parameters by optical coherence tomography (OCT) in Vietnamese with various types of glaucoma. Medical charts of Vietnamese and White patients within a single practice were reviewed. Disc and rim areas by OCT were compared among nonglaucoma controls, different types of glaucoma, and glaucoma suspect. The association of these parameters with demographic and ocular features was evaluated. Data from 1416 Vietnamese and 57 White patients were included. A larger mean disc area was observed in eyes with primary angle-closure glaucoma than in eyes with primary angle-closure and primary angle-closure suspect (both P<0.001). There was no association between disc size with central corneal thickness (P=0.051) and sex (P=0.155). Vietnamese patients with glaucoma and glaucoma suspicion had larger discs than diagnosis-matched Whites (P=0.043 and 0.021, respectively). Vietnamese patients with glaucoma seem to have larger optic discs than White patients. Central corneal thickness had no association with disc area in this study population.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chillara, Vamshi Krishna; Pantea, Cristian; Sinha, Dipen N.

Here, we numerically investigate the resonance and vibration characteristics of radial modes of laterally stiffened piezoelectric disc transducers. Lateral stiffening is modeled using a spring and vibration characteristics of the piezo-disc are investigated with increasing lateral stiffness. It is found that the resonant frequency response of the radial modes follows an asymptotic behavior approaching that of a clamped disc with increasing lateral stiffness. The radial mode vibration pattern of the discs is also found to be affected by lateral stiffness. While the vibration pattern of a free disc corresponds to a Bessel function, laterally stiffened discs show edge-effects where theymore » depart from the Bessel-like behavior. In addition, a fully clamped piezo-disc is found to have an extra side-lobe when compared to a free disc. Ultrasonic beam profiles generated from radial modes of laterally stiffened discs are numerically investigated. It is found that the free piezo-disc generates a Bessel beam that has multiple side-lobes. Increasing the lateral stiffness results in a significant reduction of side-lobes in the beam profile. This technique of generating a collimated beam with side-lobe reduction finds significant applications in imaging through concrete, drilling mud, and other highly attenuating materials.« less

A rapid leaf-disc sampler for psychrometric water potential measurements.

PubMed

Wullschleger, S D; Oosterhuis, D M

1986-06-01

An instrument was designed which facilitates faster and more accurate sampling of leaf discs for psychrometric water potential measurements. The instrument consists of an aluminum housing, a spring-loaded plunger, and a modified brass-plated cork borer. The leaf-disc sampler was compared with the conventional method of sampling discs for measurement of leaf water potential with thermocouple psychrometers on a range of plant material including Gossypium hirsutum L., Zea mays L., and Begonia rex-cultorum L. The new sampler permitted a leaf disc to be excised and inserted into the psychrometer sample chamber in less than 7 seconds, which was more than twice as fast as the conventional method. This resulted in more accurate determinations of leaf water potential due to reduced evaporative water losses. The leaf-disc sampler also significantly reduced sample variability between individual measurements. This instrument can be used for many other laboratory and field measurements that necessitate leaf disc sampling.

Radial modes of laterally stiffened piezoelectric disc transducers for ultrasonic collimated beam generation

DOE PAGES

Chillara, Vamshi Krishna; Pantea, Cristian; Sinha, Dipen N.

2017-07-15

Here, we numerically investigate the resonance and vibration characteristics of radial modes of laterally stiffened piezoelectric disc transducers. Lateral stiffening is modeled using a spring and vibration characteristics of the piezo-disc are investigated with increasing lateral stiffness. It is found that the resonant frequency response of the radial modes follows an asymptotic behavior approaching that of a clamped disc with increasing lateral stiffness. The radial mode vibration pattern of the discs is also found to be affected by lateral stiffness. While the vibration pattern of a free disc corresponds to a Bessel function, laterally stiffened discs show edge-effects where theymore » depart from the Bessel-like behavior. In addition, a fully clamped piezo-disc is found to have an extra side-lobe when compared to a free disc. Ultrasonic beam profiles generated from radial modes of laterally stiffened discs are numerically investigated. It is found that the free piezo-disc generates a Bessel beam that has multiple side-lobes. Increasing the lateral stiffness results in a significant reduction of side-lobes in the beam profile. This technique of generating a collimated beam with side-lobe reduction finds significant applications in imaging through concrete, drilling mud, and other highly attenuating materials.« less

Planet-disc interaction in laminar and turbulent discs

NASA Astrophysics Data System (ADS)

Stoll, Moritz H. R.; Picogna, Giovanni; Kley, Wilhelm

2017-07-01

In weakly ionised discs turbulence can be generated through the vertical shear instability (VSI). Embedded planets are affected by a stochastic component in the torques acting on them, which can impact their migration. In this work we study the interplay between a growing planet embedded in a protoplanetary disc and the VSI turbulence. We performed a series of 3D hydrodynamical simulations for locally isothermal discs with embedded planets in the mass range from 5 to 100 Earth masses. We study planets embedded in an inviscid disc that is VSI unstable, becomes turbulent, and generates angular momentum transport with an effective α = 5 × 10-4. This is compared to the corresponding viscous disc using exactly this α-value. In general we find that the planets have only a weak impact on the disc turbulence. Only for the largest planet (100 M⊕) does the turbulent activity become enhanced inside of the planet. The depth and width of a gap created by the more massive planets (30,100 M⊕) in the turbulent disc equal exactly that of the corresponding viscous case, leading to very similar torque strengths acting on the planet, with small stochastic fluctuations for the VSI disc. At the gap edges vortices are generated that are stronger and longer-lived in the VSI disc. Low mass planets (with Mp ≤ 10 M⊕) do not open gaps in the disc in either case, but generate for the turbulent disc an overdensity behind the planet that exerts a significant negative torque. This can boost the inward migration in VSI turbulent discs well above the Type I rate. Owing to the finite turbulence level in realistic 3D discs the gap depth will always be limited and migration will not stall in inviscid discs.

The NEtherlands Cervical Kinematics (NECK) trial. Cost-effectiveness of anterior cervical discectomy with or without interbody fusion and arthroplasty in the treatment of cervical disc herniation; a double-blind randomised multicenter study.

PubMed

Arts, Mark P; Brand, Ronald; van den Akker, Elske; Koes, Bart W; Peul, Wilco C

2010-06-16

Patients with cervical radicular syndrome due to disc herniation refractory to conservative treatment are offered surgical treatment. Anterior cervical discectomy is the standard procedure, often in combination with interbody fusion. Accelerated adjacent disc degeneration is a known entity on the long term. Recently, cervical disc prostheses are developed to maintain motion and possibly reduce the incidence of adjacent disc degeneration. A comparative cost-effectiveness study focused on adjacent segment degeneration and functional outcome has not been performed yet. We present the design of the NECK trial, a randomised study on cost-effectiveness of anterior cervical discectomy with or without interbody fusion and arthroplasty in patients with cervical disc herniation. Patients (age 18-65 years) presenting with radicular signs due to single level cervical disc herniation lasting more than 8 weeks are included. Patients will be randomised into 3 groups: anterior discectomy only, anterior discectomy with interbody fusion, and anterior discectomy with disc prosthesis. The primary outcome measure is symptomatic adjacent disc degeneration at 2 and 5 years after surgery. Other outcome parameters will be the Neck Disability Index, perceived recovery, arm and neck pain, complications, re-operations, quality of life, job satisfaction, anxiety and depression assessment, medical consumption, absenteeism, and costs. The study is a randomised prospective multicenter trial, in which 3 surgical techniques are compared in a parallel group design. Patients and research nurses will be kept blinded of the allocated treatment for 2 years. The follow-up period is 5 years. Currently, anterior cervical discectomy with fusion is the golden standard in the surgical treatment of cervical disc herniation. Whether additional interbody fusion or disc prosthesis is necessary and cost-effective will be determined by this trial. Netherlands Trial Register NTR1289.

The NEtherlands Cervical Kinematics (NECK) Trial. Cost-effectiveness of anterior cervical discectomy with or without interbody fusion and arthroplasty in the treatment of cervical disc herniation; a double-blind randomised multicenter study

PubMed Central

2010-01-01

Background Patients with cervical radicular syndrome due to disc herniation refractory to conservative treatment are offered surgical treatment. Anterior cervical discectomy is the standard procedure, often in combination with interbody fusion. Accelerated adjacent disc degeneration is a known entity on the long term. Recently, cervical disc prostheses are developed to maintain motion and possibly reduce the incidence of adjacent disc degeneration. A comparative cost-effectiveness study focused on adjacent segment degeneration and functional outcome has not been performed yet. We present the design of the NECK trial, a randomised study on cost-effectiveness of anterior cervical discectomy with or without interbody fusion and arthroplasty in patients with cervical disc herniation. Methods/Design Patients (age 18-65 years) presenting with radicular signs due to single level cervical disc herniation lasting more than 8 weeks are included. Patients will be randomised into 3 groups: anterior discectomy only, anterior discectomy with interbody fusion, and anterior discectomy with disc prosthesis. The primary outcome measure is symptomatic adjacent disc degeneration at 2 and 5 years after surgery. Other outcome parameters will be the Neck Disability Index, perceived recovery, arm and neck pain, complications, re-operations, quality of life, job satisfaction, anxiety and depression assessment, medical consumption, absenteeism, and costs. The study is a randomised prospective multicenter trial, in which 3 surgical techniques are compared in a parallel group design. Patients and research nurses will be kept blinded of the allocated treatment for 2 years. The follow-up period is 5 years. Discussion Currently, anterior cervical discectomy with fusion is the golden standard in the surgical treatment of cervical disc herniation. Whether additional interbody fusion or disc prothesis is necessary and cost-effective will be determined by this trial. Trial Registration Netherlands Trial Register NTR1289 PMID:20553591

The AMBRE Project: r-process element abundances in the Milky Way thin and thick discs

NASA Astrophysics Data System (ADS)

Guiglion, Guillaume; de Laverny, Patrick; Recio-Blanco, Alejandra; Worley, C. Clare

2018-04-01

Chemical evolution of r-process elements in the Milky Way disc is still a matter of debate. We took advantage of high resolution HARPS spectra from the ESO archive in order to derive precise chemical abundances of 3 r-process elements Eu, Dy & Gd for a sample of 4 355 FGK Milky Way stars. The chemical analysis has been performed thanks to the automatic optimization pipeline GAUGUIN. Based on the [α/Fe] ratio, we chemically characterized the thin and the thick discs, and present here results of these 3 r-process element abundances in both discs. We found an unexpected Gadolinium and Dysprosium enrichment in the thick disc stars compared to Europium, while these three elements track well each other in the thin disc.

In vivo biofunctional evaluation of hydrogels for disc regeneration.

PubMed

Reitmaier, Sandra; Kreja, Ludwika; Gruchenberg, Katharina; Kanter, Britta; Silva-Correia, Joana; Oliveira, Joaquim Miguel; Reis, Rui Luís; Perugini, Valeria; Santin, Matteo; Ignatius, Anita; Wilke, Hans-Joachim

2014-01-01

Regenerative strategies aim to restore the original biofunctionality of the intervertebral disc. Different biomaterials are available, which might support disc regeneration. In the present study, the prospects of success of two hydrogels functionalized with anti-angiogenic peptides and seeded with bone marrow derived mononuclear cells (BMC), respectively, were investigated in an ovine nucleotomy model. In a one-step procedure iliac crest aspirates were harvested and, subsequently, separated BMC were seeded on hydrogels and implanted into the ovine disc. For the cell-seeded approach a hyaluronic acid-based hydrogel was used. The anti-angiogenic potential of newly developed VEGF-blockers was investigated on ionically crosslinked metacrylated gellan gum hydrogels. Untreated discs served as nucleotomy controls. 24 adult merino sheep were used. After 6 weeks histological, after 12 weeks histological and biomechanical analyses were conducted. Biomechanical tests revealed no differences between any of the implanted and nucleotomized discs. All implanted discs significantly degenerated compared to intact discs. In contrast, there was no marked difference between implanted and nucleotomized discs. In tendency, albeit not significant, degeneration score and disc height index deteriorated for all but not for the cell-seeded hydrogels from 6 to 12 weeks. Cell-seeded hydrogels slightly decelerated degeneration. None of the hydrogel configurations was able to regenerate biofunctionality of the intervertebral disc. This might presumably be caused by hydrogel extrusion. Great importance should be given to the development of annulus sealants, which effectively exploit the potential of (cell-seeded) hydrogels for biological disc regeneration and restoration of intervertebral disc functioning.

New Brown Dwarf Discs in Upper Scorpius Observed with WISE

NASA Technical Reports Server (NTRS)

Dawson, P.; Scholz, A.; Ray, T. P.; Natta, A.; Marsh, K. A.; Padgett, D.; Ressler, M. E.

2013-01-01

We present a census of the disc population for UKIDSS selected brown dwarfs in the 5-10 Myr old Upper Scorpius OB association. For 116 objects originally identified in UKIDSS, the majority of them not studied in previous publications, we obtain photometry from the Wide-Field Infrared Survey Explorer data base. The resulting colour magnitude and colour colour plots clearly show two separate populations of objects, interpreted as brown dwarfs with discs (class II) and without discs (class III). We identify 27 class II brown dwarfs, 14 of them not previously known. This disc fraction (27 out of 116, or 23%) among brown dwarfs was found to be similar to results for K/M stars in Upper Scorpius, suggesting that the lifetimes of discs are independent of the mass of the central object for low-mass stars and brown dwarfs. 5 out of 27 discs (19 per cent) lack excess at 3.4 and 4.6 microns and are potential transition discs (i.e. are in transition from class II to class III). The transition disc fraction is comparable to low-mass stars.We estimate that the time-scale for a typical transition from class II to class III is less than 0.4 Myr for brown dwarfs. These results suggest that the evolution of brown dwarf discs mirrors the behaviour of discs around low-mass stars, with disc lifetimes of the order of 5 10 Myr and a disc clearing time-scale significantly shorter than 1 Myr.

Percutaneous Endoscopic Cervical Discectomy (PECD): An Analysis of Outcome, Causes of Reoperation.

PubMed

Oh, Hyeong Seok; Hwang, Byeong-Wook; Park, Sang-Joon; Hsieh, Chang-Sheng; Lee, Sang-Ho

2017-06-01

Percutaneous endoscopic cervical discectomy (PECD) is regarded as an effective treatment modality in cervical disc herniation, including radicular pain and lateral location of disc herniation. This study aimed to evaluate the clinical and radiologic outcomes of PECD along with the causes of reoperation and the technique itself. Between January 2007 and November 2012, 101 patients underwent PECD at the Busan Wooridul Hospital. Three patients underwent a 2-level PECD. The mean follow-up period was 34 months (range, 18-72 months). The mean age was 46.1 years; the most common operation was at the C5-C6 level (n = 45), followed by C6-C7 (n = 35), C4-C5 (n = 16), and C3-C4 (n = 8). The clinical outcomes were evaluated via the visual analog scale of the neck and arm according to the Neck Disability Index and the modified Macnab criteria. Among 101 patients, 12 underwent an additional operation at the index level. Five patients had aggravated stenosis by disc height narrowing, 4 had recurred disc, 2 had remained disc, and 1 had sustained symptoms. After PECD, there was a significant improvement in the visual analog scale and Neck Disability Index scores (P < 0.001). According to the modified Macnab criteria, excellent concordance was achieved in 65 patients, good in 22, fair in 2, and poor in 12. The reoperation performed on 12 patients improved their clinical outcomes. The mean duration was 4.8 months (2 days to 18 months) until reoperation. There were 3 PECD revisions, 3 artificial disc replacements, 2 corpectomies, 2 anterior cervical discectomies and fusion with cages, and 2 transfers to another hospital. The common feature was older age (P = 0.016) and male sex (P = 0.031). Preoperative radiologic findings were characterized by the foraminal disc (P = 0.04), disc degeneration at the index level (P = 0.05), combined bony spur (P = 0.001), concomitant adjacent level degeneration (P = 0.019), cervical kyphosis (P = 0.015), and segmental angle deterioration after PECD (P = 0.038). No statistical correlation was seen between the operation level and herniation size (P > 0.05). In total, 87% patients showed successful clinical outcome. Poor and fair outcomes at initial PECD were overcome by revision surgery, which improved outcomes. Although PECD is a promising minimally invasive procedure for cervical disc treatment, the indications for PECD should be considered carefully. Copyright © 2017 Elsevier Inc. All rights reserved.

The Black Record: A Selective Discography of Afro-Americana on Audio Discs Held by the Audio/Visual Department, John M. Olin Library.

ERIC Educational Resources Information Center

Dain, Bernice, Comp.; Nevin, David, Comp.

The present revised and expanded edition of this document is an inclusive cumulation. A few items have been included which are on order as new to the collection or as replacements. This discography is intended to serve primarily as a local user's guide. The call number preceding each entry is based on the Audio-Visual Department's own, unique…

Lumbar spinal canal MRI diameter is smaller in herniated disc cauda equina syndrome patients

PubMed Central

Kruit, Mark C.; Peul, Wilco C.; Vleggeert-Lankamp, Carmen L. A.

2017-01-01

Introduction Correlation between magnetic resonance imaging (MRI) and clinical features in cauda equina syndrome (CES) is unknown; nor is known whether there are differences in MRI spinal canal size between lumbar herniated disc patients with CES versus lumbar herniated discs patients without CES, operated for sciatica. The aims of this study are 1) evaluating the association of MRI features with clinical presentation and outcome of CES and 2) comparing lumbar spinal canal diameters of lumbar herniated disc patients with CES versus lumbar herniated disc patients without CES, operated because of sciatica. Methods MRIs of CES patients were assessed for the following features: level of disc lesion, type (uni- or bilateral) and severity of caudal compression. Pre- and postoperative clinical features (micturition dysfunction, defecation dysfunction, altered sensation of the saddle area) were retrieved from the medical files. In addition, anteroposterior (AP) lumbar spinal canal diameters of CES patients were measured at MRI. AP diameters of lumbar herniated disc patients without CES, operated for sciatica, were measured for comparison. Results 48 CES patients were included. At MRI, bilateral compression was seen in 82%; complete caudal compression in 29%. MRI features were not associated with clinical presentation nor outcome. AP diameter was measured for 26 CES patients and for 31 lumbar herniated disc patients without CES, operated for sciatica. Comparison displayed a significant smaller AP diameter of the lumbar spinal canal in CES patients (largest p = 0.002). Compared to average diameters in literature, diameters of CES patients were significantly more often below average than that of the sciatica patients (largest p = 0.021). Conclusion This is the first study demonstrating differences in lumbar spinal canal size between lumbar herniated disc patients with CES and lumbar herniated disc patients without CES, operated for sciatica. This finding might imply that lumbar herniated disc patients with a relative small lumbar spinal canal might need to be approached differently in managing complaints of herniated disc. Since the number of studied patients is relatively small, further research should be conducted before clinical consequences are considered. PMID:29023556

Imaging of Herniated Discs of the Cervical Spine: Inter-Modality Differences between 64-Slice Multidetector CT and 1.5-T MRI

PubMed Central

Yi, Ji Sook; Han, Jong Kyu; Kim, Hyun-Joo

2015-01-01

Objective To assess inter-modality variability when evaluating cervical intervertebral disc herniation using 64-slice multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI). Materials and Methods Three musculoskeletal radiologists independently reviewed cervical spine 1.5-T MRI and 64-slice MDCT data on C2-3 though C6-7 of 51 patients in the context of intervertebral disc herniation. Interobserver and inter-modality agreements were expressed as unweighted kappa values. Weighted kappa statistics were used to assess the extents of agreement in terms of the number of involved segments (NIS) in disc herniation and epicenter measurements collected using MDCT and MRI. Results The interobserver agreement rates upon evaluation of disc morphology by the three radiologists were in fair to moderate agreement (k = 0.39-0.53 for MDCT images; k = 0.45-0.56 for MRIs). When the disc morphology was categorized into two and four grades, the inter-modality agreement rates were moderate (k-value, 0.59) and substantial (k-value, 0.66), respectively. The inter-modality agreements for evaluations of the NIS (k-value, 0.78) and the epicenter (k-value, 0.79) were substantial. Also, the interobserver agreements for the NIS (CT; k-value, 0.85 and MRI; k-value, 0.88) and epicenter (CT; k-value, 0.74 and MRI; k-value, 0.70) evaluations by two readers were substantial. MDCT tended to underestimate the extent of herniated disc lesions compared with MRI. Conclusion Multidetector-row computed tomography and MRI showed a moderate-to-substantial degree of inter-modality agreement for the assessment of herniated cervical discs. MDCT images have a tendency to underestimate the anterior/posterior extent of the herniated disc compared with MRI. PMID:26175589

Long-term Evaluation of Cervical Disc Arthroplasty with the Mobi-C© Cervical Disc: A Randomized, Prospective, Multicenter Clinical Trial with Seven-Year Follow-up.

PubMed

Radcliff, Kris; Davis, Reginald J; Hisey, Michael S; Nunley, Pierce D; Hoffman, Gregory A; Jackson, Robert J; Bae, Hyun W; Albert, Todd; Coric, Dom

2017-01-01

Cervical total disc replacement (TDR) is an increasingly accepted procedure for the treatment of symptomatic cervical degenerative disc disease. Multiple Level I evidence clinical trials have established cervical TDR to be a safe and effective procedure in the short-term. The objective of this study is to provide a long-term assessment of TDR versus anterior discectomy and fusion for the treatment of one- and two-level disc disease. This study was a continuation of a prospective, multicenter, randomized, US FDA IDE clinical trial comparing cervical TDR with the Mobi-C © Cervical Disc versus ACDF through 7 years follow-up. Inclusion criteria included a diagnosis of symptomatic cervical degenerative disc disease at one or two cervical levels. TDR patients were treated using a Mobi-C © artificial disc (Zimmer Biomet, Austin TX, USA). ACDF with allograft and anterior plate was used as a control treatment. Outcome measures were collected preoperatively and postoperatively at 6 weeks, at 3, 6, 12, 18 months, annually through 60 months, and at 84 months. Measured outcomes included Overall success, Neck Disability Index (NDI), VAS neck and arm pain, segmental range of motion (ROM), patient satisfaction, SF-12 MCS/PCS, major complications, and subsequent surgery rate. The primary endpoint was an FDA composite definition of success comprising clinical improvement and an absence of major complications and secondary surgery events. A total of 599 patients were enrolled and treated, with 164 treated with one-level TDR, 225 treated with two-level TDR, 81 treated with one-level ACDF, and 105 treated with two-level ACDF. At seven years, follow-up rates ranged from 73.5% to 84.4% (overall 80.2%).The overall success rates of two level TDR and ACDF patients were 60.8% and 34.2%, respectively (p<0.0001). The overall success rates of one level TDR and ACDF patients were 55.2% and 50%, respectively (p>0.05). Both the single and two level TDR and ACDF groups showed significant improvement from baseline NDI scores, VAS neck and arm pain scores, and SF-12 MCS/PCS scores (p<0.0001). In the single level cohort, there was an increased percentage of TDR patients who reported themselves as "very satisfied" (TDR 90.9% vs ACDF 77.8%; p= 0.028). There was a lower rate of adjacent level secondary surgery in the single level TDR patients (3.7%) versus the ACDF patients (13.6%; p = 0.007).In the two level TDR group, the NDI success rate was significantly greater in the TDR group (TDR: 79.0% vs. ACDF: 58.0%; p=0.001). There was significantly more improvement in NDI change score at 7 years in the TDR patients versus ACDF. The TDR group had a significantly higher rate of patients who were "very satisfied" with their treatment compared to the ACDF group (TDR: 85.9% vs. ACDF: 73.9%). The rate of subsequent surgery at the index level was significantly lower in the TDR group compared to the ACDF group (TDR: 4.4% vs. ACDF: 16.2%; p=0.001). The rate of adjacent level secondary surgery was significantly lower in the two level TDR (4.4%) patients compared to the ACDF (11.3%; p=0.03) patients. In both single and two level cohorts, the percentage of patients with worse NDI (2.5%-3.8% of two level surgeries and 1.2%-2.5% of single level surgeries) or worse neck pain (5%-6.8% of the two level surgeries and 1.3% - 3.8% of the single level surgeries) was strikingly low in both groups but trended lower in the TDR patients. At seven years, the composite success analysis demonstrated clinical superiority of two level TDR over ACDF and non-inferiority of single level TDR versus ACDF. There were lower rates of secondary surgery and higher adjacent level disc survivorship in both groups. Both surgeries were remarkably effective in alleviating pain relative to baseline and the rate of patients with worse disability or neck pain was surprisingly low. Overall, greater than 95% of patients (from both groups) who underwent TDR and 88% of patients who underwent ACDF were "very satisfied" at seven years. The differences in clinical effectiveness of TDR versus ACDF becomes more apparent as treatment increases from one to two levels, indicating a significant benefit for TDR over ACDF for two-level procedures. The Mobi-C Clinical Trial (ClinicalTrials.gov registration number: NCT00389597) was conducted at 24 sites in the US and was approved by the Institutional Review Board, Research Ethics Committee, or local equivalent of each participating site. 1.

Cervical degenerative disease: systematic review of economic analyses.

PubMed

Alvin, Matthew D; Qureshi, Sheeraz; Klineberg, Eric; Riew, K Daniel; Fischer, Dena J; Norvell, Daniel C; Mroz, Thomas E

2014-10-15

Systematic review. To perform an evidence-based synthesis of the literature assessing the cost-effectiveness of surgery for patients with symptomatic cervical degenerative disc disease (DDD). Cervical DDD is a common cause of clinical syndromes such as neck pain, cervical radiculopathy, and myelopathy. The appropriate surgical intervention(s) for a given problem is controversial, especially with regard to quality-of-life outcomes, complications, and costs. Although there have been many studies comparing outcomes and complications, relatively few have compared costs and, more importantly, cost-effectiveness of the interventions. We conducted a systematic search in PubMed/MEDLINE, EMBASE, the Cochrane Collaboration Library, the Cost-Effectiveness Analysis registry database, and the National Health Service Economic Evaluation Database for full economic evaluations published through January 16, 2014. Identification of full economic evaluations that were explicitly designed to evaluate and synthesize the costs and consequences of surgical procedures or surgical intervention with nonsurgical management in patients with cervical DDD were considered for inclusion, based on 4 key questions. Five studies were included, each specific to 1 or more of our focus questions. Two studies suggested that cervical disc replacement may be more cost-effective compared with anterior cervical discectomy and fusion. Two studies comparing anterior with posterior surgical procedures for cervical spondylotic myelopathy suggested that anterior surgery was more cost-effective than posterior surgery. One study suggested that posterior cervical foraminotomy had a greater net economic benefit than anterior cervical discectomy and fusion in a military population with unilateral cervical radiculopathy. No studies assessed the cost-effectiveness of surgical intervention compared with nonoperative treatment of cervical myelopathy or radiculopathy, although it is acknowledged that existing studies demonstrate the cost-effectiveness of surgical intervention for these 2 clinical entities. A paucity of high-quality economic literature exists regarding cost-effectiveness of surgical intervention for cervical DDD. Future research is necessary to validate the findings of the few studies that do exist to guide decisions for surgery by the physician and patient with respect to cost-effectiveness. 2.

Secular evolution of eccentricity in protoplanetary discs with gap-opening planets

NASA Astrophysics Data System (ADS)

Teyssandier, Jean; Ogilvie, Gordon I.

2017-06-01

We explore the evolution of the eccentricity of an accretion disc perturbed by an embedded planet whose mass is sufficient to open a large gap in the disc. Various methods for representing the orbit-averaged motion of an eccentric disc are discussed. We characterize the linear instability that leads to the growth of eccentricity by means of hydrodynamical simulations. We numerically recover the known result that eccentricity growth in the disc is possible when the planet-to-star mass ratio exceeds 3 × 10-3. For mass ratios larger than this threshold, the precession rates and growth rates derived from simulations, as well as the shape of the eccentric mode, compare well with the predictions of a linear theory of eccentric discs. We study mechanisms by which the eccentricity growth eventually saturates into a non-linear regime.

Comparison of Optic Disc Margin Identified by Color Disc Photography and High-Speed Ultrahigh-Resolution Optical Coherence Tomography

PubMed Central

Manassakorn, Anita; Ishikawa, Hiroshi; Kim, Jong S.; Wollstein, Gadi; Bilonick, Richard A.; Kagemann, Larry; Gabriele, Michelle L.; Sung, Kyung Rim; Mumcuoglu, Tarkan; Duker, Jay S.; Fujimoto, James G.; Schuman, Joel S.

2009-01-01

Objective To determine the correspondence between optic disc margins evaluated using disc photography (DP) and optical coherence tomography (OCT). Methods From May 1, 2005, through November 10, 2005, 17 healthy volunteers (17 eyes) had raster scans (180 frames, 501 samplings per frame) centered on the optic disc taken with stereo-optic DP and high-speed ultrahigh-resolution OCT (hsUHR-OCT). Two image outputs were derived from the hsUHR-OCT data set: an en face hsUHR-OCT fundus image and a set of 180 frames of cross-sectional images. Three ophthalmologists independently and in a masked, randomized fashion marked the disc margin on the DP, hsUHR-OCT fundus, and cross-sectional images using custom software. Disc size (area and horizontal and vertical diameters) and location of the geometric disc center were compared among the 3 types of images. Results The hsUHR-OCT fundus image definition showed a significantly smaller disc size than the DP definition (P<.001, mixed-effects analysis). The hsUHR-OCT cross-sectional image definition showed a significantly larger disc size than the DP definition (P<.001). The geometric disc center location was similar among the 3 types of images except for the y-coordinate, which was significantly smaller in the hsUHR-OCT fundus images than in the DP images. Conclusion The optic disc margin as defined by hsUHR-OCT was significantly different than the margin defined by DP. PMID:18195219

Computation models simulating notochordal cell extinction during early ageing of an intervertebral disc.

PubMed

Louman-Gardiner, K M; Coombe, D; Hunter, C J

2011-12-01

Lower back pain due to intervertebral disc (IVD) degeneration is a prevalent problem which drastically affects the quality of life of millions of sufferers. Healthy IVDs begin with high populations of notochordal cells in the nucleus pulposus, while by the second stage of degeneration, these cells will be replaced by chondrocyte-like cells. Because the IVD is avascular, these cells rely on passive diffusion of nutrients to survive. It is thought that this transition in cell phenotype causes the shift of the IVD's physical properties, which impede the flow of nutrients. Our computational model of the IVD illustrates its ability to simulate the evolving chemical and mechanical environments occurring during the early ageing process. We demonstrate that, due to the insufficient nutrient supply and accompanying changes in physical properties of the IVD, there was a resultant exponential decay in the number of notochordal cells over time.

The Application of Vibration Accelerations in the Assessment of Average Friction Coefficient of a Railway Brake Disc

NASA Astrophysics Data System (ADS)

Sawczuk, Wojciech

2017-06-01

Due to their wide range of friction characteristics resulting from the application of different friction materials and good heat dissipation conditions, railway disc brakes have long replaced block brakes in many rail vehicles. A block brake still remains in use, however, in low speed cargo trains. The paper presents the assessment of the braking process through the analysis of vibrations generated by the components of the brake system during braking. It presents a possibility of a wider application of vibroacoustic diagnostics (VA), which aside from the assessment of technical conditions (wear of brake pads) also enables the determination of the changes of the average friction coefficient as a function of the braking onset speed. Vibration signals of XYZ were measured and analyzed. The analysis of the results has shown that there is a relation between the values of the point measures and the wear of the brake pads.

The fundamentals of biotribology and its application to spine arthroplasty

PubMed Central

Harper, Megan L.; Dooris, Andrew; Paré, Philippe E.

2009-01-01

The biological effect of wear of articulating surfaces is a continued concern with large joint replacements and, likewise, of interest for total disc replacements. There are a number of important biotribological testing parameters that can greatly affect the outcome of a wear study in addition to the implant design and material selection. The current ASTM and ISO wear testing standards/guides for spine arthroplasty leave many choices as testing parameters. These factors include but are not limited to the sequence of kinematics and load, phasing, type of lubricant, and specimen preparation (sterilization and artificial aging). The spinal community should critically assess wear studies and be cognizant of the influence of the selected parameters on the test results. PMID:25802638

Are Collapsed Cervical Discs Amenable to Total Disc Arthroplasty?: Analysis of Prospective Clinical Data With 2-Year Follow Up.

PubMed

Patwardhan, Avinash G; Carandang, Gerard; Voronov, Leonard I; Havey, Robert M; Paul, Gary A; Lauryssen, Carl; Coric, Domagoj; Dimmig, Thomas; Musante, David

2016-12-15

Analysis of prospectively collected radiographic data. To investigate the influence of preoperative index-level range of motion (ROM) and disc height on postoperative ROM after cervical total disc arthroplasty (TDA) using compressible disc prostheses. Clinical studies demonstrate benefits of motion preservation over fusion; however, questions remain unanswered as to which preoperative factors have the ability to identify patients who are most likely to have good postoperative motion, which is the primary rationale for TDA. We analyzed prospectively collected data from a single-arm, multicenter study with 2-year follow up of 30 patients with 48 implanted levels. All received compressible cervical disc prostheses of 6 mm-height (M6C, Spinal Kinetics, Sunnyvale, CA). The influence of index-level preoperative disc height and ROM (each with two levels: below-median and above-median) on postoperative ROM was analyzed using 2 x 2 ANOVA. We further analyzed the radiographic outcomes of a subset of discs with preoperative height less than 3 mm, the so-called "collapsed" discs. Shorter (3.0 ± 0.4 mm) discs were significantly less mobile preoperatively than taller (4.4 ± 0.5 mm) discs (6.7° vs. 10.5°, P = 0.01). The postoperative ROM did not differ between the shorter and taller discs (5.6° vs. 5.0°, P = 0.63). Tall discs that were less mobile preoperatively had significantly smaller postoperative ROM than short discs with above-median preoperative mobility (P < 0.05). The "collapsed discs" (n = 8) were less mobile preoperatively compared with all discs combined (5.1° vs. 8.6°, P < 0.01). These discs were distracted to more than two times the preoperative height, from 2.6 to 5.7 mm, and had significantly greater postoperative ROM than all discs combined (7.6° vs. 5.3°, P < 0.05). We observed a significant interaction between preoperative index-level disc height and ROM in influencing postoperative ROM. Although limited by small sample size, the results suggest discs with preoperative height less than 3 mm may be amenable to disc arthroplasty using compressible disc prostheses. 2.

Intradiscal pressure study of percutaneous disc decompression with nucleoplasty in human cadavers.

PubMed

Chen, Yung C; Lee, Sang-heon; Chen, Darwin

2003-04-01

Intradiscal pressure was measured after percutaneous disc decompression by nucleoplasty in human cadavers with different degrees of disc degeneration. To assess intradiscal pressure change after disc decompression, and to analyze the influence of degeneration on the intradiscal pressure change. Partial removal of the nucleus has been shown to decompress herniated discs, relieving pressure on nerve roots and, in some cases, offering relief from disc pain. Nucleoplasty, a new minimally invasive procedure using patented Coblation technology, combines coagulation and ablation for partial removal of the nucleus. Coblated channels remove the tissue volume and may decrease the disc pressure. Three fresh human cadaver spinal specimens (T8-L5; age, 54-84 years; mean age, 70.7 years) were used in this investigation. The intradiscal pressure was measured at three points: before treatment, after each channel was created, and after treatment using a 25-guage 6-inch needle connected to a Merit Medical Systems Intellisystem Inflation Monitor. The needles were calibrated initially to approximately 30 pounds per square inch. For the control, the change in disc pressure was recorded by the same procedure without using Coblation energy. To evaluate the effectiveness of nucleoplasty, disc pressure changes were compared between treatment with and without Coblation energy. Intradiscal pressure was markedly reduced in the younger, healthy disc cadaver. In the older, degenerative disc cadavers, the change in intradiscal pressure after nucleoplasty was very small. There was an inverse correlation between the degree of disc degeneration and the change in intradiscal pressure. Pressure reduction through nucleoplasty is highly dependent on the degree of spine degeneration. Nucleoplasty markedly reduced intradiscal pressure in nondegenerative discs, but had a negligible effect on highly degenerative discs.

Biometry and spectral domain optical coherence tomography parameters in children with large cupping.

PubMed

Jung, Jong Jin; Baek, Seung-Hee; Kim, Ungsoo Samuel

2013-09-01

The purpose of this study is to investigate optic nerve head using spectral domain optical coherence tomography (SD-OCT) in children with large cupping. 111 eyes (4-10 years) were divided into three groups according to the cup to disc ratio: group 1, ≤0.3; group 2, 0.4-0.6; and group 3, ≥0.7. The rim area, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume were investigated using SD-OCT (Cirrus HD-OCT, Carl Zeiss, Jena, Germany), and the axial length and anterior chamber depth (ACD) were measured by IOL master (IOL master 500, Carl Zeiss, Jena, Germany). Next, we compared ocular biometry and SD-OCT between the three groups. The mean age of group 1 was 6.48 ± 1.42 years, 7.00 ± 1.75 years in group 2, and 6.63 ± 1.82 years in group 3 (p = 0.370). A significant difference was seen in the spherical equivalent between the groups (p = 0.001). Group 2 had the most myopic refractive errors. As the cup to disc ratio increases, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume increase significantly. When the results of ocular biometry and SD-OCT are adjusted for axial length, only disc area showed a significant correlation with cup to disc ratio (ACD: p = 0.473, rim area: p = 0.639, disc area: p = 0.005, and cup volume: p = 0.325). Axial length is the key factor determining disc size, which in turn is important for determining cup to disc ratio. Normal children with large cupping should be examined for axial length, myopic refractive errors, and disc size.

Comparative study of optic disc measurement by Copernicus optical coherence tomography and Heidelberg retinal tomography.

PubMed

Yang, Qing-Song; Yu, Ya-Jie; Li, Shu-Ning; Liu, Juan; Hao, Ying-Juan

2012-08-01

Copernicus optical coherence tomography (SOCT) is a new, ultra high-speed and high-resolution instrument available for clinical evaluation of optic nerve. The purpose of the study was to compare the agreements between SOCT and Heidelberg retinal tomography (HRT). A total of 44 healthy normal volunteers were recruited in this study. One eye in each subject was selected randomly. Agreement between SOCT and HRT-3 in measuring optic disc area was assessed using Bland-Altman plots. Relationships between measurements of optic nerve head parameter obtained by SOCT and HRT-3 were assessed by Pearson correlation. There was no significant difference in the average cup area (0.306 vs. 0.355 mm, P = 0.766), cup volume (0.158 vs. 0.130 mm, P = 0.106) and cup/disc ration (0.394 vs. 0.349 mm, P = 0.576) measured by the two instruments. However, other optic disc parameters from SOCT were significantly lower compared with HRT-3. The Bland-Altman plot revealed good agreement of cup area and cup volume measured by SOCT and HRT-3. Bad agreement of disc area, rim area, rim volume and cup/disc ratio were found between SOCT and HRT-3. The highest correlations between the two instruments were observed for cup area (r(2) = 0.783, P = 0.000) and cup/disc ratio (r(2) = 0.669, P = 0.000), whereas the lowest correlation was observed for disc area (r(2) = 0.100, P = 0.037), rim area (r(2) = 0.275, P = 0.000), cup volume (r(2) = 0.005, P = 0.391) and rim volume (r(2) = 0.021, P = 0.346). There were poor agreements between SOCT and HRT-3 for measurement of optic nerve parameters except cup area and cup volume. Measurement results of the two instruments are not interchangeable.

The Boston Keratoprosthesis: Comparing Corneal Epithelial Cell Compatibility with Titanium and PMMA

PubMed Central

Ament, Jared D.; Spurr-Michaud, Sandra J.; Dohlman, Claes H.; Gipson, Ilene K.

2014-01-01

Purpose To determine in vitro whether titanium is superior in corneal cell compatibility to standard polymethyl-methacrylate (PMMA) for the Boston Keratoprosthesis (KPro). Methods Human corneal-limbal epithelial (HCLE) cells were cultured 24, 48, 72, 96, 120, 144, or 168 hours in culture plates alone (controls) or with PMMA or titanium discs. Experiments were performed in triplicate and repeated (final n = 6). To determine if a soluble, toxic factor is emitted from materials, concurrent experiments at 48 and 144 hours were performed with discs placed in Transwell Supports, with HCLE cells plated beneath. As an additional test for soluble factors, cells were incubated 24 hours with disc-conditioned media, and number of viable cells per well was quantified at each timepoint by proliferation assay. To determine if delayed cell proliferation was attributable to cell death, HCLE cell death was measured under all conditions and quantified at each timepoint by cytotoxicity assay. The effects of material on HCLE cell proliferation over time was determined by repeated measures ANOVA. P < 0.05 was statistically significant. Results HCLE cell proliferation was greater in wells with titanium discs compared to PMMA. Differences between the test discs and control non-disc cocultures were statistically significant over time for both cell proliferation (P = 0.001) and death (P = 0.0025). No significant difference was found using Transwells (P = 0.9836) or disc-conditioned media (P = 0.36). Conclusion This in vitro HCLE cell model demonstrates significantly increased cell proliferation and decreased cell death with cell/titanium contact compared to cell/PMMA contact. Moreover, differences are unlikely attributable to a soluble factor. Prospective in vivo analysis of the two KPro biomaterials is indicated. PMID:19574903

Comparison of biomechanical function at ideal and varied surgical placement for two lumbar artificial disc implant designs: mobile-core versus fixed-core.

PubMed

Moumene, Missoum; Geisler, Fred H

2007-08-01

Finite element model. To estimate the effect of lumbar mobile-core and fixed-core artificial disc design and placement on the loading of the facet joints, and stresses on the polyethylene core. Although both mobile-core and fixed-core lumbar artificial disc designs have been used clinically, the effect of their design and the effect of placement within the disc space on the structural element loading, and in particular the facets and the implant itself, have not been investigated. A 3D nonlinear finite element model of an intact ligamentous L4-L5 motion segment was developed and validated in all 6 df based on previous experiments conducted on human cadavers. Facet loading of a mobile-core TDR and a fixed-core TDR were estimated with 4 different prosthesis placements for 3 different ranges of motion. Placing the mobile-core TDR anywhere within the disc space reduced facet loading by more than 50%, while the fixed-core TDR increased facet loading by more than 10% when compared with the intact disc in axial rotation. For central (ideal) placement, the mobile- and fixed-core implants were subjected to compressive stresses on the order of 3 MPa and 24 MPa, respectively. The mobile-core stresses were not affected by implant placement, while the fixed-core stresses increased by up to 40%. A mobile-core artificial disc design is less sensitive to placement, and unloads the facet joints, compared with a fixed-core design. The decreased core stress may result in a reduced potential for wear in a mobile-core prosthesis compared with a fixed-core prosthesis, which may increase the functional longevity of the device.

A Rapid Leaf-Disc Sampler for Psychrometric Water Potential Measurements 1

PubMed Central

Wullschleger, Stan D.; Oosterhuis, Derrick M.

1986-01-01

An instrument was designed which facilitates faster and more accurate sampling of leaf discs for psychrometric water potential measurements. The instrument consists of an aluminum housing, a spring-loaded plunger, and a modified brass-plated cork borer. The leaf-disc sampler was compared with the conventional method of sampling discs for measurement of leaf water potential with thermocouple psychrometers on a range of plant material including Gossypium hirsutum L., Zea mays L., and Begonia rex-cultorum L. The new sampler permitted a leaf disc to be excised and inserted into the psychrometer sample chamber in less than 7 seconds, which was more than twice as fast as the conventional method. This resulted in more accurate determinations of leaf water potential due to reduced evaporative water losses. The leaf-disc sampler also significantly reduced sample variability between individual measurements. This instrument can be used for many other laboratory and field measurements that necessitate leaf disc sampling. PMID:16664879

Fusion-nonfusion hybrid construct versus anterior cervical hybrid decompression and fusion: a comparative study for 3-level cervical degenerative disc diseases.

PubMed

Ding, Fan; Jia, Zhiwei; Wu, Yaohong; Li, Chao; He, Qing; Ruan, Dike

2014-11-01

A retrospective analysis. This study aimed to compare the safety and efficacy between the fusion-nonfusion hybrid construct (HC: anterior cervical corpectomy and fusion plus artificial disc replacement, ACCF plus cADR) and anterior cervical hybrid decompression and fusion (ACHDF: anterior cervical corpectomy and fusion plus discectomy and fusion, ACCF plus ACDF) for 3-level cervical degenerative disc diseases (cDDD). The optimal anterior technique for 3-level cDDD remains uncertain. Long-segment fusion substantially induced biomechanical changes at adjacent levels, which may lead to symptomatic adjacent segment degeneration. Hybrid surgery consisting of ACDF and cADR has been reported with good results for 2-level cDDD. In this context, ACCF combining with cADR may be an alternative to ACHDF for 3-level cDDD. Between 2009 and 2012, 28 patients with 3-level cDDD who underwent HC (n=13) and ACHDF (15) were retrospectively reviewed. Clinical assessments were based on Neck Disability Index, Japanese Orthopedic Association disability scale, visual analogue scale, Japanese Orthopedic Association recovery rate, and Odom criteria. Radiological analysis included range of motion of C2-C7 and adjacent segments and cervical lordosis. Perioperative parameters, radiological adjacent-level changes, and the complications were also assessed. HC showed better Neck Disability Index improvement at 12 and 24 months, as well as Japanese Orthopedic Association and visual analogue scale improvement at 24 months postoperatively (P<0.05). HC had better outcome according to Odom criteria but not significantly (P>0.05). The range of motion of C2-C7 and adjacent segments was less compromised in HC (P<0.05). Both 2 groups showed significant lordosis recovery postoperatively (P<0.05), but no difference was found between groups (P>0.05). The incidence of adjacent-level degenerative changes and complications was higher in ACHDF but not significantly (P>0.05). HC may be an alternative to ACHDF for 3-level cDDD due to the equivalent or superior early clinical outcomes, less compromised C2-C7 range of motion, and less impact at adjacent levels. 3.

Regression Analysis of Optical Coherence Tomography Disc Variables for Glaucoma Diagnosis.

PubMed

Richter, Grace M; Zhang, Xinbo; Tan, Ou; Francis, Brian A; Chopra, Vikas; Greenfield, David S; Varma, Rohit; Schuman, Joel S; Huang, David

2016-08-01

To report diagnostic accuracy of optical coherence tomography (OCT) disc variables using both time-domain (TD) and Fourier-domain (FD) OCT, and to improve the use of OCT disc variable measurements for glaucoma diagnosis through regression analyses that adjust for optic disc size and axial length-based magnification error. Observational, cross-sectional. In total, 180 normal eyes of 112 participants and 180 eyes of 138 participants with perimetric glaucoma from the Advanced Imaging for Glaucoma Study. Diagnostic variables evaluated from TD-OCT and FD-OCT were: disc area, rim area, rim volume, optic nerve head volume, vertical cup-to-disc ratio (CDR), and horizontal CDR. These were compared with overall retinal nerve fiber layer thickness and ganglion cell complex. Regression analyses were performed that corrected for optic disc size and axial length. Area-under-receiver-operating curves (AUROC) were used to assess diagnostic accuracy before and after the adjustments. An index based on multiple logistic regression that combined optic disc variables with axial length was also explored with the aim of improving diagnostic accuracy of disc variables. Comparison of diagnostic accuracy of disc variables, as measured by AUROC. The unadjusted disc variables with the highest diagnostic accuracies were: rim volume for TD-OCT (AUROC=0.864) and vertical CDR (AUROC=0.874) for FD-OCT. Magnification correction significantly worsened diagnostic accuracy for rim variables, and while optic disc size adjustments partially restored diagnostic accuracy, the adjusted AUROCs were still lower. Axial length adjustments to disc variables in the form of multiple logistic regression indices led to a slight but insignificant improvement in diagnostic accuracy. Our various regression approaches were not able to significantly improve disc-based OCT glaucoma diagnosis. However, disc rim area and vertical CDR had very high diagnostic accuracy, and these disc variables can serve to complement additional OCT measurements for diagnosis of glaucoma.

Mechanical Characterization of the Human Lumbar Intervertebral Disc Subjected to Impact Loading Conditions

NASA Astrophysics Data System (ADS)

Jamison, David, IV

Low back pain is a large and costly problem in the United States. Several working populations, such as miners, construction workers, forklift operators, and military personnel, have an increased risk and prevalence of low back pain compared to the general population. This is due to exposure to repeated, transient impact shocks, particularly while operating vehicles or other machinery. These shocks typically do not cause acute injury, but rather lead to pain and injury over time. The major focus in low back pain is often the intervertebral disc, due to its role as the major primary load-bearing component along the spinal column. The formation of a reliable standard for human lumbar disc exposure to repeated transient shock could potentially reduce injury risk for these working populations. The objective of this project, therefore, is to characterize the mechanical response of the lumbar intervertebral disc subjected to sub-traumatic impact loading conditions using both cadaveric and computational models, and to investigate the possible implications of this type of loading environment for low back pain. Axial, compressive impact loading events on Naval high speed boats were simulated in the laboratory and applied to human cadaveric specimen. Disc stiffness was higher and hysteresis was lower than quasi-static loading conditions. This indicates a shift in mechanical response when the disc is under impact loads and this behavior could be contributing to long-term back pain. Interstitial fluid loss and disc height changes were shown to affect disc impact mechanics in a creep study. Neutral zone increased, while energy dissipation and low-strain region stiffness decreased. This suggests that the disc has greater clinical instability during impact loading with progressive creep and fluid loss, indicating that time of day should be considered for working populations subjected to impact loads. A finite element model was developed and validated against cadaver specimen subjected to impacts in the laboratory. Analysis showed greater total von Mises stress and pore pressure in the components of the disc under transient shocks compared to static or quasi-static loading. These findings support the idea that impact shocks cause a change in mechanical response and are potentially damaging to the disc in the long term.

Development and Translation of a Tissue-Engineered Disc in a Preclinical Rodent Model

DTIC Science & Technology

2013-10-01

authors Dong Hwa Kim, John T. Martin, Dawn M. Elliott, Lachlan J. Smith , and Robert L. Mauck...Replacement in a Small Animal Model with authors John T. Martin, Andrew H. Milby, Joseph A. Chiaro, Dong Hwa Kim, Nader M. Hebela, Lachlan J. Smith , Dawn... Smith , Dawn M. Elliott, and Robert L. Mauck is now in review. To carry out this study, radiopaque scaffolds were generated from a 14.3% w/v slurry

Wear of the Charité® lumbar intervertebral disc replacement investigated using an electro-mechanical spine simulator

PubMed Central

Moghadas, Parshia; Shepherd, Duncan ET; Hukins, David WL

2015-01-01

The Charité® lumbar intervertebral disc replacement was subjected to wear testing in an electro-mechanical spine simulator. Sinusoidally varying compression (0.6–2 kN, frequency 2 Hz), rotation (±2°, frequency 1 Hz), flexion–extension (6° to −3°, frequency 1 Hz) and lateral bending (±2°, frequency 1 Hz) were applied out of phase to specimens immersed in diluted calf serum at 37 °C. The mass of the ultra-high-molecular weight polyethylene component of the device was measured at intervals of 0.5, 1, 2, 3, 4 and 5 million cycles; its volume was also measured by micro-computed tomography. Total mass and volume losses were 60.3 ± 4.6 mg (mean ± standard deviation) and 64.6 ± 6.0 mm3. Corresponding wear rates were 12.0 ± 1.4 mg per million cycles and 12.8 ± 1.2 mm3 per million cycles; the rate of loss of volume corresponds to a mass loss of 11.9 ± 1.1 mg per million cycles, that is, the two sets of measurements of wear agree closely. Wear rates also agree closely with measurements made in another laboratory using the same protocol but using a conventional mechanical spine simulator. PMID:25834002

Localization of the lumbar discs using machine learning and exact probabilistic inference.

PubMed

Oktay, Ayse Betul; Akgul, Yusuf Sinan

2011-01-01

We propose a novel fully automatic approach to localize the lumbar intervertebral discs in MR images with PHOG based SVM and a probabilistic graphical model. At the local level, our method assigns a score to each pixel in target image that indicates whether it is a disc center or not. At the global level, we define a chain-like graphical model that represents the lumbar intervertebral discs and we use an exact inference algorithm to localize the discs. Our main contributions are the employment of the SVM with the PHOG based descriptor which is robust against variations of the discs and a graphical model that reflects the linear nature of the vertebral column. Our inference algorithm runs in polynomial time and produces globally optimal results. The developed system is validated on a real spine MRI dataset and the final localization results are favorable compared to the results reported in the literature.

A study of the effect of bulges on bar formation in disc galaxies

NASA Astrophysics Data System (ADS)

Kataria, Sandeep Kumar; Das, Mousumi

2018-04-01

We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disc instabilities that evolve by transferring angular momentum from the inner to outer discs and to the dark matter halo. It is well known that a massive spherical component such as halo in a disc galaxy can make it bar stable. In this study, we explore the effect of another spherical component, the bulge, on bar formation in disc galaxies. In our models, we vary both the bulge mass and concentration. We have used two sets of models: one that has a dense bulge and high surface density disc, and the other model has a less concentrated bulge and a lighter disc. In both models, we vary the bulge to disc mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cut-off in bulge-to-disc mass ratio Mb/Md above which bars cannot form; the cut-off is smaller for denser bulges (Mb/Md = 0.2) compared to less denser ones (Mb/Md = 0.5). We define a new criterion for bar formation in terms of the ratio of bulge to total radial force (Fb/Ftot) at the disc scale lengths above which bars cannot form. We find that if Fb/Ftot > 0.35, a disc is stable and a bar cannot form. Our results indicate that early-type disc galaxies can still form strong bars in spite of having massive bulges.

Human disc degeneration is associated with increased MMP 7 expression.

PubMed

Le Maitre, C L; Freemont, A J; Hoyland, J A

2006-01-01

During intervertebral disc (IVD) degeneration, normal matrix synthesis decreases and degradation of disc matrix increases. A number of proteases that are increased during disc degeneration are thought to be involved in its pathogenesis. Matrix metalloproteinase 7 (MMP 7) (Matrilysin, PUMP-1) is known to cleave the major matrix molecules found within the IVD, i.e., the proteoglycan aggrecan and collagen type II. To date, however, it is not known how its expression changes with degeneration or its exact location. We investigated the localization of MMP 7 in human, histologically graded, nondegenerate, degenerated and prolapsed discs to ascertain whether MMP 7 is up-regulated during disc degeneration. Samples of human IVD tissue were fixed in neutral buffered formalin, embedded in paraffin, and sections stained with hematoxylin and eosin to score the degree of morphological degeneration. Immunohistochemistry was performed to localize MMP 7 in 41 human IVDs with varying degrees of degeneration. We found that the chondrocyte-like cells of the nucleus pulposus and inner annulus fibrosus were MMP 7 immunopositive; little immunopositivity was observed in the outer annulus. Nondegenerate discs showed few immunopositive cells. A significant increase in the proportion of MMP 7 immunopositive cells was seen in the nucleus pulposus of discs classified as showing intermediate levels of degeneration and a further increase was seen in discs with severe degeneration. Prolapsed discs showed more MMP 7 immunopositive cells compared to nondegenerated discs, but fewer than those seen in cases of severe degeneration.

An inner warp in the DoAr 44 T Tauri transition disc

NASA Astrophysics Data System (ADS)

Casassus, Simon; Avenhaus, Henning; Pérez, Sebastián; Navarro, Víctor; Cárcamo, Miguel; Marino, Sebastián; Cieza, Lucas; Quanz, Sascha P.; Alarcón, Felipe; Zurlo, Alice; Osses, Axel; Rannou, Fernando R.; Román, Pablo E.; Barraza, Marcelo

2018-07-01

Optical/IR images of transition discs (TDs) have revealed deep intensity decrements in the rings of HAeBes HD 142527 and HD 100453 that can be interpreted as shadowing from sharply tilted inner discs, such that the outer discs are directly exposed to stellar light. Here we report similar dips in SPHERE+IRDIS differential polarized imaging (DPI) of T Tauri DoAr 44. With a fairly axially symmetric ring in the sub-mm radio continuum, DoAr 44 is likely also a warped system. We constrain the warp geometry by comparing radiative transfer predictions with the DPI data in H band (Qϕ(H)) and with a re-processing of archival 336 GHz ALMA observations. The observed DPI shadows have coincident radio counterparts, but the intensity drops are much deeper in Qϕ(H) (˜88 per cent), compared to the shallow drops at 336 GHz (˜24 per cent). Radiative transfer predictions with an inner disc tilt of ˜30 ± 5 deg approximately account for the observations. ALMA long-baseline observations should allow the observation of the warped gas kinematics inside the cavity of DoAr 44.

Analysis of the spinal nerve roots in relation to the adjacent vertebral bodies with respect to a posterolateral vertebral body replacement procedure.

PubMed

Awwad, Waleed; Bourget-Murray, Jonathan; Zeiadin, Nadil; Mejia, Juan P; Steffen, Thomas; Algarni, Abdulrahman D; Alsaleh, Khalid; Ouellet, Jean; Weber, Michael; Jarzem, Peter F

2017-01-01

This study aims to improve the understanding of the anatomic variations along the thoracic and lumbar spine encountered during an all-posterior vertebrectomy, and reconstruction procedure. This information will help improve our understanding of human spine anatomy and will allow better planning for a vertebral body replacement (VBR) through either a transpedicular or costotransversectomy approach. The major challenge to a total posterior approach vertebrectomy and VBR in the thoracolumbar spine lies in the preservation of important neural structures. This was a retrospective analysis. Hundred normal magnetic resonance imaging (MRI) spinal studies (T1-L5) on sagittal T2-weighted MRI images were studied to quantify: (1) mid-sagittal vertebral body (VB) dimensions (anterior, midline, and posterior VB height), (2) midline VB and associated intervertebral discs height, (3) mean distance between adjacent spinal nerve roots (DNN) and mean distance between the inferior endplate of the superior vertebrae to its respective spinal nerve root (DNE), and (4) posterior approach expansion ratio (PAER). (1) The mean anterior VB height gradually increased craniocaudally from T1 to L5. The mean midline and posterior VB height showed a similar pattern up to L2. Mean posterior VB height was larger than the mean anterior VB height from T1 to L2, consistent with anterior wedging, and then measured less than the mean anterior VB height, indicating posterior wedging. (2) Midline VB and intervertebral disc height gradually increased from T1 to L4. (3) DNN and DNE were similar, whereby they gradually increased from T1 to L3. (5) Mean PAER varied between 1.69 (T12) and 2.27 (L5) depending on anatomic level. The dimensions of the thoracic and lumbar vertebrae and discs vary greatly. Thus, any attempt at carrying out a VBR from a posterior approach should take into account the specifications at each spinal level.

Comparison of Ripening Processes in Intact Tomato Fruit and Excised Pericarp Discs 1

PubMed Central

Campbell, Alan D.; Huysamer, Marius; Stotz, Henrik U.; Greve, L. Carl; Labavitch, John M.

1990-01-01

Physiological processes characteristic of ripening in tissues of intact tomato fruit (Lycopersicon esculentum Mill.) were examined in excised pericarp discs. Pericarp discs were prepared from mature-green tomato fruit and stored in 24-well culture plates, in which individual discs could be monitored for color change, ethylene biosynthesis, and respiration, and selected for cell wall analysis. Within the context of these preparation and handling procedures, most whole fruit ripening processes were maintained in pericarp discs. Pericarp discs and matched intact fruit passed through the same skin color stages at similar rates, as expressed in the L*a*b* color space, changing from green (a* < −5) to red (a* > 15) in about 6 days. Individual tissues of the pericarp discs changed color in the same sequence seen in intact fruit (exocarp, endocarp, then vascular parenchyma). Discs from different areas changed in the same spatial sequence seen in intact fruit (bottom, middle, top). Pericarp discs exhibited climacteric increases in ethylene biosynthesis and CO2 production comparable with those seen in intact fruit, but these were more tightly linked to rate of color change, reaching a peak around a* = 5. Tomato pericarp discs decreased in firmness as color changed. Cell wall carbohydrate composition changed with color as in intact fruit: the quantity of water-soluble pectin eluted from the starch-free alcohol insoluble substances steadily increased and more tightly bound, water-insoluble, pectin decreased in inverse relationship. The cell wall content of the neutral sugars arabinose, rhamnose, and galactose steadily decreased as color changed. The extractable activity of specific cell wall hydrolases changed as in intact fruit: polygalacturonase activity, not detectable in green discs (a* = −5), appeared as discs turned yellow-red (a* = 5), and increased another eight-fold as discs became full red (a* value +20). Carboxymethyl-cellulase activity, low in extracts from green discs, increased about six-fold as discs changed from yellow (a* = 0) to red. PMID:16667893

Efficient radiative transfer techniques in hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Mercer, A.; Stamatellos, D.; Dunhill, A.

2018-05-01

Radiative transfer is an important component of hydrodynamic simulations as it determines the thermal properties of a physical system. It is especially important in cases where heating and cooling regulate significant processes, such as in the collapse of molecular clouds, the development of gravitational instabilities in protostellar discs, disc-planet interactions, and planet migration. We compare two approximate radiative transfer methods which indirectly estimate optical depths within hydrodynamic simulations using two different metrics: (i) the gravitational potential and density of the gas (Stamatellos et al.), and (ii) the pressure scale-height (Lombardi et al.). We find that both methods are accurate for spherical configurations e.g. in collapsing molecular clouds and within clumps that form in protostellar discs. However, the pressure scale-height approach is more accurate in protostellar discs (low and high-mass discs, discs with spiral features, discs with embedded planets). We also investigate the β-cooling approximation which is commonly used when simulating protostellar discs, and in which the cooling time is proportional to the orbital period of the gas. We demonstrate that the use of a constant β cannot capture the wide range of spatial and temporal variations of cooling in protostellar discs, which may affect the development of gravitational instabilities, planet migration, planet mass growth, and the orbital properties of planets.

Effect of grinding with diamond-disc and -bur on the mechanical behavior of a Y-TZP ceramic.

PubMed

Pereira, G K R; Amaral, M; Simoneti, R; Rocha, G C; Cesar, P F; Valandro, L F

2014-09-01

This study compared the effects of grinding on the surface micromorphology, phase transformation (t→m), biaxial flexural strength and structural reliability (Weibull analysis) of a Y-TZP (Lava) ceramic using diamond-discs and -burs. 170 discs (15×1.2mm) were produced and divided into 5 groups: without treatment (Ctrl, as-sintered), and ground with 4 different systems: extra-fine (25µm, Xfine) and coarse diamond-bur (181µm, Coarse), 600-grit (25µm, D600) and 120-grit diamond-disc (160µm, D120). Grinding with burs was performed using a contra-angle handpiece (T2-Revo R170, Sirona), while for discs (Allied) a Polishing Machine (Ecomet, Buehler) was employed, both under water-cooling. Micromorphological analysis showed distinct patterns generated by grinding with discs and burs, independent of grit size. There was no statistical difference for characteristic strength values (MPa) between smaller grit sizes (D600 - 1050.08 and Xfine - 1171.33), although they presented higher values compared to Ctrl (917.58). For bigger grit sizes, a significant difference was observed (Coarse - 1136.32>D120 - 727.47). Weibull Modules were statistically similar between the tested groups. Within the limits of this study, from a micromorphological point-of-view, the treatments performed did not generate similar effects, so from a methodological point-of-view, diamond-discs should not be employed to simulate clinical abrasion performed with diamond-burs on Y-TZP ceramics. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Herschel resolved far-infrared dust ring around HD 207129

NASA Astrophysics Data System (ADS)

Marshall, J. P.; Löhne, T.; Montesinos, B.; Krivov, A. V.; Eiroa, C.; Absil, O.; Bryden, G.; Maldonado, J.; Mora, A.; Sanz-Forcada, J.; Ardila, D.; Augereau, J.-Ch.; Bayo, A.; Del Burgo, C.; Danchi, W.; Ertel, S.; Fedele, D.; Fridlund, M.; Lebreton, J.; González-García, B. M.; Liseau, R.; Meeus, G.; Müller, S.; Pilbratt, G. L.; Roberge, A.; Stapelfeldt, K.; Thébault, P.; White, G. J.; Wolf, S.

2011-05-01

Context. Dusty debris discs around main sequence stars are thought to be the result of continuous collisional grinding of planetesimals in the system. The majority of these systems are unresolved and analysis of the dust properties is limited by the lack of information regarding the dust location. Aims: The Herschel DUNES key program is observing 133 nearby, Sun-like stars (<20 pc, FGK spectral type) in a volume limited survey to constrain the absolute incidence of cold dust around these stars by detection of far infrared excess emission at flux levels comparable to the Edgeworth-Kuiper belt (EKB). Methods: We have observed the Sun-like star HD 207129 with Herschel PACS and SPIRE. In all three PACS bands we resolve a ring-like structure consistent with scattered light observations. Using α Boötis as a reference point spread function (PSF), we deconvolved the images, clearly resolving the inner gap in the disc at both 70 and 100 μm. Results: We have resolved the dust-producing planetesimal belt of a debris disc at 100 μm for the first time. We measure the radial profile and fractional luminosity of the disc, and compare the values to those of discs around stars of similar age and/or spectral type, placing this disc in context of other resolved discs observed by Herschel/DUNES. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Development of friction material by using precast prefired (pcp f) blocks

NASA Astrophysics Data System (ADS)

Dineshkumar, R.; Ramanamurthy, E. V. V.; Krishnapavanteja, Ch

2017-05-01

The braking system used to control and stop automobile system. The braking system converts the kinematic energy into heat energy by friction. The performance of the brake pad depends on composition of friction materials. The asbestos brake pads are carcinogenic nature and it makes so many health problems. The present research work is going to replacement of asbestos by new materials. The new material is made by fused ceramic materials from industrial wastage. In this study the industrial waste are recycled and conducted the suitable test to compare the performance of the new material with existing brake pad material. The wear test was conducted by pin on disc experiment. The non asbestos, nonfused, fused samples are represented by x1, x2 and x3. The new brake pad material is formed by non fused and fused ceramic materials. The brake pads are manufactured by powder compacting process.

Relationship between microstructure and tribological behavior of CFRC composites

NASA Astrophysics Data System (ADS)

de Souza, Maria Aparecida Miranda; Pardini, Luiz Claudio

2017-12-01

Carbon fiber reinforced carbon (CFRC) composites were initially introduced in spacecraft propulsion area and quickly started to be applied in aircraft braking systems, replacing conventional metallic systems, thanks to their excellent tribological properties. Each company develops their own CFRC composite production system, the information is unique to each manufacturer, and little is reported in the literature. In this work, tribological characterizations of three commercial CFRC composites are performed using a pin-on-disc tribometer. The results showed that the pairs assembled with pyrolytic matrix composites of rough or smooth laminar texture with graphitization index between 18 and 40% has an average COF between 0.15 and 0.25, while the pairs assembled with mixed pairs, pyrolytic matrix and glassy matrix, or pair of glassy matrix display average COF between 0.10 and 0.15. Wear which can reach a rate 9 times higher to the tribological pair of glassy composite when compared to a pyrolytic composite.

Effects of cryogenic treatment on the wear properties of brake discs

NASA Astrophysics Data System (ADS)

Nadig, D. S.; Shivakumar, P.; Anoop, S.; Chinmay, Kulkarni; Divine, P. V.; Harsha, H. P.

2017-02-01

Disc brakes are invariably used in all the automobiles either to reduce the rotational speed of the wheel or to hold the vehicle stationary. During the braking action, the kinetic energy is converted into heat which can result in high temperatures resulting in fading of brake effects. Brake discs produced out of martensite stainless steel (SS410) are expected to exhibit high wear resistance properties with low value of coefficient of friction. These factors increase the useful life of the brake discs with minimal possibilities of brake fade. To study the effects of cryogenic treatment on the wear behaviour, two types of brake discs were cryotreated at 98K for 8 and 24 hours in a specially developed cryotreatment system using liquid nitrogen. Wear properties of the untreated and cryotreated test specimens were experimentally determined using the pin on disc type tribometer (ASTM G99-95). Similarly, the Rockwell hardness (HRC) of the specimens were tested in a hardness tester in accordance with ASTM E18. In this paper, the effects of cryotreatment on the wear and hardness properties of untreated and cryotreated brake discs are presented. Results indicate enhancement of wear properties and hardness after cryogenic treatment compared with the normal brakes discs.

Loss of notochordal cell phenotype in 3D-cell cultures: implications for disc physiology and disc repair.

PubMed

Omlor, G W; Nerlich, A G; Tirlapur, U K; Urban, J P; Guehring, T

2014-12-01

Embryonic notochordal disc nucleus cells (NC) have been identified to protect disc tissue against disc degeneration but in human beings NC phenotype gets lost with aging and the pathophysiological mechanisms are poorly understood. NC may stimulate other cells via soluble factors, and NC-conditioned medium can be used to stimulate matrix production of other disc cells and mesenchymal stem cells and thus may be of special interest for biological disc repair. As this stimulatory effect is associated with the NC phenotype, we investigated how cell morphology and gene-expression of the NC phenotype changes with time in 3D-cell culture. NC and inner annulus chondrocyte-like cells (CLC) from immature pigtails (freshly isolated cells/tissue, 3D-alginate beads, 3D-clusters) were cultured for up to 16 days under normoxia and hypoxia. Protein-expression was analysed by immunohistology and gene-expression analysis was carried out on freshly isolated cells and cultured cells. Cell morphology and proliferation were analysed by two-photon-laser-microscopy. Two-photon-laser-microscopy showed a homogenous and small CLC population in the inner annulus, which differed from the large vacuole-containing NC in the nucleus. Immunohistology found 93 % KRT8 positive cells in the nucleus and intracellular and pericellular Col2, IL6, and IL12 staining while CLC were KRT8 negative. Freshly isolated NC showed significantly higher KRT8 and CAIII but lower Col2 gene-expression than CLC. NC in 3D-cultures demonstrated significant size reduction and loss of vacuoles with culture time, all indicating a loss of the characteristic NC morphology. Hypoxia reduced the rate of decrease in NC size and vacuoles. Gene-expression of KRT8 and CAIII in NC fell significantly early in culture while Col2 did not decrease significantly within the culture period. In CLC, KRT8 and CAIII gene-expression was low and did not change noticeably in culture, whereas Col2 expression fell with time in culture. 3D-culture caused a rapid loss of NC phenotype towards a CLC phenotype with disappearance of vacuoles, reduced cell size, increased proliferation, and gene-expression changes. These findings may be related to NC nutritional demands and support the latest hypothesis of NC maturation into CLC opposing the idea that NC get lost in human discs by cell death or apoptosis to be replaced by CLC from the inner annulus.

HD 172555: Detection of 63 micrometers [OI] Emission in a Debris Disc

NASA Technical Reports Server (NTRS)

Riviere-Marichalar, P.; Barrado, D.; Augereau, J. -C.; Thi, W. F.; Roberge, A.; Eiroa, C.; Montesinos, B.; Meeus, G.; Howard, C.; Sandell, G.;

Global multifluid simulations of the magnetorotational instability in radially stratified protoplanetary discs

NASA Astrophysics Data System (ADS)

Rodgers-Lee, D.; Ray, T. P.; Downes, T. P.

2016-11-01

The redistribution of angular momentum is a long standing problem in our understanding of protoplanetary disc (PPD) evolution. The magnetorotational instability (MRI) is considered a likely mechanism. We present the results of a study involving multifluid global simulations including Ohmic dissipation, ambipolar diffusion and the Hall effect in a dynamic, self-consistent way. We focus on the turbulence resulting from the non-linear development of the MRI in radially stratified PPDs and compare with ideal magnetohydrodynamics simulations. In the multifluid simulations, the disc is initially set up to transition from a weak Hall-dominated regime, where the Hall effect is the dominant non-ideal effect but approximately the same as or weaker than the inductive term, to a strong Hall-dominated regime, where the Hall effect dominates the inductive term. As the simulations progress, a substantial portion of the disc develops into a weak Hall-dominated disc. We find a transition from turbulent to laminar flow in the inner regions of the disc, but without any corresponding overall density feature. We introduce a dimensionless parameter, αRM, to characterize accretion with αRM ≳ 0.1 corresponding to turbulent transport. We calculate the eddy turnover time, teddy, and compared this with an effective recombination time-scale, trcb, to determine whether the presence of turbulence necessitates non-equilibrium ionization calculations. We find that trcb is typically around three orders of magnitude smaller than teddy. Also, the ionization fraction does not vary appreciably. These two results suggest that these multifluid simulations should be comparable to single-fluid non-ideal simulations.

Effectiveness of disinfection therapies and promotion of osteoblast growth on osseotite and nanotite implant surfaces.

PubMed

Lubin, Judith; Hernandez, Maria A; Drukteinis, Saulius E; Parker, William B; Murray, Peter E

2014-08-01

To evaluate the effectiveness of 4 procedures to disinfect implant surfaces intentionally inoculated with bacteria and afterward to evaluate osteoblast viability to the disinfected implant surfaces. Eighty-eight commercially pure Osseotite and Nanotite titanium implant discs were inoculated with Porphyromonas gingivalis. The implant surfaces were disinfected with EDTA, tetracycline, citric acid, or neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. The implant discs were then placed in cultures of osteoblast cells. Osseotite implant discs were easier to disinfect compared with the Nanotite implant discs. Citric acid and tetracycline were the most effective solutions for the disinfection of P. gingivalis from the Osseotite implant discs. The Nanotite implant discs were the most difficult to disinfect, likely because of their chemical and physical properties. Citric acid and tetracycline were most effective for disinfecting the Osseotite implant discs, and further clinical research is needed to verify these effects in vivo. The Nd:YAG laser was the weakest disinfection method, and it is not recommended for disinfecting implant surfaces until its effectiveness is improved.

Stellar wind erosion of protoplanetary discs

NASA Astrophysics Data System (ADS)

Schnepf, N. R.; Lovelace, R. V. E.; Romanova, M. M.; Airapetian, V. S.

2015-04-01

An analytic model is developed for the erosion of protoplanetary gas discs by high-velocity magnetized stellar winds. The winds are centrifugally driven from the surface of rapidly rotating, strongly magnetized young stars. The presence of the magnetic field in the wind leads to Reynolds numbers sufficiently large to cause a strongly turbulent wind/disc boundary layer which entrains and carries away the disc gas. The model uses the conservation of mass and momentum in the turbulent boundary layer. The time-scale for significant erosion depends on the disc accretion speed, disc accretion rate, the wind mass-loss rate, and the wind velocity. The time-scale is estimated to be ˜2 × 106 yr. The analytic model assumes a steady stellar wind with mass- loss rate dot {M}}_w ˜ 10^{-10} M_{⊙} yr-1 and velocity vw ˜ 103 km s-1. A significant contribution to the disc erosion can come from frequent powerful coronal mass ejections (CMEs) where the average mass-loss rate in CMEs, dot{M}_CME, and velocities, vCME, have values comparable to those for the steady wind.

Optical Coherence Tomography Angiography of Optic Disc Perfusion in Glaucoma

PubMed Central

Jia, Yali; Wei, Eric; Wang, Xiaogang; Zhang, Xinbo; Morrison, John C.; Parikh, Mansi; Lombardi, Lori H.; Gattey, Devin M.; Armour, Rebecca L.; Edmunds, Beth; Kraus, Martin F.; Fujimoto, James G.; Huang, David

2014-01-01

Purpose To compare optic disc perfusion between normal and glaucoma subjects using optical coherence tomography (OCT) angiography and detect optic disc perfusion changes in glaucoma. Design Observational, cross-sectional study. Participants Twenty-four normal subjects and 11 glaucoma patients were included. Methods One eye of each subject was scanned by a high-speed 1050 nm wavelength swept-source OCT instrument. The split-spectrum amplitude-decorrelation angiography algorithm (SSADA) was used to compute three-dimensional optic disc angiography. A disc flow index was computed from four registered scans. Confocal scanning laser ophthalmoscopy (cSLO) was used to measure disc rim area, and stereo photography was used to evaluate cup/disc ratios. Wide field OCT scans over the discs were used to measure retinal nerve fiber layer (NFL) thickness. Main Outcome Measurements Variability was assessed by coefficient of variation (CV). Diagnostic accuracy was assessed by sensitivity and specificity. Comparisons between glaucoma and normal groups were analyzed by Wilcoxon rank-sum test. Correlations between disc flow index, structural assessments, and visual field (VF) parameters were assessed by linear regression. Results In normal discs, a dense microvascular network was visible on OCT angiography. This network was visibly attenuated in glaucoma subjects. The intra-visit repeatability, inter-visit reproducibility, and normal population variability of the optic disc flow index were 1.2%, 4.2%, and 5.0% CV respectively. The disc flow index was reduced by 25% in the glaucoma group (p = 0.003). Sensitivity and specificity were both 100% using an optimized cutoff. The flow index was highly correlated with VF pattern standard deviation (R2 = 0.752, p = 0.001). These correlations were significant even after accounting for age, cup/disc area ratio, NFL, and rim area. Conclusions OCT angiography, generated by the new SSADA algorithm, repeatably measures optic disc perfusion. OCT angiography could be useful in the evaluation of glaucoma and glaucoma progression. PMID:24629312

A Large Animal Model that Recapitulates the Spectrum of Human Intervertebral Disc Degeneration

PubMed Central

Gullbrand, Sarah E.; Malhotra, Neil R.; Schaer, Thomas P.; Zawacki, Zosia; Martin, John T.; Bendigo, Justin R.; Milby, Andrew H.; Dodge, George R.; Vresilovic, Edward J.; Elliott, Dawn M.; Mauck, Robert L.; Smith, Lachlan J.

2016-01-01

Objective The objective of this study was to establish a large animal model that recapitulates the spectrum of intervertebral disc degeneration that occurs in humans and which is suitable for pre-clinical evaluation of a wide range of experimental therapeutics. Design Degeneration was induced in the lumbar intervertebral discs of large frame goats by either intradiscal injection of chondroitinase ABC (ChABC) over a range of dosages (0.1U, 1U or 5U) or subtotal nucleotomy. Radiographs were used to assess disc height changes over 12 weeks. Degenerative changes to the discs and endplates were assessed via magnetic resonance imaging (MRI), semi-quantitative histological grading, micro-computed tomography (µCT), and measurement of disc biomechanical properties. Results Degenerative changes were observed for all interventions that ranged from mild (0.1U ChABC) to moderate (1U ChABC and nucleotomy) to severe (5U ChABC). All groups showed progressive reductions in disc height over 12 weeks. Histological scores were significantly increased in the 1U and 5U ChABC groups. Reductions in T2 and T1ρ, and increased Pfirrmann grade were observed on MRI. Resorption and remodeling of the cortical boney endplate adjacent to ChABC injected discs also occurred. Spine segment range of motion was greater and compressive modulus was lower in 1U ChABC and nucleotomy discs compared to intact. Conclusions A large animal model of disc degeneration was established that recapitulates the spectrum of structural, compositional and biomechanical features of human disc degeneration. This model may serve as a robust platform for evaluating the efficacy of therapeutics targeted towards varying degrees of disc degeneration. PMID:27568573

Gravitational instabilities in a protosolar-like disc - I. Dynamics and chemistry

NASA Astrophysics Data System (ADS)

Evans, M. G.; Ilee, J. D.; Boley, A. C.; Caselli, P.; Durisen, R. H.; Hartquist, T. W.; Rawlings, J. M. C.

2015-10-01

To date, most simulations of the chemistry in protoplanetary discs have used 1 + 1D or 2D axisymmetric α-disc models to determine chemical compositions within young systems. This assumption is inappropriate for non-axisymmetric, gravitationally unstable discs, which may be a significant stage in early protoplanetary disc evolution. Using 3D radiative hydrodynamics, we have modelled the physical and chemical evolution of a 0.17 M⊙ self-gravitating disc over a period of 2000 yr. The 0.8 M⊙ central protostar is likely to evolve into a solar-like star, and hence this Class 0 or early Class I young stellar object may be analogous to our early Solar system. Shocks driven by gravitational instabilities enhance the desorption rates, which dominate the changes in gas-phase fractional abundances for most species. We find that at the end of the simulation, a number of species distinctly trace the spiral structure of our relatively low-mass disc, particularly CN. We compare our simulation to that of a more massive disc, and conclude that mass differences between gravitationally unstable discs may not have a strong impact on the chemical composition. We find that over the duration of our simulation, successive shock heating has a permanent effect on the abundances of HNO, CN and NH3, which may have significant implications for both simulations and observations. We also find that HCO+ may be a useful tracer of disc mass. We conclude that gravitational instabilities induced in lower mass discs can significantly, and permanently, affect the chemical evolution, and that observations with high-resolution instruments such as Atacama Large Millimeter/submillimeter Array (ALMA) offer a promising means of characterizing gravitational instabilities in protosolar discs.

In vivo dynamic stiffness of the porcine lumbar spine exposed to cyclic loading: influence of load and degeneration.

PubMed

Kaigle, A; Ekström, L; Holm, S; Rostedt, M; Hansson, T

1998-02-01

The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.

The Gas Content Of Protoplanetary Herbig Ae/be Discs As Seen With Herschel

NASA Astrophysics Data System (ADS)

Meeus, Gwendolyn; Herschel OTKP, GASPS; Dent, B.

2011-09-01

The mechanisms determining planet formation are not (yet) well-understood. Primordial protoplanetary discs consist 99% out of gas, and only 1% out of dust. With time, those discs are believed to evolve from a flaring geometry into a flat geometry, as the initially small dust grains grow to larger sizes and settle towards the mid-plane. In the mean time, the gas will disperse, until so little is left that giant planets no longer can form. As an important piece of the puzzle of planet formation, it is important to understand the influence of the gas heating/cooling processes on the young disc structure, its chemical composition and finally how fast gas gets dispersed. In this talk, we study the protoplanetary discs around Herbig Ae/Be stars, young objects of intermediate mass, in the context of its gas content. We present Herschel PACS spectroscopic observations for a sample that was obtained within the GASPS (Gas in Protoplanetary Systems) Open Time Key Project, concentrating on the detection and characterisation of emission lines of the [OI], [CII], and CO, tracing the disc between 5 and 500 AU. We look for correlations between the observed line fluxes and stellar properties such as effective temperature, Halpha emission, accretion rates and UV flux, as well as the disc properties: degree of flaring, presence and strength of PAH emission and disc mass. We will present a few cases to show how simultaneous modeling (using the thermo-chemical disc code ProDiMo) of the atomic fine structure lines and both molecular lines can constrain the disc gas mass, once the disc structure is derived. Finally, we compare our gas line observations with those of young debris disc stars, for which the HAEBE stars are thought to be progenitors.

Injectible bodily prosthetics employing methacrylic copolymer gels

DOEpatents

Mallapragada, Surya K.; Anderson, Brian C.

2007-02-27

The present invention provides novel block copolymers as structural supplements for injectible bodily prosthetics employed in medical or cosmetic procedures. The invention also includes the use of such block copolymers as nucleus pulposus replacement materials for the treatment of degenerative disc disorders and spinal injuries. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol) methyl ether polymer.

Debris disc constraints on planetesimal formation

NASA Astrophysics Data System (ADS)

Krivov, Alexander V.; Ide, Aljoscha; Löhne, Torsten; Johansen, Anders; Blum, Jürgen

2018-02-01

Two basic routes for planetesimal formation have been proposed over the last decades. One is a classical `slow-growth' scenario. Another one is particle concentration models, in which small pebbles are concentrated locally and then collapse gravitationally to form planetesimals. Both types of models make certain predictions for the size spectrum and internal structure of newly born planetesimals. We use these predictions as input to simulate collisional evolution of debris discs left after the gas dispersal. The debris disc emission as a function of a system's age computed in these simulations is compared with several Spitzer and Herschel debris disc surveys around A-type stars. We confirm that the observed brightness evolution for the majority of discs can be reproduced by classical models. Further, we find that it is equally consistent with the size distribution of planetesimals predicted by particle concentration models - provided the objects are loosely bound `pebble piles' as these models also predict. Regardless of the assumed planetesimal formation mechanism, explaining the brightest debris discs in the samples uncovers a `disc mass problem'. To reproduce such discs by collisional simulations, a total mass of planetesimals of up to ˜1000 Earth masses is required, which exceeds the total mass of solids available in the protoplanetary progenitors of debris discs. This may indicate that stirring was delayed in some of the bright discs, that giant impacts occurred recently in some of them, that some systems may be younger than previously thought or that non-collisional processes contribute significantly to the dust production.

Growth of carbon nanotubes in arc plasma treated graphite disc: microstructural characterization and electrical conductivity study

NASA Astrophysics Data System (ADS)

Nayak, B. B.; Sahu, R. K.; Dash, T.; Pradhan, S.

2018-03-01

Circular graphite discs were treated in arc plasma by varying arcing time. Analysis of the plasma treated discs by field emission scanning electron microscope revealed globular grain morphologies on the surfaces, but when the same were observed at higher magnification and higher resolution under transmission electron microscope, growth of multiwall carbon nanotubes of around 2 nm diameter was clearly seen. In situ growth of carbon nanotube bundles/bunches consisting of around 0.7 nm tube diameter was marked in the case of 6 min treated disc surface. Both the untreated and the plasma treated graphite discs were characterized by X-ray diffraction, energy dispersive spectra of X-ray, X-ray photoelectron spectroscopy, transmission electron microscopy, micro Raman spectroscopy and BET surface area measurement. From Raman spectra, BET surface area and microstructure observed in transmission electron microscope, growth of several layers of graphene was identified. Four-point probe measurements for electrical resistivity/conductivity of the graphite discs treated under different plasma conditions showed significant increase in conductivity values over that of untreated graphite conductivity value and the best result, i.e., around eightfold increase in conductivity, was observed in the case of 6 min plasma treated sample exhibiting carbon nanotube bundles/bunches grown on disc surface. By comparing the microstructures of the untreated and plasma treated graphite discs, the electrical conductivity increase in graphite disc is attributed to carbon nanotubes (including bundles/bunches) growth on disc surface by plasma treatment.

Evaluation of Surlyn 8920 as PHE Visor Material and Evaluations of New Adhesives for Improving Bonding Between Teflon and Stainless Steel at Cryogenic Temperature

NASA Technical Reports Server (NTRS)

Ray, Asit K.

1991-01-01

Two studies are presented, and in the first study, Surlyn 8920 (an ionic and amorphous low density polyethylene made by Dupont) was evaluated as a possible replacement of Plexyglass G as PHE visor material. Four formulations of the polymer were made by adding different amounts of UV stabilizer, energy quencher, and antioxident in a Brabender Plasticorder. The formulated polymers were molded in the form of sheets in a compression molder. Cut samples from the molded sheets were exposed in a weatherometer and tested on Instron Tensile Tester for strength and elongation. Specially molded samples of the formulated polymers were subjected to Charpy Impact Tests. In the second study, preliminary evaluations of adhesives for improvement of bonding between Teflon and stainless steel (SS) were performed. Kapton, a high temperature polyimide made by Dupont, and a rubber based adhesive made by Potter Paint Co., were evaluated against industrial quality epoxy, the current material used to bond Teflon and SS. The degreased surfaces of the SS discs were etched mechanically, with a few of these etched chemically. The surfaces of the SS discs were etched mechanically, with a few of these etched chemically. Bonding strengths were evaluated using lap shear tests on the Instron Tensile Tester for the samples bonded by Kapton and industrial quality epoxy. Bond strengths were also evaluated using a pull test on the Instron for the samples bonded by Potter adhesive (CWL-152) and industrial quality epoxy. Based on limited lap shear data, Kapton gave bond strength favorable compared to that of industrial epoxy. Based on limited pull test data, Kapton bonded and CWL-152 bonded samples showed poor strength compared to epoxy bonded sample.

Short-term outcomes of anterior fusion-nonfusion hybrid surgery versus posterior cervical laminoplasty in the treatment of multilevel cervical spondylotic myelopathy.

PubMed

Chen, Hua; Liu, Hao; Meng, Yang; Wang, Beiyu; Gong, Quan; Song, Yueming

2018-05-30

To compare short-term clinical and radiological outcomes of anterior fusion-nonfusion hybrid surgery (cervical discectomy or corpectomy and fusion combine with cervical disc replacement) and posterior cervical laminoplasty for multilevel cervical spondylotic myelopathy (CSM). From January 2014 to December 2015, 105 patients who underwent anterior fusion-nonfusion hybrid surgery (AHS group, n=48) or posterior cervical laminoplasty (PCL group, n=57) for ≥3 disc levels CSM were included. Japanese Orthopedic Association (JOA) score, complications, and radiological results including cervical curvature and cervical range of motion (ROM) were compared between the two groups. The complications happened within 1 month after the surgery were recorded as early complication, otherwise would be late complications. Both groups gained significant JOA scores improvement (P<0.05). No significant different of JOA improvement was found between the two groups (P>0.05). The cervical curvature increased significantly in AHS group (P=0.024), whereas decreased significantly in PCL group (P=0.002). Cervical ROM of both two groups significantly decreased after the surgery (P<0.05). The preoperative and final follow-up cervical ROM, together with the total cervical ROM preservation rate were not significant different between the two groups (P>0.05). The AHS group had a significant higher early complication rate (22/48 vs. 15/57, P=0.037) and a lower late complication rate (9/48 vs. 21/57, P=0.041). Both anterior fusion-nonfusion hybrid surgery and cervical laminoplasty could gain satisfied neurological recovery. The anterior hybrid surgery may preserve cervical curvature with higher early complication rate and lower late complication rate than cervical laminoplasty. Copyright © 2018. Published by Elsevier Inc.

Comparison of optic area measurement using fundus photography and optical coherence tomography between optic nerve head drusen and control subjects.

PubMed

Flores-Rodríguez, Patricia; Gili, Pablo; Martín-Ríos, María Dolores; Grifol-Clar, Eulalia

2013-03-01

To compare optic disc area measurement between optic nerve head drusen (ONHD) and control subjects using fundus photography, time-domain optical coherence tomography (TD-OCT) and spectral-domain optical coherence tomography (SD-OCT). We also made a comparison between each of the three techniques. We performed our study on 66 eyes (66 patients) with ONHD and 70 healthy control subjects (70 controls) with colour ocular fundus photography at 20º (Zeiss FF 450 IR plus), TD-OCT (Stratus OCT) with the Fast Optic Disc protocol and SD-OCT (Cirrus OCT) with the Optic Disc Cube 200 × 200 protocol for measurement of the optic disc area. The measurements were made by two observers and in each measurement a correction of the image magnification factor was performed. Measurement comparison using the Student's t-test/Mann-Whitney U test, the intraclass correlation coefficient, Pearson/Spearman rank correlation coefficient and the Bland-Altman plot was performed in the statistical analysis. Mean and standard deviation (SD) of the optic disc area in ONHD and in controls was 2.38 (0.54) mm(2) and 2.54 (0.42) mm(2), respectively with fundus photography; 2.01 (0.56) mm(2) and 1.66 (0.37) mm(2), respectively with TD-OCT, and 2.03 (0.49) mm(2) and 1.75 (0.38) mm(2), respectively with SD-OCT. In ONHD and controls, repeatability of optic disc area measurement was excellent with fundus photography and optical coherence tomography (TD-OCT and SD-OCT), but with a low degree of agreement between both techniques. Optic disc area measurement is smaller in ONHD compared to healthy subjects with fundus photography, unlike time-domain and spectral-domain optical coherence tomography in which the reverse is true. Both techniques offer good repeatability, but a low degree of correlation and agreement, which means that optic disc area measurement is not interchangeable or comparable between techniques. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Study of the Radial Peripapillary Capillary Network in Congenital Optic Disc Anomalies With Optical Coherence Tomography Angiography.

PubMed

Cennamo, Gilda; Rossi, Claudia; Ruggiero, Pasquale; de Crecchio, Giuseppe; Cennamo, Giovanni

2017-04-01

To evaluate the radial peripapillary capillary network with optical coherence tomography angiography (angio-OCT) in morning glory syndrome (MGS), optic disc colobomas, and optic disc pits, and to explore possible correlations between the neural vascular structure and the pathogenesis of congenital optic disc anomalies. Prospective observational comparative case series. Fifteen eyes of 15 patients with congenital optic disc anomalies were enrolled in this study. All patients underwent angio-OCT. The scans were centered on optic discs. The mean age at presentation was 33 years (range: 19-50 years). Congenital optic disc anomalies were identified in all 15 eyes. Three eyes had the characteristic funduscopic signs of MGS, and angio-OCT scans of the peripapillary retina revealed a dense microvascular network. Optic disc colobomas were found in 5 eyes, and the characteristic funduscopic signs of optic pits were found in 7 eyes. Angio-OCT showed the absence of a radial peripapillary microvascular network in these 12 eyes. The finding that angio-OCT scans confirmed the presence of a peripapillary microvascular network only in MGS cases supports the hypothesis that a primary neuroectodermal abnormality and a secondary mesenchymal abnormality leads to MGS. Angio-OCT is a safe, rapid imaging technique that could shed light on the pathogenesis of rare diseases of the optic disc. Copyright © 2016 Elsevier Inc. All rights reserved.

Morphometric Study of the Lumbar Posterior Longitudinal Ligament

PubMed Central

Lee, Sang Beom; Chang, Jae Chil; Lee, Gwang Soo; Hwang, Jae Chan; Bae, Hack Gun; Doh, Jae Won

2018-01-01

Objective Morphometric data for the lumbar posterior longitudinal ligament (PLL) was investigated to identify whether there is a difference in the morphometry of the PLL of the lumbar spine at each level with respect to the pattern of intervertebral disc displacement. Methods In 14 formalin-fixed adult cadavers (12 males and 2 females), from L1 to L5, the authors measured the width and height of the PLL and compared them with other landmarks such as the disc and the pedicle. Results Horizontally, at the upper margin of the disc, the central portion of the superficial PLL covered 17.8–36.9% of the disc width and the fan-like portion of the PLL covered 63.9–76.7% of the disc width. At the level of the median portion of the disc, the PLL covered 69.1–74.5% of the disc width. Vertically, at the level of the medial margin of the pedicle, the fan-like portion of the PLL covered 23.5–29.9% of the disc height. In general, a significant difference in length was not found in the right-left and male-female comparisons. Conclusion This study presents the morphometric data on the pattern of intervertebral disc displacement and helps to improve the knowledge of the surgical anatomy of the lumbar PLL. PMID:29354240

Reliability of gadolinium-enhanced magnetic resonance imaging findings and their correlation with clinical outcome in patients with sciatica.

PubMed

el Barzouhi, Abdelilah; Vleggeert-Lankamp, Carmen L A M; Lycklama à Nijeholt, Geert J; Van der Kallen, Bas F; van den Hout, Wilbert B; Koes, Bart W; Peul, Wilco C

2014-11-01

Gadolinium-enhanced magnetic resonance imaging (Gd-MRI) is often performed in the evaluation of patients with persistent sciatica after lumbar disc surgery. However, correlation between enhancement and clinical findings is debated, and limited data are available regarding the reliability of enhancement findings. To evaluate the reliability of Gd-MRI findings and their correlation with clinical findings in patients with sciatica. Prospective observational evaluation of patients who were enrolled in a randomized trial with 1-year follow-up. Patients with 6- to 12-week sciatica, who participated in a multicentre randomized clinical trial comparing an early surgery strategy with prolonged conservative care with surgery if needed. In total 204 patients underwent Gd-MRI at baseline and after 1 year. Patients were assessed by means of the Roland Disability Questionnaire (RDQ) for sciatica, visual analog scale (VAS) for leg pain, and patient-reported perceived recovery at 1 year. Kappa coefficients were used to assess interobserver reliability. In total, 204 patients underwent Gd-MRI at baseline and after 1 year. Magnetic resonance imaging findings were correlated to the outcome measures using the Mann-Whitney U test for continuous data and Fisher exact tests for categorical data. Poor-to-moderate agreement was observed regarding Gd enhancement of the herniated disc and compressed nerve root (kappa<0.41), which was in contrast with excellent interobserver agreement of the disc level of the herniated disc and compressed nerve root (kappa>0.95). Of the 59 patients with an enhancing herniated disc at 1 year, 86% reported recovery compared with 100% of the 12 patients with nonenhancing herniated discs (p=.34). Of the 12 patients with enhancement of the most affected nerve root at 1 year, 83% reported recovery compared with 85% of the 192 patients with no enhancement (p=.69). Patients with and without enhancing herniated discs or nerve roots at 1 year reported comparable outcomes on RDQ and VAS-leg pain. Reliability of Gd-MRI findings was poor-to-moderate and no correlation was observed between enhancement and clinical findings at 1-year follow-up. Copyright © 2014 Elsevier Inc. All rights reserved.

Comparison of optical coherence tomography and fundus photography for measuring the optic disc size.

PubMed

Neubauer, Aljoscha S; Krieglstein, Tina R; Chryssafis, Christos; Thiel, Martin; Kampik, Anselm

2006-01-01

To assess the agreement and repeatability of optic nerve head (ONH) size measurements by optical coherence tomography (OCT) as compared to conventional planimetry of fundus photographs in normal eyes. For comparison with planimetry the absolute size of the ONH of 25 eyes from 25 normal subjects were measured by both OCT and digital fundus photography (Zeiss FF camera 450). Repeatability of automated Stratus OCT measurements were investigated by repeatedly measuring the optic disc in five normal subjects. Mean disc size was 1763 +/- 186 vertically and 1632 +/- 160 microm horizontally on planimetry. On OCT, values of 1772 +/- 317 microm vertically (p = 0.82) and a significantly smaller horizontal diameter of 1492 +/- 302 microm (p = 0.04) were obtained. The 95% limits of agreement were (-546 microm; +527 microm) for vertical and (-502 microm; +782 microm) for horizontal planimetric compared to OCT measurements. In some cases large discrepancies existed. Repeatability of automatic measurements of the optic disc by OCT was moderately good with intra-class correlation coefficients (ICC) of 0.78 horizontally and 0.83 vertically. The coefficient of repeatability indicating instrument precision was 80 microm for horizontal and 168 microm for vertical measurements. OCT can be used to determine optic disc margins in moderate agreement with planimetry in normal subjects. However, in some cases significant disagreement with photographic assessment may occur making manual inspection advisable. Automatic disc detection by OCT is moderately repeatable.

Mechanical behavior of the human lumbar intervertebral disc with polymeric hydrogel nucleus implant: An experimental and finite element study

NASA Astrophysics Data System (ADS)

Joshi, Abhijeet Bhaskar

The origin of the lower back pain is often the degenerated lumbar intervertebral disc (IVD). We are proposing replacement of the degenerated nucleus by a PVA/PVP polymeric hydrogel implant. We hypothesize that a polymeric hydrogel nucleus implant can restore the normal biomechanics of the denucleated IVD by mimicking the natural load transfer phenomenon as in case of the intact IVD. Lumbar IVDs (n = 15) were harvested from human cadavers. In the first part, specimens were tested in four different conditions for compression: Intact, bone in plug, denucleated and Implanted. Hydrogel nucleus implants were chosen to have line-to-line fit in the created nuclear cavity. In the second part, nucleus implant material (modulus) and geometric (height and diameter) parameters were varied and specimens (n = 9) were tested. Nucleus implants with line-to-line fit significantly restored (88%) the compressive stiffness of the denucleated IVD. The synergistic effect between the implant and the intact annulus resulted in the nonlinear increase in implanted IVD stiffness, where Poisson effect of the hydrogel played major role. Nucleus implant parameters were observed to have a significant effect on the compressive stiffness. All implants with modulus in the tested range restored the compressive stiffness. The undersize implants resulted in incomplete restoration while oversize implants resulted in complete restoration compared to the BI condition. Finite element models (FEM) were developed to simulate the actual test conditions and validated against the experimental results for all conditions. The annulus (defined as hyperelastic, isotropic) mainly determined the nonlinear response of the IVD. Validated FEMs predicted 120--3000 kPa as a feasible range for nucleus implant modulus. FEMs also predicted that overdiameter implant would be more effective than overheight implant in terms of stiffness restoration. Underdiameter implants, initially allowed inward deformation of the annulus and hence were less effective compared to underheight implants. This research successfully proved the feasibility of PVA/PVP polymeric hydrogel as a replacement for degenerated nucleus. This approach may reduce the abnormal stresses on the annulus and thus, prevent/postpone the degeneration of the annulus. A validated FEM can be used as a design tool for optimization of hydrogel nucleus implants design and related feasibility studies.

Comparison of hybrid constructs with 2-level artificial disc replacement and 2-level anterior cervical discectomy and fusion for surgical reconstruction of the cervical spine: a kinematic study in whole cadavers.

PubMed

Liu, Baoge; Zeng, Zheng; Hoof, Tom Van; Kalala, Jean Pierre; Liu, Zhenyu; Wu, Bingxuan

2015-04-08

Multi-level cervical degeneration of the spine is a common clinical pathology that is often repaired by anterior cervical discectomy and fusion (ACDF). The aim of this study was to investigate the kinematics of the cervical spine after hybrid surgery compared with 2-level ACDF. Five freshly frozen, unembalmed whole human cadavers were used including 3 males and 2 females with a mean age of 51 ± 8 years. After evaluating the intact spine for range of motion (ROM), sagittal alignment and instantaneous center of rotation (ICR), each cadaver underwent 4 consecutive surgeries: 2-level artificial disc replacement (ADR) from C4 to C6 (ADR surgery); 2-level ACDF from C4 to C6 (ACDF surgery); hybrid C4-5 ACDF and C5-6 ADR (ACDF+ADR surgery); and hybrid C4-5 ADR and C5-6 ACDF (ADR+ACDF surgery). The ROM and ICR of adjacent intact segments (C3-4; C6-7), and whole sagittal alignment were revaluated. Two-level ACDF resulted in increased ROM at C3-4 and C6-7 compared with intact spine. ROM was significantly different to intact spine using ACDF surgery at C3-C4 and C6-C7 and ROM was increased with ACDF+ADR surgery at C6-C7 (all P<0.05). No improvement in sagittal alignment was observed with any approach. The localization of the ICR shifted upwards and anteriorly at C3-C4 after reconstruction. ICR changes at C3-C4 were greatest for ADR+ACDF surgery and were significantly different to ACDF surgery (P<0.05), but not between ADR surgery and ACDF+ADR surgery. At C6-C7, the ICR was more posterior and superior than in the intact condition. The greatest change in ICR was observed in ACDF surgery at the C6-C7 level, significantly different from the other groups (P<0.05). For 2-level reconstruction, hybrid surgery and ADR did not alter ROM and minimally changed ICR at the adjacent-level. The type of surgery had a significant impact on the ICR location. This suggests that hybrid surgery may be a viable option for 2-level cervical surgery.

Prognosis of intervertebral disc loss from diagnosis of degenerative disc disease

NASA Astrophysics Data System (ADS)

Li, S.; Lin, A.; Tay, K.; Romano, W.; Osman, Said

2015-03-01

Degenerative Disc Disease (DDD) is one of the most common causes of low back pain, and is a major factor in limiting the quality of life of an individual usually as they enter older stages of life, the disc degeneration reduces the shock absorption available which in turn causes pain. Disc loss is one of the central processes in the pathogenesis of DDD. In this study, we investigated whether the image texture features quantified from magnetic resonance imaging (MRI) could be appropriate markers for diagnosis of DDD and prognosis of inter-vertebral disc loss. The main objective is to use simple image based biomarkers to perform prognosis of spinal diseases using non-invasive procedures. Our results from 65 subjects proved the higher success rates of the combination marker compared to the individual markers and in the future, we will extend the study to other spine regions to allow prognosis and diagnosis of DDD for a wider region.

Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis.

PubMed

Ramakrishna, Vivek A S; Chamoli, Uphar; Viglione, Luke L; Tsafnat, Naomi; Diwan, Ashish D

2018-04-02

Spondylolytic (or lytic) spondylolisthesis is often associated with disc degeneration at the index-level; however, it is not clear if disc degeneration is the cause or the consequence of lytic spondylolisthesis. The main objective of this computed tomography based finite element modelling study was to examine the role of different grades of disc degeneration in the progression of a bilateral L5-lytic defect to spondylolisthesis. High-resolution computed tomography data of the lumbosacral spine from an anonymised healthy male subject (26 years old) were segmented to build a 3D-computational model of an INTACT L1-S1 spine. The INTACT model was manipulated to generate four more models representing a bilateral L5-lytic defect and the following states of the L5-S1 disc: nil degeneration (NOR LYTIC), mild degeneration (M-DEG LYTIC), mild degeneration with 50% disc height collapse (M-DEG-COL LYTIC), and severe degeneration with 50% disc height collapse(S-COL LYTIC). The models were imported into a finite element modelling software for pre-processing, running nonlinear-static solves, and post-processing of the results. Compared with the baseline INTACT model, M-DEG LYTIC model experienced the greatest increase in kinematics (Fx range of motion: 73% ↑, Fx intervertebral translation: 53%↑), shear stresses in the annulus (Fx anteroposterior: 163%↑, Fx posteroanterior: 31%↑), and strain in the iliolumbar ligament (Fx: 90%↑). The S-COL LYTIC model experienced a decrease in mobility (Fx range of motion: 48%↓, Fx intervertebral translation: 69%↓) and an increase in normal stresses in the annulus (Fx Tensile: 170%↑; Fx Compressive: 397%↑). No significant difference in results was noted between M-DEG-COL LYTIC and S-COL LYTIC models. In the presence of a bilateral L5 spondylolytic defect, a mildly degenerate index-level disc experienced greater intervertebral motions and shear stresses compared with a severely degenerate index-level disc in flexion and extension bending motions. Disc height collapse, with or without degenerative changes in the stiffness properties of the disc, is one of the plausible re-stabilisation mechanisms available to the L5-S1 motion segment to mitigate increased intervertebral motions and shear stresses due to a bilateral L5 lytic defect.

Standing spin-wave mode structure and linewidth in partially disordered hexagonal arrays of perpendicularly magnetized sub-micron Permalloy discs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, N., E-mail: rossn2282@gmail.com; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au; Stamps, R. L.

2014-09-21

Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs inmore » the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.« less

Accuracy of the actuator disc-RANS approach for predicting the performance and wake of tidal turbines.

PubMed

Batten, W M J; Harrison, M E; Bahaj, A S

2013-02-28

The actuator disc-RANS model has widely been used in wind and tidal energy to predict the wake of a horizontal axis turbine. The model is appropriate where large-scale effects of the turbine on a flow are of interest, for example, when considering environmental impacts, or arrays of devices. The accuracy of the model for modelling the wake of tidal stream turbines has not been demonstrated, and flow predictions presented in the literature for similar modelled scenarios vary significantly. This paper compares the results of the actuator disc-RANS model, where the turbine forces have been derived using a blade-element approach, to experimental data measured in the wake of a scaled turbine. It also compares the results with those of a simpler uniform actuator disc model. The comparisons show that the model is accurate and can predict up to 94 per cent of the variation in the experimental velocity data measured on the centreline of the wake, therefore demonstrating that the actuator disc-RANS model is an accurate approach for modelling a turbine wake, and a conservative approach to predict performance and loads. It can therefore be applied to similar scenarios with confidence.

Static compression down-regulates N-cadherin expression and facilitates loss of cell phenotype of nucleus pulposus cells in a disc perfusion culture.

PubMed

Zhou, Haibo; Shi, Jianmin; Zhang, Chao; Li, Pei

2018-02-28

Mechanical compression often induces degenerative changes of disc nucleus pulposus (NP) tissue. It has been indicated that N-cadherin (N-CDH)-mediated signaling helps to preserve the NP cell phenotype. However, N-CDH expression and the resulting NP-specific phenotype alteration under the static compression and dynamic compression remain unclear. To study the effects of static compression and dynamic compression on N-CDH expression and NP-specific phenotype in an in vitro disc organ culture. Porcine discs were organ cultured in a self-developed mechanically active bioreactor for 7 days and subjected to static or dynamic compression (0.4 MPa for 2 h once per day). The noncompressed discs were used as controls. Compared with the dynamic compression, static compression significantly down-regulated the expression of N-CDH and NP-specific markers (laminin, brachyury, and keratin 19); decreased the Alcian Blue staining intensity, glycosaminoglycan and hydroxyproline contents; and declined the matrix macromolecule (aggrecan and collagen II) expression. Compared with the dynamic compression, static compression causes N-CDH down-regulation, loss of NP-specific phenotype, and the resulting decrease in NP matrix synthesis. © 2018 The Author(s).

Stellar disc destruction by dynamical interactions in the Orion Trapezium star cluster

NASA Astrophysics Data System (ADS)

Portegies Zwart, Simon F.

2016-03-01

We compare the observed size distribution of circumstellar discs in the Orion Trapezium cluster with the results of N-body simulations in which we incorporated an heuristic prescription for the evolution of these discs. In our simulations, the sizes of stellar discs are affected by close encounters with other stars (with discs). We find that the observed distribution of disc sizes in the Orion Trapezium cluster is excellently reproduced by truncation due to dynamical encounters alone. The observed distribution appears to be a sensitive measure of the past dynamical history of the cluster, and therewith on the conditions of the cluster at birth. The best comparison between the observed disc-size distribution and the simulated distribution is realized with a cluster of N = 2500 ± 500 stars with a half-mass radius of about 0.5 pc in virial equilibrium (with a virial ratio of Q = 0.5, or somewhat colder Q ≃ 0.3), and with a density structure according to a fractal dimension of F ≃ 1.6. Simulations with these parameters reproduce the observed distribution of circumstellar discs in about 0.2-0.5 Myr. We conclude that the distribution of disk sizes in the Orion Trapezium cluster is the result of dynamical interactions in the early evolution of the cluster.

Evolution of an accretion disc in binary black hole systems

NASA Astrophysics Data System (ADS)

Kimura, Shigeo S.; Takahashi, Sanemichi Z.; Toma, Kenji

2017-03-01

We investigate evolution of an accretion disc in binary black hole (BBH) systems and possible electromagnetic counterparts of the gravitational waves from mergers of BBHs. Perna et al. proposed a novel evolutionary scenario of an accretion disc in BBHs in which a disc eventually becomes 'dead', I.e. the magnetorotational instability (MRI) becomes inactive. In their scenario, the dead disc survives until a few seconds before the merger event. We improve the dead disc model and propose another scenario, taking account of effects of the tidal torque from the companion and the critical ionization degree for MRI activation more carefully. We find that the mass of the dead disc is much lower than that in the Perna's scenario. When the binary separation sufficiently becomes small, the mass inflow induced by the tidal torque reactivates MRI, restarting mass accretion on to the black hole. We also find that this disc 'revival' happens more than thousands of years before the merger. The mass accretion induced by the tidal torque increases as the separation decreases, and a relativistic jet could be launched before the merger. The emissions from these jets are too faint compared to gamma-ray bursts, but detectable if the merger events happen within ≲10 Mpc or if the masses of the black holes are as massive as ˜105 M⊙.

Thoracolumbar Intervertebral Disc Area Morphometry in Elderly Chinese Men and Women: Radiographic Quantifications at Baseline and Changes at Year-4 Follow-up.

PubMed

Wáng, Jùn-Qīng; Káplár, Zoltán; Deng, Min; Griffith, James F; Leung, Jason C S; Kwok, Anthony W L; Kwok, Timothy; Leung, Ping Chung; Wáng, Yì Xiáng J

2018-05-15

A population-based radiographic study with longitudinal follow-up. To develop a quantitative index for lumbar disc space narrowing (DSN) evaluation in elderly subjects; to determine how DSN in the elderly is influenced by osteoporosis and sex. There is paucity of research on quantitative classification of lumbar DSN based on disc areal morphometry. With the database of Osteoporotic Fractures in Men (Hong Kong) and Osteoporotic Fractures in Women (Hong Kong) Studies and those who attended the year-4 follow-up (n = 1519 for men and n = 1546 for women), data of 491 women and 592 men were randomly selected. The anterior, middle, and posterior heights; anteroposterior diameter; and area of intervertebral discs (T4T5 to L4L5) were measured on lateral radiographs. Disc area index for lumbar spine (DAIL, disc area divided by the mean of the sum of square of the adjacent upper and lower vertebrae mid-height anterior-posterior diameter) was developed and compared with semiquantitative DSN expert grading. DAIL correlated with semiquantitative grading, with sensitivity and specificity varying from 87.3% to 96.8% for grade 1 DSN (<30% reduction in disc height), and 92.9% to 100% for grade 3 DSN (>60% reduction in disc height). The thoracolumbar disc area loss among men and women during 4-years' follow-up period varied between 1.32% and 3.56%, and it was greater for women (mean: 2.44%) than for men (mean: 1.90%, P = 0.044). Majority of lumbar DSN progressions during 72 to 76 years old were progression from normal disc space to grade 1 DSN. Osteoporosis was associated with greater disc area decrease, both for thoracic and lumbar discs. Lumbar DSN can be quantified using DAIL. In elderly Chinese, intervertebral disc narrowing over a 4-year period was greater in women than men, and associated with the presence of osteoporosis. 3.

Molecules in Protoplanetary HAEBE discs as seen with Herschel.

NASA Astrophysics Data System (ADS)

Meeus, G.

2011-05-01

The discovery of planets around other stars has revealed that planet formation is ubiquitous. However, the mechanisms determining planet formation are not (yet) well-understood. Primordial protoplanetary discs consist 99% out of gas, and only 1% out of dust. With time, those discs are believed to evolve from a flaring geometry into a flat geometry, as the initially small dust grains grow to larger sizes and settle towards the mid-plane. In the mean time, the gas will disperse, until so little is left that giant planets no longer can form. It is thus important to understand the chemical composition of the disc and the influence of the gas heating/cooling processes on the disc structure, and finally how gas gets dispersed as a pieces of the puzzle of planet formation. In this contribution, we study the protoplanetary discs around Herbig Ae/Be stars, young objects of intermediate mass, in the context of gas chemistry. We present Herschel PACS spectroscopic observations for a sample that was obtained within the GASPS (Gas in Protoplanetary Systems) Open Time Key Project, concentrating on the detection and characterisation of emission lines of the molecules H20, CO and CH+ (besides [OI] and [CII]), tracing the disc between 5 and 500 AU. We look for correlations between the observed line fluxes and stellar properties such as effective temperature, Halpha emission, accretion rates and UV flux, as well as the disc properties: degree of flaring, presence and strength of PAH emission and disc mass. We will present a few cases to show how simultaneous modeling (using the thermo-chemical disc code ProDiMo) of the atomic fine structure lines and both Space Telescope and ground-based molecular lines can constrain the disc gas mass, once the disc structure is derived (here with the radiative transfer code MCFost). Finally, we compare our gas line observations with those of young debris disc stars, for which the HAEBE stars are thought to be progenitors.

What the Milky Way bulge reveals about the initial metallicity gradients in the disc

NASA Astrophysics Data System (ADS)

Fragkoudi, F.; Di Matteo, P.; Haywood, M.; Khoperskov, S.; Gomez, A.; Schultheis, M.; Combes, F.; Semelin, B.

2017-11-01

We use APOGEE DR13 data to examine the metallicity trends in the Milky Way (MW) bulge and we explore their origin by comparing two N-body models of isolated galaxies that develop a bar and a boxy/peanut (b/p) bulge. Both models have been proposed as scenarios for reconciling a disc origin of the MW bulge with a negative vertical metallicity gradient. The first model is a superposition of co-spatial, I.e. overlapping, disc populations with different scale heights, kinematics, and metallicities. In this model the thick, metal-poor, and centrally concentrated disc populations contribute significantly to the stellar mass budget in the inner galaxy. The second model is a single disc with an initial steep radial metallicity gradient; this disc is mapped by the bar into the b/p bulge in such a way that the vertical metallicity gradient of the MW bulge is reproduced, as has been shown already in previous works in the literature. However, as we show here, the latter model does not reproduce the positive longitudinal metallicity gradient of the inner disc, nor the metal-poor innermost regions seen in the data. On the other hand, the model with co-spatial thin and thick disc populations reproduces all the aforementioned trends. We therefore see that it is possible to reconcile a (primarily) disc origin for the MW bulge with the observed trends in metallicity by mapping the inner thin and thick discs of the MW into a b/p. For this scenario to reproduce the observations, the α-enhanced, metal-poor, thick disc populations must have a significant mass contribution in the inner regions, as has been suggested for the Milky Way.

Disc cell clusters in pathological human intervertebral discs are associated with increased stress protein immunostaining.

PubMed

Sharp, Christopher A; Roberts, Sally; Evans, Helena; Brown, Sharon J

2009-11-01

Intervertebral disc (IVD) cells within the annulus fibrosus (AF) and nucleus pulposus (NP) maintain distinct functional extracellular matrices and operate within a potentially noxious and stressful environment. How disc cells respond to stress and whether stress is responsible for triggering degeneration is unknown. Disc cell proliferation and cluster formation are most marked in degenerate IVDs, possibly indicating attempts at matrix repair. In other tissues, stress proteins increase rapidly after stress protecting cell function and, although implicated in degeneration of articular cartilage, have received little attention in degenerative IVD pathologies. We have compared the distribution of stress protein immunolocalization in pathological and control IVDs. Disc tissues were obtained at surgery from 43 patients with degenerative disc disease (DDD) and herniation, and 12 controls at postmortem. Tissues were immunostained with a polyclonal antibody for heat shock factor 1 (HSF-1) and monoclonal antibodies for the heat shock proteins, Hsp27 and Hsp72, using an indirect immunoperoxidase method. Positively stained cells were expressed as a percentage of the total. Cell cluster formation was also assessed. The proportion of cells in clusters was similar in the AF (both 2%) and NP (8 and 9%) of control and DDD samples, whereas in herniated tissues this was increased (AF 12%, NP 14%). Stress antigen staining tended to be more frequent in clustered rather than in single/doublet cells, and this was significant (P < 0.005) in both the AF and NP of herniated discs. Clustered cells, which are most common in herniated discs, may be mounting a protective response to abnormal environmental factors associated with disc degeneration. A better understanding of the stress response in IVD cells may allow its utilization in disc cell therapies.

Star formation in the outskirts of DDO 154: A top-light IMF in a nearly dormant disc

NASA Astrophysics Data System (ADS)

Watts, Adam B.; Meurer, Gerhardt R.; Lagos, Claudia D. P.; Bruzzese, Sarah M.; Kroupa, Pavel; Jerabkova, Tereza

2018-04-01

We present optical photometry of Hubble Space Telescope (HST) ACS/WFC data of the resolved stellar populations in the outer disc of the dwarf irregular galaxy DDO 154. The photometry reveals that young main sequence stars are almost absent from the outermost HI disc. Instead, most are clustered near the main stellar component of the galaxy. We constrain the stellar initial mass function (IMF) by comparing the luminosity function of the main sequence stars to simulated stellar populations assuming a constant star formation rate over the dynamical timescale. The best-fitting IMF is deficient in high mass stars compared to a canonical Kroupa IMF, with a best-fit slope α = -2.45 and upper mass limit MU = 16 M⊙. This top-light IMF is consistent with predictions of the Integrated Galaxy-wide IMF theory. Combining the HST images with HI data from The HI Nearby Galaxy Survey Treasury (THINGS) we determine the star formation law (SFL) in the outer disc. The fit has a power law exponent N = 2.92 ± 0.22 and zero point A = 4.47 ± 0.65 × 10-7 M⊙ yr-1 kpc-2. This is depressed compared to the Kennicutt-Schmidt Star Formation Law, but consistent with weak star formation observed in diffuse HI environments. Extrapolating the SFL over the outer disc implies that there could be significant star formation occurring that is not detectable in Hα. Last, we determine the Toomre stability parameter Q of the outer disc of DDO 154 using the THINGS HI rotation curve and velocity dispersion map. 72% of the HI in our field has Q ≤ 4 and this incorporates 96% of the observed MS stars. Hence 28% of the HI in the field is largely dormant.

Evaluation of an alternative technique to optimize direct bonding of orthodontic brackets to temporary crowns.

PubMed

Dias, Francilena Maria Campos Santos; Pinzan-Vercelino, Célia Regina Maio; Tavares, Rudys Rodolfo de Jesus; Gurgel, Júlio de Araújo; Bramante, Fausto Silva; Fialho, Melissa Nogueira Proença

2015-01-01

To compare shear bond strength of different direct bonding techniques of orthodontic brackets to acrylic resin surfaces. The sample comprised 64 discs of chemically activated acrylic resin (CAAR) randomly divided into four groups: discs in group 1 were bonded by means of light-cured composite resin (conventional adhesive); discs in group 2 had surfaces roughened with a diamond bur followed by conventional direct bonding by means of light-cured composite resin; discs in group 3 were bonded by means of CAAR (alternative adhesive); and discs in group 4 had surfaces roughened with a diamond bur followed by direct bonding by means of CAAR. Shear bond strength values were determined after 24 hours by means of a universal testing machine at a speed of 0.5 mm/min, and compared by analysis of variance followed by post-hoc Tukey test. Adhesive remnant index (ARI) was measured and compared among groups by means of Kruskal-Wallis and Dunn tests. Groups 3 and 4 had significantly greater shear bond strength values in comparison to groups 1 and 2. Groups 3 and 4 yielded similar results. Group 2 showed better results when compared to group 1. In ARI analyses, groups 1 and 2 predominantly exhibited a score equal to 0, whereas groups 3 and 4 predominantly exhibited a score equal to 3. Direct bonding of brackets to acrylic resin surfaces using CAAR yielded better results than light-cured composite resin. Surface preparation with diamond bur only increased shear bond strength in group 2.

Fluid flow and convective transport of solutes within the intervertebral disc.

PubMed

Ferguson, Stephen J; Ito, Keita; Nolte, Lutz P

2004-02-01

Previous experimental and analytical studies of solute transport in the intervertebral disc have demonstrated that for small molecules diffusive transport alone fulfils the nutritional needs of disc cells. It has been often suggested that fluid flow into and within the disc may enhance the transport of larger molecules. The goal of the study was to predict the influence of load-induced interstitial fluid flow on mass transport in the intervertebral disc. An iterative procedure was used to predict the convective transport of physiologically relevant molecules within the disc. An axisymmetric, poroelastic finite-element structural model of the disc was developed. The diurnal loading was divided into discrete time steps. At each time step, the fluid flow within the disc due to compression or swelling was calculated. A sequentially coupled diffusion/convection model was then employed to calculate solute transport, with a constant concentration of solute being provided at the vascularised endplates and outer annulus. Loading was simulated for a complete diurnal cycle, and the relative convective and diffusive transport was compared for solutes with molecular weights ranging from 400 Da to 40 kDa. Consistent with previous studies, fluid flow did not enhance the transport of low-weight solutes. During swelling, interstitial fluid flow increased the unidirectional penetration of large solutes by approximately 100%. Due to the bi-directional temporal nature of disc loading, however, the net effect of convective transport over a full diurnal cycle was more limited (30% increase). Further study is required to determine the significance of large solutes and the timing of their delivery for disc physiology.

Prevalence of different temporomandibular joint sounds, with emphasis on disc-displacement, in patients with temporomandibular disorders and controls.

PubMed

Elfving, Lars; Helkimo, Martti; Magnusson, Tomas

2002-01-01

Temporomandibular joint (TMJ) sounds are very common among patients with temporomandibular disorders (TMD), but also in non-patient populations. A variety of different causes to TMJ-sounds have been suggested e.g. arthrotic changes in the TMJs, anatomical variations, muscular incoordination and disc displacement. In the present investigation, the prevalence and type of different joint sounds were registered in 125 consecutive patients with suspected TMD and in 125 matched controls. Some kind of joint sound was recorded in 56% of the TMD patients and in 36% of the controls. The awareness of joint sounds was higher among TMD patients as compared to controls (88% and 60% respectively). The most common sound recorded in both groups was reciprocal clickings indicative of a disc displacement, while not one single case fulfilling the criteria for clicking due to a muscular incoordination was found. In the TMD group women with disc displacement reported sleeping on the stomach significantly more often than women without disc displacement did. An increased general joint laxity was found in 39% of the TMD patients with disc displacement, while this was found in only 9% of the patients with disc displacement in the control group. To conclude, disc displacement is probably the most common cause to TMJ sounds, while the existence of TMJ sounds due to a muscular incoordination can be questioned. Furthermore, sleeping on the stomach might be associated with disc displacement, while general joint laxity is probably not a causative factor, but a seeking care factor in patients with disc displacement.

Clinical and radiological analysis of Bryan cervical disc arthroplasty: eight-year follow-up results compared with anterior cervical discectomy and fusion.

PubMed

Lei, Tao; Liu, Yaming; Wang, Hui; Xu, Jiaxin; Ma, Qinghua; Wang, Linfeng; Shen, Yong

2016-06-01

Bryan cervical disc arthroplasty has been reported with satisfactory short- and medium-term clinical results. However, the long-term clinical and radiographic outcomes are seldom reported. The purpose of this study was to compare the eight-year follow-up results in patients who underwent Bryan disc arthroplasty with patients received ACDF, and assess the incidence of heterotopic ossification (HO) and its effect on clinical outcome and mobility of the device. Thirty-one patients underwent Bryan disc arthroplasty, and 35 patients underwent ACDF were included in the study. The Japanese Orthopedic Association (JOA) scores, neck disability index (NDI), visual analogue scale (VAS) of neck and arm pain, and the radiographs were used to evaluate the outcomes. The heterotopic ossification (HO) was determined by CT scan and was classified into three subgroups to compare the related effect. Adjacent segment degeneration (ASD) was also observed. At final follow-up, there were no significant differences in JOA scores between two groups, but the improvement in NDI and neck or arm VAS were significantly greater in the Bryan disc cohort. The range of motion at the index level was 7.0° in Bryan group, while 100 % bone fusion were achieved in ACDF group. HO was observed in 18 (51.4 %) levels. There were more restricted movement of the prosthesis and slight higher rate of axial pain in patients with severe-HO (grade III and IV). Fourteen (28.6 %) levels developed ASD in Bryan group, which was significantly lower than that (58.6 %) in ACDF group. At eight year follow-up, the clinical and radiographic outcomes of Bryan cervical disc arthroplasty compared favorably to those of ACDF. It avoided accelerated adjacent segment degeneration by preserving motion. However, severe HO restricted the ROM of the index levels and maybe associated with post-operative axial pain.

Vortex survival in 3D self-gravitating accretion discs

NASA Astrophysics Data System (ADS)

Lin, Min-Kai; Pierens, Arnaud

2018-07-01

Large-scale, dust-trapping vortices may account for observations of asymmetric protoplanetary discs. Disc vortices are also potential sites for accelerated planetesimal formation by concentrating dust grains. However, in 3D discs vortices are subject to destructive `elliptic instabilities', which reduces their viability as dust traps. The survival of vortices in 3D accretion discs is thus an important issue to address. In this work, we perform shearing box simulations to show that disc self-gravity enhances the survival of 3D vortices, even when self-gravity is weak in the classic sense (e.g. with a Toomre Q ≃ 5). We find a 3D self-gravitating vortex can grow on secular time-scales in spite of the elliptic instability. The vortex aspect ratio decreases as it strengthens, which feeds the elliptic instability. The result is a 3D vortex with a turbulent core that persists for ˜103 orbits. We find when gravitational and hydrodynamic stresses become comparable, the vortex may undergo episodic bursts, which we interpret as an interaction between elliptic and gravitational instabilities. We estimate the distribution of dust particles in self-gravitating, turbulent vortices. Our results suggest large-scale vortices in protoplanetary discs are more easily observed at large radii.

Vortex survival in 3D self-gravitating accretion discs

NASA Astrophysics Data System (ADS)

Lin, Min-Kai; Pierens, Arnaud

2018-04-01

Large-scale, dust-trapping vortices may account for observations of asymmetric protoplanetary discs. Disc vortices are also potential sites for accelerated planetesimal formation by concentrating dust grains. However, in 3D discs vortices are subject to destructive `elliptic instabilities', which reduces their viability as dust traps. The survival of vortices in 3D accretion discs is thus an important issue to address. In this work, we perform shearing box simulations to show that disc self-gravity enhances the survival of 3D vortices, even when self-gravity is weak in the classic sense (e.g. with a Toomre Q ≃ 5). We find a 3D, self-gravitating vortex can grow on secular timescales in spite of the elliptic instability. The vortex aspect-ratio decreases as it strengthens, which feeds the elliptic instability. The result is a 3D vortex with a turbulent core that persists for ˜103 orbits. We find when gravitational and hydrodynamic stresses become comparable, the vortex may undergo episodic bursts, which we interpret as interaction between elliptic and gravitational instabilities. We estimate the distribution of dust particles in self-gravitating, turbulent vortices. Our results suggest large-scale vortices in protoplanetary discs are more easily observed at large radii.

Far-infrared signatures and inner hole sizes of protoplanetary discs undergoing inside-out dust dispersal

NASA Astrophysics Data System (ADS)

Ercolano, Barbara; Koepferl, Christine; Owen, James; Robitaille, Thomas

2015-10-01

By means of radiative transfer simulation, we study the evolution of the far-infrared colours of protoplanetary discs undergoing inside-out dispersal, often referred to as transition discs. We show that a brightening of the mid- and far-infrared emission from these objects is a natural consequence of the removal of the inner disc. Our results can fully explain recent observations of transition discs in the Chamaleon and Lupus star-forming regions from the Herschel Gould Belt Survey, which shows a higher median for the 70 μm (Herschel PACS 1) band of known transition objects compared with primordial discs. Our theoretical results hence support the suggestion that the 70 μm band may be a powerful diagnostic for the identification of transition discs from photometry data, provided that the inner hole is larger than tens of au, depending on spectral type. Furthermore, we show that a comparison of photometry in the K, 12 μm and 70 μm bands to model tracks can provide a rough, but quick estimate of the inner hole size of these objects, provided their inclination is below ˜85° and the inner hole size is again larger than tens of au.

Long-term Evaluation of Cervical Disc Arthroplasty with the Mobi-C© Cervical Disc: A Randomized, Prospective, Multicenter Clinical Trial with Seven-Year Follow-up

PubMed Central

Davis, Reginald J.; Hisey, Michael S.; Nunley, Pierce D.; Hoffman, Gregory A.; Jackson, Robert J.; Bae, Hyun W.; Albert, Todd; Coric, Dom

2017-01-01

Background Cervical total disc replacement (TDR) is an increasingly accepted procedure for the treatment of symptomatic cervical degenerative disc disease. Multiple Level I evidence clinical trials have established cervical TDR to be a safe and effective procedure in the short-term. The objective of this study is to provide a long-term assessment of TDR versus anterior discectomy and fusion for the treatment of one- and two-level disc disease. Methods This study was a continuation of a prospective, multicenter, randomized, US FDA IDE clinical trial comparing cervical TDR with the Mobi-C© Cervical Disc versus ACDF through 7 years follow-up. Inclusion criteria included a diagnosis of symptomatic cervical degenerative disc disease at one or two cervical levels. TDR patients were treated using a Mobi-C© artificial disc (Zimmer Biomet, Austin TX, USA). ACDF with allograft and anterior plate was used as a control treatment. Outcome measures were collected preoperatively and postoperatively at 6 weeks, at 3, 6, 12, 18 months, annually through 60 months, and at 84 months. Measured outcomes included Overall success, Neck Disability Index (NDI), VAS neck and arm pain, segmental range of motion (ROM), patient satisfaction, SF-12 MCS/PCS, major complications, and subsequent surgery rate. The primary endpoint was an FDA composite definition of success comprising clinical improvement and an absence of major complications and secondary surgery events. Results A total of 599 patients were enrolled and treated, with 164 treated with one-level TDR, 225 treated with two-level TDR, 81 treated with one-level ACDF, and 105 treated with two-level ACDF. At seven years, follow-up rates ranged from 73.5% to 84.4% (overall 80.2%). The overall success rates of two level TDR and ACDF patients were 60.8% and 34.2%, respectively (p<0.0001). The overall success rates of one level TDR and ACDF patients were 55.2% and 50%, respectively (p>0.05). Both the single and two level TDR and ACDF groups showed significant improvement from baseline NDI scores, VAS neck and arm pain scores, and SF-12 MCS/PCS scores (p<0.0001). In the single level cohort, there was an increased percentage of TDR patients who reported themselves as “very satisfied” (TDR 90.9% vs ACDF 77.8%; p= 0.028). There was a lower rate of adjacent level secondary surgery in the single level TDR patients (3.7%) versus the ACDF patients (13.6%; p = 0.007). In the two level TDR group, the NDI success rate was significantly greater in the TDR group (TDR: 79.0% vs. ACDF: 58.0%; p=0.001). There was significantly more improvement in NDI change score at 7 years in the TDR patients versus ACDF. The TDR group had a significantly higher rate of patients who were “very satisfied” with their treatment compared to the ACDF group (TDR: 85.9% vs. ACDF: 73.9%). The rate of subsequent surgery at the index level was significantly lower in the TDR group compared to the ACDF group (TDR: 4.4% vs. ACDF: 16.2%; p=0.001). The rate of adjacent level secondary surgery was significantly lower in the two level TDR (4.4%) patients compared to the ACDF (11.3%; p=0.03) patients. In both single and two level cohorts, the percentage of patients with worse NDI (2.5%-3.8% of two level surgeries and 1.2%-2.5% of single level surgeries) or worse neck pain (5%-6.8% of the two level surgeries and 1.3% - 3.8% of the single level surgeries) was strikingly low in both groups but trended lower in the TDR patients. Conclusions At seven years, the composite success analysis demonstrated clinical superiority of two level TDR over ACDF and non-inferiority of single level TDR versus ACDF. There were lower rates of secondary surgery and higher adjacent level disc survivorship in both groups. Both surgeries were remarkably effective in alleviating pain relative to baseline and the rate of patients with worse disability or neck pain was surprisingly low. Overall, greater than 95% of patients (from both groups) who underwent TDR and 88% of patients who underwent ACDF were “very satisfied” at seven years. The differences in clinical effectiveness of TDR versus ACDF becomes more apparent as treatment increases from one to two levels, indicating a significant benefit for TDR over ACDF for two-level procedures. Ethical Standards The Mobi-C Clinical Trial (ClinicalTrials.gov registration number: NCT00389597) was conducted at 24 sites in the US and was approved by the Institutional Review Board, Research Ethics Committee, or local equivalent of each participating site. Level of Evidence 1. PMID:29372135

Temporomandibular Joint Disorders: A Review of Etiology, Clinical Management, and Tissue Engineering Strategies

PubMed Central

Murphy, Meghan K.; MacBarb, Regina F.; Wong, Mark E.; Athanasiou, Kyriacos A.

2015-01-01

Epidemiology reports state temporomandibular joint disorders (TMD) affect up to 25% of the population, yet their etiology and progression are poorly understood. As a result, treatment options are limited and fail to meet the long-term demands of the relatively young patient population. TMD are a class of degenerative musculoskeletal conditions associated with morphological and functional deformities. In up to 70% of cases, TMD are accompanied by malpositioning of the TMJ disc, termed “internal derangement.” Though onset is not well characterized, correlations between internal derangement and osteoarthritic change have been identified. Due to the complex and unique nature of each TMD case, diagnosis requires patient-specific analysis accompanied by various diagnostic modalities. Likewise, treatment requires customized plans to address the specific characteristics of each patient’s disease. In the mechanically demanding and biochemically active environment of the TMJ, therapeutic approaches capable of restoring joint functionality while responding to changes in the joint have become a necessity. Capable of integration and adaptation in the TMJ, one such approach, tissue engineering, carries significant potential in the development of repair and replacement tissues. The following review presents a synopsis of etiology, current treatment methods, and the future of tissue engineering for repairing and/or replacing diseased joint components, specifically the mandibular condyle and TMJ disc. Preceding the current trends in tissue engineering is an analysis of native tissue characterization, toward identifying tissue engineering objectives and validation metrics for restoring healthy and functional structures of the TMJ. PMID:24278954

Temporomandibular disorders: a review of etiology, clinical management, and tissue engineering strategies.

PubMed

Murphy, Meghan K; MacBarb, Regina F; Wong, Mark E; Athanasiou, Kyriacos A

2013-01-01

Temporomandibular disorders (TMD) are a class of degenerative musculoskeletal conditions associated with morphologic and functional deformities that affect up to 25% of the population, but their etiology and progression are poorly understood and, as a result, treatment options are limited. In up to 70% of cases, TMD are accompanied by malpositioning of the temporomandibular joint (TMJ) disc, termed "internal derangement." Although the onset is not well characterized, correlations between internal derangement and osteoarthritic change have been identified. Because of the complex and unique nature of each TMD case, diagnosis requires patient-specific analysis accompanied by various diagnostic modalities. Likewise, treatment requires customized plans to address the specific characteristics of each patient's disease. In the mechanically demanding and biochemically active environment of the TMJ, therapeutic approaches that can restore joint functionality while responding to changes in the joint have become a necessity. One such approach, tissue engineering, which may be capable of integration and adaptation in the TMJ, carries significant potential for the development of repair and replacement tissues. The following review presents a synopsis of etiology, current treatment methods, and the future of tissue engineering for repairing and/or replacing diseased joint components, specifically the mandibular condyle and TMJ disc. An analysis of native tissue characterization to assist clinicians in identifying tissue engineering objectives and validation metrics for restoring healthy and functional structures of the TMJ is followed by a discussion of current trends in tissue engineering.

Performance of the STAR Event Plane Detector

NASA Astrophysics Data System (ADS)

Ewigleben, Justin; Justin Ewigleben Collaboration

2017-09-01

The Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider has shown hints of a critical point and first order phase transition at the BES energies. Key measurements for locating the critical point and determining the first order phase transition are limited by poor event plane resolution, limited statistics and a TPC-only centrality determination. A new event plane and collision centrality detector (EPD) is planned to replace the existing detector, the Beam-Beam Counter (BBC), with higher granularity and acceptance. The design of the EPD consists of two scintillator discs at z = +/- 3.75m from the center of STAR, covering 2.2 < η < 5.1. One quarter of a single disc was installed in STAR for the 2017 run for commissioning. In this talk we will discuss the detector performance during this commissioning run in both proton-proton collisions at √{ s = 510 } GeV and Au-Au collisions at √{sNN = 54.4 } GeV. NSF Grant 1614474.

Strain on intervertebral discs after anterior cervical decompression and fusion.

PubMed

Matsunaga, S; Kabayama, S; Yamamoto, T; Yone, K; Sakou, T; Nakanishi, K

1999-04-01

An analysis of the change in strain distribution of intervertebral discs present after anterior cervical decompression and fusion by an original method. The analytical results were compared to occurrence of herniation of the intervertebral disc on magnetic resonance imaging. To elucidate the influence of anterior cervical decompression and fusion on the unfused segments of the spine. There is no consensus regarding the exact significance of the biomechanical change in the unfused segment present after surgery. Ninety-six patients subjected to anterior cervical decompression and fusion for herniation of intervertebral discs were examined. Shear strain and longitudinal strain of intervertebral discs were analyzed on pre- and postoperative lateral dynamic routine radiography of the cervical spine. Thirty of the 96 patients were examined by magnetic resonance imaging before and after surgery, and the relation between alteration in strains and postsurgical occurrence of disc herniation was examined. In the cases of double- or triple-level fusion, shear strain of adjacent segments had increased 20% on average 1 year after surgery. Thirteen intervertebral discs that had an abnormally high degree of strain showed an increase in longitudinal strain after surgery. Eleven (85%) of the 13 discs that showed an abnormal increase in longitudinal strain had herniation in the same intervertebral discs with compression of the spinal cord during the follow-up period. Relief of symptoms was significantly poor in the patients with recent herniation. Close attention should be paid to long-term biomechanical changes in the unfused segment.

The effect of simulated microgravity on lumbar spine biomechanics: an in vitro study.

PubMed

Laws, Cory J; Berg-Johansen, Britta; Hargens, Alan R; Lotz, Jeffrey C

2016-09-01

Disc herniation risk is quadrupled following spaceflight. This study tested the hypothesis that swelling-induced disc height increases (comparable to those reported in spaceflight) stiffen the spine and elevate annular strain and nuclear pressure during forward bending. Eight human lumbar motion segments were secured to custom-designed testing jigs and subjected to baseline flexion and compression and pure moment flexibility tests. Discs were then free-swelled in saline to varying supraphysiologic heights consistent with prolonged weightlessness and re-tested to assess biomechanical changes. Swelling-induced disc height changes correlated positively with intradiscal pressure (p < 0.01) and stiffening in flexion (p < 0.01), and negatively with flexion range of motion (p < 0.05). Swelling-induced increases in disc height also led to increased annular surface strain under combined flexion with compression. Disc wedge angle decreased with swelling (p < 0.05); this loss of wedge angle correlated with decreased flexion range of motion (R (2) = 0.94, p < 0.0001) and decreased stiffness fold change in extension (p < 0.05). Swelling-induced increases in disc height decrease flexibility and increase annular strain and nuclear pressure during forward bending. These changes, in combination with the measured loss of lordotic curvature with disc swelling, may contribute toward increased herniation risk. This is consistent with clinical observations of increased disc herniation rates after microgravity exposure and may provide the basis for future countermeasure development.

The effect of simulated microgravity on lumbar spine biomechanics: an in vitro study

PubMed Central

Laws, Cory J.; Berg-Johansen, Britta; Hargens, Alan R.; Lotz, Jeffrey C.

2015-01-01

Purpose Disc herniation risk is quadrupled following spaceflight. This study tested the hypothesis that swelling-induced disc height increases (comparable to those reported in spaceflight) stiffen the spine and elevate annular strain and nuclear pressure during forward bending. Methods Eight human lumbar motion segments were secured to custom-designed testing jigs and subjected to baseline flexion and compression and pure moment flexibility tests. Discs were then free-swelled in saline to varying supraphysiologic heights consistent with prolonged weightlessness and re-tested to assess biomechanical changes. Results Swelling-induced disc height changes correlated positively with intradiscal pressure (p < 0.01) and stiffening in flexion (p < 0.01), and negatively with flexion range of motion (p < 0.05). Swelling-induced increases in disc height also led to increased annular surface strain under combined flexion with compression. Disc wedge angle decreased with swelling (p < 0.05); this loss of wedge angle correlated with decreased flexion range of motion (R2 = 0.94, p < 0.0001) and decreased stiffness fold change in extension (p < 0.05). Conclusion Swelling-induced increases in disc height decrease flexibility and increase annular strain and nuclear pressure during forward bending. These changes, in combination with the measured loss of lordotic curvature with disc swelling, may contribute toward increased herniation risk. This is consistent with clinical observations of increased disc herniation rates after microgravity exposure and may provide the basis for future countermeasure development. PMID:26403291

The Formation And Evolution Of Milky Way Sized Galaxies In High-Resolution Cosmological Zoom Simulations

NASA Astrophysics Data System (ADS)

Grand, Robert

2016-09-01

Simulations are playing an increasingly important role in probing the formation history of the Milky Way, including the formation of the thick/thin disc and origin of the metal distribution and chemo-dynamical relations. We introduce the Auriga project, a suite of high resolution cosmological-zoom simulations of Milky Way-sized galaxies simulated with the state-of-the-art cosmological magneto-hydrodynamical code AREPO, and present an analysis of the formation and evolution of the stellar disc(s) from early times to present day. In particular, we show that 'thickened discs' are mainly driven by a bar (if present) and interactions with satellites of masses log10 (M/ Mo ) >= 10, whereas other potential heating mechanisms such as spiral arms, radial migration, and adiabatic heating from mid-plane density growth are all sub-dominant. Interestingly, we find that even in cases of violent satellite interactions the disc reforms quickly (within a few giga years), producing a well-defined disc-bulge system. In nearly all simulations the overall structure of the disc becomes gradually more radially extended and vertically thinner with time, in support of the inside-out, upside-down formation scenario, and without the presence of a thin/thick disc dichotomy. In addition, we comment on the mass distribution of mono-abundance populations and their relation to the bulge and disc components, which are readily comparable to observations from surveys such as APOGEE and Gaia.

Thermal stability of bubble domains in ferromagnetic discs

NASA Astrophysics Data System (ADS)

Hrkac, G.; Bance, S.; Goncharov, A.; Schrefl, T.; Suess, D.

2007-05-01

The transition and thermal stability of disc-shaped ferromagnetic particles at the temperature of T = 300 K with a uniaxial anisotropy along the symmetry axis from a bi-domain to a single domain state has been studied. The nudge elastic band method was used to map the energy landscape and to calculate the energy barrier between the transition states. For single FePt disc-shaped particles with perpendicular anisotropy three transition configurations have been found: single domain, stripe- and stable bubble domains at zero applied field. The single domain configuration along the positive anisotropy axis is reached by an annihilation process of the domain wall and the all-down state by a complex domain expansion process. Magnetization configurations in two interacting discs show an increase in thermal stability compared with single disc systems, which is attributed to the interacting magnetostatic energy between the two particles.

Alignment in star-debris disc systems seen by Herschel

NASA Astrophysics Data System (ADS)

Greaves, J. S.; Kennedy, G. M.; Thureau, N.; Eiroa, C.; Marshall, J. P.; Maldonado, J.; Matthews, B. C.; Olofsson, G.; Barlow, M. J.; Moro-Martín, A.; Sibthorpe, B.; Absil, O.; Ardila, D. R.; Booth, M.; Broekhoven-Fiene, H.; Brown, D. J. A.; Cameron, A. Collier; del Burgo, C.; Di Francesco, J.; Eislöffel, J.; Duchêne, G.; Ertel, S.; Holland, W. S.; Horner, J.; Kalas, P.; Kavelaars, J. J.; Lestrade, J.-F.; Vican, L.; Wilner, D. J.; Wolf, S.; Wyatt, M. C.

2014-02-01

Many nearby main-sequence stars have been searched for debris using the far-infrared Herschel satellite, within the DEBRIS, DUNES and Guaranteed-Time Key Projects. We discuss here 11 stars of spectral types A-M where the stellar inclination is known and can be compared to that of the spatially resolved dust belts. The discs are found to be well aligned with the stellar equators, as in the case of the Sun's Kuiper belt, and unlike many close-in planets seen in transit surveys. The ensemble of stars here can be fitted with a star-disc tilt of ≲ 10°. These results suggest that proposed mechanisms for tilting the star or disc in fact operate rarely. A few systems also host imaged planets, whose orbits at tens of au are aligned with the debris discs, contrary to what might be expected in models where external perturbers induce tilts.

Clinical evaluation of an allogeneic bone matrix containing viable osteogenic cells in patients undergoing one- and two-level posterolateral lumbar arthrodesis with decompressive laminectomy.

PubMed

Musante, David B; Firtha, Michael E; Atkinson, Brent L; Hahn, Rebekah; Ryaby, James T; Linovitz, Raymond J

2016-05-27

Trinity Evolution® cellular bone allograft (TE) possesses the osteogenic, osteoinductive, and osteoconductive elements essential for bone healing. The purpose of this study is to evaluate the radiographic and clinical outcomes when TE is used as a graft extender in combination with locally derived bone in one- and two-level instrumented lumbar posterolateral arthrodeses. In this retrospective evaluation, a consecutive series of subject charts that had posterolateral arthrodesis with TE and a 12-month radiographic follow-up were evaluated. All subjects were diagnosed with degenerative disc disease, radiculopathy, stenosis, and decreased disc height. At 2 weeks and at 3 and 12 months, plain radiographs were performed and the subject's back and leg pain (VAS) was recorded. An evaluation of fusion status was performed at 12 months. The population consisted of 43 subjects and 47 arthrodeses. At 12 months, a fusion rate of 90.7 % of subjects and 89.4 % of surgical levels was observed. High-risk subjects (e.g., diabetes, tobacco use, etc.) had fusion rates comparable to normal patients. Compared with the preoperative leg or back pain level, the postoperative pain levels were significantly (p < 0.0001) improved at every time point. There were no adverse events attributable to TE. Fusion rates using TE were higher than or comparable to fusion rates with autologous iliac crest bone graft that have been reported in the recent literature for posterolateral fusion procedures, and TE fusion rates were not adversely affected by several high-risk patient factors. The positive results provide confidence that TE can safely replace autologous iliac crest bone graft when used as a bone graft extender in combination with locally derived bone in the setting of posterolateral lumbar arthrodesis in patients with or without risk factors for compromised bone healing. Because of the retrospective nature of this study, the trial was not registered.

A radiopaque electrospun scaffold for engineering fibrous musculoskeletal tissues: Scaffold characterization and in vivo applications.

PubMed

Martin, John T; Milby, Andrew H; Ikuta, Kensuke; Poudel, Subash; Pfeifer, Christian G; Elliott, Dawn M; Smith, Harvey E; Mauck, Robert L

2015-10-01

Tissue engineering strategies have emerged in response to the growing prevalence of chronic musculoskeletal conditions, with many of these regenerative methods currently being evaluated in translational animal models. Engineered replacements for fibrous tissues such as the meniscus, annulus fibrosus, tendons, and ligaments are subjected to challenging physiologic loads, and are difficult to track in vivo using standard techniques. The diagnosis and treatment of musculoskeletal conditions depends heavily on radiographic assessment, and a number of currently available implants utilize radiopaque markers to facilitate in vivo imaging. In this study, we developed a nanofibrous scaffold in which individual fibers included radiopaque nanoparticles. Inclusion of radiopaque particles increased the tensile modulus of the scaffold and imparted radiation attenuation within the range of cortical bone. When scaffolds were seeded with bovine mesenchymal stem cells in vitro, there was no change in cell proliferation and no evidence of promiscuous conversion to an osteogenic phenotype. Scaffolds were implanted ex vivo in a model of a meniscal tear in a bovine joint and in vivo in a model of total disc replacement in the rat coccygeal spine (tail), and were visualized via fluoroscopy and microcomputed tomography. In the disc replacement model, histological analysis at 4 weeks showed that the scaffold was biocompatible and supported the deposition of fibrous tissue in vivo. Nanofibrous scaffolds that include radiopaque nanoparticles provide a biocompatible template with sufficient radiopacity for in vivo visualization in both small and large animal models. This radiopacity may facilitate image-guided implantation and non-invasive long-term evaluation of scaffold location and performance. The healing capacity of fibrous musculoskeletal tissues is limited, and injury or degeneration of these tissues compromises the standard of living of millions in the US. Tissue engineering repair strategies for the intervertebral disc, meniscus, tendon and ligament have progressed from in vitro to in vivo evaluation using a variety of animal models, and the clinical application of these technologies is imminent. The composition of most scaffold materials however does not allow for visualization by methods available to clinicians (e.g., radiography), and thus it is not possible to assess their performance in situ. In this work, we describe a radiopaque nanofibrous scaffold that can be visualized radiographically in both small and large animal models and serve as a framework for the development of an engineered fibrous tissue. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Assessment of methicillin resistant Staphylococcus Aureus detection methods: analytical comparative study.

PubMed

Ibrahim, Omer Mohammed Ali; Bilal, Naser Eldin; Osman, Omran Fadl; Magzoub, Magzoub Abbas

2017-01-01

The heterogeneous expression of methicillin resistance in Staphylococcus aureus (MRSA) affects the efficiency of tests available to detect it. The objective of this study was to assess four phenotypic tests used to detect MRSA. This is an analytical comparative study conducted among sudanese patients during period from May 2012 to July 2014, Staphylococcus aureus strains were isolated and identified by conventional methods, and then confirmed by PCR detection of coagulase gene. PCR detection of mecA gene was used as a gold standard to assess oxacillin resistance screen agar base (ORSAB), oxacillin disc, cefoxitin disc (at different temperatures and incubation periods) and MRSA-latex agglutination test. S.aureus ATCC 25923 was used as control. Sensitivity and specificity were calculated. MRSA- latex agglutination was the most accurate test; it showed 100% of both sensitivity and specificity, followed by cefoxitin disc with sensitivity of 98.48% and specificity of 100%. However, both of oxacillin disc and oxacillin resistance screen agar base showed less accurate results, and were affected by incubation periods. Oxacillin disc after 24 h incubation both at 30°C and 35°C showed sensitivity and specificity values of 87.88% and 96.23%, respectively. However, after 48h incubation the test at 30°C showed sensitivity and specificity values of 89.39%, and 94.34%, respectively. At 35°C (48h) it showed values of 89.39%, 92.45% respectively. Specificity of ORSAB was more than oxacillin disc at 35°C after 24h incubation 98.11% and 96.23%, respectively. MRSA- latex agglutination and cefoxitin disc diffusion tests are recommended for routine detection of MRSA.

Biomechanical Changes in Disc Pressure and Facet Strain after Lumbar Spinal Arthroplasty with CharitéTM in the Human Cadaveric Spine under Physiologic Compressive Follower Preload.

PubMed

Choi, Jong-Il; Kim, Se-Hoon; Lim, Dong-Jun; Ha, Sung-Kon; Kim, Sang-Dae

2017-01-01

Arthroplasty maintains the biomechanical features of a healthy disc, decreases the adjacent segment disease rate, and decreases the accelerated degeneration rate of the neighboring discs in traditional fusion procedures. However, there are only a few reports on adjacent disc pressure (DP) and facet strain (FS) after lumbar arthroplasty under a physiologic compressive preload. Baseline DP and FS measurements were obtained from five intact cadaveric human lumbosacral spines for different modes of motion. DP was measured by inserting pressure transducer needle tips into the L3-L4 and L5-S1 discs. FS gauges were fixed on both sides of the laminae near the L3-L4, L4-L5, and L5-S1 facet joints. After SB Charité < sup > TM < /sup > III implantation at the L4-L5 level, the measurements were repeated at preload and compared with those of the intact spine. Under the preload condition, the central DP of the upper disc was decreased during extension and bending, and it significantly increased during rotation (p < 0.05). In the lower disc, the central DP insignificantly decreased during bending and increased during extension and flexion. A statistically significant increase in FS was observed during rotation at the operative facet (p < 0.05). Compared to the intact spine, all FS values were insignificantly decreased during lateral bending but increased during axial rotation. In an ex-vivo physiologic preload setting, the SB Charité < sup > TM < /sup > III provided relatively inconsistent and sometimes increased DP or FS at the operative and adjacent levels after arthroplasty.

Galaxy Zoo: secular evolution of barred galaxies from structural decomposition of multiband images

NASA Astrophysics Data System (ADS)

Kruk, Sandor J.; Lintott, Chris J.; Bamford, Steven P.; Masters, Karen L.; Simmons, Brooke D.; Häußler, Boris; Cardamone, Carolin N.; Hart, Ross E.; Kelvin, Lee; Schawinski, Kevin; Smethurst, Rebecca J.; Vika, Marina

2018-02-01

We present the results of two-component (disc+bar) and three-component (disc+bar+bulge) multiwavelength 2D photometric decompositions of barred galaxies in five Sloan Digital Sky Survey (SDSS) bands (ugriz). This sample of ∼3500 nearby (z < 0.06) galaxies with strong bars selected from the Galaxy Zoo citizen science project is the largest sample of barred galaxies to be studied using photometric decompositions that include a bar component. With detailed structural analysis, we obtain physical quantities such as the bar- and bulge-to-total luminosity ratios, effective radii, Sérsic indices and colours of the individual components. We observe a clear difference in the colours of the components, the discs being bluer than the bars and bulges. An overwhelming fraction of bulge components have Sérsic indices consistent with being pseudo-bulges. By comparing the barred galaxies with a mass-matched and volume-limited sample of unbarred galaxies, we examine the connection between the presence of a large-scale galactic bar and the properties of discs and bulges. We find that the discs of unbarred galaxies are significantly bluer compared to the discs of barred galaxies, while there is no significant difference in the colours of the bulges. We find possible evidence of secular evolution via bars that leads to the build-up of pseudo-bulges and to the quenching of star formation in the discs. We identify a subsample of unbarred galaxies with an inner lens/oval and find that their properties are similar to barred galaxies, consistent with an evolutionary scenario in which bars dissolve into lenses. This scenario deserves further investigation through both theoretical and observational work.

Effects of radial compression on a novel simulated intervertebral disc-like assembly using bone marrow-derived mesenchymal stem cell cell-sheets for annulus fibrosus regeneration.

PubMed

See, Eugene Yong-Shun; Toh, Siew Lok; Goh, James Cho-Hong

2011-10-01

The aim of this study was to develop a tissue engineering approach in regenerating the annulus fibrosus (AF) as part of an overall strategy to produce a tissue-engineered intervertebral disc (IVD) replacement. To determine whether a rehabilitative simulation regime on bone marrow–derived mesenchymal stem cell cell-sheet is able to aid the regeneration of the AF. No previous study has used bone marrow–derived mesenchymal stem cell cell-sheets simulated by a rehabilitative regime to regenerate the AF. The approach was to use bone marrow–derived stem cells to form cell-sheets and incorporating them onto silk scaffolds to simulate the native lamellae of the AF. The in vitro experimental model used to study the efficacy of such a system was made up of the tissue engineering AF construct wrapped around a silicone disc to form a simulated IVD-like assembly. The assembly was cultured within a custom-designed bioreactor that provided a compressive mechanical stimulation onto the silicone disc. The silicone nucleus pulposus would bulge radially and compress the simulated AF to mimic the physiological conditions. The simulated IVD-like assembly was compressed using a rehabilitative regime that lasted for 4 weeks at 0.25 Hz, for 15 minutes each day. With the rehabilitative regime, the cell-sheets remained viable but showed a decrease in cell numbers and viability. Gene expression analysis showed significant upregulation of IVD-related genes and there was an increased ratio of collagen type II to collagen type I found within the extracellular matrix. The results suggested that a rehabilitative regime caused extensive remodeling to take place within the simulated IVD-like assembly, producing extracellular matrix similar to that found in the inner AF.

Physical examination, magnetic resonance image, and electrodiagnostic study in patients with lumbosacral disc herniation or spinal stenosis.

PubMed

Lee, Jung Hwan; Lee, Sang-Ho

2012-10-01

To compare the clinical implications of electro-diagnostic study with those of magnetic resonance imaging in patients with lumbosacral intervertebral herniated disc or spinal stenosis. Retrospective study of clinical data. Patients with lumbosacral intervertebral herniated disc or spinal stenosis, diagnosed by clinical assessment and magnetic resonance imaging (MRI), were selected. A total of 753 patients (437 with lumbosacral intervertebral herniated disc and 316 with spinal stenosis) were included in the study. Clinical data for electrodiagnostic study (EDX)and MRI were compared and the sensitivity and specificity of these studies were evaluated. Among all subjects, 267 had radiculopathy on EDX (EDX (+)) and 486 no radiculopathy (EDX(-)). Furthermore, 391 had root compression on MRI (MRI (+)) and 362 no root compression on MRI (MRI (-)). Patients with radioculopathy on EDX (+) showed a significantly higher visual analogue scale score for radiating pain and a higher Oswestry Disability Index than those with negative findings by EDX (-) in the total subjects group and the lumbosacral intervertebral herniated disc subgroup, and there was a trend toward higher Oswestry Disability Index in the spinal stenosis subgroup. Although patients with radioculopathy on root compression on MRI (+) also had a higher visual analogue scale for radiating pain than patients with negative findings by MRI (-) in the total subjects group and the lumbosacral intervertebral herniated disc subgroup, no significant difference was seen in the Oswestry Disability Index. EDX revealed a significant correlation with muscle weakness in the total subjects group and the lumbosacral intervertebral herniated disc subgroup, and trends toward muscle weakness in the spinal stenosis subgroup, whereas there was no such significant correlation for MRI findings in any group. Electrodiagnostic study had a higher specificity in terms of physical examination data than MRI, in spite of its lower sensitivity. Electrodiagnostic study was significantly more correlated with clinical data, especially leg muscle weakness and functional status, and showed a higher specificity than MRI in patients with lumbosacral intervertebral herniated disc or spinal stenosis.

Diffusion-Weighted MRI Assessment of Adjacent Disc Degeneration After Thoracolumbar Vertebral Fractures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noriega, David C., E-mail: dcnoriega1970@gmail.com; Marcia, Stefano, E-mail: stemarcia@gmail.com; Ardura, Francisco, E-mail: fardura@ono.com

ObjectiveThe purpose of this study was to assess, by the mean apparent diffusion coefficient (ADC), if a relationship exists between disc ADC and MR findings of adjacent disc degeneration after thoracolumbar fractures treated by anatomic reduction using vertebral augmentation (VAP).Materials and MethodsTwenty non-consecutive patients (mean age 50.7 years; range 45–56) treated because of vertebral fractures, were included in this study. There were 10 A3.1 and 10 A1.2 fractures (AO classification). Surgical treatment using VAP was applied in 14 cases, and conservative in 6 patients. MRI T2-weighted images and mapping of apparent diffusion coefficient (ADC) of the intervertebral disc adjacent to themore » fractured segment were performed after a mean follow-up of 32 months. A total of 60 discs, 3 per patient, were analysed: infra-adjacent, supra-adjacent and a control disc one level above the supra-adjacent.ResultsNo differences between patients surgically treated and those following a conservative protocol regarding the average ADC values obtained in the 20 control discs analysed were found. Considering all discs, average ADC in the supra-adjacent level was lower than in the infra-adjacent (1.35 ± 0.12 vs. 1.53 ± 0.06; p < 0.001). Average ADC values of the discs used as a control were similar to those of the infra-adjacent level (1.54 ± 0.06). Compared to surgically treated patients, discs at the supra-adjacent fracture level showed statistically significant lower values in cases treated conservatively (p < 0.001). The variation in the delay of surgery had no influence on the average values of ADC at any of the measured levels.ConclusionsADC measurements of the supra-adjacent discs after a mean follow-up of 32 months following thoracolumbar fractures, showed that restoration of the vertebral collapse by minimally invasive VAP prevents posttraumatic disc degeneration.« less

Comparison of radiographic changes after ACDF versus Bryan disc arthroplasty in single and bi-level cases

PubMed Central

Limson, Marc Anthony; Kim, Soo-Bum; Arbatin, Jose Joefrey F.; Chang, Kee-Young; Park, Moon-Soo; Shin, Jae-hyuk; Ju, Yeong-Su

2009-01-01

The object of this study is to compare radiographic outcomes of anterior cervical decompression and fusion (ACDF) versus cervical disc replacement using the Bryan Cervical Disc Prosthesis (Medtronic Sofamor Danek, Memphis, TN) in terms of range of motion (ROM), Functional spinal unit (FSU), overall sagittal alignment (C2–C7), anterior intervertebral height (AIH), posterior intervertebral height (PIH) and radiographic changes at the implanted and adjacent levels. The study consisted of 105 patients. A total of 63 Bryan disc were placed in 51 patients. A single level procedure was performed in 39 patients and a two-level procedure in the other 12. Fifty-four patients underwent ACDF, 26 single level cases and 28 double level cases. The Bryan group had a mean follow-up 19 months (12–38). Mean follow-up for the ACDF group was 20 months (12–40 months). All patients were evaluated using static and dynamic cervical spine radiographs as well as MR imaging. All patients underwent anterior cervical discectomy followed by autogenous bone graft with plate (or implantation of a cage) or the Bryan artificial disc prosthesis. Clinical evaluation included the visual analogue scale (VAS), and neck disability index (NDI). Radiographic evaluation included static and dynamic flexion-extension radiographs using the computer software (Infinitt PiviewSTAR 5051) program. ROM, disc space angle, intervertebral height were measured at the operative site and adjacent levels. FSU and overall sagittal alignment (C2–C7) were also measured pre-operatively, postoperatively and at final follow-up. Radiological change was analyzed using χ2 test (95% confidence interval). Other data were analyzed using the mixed model (SAS enterprises guide 4.1 versions). There was clinical improvement within each group in terms of VAS and NDI scores from pre-op to final follow-up but not significantly between the two groups for both single (VAS p = 0.8371, NDI p = 0.2872) and double (VAS p = 0.2938, NDI p = 0.6753) level surgeries. Overall, ROM and intervertebral height was relatively well maintained during the follow-up in the Bryan group compared to ACDF. Regardless of the number of levels operated on, significant differences were noted for overall ROM of the cervical spine (p < 0.0001) and all other levels except at the upper adjacent level for single level surgeries (p = 0.2872). Statistically significant (p < 0.0001 and p = 0.0172) differences in the trend of intervertebral height measurements between the two groups were noted at all levels except for the AIH of single level surgeries at the upper (p = 0.1264) and lower (p = 0.7598) adjacent levels as well as PIH for double level surgeries at the upper (p = 0.8363) adjacent level. Radiological change was 3.5 times more observed for the ACDF group. Clinical status of both groups, regardless of the number of levels, showed improvement. Although clinical outcomes between the two groups were not significantly different at final follow-up, radiographic parameters, namely ROM and intervertebral heights at the operated site, some adjacent levels as well as FSU and overall sagittal alignment of the cervical spine were relatively well maintained in Bryan group compared to ACDF group. We surmise that to a certain degree, the maintenance of these parameters could contribute to reduce development of adjacent level change. Noteworthy is that radiographic change was 3.5 times more observed for ACDF surgeries. A longer period of evaluation is needed, to see if all these radiographic changes will translate to symptomatic adjacent level disease. PMID:19127374

Comparing Blast Effects on Human Torso Finite Element Model against Existing Lethality Curves

DTIC Science & Technology

2010-07-15

vertebrae, intervertebral discs, ribs, cartilage, sternum, scapula, and clavicle . The internal organs include the heart and aorta, lungs and trachea...Thoracic Vertebrae  Intervertebral Disc  Scapula  Clavicle Heritage Style Viewgraphs6 HTFEM Development Internal Organs Ten-noded tetrahedral

Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia.

PubMed

Goldspink, Lauren K; Mollinger, Joanne L; Barnes, Tamsin S; Groves, Mitchell; Mahony, Timothy J; Gibson, Justine S

2015-02-01

This study investigated antimicrobial resistance traits, clonal relationships and epidemiology of Histophilus somni isolated from clinically affected cattle in Queensland and New South Wales, Australia. Isolates (n = 53) were subjected to antimicrobial susceptibility testing against six antimicrobial agents (ceftiofur, enrofloxacin, florfenicol, tetracycline, tilmicosin and tulathromycin) using disc diffusion and minimum inhibitory concentration (MIC) assays. Clonal relationships were assessed using repetitive sequence PCR and descriptive epidemiological analysis was performed. The H. somni isolates appeared to be geographically clonal, with 27/53 (47%) isolates grouping in one cluster from one Australian state. On the basis of disc diffusion, 34/53 (64%) isolates were susceptible to all antimicrobial agents tested; there was intermediate susceptibility to tulathromycin in 12 isolates, tilmicosin in seven isolates and resistance to tilmicosin in one isolate. Using MIC, all but one isolate was susceptible to all antimicrobial agents tested; the non-susceptible isolate was resistant to tetracycline, but this MIC result could not be compared to disc diffusion, since there are no interpretative guidelines for disc diffusion for H. somni against tetracycline. In this study, there was little evidence of antimicrobial resistance in H. somni isolates from Australian cattle. Disc diffusion susceptibility testing results were comparable to MIC results for most antimicrobial agents tested; however, results for isolates with intermediate susceptibility or resistance to tilmicosin and tulathromycin on disc diffusion should be interpreted with caution in the absence of MIC results. Copyright © 2014 Elsevier Ltd. All rights reserved.

Comparison of the intervertebral disc spaces between axial and anterior lean cervical traction.

PubMed

Chung, Chin-Teng; Tsai, Sen-Wei; Chen, Chun-Jung; Wu, Ting-Chung; Wang, David; Lan, Haw-Chang H; Wu, Shyi-Kuen

2009-11-01

The insufficient investigations on the changes of spinal structures during traction prevent further exploring the possible therapeutic mechanism of cervical traction. A blind randomized crossover-design study was conducted to quantitatively compare the intervertebral disc spaces between axial and anterior lean cervical traction in sitting position. A total of 96 radiographic images from the baseline measurements, axial and anterior lean tractions in 32 asymptomatic subjects were digitized for further analysis. The intra- and inter-examiner reliabilities for measuring the intervertebral disc spaces were in good ranges (ICCs = 0.928-0.942). With the application of anterior lean traction, the statistical increases were detected both in anterior and in posterior disc spaces compared to the baseline (0.29 mm and 0.24 mm; both P < 0.01) and axial traction (0.16 mm and 0.35 mm; both P < 0.01). The greater intervertebral disc spaces obtained during anterior lean traction might be associated with the more even distribution of traction forces over the anterior and posterior neck structures. The neck extension moment through mandible that generally occurred in the axial traction could be counteracted by the downward force of head weight during anterior lean traction. This study quantitatively demonstrated that anterior lean traction in sitting position provided more intervertebral disc space enlargements in both anterior and posterior aspects than axial traction did. These findings may serve as a therapeutic reference when cervical traction is suggested.

Age-related change and sex difference over 60s in disc-fovea angle in Japanese population: the Nagahama Study.

PubMed

Miyata, Manabu; Yoshikawa, Munemitsu; Ohtsuki, Hiroshi; Muraoka, Yuki; Hata, Masayuki; Yokota, Satoshi; Fujimoto, Masahiro; Miyake, Masahiro; Tabara, Yasuharu; Matsuda, Fumihiko; Yoshimura, Nagahisa

2018-01-25

To analyse the disc-fovea angle (DFA) by age group and to compare sex differences in each age group in a large cohort population. This community-based cross-sectional cohort study included 9682 eyes of 9682 volunteers (aged 30-75 years). We measured the DFA, which is the angle between a horizontal line and a line connecting the fovea with the centroid of an optic disc on fundus photographs of the right eye. We manually marked the fovea and surrounded the optic disc. The centroid of an optic disc and the DFA was automatically calculated using originally developed software. We compared the DFA between age groups in 10-year increments and investigated sex differences of DFA in each age group. Overall mean DFA was 6.32 ± 3.53°. The DFA of older subjects was significantly larger than that of younger subjects (p < 0.001). The DFA of women was larger than that of men in their 60s and 70s (p < 0.001 for both), but not in subjects in their 30s, 40s and 50s. Larger DFA in women than in men in their 60s and 70s suggests the possibility that age-related excyclo-shift occurs more easily in postmenopausal women compared to men of the same age. © 2018 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Discover cervical disc arthroplasty versus anterior cervical discectomy and fusion in symptomatic cervical disc diseases: A meta-analysis.

PubMed

Shangguan, Lei; Ning, Guang-Zhi; Tang, Yu; Wang, Zhe; Luo, Zhuo-Jing; Zhou, Yue

2017-01-01

Symptomatic cervical disc disease (SCDD) is a common degenerative disease, and Discover artificial cervical disc, a new-generation nonconstrained artificial disk, has been developed and performed gradually to treat it. We performed this meta-analysis to compare the efficacy and safety between Discover cervical disc arthroplasty (DCDA) and anterior cervical discectomy and fusion (ACDF) for SCDD. An exhaustive literature search of PubMed, EMBASE, and the Cochrane Library was conducted to identify randomized controlled trials that compared DCDA with ACDF for patients suffering SCDD. A random-effect model was used. Results were reported as standardized mean difference or risk ratio with 95% confidence interval. Of 33 articles identified, six studies were included. Compared with ACDF, DCDA demonstrated shorter operation time (P < 0.0001), and better range of motion (ROM) at the operative level (P < 0.00001). But no significant differences were observed in blood loss, neck disability index (NDI) scores, neck and arm pain scores, Japanese orthopaedic association (JOA) scores, secondary surgery procedures and adverse events (P > 0.05). Subgroup analyses did not demonstrated significant differences. In conclusion, DCDA presented shorter operation time, and better ROM at the operative level. However, no significant differences were observed in blood loss, NDI scores, neck and arm pain scores, JOA scores, secondary surgery procedures and adverse events between the two groups. Additionally, more studies of high quality with mid- to long-term follow-up are required in future.

Effects of annulus defects and implantation of poly(lactic-co-glycolic acid) (PLGA)/fibrin gel scaffolds on nerves ingrowth in a rabbit model of annular injury disc degeneration.

PubMed

Xin, Long; Xu, Weixing; Yu, Leijun; Fan, Shunwu; Wang, Wei; Yu, Fang; Wang, Zhenbin

2017-05-12

Growth of nerve fibers has been shown to occur in a rabbit model of intravertebral disc degeneration (IVD) induced by needle puncture. As nerve growth may underlie the process of chronic pain in humans affected by disc degeneration, we sought to investigate the factors underlying nerve ingrowth in a minimally invasive annulotomy rabbit model of IVD by comparing the effects of empty disc defects with those of defects filled with poly(lactic-co-glycolic acid)/fibrin gel (PLGA) plugs. New Zealand white rabbits (n = 24) received annular injuries at three lumbar levels (L3/4, L4/5, and L5/6). The discs were randomly assigned to four groups: (a) annular defect (1.8-mm diameter; 4-mm depth) by mini-trephine, (b) annular defect implanted with a PLGA scaffold containing a fibrin gel, (c) annular puncture by a 16G needle (5-mm depth), and (d) uninjured L2/3 disc (control). Disc degeneration was evaluated by radiography, MRI, histology, real-time PCR, and analysis of proteoglycan (PG) content. Nerve ingrowth into the discs was assessed by immunostaining with the nerve marker protein gene product 9.5. Injured discs showed a progressive disc space narrowing with significant disc degeneration and proteoglycan loss, as confirmed by imaging results, molecular and compositional analysis, and histological examinations. In 16G punctured discs, nerve ingrowth was observed on the surface of scar tissue. In annular defects, nerve fibers were found to be distributed along small fissures within the fibrocartilaginous-like tissue that filled the AF. In discs filled with PLGA/ fibrin gel, more nerve fibers were observed growing deeper into the inner AF along the open annular track.  In addition, innervations scores showed significantly higher than those of punctured discs and empty defects. A limited vascular proliferation was found in the injured sites and regenerated tissues. Nerve ingrowth was significantly higher in PLGA/fibrin-filled discs than in empty defects. Possible explanations include (i) annular fissures along the defect and early loss of proteoglycan may facilitate the ingrowth process and (ii) biodegradable PLGA/fibrin gel may promote adverse growth of nerves and blood vessels into deeper parts of injured disc. The rabbit annular defect model of disc degeneration appears suitable to investigate the effects of nerve ingrowth in relation to pain generation.

The reports of thick discs' deaths are greatly exaggerated. Thick discs are NOT artefacts caused by diffuse scattered light

NASA Astrophysics Data System (ADS)

Comerón, S.; Salo, H.; Knapen, J. H.

2018-02-01

Recent studies have made the community aware of the importance of accounting for scattered light when examining low-surface-brightness galaxy features such as thick discs. In our past studies of the thick discs of edge-on galaxies in the Spitzer Survey of Stellar Structure in Galaxies - the S4G - we modelled the point spread function as a Gaussian. In this paper we re-examine our results using a revised point spread function model that accounts for extended wings out to more than 2\\farcm5. We study the 3.6 μm images of 141 edge-on galaxies from the S4G and its early-type galaxy extension. Thus, we more than double the samples examined in our past studies. We decompose the surface-brightness profiles of the galaxies perpendicular to their mid-planes assuming that discs are made of two stellar discs in hydrostatic equilibrium. We decompose the axial surface-brightness profiles of galaxies to model the central mass concentration - described by a Sérsic function - and the disc - described by a broken exponential disc seen edge-on. Our improved treatment fully confirms the ubiquitous occurrence of thick discs. The main difference between our current fits and those presented in our previous papers is that now the scattered light from the thin disc dominates the surface brightness at levels below μ 26 mag arcsec-2. We stress that those extended thin disc tails are not physical, but pure scattered light. This change, however, does not drastically affect any of our previously presented results: 1) Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere. 2) Thick discs have masses comparable to those of thin discs in low-mass galaxies - with circular velocities vc< 120 km s-1 - whereas they are typically less massive than the thin discs in high-mass galaxies. 3) Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir. 4) Approximately 50% of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest. Data of Figs. B.1 and C.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A5

Research on anti crack mechanism of bionic coupling brake disc

NASA Astrophysics Data System (ADS)

Shi, Lifeng; Yang, Xiao; Zheng, Lingnan; Wu, Can; Ni, Jing

2017-09-01

According to the biological function of fatigue resistance possessed by biology, this study designed a Bionic Coupling Brake Disc (BCBD) which can inhibit crack propagation as the result of improving fatigue property. Thermal stress field of brake disc was calculated under emergency working condition, and circumferential and radial stress field which lead to fatigue failure of brake disc were investigated simultaneously. Results showed that the maximum temperature of surface reached 890°C and the maximum residual tensile stress was 207 Mpa when the initial velocity of vehicle was 200 km/h. Based on the theory of elastic plastic fracture mechanics, the crack opening displacement and the crack front J integrals of the BCBD and traditional brake disc (TBD) with pre-cracking were calculated, and the strength of crack front was compared. Results revealed the growth behavior of fatigue crack located on surface of brake disc, and proved the anti fatigue resistance of BCBD was better, and the strength of crack resistance of BCBD was much stronger than that of TBD. This simulation research provided significant references for optimization and manufacturing of BCBD.

A 1q42 Deletion Involving DISC1, DISC2, and TSNAX in an Autism Spectrum Disorder

PubMed Central

Williams, Jaime M.; Beck, Tyler F.; Pearson, David M.; Proud, Monica B.; Cheung, Sau Wai; Scott, Daryl A.

2010-01-01

Individuals with autism spectrum disorders have impairments in social, communicative, and behavior development that are often accompanied by abnormalities in cognitive functioning, learning, attention, and sensory processing. In this report, we describe a 3-year-old male child with an autism spectrum disorder who carries a 2Mb deletion of chromosome 1q42. Array comparative genome hybridization revealed that this deletion involves at least three genes—DISC1, DISC2, and TSNAX—which have been found to be associated with neuropsychiatric disorders and are likely to play key roles in normal CNS development. Further studies revealed that the deletion was inherited from his unaffected mother. This suggests that other genetic and/or environmental factors, some of which may be sex specific, may modify the phenotypic effects of this deletion. While this case provides evidence for the potential role of DISC1, DISC2, and TSNAX in the development of autism spectrum disorders, it is equally clear that caution must be taken when providing families with prognostic information and genetic counseling regarding such deletions. PMID:19606485

Is mandibular asymmetry more frequent and severe with unilateral disc displacement?

PubMed

Xie, Qianyang; Yang, Chi; He, Dongmei; Cai, Xieyi; Ma, Zhigui

2015-01-01

To investigate the prevalence of mandibular asymmetry (MA) within the symptomatic unilateral anterior disc displacement (ADD) patients, and analyze the influence TMJ factors of the MA severity. Patients aged under 20 years old with symptomatic unilateral ADD and asymptomatic volunteers with normal disc-condyle relationship diagnosed by magnetic resonance imaging (MRI) were included in this study. Posteroanterior cephalometric radiographs were taken to measure MA. Condylar height, disc length and disc displacement were measured by MRI. The prevalence and severity of MA were compared between the ADD and the control groups. The correlation between the severity of MA with the amount of condylar height shortage, disc deformity and distance of disc displacement were also evaluated within the ADD group. There were 165 cases in the unilateral ADD group, and 156 cases in the control group. One hundred and nineteen cases had MA which accounted 72.12% (119/165) in the ADD group; while in the control group, only 25.64% (40/156) exhibited MA. The mean horizontal menton deviation and condylar height shortage in the unilateral ADD group were significantly larger than that in the control group (5.62 mm vs. 4.19 mm; 3.14 mm vs. 1.32 mm, p < 0.01). The severity of MA was significantly correlated with the amount of disc displacement, disc deformity and condylar height shortage (correlation coefficient: 0.80, 0.70, and 0.82). MA is much more common and severe in young unilateral ADD patients. The severity of MA is correlated with the height of condyle and the status of the disc. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Effect of Survivin gene therapy via lentivirus vector on the course of intervertebral disc degeneration in an in vivo rabbit model.

PubMed

Yue, Bin; Lin, Yazhou; Ma, Xuexiao; Zhang, Guoqing; Chen, Bohua

2016-11-01

The aim of the current study was to use gene therapy to attenuate or reverse the degenerative process within the intervertabral disc. The effect of survivin gene therapy via lentiviral vector transfection on the course of intervertebral disc degeneration was investigated in the current study in an in vivo rabbit model. A total of 15 skeletally mature female New Zealand White rabbits were randomly divided into three groups: Punctured blank control group (group A, n=5), punctured empty vector control group (group B, n=5) and the treatment group (group C, n=5). Computed tomography‑guided puncture was performed at the L3‑L4 and L4‑L5 discs, in accordance with a previously validated rabbit annulotomy model for intervertebral disc degeneration. After 3 weeks, a lentiviral vector (LV) carrying survivin was injected into the nucleus pulposus. The results demonstrated that through magnetic resonance imaging, histology, gene expression, protein content and apoptosis analyses, group A and B were observed to exhibit disc degeneration, which increased over time, and no significant difference was observed between the two groups (P>0.05). However, there was reduced disc degeneration in group C compared with the punctured control groups, and the difference was statistically significant (P<0.05). Overall, the results of the present study demonstrated that injection of the LV carrying survivin into punctured rabbit intervertebral discs acted to delay changes associated with the degeneration of the discs. Although data from animal models should be extrapolated to the human condition with caution, the present study suggests potential for the use of gene therapy to decelerate disc degeneration.

Microarray analysis of laser capture microdissected-anulus cells from the human intervertebral disc.

PubMed

Gruber, Helen E; Mougeot, Jean-Luc; Hoelscher, Gretchen; Ingram, Jane A; Hanley, Edward N

2007-05-15

Five Thompson Grade I/II discs (Group 1), 7 Grade III discs (Group 2), and 3 Grade IV discs (Group IV) were studied here in a project approved by the authors' Human Subjects Institutional Review Board. Our objective was to use laser capture microdissection (LCM) to harvest cells from the human anulus and to derive gene expression profiles using microarray analysis. Appropriate gene expression is essential in the intervertebral disc for maintenance of extracellular matrix (ECM), ECM remodeling, and maintenance of a viable disc cell population. During disc degeneration, cell numbers drop, making gene expression studies challenging. LCM was used to harvest cells from paraffin-embedded sections of human anulus tissue. Gene profiling used Affymetrix GeneChip Human X3P arrays. ANOVA and SAM permutation analysis were applied to dCHIP normalized, filtered, and log-transformed gene expression data ( approximately 33,500 probes), and data analyzed to identify genes that were significantly differentially expressed between the 3 groups. We identified 47 genes that were significantly differentially expressed between the 3 groups (P < 0.001 and lowest q values). Compared with the healthiest discs (Grade I/II), 13 genes were up-regulated and 19 down-regulated in both the Grade III and the Grade IV discs. Genes with biologic significance regulated during degeneration involved cell senescence, low cell division rates, hypoxia-related genes, heat-shock protein 70 interacting protein, neuropilin 2, and interleukin-23p19 (interleukin-12 family). Results expand our understanding of disc aging and degeneration and show that LCM is a valuable technique that can be used to collect mRNA amounts adequate for microarray analysis from the sparse cell population of the human anulus.

Effects of Axial Torsion on Disc Height Distribution: An In Vivo Study.

PubMed

Espinoza Orías, Alejandro A; Mammoser, Nicole M; Triano, John J; An, Howard S; Andersson, Gunnar B J; Inoue, Nozomu

2016-05-01

Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positions on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo. Eighty-one volunteers were computed tomography-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each "disc" set as the reference surface and separated into 5 anatomical zones: 4 peripheral and 1 central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions and were compared against each other with analysis of variance, with significance set at P < .05. Mean neutral disc height was 7.32 mm (1.59 mm). With 50° rotation, a small but significant increase to 7.44 mm (1.52 mm) (P < .0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (P < .0001), whereas the left, anterior, and central decreased. This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown. Copyright © 2016 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.

Estimating normative limits of Heidelberg Retina Tomograph optic disc rim area with quantile regression.

PubMed

Artes, Paul H; Crabb, David P

2010-01-01

To investigate why the specificity of the Moorfields Regression Analysis (MRA) of the Heidelberg Retina Tomograph (HRT) varies with disc size, and to derive accurate normative limits for neuroretinal rim area to address this problem. Two datasets from healthy subjects (Manchester, UK, n = 88; Halifax, Nova Scotia, Canada, n = 75) were used to investigate the physiological relationship between the optic disc and neuroretinal rim area. Normative limits for rim area were derived by quantile regression (QR) and compared with those of the MRA (derived by linear regression). Logistic regression analyses were performed to quantify the association between disc size and positive classifications with the MRA, as well as with the QR-derived normative limits. In both datasets, the specificity of the MRA depended on optic disc size. The odds of observing a borderline or outside-normal-limits classification increased by approximately 10% for each 0.1 mm(2) increase in disc area (P < 0.1). The lower specificity of the MRA with large optic discs could be explained by the failure of linear regression to model the extremes of the rim area distribution (observations far from the mean). In comparison, the normative limits predicted by QR were larger for smaller discs (less specific, more sensitive), and smaller for larger discs, such that false-positive rates became independent of optic disc size. Normative limits derived by quantile regression appear to remove the size-dependence of specificity with the MRA. Because quantile regression does not rely on the restrictive assumptions of standard linear regression, it may be a more appropriate method for establishing normative limits in other clinical applications where the underlying distributions are nonnormal or have nonconstant variance.

Interleukin 1-beta upregulates brain-derived neurotrophic factor, neurotrophin 3 and neuropilin 2 gene expression and NGF production in annulus cells.

PubMed

Gruber, H E; Hoelscher, G L; Bethea, S; Hanley, E N

2012-11-01

The relationship between disc cells, nerves and pain production in the intervertebral disc is poorly understood. Neurotrophins, signaling molecules involved in the survival, differentiation and migration of neurons, and neurite outgrowth, are expressed in non-neuronal tissues including the disc. We hypothesized that three-dimensional exposure of human disc cells to the proinflammatory cytokine IL-1ß in vitro would elevate neurotrophin gene expression levels and production of nerve growth factor (NGF). Cells isolated from Thompson grade III and IV discs were cultured for 14 days under control conditions or with addition of 10(2) pM IL-1ß; mRNA was isolated and conditioned media assayed for NGF content. IL-1ß exposure in three-dimensional culture significantly increased expression of neurotrophin 3, brain-derived neurotrophic factor, and neuropilin 2 compared to controls. IL-1ß-exposed cells showed significantly increased NGF production compared to controls. Findings support our hypothesis, expand previous data concerning expression of neurotrophins, and provide the first documented expression of neurotrophin 3 and neuropilin 2. Our results have direct translational relevance, because they address the primary clinical issue of low back pain and open the possibility of novel analgesic therapies using specific small-molecular antagonists to neurotrophins.

The imprint of satellite accretion on the chemical and dynamical properties of disc galaxies

NASA Astrophysics Data System (ADS)

Ruiz-Lara, T.; Few, C. G.; Gibson, B. K.; Pérez, I.; Florido, E.; Minchev, I.; Sánchez-Blázquez, P.

2016-02-01

Aims: We study the effects of the cosmological assembly history on the chemical and dynamical properties of the discs of spiral galaxies as a function of radius. Methods: We made use of the simulated Milky Way mass, fully-cosmological discs from Ramses Disc Environment Study (RaDES). We analysed their assembly history by examining the proximity of satellites to the galactic disc, instead of their merger trees, to better gauge which satellites impact the disc. We presented stellar age and metallicity profiles, age-metallicity relation (AMR), age-velocity dispersion relation (AVR), and stellar age distribution (SAD) in several radial bins for the simulated galaxies. Results: Assembly histories can be divided into three different stages: I) a merger dominated phase, when a large number of mergers with mass ratios of ~1:1 take place (lasting ~3.2 ± 0.4 Gyr on average); II) a quieter phase, when ~1:10 mergers take place (lasting ~4.4 ± 2.0 Gyr); and III) a secular phase where the few mergers that take place have mass ratios below 1:100, which do not affect the disc properties (lasting ~5.5 ± 2.0 Gyr). The first two phases are able to kinematically heat the disc and produce a disc that is chemically mixed over its entire radial extension. Phase 2 ends with a final merger event (at time tjump) marking the onset of important radial differences in the AMR, AVR, and SAD. Conclusions: Inverted AMR trends in the outer parts of discs, for stars younger than tjump, are found as the combined effect of radial motions and star formation in satellites temporarily located in these outer parts. U-shaped stellar age profiles change to an old plateau (~10 Gyr) in the outer discs for the entire RaDES sample. This shape is a consequence of inside-out growth of the disc, radial motions of disc stars (inwards and outwards), and the accretion of old stars from satellites. We see comparable age profiles even when ignoring the influence of stellar migration due to the presence of early in situ star formation in the outer regions of the galaxy.

Total prosthetic replacement of atrioventricular valves in the dog

PubMed Central

Den Otter, G.

1968-01-01

The free-floating cone and cage valve, described in a previous study as being successful as a substitute for the right atrioventricular valve, does not perform well when it is inserted in the mitral ostium. A tilting cone or disc was constructed and tested in a series of 15 dogs. This prosthesis gave excellent results in 12 animals. The reasons for its failure in the remaining three is discussed. The prosthesis presented has advantages over any ball and cage valve, mainly because of its smaller volume. Images PMID:5654076

Nonlinear dynamics of the human lumbar intervertebral disc.

PubMed

Marini, Giacomo; Huber, Gerd; Püschel, Klaus; Ferguson, Stephen J

2015-02-05

Systems with a quasi-static response similar to the axial response of the intervertebral disc (i.e. progressive stiffening) often present complex dynamics, characterized by peculiar nonlinearities in the frequency response. However, such characteristics have not been reported for the dynamic response of the disc. The accurate understanding of disc dynamics is essential to investigate the unclear correlation between whole body vibration and low back pain. The present study investigated the dynamic response of the disc, including its potential nonlinear response, over a range of loading conditions. Human lumbar discs were tested by applying a static preload to the top and a sinusoidal displacement at the bottom of the disc. The frequency of the stimuli was set to increase linearly from a low frequency to a high frequency limit and back down. In general, the response showed nonlinear and asymmetric characteristics. For each test, the disc had different response in the frequency-increasing compared to the frequency-decreasing sweep. In particular, the system presented abrupt changes of the oscillation amplitude at specific frequencies, which differed between the two sweeps. This behaviour indicates that the system oscillation has a different equilibrium condition depending on the path followed by the stimuli. Preload and amplitude of the oscillation directly influenced the disc response by changing the nonlinear dynamics and frequency of the jump-phenomenon. These results show that the characterization of the dynamic response of physiological systems should be readdressed to determine potential nonlinearities. Their direct effect on the system function should be further investigated. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of Axial Torsion on Disc Height Distribution: an In Vivo Study

PubMed Central

Espinoza Orías, Alejandro A.; Mammoser, Nicole M.; Triano, John J.; An, Howard S.; Andersson, Gunnar B.J.; Inoue, Nozomu

2016-01-01

Objectives Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positons on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo. Methods Eighty-one volunteers were CT-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each ‘disc’ set as the reference surface and separated into five anatomical zones: four peripheral and one central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions, and were compared against each other with ANOVA, with significance set at p < 0.05. Results Mean neutral disc height was 7.32 (1.59) mm. With 50° rotation, a small but significant increase to 7.44 (1.52) mm (p < 0.0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (p < 0.0001), while the left, anterior and central decreased. Conclusions This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown. PMID:27059249

Harvesting the decay energy of 26Al to drive lightning discharge in protoplanetary discs

NASA Astrophysics Data System (ADS)

Johansen, Anders; Okuzumi, Satoshi

2018-01-01

Chondrules in primitive meteorites likely formed by recrystallisation of dust aggregates that were flash-heated to nearly complete melting. Chondrules may represent the building blocks of rocky planetesimals and protoplanets in the inner regions of protoplanetary discs, but the source of ubiquitous thermal processing of their dust aggregate precursors remains elusive. Here we demonstrate that escape of positrons released in the decay of the short-lived radionuclide 26Al leads to a large-scale charging of dense pebble structures, resulting in neutralisation by lightning discharge and flash-heating of dust and pebbles. This charging mechanism is similar to a nuclear battery where a radioactive source charges a capacitor. We show that the nuclear battery effect operates in circumplanetesimal pebble discs. The extremely high pebble densities in such discs are consistent with conditions during chondrule heating inferred from the high abundance of sodium within chondrules. The sedimented mid-plane layer of the protoplanetary disc may also be prone to charging by the emission of positrons, if the mass density of small dust there is at least an order of magnitude above the gas density. Our results imply that the decay energy of 26Al can be harvested to drive intense lightning activity in protoplanetary discs. The total energy stored in positron emission is comparable to the energy needed to melt all solids in the protoplanetary disc. The efficiency of transferring the positron energy to the electric field nevertheless depends on the relatively unknown distribution and scale-dependence of pebble density gradients in circumplanetesimal pebble discs and in the protoplanetary disc mid-plane layer.

A minimally invasive in-fiber Bragg grating sensor for intervertebral disc pressure measurements

NASA Astrophysics Data System (ADS)

Dennison, Christopher R.; Wild, Peter M.; Wilson, David R.; Cripton, Peter A.

2008-08-01

We present an in-fiber Bragg grating (FBG) based intervertebral disc (IVD) pressure sensor that has pressure sensitivity seven times greater than that of a bare fiber, and a major diameter and sensing area of only 400 µm and 0.03 mm2, respectively. This is the only optical, the smallest and the most mechanically compliant disc pressure sensor reported in the literature. This is also an improvement over other FBG pressure sensors that achieve increased sensitivity through mechanical amplification schemes, usually resulting in major diameters and sensing lengths of many millimeters. Sensor sensitivity is predicted using numerical models, and the predicted sensitivity is verified through experimental calibrations. The sensor is validated by conducting IVD pressure measurements in porcine discs and comparing the FBG measurements to those obtained using the current standard sensor for IVD pressure. The predicted sensitivity of the FBG sensor matched with that measured experimentally. IVD pressure measurements showed excellent repeatability and agreement with those obtained from the standard sensor. Unlike the current larger sensors, the FBG sensor could be used in discs with small disc height (i.e. cervical or degenerated discs). Therefore, there is potential to conduct new measurements that could lead to new understanding of the biomechanics.

The relationship between loads and power of a rotor and an actuator disc

NASA Astrophysics Data System (ADS)

van Kuik, Gijs A. M.

2014-12-01

Most state of the art rotor design methods are based on the actuator disc theory developed about one century ago. The actuator disc is an axisymmetric permeable surface carrying a load that represents the load on a real rotor with a finite number of blades N. However, the mathematics of the transition from a real rotor load to an axisymmetrically loaded disc is not yet presented in literature. By formulating an actuator disc equation of motion in which the Bernoulli constant H is expressed in kinematical terms, a comparison of the power conversion and load on the disc and rotor is possible. For both the converted power is expressed as a change of angular momentum times rotational speed. The limits for N → ∞ while the chord c → 0, the rotational speed Ω → ∞, the load F becoming uniform by ∂F/∂r → 0 and the thickness epsilon → 0 confirm that the classical disc represents the rotor with an infinite number of blades. Furthermore, the expressions for the blade load are compared to the expressions in current design and analysis tools. The latter do not include the load on chord-wise vorticity. Including this is expected to give a better modelling of the tip and root flow.

Improved display of cervical intervertebral discs on water (iodine) images: incidental findings from single-source dual-energy CT angiography of head and neck arteries.

PubMed

Wu, Qingxia; Shi, Dapeng; Cheng, Tianming; Liu, Hongming; Hu, Niuniu; Chang, Xiaowan; Guo, Ying; Wang, Meiyun

2018-06-19

To (a) assess the diagnostic performance of material decomposition (MD) water (iodine) images for the evaluation of cervical intervertebral discs (IVDs) in patients who underwent dual-energy head and neck CT angiography (HNCTA) compared with 70-keV images and (b) to explore the correlation of water concentration with the T2 relaxation time of IVDs. Twenty-four consecutive patients who underwent dual-energy HNCTA and cervical spine MRI were studied. The diagnostic performance of water (iodine), 70-keV and MR images for IVD bulge and herniation was assessed. A subjective image score for each image set was recorded. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of IVDs to the cervical spinal cord were compared between water (iodine) and 70-keV images. Disc water concentration as measured on water (iodine) images was correlated with T2 relaxation time. IVD evaluations for bulge and herniation did not differ significantly among the three image sets (pairwise comparisons; all p > 0.05). SNR and CNR were significantly improved on water (iodine) images compared with those on 70-keV images (p < 0.001). Although water (iodine) images showed higher image quality scores when evaluating IVDs compared with 70-keV images, the difference is not significant (all adjusted p > 0.05). IVD water concentration exhibited no correlation with relative T2 relaxation time (all p > 0.05). Water (iodine) images facilitated analysis of cervical IVDs by providing higher SNR and CNR compared with 70-keV images. The disc water concentration measured on water (iodine) images exhibited no correlation with relative T2 relaxation time. • There was no significant difference in cervical IVD evaluations for bulge and herniation among water (iodine) images, 70-keV images and MR images. • Water (iodine) images provided higher objective and subjective image quality than 70-keV images, though the difference of subjective evaluation was not statistically significant. • The disc water concentration exhibited no correlation with relative T2 relaxation time, which reflects the inferiority of the water (iodine) images in evaluating disc water content compared with T2 maps.

ISSLS PRIZE IN CLINICAL SCIENCE 2017: Is infection the possible initiator of disc disease? An insight from proteomic analysis.

PubMed

Rajasekaran, S; Tangavel, Chitraa; Aiyer, Siddharth N; Nayagam, Sharon Miracle; Raveendran, M; Demonte, Naveen Luke; Subbaiah, Pramela; Kanna, Rishi; Shetty, Ajoy Prasad; Dharmalingam, K

2017-05-01

Proteomic and 16S rDNA analysis of disc tissues obtained in vivo. To address the controversy of infection as an aetiology for disc disorders through protein profiling. There is raging controversy over the presence of bacteria in human lumbar discs in vivo, and if they represent contamination or infection. Proteomics can provide valuable insight by identifying proteins signifying bacterial presence and, also host defence response proteins (HDRPs), which will confirm infection. 22 discs (15-disc herniations (DH), 5-degenerate (DD), 2-normal in MRI (NM) were harvested intraoperatively and immediately snap frozen. Samples were pooled into three groups and proteins extracted were analysed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Post identification, data analysis was performed using Uniprotdb, Pantherdb, Proteome discoverer and STRING network. Authentication for bacterial presence was performed by PCR amplification of 16S rDNA. LC-MS/MS analysis using Orbitrap showed 1103 proteins in DH group, compared to 394 in NM and 564 in DD. 73 bacterial specific proteins were identified (56 specific for Propionibacterium acnes; 17 for Staphylococcus epidermidis). In addition, 67 infection-specific HDRPs, unique or upregulated, such as Defensin, Lysozyme, Dermcidin, Cathepsin-G, Prolactin-Induced Protein, and Phospholipase-A2, were identified confirming presence of infection. Species-specific primers for P. acnes exhibited amplicons at 946 bp (16S rDNA) and 515 bp (Lipase) confirming presence of P. acnes in both NM discs, 11 of 15 DH discs, and all five DD discs. Bioinformatic search for protein-protein interactions (STRING) documented 169 proteins with close interactions (protein clustering co-efficient 0.7) between host response and degenerative proteins implying that infection may initiate degradation through Ubiquitin C. Our study demonstrates bacterial specific proteins and host defence proteins to infection which strengthen the hypothesis of infection as a possible initiator of disc disease. These results can lead to a paradigm shift in our understanding and management of disc disorders.

Structure-Function Correlation Using Confocal Laser Ophthalmoscope in Primary Open-Angle Glaucoma and Pseudoexfoliative Glaucoma.

PubMed

Pappas, Theofanis; Founti, Panayiota; Yin, Xiang Jun; Koskosas, Archimidis; Anastasopoulos, Eleftherios; Salonikiou, Angeliki; Kilintzis, Vasilios; Antoniadis, Antonios; Ziakas, Nikolaos; Topouzis, Fotis

2016-04-01

To compare Heidelberg Retina Tomograph (HRT) optic disc parameters and structure-function correlation between primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG). Prospective, observation case series. A total of 54 POAG and 33 PEXG cases, consecutively recruited from a University Glaucoma Service, underwent a comprehensive ophthalmic examination, including HRT optic disc imaging. Glaucoma definition required the presence of both structural and functional damage. One eye per subject was included in the analysis. T test, Mann-Whitney U test, and analysis of covariance were used to compare HRT parameters between POAG and PEXG, adjusting for age, mean deviation (MD) in the visual field, intraocular pressure, and disc area. The correlation between HRT and MD was assessed in each group. Cup area (P=0.048), height variation contour (P=0.016), and cup/disc area ratio (P=0.023) were higher in POAG, whereas the mean retinal nerve fiber layer thickness (P=0.048), retinal nerve fiber layer cross-section area (P=0.044), and rim area (P=0.048) were lower in POAG, compared with PEXG. The correlation of HRT parameters with MD was significant only in the POAG group. At a similar level of functional damage, POAG subjects presented with more pronounced structural damage than PEXG subjects. The correlation between HRT and visual field parameters was more evident in POAG, compared with PEXG.

Truncated disc surface brightness profiles produced by flares

NASA Astrophysics Data System (ADS)

Borlaff, Alejandro; Eliche-Moral, M. Carmen; Beckman, John; Font, Joan

2017-03-01

Previous studies have discarded that flares in galactic discs may explain the truncation that are frequently observed in highly-inclined galaxies (Kregel et al. 2002). However, no study has systematically analysed this hypothesis using realistic models for the disc, the flare and the bulge. We derive edge-on and face-on surface brightness profiles for a series of realistic galaxy models with flared discs that sample a wide range of structural and photometric parameters across the Hubble Sequence, accordingly to observations. The surface brightness profile for each galaxy model has been simulated for edge-on and face-on views to find out whether the flared disc produces a significant truncation in the disc in the edge-on view compared to the face-on view or not. In order to simulate realistic images of disc galaxies, we have considered the observational distribution of the photometric parameters as a function of the morphological type for three mass bins (10 < log10(M/M ⊙) < 10.7, 10.7 < log10(M/M ⊙) < 11 and log10(M/M ⊙) > 11), and four morphological type bins (S0-Sa, Sb-Sbc, Sc-Scd and Sd-Sdm). For each mass bin, we have restricted the photometric and structural parameters of each modelled galaxy to their characteristic observational ranges (μ0, disc, μeff, bulge, B/T, M abs, r eff, n bulge, h R, disc) and the flare in the disc (h z, disc/h R, disc, ∂h z, disc/∂R, see de Grijs & Peletier 1997, Graham 2001, López-Corredoira et al. 2002, Yoachim & Dalcanton 2006, Bizyaev et al. 2014, Mosenkov et al. 2015). Contrary to previous claims, the simulations show that realistic flared disks can be responsible for the truncations observed in many edge-on systems, preserving the profile of the non-flared analogous model in face-on view. These breaks reproduce the properties of the weak-to-intermediate breaks observed in many real Type-II galaxies in the diagram relating the radial location of the break (R brkII) in units of the inner disk scale-length with the break strength S (Laine et al. 2014). Radial variation of the scale-height of the disc (flaring) can explain the existence of many breaks in edge-on galaxies, especially of those with low break strengths 10\\frac{ho}{hi} \\sim \\ [-0.3,-0.1]$ .

Revolution evolution: tracing angular momentum during star and planetary system formation

NASA Astrophysics Data System (ADS)

Davies, Claire Louise

2015-04-01

Stars form via the gravitational collapse of molecular clouds during which time the protostellar object contracts by over seven orders of magnitude. If all the angular momentum present in the natal cloud was conserved during collapse, stars would approach rotational velocities rapid enough to tear themselves apart within just a few Myr. In contrast to this, observations of pre-main sequence rotation rates are relatively slow (∼ 1 - 15 days) indicating that significant quantities of angular momentum must be removed from the star. I use observations of fully convective pre-main sequence stars in two well-studied, nearby regions of star formation (namely the Orion Nebula Cluster and Taurus-Auriga) to determine the removal rate of stellar angular momentum. I find the accretion disc-hosting stars to be rotating at a slower rate and contain less specific angular momentum than the disc-less stars. I interpret this as indicating a period of accretion disc-regulated angular momentum evolution followed by near-constant rotational evolution following disc dispersal. Furthermore, assuming that the age spread inferred from the Hertzsprung-Russell diagram constructed for the star forming region is real, I find that the removal rate of angular momentum during the accretion-disc hosting phase to be more rapid than that expected from simple disc-locking theory whereby contraction occurs at a fixed rotation period. This indicates a more efficient process of angular momentum removal must operate, most likely in the form of an accretion-driven stellar wind or outflow emanating from the star-disc interaction. The initial circumstellar envelope that surrounds a protostellar object during the earliest stages of star formation is rotationally flattened into a disc as the star contracts. An effective viscosity, present within the disc, enables the disc to evolve: mass accretes inwards through the disc and onto the star while momentum migrates outwards, forcing the outer regions of the disc to expand. I used spatially resolved submillimetre detections of the dust and gas components of protoplanetary discs, gathered from the literature, to measure the radial extent of discs around low-mass pre-main sequence stars of ∼ 1-10 Myr and probe their viscous evolution. I find no clear observational evidence for the radial expansion of the dust component. However, I find tentative evidence for the expansion ofthe gas component. This suggests that the evolution of the gas and dust components of protoplanetary discs are likely governed by different astrophysical processes. Observations of jets and outflows emanating from protostars and pre-main sequence stars highlight that it may also be possible to remove angular momentum from the circumstellar material. Using the sample of spatially resolved protoplanetary discs, I find no evidence for angular momentum removal during disc evolution. I also use the spatially resolved debris discs from the Submillimetre Common-User Bolometer Array-2 Observations of Nearby Stars survey to constrain the amount of angular momentum retained within planetary systems. This sample is compared to the protoplanetary disc angular momenta and to the angular momentum contained within pre-stellar cores. I find that significant quantities of angular momentum must be removed during disc formation and disc dispersal. This likely occurs via magnetic braking during the formation of the disc, via the launching of a disc or photo-evaporative wind, and/or via ejection of planetary material following dynamical interactions.

[Topography and mechanical property of goat temporomandibular joint disc cells].

PubMed

Bao, Guangjie; Kong, Nannan; Guo, Manli; Su, Xuelian; Kang, Hong

2015-08-01

This study is performed to investigate the cell topographies and biomechanical properties of two different types of temporomandibular joint (TMJ) discs from goats by using JPK Nano Wizard 3 biological atomic force microscopy (AFM). This process provides a guideline for selecting seed cells for TMJ disc tissue engineering. TMJ disc cells from primary goats were cultured by monolayer culture method. AFM was used to contact scan the topographies of the two types of TMJ disc cells under physiological environment. Approximately 20 chondrocyte-like and fibroblast-like cells were selected randomly to plot the force-versus-distance curves of the cytoplasm and nucleus. Young's modulus and adhesion were analyzed by JPK Data Processing. The triangle-shapednucleus of the chondrocyte-like cell occupied a large portion of the cell. Cytoskeleton was arranged dendritically on the surface. Pseudopodia were extended from cell edges. The spindle-shaped nucleus of the fibroblast-like cell occupied a significantly larger region compared with the cytoplasmic region. Cytoskeleton was arranged regularly. Cell edges were smooth with less pseudopodia extended. No difference was found in the surface roughness between the two types of cells. According to the force-versus-distance curves, the Young's moduli of the two types of cells were not statistically different (P>0.05), but differences were found in the cytoplasmic regions (P=0.047). No statistical difference was found in the adhesions between the two types of cells (P>0.05). The AFM topography and curves were compared and analyzed. The two types of TMJ disc cells exhibited significantly different topographies, but only slight difference in their mechanical abilities.

Distinction between the extracellular matrix of the nucleus pulposus and hyaline cartilage: a requisite for tissue engineering of intervertebral disc.

PubMed

Mwale, F; Roughley, P; Antoniou, J

2004-12-15

Tissue engineering of intervertebral discs (IVD) using mesenchymal stem cells (MSCs) induced to differentiate into a disc-cell phenotype has been considered as an alternative treatment for disc degeneration. However, since there is no unique marker characteristic of discs and since hyaline cartilage and immature nucleus pulposus (NP) possess similar macromolecules in their extracellular matrix, it is currently difficult to recognize MSC conversion to a disc cell. This study was performed to compare the proteoglycan to collagen ratio (measured as GAG to hydroxyproline ratio) in the NP of normal disc to that of the hyaline cartilage of the endplate within the same group of individuals and test the hypothesis that this ratio can be used for in vivo studies to distinguish between a normal NP and hyaline cartilage phenotype. Whole human lumbar spine specimens from fresh cadavers, ranging in age from 12 weeks to 79 years, were used to harvest the IVDs and adjacent endplates. The GAG to hydroxyproline ratio within the NP of young adults is approximately 27:1, whereas the ratio within the hyaline cartilage endplate of the same aged individuals is about 2:1. The production of an extracellular matrix with a high proteoglycan to collagen ratio can be used in vivo to distinguish NP cells from chondrocytes, and could help in identifying a NP-like phenotype in vivo as opposed to a chondrocyte when MSCs are induced to differentiate for tissue engineering of a disc.

MRI Quantification of Human Spine Cartilage Endplate Geometry: Comparison With Age, Degeneration, Level, and Disc Geometry

PubMed Central

DeLucca, John F.; Peloquin, John M.; Smith, Lachlan J.; Wright, Alexander C.; Vresilovic, Edward J.; Elliott, Dawn M.

2017-01-01

Geometry is an important indicator of disc mechanical function and degeneration. While the geometry and associated degenerative changes in the nucleus pulposus and the annulus fibrosus are well-defined, the geometry of the cartilage endplate (CEP) and its relationship to disc degeneration are unknown. The objectives of this study were to quantify CEP geometry in three dimensions using an MRI FLASH imaging sequence and evaluate relationships between CEP geometry and age, degeneration, spinal level, and overall disc geometry. To do so, we assessed the MRI-based measurements for accuracy and repeatability. Next, we measured CEP geometry across a larger sample set and correlated CEP geometric parameters to age, disc degeneration, level, and disc geometry. The MRI-based measures resulted in thicknesses (0.3–1 mm) that are comparable to prior measurements of CEP thickness. CEP thickness was greatest at the anterior/posterior (A/P) margins and smallest in the center. The CEP A/P thickness, axial area, and lateral width decreased with age but were not related to disc degeneration. Age-related, but not degeneration-related, changes in geometry suggest that the CEP may not follow the progression of disc degeneration. Ultimately, if the CEP undergoes significant geometric changes with aging and if these can be related to low back pain, a clinically feasible translation of the FLASH MRI-based measurement of CEP geometry presented in this study may prove a useful diagnostic tool. PMID:27232974

A Substance Exchanger-Based Bioreactor Culture of Pig Discs for Studying the Immature Nucleus Pulposus.

PubMed

Li, Pei; Gan, Yibo; Wang, Haoming; Xu, Yuan; Song, Lei; Wang, Liyuan; Ouyang, Bin; Zhou, Qiang

2017-11-01

Various research models have been developed to study the biology of disc cells. Recently, the adult disc nucleus pulposus (NP) has been well studied. However, the immature NP is underinvestigated due to a lack of a suitable model. This study aimed to establish an organ culture of immature porcine disc by optimizing culture conditions and using a self-developed substance exchanger-based bioreactor. Immature porcine discs were first cultured in the bioreactor for 7 days at various levels of glucose (low, medium, high), osmolarity (hypo-, iso-, hyper-) and serum (5, 10, 20%) to determine the respective optimal level. The porcine discs were then cultured under the optimized conditions in the novel bioreactor, and were compared with fresh discs at day 14. For high-glucose, iso-osmolarity, or 10% serum, cell viability, the gene expression profile (for anabolic genes and catabolic genes), and glycosaminoglycan (GAG) and hydroxyproline (HYP) contents were more favorable than for other levels of glucose, osmolarity, and serum. When the immature discs were cultured under the optimized conditions using the novel bioreactor for 14 days, the viability of the immature NP was maintained based on histology, cell viability, GAG and HYP contents, and matrix molecule expression. In conclusion, the viability of the immature NP in organ culture could be maintained under the optimized culture conditions (high-glucose, iso-osmolarity, and 10% serum) in the substance exchanger-based bioreactor. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Efficiency of thin magnetically arrested discs around black holes

NASA Astrophysics Data System (ADS)

Avara, Mark J.; McKinney, Jonathan C.; Reynolds, Christopher S.

2016-10-01

The radiative and jet efficiencies of thin magnetized accretion discs around black holes (BHs) are affected by BH spin and the presence of a magnetic field that, when strong, could lead to large deviations from Novikov-Thorne (NT) thin disc theory. To seek the maximum deviations, we perform general relativistic magnetohydrodynamic simulations of radiatively efficient thin (half-height H to radius R of H/R ≈ 0.10) discs around moderately rotating BHs with a/M = 0.5. First, our simulations, each evolved for more than 70 000 rg/c (gravitational radius rg and speed of light c), show that large-scale magnetic field readily accretes inward even through our thin disc and builds-up to the magnetically arrested disc (MAD) state. Secondly, our simulations of thin MADs show the disc achieves a radiative efficiency of ηr ≈ 15 per cent (after estimating photon capture), which is about twice the NT value of ηr ˜ 8 per cent for a/M = 0.5 and gives the same luminosity as an NT disc with a/M ≈ 0.9. Compared to prior simulations with ≲10 per cent deviations, our result of an ≈80 per cent deviation sets a new benchmark. Building on prior work, we are now able to complete an important scaling law which suggests that observed jet quenching in the high-soft state in BH X-ray binaries is consistent with an ever-present MAD state with a weak yet sustained jet.

ITERATIVE SCATTER CORRECTION FOR GRID-LESS BEDSIDE CHEST RADIOGRAPHY: PERFORMANCE FOR A CHEST PHANTOM.

PubMed

Mentrup, Detlef; Jockel, Sascha; Menser, Bernd; Neitzel, Ulrich

2016-06-01

The aim of this work was to experimentally compare the contrast improvement factors (CIFs) of a newly developed software-based scatter correction to the CIFs achieved by an antiscatter grid. To this end, three aluminium discs were placed in the lung, the retrocardial and the abdominal areas of a thorax phantom, and digital radiographs of the phantom were acquired both with and without a stationary grid. The contrast generated by the discs was measured in both images, and the CIFs achieved by grid usage were determined for each disc. Additionally, the non-grid images were processed with a scatter correction software. The contrasts generated by the discs were determined in the scatter-corrected images, and the corresponding CIFs were calculated. The CIFs obtained with the grid and with the software were in good agreement. In conclusion, the experiment demonstrates quantitatively that software-based scatter correction allows restoring the image contrast of a non-grid image in a manner comparable with an antiscatter grid. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Reference Standard Test and the Diagnostic Ability of Spectral Domain Optical Coherence Tomography in Glaucoma.

PubMed

Rao, Harsha L; Yadav, Ravi K; Addepalli, Uday K; Begum, Viquar U; Senthil, Sirisha; Choudhari, Nikhil S; Garudadri, Chandra S

2015-08-01

To evaluate the relationship between the reference standard used to diagnose glaucoma and the diagnostic ability of spectral domain optical coherence tomograph (SDOCT). In a cross-sectional study, 280 eyes of 175 consecutive subjects, referred to a tertiary eye care center for glaucoma evaluation, underwent optic disc photography, visual field (VF) examination, and SDOCT examination. The cohort was divided into glaucoma and control groups based on 3 reference standards for glaucoma diagnosis: first based on the optic disc classification (179 glaucoma and 101 control eyes), second on VF classification (glaucoma hemifield test outside normal limits and pattern SD with P-value of <5%, 130 glaucoma and 150 control eyes), and third on the presence of both glaucomatous optic disc and glaucomatous VF (125 glaucoma and 155 control eyes). Relationship between the reference standards and the diagnostic parameters of SDOCT were evaluated using areas under the receiver operating characteristic curve, sensitivity, and specificity. Areas under the receiver operating characteristic curve and sensitivities of most of the SDOCT parameters obtained with the 3 reference standards (ranging from 0.74 to 0.88 and 72% to 88%, respectively) were comparable (P>0.05). However, specificities of SDOCT parameters were significantly greater (P<0.05) with optic disc classification as reference standard (74% to 88%) compared with VF classification as reference standard (57% to 74%). Diagnostic parameters of SDOCT that was significantly affected by reference standard was the specificity, which was greater with optic disc classification as the reference standard. This has to be considered when comparing the diagnostic ability of SDOCT across studies.

On the timing behaviour of PSR B1259-63 under the propeller torque from a transient accretion disc

NASA Astrophysics Data System (ADS)

Yi, Shu-Xu; Cheng, K. S.

2018-05-01

The γ-ray pulsar binary system PSR B1259-63 flares in GeV after each periastron. The origin of these flares is still under debate. Recently, in 2017, we proposed a mechanism that might explain the GeV flares. In that model, a transient accretion disc is expected to be formed from the matter that was gravity-captured by the neutron star from the main-sequence companion's circumstellar disc. The transient accretion disc exerts a spin-down torque on the neutron star (i.e. the propeller effect), which might be traceable via pulsar timing observations of PSR B1259-63. In this paper, we consider the propeller effect phenomenologically using a parameter χ, which describes the coupling between the disc matter and the neutron star. Comparing the expected timing residuals with recent observations by Shannon et al., we conclude that the angular momentum transfer is very weak (with the coupling parameter χ ≤ 10-4).

Deletion Analysis of the Tumorous-Head (tuh–3) Gene in DROSOPHILA MELANOGASTER

PubMed Central

Kuhn, David T.; Woods, Daniel F.; Andrew, Deborah J.

1981-01-01

In the presence of the naturally occurring maternal-effect alleles tuh-1h or tuh-1g, the tuh-3 mutant gene can cause the tumorous-head trait or the sac-testis trait. The tuh-3 gene functions as a semidominant in the presence of the tuh-1h maternal effect. Eye-antennal structures are replaced by posterior abdominal tergites and genital structures. If tuh-1h is replaced by its naturally occurring allele tuh-1g, tuh-3 functions as a recessive hypomorph and the defect switches from anterior to posterior structures, with a male genital-disc defect appearing with variable penetrance. Function and regulation of tuh-3+ may better be understood in light of the cytological localization of tuh-3 either adjacent to or as part of the bithorax complex. The tuh-3+ gene product appears to be essential for normal development, at least in the posterior end of the embryo. PMID:6804305

Association between menopause and lumbar disc degeneration: an MRI study of 1,566 women and 1,382 men.

PubMed

Lou, Chao; Chen, Hongliang; Mei, Liangwei; Yu, Weiyang; Zhu, Kejun; Liu, Feijun; Chen, Zhenzhong; Xiang, Guangheng; Chen, Minjiang; Weng, Qiaoyou; He, Dengwei

2017-10-01

The aim of this study was to revisit and further investigate the association between menopause and disc degeneration in the lumbar spine using a magnetic resonance imaging-based eight-level grading system. This study cohort comprised of 1,566 women and 1,382 age-matched men who were admitted for low back pain from June 2013 to October 2016. Data on age, weight, height, body mass index, age at natural menopause, and years since menopause (YSM) were obtained. Lumbar disc degeneration was assessed using a magnetic resonance imaging-based eight-level grading system. After adjustment for the confounding factors of age, height, and weight, young age-matched men were more susceptible to disc degeneration than premenopausal women (P < 0.05). However, after menopause, postmenopausal women had a significant tendency to develop more severe disc degeneration than their age-matched men (P < 0.05), and also compared with premenopausal and perimenopausal women (P < 0.01). Postmenopausal women were divided into nine subgroups by every 5 YSM. When YSM was less than 15 years, a positive trend was observed between YSM and severity of disc degeneration, respectively, at L1/L2 (r = 0.241), L2/L3 (r = 0.193), L3/L4 (r = 0.191), L4/L5 (r = 0.165), L5/S1 (r = 0.153), and all lumbar discs (r = 0.237) (P < 0.05 or 0.01). The analysis of covariance indicated a significant difference in each disc level (P < 0.05 or 0.01) between every two groups. When YSM was more than 15 years, the significant difference, however, disappeared in each disc level (P > 0.05). Menopause is associated with lumbar disc degeneration. The association occurred in the first 15 YSM, suggesting estrogen deficiency might be a risk factor of disc degeneration of the lumbar spine. Further studies need to be carried out for deciding whether age or menopause plays a more important role in the progression of disc degeneration in the lumbar spine.

Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc

NASA Astrophysics Data System (ADS)

Watts, Adam B.; Meurer, Gerhardt R.; Lagos, Claudia D. P.; Bruzzese, Sarah M.; Kroupa, Pavel; Jerabkova, Tereza

2018-07-01

We present optical photometry of Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)/Wide Field Camera (WFC) data of the resolved stellar populations in the outer disc of the dwarf irregular galaxy DDO 154. The photometry reveals that young main sequence (MS) stars are almost absent from the outermost H I disc. Instead, most are clustered near the main stellar component of the galaxy. We constrain the stellar initial mass function (IMF) by comparing the luminosity function of the MS stars to simulated stellar populations, assuming a constant star formation rate over the dynamical time-scale. The best-fitting IMF is deficient in high-mass stars compared to a canonical Kroupa IMF, with a best-fitting slope α = -2.45 and upper mass limit MU = 16 M⊙. This top-light IMF is consistent with predictions of the integrated galactic IMF theory. Combining the HST images with H I data from The H I Nearby Galaxy Survey (THINGS), we determine the star formation law (SFL) in the outer disc. The fit has a power-law exponent N = 2.92 ± 0.22 and zero-point A = 4.47 ± 0.65 × 10-7 M⊙ yr-1 kpc-2. This is depressed compared to the Kennicutt-Schmidt SFL, but consistent with weak star formation observed in diffuse H I environments. Extrapolating the SFL over the outer disc implies that there could be significant star formation occurring that is not detectable in H α. Last, we determine the Toomre stability parameter Q of the outer disc of DDO 154 using the THINGS H I rotation curve and velocity dispersion map. 72 per cent of the H I in our field has Q ≤ 4 and this incorporates 96 per cent of the observed MS stars. Hence, 28 per cent of the H I in the field is largely dormant.

Magnetic Resonance Imaging Interpretation in Patients With Symptomatic Lumbar Spine Disc Herniations

PubMed Central

Lurie, Jon D.; Doman, David M.; Spratt, Kevin F.; Tosteson, Anna N. A.; Weinstein, James N.

2009-01-01

Study Design Retrospective review of imaging data from a clinical trial. Objective To compare the interpretation of lumbar spine magnetic resonance imaging (MRIs) by clinical spine specialists and radiologists in patients with lumbar disc herniation. Summary of Background Data MRI is the imaging modality of choice for evaluation of the lumbar spine in patients with suspected lumbar disc herniation. Guidelines provide standardization of terms to more consistently describe disc herniation. The extent to which these guidelines are being followed in clinical practice is unknown. Methods We abstracted data from radiology reports from patients with lumbar intervertebral disc herniation enrolled in the Spine Patient Outcomes Research Trial. We evaluated the frequency with which morphology (e.g., protrusions, extrusions, or sequestrations) was reported as per guidelines and when present we compared the morphology ratings to those of clinicians who completed a structured data form as part of the trial. We assessed agreement using percent agreement and the κ statistic. Results There were 396 patients with sufficient data to analyze. Excellent agreement was observed between clinician and radiologist on the presence and level of herniation (93.4%), with 3.3% showing disagreement regarding level, of which a third could be explained by the presence of a transitional vertebra. In 3.3% of the cases in which the clinician reported a herniation (protrusion, extrusion, or sequestration), the radiologist reported no herniation on the MRI. The radiology reports did not clearly describe morphology in 42.2% of cases. In the 214 cases with clear morphologic descriptions, agreement was fair (κ = 0.24) and the disagreement was asymmetric (Bowker’s test of symmetry P < 0.0001) with clinicians more often rating more abnormal morphologic categories. Agreement on axial location of the herniation was excellent (κ = 0.81). There was disagreement between left or right side in only 3.3% of cases (κ = 0.93). Conclusion Radiology reports frequently fail to provide sufficient detail to describe disc herniation morphology. Agreement between MRI readings by clinical spine specialists and radiologists was excellent when comparing herniation vertebral level and location within level, but only fair comparing herniation morphology. PMID:19333103

Reoperation After Cervical Disc Arthroplasty Versus Anterior Cervical Discectomy and Fusion: A Meta-analysis.

PubMed

Zhong, Zhao-Ming; Zhu, Shi-Yuan; Zhuang, Jing-Shen; Wu, Qian; Chen, Jian-Ting

2016-05-01

Anterior cervical discectomy and fusion is a standard surgical treatment for cervical radiculopathy and myelopathy, but reoperations sometimes are performed to treat complications of fusion such as pseudarthrosis and adjacent-segment degeneration. A cervical disc arthroplasty is designed to preserve motion and avoid the shortcomings of fusion. Available evidence suggests that a cervical disc arthroplasty can provide pain relief and functional improvements similar or superior to an anterior cervical discectomy and fusion. However, there is controversy regarding whether a cervical disc arthroplasty can reduce the frequency of reoperations. We performed a meta-analysis of randomized controlled trials (RCTs) to compare cervical disc arthroplasty with anterior cervical discectomy and fusion regarding (1) the overall frequency of reoperation at the index and adjacent levels; (2) the frequency of reoperation at the index level; and (3) the frequency of reoperation at the adjacent levels. PubMed, EMBASE, and the Cochrane Register of Controlled Trials databases were searched to identify RCTs comparing cervical disc arthroplasty with anterior cervical discectomy and fusion and reporting the frequency of reoperation. We also manually searched the reference lists of articles and reviews for possible relevant studies. Twelve RCTs with a total of 3234 randomized patients were included. Eight types of disc prostheses were used in the included studies. In the anterior cervical discectomy and fusion group, autograft was used in one study and allograft in 11 studies. Nine of 12 studies were industry sponsored. Pooled risk ratio (RR) and associated 95% CI were calculated for the frequency of reoperation using random-effects or fixed-effects models depending on the heterogeneity of the included studies. A funnel plot suggested the possible presence of publication bias in the available pool of studies; that is, the shape of the plot suggests that smaller negative or no-difference studies may have been performed but have not been published, and so were not identified and included in this meta-analysis. The overall frequency of reoperation at the index and adjacent levels was lower in the cervical disc arthroplasty group (6%; 108/1762) than in the anterior cervical discectomy and fusion group (12%; 171/1472) (RR, 0.54; 95% CI, 0.36-0.80; p = 0.002). Subgroup analyses were performed according to secondary surgical level. Compared with anterior cervical discectomy and fusion, cervical disc arthroplasty was associated with fewer reoperations at the index level (RR, 0.50; 95% CI, 0.37-0.68; p < 0.001) and adjacent levels (RR, 0.52; 95% CI, 0.37-0.74; p < 0.001). Cervical disc arthroplasty is associated with fewer reoperations than anterior cervical discectomy and fusion, indicating that it is a safe and effective alternative to fusion for cervical radiculopathy and myelopathy. However, because of some limitations, these findings should be interpreted with caution. Additional studies are needed. Level I, therapeutic study.

Increased density of DISC1-immunoreactive oligodendroglial cells in fronto-parietal white matter of patients with paranoid schizophrenia.

PubMed

Bernstein, Hans-Gert; Jauch, Esther; Dobrowolny, Henrik; Mawrin, Christian; Steiner, Johann; Bogerts, Bernhard

2016-09-01

Profound white matter abnormalities have repeatedly been described in schizophrenia, which involve the altered expression of numerous oligodendrocyte-associated genes. Transcripts of the disrupted-in-schizophrenia 1 (DISC1) gene, a key susceptibility factor in schizophrenia, have recently been shown to be expressed by oligodendroglial cells and to negatively regulate oligodendrocyte differentiation and maturation. To learn more about the putative role(s) of oligodendroglia-associated DISC1 in schizophrenia, we analyzed the density of DISC1-immunoreactive oligodendrocytes in the fronto-parietal white matter in postmortem brains of patients with schizophrenia. Compared with controls (N = 12) and cases with undifferentiated/residual schizophrenia (N = 6), there was a significantly increased density of DISC1-expressing glial cells in paranoid schizophrenia (N = 12), which unlikely resulted from neuroleptic treatment. Pathophysiologically, over-expression of DISC1 protein(s) in white matter oligodendrocytes might add to the reduced levels of two myelin markers, 2',3'-cyclic-nucleotide 3'-phosphodiesterase and myelin basic protein in schizophrenia. Moreover, it might significantly contribute to cell cycle abnormalities as well as to deficits in oligodendroglial cell differentiation and maturation found in schizophrenia.

Radio emission from Sgr A*: pulsar transits through the accretion disc

NASA Astrophysics Data System (ADS)

Christie, I. M.; Petropoulou, M.; Mimica, P.; Giannios, D.

2017-06-01

Radiatively inefficient accretion flow models have been shown to accurately account for the spectrum and luminosity observed from Sgr A* in the X-ray regime down to mm wavelengths. However, observations at a few GHz cannot be explained by thermal electrons alone but require the presence of an additional non-thermal particle population. Here, we propose a model for the origin of such a population in the accretion flow via means of a pulsar orbiting the supermassive black hole in our Galaxy. Interactions between the relativistic pulsar wind with the disc lead to the formation of a bow shock in the wind. During the pulsar's transit through the accretion disc, relativistic pairs, accelerated at the shock front, are injected into the disc. The radio-emitting particles are long lived and remain within the disc long after the pulsar's transit. Periodic pulsar transits through the disc result in regular injection episodes of non-thermal particles. We show that for a pulsar with spin-down luminosity Lsd ˜ 3 × 1035 erg s-1 and a wind Lorentz factor of γw ˜ 104 a quasi-steady synchrotron emission is established with luminosities in the 1-10 GHz range comparable to the observed one.

Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars

NASA Astrophysics Data System (ADS)

Brown, R. O.; Ho, W. C. G.; Coe, M. J.; Okazaki, A. T.

2018-04-01

There are over 100 Be stars that are known to have neutron star companions but only one such system with a black hole. Previous theoretical work suggests this is not due to their formation but due to differences in X-ray luminosity. It has also been proposed that the truncation of the Be star's circumstellar disc is dependent on the mass of the compact object. Hence, Be star discs in black hole binaries are smaller. Since accretion onto the compact object from the Be star's disc is what powers the X-ray luminosity, a smaller disc in black hole systems leads to a lower luminosity. In this paper, simulations are performed with a range of eccentricities and compact object mass. The disc's size and density are shown to be dependent on both quantities. Mass capture and, in turn, X-ray luminosity are heavily dependent on the size and density of the disc. Be/black hole binaries are expected to be up to ˜10 times fainter than Be/neutron star binaries when both systems have the same eccentricity and can be 100 times fainter when comparing systems with different eccentricity.

The influence of microlensing on spectral line shapes generated by a relativistic accretion disc

NASA Astrophysics Data System (ADS)

Popović, L. Č; Mediavilla, E. G.; Muñoz, J. A.

2001-10-01

We study the influence of gravitational microlensing on the spectral line profiles originating from a relativistic accretion disc. Using the Chen & Halpern model for the disc, we show the noticeable changes that microlensing can induce in the line shape when the Einstein radius associated with the microlens is of a size comparable to that of the accretion disc. Of special interest is the relative enhancement between the blue and red peaks of the line when an off-center microlens affects the approaching and receding parts of the accretion disc asymmetrically. In an AGN formed by a super-massive binary in which the accretion disc is located around one of the super-massive companions (the primary), we discuss the possibility of microlensing by the secondary. In this case the ratio between the blue and red peaks of the line profile would depend on the orbital phase. We have also considered the more standard configuration of microlensing by a star-sized object in an intervening galaxy and find that microlensing may also be detected in the broad emission lines of multiply imaged QSOs. The changes observed in the line profile of Arp 102 B are taken as a reference for exploring both scenarios.

Fabrication and Demonstration of Mercury Disc-Well Probes for Stripping-Based Cyclic Voltammetry Scanning Electrochemical Microscopy.

PubMed

Barton, Zachary J; Rodríguez-López, Joaquín

2017-03-07

Scanning electrochemical microscopy (SECM) is a rising technique for the study of energy storage materials. Hg-based probes allow the extension of SECM investigations to ionic processes, but the risk of irreversible Hg amalgam saturation limits their operation to rapid timescales and dilute analyte solutions. Here, we report a novel fabrication protocol for Hg disc-well ultramicroelectrodes (UMEs), which retain access to stripping information but are less susceptible to amalgam saturation than traditional Hg sphere-caps or thin-films. The amalgamation and stripping behaviors of Hg disc-well UMEs are compared to those of traditional Hg sphere-cap UMEs and corroborated with data from finite element simulations. The improved protection against amalgam saturation allows Hg disc-wells to operate safely in highly concentrated environments at long timescales. The utility of the probes for bulk measurements extends also to SECM studies, where the disc geometry facilitates small tip-substrate gaps and improves both spatial and temporal resolution. Because they can carry out slow, high-resolution anodic stripping voltammetry approaches and imaging in concentrated solutions, Hg disc-well electrodes fill a new analytical niche for studies of ionic reactivity and are a valuable addition to the electrochemical toolbox.

Conservative and esthetic cast gold fixed partial dentures-inlay, onlay, and partial veneer retainers, custom composite pontics, and stress-breakers: part I: fundamental design principles.

PubMed

Stevenson, Richard G; Refela, Jane A

2009-01-01

Although in today's dental world implant restorations are considered the standard of care in the replacement of missing teeth, clinical contraindications and patient nonacceptance of implant placement can be encountered. Several scenarios are discussed here in which a single missing tooth can be restored with conservative fixed partial dentures (FPD) that employ cast gold retainers; each with a customized design in order to preserve tooth structure, maintain esthetics, and provide a long-term prognosis. The abutment teeth are prepared for conservative partial coverage restorations by using Brasseler burs (Brasseler USA, Savannah, GA, USA). Impressions are taken of the preparations, along with any retentive features, utilizing either the Vented Pin Channel technique or the Shooshan Plastic Pin technique. The latter technique utilizes Kodex twist drills and corresponding impression pins (Coltene Whaledent Inc., Mahwah, NJ, USA). The conservative FPD with non-rigid connectors is fabricated by using type III gold alloy. The pontic cage portion is chemically prepared utilizing the Panavia F2.0 cement kit (Kuraray America Inc., Houston, TX, USA) or other dual-polymerizing resin cement and restored with any type of direct composite resin material. A palette of opaquers and tints are used for chairside characterization of the esthetic pontic facing. The final polish of the pontic is completed by using FlexiDisc and FlexiBuff discs (Cosmedent Inc., Chicago, IL, USA). CLINICAL SIGNIFICANCE In cases where an implant restoration is contraindicated for replacement of a single tooth, a semi-precision FPD is a conservative, functional, and esthetic alternative.

The Influence of Artificial Cervical Disc Prosthesis Height on the Cervical Biomechanics: A Finite Element Study.

PubMed

Yuan, Wei; Zhang, Haiping; Zhou, Xiaoshu; Wu, Weidong; Zhu, Yue

2018-05-01

Artificial cervical disc replacement is expected to maintain normal cervical biomechanics. At present, the effect of the Prestige LP prosthesis height on cervical biomechanics has not been thoroughly studied. This finite element study of the cervical biomechanics aims to predict how the parameters, like range of motion (ROM), adjacent intradiscal pressure, facet joint force, and bone-implant interface stress, are affected by different heights of Prestige LP prostheses. The finite element model of intact cervical spine (C3-C7) was obtained from our previous study, and the model was altered to implant Prestige LP prostheses at the C5-C6 level. The effects of the height of 5, 6, and 7 mm prosthesis replacement on ROM, adjacent intradiscal pressure, facet joint force, as well as the distribution of bone-implant interface stress were examined. ROM, adjacent intradiscal pressure, and facet joint force increased with the prosthesis height, whereas ROM and facet joint force decreased at C5-C6. The maximal stress on the inferior surface of the prostheses was greater than that on the superior surface, and the stresses increased with the prosthesis height. The biomechanical changes were slightly affected by the height of 5 and 6 mm prostheses, but were strongly affected by the 7-mm prosthesis. An appropriate height of the Prestige LP prosthesis can preserve normal ROM, adjacent intradiscal pressure, and facet joint force. Prostheses with a height of ≥2 mm than normal can lead to marked changes in the cervical biomechanics and bone-implant interface stress. Copyright © 2018 Elsevier Inc. All rights reserved.

Clinical outcomes, radiologic kinematics, and effects on sagittal balance of the 6 df LP-ESP lumbar disc prosthesis.

PubMed

Lazennec, Jean-Yves; Even, Julien; Skalli, Wafa; Rakover, Jean-Patrick; Brusson, Adrien; Rousseau, Marc-Antoine

2014-09-01

Surgical treatment of degenerative disc disease remains a controversial subject. Lumbar fusion has been associated with a potential risk of segmental junctional disease and sagittal balance misalignment. Motion preservation devices have been developed as an alternative to fusion. The LP-ESP disc is a one-piece deformable device achieving 6 df, including shock absorption and elastic return. This is the first clinical report on its use. To assess clinical outcomes and radiologic kinematics in the first 2 years after implantation. Prospective cohort of patients with LP-ESP total disc replacement (TDR) at the lumbar spine. Forty-six consecutive patients. Clinical outcomes were the visual analog scale (VAS) for pain, the Oswestry disability index (ODI), and the GHQ28 (General Health Questionnaire) psychological score. Radiologic data were the range of motion (ROM), sagittal balance parameters, and mean center of rotation (MCR). Patients had single-level TDR at L4-L5 or L5-S1. Outcomes were prospectively recorded for 2 years (before and at 3, 6, 12, and 24 months after surgery). The SpineView software was used for computed analysis of the radiographic data. Paired t tests were used for statistical comparisons. No intraoperative complication occurred. All clinical scores improved significantly at 24 months: the back pain VAS scores by a mean of 4.1 points and the ODI by 33 points. The average ROM of the instrumented level was 5.4°±4.8° at 2 years and more than 2° for 76% of prostheses. The MCR was in a physiological area in 73% of cases. The sagittal balance (pelvic tilt, sacral slope, and segmental lordosis) did not change significantly at any point of the follow-up. Results from the 2-year follow-up indicate that LP-ESP prosthesis recreates lumbar spine function similar to that of the healthy disc in terms of ROM, quality of movement, effect on sagittal balance, and absence of modification in the kinematics of the upper adjacent level. Copyright © 2014 Elsevier Inc. All rights reserved.

The Effect of Single-Level Disc Degeneration on Dynamic Response of the Whole Lumbar Spine to Vertical Vibration.

PubMed

Guo, Li-Xin; Fan, Wei

2017-09-01

The objective of this study was to investigate the effect of single-level disc degeneration on dynamic response of the whole lumbar spine to vertical whole body vibration that is typically present when driving vehicles. Ligamentous finite element models of the lumbar L1-S1 motion segment in different grades of degeneration (healthy, mild, and moderate) at the L4-L5 level were developed with consideration of changing disc height and material properties of the nucleus pulpous. All models were loaded with a compressive follower preload of 400 N and a sinusoidal vertical vibration load of ±40 N. After transient dynamic analyses, computational results for the 3 models in terms of disc bulge, von-Mises stress in annulus ground substance, and nucleus pressure were plotted as a function of time and compared. All the predicted results showed a cyclic response with time. At the degenerated L4-L5 disc level, as degeneration progressed, maximum value of the predicted response showed a decrease in disc bulge and von-Mises stress in annulus ground substance but a slight increase in nucleus pressure, and their vibration amplitudes were all decreased. At the adjacent levels of the degenerated disc, there was a slight decrease in maximum value and vibration amplitude of these predicted responses with the degeneration. The results indicated that single-level disc degeneration can alter vibration characteristics of the whole lumbar spine especially for the degenerated disc level, and increasing the degeneration did not deteriorate the effect of vertical vibration on the spine. Copyright © 2017 Elsevier Inc. All rights reserved.

Cobb Angle Progression in Adolescent Scoliosis Begins at the Intervertebral Disc

PubMed Central

Will, Ryan E; Stokes, Ian A; Qiu, Xing; Walker, Matthew R.; Sanders, James O

2009-01-01

Study Design Longitudinal radiographic study of patients with progressive idiopathic scoliosis. Objective To determine the relative contributions of vertebral and disc wedging to the increase in Cobb angle during 3 phases of adolescent skeletal growth and maturation. Summary of Background Data Both disc wedging and vertebral body wedging are found in progressive scoliosis, but their relative contribution to curve progression over time is unknown. Which occurs first is important for understanding how scoliosis progresses and for developing methods to halt progression. Previous studies have not properly identified maturity and provide conflicting results. Methods Eighteen girls were followed through their adolescent growth spurt with serial spine and hand skeletal age radiographs. Each Cobb angle was divided into disc wedge angles and vertebral wedge angles. The corresponding hand radiographs provided a measure of maturity level, the Digital Skeletal Age (DSA). The disc versus bone contributions to the Cobb angle were then compared during 3 growth phases: prior to the growth spurt, during the growth spurt and after the growth spurt. Significance of relative changes was assessed with the Wilcoxon two-sided mean rank test. Results Prior to the growth spurt, there was no difference in relative contributions of the disc and the bone (3° vs 0°, p=0.38) to curve progression. During the growth spurt, the mean disc component progressed significantly more than that of the vertebrae (15° vs 0°, p=0.0002). This reversed following the growth spurt with the vertebral component progressing more than the disc (10° vs 0°, p=0.01). Conclusion Adolescent idiopathic scoliosis initially increases through disc wedging during the rapid growth spurt with progressive vertebral wedging occurring later. PMID:19940737

High-resolution ultrasonography in assessing temporomandibular joint disc position.

PubMed

Talmaceanu, Daniel; Lenghel, Lavinia Manuela; Bolog, Nicolae; Popa Stanila, Roxana; Buduru, Smaranda; Leucuta, Daniel Corneliu; Rotar, Horatiu; Baciut, Mihaela; Baciut, Grigore

2018-02-04

The purpose of this study was to determine the diagnostic value of high-resolution ultrasonography (US) in temporomandibular joint (TMJ) disc displacements. A number of 74 patients (148 TMJs) with signs and symptoms of TMJ disorders, according to the Research Diagnostic Criteria for Temporomandibular Disorders, were included in this study. All patients received US and magnetic resonance imaging (MRI) of both TMJs 1 to 5 days after the clinical examination. MRI examinations were performed using 1.5 T MRI equipment (Siemens Avanto, Siemens, Erlangen). Ultrasonographic examination was performed on a Hitachi EUB 8500 (Hitachi Medical Corp., Tokyo, Japan) scanner with L 54 M6.5-13 MHz linear transducer. MRI depicted 68 (45.95%) normal joints, 47 (31.76%) with disc displacement with reduction, 33 (22.3%) with disc displacement without reduction and 34 (22.97%) with degenerative changes. US detected 78 (52.7%) normal joints, 37 (25%) with disc displacement with reduction, 33 (22.3%) with disc displacement without reduction and 21 (14.19%) with degenerative changes. Compared to MRI, US showed a sensitivity of 93.1%, specificity of 87.88%, accuracy of 90.32%, a positive predictive value of 87.1% and a negative predictive value of 93.55% for overall diagnosis of disc displacement. The Youden index was 0.81. Based on our results, high-resolution ultrasonography showed high sensitivity, specificity and accuracy in the diagnosis of TMJ disc displacement. It could be a valuable imaging technique in assessing TMJ disc position. The diagnostic value of high-resolution ultrasonography depends strictly on the examiner's skills and on the equipment used.

Use of Faropenem as an Indicator of Carbapenemase Activity in the Enterobacteriaceae

PubMed Central

Day, Kathryn M.; Pike, Rachel; Winstanley, Trevor G.; Lanyon, Clare; Cummings, Stephen P.; Raza, Muhammad W.; Woodford, Neil

2013-01-01

The aim of this study was to determine the ability of a disc susceptibility test using faropenem (10 μg) to predict carbapenemase activity in Enterobacteriaceae. A collection of 166 isolates of carbapenemase-producing Enterobacteriaceae (CPE) and 82 isolates of Enterobacteriaceae that produced other β-lactamases was compiled from diverse sources. Disc susceptibility testing was performed using the CLSI/EUCAST methodology with discs of faropenem (10 μg), temocillin (30 μg), and four carbapenems (each 10 μg). A further prospective evaluation of the faropenem disc susceptibility test was performed using 205 consecutive isolates referred to a United Kingdom reference laboratory in parallel with molecular methods for carbapenemase detection. Of 166 isolates of CPE, 99% showed growth up to the edge of a 10-μg faropenem disc compared with only 6% of other β-lactamase producers (sensitivity, 99%; specificity, 94%). A “double zone” around 10-μg faropenem discs was frequently associated with OXA-48 producers. Of the carbapenems, the most useful agent was imipenem, where a zone diameter of ≤23 mm as a predictor of carbapenemase activity had a sensitivity of 99% and a specificity of 85%. The presence of no zone of inhibition around a 30-μg temocillin disc was a consistent feature of strains producing OXA-48 carbapenemase. For 205 isolates of Enterobacteriaceae referred to a United Kingdom reference laboratory, growth up to a 10-μg faropenem disc correctly identified 84 of 86 carbapenemase producers (98% sensitivity), with a specificity of 87%. Disc susceptibility testing using faropenem (10 μg) is a simple, convenient, and highly predictive screening test for carbapenemase-producing Enterobacteriaceae. PMID:23576544

[Effect of Basic Fibroblast Growth Factor and Transforming Growth Factor-Β1 Combined with Bone Marrow Mesenchymal Stem Cells on the Repair of Degenerated Intervertebral Discs in Rat Models].

PubMed

Jiang, Chao; Li, Da-peng; Zhang, Zhi-jian; Shu, Hao-ming; Hu, Lang; Li, Zheng-nan; Huang, Yong-hui

2015-08-01

To evaluate the effects of the combination of basic fibroblast growth factor (bFGF), transforming growth factor-Β1 (TGF-Β1), bone marrow mesenchymal stem cells (BMSCs), and temperature-responsive chitosan hydrogel (TCH) gel on the repair of degenerative intervertebral disc in rat models. Rat models of intervertebral disc degeneration were established by acupuncture. The degenerative effects were observed under magnetic resonance imaging (MRI). The BMSCs was cultured in vitro and then transfected by adenovirus with enhanced green fluorescent protein to make it carry the gene of enhanced green fluorescent protein,which functioned as fluorescence labeling. The SD rat models of intervertebral disc degeneration were divided into four groups: group A, treated with the combination of bFGF, TGF-Β1,BMSCs,and TCH gel; group B, treated with the combination of BMSCs and TCH gel;group C, treated with the combination of bFGF,TGF-Β1, and TCH gel;and group D, treated with PBS buffer solution. After the corresponding reagents were injected into the degenerative intervertebral discs of each group, the rats were cultivated for another four weeks and then the repair effects of the intervertebral discs were observed under MRI. Furthermore,the intervertebral discs of each group were taken out and observed by HE and Masson staining. The nucleus pulposus was aspirated and the expressions of aggrecan,collagen 2,Sox-9,and collagen I of nucleus pulposus of each group were tested by reverse transcription polymerase chain reaction and Western blot. The transplanted BMSCs survived in the intervertebral disc and differentiated into nucleus pulposus-like cells. MRI showed that:the signal intensity of the nucleus pulposus of group A was much higher than that of the rest groups, the signal intensity of group B was higher than that of group C, and the signal intensity of group D was the lowest,in which the dura mater spinalis was in compression and the spinal cord changed in beaded shape. The differences of the Pfirrmann grading among the four groups had statistical significance (P<0.05). The results of the HE and Masson stains showed:the intervertebral disc of group A was well-structured,the quantity of nucleus pulposus cells was larger than that of the other three groups,and the boundary between the nucleus pulposus and the annulus fibrosus was clearly defined;the quantity of the nucleus pulposus cells of group B was larger than that of group C, and the broken annulus fibrosus was not observed in group B, while the broken annulus fibrosus could be observed in group C; and, the nucleus pulposus cells of group D were replaced by fibrous tissue. The results of the reverse transcription polymerase chain reaction and Western blot tests showed that,in terms of the expressions of aggrecan,collagen 2 and Sox-9,group A was the highest, followed by group B,group C,and group D (P<0.05); in terms of the expression of collagen 1,there was no obvious difference among these four groups (P>0.05). The transplanted BMSCs can survive in the degenerative intervertebral disc and differentiate into nucleus pulposus-like cells. The combination of bFGF, TGF-Β1, BMSCs,and TCH gel has obvious repair effect on the degenerative intervertebral discs. The effect of the combination of BMSCs and TCH gel on transplantation therapy of the degenerative intervertebral discs is better than that of the combination of bFGF, TGF-Β1 and TCH gel but worse than that of the combination of bFGF, TGF-Β1, BMSCs, and TCH gel.

Comparison of Automated Analysis of Cirrus HD-OCT™ Spectral Domain Optical Coherence Tomography with Stereo Photos of the Optic Disc

PubMed Central

Sharma, Ashish; Oakley, Jonathan D.; Schiffman, Joyce C.; Budenz, Donald L.; Anderson, Douglas R.

2010-01-01

OBJECTIVE To evaluate a new automated analysis of optic disc images obtained by spectral domain optical coherence tomography (SD-OCT). Areas of the optic disc, cup, and neural rim in SD-OCT images were compared with these areas from stereoscopic photographs, to represent the current traditional optic nerve evaluation. The repeatability of measurements by each method was determined and compared. DESIGN Evaluation of diagnostic technology. PARTICIPANTS 119 healthy eyes, 23 eyes with glaucoma, and 7 suspect eyes METHODS Optic disc and cup margins were traced from stereoscopic photographs by three individuals independently. Optic disc margins and rim widths were determined automatically in SD-OCT. A subset of photographs was examined and traced a second time, and duplicate SD-OCT images were also analyzed. MAIN OUTCOME MEASUREMENTS Agreement among photograph readers, between duplicate readings, and between SD-OCT and photographs were quantified by the intraclass correlation coefficient (ICC), by the root mean square (RMS), and the standard deviation (SD) of the differences. RESULTS Optic disc areas tended to be slightly larger when judged in photographs than by SD-OCT, while cup areas were similar. Cup and optic disc areas showed good correlation (0.8) between average photographic reading and SD-OCT, but only fair correlation of rim areas (0.4). The SD-OCT was highly reproducible (ICC of 0.96 to 0.99). Each reader was also consistent with himself on duplicate readings of 21 photographs (ICC 0.80 to 0.88 for rim area, 0.95 to 0.98 for all other measurements), but reproducibility was not as good as SD-OCT. Measurements derived from SD-OCT did not differ from photographic readings more than the readings of photographs by different readers differed from each other. CONCLUSIONS Designation of the cup and optic disc boundaries by an automated analysis of SD-OCT was within the range of variable designations by different readers from color stereoscopic photographs, but use of different landmarks typically made the designation of the optic disc size somewhat smaller in the automated analysis. There was better repeatability among measurements from SD-OCT than from among readers of photographs. The repeatability of automated measurement of SD-OCT images is promising for use both in diagnosis and in monitoring of progression. PMID:21397334

Inclusion of Regional Poroelastic Material Properties Better Predicts Biomechanical Behavior of Lumbar Discs Subjected to Dynamic Loading

PubMed Central

Williams, Jamie R.; Natarajan, Raghu N.; Andersson, Gunnar B.J.

2009-01-01

Understanding the relationship between repetitive lifting and the breakdown of disc tissue over several years of exposure is difficult to study in vivo and in vitro. The aim of this investigation was to develop a three-dimensional poroelastic finite element model of a lumbar motion segment that reflects the biological properties and behaviors of in vivo disc tissues including swelling pressure due to the proteoglycans and strain dependent permeability and porosity. It was hypothesized that when modeling the annulus, prescribing tissue specific material properties will not be adequate for studying the in vivo loading and unloading behavior of the disc. Rather, regional variations of these properties, which are known to exist within the annulus, must also be included. Finite element predictions were compared to in vivo measurements published by Tyrrell et al., (Tyrrell et al., 1985) of percent change in total stature for two loading protocols, short-term creep loading and standing recovery and short-term cyclic loading with standing recovery. The model in which the regional variations of material properties in the annulus had been included provided an overall better prediction of the in vivo behavior as compared to the model in which the annulus properties were assumed to be homogenous. This model will now be used to study the relationship between repetitive lifting and disc degeneration. PMID:17156786

Comparative experiments for in vivo fibroplasia and biological stability of four porous polymers intended for use in the Seoul-type keratoprosthesis

PubMed Central

Kim, M K; Lee, J L; Wee, W R; Lee, J H

2002-01-01

Aims: To evaluate in vivo fibroplasia and biological stability of porous polymers intended for use in the Seoul-type keratoprosthesis (S-KPro). Methods: Four porous polymers (polypropylene, two kinds of polyethylene terephthalate (PE70 and PE50), and polyurethane) were investigated. Discs of polymers were inserted into the corneal stroma of rabbits for a 2 and 5 month period. Corneal oedema and neovascularisation were evaluated. The fibroplasia and collagen deposition were examined under light and transmission electron microscopy. S-KPros, whose skirt was made of four types of polymer, were implanted into the rabbits' eyes. The retention time and complications were evaluated. Results: Neovascularisation and corneal oedema were found in all of the disc inserted eyes, but the corneal oedema subsided within 2 months in most of the eyes. The mean number of fibroblasts increased significantly in polypropylene and PE50 disc inserted eyes compared with polyurethane disc inserted eyes. Plentiful collagen deposition was also found in both polypropylene and PE50 disc inserted eyes. Mean retention time in the polypropylene SK-Pro implanted eyes was longer than that of the other eyes (20.7 weeks). The PE70 skirt induced corneal melting around the prosthesis. Conclusion: Polypropylene encourages fibroblast ingrowth and shows good biological stability when used as a skirt material in S-KPro. PMID:12084755

Engineering Human TMJ Discs with Protein-Releasing 3D-Printed Scaffolds.

PubMed

Legemate, K; Tarafder, S; Jun, Y; Lee, C H

2016-07-01

The temporomandibular joint (TMJ) disc is a heterogeneous fibrocartilaginous tissue positioned between the mandibular condyle and glenoid fossa of the temporal bone, with important roles in TMJ functions. Tissue engineering TMJ discs has emerged as an alternative approach to overcoming limitations of current treatments for TMJ disorders. However, the anisotropic collagen orientation and inhomogeneous fibrocartilaginous matrix distribution present challenges in the tissue engineering of functional TMJ discs. Here, we developed 3-dimensional (3D)-printed anatomically correct scaffolds with region-variant microstrand alignment, mimicking anisotropic collagen alignment in the TMJ disc and corresponding mechanical properties. Connective tissue growth factor (CTGF) and transforming growth factor beta 3 (TGFβ3) were then delivered in the scaffolds by spatially embedding CTGF- or TGFβ3-encapsulated microspheres (µS) to reconstruct the regionally variant fibrocartilaginous matrix in the native TMJ disc. When cultured with human mesenchymal stem/progenitor cells (MSCs) for 6 wk, 3D-printed scaffolds with CTGF/TGFβ3-µS resulted in a heterogeneous fibrocartilaginous matrix with overall distribution of collagen-rich fibrous structure in the anterior/posterior (AP) bands and fibrocartilaginous matrix in the intermediate zone, reminiscent of the native TMJ disc. High dose of CTGF/TGFβ3-µS (100 mg µS/g of scaffold) showed significantly more collagen II and aggrecan in the intermediate zone than a low dose (50 mg µS/g of scaffold). Similarly, a high dose of CTGF/TGFβ3-µS yielded significantly higher collagen I expression in the AP bands compared with the low-dose and empty µS. From stress relaxation tests, the ratio of relaxation modulus to instantaneous modulus was significantly smaller with CTGF/TGFβ3-µS than empty µS. Similarly, a significantly higher coefficient of viscosity was achieved with the high dose of CTGF/TGFβ3-µS compared with the low-dose and empty µS, suggesting the dose effect of CTGF and TGFβ3 on fibrocartilage formation. Together, our findings may represent an efficient approach to engineering the TMJ disc graft with anisotropic scaffold microstructure, heterogeneous fibrocartilaginous matrix, and region-dependent viscoelastic properties. © International & American Associations for Dental Research 2016.

Multiwavelength studies of the gas and dust disc of IRAS 04158+2805

NASA Astrophysics Data System (ADS)

Glauser, A. M.; Ménard, F.; Pinte, C.; Duchêne, G.; Güdel, M.; Monin, J.-L.; Padgett, D. L.

2008-07-01

We present a study of the circumstellar environment of IRAS 04158+2805 based on multi-wavelength observations and models. Images in the optical and near-infrared, a polarisation map in the optical, and mid-infrared spectra were obtained with VLT-FORS1, CFHT-IR, and Spitzer-IRS. Additionally we used an X-ray spectrum observed with Chandra. We interpret the observations in terms of a central star surrounded by an axisymmetric circumstellar disc, but without an envelope, to test the validity of this simple geometry. We estimate the structural properties of the disc and its gas and dust content. We modelled the dust disc with a 3D continuum radiative transfer code, MCFOST, based on a Monte-Carlo method that provides synthetic scattered light images and polarisation maps, as well as spectral energy distributions. We find that the disc images and spectral energy distribution narrowly constrain many of the disc model parameters, such as a total dust mass of 1.0-1.75×10-4 M_⊙ and an inclination of 62°-63°. The maximum grain size required to fit all available data is of the order of 1.6-2.8 μm although the upper end of this range is loosely constrained. The observed optical polarisation map is reproduced well by the same disc model, suggesting that the geometry we find is adequate and the optical properties are representative of the visible dust content. We compare the inferred dust column density to the gas column density derived from the X-ray spectrum and find a gas-to-dust ratio along the line of sight that is consistent with the ISM value. To our knowledge, this measurement is the first to directly compare dust and gas column densities in a protoplanetary disc. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based also on data collected at ESO/VLT during observation program 68-C.0171.

Determination of cup-to-disc ratio of optical nerve head for diagnosis of glaucoma on stereo retinal fundus image pairs

NASA Astrophysics Data System (ADS)

Muramatsu, Chisako; Nakagawa, Toshiaki; Sawada, Akira; Hatanaka, Yuji; Hara, Takeshi; Yamamoto, Tetsuya; Fujita, Hiroshi

2009-02-01

A large cup-to-disc (C/D) ratio, which is the ratio of the diameter of the depression (cup) to that of the optical nerve head (ONH, disc), can be one of the important signs for diagnosis of glaucoma. Eighty eyes, including 25 eyes with the signs of glaucoma, were imaged by a stereo retinal fundus camera. An ophthalmologist provided the outlines of cup and disc on a regular monitor and on the stereo display. The depth image of the ONH was created by determining the corresponding pixels in a pair of images based on the correlation coefficient in localized regions. The areas of the disc and cup were determined by use of the red component in one of the color images and by use of the depth image, respectively. The C/D ratio was determined based on the largest vertical lengths in the cup and disc areas, which was then compared with that by the ophthalmologist. The disc areas determined by the computerized method agreed relatively well with those determined by the ophthalmologist, whereas the agreement for the cup areas was somewhat lower. When C/D ratios were employed for distinction between the glaucomatous and non-glaucomatous eyes, the area under the receiver operating characteristic curve (AUC) was 0.83. The computerized analysis of ONH can be useful for diagnosis of glaucoma.

Constraints on the temperature inhomogeneity in quasar accretion discs from the ultraviolet-optical spectral variability

NASA Astrophysics Data System (ADS)

Kokubo, Mitsuru

2015-05-01

The physical mechanisms of the quasar ultraviolet (UV)-optical variability are not well understood despite the long history of observations. Recently, Dexter & Agol presented a model of quasar UV-optical variability, which assumes large local temperature fluctuations in the quasar accretion discs. This inhomogeneous accretion disc model is claimed to describe not only the single-band variability amplitude, but also microlensing size constraints and the quasar composite spectral shape. In this work, we examine the validity of the inhomogeneous accretion disc model in the light of quasar UV-optical spectral variability by using five-band multi-epoch light curves for nearly 9 000 quasars in the Sloan Digital Sky Survey (SDSS) Stripe 82 region. By comparing the values of the intrinsic scatter σint of the two-band magnitude-magnitude plots for the SDSS quasar light curves and for the simulated light curves, we show that Dexter & Agol's inhomogeneous accretion disc model cannot explain the tight inter-band correlation often observed in the SDSS quasar light curves. This result leads us to conclude that the local temperature fluctuations in the accretion discs are not the main driver of the several years' UV-optical variability of quasars, and consequently, that the assumption that the quasar accretion discs have large localized temperature fluctuations is not preferred from the viewpoint of the UV-optical spectral variability.

Biochemical validity of imaging techniques (X-ray, MRI, and dGEMRIC) in degenerative disc disease of the human cervical spine-an in vivo study.

PubMed

Bostelmann, Richard; Bostelmann, Tamara; Nasaca, Adrian; Steiger, Hans Jakob; Zaucke, Frank; Schleich, Christoph

2017-02-01

On a molecular level, maturation or degeneration of human intervertebral disc is among others expressed by the content of glycosaminoglycans (GAGs). According to the degenerative status, the disc content can differ in nucleus pulposus (NP) and annulus fibrosus (AF), respectively. Research in this area was conducted mostly on postmortem samples. Although several radiological classification systems exist, none includes biochemical features. Therefore, we focused our in vivo study on a widely spread and less expensive imaging technique for the cervical spine and the correlation of radiological patterns to biochemical equivalents in the intervertebral discs. The aim of this pilot study was to (1) measure the GAG content in human cervical discs, (2) to investigate whether a topographic biochemical GAG pattern can be found, and (3) whether there is a correlation between imaging data (X-ray and magnetic resonance imaging [MRI] including delayed gadolinium-enhanced MRI of cartilage [dGEMRIC] as a special imaging technique of cartilage) and the biochemical data. We conducted a prospective experimental pilot study. Only non-responders to conservative therapy were included. All subjects were physically and neurologically examined, and they completed their questionnaires. Visual analogue scale neck and arm, Neck Disability Index score, radiological parameters (X-rays, MRI, dGEMRIC), and the content of GAG in the cervical disc were assessed. After surgical removal of 12 discs, 96 fractions of AF and NP were biochemically analyzed for the GAG content using dimethylmethylene blue assay. A quantitative pattern of GAGs in the human cervical disc was identified. There were (1) significantly (p<.001) higher values of GAGs (µg GAG/mg tissue) in the NP (169.9 SD 37.3) compared with the AF (132.4 SD 42.2), and (2) significantly (p<.005) higher values of GAGs in the posterior (right/left: 149.9/160.2) compared with the anterior (right/left: 112.0/120.2) part of the AF. Third, we found in dGEMRIC imaging a significantly (p<.008) different distribution of GAGs in the cervical disc (NP 1083.3 ms [SD 248.6], AF 925.9 ms [SD 137.6]). Finally, we found that grading of disc degeneration in X-ray and MRI was significantly correlated with neither AF- nor NP-GAG content. The GAG content in human cervical discs can be detected in vivo and is subject to a significantly (p<.05) region-specific pattern (AF vs. NP; anterior vs. posterior in the AF). Up to the levels of AF and NP, this is reproducible in MRI in dGEMRIC technique, but not in X-ray or standard MRI sequences. Potentially, the MRI in dGEMRIC technique can be used as a non-invasive in vivo indicator for disc degeneration in the cervical spine. Copyright © 2016 Elsevier Inc. All rights reserved.

Preflight, In-Flight, and Postflight Imaging of the Cervical and Lumbar Spine in Astronauts.

PubMed

Harrison, Michael F; Garcia, Kathleen M; Sargsyan, Ashot E; Ebert, Douglas; Riascos-Castaneda, Roy F; Dulchavsky, Scott A

2018-01-01

Back pain is a common complaint during spaceflight that is commonly attributed to intervertebral disc swelling in microgravity. Ultrasound (US) represents the only imaging modality on the International Space Station (ISS) to assess its etiology. The present study investigated: 1) The agreement and correlation of spinal US assessments as compared to results of pre- and postflight MRI studies; and 2) the trend in intervertebral disc characteristics over the course of spaceflight to ISS. Seven ISS astronauts underwent pre- and postflight US examinations that included anterior disc height and anterior intervertebral angles with comparison to pre- and postflight MRI results. In-flight US images were analyzed for changes in disc height and angle. Statistical analysis included repeated measures ANOVA with Bonferroni post hoc analysis, Bland-Altman plots, and Pearson correlation. Bland-Altman plots revealed significant disagreement between disc heights and angles for MRI and US measurements while significant Pearson correlations were found in MRI and US measurements for lumbar disc height (r2 = 0.83) and angle (r2 = 0.89), but not for cervical disc height (r2 = 0.26) or angle (r2 = 0.02). Changes in anterior intervertebral disc angle-initially increases followed by decreases-were observed in the lumbar and cervical spine over the course of the long-duration mission. The cervical spine demonstrated a loss of total disc height during in-flight assessments (∼0.5 cm). Significant disagreement but significant correlation was noted between US and MRI measurements of disc height and angle. Consistency in imaging modality is important for trending measurements and more research related to US technique is required.Harrison MF, Garcia KM, Sargsyan AE, Ebert D, Riascos-Castaneda RF, Dulchavsky SA. Preflight, in-flight, and postflight imaging of the cervical and lumbar spine in astronauts. Aerosp Med Hum Perform. 2018; 89(1):32-40.

Defocus Incorporated Soft Contact (DISC) lens slows myopia progression in Hong Kong Chinese schoolchildren: a 2-year randomised clinical trial

PubMed Central

Lam, Carly Siu Yin; Tang, Wing Chun; Tse, Dennis Yan-Yin; Tang, Ying Yung; To, Chi Ho

2014-01-01

Aims To determine if ‘Defocus Incorporated Soft Contact’ (DISC) lens wear slows childhood myopia progression. Methods A 2-year double-blind randomised controlled trial was carried out in 221 children aged 8–13 years, with myopia between −1.00 and −5.00 Dioptres (D) and astigmatism ≤1.00 D. Subjects were randomly assigned to the DISC (n=111) or single vision (SV; n=110) contact lens group. DISC lenses incorporated concentric rings, which provided an addition of +2.50 D, alternating with the normal distance correction. Refractive error (cycloplegic autorefraction) and axial length were measured at 6-month intervals. Differences between groups were analysed using unpaired t test. Results In total, 128 children completed the study, n=65 in the DISC group and n=63 in the SV group. Myopia progressed 25% more slowly for children in the DISC group compared with those in the control group (0.30 D/year; 95% CI −0.71 to −0.47 vs 0.4 D/year; 95% CI −0.93 to −0.65, p=0.031). Likewise, there was less axial elongation for children in the DISC versus SV groups (0.13 mm/year; 95% CI 0.20 to 0.31 vs 0.18 mm/year; 95% CI 0.30 to 0.43, p=0.009). Treatment effect correlated positively with DISC lens wearing time (r=0.342; p=0.005). Indeed, myopia in children who wore the DISC lenses for five or more hours/day progressed 46% (mean difference=−0.382 D, p=0.001; 95% CI −0.59 to −0.17) less than those in the SV group. Conclusions The daily wearing of DISC lens significantly slowed myopia progression and axial elongation in Hong Kong schoolchildren. The findings demonstrated that simultaneous clear vision with constant myopic defocus can retard myopia progression. PMID:24169657

Planet population synthesis driven by pebble accretion in cluster environments

NASA Astrophysics Data System (ADS)

Ndugu, N.; Bitsch, B.; Jurua, E.

2018-02-01

The evolution of protoplanetary discs embedded in stellar clusters depends on the age and the stellar density in which they are embedded. Stellar clusters of young age and high stellar surface density destroy protoplanetary discs by external photoevaporation and stellar encounters. Here, we consider the effect of background heating from newly formed stellar clusters on the structure of protoplanetary discs and how it affects the formation of planets in these discs. Our planet formation model is built on the core accretion scenario, where we take the reduction of the core growth time-scale due to pebble accretion into account. We synthesize planet populations that we compare to observations obtained by radial velocity measurements. The giant planets in our simulations migrate over large distances due to the fast type-II migration regime induced by a high disc viscosity (α = 5.4 × 10-3). Cold Jupiters (rp > 1 au) originate preferably from the outer disc, due to the large-scale planetary migration, while hot Jupiters (rp < 0.1 au) preferably form in the inner disc. We find that the formation of gas giants via pebble accretion is in agreement with the metallicity correlation, meaning that more gas giants are formed at larger metallicity. However, our synthetic population of isolated stars host a significant amount of giant planets even at low metallicity, in contradiction to observations where giant planets are preferably found around high metallicity stars, indicating that pebble accretion is very efficient in the standard pebble accretion framework. On the other hand, discs around stars embedded in cluster environments hardly form any giant planets at low metallicity in agreement with observations, where these changes originate from the increased temperature in the outer parts of the disc, which prolongs the core accretion time-scale of the planet. We therefore conclude that the outer disc structure and the planet's formation location determines the giant planet occurrence rate and the formation efficiency of cold and hot Jupiters.

The effect of cervical posterior foraminotomy on segmental range of motion in the setting of total disc arthroplasty.

PubMed

Bevevino, Adam J; Lehman, Ronald A; Kang, Daniel G; Gwinn, David E; Dmitriev, Anton E

2014-09-01

Human cadaveric biomechanical analysis. To investigate the effect on cervical spine segmental stability that results from a posterior foraminotomy after cervical disc arthroplasty (CDA). Posterior foraminotomy offers the ability to decompress cervical nerves roots while avoiding the need to extend a previous fusion or revise an arthroplasty to a fusion. However, the safety of a foraminotomy in the setting of CDA is unknown. Segmental nondestructive range of motion (ROM) was analyzed in 9 human cadaveric cervical spine specimens. After intact testing, each specimen was sequentially tested according to the following 4 experimental groups: group 1=C5-C6 CDA, group 2=C5-C6 CDA with unilateral C5-C6 foraminotomy, group 3=C5-C6 CDA with bilateral C5-C6 foraminotomy, and group 4=C5-C6 CDA with C5-C6 and C4-C5 bilateral foraminotomy. No differences in ROM were found between the intact, CDA, and foraminotomy specimens at C4-C5 or C6-C7. There was a step-wise increase in C5-C6 axial rotation from the intact state (8°) to group 4 (12°), although the difference did not reach statistical significance. At C5-C6, the degree of lateral bending remained relatively constant. Flexion and extension at C5-C6 was significantly higher in the foraminotomy specimens, groups 2 (18.1°), 3 (18.6°), and 4 (18.2°), compared with the intact state, 11.2°. However, no ROM difference was found within foraminotomy groups (2-4) or between the foraminotomy groups and the CDA group (group 1), 15.3°. Our results indicate that cervical stability is not significantly decreased by the presence, number, or level of posterior foraminotomies in the setting of CDA. The addition of foraminotomies to specimens with a pre-existing CDA resulted in small and insignificant increases in segmental ROM. Therefore, biomechanically, posterior foraminotomy/foraminotomies may be considered a safe and viable option in the setting of recurrent or adjacent level radiculopathy after cervical disc replacement. N/A.

Clinical and Radiologic Features of 3 Reconstructive Procedures for the Surgical Management of Patients with Bilevel Cervical Degenerative Disc Disease at a Minimum Follow-Up Period of 5 Years: A Comparative Study.

PubMed

Wang, Kai-Feng; Duan, Shuo; Zhu, Zhen-Qi; Liu, Hai-Ying; Liu, Chen-Jun; Xu, Shuai

2018-05-01

To assess the mid-long-term follow-up of the safety and efficacy of anterior cervical discectomy and fusion (ACDF), cervical artificial disc replacement (CADR) and hybrid surgery (HS) for bilevel cervical degenerative disc disease (cDDD). 77 patients who underwent ACDF, HS, and CADR were retrospectively reviewed. Clinical effects were evaluated based on Neck Disability Index (NDI), Visual Analog Scale (VAS), and Japanese Orthopedic Association (JOA) scores and the Odom criteria. Radiographic outcomes were evaluated, including cervical range of motion (ROM), ROM in the operative and adjacent segments, incidence of degeneration in the adjacent segments (ASD), and heterotopic ossification (HO). NDI, VAS, and JOA scores significantly improved in all patients after surgery without significant differences between groups. The excellent-to-good ratio in the Odom scale was 28/30 for the HS group, 30/33 for the ACDF group, and 13/14 for the CADR group. No significant differences in clinical outcomes or complication were found between groups (P > 0.05). Furthermore, the HS and CADR groups had less decreased ROM in the cervical and operative segments and less compensatory ROM in adjacent segments (P < 0.05). By contrast, the ACDF group had decreased ROM in the cervical and operative segments and significantly increased ROM in adjacent segments (P < 0.05). Moreover, the incidence of ASD was higher in the ACDF group, but the difference was not statistically significant (P > 0.05). HO was found in 10 patients (33.3%) in the HS group and 5 patients (35.7%) in the CADR group. HS was superior to ACDF with regard to equivalent clinical outcomes in the mid-long-term follow-up. Furthermore, HS was superior in the maintenance of ROM and had less impact on its adjacent segments. The efficacy of HS is similar to that of CADR. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Applications of 3D printing in the management of severe spinal conditions.

PubMed

Provaggi, Elena; Leong, Julian J H; Kalaskar, Deepak M

2017-06-01

The latest and fastest-growing innovation in the medical field has been the advent of three-dimensional printing technologies, which have recently seen applications in the production of low-cost, patient-specific medical implants. While a wide range of three-dimensional printing systems has been explored in manufacturing anatomical models and devices for the medical setting, their applications are cutting-edge in the field of spinal surgery. This review aims to provide a comprehensive overview and classification of the current applications of three-dimensional printing technologies in spine care. Although three-dimensional printing technology has been widely used for the construction of patient-specific anatomical models of the spine and intraoperative guide templates to provide personalized surgical planning and increase pedicle screw placement accuracy, only few studies have been focused on the manufacturing of spinal implants. Therefore, three-dimensional printed custom-designed intervertebral fusion devices, artificial vertebral bodies and disc substitutes for total disc replacement, along with tissue engineering strategies focused on scaffold constructs for bone and cartilage regeneration, represent a set of promising applications towards the trend of individualized patient care.

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

DOE PAGES

Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; ...

2017-02-16

Here, magnesium diboride (MgB 2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB 2. MgB 2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB 2 and excellent thermal conductivity of Cu. We have grown MgB 2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB 2 coating on top of a Mg–Cu alloy layer with occasionalmore » intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm –2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.« less

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza

Here, magnesium diboride (MgB 2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB 2. MgB 2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB 2 and excellent thermal conductivity of Cu. We have grown MgB 2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB 2 coating on top of a Mg–Cu alloy layer with occasionalmore » intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm –2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.« less

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza

Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High Tmore » c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.« less

Comparison between cranial thoracic intervertebral disc herniations in German Shepherd dogs and other large breed dogs.

PubMed

Gaitero, Luis; Nykamp, Stephanie; Daniel, Rob; Monteith, Gabrielle

2013-01-01

Cranial thoracic intervertebral disc herniations have been reported to be rare in dogs due to the presence of the intercapital ligament, however some studies have proposed they may not be uncommon in German Shepherd dogs. The purpose of this retrospective study was to compare cranial thoracic intervertebral disc herniations in German Shepherd dogs and other large breed dogs (control group). Medical records at the Ontario Veterinary College were searched for German Shepherd dogs and other large breed dogs that had magnetic resonance imaging studies including the T1-T9 region. For each dog and each disc space from T1-T9, three variables (compression, disc degeneration, and herniation) were recorded and graded based on review of sagittal T2-weighted images. Twenty-three German Shepherd dogs and 47 other large breed dogs met inclusion criteria. The German Shepherd dog group had higher scores than the control group for compression (P = 0.0099) and herniation (P < 0.001), but not disc degeneration (P = 0.97). In the German Shepherd dog group, intervertebral discs T2-T3 and T4-T5 had an increased risk for compression and T3-T4 had an increased risk for compression and herniation. Findings from this study indicated that German Shepherd dogs may be more likely than other large breed dogs to have spinal cord compression due to cranial thoracic disc herniations. Imaging of the cranial thoracic spine, including T2-T3, is recommended for German Shepherd dogs with T3-L3 neurological signs. © 2012 Veterinary Radiology & Ultrasound.

Agreement of glaucoma specialists and experienced optometrists in gonioscopy and optic disc evaluation

PubMed Central

Kumar, Addepalli U.; Jonnadula, Ganesh B.; Garudadri, Chandrasekhar; Rao, Harsha L.; Senthil, Sirisha; Papas, Eric B.; Sankaridurg, Padmaja; Khanna, Rohit C.

2013-01-01

Purpose To compare the diagnostic performance of glaucoma specialists and experienced optometrists in gonioscopy and optic disc assessment. Methods This study was done to validate the diagnostic performance of two experienced optometrists for using their skills of detecting glaucoma using gonioscopy and optic disc assessment in a major epidemiological study, the L V Prasad Eye Institute Glaucoma Epidemiology and Molecular Genetics Study (LVPEI-GLEAMS). Gonioscopic findings for 150 eyes were categorized as 0, 1 and 2 for open angle, primary angle closure suspect (PACS) and primary angle closure (PAC) respectively. Optic disc findings for 200 eyes were categorized as 0, 1 and 2 for normal, suspects and glaucomatous respectively. Weighted kappa (κ) and diagnostic accuracy parameters were calculated. Two optometrists (#1 and #2) participated in the study. Results Agreement between glaucoma specialists and optometrist for interpretation of gonioscopy to discriminate PACS and PAC from open angles and for interpretation of optic disc to discriminate glaucomatous and suspicious discs from normal, the kappa (κ) was 0.92 and 0.84 and 0.90 and 0.89 for optometrists #1 and #2 respectively. Sensitivities and specificities were above 90% for gonioscopy. Optic disc evaluation had specificities greater than 95% to discriminate normal from glaucomatous discs while the sensitivities were 83% and 93% for optometrists #1 and #2 respectively. Conclusion Agreement between optometrists and glaucoma specialists, in diagnostic performance of gonioscopy and optic assessment was excellent with high sensitivity and specificity. Hence, we conclude that the experienced optometrists can detect glaucoma accurately in the LVPEI-GLEAMS.

Towards a population synthesis model of self-gravitating disc fragmentation and tidal downsizing II: the effect of fragment-fragment interactions

NASA Astrophysics Data System (ADS)

Forgan, D. H.; Hall, C.; Meru, F.; Rice, W. K. M.

2018-03-01

It is likely that most protostellar systems undergo a brief phase where the protostellar disc is self-gravitating. If these discs are prone to fragmentation, then they are able to rapidly form objects that are initially of several Jupiter masses and larger. The fate of these disc fragments (and the fate of planetary bodies formed afterwards via core accretion) depends sensitively not only on the fragment's interaction with the disc, but also with its neighbouring fragments. We return to and revise our population synthesis model of self-gravitating disc fragmentation and tidal downsizing. Amongst other improvements, the model now directly incorporates fragment-fragment interactions while the disc is still present. We find that fragment-fragment scattering dominates the orbital evolution, even when we enforce rapid migration and inefficient gap formation. Compared to our previous model, we see a small increase in the number of terrestrial-type objects being formed, although their survival under tidal evolution is at best unclear. We also see evidence for disrupted fragments with evolved grain populations - this is circumstantial evidence for the formation of planetesimal belts, a phenomenon not seen in runs where fragment-fragment interactions are ignored. In spite of intense dynamical evolution, our population is dominated by massive giant planets and brown dwarfs at large semimajor axis, which direct imaging surveys should, but only rarely, detect. Finally, disc fragmentation is shown to be an efficient manufacturer of free-floating planetary mass objects, and the typical multiplicity of systems formed via gravitational instability will be low.

Tiny Particles, So Far Away

NASA Image and Video Library

2005-01-10

NASA's Spitzer Space Telescope recently captured these images of the star Vega, located 25 light years away in the constellation Lyra. Spitzer was able to detect the heat radiation from the cloud of dust around the star and found that the debris disc is much larger than previously thought. This side by side comparison, taken by Spitzer's multiband imaging photometer, shows the warm infrared glows from dust particles orbiting the star at wavelengths of 24 microns (figure 2 in blue) and 70 microns (figure 3 in red). Both images show a very large, circular and smooth debris disc. The disc radius extends to at least 815 astronomical units. (One astronomical unit is the distance from Earth to the Sun, which is 150-million kilometers or 93-million miles). Scientists compared the surface brightness of the disc in the infrared wavelengths to determine the temperature distribution of the disc and then infer the corresponding particle size in the disc. Most of the particles in the disc are only a few microns in size, or 100 times smaller than a grain of Earth sand. These fine dust particles originate from collisions of embryonic planets near the star at a radius of approximately 90 astronomical units, and are then blown away by Vega's intense radiation. The mass and short lifetime of these small particles indicate that the disc detected by Spitzer is the aftermath of a large and relatively recent collision, involving bodies perhaps as big as the planet Pluto. The images are 3 arcminutes on each side. North is oriented upward and east is to the left. http://photojournal.jpl.nasa.gov/catalog/PIA07218

Percutaneous Transcatheter One-Step Mechanical Aortic Disc Valve Prosthesis Implantation: A Preliminary Feasibility Study in Swine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sochman, Jan; Peregrin, Jan H.; Rocek, Miloslav

Purpose. To evaluate the feasibility of one-step implantation of a new type of stent-based mechanical aortic disc valve prosthesis (MADVP) above and across the native aortic valve and its short-term function in swine with both functional and dysfunctional native valves. Methods. The MADVP consisted of a folding disc valve made of silicone elastomer attached to either a nitinol Z-stent (Z model) or a nitinol cross-braided stent (SX model). Implantation of 10 MADVPs (6 Z and 4 SX models) was attempted in 10 swine: 4 (2 Z and 2 SX models) with a functional native valve and 6 (4 Z andmore » 2 SX models) with aortic regurgitation induced either by intentional valve injury or by MADVP placement across the native valve. MADVP function was observed for up to 3 hr after implantation. Results. MADVP implantation was successful in 9 swine. One animal died of induced massive regurgitation prior to implantation. Four MADVPs implanted above functioning native valves exhibited good function. In 5 swine with regurgitation, MADVP implantation corrected the induced native valve dysfunction and the device's continuous good function was observed in 4 animals. One MADVP (SX model) placed across native valve gradually migrated into the left ventricle. Conclusion. The tested MADVP can be implanted above and across the native valve in a one-step procedure and can replace the function of the regurgitating native valve. Further technical development and testing are warranted, preferably with a manufactured MADVP.« less

Effects of surface finishing conditions on the biocompatibility of a nickel-chromium dental casting alloy.

PubMed

McGinley, Emma Louise; Coleman, David C; Moran, Gary P; Fleming, Garry J P

2011-07-01

To assess the effects of surface finishing condition (polished or alumina particle air abraded) on the biocompatibility of direct and indirect exposure to a nickel-chromium (Ni-Cr) d.Sign®10 dental casting alloy on oral keratinocytes. Biocompatibility was performed by assessing cellular viability and morphology, metabolic activity, cellular toxicity and presence of inflammatory cytokine markers. Discs of d.Sign®10 were cast, alumina particle air abraded and half were polished before surface roughness was determined by profilometry. Biocompatibility was assessed by placing the discs directly or indirectly (with immersion solutions) into contact with TR146 monolayers. Metal ion release was determined by ICP-MS. Cell viability was assessed by trypan blue dye exclusion, metabolic activity by XTT and cellular toxicity by LDH. Inflammatory cytokine analysis was performed using sandwich ELISAs. The mean polished Ra value was significantly reduced (P<0.001) compared with the alumina particle air abraded discs but metal ion release was significantly increased for the polished discs. Significant reductions in cell density of polished compared with alumina particle air abraded discs was observed following direct or indirect exposure. A significant reduction in metabolic activity, increase in cellular toxicity and an increase in the presence of inflammatory cytokine markers was highlighted for the polished relative to the alumina particle air abraded discs at 24h. Finishing condition of the Ni-Cr dental alloy investigated has important clinical implications. The approach of employing cell density and morphology, metabolic activity, cellular toxicity levels and inflammatory marker responses to TR146 epithelial cells combined with ICP-MS afforded the authors an increased insight into the complex processes dental alloys undergo in the oral environment. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

First analysis of solar structures in 1.21 mm full-disc ALMA image of the Sun

NASA Astrophysics Data System (ADS)

Brajša, R.; Sudar, D.; Benz, A. O.; Skokić, I.; Bárta, M.; Pontieu, B. De; Kim, S.; Kobelski, A.; Kuhar, M.; Shimojo, M.; Wedemeyer, S.; White, S.; Yagoubov, P.; Yan, Y.

2018-05-01

Context. Various solar features can be seen in emission or absorption on maps of the Sun in the millimetre and submillimetre wavelength range. The recently installed Atacama Large Millimetre/submillimetre Array (ALMA) is capable of observing the Sun in that wavelength range with an unprecedented spatial, temporal and spectral resolution. To interpret solar observations with ALMA, the first important step is to compare solar ALMA maps with simultaneous images of the Sun recorded in other spectral ranges. Aims: The first aim of the present work is to identify different structures in the solar atmosphere seen in the optical, infrared, and EUV parts of the spectrum (quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points) in a full-disc solar ALMA image. The second aim is to measure the intensities (brightness temperatures) of those structures and to compare them with the corresponding quiet Sun level. Methods: A full-disc solar image at 1.21 mm obtained on December 18, 2015, during a CSV-EOC campaign with ALMA is calibrated and compared with full-disc solar images from the same day in Hα line, in He I 1083 nm line core, and with various SDO images (AIA at 170 nm, 30.4 nm, 21.1 nm, 19.3 nm, and 17.1 nm and HMI magnetogram). The brightness temperatures of various structures are determined by averaging over corresponding regions of interest in the calibrated ALMA image. Results: Positions of the quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points are identified in the ALMA image. At the wavelength of 1.21 mm, active regions appear as bright areas (but sunspots are dark), while prominences on the disc and coronal holes are not discernible from the quiet Sun background, despite having slightly less intensity than surrounding quiet Sun regions. Magnetic inversion lines appear as large, elongated dark structures and coronal bright points correspond to ALMA bright points. Conclusions: These observational results are in general agreement with sparse earlier measurements at similar wavelengths. The identification of coronal bright points represents the most important new result. By comparing ALMA and other maps, it was found that the ALMA image was oriented properly and that the procedure of overlaying the ALMA image with other images is accurate at the 5 arcsec level. The potential of ALMA for physics of the solar chromosphere is emphasised.

Leaflet embolisation from Duromedics valves: a report of two cases.

PubMed

Kumar, N; Balasundaram, S; Rickard, M; al Halees, Z; Duran, C M

1991-12-01

Embolization of parts of mechanical valves has been reported since the inception of prosthetic valve implantation. We report here two cases of embolization of one hemileaflet of a Duromedic bileaflet prosthesis in the mitral position due to a pivot fracture. Both presented with moderately severe mitral regurgitation and pulmonary edema and were successfully managed by replacement of the malfunctioning prostheses. The embolised disc was located in the left common iliac artery by abdominal ultrasound and removed by an inguinal, retroperitoneal approach with low morbidity. Both patients left hospital and are doing well to-date.

Validation of Tethya samaaii Ribeiro & Muricy, 2011, replacement name for the sponge Tethya rubra Samaai & Gibbons, 2005 (Demospongiae, Tethyida, Tethyidae).

PubMed

Samaai, Toufiek; Gibbons, Mark J; Muricy, Guilherme

2017-11-14

Tethya samaaii Ribeiro & Muricy, 2011 is a massive, irregularly globular or sub-spherical sponge with basal rooting processes or a disc-like attachment (Figure 1A). It was described from Oudekraal, on the west coast of South Africa as Tethya rubra Samaai & Gibbons, 2005 based on specimens collected during two surveys in 1996 (Samaai & Gibbons 2005). This species was later reported from Algoa Bay, on the southeast coast of South Africa by Waterworth et al. (2017).

In vitro effect of a corrosive hostile ocular surface on candidate biomaterials for keratoprosthesis skirt

PubMed Central

Tan, Xiao Wei; Riau, Andri; Shi, Zhi Long; Tan, Anna C S; Neoh, Koon Gee; Khor, Khiam Aik; Beuerman, Roger W; Tan, Donald; Mehta, Jodhbir S

2012-01-01

Aim Keratoprosthesis (KPro) devices are prone to long-term corrosion and microbiological assault. The authors aimed to compare the inflammatory response and material dissolution properties of two candidate KPro skirt materials, hydroxyapatite (HA) and titania (TiO2) in a simulated in vitro cornea inflammation environment. Methods Lipopolysaccharide-stimulated cytokine secretions were evaluated with human corneal fibroblasts on both HA and TiO2. Material specimens were subjected to electrochemical and long-term incubation test with artificial tear fluid (ATF) of various acidities. Topography and surface roughness of material discs were analysed by scanning electron microscopy and atomic force microscopy. Results There were less cytokines secreted from human corneal fibroblasts seeded on TiO2 substrates as compared with HA. TiO2 was more resistant to the corrosion effect caused by acidic ATF in contrast to HA. Moreover, the elemental composition of TiO2 was more stable than HA after long-term incubation with ATF. Conclusions TiO2 is more resistant to inflammatory degradation and has a higher corrosion resistance as compared with HA, and in this regard may be a suitable material to replace HA as an osteo-odonto-keratoprosthesis skirt. This would reduce resorption rates for KPro surgery. PMID:22802307

Dynamic foraminal dimensions during neck extension and rotation in fusion and artificial disc replacement: an observational study.

PubMed

Yeni, Yener N; Baumer, Timothy; Oravec, Daniel; Basheer, Azam; McDonald, Colin P; Bey, Michael J; Bartol, Stephen W; Chang, Victor

2018-04-01

Changes in the dimensions of the cervical neural foramina (CNF) are considered to be a key factor in nerve root compression and development of cervical radiculopathy. However, to what extent foraminal geometry differs between patients who underwent anterior cervical discectomy and fusion (ACDF) and those who underwent total disc arthroplasty with an artificial disc (AD) during physiological motion is largely unknown. The objective of this study is to compare CNF dimensions during physiological neck motion between ACDF and AD. This is a retrospective comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution. A total of 16 single-level C5-C6 ACDF (4 males, 12 females; 28-71 years) and 7 single-level C5-C6 cervical arthroplasty patients (3 males, 4 females; 38-57 years), at least 12 months after surgery (23.6±6.8 months) were included. Patient demographics, preoperative magnetic resonance imaging (MRI)-based measurements of cervical spine degeneration, and 2-year postoperative measurements of dynamic foraminal geometry were the outcome measures. Biplane X-ray images were acquired during axial neck rotation and neck extension. A computed tomography scan was also acquired from C3 to the first thoracic vertebrae. The subaxial cervical vertebrae (C3-C7) were reconstructed into three-dimensional (3D) bone models for use with model-based tracking. Foraminal height (FH) was calculated as the 3D distance between the superior point of the inferior pedicle and the inferior point of the superior pedicle using custom software. Foraminal width (FW) was similarly calculated as the 3D distance between the anterolateral aspect of the superior vertebral body inferior notch and the posterolateral aspect of the inferior vertebral body superior notch. Dynamic foraminal dimensions were quantified as the minimum (FH.Min, FW.Min), the range (FH.Range, FW.Range), and the median (FH.Med, FW.Med) of each trial and then averaged over trials. Mixed model analysis of variance framework was used to examine the differences between ACDF and AD groups. The initial severity of disc degeneration as determined from preoperative MRI images was introduced as covariates in the models. At the operated level (C5-C6), FH.Med and FH.Range were smaller in ACDF than in AD during axial rotation and neck extension (p<.003 to p<.05). At the superior adjacent level (C4-C5), no significant difference was found. At the inferior adjacent level (C6-C7), FW.Range was greater in ACDF than in AD during axial rotation and extension (p<.05). At the non-adjacent level (C3-C4), FW.Range was greater in ACDF than in AD during extension (p<.008). This study demonstrated decreases in foraminal dimensions and their range for ACDF compared with AD at the operated level. In contrast, it demonstrated increases in the range of foraminal dimensions during motion for ACDF compared with AD at the non-operated segments. Together, these data support the notion that increased mobility at the non-operated segments after ACDF may contribute to a greater risk for adjacent segment degeneration. Because of the significant presence of range variables in the findings, the current data also indicate that a dynamic evaluation is likely more appropriate for evaluation of the differences in foramina between ACDF and AD than a static evaluation. Copyright © 2017 Elsevier Inc. All rights reserved.

Using the U.S. Bureau of the Census CD-ROM Test Disc 2: A Note.

ERIC Educational Resources Information Center

Staninger, Steven W.

1991-01-01

This evaluation of means of accessing data on the U.S. Census Bureau CD-ROM Test Disc 2 describes computer hardware configurations considered in determining the most efficient method of manipulating the data, and mentions software options. Two dBASE configurations are compared, and it is concluded that the 80386 is essential for efficient…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Anne-Christine; Jha, Rahul; Gregory, Ruth, E-mail: acd@damtp.cam.ac.uk, E-mail: r.a.w.gregory@durham.ac.uk, E-mail: r.jha@damtp.cam.ac.uk

We present a novel way to investigate scalar field profiles around black holes with an accretion disc for a range of models where the Compton wavelength of the scalar is large compared to other length scales. By analysing the problem in ''Weyl' coordinates, we are able to calculate the scalar profiles for accretion discs in the static Schwarzschild, as well as rotating Kerr, black holes. We comment on observational effects.

Planet-disc interactions with Discontinuous Galerkin Methods using GPUs

NASA Astrophysics Data System (ADS)

Velasco Romero, David A.; Veiga, Maria Han; Teyssier, Romain; Masset, Frédéric S.

2018-05-01

We present a two-dimensional Cartesian code based on high order discontinuous Galerkin methods, implemented to run in parallel over multiple GPUs. A simple planet-disc setup is used to compare the behaviour of our code against the behaviour found using the FARGO3D code with a polar mesh. We make use of the time dependence of the torque exerted by the disc on the planet as a mean to quantify the numerical viscosity of the code. We find that the numerical viscosity of the Keplerian flow can be as low as a few 10-8r2Ω, r and Ω being respectively the local orbital radius and frequency, for fifth order schemes and resolution of ˜10-2r. Although for a single disc problem a solution of low numerical viscosity can be obtained at lower computational cost with FARGO3D (which is nearly an order of magnitude faster than a fifth order method), discontinuous Galerkin methods appear promising to obtain solutions of low numerical viscosity in more complex situations where the flow cannot be captured on a polar or spherical mesh concentric with the disc.

The origin of the LMC stellar bar: clues from the SFH of the bar and inner disc

NASA Astrophysics Data System (ADS)

Monteagudo, L.; Gallart, C.; Monelli, M.; Bernard, E. J.; Stetson, P. B.

2018-01-01

We discuss the origin of the Large Magellanic Cloud (LMC) stellar bar by comparing the star formation histories (SFHs) obtained from deep colour-magnitude diagrams (CMDs) in the bar and in a number of fields in different directions within the inner disc. The CMDs, reaching the oldest main-sequence turn-offs in these very crowded fields, have been obtained with VIMOS on the Very Large Telescope in the service mode, under very good seeing conditions. We show that the SFHs of all fields share the same patterns, with consistent variations of the star formation rate as a function of time in all of them. We therefore conclude that no specific event of star formation can be identified with the formation of the LMC bar, which instead likely formed from a redistribution of disc material which occurred when the LMC disc became bar unstable, and shared a common SFH with the inner disc thereafter. The strong similarity between the SFH of the centre and edge of the bar rules out the expected significant spatial variations of the SFH across the bar.

Observational constraints on disc galaxy formation

NASA Astrophysics Data System (ADS)

Syer, D.; Mao, Shude; Mo, H. J.

1999-04-01

We use data from the literature to constrain theoretical models of galaxy formation. We show how to calculate the dimensionless spin parameter lambda of the haloes of disc galaxies, and we compare the distribution of lambda with that observed in cosmological N-body simulations. The agreement is excellent, which provides strong support for the hierarchical picture of galaxy formation. Assuming only that the radial surface density distribution of discs is exponential, we estimate crudely the maximum-disc mass-to-light ratio in the I band, and obtain < Upsilon_I> <~ 3.56 h, for a Hubble constant of 100 h km s^-1 Mpc^-1. We discuss this result and its limitations in relation to other independent determinations of Upsilon_I. We also define a dimensionless form of the Tully-Fisher relation, and use it to derive a value of the baryon fraction in disc galaxies; the median value is m_d = 0.084 (Upsilon_I3.56 h). Assuming that the gas fraction in galactic haloes is at most as large as that in clusters, we also conclude that < Upsilon_I> <~ 2.56 h^-1/2.

Global stability of self-gravitating discs in modified gravity

NASA Astrophysics Data System (ADS)

Ghafourian, Neda; Roshan, Mahmood

2017-07-01

Using N-body simulations, we study the global stability of a self-gravitating disc in the context of modified gravity (MOG). This theory is a relativistic scalar-tensor-vector theory of gravity and it is presented to address the dark matter problem. In the weak field limit, MOG possesses two free parameters α and μ0, which have already been determined using the rotation curve data of spiral galaxies. The evolution of a stellar self-gravitating disc and, more specifically, the bar instability in MOG are investigated and compared to a Newtonian case. Our models have exponential and Mestel-like surface densities as Σ ∝ exp (-r/h) and Σ ∝ 1/r. It is found that, surprisingly, the discs are more stable against the bar mode in MOG than in Newtonian gravity. In other words, the bar growth rate is effectively slower than the Newtonian discs. Also, we show that both free parameters (I.e. α and μ0) have stabilizing effects. In other words, an increase in these parameters will decrease the bar growth rate.

Quantitative in vivo MRI evaluation of lumbar facet joints and intervertebral discs using axial T2 mapping.

PubMed

Stelzeneder, David; Messner, Alina; Vlychou, Marianna; Welsch, Goetz H; Scheurecker, Georg; Goed, Sabine; Pieber, Karin; Pflueger, Verena; Friedrich, Klaus M; Trattnig, Siegfried

2011-11-01

To assess the feasibility of T2 mapping of lumbar facet joints and intervertebral discs in a single imaging slab and to compare the findings with morphological grading. Sixty lumbar spine segments from 10 low back pain patients and 5 healthy volunteers were examined by axial T2 mapping and morphological MRI at 3.0 Tesla. Regions of interest were drawn on a single slice for the facet joints and the intervertebral discs (nucleus pulposus, anterior and posterior annulus fibrosus). The Weishaupt grading was used for facet joints and the Pfirrmann score was used for morphological disc grading ("normal" vs. "abnormal" discs). The inter-rater agreement was excellent for the facet joint T2 evaluation (r = 0.85), but poor for the morphological Weishaupt grading (kappa = 0.15). The preliminary results show similar facet joint T2 values in segments with normal and abnormal Pfirrmann scores. There was no difference in mean T2 values between facet joints in different Weishaupt grading groups. Facet joint T2 values showed a weak correlation with T2 values of the posterior annulus (r = 0.32) This study demonstrates the feasibility of a combined T2 mapping approach for the facet joints and intervertebral discs using a single axial slab.

A study of accretion discs around rapidly rotating neutron stars in general relativity and its applications to four low mass X-ray binaries

NASA Astrophysics Data System (ADS)

Bhattacharyya, Sudip

2002-02-01

We calculate the accretion disc temperature profiles, disc luminosities and boundary layer luminosities for rapidly rotating neutron stars considering the full effect of general relativity. We compare the theoretical values of these quantities with their values inferred from EXOSAT data for four low mass X-ray binary sources: XB 1820-30, GX 17+2, GX 9+1 and GX 349+2 and constrain the values of several properties of these sources. According to our calculations, the neutron stars in GX 9+1 and GX 349+2 are rapidly rotating and stiffer equations of state are unfavoured.

Transient events in bright debris discs: Collisional avalanches revisited

NASA Astrophysics Data System (ADS)

Thebault, P.; Kral, Q.

2018-01-01

Context. A collisional avalanche is set off by the breakup of a large planetesimal, releasing vast amounts of small unbound grains that enter a debris disc located further away from the star, triggering there a collisional chain reaction that could potentially create detectable transient structures. Aims: We investigate this mechanism, using for the first time a fully self-consistent code coupling dynamical and collisional evolutions. We also quantify for the first time the photometric evolution of the system and investigate whether or not avalanches could explain the short-term luminosity variations recently observed in some extremely bright debris discs. Methods: We use the state-of-the-art LIDT-DD code. We consider an avalanche-favoring A6V star, and two set-ups: a "cold disc" case, with a dust release at 10 au and an outer disc extending from 50 to 120 au, and a "warm disc" case with the release at 1 au and a 5-12 au outer disc. We explore, in addition, two key parameters: the density (parameterized by its optical depth τ) of the main outer disc and the amount of dust released by the initial breakup. Results: We find that avalanches could leave detectable structures on resolved images, for both "cold" and "warm" disc cases, in discs with τ of a few 10-3, provided that large dust masses (≳1020-5 × 1022 g) are initially released. The integrated photometric excess due to an avalanche is relatively limited, less than 10% for these released dust masses, peaking in the λ 10-20 μm domain and becoming insignificant beyond 40-50 μm. Contrary to earlier studies, we do not obtain stronger avalanches when increasing τ to higher values. Likewise, we do not observe a significant luminosity deficit, as compared to the pre-avalanche level, after the passage of the avalanche. These two results concur to make avalanches an unlikely explanation for the sharp luminosity drops observed in some extremely bright debris discs. The ideal configuration for observing an avalanche would be a two-belt structure, with an inner belt (at 1 or 10 au for the "warm" and "cold" disc cases, respectively) of fractional luminosity f ≳ 10-4 where breakups of massive planetesimals occur, and a more massive outer belt, with τ of a few 10-3, into which the avalanche chain reaction develops and propagates.

The dynamics of stellar discs in live dark-matter haloes

NASA Astrophysics Data System (ADS)

Fujii, M. S.; Bédorf, J.; Baba, J.; Portegies Zwart, S.

2018-06-01

Recent developments in computer hardware and software enable researchers to simulate the self-gravitating evolution of galaxies at a resolution comparable to the actual number of stars. Here we present the results of a series of such simulations. We performed N-body simulations of disc galaxies with between 100 and 500 million particles over a wide range of initial conditions. Our calculations include a live bulge, disc, and dark-matter halo, each of which is represented by self-gravitating particles in the N-body code. The simulations are performed using the gravitational N-body tree-code BONSAI running on the Piz Daint supercomputer. We find that the time-scale over which the bar forms increases exponentially with decreasing disc-mass fraction and that the bar formation epoch exceeds a Hubble time when the disc-mass fraction is ˜0.35. These results can be explained with the swing-amplification theory. The condition for the formation of m = 2 spirals is consistent with that for the formation of the bar, which is also an m = 2 phenomenon. We further argue that the non-barred grand-design spiral galaxies are transitional, and that they evolve to barred galaxies on a dynamical time-scale. We also confirm that the disc-mass fraction and shear rate are important parameters for the morphology of disc galaxies. The former affects the number of spiral arms and the bar formation epoch, and the latter determines the pitch angle of the spiral arms.

A Small Disc Area Is a Risk Factor for Visual Field Loss Progression in Primary Open-Angle Glaucoma: The Glaucoma Stereo Analysis Study.

PubMed

Kitaoka, Yasushi; Tanito, Masaki; Yokoyama, Yu; Nitta, Koji; Katai, Maki; Omodaka, Kazuko; Nakazawa, Toru

2018-01-01

The Glaucoma Stereo Analysis Study, a cross-sectional multicenter collaborative study, used a stereo fundus camera (nonmyd WX) to assess various morphological parameters of the optic nerve head (ONH) in glaucoma patients. We compared the associations of each parameter between the visual field loss progression group and no-progression group. The study included 187 eyes of 187 patients with primary open-angle glaucoma or normal-tension glaucoma. We divided the mean deviation (MD) slope values of all patients into the progression group (<-0.3 dB/year) and no-progression group (≧-0.3 dB/year). ONH morphological parameters were calculated with prototype analysis software. The correlations between glaucomatous visual field progression and patient characteristics or each ONH parameter were analyzed with Spearman's rank correlation coefficient. The MD slope averages in the progression group and no-progression group were -0.58 ± 0.28 dB/year and 0.05 ± 0.26 dB/year, respectively. Among disc parameters, vertical disc width (diameter), disc area, cup area, and cup volume in the progression group were significantly less than those in the no-progression group. Logistic regression analysis revealed a significant association between the visual field progression and disc area (odds ratio 0.49/mm 2 disc area). A smaller disc area may be associated with more rapid glaucomatous visual field progression.

How important is non-ideal physics in simulations of sub-Eddington accretion on to spinning black holes?

NASA Astrophysics Data System (ADS)

Foucart, Francois; Chandra, Mani; Gammie, Charles F.; Quataert, Eliot; Tchekhovskoy, Alexander

2017-09-01

Black holes with accretion rates well below the Eddington rate are expected to be surrounded by low-density, hot, geometrically thick accretion discs. This includes the two black holes being imaged at subhorizon resolution by the Event Horizon Telescope. In these discs, the mean free path for Coulomb interactions between charged particles is large, and the accreting matter is a nearly collisionless plasma. Despite this, numerical simulations have so far modelled these accretion flows using ideal magnetohydrodynamics. Here, we present the first global, general relativistic, 3D simulations of accretion flows on to a Kerr black hole including the non-ideal effects most likely to affect the dynamics of the disc: the anisotropy between the pressure parallel and perpendicular to the magnetic field, and the heat flux along magnetic field lines. We show that for both standard and magnetically arrested discs, the pressure anisotropy is comparable to the magnetic pressure, while the heat flux remains dynamically unimportant. Despite this large pressure anisotropy, however, the time-averaged structure of the accretion flow is strikingly similar to that found in simulations treating the plasma as an ideal fluid. We argue that these similarities are largely due to the interchangeability of the viscous and magnetic shear stresses as long as the magnetic pressure is small compared to the gas pressure, and to the subdominant role of pressure/viscous effects in magnetically arrested discs. We conclude by highlighting outstanding questions in modelling the dynamics of low-collisionality accretion flows.

Analysis of optic disc change using the heidelberg retina tomograph in an acquired pit of the optic nerve.

PubMed

Oh, Joo Youn; Park, Ki Ho

2004-01-01

A 51-year-old woman diagnosed as having normal-tension glaucoma developed an acquired pit of the optic nerve. The optic disc was viewed by the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) before and after development of an acquired pit of the optic nerve. HRT parameters and cross-sectional images of the optic disc were compared. Maximum cup depth at the site of the acquired pit of the optic nerve increased after development of the acquired pit of the optic nerve (from 1.200 to 2.432 mm). The neuroretinal rim area and volume in the inferotemporal octant were reduced (rim area from 0.070 to 0.010 mm2, rim volume from 0.009 to 0.001 mm3). The morphologic changes in the optic disc were also detected topographically and reflectively.

Refining the application of direct embryogenesis in sugarcane: Effect of the developmental phase of leaf disc explants and the timing of DNA transfer on transformation efficiency.

PubMed

Snyman, S J; Meyer, G M; Richards, J M; Haricharan, N; Ramgareeb, S; Huckett, B I

2006-10-01

A rapid in vitro protocol using direct somatic embryogenesis and microprojectile bombardment was investigated to establish the developmental phases most suitable for efficient sugarcane transformation. Immature leaf roll disc explants with and without pre-emergent inflorescence tissue were compared. It was shown that for effective transformation to occur, explants should be cultured for several days to allow initiation of embryo development prior to bombardment. Leaf roll discs with pre-emergent inflorescences showed a higher degree of embryogenic competence than non-flowering explants, and transformation efficiency was higher when explants containing floral initials were bombarded. Despite the occurrence of high numbers of phenotypically negative plants, combining the use of inflorescent leaf roll discs with direct embryogenic regeneration has the potential to improve the speed and efficiency of transgenesis in sugarcane.

Bone loss of vertebral bodies at the operative segment after cervical arthroplasty: a potential complication?

PubMed

Heo, Dong Hwa; Lee, Dong Chan; Oh, Jong Yang; Park, Choon Keun

2017-02-01

OBJECTIVE Bony overgrowth and spontaneous fusion are complications of cervical arthroplasty. In contrast, bone loss or bone remodeling of vertebral bodies at the operation segment after cervical arthroplasty has also been observed. The purpose of this study is to investigate a potential complication-bone loss of the anterior portion of the vertebral bodies at the surgically treated segment after cervical total disc replacement (TDR)-and discuss the clinical significance. METHODS All enrolled patients underwent follow-up for more than 24 months after cervical arthroplasty using the Baguera C disc. Clinical evaluations included recording demographic data and measuring the visual analog scale and Neck Disability Index scores. Radiographic evaluations included measurements of the functional spinal unit's range of motion and changes such as bone loss and bone remodeling. The grading of the bone loss of the operative segment was classified as follows: Grade 1, disappearance of the anterior osteophyte or small minor bone loss; Grade 2, bone loss of the anterior portion of the vertebral bodies at the operation segment without exposure of the artificial disc; or Grade 3, significant bone loss with exposure of the anterior portion of the artificial disc. RESULTS Forty-eight patients were enrolled in this study. Among them, bone loss developed in 29 patients (Grade 1 in 15 patients, Grade 2 in 6 patients, and Grade 3 in 8 patients). Grade 3 bone loss was significantly associated with postoperative neck pain (p < 0.05). Bone loss was related to the motion preservation effect of the operative segment after cervical arthroplasty in contrast to heterotopic ossification. CONCLUSIONS Bone loss may be a potential complication of cervical TDR and affect early postoperative neck pain. However, it did not affect mid- to long-term clinical outcomes or prosthetic failure at the last follow-up. Also, this phenomenon may result in the motion preservation effect in the operative segment after cervical TDR.

Nearby stars of the Galactic disc and halo - IV

NASA Astrophysics Data System (ADS)

Fuhrmann, Klaus

2008-02-01

The Milky Way Galaxy has an age of about 13 billion years. Solar-type stars evolve all the long way to the realm of degenerate objects on essentially this time-scale. This, as well as the particular advantage that the Sun offers through reliable differential spectroscopic analyses, render these stars the ideal tracers for the fossil record of our parent spiral. Astrophysics is a science that is known to be notoriously plagued by selection effects. The present work - with a major focus in this fourth contribution on model atmosphere analyses of spectroscopic binaries and multiple star systems - aims at a volume-complete sample of about 300 nearby F-, G-, and K-type stars that particularly avoids any kinematical or chemical pre-selection from the outset. It thereby provides an unbiased record of the local stellar populations - the ancient thick disc and the much younger thin disc. On this base, the detailed individual scrutiny of the long-lived stars of both populations unveils the thick disc as a single-burst component with a local normalization of no less than 20 per cent. This enormous fraction, combined with its much larger scaleheight, implies a mass for the thick disc that is comparable to that of the thin disc. On account of its completely different mass-to-light ratio the thick disc thereby becomes the dark side of the Milky Way, an ideal major source for baryonic dark matter. This massive, ancient population consequently challenges any gradual build-up scenario for our parent spiral. Even more, on the supposition that the Galaxy is not unusual, the thick disc - as it emerges from this unbiased spectroscopic work - particularly challenges the hierarchical cold-dark-matter-dominated formation picture for spiral galaxies in general.

Sensibility testing in patients with a lumbosacral radicular syndrome.

PubMed

Peeters, G G; Aufdemkampe, G; Oostendorp, R A

1998-02-01

To examine whether there is a significant difference in gnostic sensibility between affected and unaffected legs of patients suffering from lumbosacral radicular syndrome (LRS) resulting from a disc herniation and to determine the validity of the sensibility test for detecting a disc herniation. Observer blind study of sensibility testing. Four general hospitals (neurology department) and one practice of physical and manual therapy. Fifty-one patients with radicular pain in the lumbosacral nerve roots for at least 4 wk and/or neurological deficits. The gnostic sensibility of 51 patients with a unilateral LRS was tested using Semmes-Weinstein monofilaments for the L4, L5 and S1 dermatomes. Gnostic hypoesthetic impairments in the L4, L5 and S1 dermatomes were found in 84.6% of the 43 patients in which the presence of disc herniation was confirmed by CT. There was significant difference in gnostic sensibility between the affected and unaffected legs in the L4, L5, and S1 dermatomes for disc herniation at the L4-L5 level and for the L5 and S1 dermatomes for a disc herniation at the L5-S1 level. There was no significant difference in gnostic sensibility in the L4 dermatome for a disc herniation at the L5-S1 level. The gnostic sensibility of the affected leg is hypoesthetic compared with the unaffected leg. The specificity of the sensibility test using monofilaments is acceptable, but the sensitivity is not. The monofilament test is a useful and practical tool for excluding the presence of a disc herniation at dermatomes L4, L5 and S1 and disc herniations at the L4-L5, L5-S1 level.

Semiautomatic computer-aided classification of degenerative lumbar spine disease in magnetic resonance imaging.

PubMed

Ruiz-España, Silvia; Arana, Estanislao; Moratal, David

2015-07-01

Computer-aided diagnosis (CAD) methods for detecting and classifying lumbar spine disease in Magnetic Resonance imaging (MRI) can assist radiologists to perform their decision-making tasks. In this paper, a CAD software has been developed able to classify and quantify spine disease (disc degeneration, herniation and spinal stenosis) in two-dimensional MRI. A set of 52 lumbar discs from 14 patients was used for training and 243 lumbar discs from 53 patients for testing in conventional two-dimensional MRI of the lumbar spine. To classify disc degeneration according to the gold standard, Pfirrmann classification, a method based on the measurement of disc signal intensity and structure was developed. A gradient Vector Flow algorithm was used to extract disc shape features and for detecting contour abnormalities. Also, a signal intensity method was used for segmenting and detecting spinal stenosis. Novel algorithms have also been developed to quantify the severity of these pathologies. Variability was evaluated by kappa (k) and intra-class correlation (ICC) statistics. Segmentation inaccuracy was below 1%. Almost perfect agreement, as measured by the k and ICC statistics, was obtained for all the analyzed pathologies: disc degeneration (k=0.81 with 95% CI=[0.75..0.88]) with a sensitivity of 95.8% and a specificity of 92.6%, disc herniation (k=0.94 with 95% CI=[0.87..1]) with a sensitivity of 60% and a specificity of 87.1%, categorical stenosis (k=0.94 with 95% CI=[0.90..0.98]) and quantitative stenosis (ICC=0.98 with 95% CI=[0.97..0.98]) with a sensitivity of 70% and a specificity of 81.7%. The proposed methods are reproducible and should be considered as a possible alternative when compared to reference standards. Copyright © 2015 Elsevier Ltd. All rights reserved.

The ALMA early science view of FUor/EXor objects - V. Continuum disc masses and sizes

NASA Astrophysics Data System (ADS)

Cieza, Lucas A.; Ruíz-Rodríguez, Dary; Perez, Sebastian; Casassus, Simon; Williams, Jonathan P.; Zurlo, Alice; Principe, David A.; Hales, Antonio; Prieto, Jose L.; Tobin, John J.; Zhu, Zhaohuan; Marino, Sebastian

2018-03-01

Low-mass stars build a significant fraction of their total mass during short outbursts of enhanced accretion known as FUor and EXor outbursts. FUor objects are characterized by a sudden brightening of ˜5 mag at visible wavelengths within 1 yr and remain bright for decades. EXor objects have lower amplitude outbursts on shorter time-scales. Here we discuss a 1.3 mm Atacama Large Millimeter/submillimeter Array (ALMA) mini-survey of eight outbursting sources (three FUors, four EXors, and the borderline object V1647 Ori) in the Orion Molecular Cloud. While previous papers in this series discuss the remarkable molecular outflows observed in the three FUor objects and V1647 Ori, here we focus on the continuum data and the differences and similarities between the FUor and EXor populations. We find that FUor discs are significantly more massive (˜80-600 MJup) than the EXor objects (˜0.5-40 MJup). We also report that the EXor sources lack the prominent outflows seen in the FUor population. Even though our sample is small, the large differences in disc masses and outflow activity suggest that the two types of objects represent different evolutionary stages. The FUor sources seem to be rather compact (Rc < 20-40 au) and to have a smaller characteristic radius for a given disc mass when compared to T Tauri stars. V1118 Ori, the only known close binary system in our sample, is shown to host a disc around each one of the stellar components. The disc around HBC 494 is asymmetric, hinting at a structure in the outer disc or the presence of a second disc.

Novel Bruch's Membrane Opening Minimum Rim Area Equalizes Disc Size Dependency and Offers High Diagnostic Power for Glaucoma.

PubMed

Enders, Philip; Adler, Werner; Schaub, Friederike; Hermann, Manuel M; Dietlein, Thomas; Cursiefen, Claus; Heindl, Ludwig M

2016-12-01

The purpose of this study was to assess the diagnostic power of the novel two-dimensional parameter Bruch's membrane opening minimal rim area (BMO-MRA) in spectral-domain optical coherence tomography (SD-OCT) for detection of glaucoma compared to minimal rim width (BMO-MRW) and retinal nerve fiber layer (RNFL) thickness in large and small optic discs. In this case-control, cross-sectional study, 207 eyes of 207 participants, including 89 controls and 97 patients with glaucoma and 21 with ocular hypertension (OHT), with a disc size <1.63 mm2 or >2.43 mm2 underwent SD-OCT, confocal laser scanning tomography (CSLT), visual field testing, and clinical examination. Bruch's membrane opening-MRA BMO-MRW, RNFL thickness of SD-OCT and disc margin rim area (DM-RA) of CSLT were evaluated and analyzed for diagnostic power to detect glaucoma. In healthy eyes with macrodiscs, mean BMO-MRW of 243.14 ± 43.12 μm was significantly smaller than BMO-MRW in microdiscs (338.97 ± 69.39; P < 0.001). Bruch's membrane opening-MRA was comparable between disc size groups with 1.22 ± 0.25 mm2 for macrodiscs and 1.26 ± 0.27 mm2 for microdiscs (P = 0.51), as was RNFL thickness (82.69 ± 15.76 μm versus 78.53 ± 11.01 μm, respectively; P = 0.28). Perimetric mean deviation was -8.7 ± 6.3 dB in glaucoma and -0.6 ± 1.60 dB in OHT patients. Correlation of BMO-MRA and visual field function was rho (ρ) = 0.70 (P < 0.001). Diagnostic power to differentiate glaucoma patients was highest for BMO-MRA. Partial area under the curve (pAUC) for BMO-MRA was 0.14 for specificity between 0.8 and 1.0, exceeding pAUCs of BMO-MRW (P < 0.001), RNFL thickness (P = 0.03), and DM-RA (P = 0.01). Bruch's membrane opening-based minimum rim area measurements offer advantages compared to one-dimensional parameters assessing neuroretinal rim by SD-OCT. In nonglaucomatous eyes, BMO-MRA values seem comparable for the full range of disc sizes. Bruch's membrane opening-MRA surpasses other parameters in diagnostic power for glaucoma.

The formation of bulges, discs and two-component galaxies in the CANDELS Survey at z < 3

NASA Astrophysics Data System (ADS)

Margalef-Bentabol, Berta; Conselice, Christopher J.; Mortlock, Alice; Hartley, Will; Duncan, Kenneth; Ferguson, Harry C.; Dekel, Avishai; Primack, Joel R.

2016-09-01

We examine a sample of 1495 galaxies in the CANDELS fields to determine the evolution of two-component galaxies, including bulges and discs, within massive galaxies at the epoch 1 < z < 3 when the Hubble sequence forms. We fit all of our galaxies' light profiles with a single Sérsic fit, as well as with a combination of exponential and Sérsic profiles. The latter is done in order to describe a galaxy with an inner and an outer component, or bulge and disc component. We develop and use three classification methods (visual, F-test and the residual flux fraction) to separate our sample into one-component galaxies (disc/spheroids-like galaxies) and two-component galaxies (galaxies formed by an `inner part' or bulge and an `outer part' or disc). We then compare the results from using these three different ways to classify our galaxies. We find that the fraction of galaxies selected as two-component galaxies increases on average 50 per cent from the lowest mass bin to the most massive galaxies, and decreases with redshift by a factor of 4 from z = 1 to 3. We find that single Sérsic `disc-like' galaxies have the highest relative number densities at all redshifts, and that two-component galaxies have the greatest increase and become at par with Sérsic discs by z = 1. We also find that the systems we classify as two-component galaxies have an increase in the sizes of their outer components, or `discs', by about a factor of 3 from z = 3 to 1.5, while the inner components or `bulges' stay roughly the same size. This suggests that these systems are growing from the inside out, whilst the bulges or protobulges are in place early in the history of these galaxies. This is also seen to a lesser degree in the growth of single `disc-like' galaxies versus `spheroid-like' galaxies over the same epoch.

Multidirectional testing of one- and two-level ProDisc-L versus simulated fusions.

PubMed

Panjabi, Manohar; Henderson, Gweneth; Abjornson, Celeste; Yue, James

2007-05-20

An in vitro human cadaveric biomechanical study. To evaluate intervertebral rotation changes due to lumbar ProDisc-L compared with simulated fusion, using follower load and multidirectional testing. Artificial discs, as opposed to the fusions, are thought to decrease the long-term accelerated degeneration at adjacent levels. A biomechanical assessment can be helpful, as the long-term clinical evaluation is impractical. Six fresh human cadaveric lumbar specimens (T12-S1) underwent multidirectional testing in flexion-extension, bilateral lateral bending, and bilateral torsion using the Hybrid test method. First, intact specimen total range of rotation (T12-S1) was determined. Second, using pure moments again, this range of rotation was achieved in each of the 5 constructs: A) ProDisc-L at L5-S1; B) fusion at L5-S1; C) ProDisc-L at L4-L5 and fusion at L5-S1; D) ProDisc-L at L4-L5 and L5-S1; and E) 2-level fusion at L4-L5 to L5-S1. Significant changes in the intervertebral rotations due to each construct were determined at the operated and nonoperated levels using repeated measures single factor ANOVA and Bonferroni statistical tests (P < 0.05). Adjacent-level effects (ALEs) were defined as the percentage changes in intervertebral rotations at the nonoperated levels due to the constructs. One- and 2-level ProDisc-L constructs showed only small ALE in any of the 3 rotations. In contrast, 1- and 2-level fusions showed increased ALE in all 3 directions (average, 7.8% and 35.3%, respectively, for 1 and 2 levels). In the disc plus fusion combination (construct C), the ALEs were similar to the 1-level fusion alone. In general, ProDisc-L preserved physiologic motions at all spinal levels, while the fusion simulations resulted in significant ALE.

Hybrid testing of lumbar CHARITE discs versus fusions.

PubMed

Panjabi, Manohar; Malcolmson, George; Teng, Edward; Tominaga, Yasuhiro; Henderson, Gweneth; Serhan, Hassan

2007-04-20

An in vitro human cadaveric biomechanical study. To quantify effects on operated and other levels, including adjacent levels, due to CHARITE disc implantations versus simulated fusions, using follower load and the new hybrid test method in flexion-extension and bilateral torsion. Spinal fusion has been associated with long-term accelerated degeneration at adjacent levels. As opposed to the fusion, artificial discs are designed to preserve motion and diminish the adjacent-level effects. Five fresh human cadaveric lumbar specimens (T12-S1) underwent multidirectional testing in flexion-extension and bilateral torsion with 400 N follower load. Intact specimen total ranges of motion were determined with +/-10 Nm unconstrained pure moments. The intact range of motion was used as input for the hybrid tests of 5 constructs: 1) CHARITE disc at L5-S1; 2) fusion at L5-S1; 3) CHARITE discs at L4-L5 and L5-S1; 4) CHARITE disc at L4-L5 and fusion at L5-S1; and 5) 2-level fusion at L4-L5-S1. Using repeated-measures single factor analysis of variance and Bonferroni statistical tests (P < 0.05), intervertebral motion redistribution of each construct was compared with the intact. In flexion-extension, 1-level CHARITE disc preserved motion at the operated and other levels, while 2-level CHARITE showed some amount of other-level effects. In contrast, 1- and 2-level fusions increased other-level motions (average, 21.0% and 61.9%, respectively). In torsion, both 1- and 2-level discs preserved motions at all levels. The 2-level simulated fusion increased motions at proximal levels (22.9%), while the 1-level fusion produced no significant changes. In general, CHARITE discs preserved operated- and other-level motions. Fusion simulations affected motion redistribution at other levels, including adjacent levels.

Oblique Sagittal Images Prevent Underestimation of the Neuroforaminal Stenosis Grade Caused by Disc Herniation in Cervical Spine MRI.

PubMed

Kintzelé, Laurent; Rehnitz, Christoph; Kauczor, Hans-Ulrich; Weber, Marc-André

2018-06-06

 To identify whether standard sagittal MRI images result in underestimation of the neuroforaminal stenosis grade compared to oblique sagittal MRI images in patients with cervical spine disc herniation.  74 patients with a total of 104 cervical disc herniations compromising the corresponding nerve root were evaluated. Neuroforaminal stenosis grades were evaluated in standard and oblique sagittal images by one senior and one resident radiologist experienced in musculoskeletal imaging. Oblique images were angled 30° towards the standard sagittal plane. Neuroforaminal stenosis grades were classified from 0 (no stenosis) to 3 (high grade stenosis).  Average neuroforaminal stenosis grades of both readers were significantly lower in standard compared to oblique sagittal images (p < 0.001). For 47.1 % of the cases, one or both readers reported a stenosis grade, which was at least 1 grade lower in standard compared to oblique sagittal images. There was also a significant difference when looking at patients who had neurological symptoms (p = 0.002) or underwent cervical spine surgery subsequently (p = 0.004). Interreader reliability, as measured by kappa value, and accordance rates were better for oblique sagittal images (0.94 vs. 0.88 and 99 % vs. 93 %).  Standard sagittal images tend to underestimate neuroforaminal stenosis grades compared to oblique sagittal images and are less reliable in the evaluation of disc herniations within the cervical spine MRI. In order to assess the potential therapeutic consequence, oblique images should therefore be considered as a valuable adjunct to the standard MRI protocol for patients with a radiculopathy.   · Neuroforaminal stenosis grades are underestimated in standard compared to oblique sagittal images. · Interreader reliability is higher for oblique sagittal images. · Oblique sagittal images should be performed in patients with a cervical radiculopathy. · Kintzele L, Rehnitz C, Kauczor H et al. Oblique Sagittal Images Prevent Underestimation of the Neuroforaminal Stenosis Grade Caused by Disc Herniation in Cervical Spine MRI. Fortschr Röntgenstr 2018; DOI: 10.1055/a-0612-8205. © Georg Thieme Verlag KG Stuttgart · New York.

Quantitative T2 evaluation at 3.0T compared to morphological grading of the lumbar intervertebral disc: a standardized evaluation approach in patients with low back pain.

PubMed

Stelzeneder, David; Welsch, Goetz Hannes; Kovács, Balázs Krisztián; Goed, Sabine; Paternostro-Sluga, Tatjana; Vlychou, Marianna; Friedrich, Klaus; Mamisch, Tallal Charles; Trattnig, Siegfried

2012-02-01

The purpose of our investigation was to compare quantitative T2 relaxation time measurement evaluation of lumbar intervertebral discs with morphological grading in young to middle-aged patients with low back pain, using a standardized region-of-interest evaluation approach. Three hundred thirty lumbar discs from 66 patients (mean age, 39 years) with low back pain were examined on a 3.0T MR unit. Sagittal T1-FSE, sagittal, coronal, and axial T2-weighted FSE for morphological MRI, as well as a multi-echo spin-echo sequence for T2 mapping, were performed. Morphologically, all discs were classified according to Pfirrmann et al. Equally sized rectangular regions of interest (ROIs) for the annulus fibrosus were selected anteriorly and posteriorly in the outermost 20% of the disc. The space between was defined as the nucleus pulposus. To assess the reproducibility of this evaluation, inter- and intraobserver statistics were performed. The Pfirrmann scoring of 330 discs showed the following results: grade I: six discs (1.8%); grade II: 189 (57.3%); grade III: 96 (29.1%); grade IV: 38 (11.5%); and grade V: one (0.3%). The mean T2 values (in milliseconds) for the anterior and the posterior annulus, and the nucleus pulposus for the respective Pfirrmann groups were: I: 57/30/239; II: 44/67/129; III: 42/51/82; and IV: 42/44/56. The nucleus pulposus T2 values showed a stepwise decrease from Pfirrmann grade I to IV. The posterior annulus showed the highest T2 values in Pfirrmann group II, while the anterior annulus showed relatively constant T2 values in all Pfirrmann groups. The inter- and intraobserver analysis yielded intraclass correlation coefficients (ICC) for average measures in a range from 0.82 (anterior annulus) to 0.99 (nucleus). Our standardized method of region-specific quantitative T2 relaxation time evaluation seems to be able to characterize different degrees of disc degeneration quantitatively. The reproducibility of our ROI measurements is sufficient to encourage the use of this method in future investigations, particularly for longitudinal studies. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Does postmenopausal hormone replacement therapy affect intraocular pressure?

PubMed

Abramov, Yoram; Borik, Sharon; Yahalom, Claudia; Fatum, Muhammad; Avgil, Gadiel; Brzezinski, Amnon; Banin, Eyal

2005-08-01

To assess the effects of postmenopausal hormone replacement therapy (HRT) on intraocular pressure (IOP). This was a cross-sectional controlled study, including 107 women aged 60 to 80 years receiving HRT and 107 controls who have never received HRT. All subjects underwent IOP assessment and funduscopic photography for cup-to-disc (C/D) ratios, and completed questionnaires regarding personal and family history of glaucoma, hormone replacement therapy, lifetime estrogen and progesterone exposure, and cardiovascular risk factors. Main Outcome Measures included IOP, prevalence of increased IOP, and C/D ratios. The groups did not differ in mean IOP (15.3 versus 15.3 mm Hg), mean vertical (0.18 versus 0.21) and horizontal (0.17 versus 0.14) C/D ratios, and in prevalence of increased IOP (15% versus 14%), C/D ratio (7% versus 7%), or glaucoma (9% versus 11%). A personal history of ischemic heart disease was the only risk factor associated with increased IOP (O.R. = 4.63, P = 0.003). Lifetime estrogen and progesterone exposure, including pregnancies, deliveries, menstruation years, and the use of oral contraceptives did not significantly affect the risk for increased IOP. Hormone replacement therapy and lifetime estrogen and progesterone exposure do not seem to affect IOP or the risk for increased IOP. A personal history of ischemic heart disease may be associated with a higher risk for this disorder.

Longitudinal analysis of progression in glaucoma using spectral-domain optical coherence tomography.

PubMed

Wessel, Julia M; Horn, Folkert K; Tornow, Ralf P; Schmid, Matthias; Mardin, Christian Y; Kruse, Friedrich E; Juenemann, Anselm G; Laemmer, Robert

2013-05-01

To compare the longitudinal loss of RNFL thickness measurements by SD-OCT in healthy individuals and glaucoma patients with or without progression concerning optic disc morphology. A total of 62 eyes, comprising 38 glaucomatous eyes with open angle glaucoma and 24 healthy controls, were included in the study (Erlangen Glaucoma Registry, NTC00494923). All patients were investigated annually over a period of 3 years by Spectralis SD-OCT measuring peripapillary RNFL thickness. By masked comparative analysis of photographs, the eyes were classified into nonprogressive and progressive glaucoma cases. Longitudinal loss of RNFL thickness was compared with morphological changes of optic disc morphology. Mixed model analysis of annual OCT scans revealed an estimated annual decrease of the RNFL thickness by 2.12 μm in glaucoma eyes with progression, whereas glaucoma eyes without progression in optic disc morphology lost 1.18 μm per year in RNFL thickness (P = 0.002). The rate of change in healthy eyes was 0.60 μm and thereby also significantly lower than in glaucoma eyes with progression (P < 0.001). The intrasession variability of three successive measurements without head repositioning was 1.5 ± 0.7 μm. The loss of mean RNFL thickness exceeded the intrasession variability in 60% of nonprogressive eyes, and in 85% of progressive eyes after 3 years. LONGITUDINAL MEASUREMENTS OF RNFL THICKNESS USING SD-OCT SHOW A MORE PRONOUNCED REDUCTION OF RNFL THICKNESS IN PATIENTS WITH PROGRESSION COMPARED WITH PATIENTS WITHOUT PROGRESSION IN GLAUCOMATOUS OPTIC DISC CHANGES. (www.clinicaltrials.gov number, NTC00494923.).

Effect of feed grinding methods with and without expansion on prececal and total tract mineral digestibility as well as on interior and exterior egg quality in laying hens.

PubMed

Hafeez, A; Mader, A; Ruhnke, I; Männer, K; Zentek, J

2016-01-01

The grinding of cereals by various milling methods as well as thermal treatment of feed may influence mineral digestibility and egg quality. The present study investigated the effect of feed produced by disc mill (D) and wedge-shaped disc mill (WSD), as mash (M) or expandate (E) on apparent ileal absorption (AIA) and apparent total digestibility (ATD) of calcium, phosphorus, magnesium, zinc, manganese, copper and iron, as well as on egg quality in laying hens. A total of 192 hens (Lohmann Brown) aged 19 wk, were assigned using a randomized design with a 2 × 2 factorial arrangement. Four experimental diets were offered ad libitum. Eggs were analyzed for weight, shape index, area, shell weight per unit surface area, yolk color, air cell, blood spot, Haugh unit, albumen and yolk measures (index, weight, height, width and length), shell measures (surface area, stability, density, thickness and membrane weight), as well as percent contents of albumen, yolk, shell, and shell membrane. The ATD for phosphorus, manganese, and copper was higher in WSD compared with D treatment (P = 0.028, P = 0.028 and P = 0.016, respectively). The interaction between milling methods and thermal treatment influenced ATD of copper (P = 0.033), which was higher in WSD+M group (41.0 ± 20.2) compared with D+E group (-3.21 ± 25.1), whereas no differences were observed for D+M (1.90 ± 37.8) and WSD+E (8.02 ± 36.2) groups. Egg stability tended to be higher in E compared with M treatment (P = 0.055). Albumen weight, percentage albumen weight, and albumen: yolk were higher and percentage yolk weight was lower in D compared with WSD treatment (P = 0.043, P = 0.027, P = 0.024, and P = 0.041, respectively). Number of blood spots was higher in E than M treatment (P = 0.053). In conclusion, use of a wedge-shaped disc mill resulted in higher ATD for phosphorus, manganese, and copper than use of a disc mill; however, digestibility for majority of minerals as well as egg quality parameters was comparable. Therefore, feed produced by either disc mill or wedge-shaped disc mill as mash or expandate may be used for laying hens without negative effects on egg quality. © 2015 Poultry Science Association Inc.

Ganglion cell-inner plexiform layer and retinal nerve fiber layer thickness according to myopia and optic disc area: a quantitative and three-dimensional analysis.

PubMed

Seo, Sam; Lee, Chong Eun; Jeong, Jae Hoon; Park, Ki Ho; Kim, Dong Myung; Jeoung, Jin Wook

2017-03-11

To determine the influences of myopia and optic disc size on ganglion cell-inner plexiform layer (GCIPL) and peripapillary retinal nerve fiber layer (RNFL) thickness profiles obtained by spectral domain optical coherence tomography (OCT). One hundred and sixty-eight eyes of 168 young myopic subjects were recruited and assigned to one of three groups according to their spherical equivalent (SE) values and optic disc area. All underwent Cirrus HD-OCT imaging. The influences of myopia and optic disc size on the GCIPL and RNFL thickness profiles were evaluated by multiple comparisons and linear regression analysis. Three-dimensional surface plots of GCIPL and RNFL thickness corresponding to different combinations of myopia and optic disc size were constructed. Each of the quadrant RNFL thicknesses and their overall average were significantly thinner in high myopia compared to low myopia, except for the temporal quadrant (all Ps ≤0.003). The average and all-sectors GCIPL were significantly thinner in high myopia than in moderate- and/or low-myopia (all Ps ≤0.002). The average OCT RNFL thickness was correlated significantly with SE (0.81 μm/diopter, P < 0.001), axial length (-1.44 μm/mm, P < 0.001), and optic disc area (5.35 μm/mm 2 , P < 0.001) by linear regression analysis. As for the OCT GCIPL parameters, average GCIPL thickness showed a significant correlation with SE (0.84 μm/diopter, P < 0.001) and axial length (-1.65 μm/mm, P < 0.001). There was no significant correlation of average GCIPL thickness with optic disc area. Three-dimensional curves showed that larger optic discs were associated with increased average RNFL thickness and that more-myopic eyes were associated with decreased average GCIPL and RNFL thickness. Myopia can significantly affect GCIPL and RNFL thickness profiles, and optic disc size has a significant influence on RNFL thickness. The current OCT maps employed in the evaluation of glaucoma should be analyzed in consideration of refractive status and optic disc size.

Circumbinary discs: Numerical and physical behaviour

NASA Astrophysics Data System (ADS)

Thun, Daniel; Kley, Wilhelm; Picogna, Giovanni

2017-08-01

Aims: Discs around a central binary system play an important role in star and planet formation and in the evolution of galactic discs. These circumbinary discs are strongly disturbed by the time varying potential of the binary system and display a complex dynamical evolution that is not well understood. Our goal is to investigate the impact of disc and binary parameters on the dynamical aspects of the disc. Methods: We study the evolution of circumbinary discs under the gravitational influence of the binary using two-dimensional hydrodynamical simulations. To distinguish between physical and numerical effects we apply three hydrodynamical codes. First we analyse in detail numerical issues concerning the conditions at the boundaries and grid resolution. We then perform a series of simulations with different binary parameters (eccentricity, mass ratio) and disc parameters (viscosity, aspect ratio) starting from a reference model with Kepler-16 parameters. Results: Concerning the numerical aspects we find that the length of the inner grid radius and the binary semi-major axis must be comparable, with free outflow conditions applied such that mass can flow onto the central binary. A closed inner boundary leads to unstable evolutions. We find that the inner disc turns eccentric and precesses for all investigated physical parameters. The precession rate is slow with periods (Tprec) starting at around 500 binary orbits (Tbin) for high viscosity and a high aspect ratio H/R where the inner hole is smaller and more circular. Reducing α and H/R increases the gap size and Tprec reaches 2500 Tbin. For varying binary mass ratios qbin the gap size remains constant, whereas Tprec decreases with increasing qbin. For varying binary eccentricities ebin we find two separate branches in the gap size and eccentricity diagram. The bifurcation occurs at around ecrit ≈ 0.18 where the gap is smallest with the shortest Tprec. For ebin lower and higher than ecrit, the gap size and Tprec increase. Circular binaries create the most eccentric discs. Movies associated to Figs. 1 and 8 are available at http://www.aanda.org

Aedes aegypti (Diptera: Culicidae): evaluation of natural long-lasting materials containing pyriproxyfen to improve control strategies.

PubMed

Seccacini, Emilia; Juan, Laura; Zerba, Eduardo; Licastro, Susana

2014-09-01

Natural materials such as beeswax or a paraffin/stearin mixture containing pyriproxyfen and used as a slow release formulation may convert any breeding place into a larvicidal ovitrap for Aedes aegypti (L.) control. Effectiveness and residual activity of beeswax and paraffin/stearin 1:1 discs containing from 10(-5) to 10(-1) % pyriproxyfen and sticked at the bottom of plastic jars were evaluated for adult emergence inhibition (EI) on late 3rd or early 4th instar A. aegypti larvae. At the initial time t = 0, the EI was 100% for vessels containing beeswax or paraffin/stearin 1:1 discs containing up to 10(-4)% pyriproxyfen. For the lowest pyriproxyfen concentration of 10(-5)%, paraffin/stearin mixture gave a higher EI% value than beeswax (100 and 50%, respectively). Jars were kept at room temperature, and water was totally replaced every 15 days. Bioassays for residual activity repeated monthly showed that at 30 days and for pyriproxyfen 10(-5) % and both matrices, the EI values were low and comparable to control values. For pyriproxyfen 10(-4) %, EI remained above 95% for at least 90 days and around 75% up to 180 days. The EI values are always higher for paraffin/stearin mixture than for beeswax. For all other higher concentrations, 100% EI was obtained at least during 300 days. In a semi-field trial, paraffin/stearin/sand O-rings (2:1:2), containing pyriproxyfen 1%, were sunken in 200-l water-storage tanks and held outdoors in a shadow place. After 72 h, a 250-ml aliquot was taken (t = 0) obtaining 100 % EI. Water level was completed to 200 l every 15 days and bioassays repeated monthly as before. Residual activity remains with 100% EI at least for 6 months.

The impact of generalized joint laxity (GJL) on the posterior neck pain, cervical disc herniation, and cervical disc degeneration in the cervical spine.

PubMed

Lee, Sun-Mi; Oh, Su Chan; Yeom, Jin S; Shin, Ji-Hoon; Park, Sam-Guk; Shin, Duk-Seop; Ahn, Myun-Whan; Lee, Gun Woo

2016-12-01

Generalized joint laxity (GJL) can have a negative impact on lumbar spine pathology, including low back pain, disc degeneration, and disc herniation, but the relationship between GJL and cervical spine conditions remains unknown. To investigate the relationship between GJL and cervical spine conditions, including the prevalence of posterior neck pain (PNP), cervical disc herniation (CDH), and cervical disc degeneration (CDD), in a young, active population. Retrospective 1:2 matched cohort (case-control) study from prospectively collected data PATIENT SAMPLE: Of a total of 1853 individuals reviewed, 73 individuals with GJL (study group, gruop A) and 146 without GJL (control group, Group B) were included in the study according to a 1:2 case-control matched design for age, sex, and body mass index. The primary outcome measure was the prevalence and intensity of PNP at enrollment based on a visual analogue scale score for pain. The secondary outcome measures were (1) clinical outcomes as measured with the neck disability index (NDI) and 12-item short form health survey (SF-12) at enrollment, and (2) radiological outcomes of CDH and CDD at enrollment. We compared baseline data between groups. Descriptive statistical analyses were performed to compare the 2 groups in terms of the outcome measures. The prevalence and intensity of PNP were significantly greater in group A (patients with GJL) than in group B (patients without GJL) (prevalence: p=.02; intensity: p=.001). Clinical outcomes as measured with NDI and SF-12 did not differ significantly between groups. For radiologic outcomes, the prevalence of CDD was significantly greater in group A than in group B (p=.04), whereas the prevalence of CDH did not differ significantly between groups (p=.91). The current study revealed that GJL was closely related to the prevalence and intensity of PNP, suggesting that GJL may be a causative factor for PNP. In addition, GJL may contribute to the occurrence of CDD, but not CDH. Spine surgeons should screen for GJL in patientswith PNP and inform patients of its potential negative impact on disc degeneration of the cervical spine. Copyright © 2016 Elsevier Inc. All rights reserved.

Formation of S0 galaxies through mergers. Antitruncated stellar discs resulting from major mergers

NASA Astrophysics Data System (ADS)

Borlaff, Alejandro; Eliche-Moral, M. Carmen; Rodríguez-Pérez, Cristina; Querejeta, Miguel; Tapia, Trinidad; Pérez-González, Pablo G.; Zamorano, Jaime; Gallego, Jesús; Beckman, John

2014-10-01

Context. Lenticular galaxies (S0s) are more likely to host antitruncated (Type III) stellar discs than galaxies of later Hubble types. Major mergers are popularly considered too violent to make these breaks. Aims: We have investigated whether major mergers can result into S0-like remnants with realistic antitruncated stellar discs or not. Methods: We have analysed 67 relaxed S0 and E/S0 remnants resulting from dissipative N-body simulations of major mergers from the GalMer database. We have simulated realistic R-band surface brightness profiles of the remnants to identify those with antitruncated stellar discs. Their inner and outer discs and the breaks have been quantitatively characterized to compare with real data. Results: Nearly 70% of our S0-like remnants are antitruncated, meaning that major mergers that result in S0s have a high probability of producing Type III stellar discs. Our remnants lie on top of the extrapolations of the observational trends (towards brighter magnitudes and higher break radii) in several photometric diagrams, because of the higher luminosities and sizes of the simulations compared to observational samples. In scale-free photometric diagrams, simulations and observations overlap and the remnants reproduce the observational trends, so the physical mechanism after antitruncations is highly scalable. We have found novel photometric scaling relations between the characteristic parameters of the antitruncations in real S0s, which are also reproduced by our simulations. We show that the trends in all the photometric planes can be derived from three basic scaling relations that real and simulated Type III S0s fulfill: hi ∝ RbrkIII, ho ∝ RbrkIII, and μbrkIII ∝ RbrkIII, where hi and ho are the scalelengths of the inner and outer discs, and μbrkIII and RbrkIII are the surface brightness and radius of the breaks. Bars and antitruncations in real S0s are structurally unrelated phenomena according to the studied photometric planes. Conclusions: Major mergers provide a feasible mechanism to form realistic antitruncated S0 galaxies. Table 3 is available in electronic form at http://www.aanda.org

Restoring Segmental Biomechanics Through Nucleus Augmentation: An In Vitro Study.

PubMed

Pelletier, Matthew H; Cohen, Charles S; Ducheyne, Paul; Walsh, William R

2016-12-01

In vitro biomechanical laboratory study. The purpose of this study is to evaluate a mechanical treatment to create a degenerative motion segment and the ability of nucleus augmentation to restore biomechanics. In cases with an intact annulus fibrosus, the replacement or augmentation of the nucleus pulposus alone may provide a less invasive option to restore normal biomechanics and disk height when compared with spinal fusion or total disk replacement. Laboratory testing allows these changes to be fully characterized. However, without preexisting pathology, nucleus augmentation therapies are difficult to evaluate in vitro. The present study evaluated pure moment bending and compressive biomechanics in 3 states (n=6): (1) intact, (2) after creep loading and nucleus disruption to induce degenerative biomechanical changes, and (3) after nucleus augmentation through an injectable polymer (DiscCell). Neutral zone and ROM were increased in all modes of bending after the degenerative treatment. The most sensitive mode of bending was lateral bending, with intact ROM (20.0±2.9 degrees) increased to 22.3±2.6 degrees after degenerative treatment and reduced to 18.4±1.6 degrees after injection of the polymer. All bending ROM and NZ changes induced by the degenerative treatment were reversed by nucleus augmentation. This material was shown to be effective at altering motion segment biomechanics and restoring disk height during time zero tests. This technique may provide a model to examine the time zero performance of a nucleus augmentation device/material.

Runaway gas accretion and gap opening versus type I migration

NASA Astrophysics Data System (ADS)

Crida, A.; Bitsch, B.

2017-03-01

Growing planets interact with their natal protoplanetary disc, which exerts a torque onto them allowing them to migrate in the disc. Small mass planets do not affect the gas profile and migrate in the fast type-I migration. Although type-I migration can be directed outwards for planets smaller than 20 - 30M⊕ in some regions of the disc, planets above this mass should be lost into the central star long before the disc disperses. Massive planets push away material from their orbit and open a gap. They subsequently migrate in the slower, type II migration, which could save them from migrating all the way to the star. Hence, growing giant planets can be saved if and only if they can reach the gap opening mass, because this extends their migration timescale, allowing them to eventually survive at large orbits until the disc itself disperses. However, most of the previous studies only measured the torques on planets with fixed masses and orbits to determine the migration rate. Additionally, the transition between type-I and type-II migration itself is not well studied, especially when taking the growth mechanism of rapid gas accretion from the surrounding disc into account. Here we use isothermal 2D disc simulations with FARGO-2D1D to study the migration behaviour of gas accreting protoplanets in discs. We find that migrating giant planets always open gaps in the disc. We further show analytically and numerically that in the runaway gas accretion regime, the growth time-scale is comparable to the type-I migration time-scale, indicating that growing planets will reach gap opening masses before migrating all the way to the central star in type-I migration if the disc is not extremely viscous and/or thick. An accretion rate limited to the radial gas flow in the disc, in contrast, is not fast enough. When gas accretion by the planet is taken into account, the gap opening process is accelerated because the planet accretes material originating from its horseshoe region. This allows an accreting planet to transition to type-II migration before being lost even if gas fails to be provided for a rapid enough growth and the classical gap opening mass is not reached.

Clues on the Milky Way disc formation from population synthesis simulations

NASA Astrophysics Data System (ADS)

Robin, A. C.; Reylé, C.; Bienaymé, O.; Fernandez-Trincado, J. G.; Amôres, E. B.

2016-09-01

In recent years the stellar populations of the Milky Way have been investigated from large scale surveys in different ways, from pure star count analysis to detailed studies based on spectroscopic surveys. While in the former case the data can constrain the scale height and scale length thanks to completeness, they suffer from high correlation between these two values. On the other hand, spectroscopic surveys suffer from complex selection functions which hardly allow to derive accurate density distributions. The scale length in particular has been difficult to be constrained, resulting in discrepant values in the literature. Here, we investigate the thick disc characteristics by comparing model simulations with large scale data sets. The simulations are done from the population synthesis model of Besançon. We explore the parameters of the thick disc (shape, local density, age, metallicity) using a Monte Carlo Markov Chain method to constrain the model free parameters (Robin et al. 2014). Correlations between parameters are limited due to the vast spatial coverage of the used surveys (SDSS + 2MASS). We show that the thick disc was created during a long phase of formation, starting about 12 Gyr ago and finishing about 10 Gyr ago, during which gravitational contraction occurred, both vertically and radially. Moreover, in its early phase the thick disc was flaring in the outskirts. We conclude that the thick disc has been created prior to the thin disc during a gravitational collapse phase, slowed down by turbulence related to a high star formation rate, as explained for example in Bournaud et al. (2009) or Lehnert et al. (2009). Our result does not favor a formation from an initial thin disc thickened later by merger events or by secular evolution of the thin disc. We then study the in-plane distribution of stars in the thin disc from 2MASS and show that the thin disc scale length varies as a function of age, indicating an inside out formation. Moreover, we investigate the warp and flare and demonstrate that the warp amplitude is changing with time and the node angle is slightly precessing. Finally, we show comparisons between the new model and spectroscopic surveys. The new model allows to correctly simulate the kinematics, the metallicity, and α-abundance distributions in the solar neighbourhood as well as in the bulge region.

Cosmic clocks: a tight radius-velocity relationship for H I-selected galaxies

NASA Astrophysics Data System (ADS)

Meurer, Gerhardt R.; Obreschkow, Danail; Wong, O. Ivy; Zheng, Zheng; Audcent-Ross, Fiona M.; Hanish, D. J.

2018-05-01

H I-selected galaxies obey a linear relationship between their maximum detected radius Rmax and rotational velocity. This result covers measurements in the optical, ultraviolet, and H I emission in galaxies spanning a factor of 30 in size and velocity, from small dwarf irregulars to the largest spirals. Hence, galaxies behave as clocks, rotating once a Gyr at the very outskirts of their discs. Observations of a large optically selected sample are consistent, implying this relationship is generic to disc galaxies in the low redshift Universe. A linear radius-velocity relationship is expected from simple models of galaxy formation and evolution. The total mass within Rmax has collapsed by a factor of 37 compared to the present mean density of the Universe. Adopting standard assumptions, we find a mean halo spin parameter λ in the range 0.020-0.035. The dispersion in λ, 0.16 dex, is smaller than expected from simulations. This may be due to the biases in our selection of disc galaxies rather than all haloes. The estimated mass densities of stars and atomic gas at Rmax are similar (˜0.5 M⊙ pc-2), indicating outer discs are highly evolved. The gas consumption and stellar population build time-scales are hundreds of Gyr, hence star formation is not driving the current evolution of outer discs. The estimated ratio between Rmax and disc scalelength is consistent with long-standing predictions from monolithic collapse models. Hence, it remains unclear whether disc extent results from continual accretion, a rapid initial collapse, secular evolution, or a combination thereof.

Covalent Binding of Antibodies to Cellulose Paper Discs and Their Applications in Naked-eye Colorimetric Immunoassays.

PubMed

Peng, Yanfen; Gelder, Victor Van; Amaladoss, Anburaj; Patel, Kadamb Haribhai

2016-10-21

This report presents two methods for the covalent immobilization of capture antibodies on cellulose filter paper grade No. 1 (medium-flow filter paper) discs and grade No. 113 (fast-flow filter paper) discs. These cellulose paper discs were grafted with amine functional groups through a silane coupling technique before the antibodies were immobilized on them. Periodate oxidation and glutaraldehyde cross-linking methods were used to graft capture antibodies on the cellulose paper discs. In order to ensure the maximum binding capacity of the capture antibodies to their targets after immobilization, the effects of various concentrations of sodium periodate, glutaraldehyde, and capture antibodies on the surface of the paper discs were investigated. The antibodies that were coated on the amine-functionalized cellulose paper discs through a glutaraldehyde cross-linking agent showed enhanced binding activity to the target when compared to the periodate oxidation method. IgG (in mouse reference serum) was used as a reference target in this study to test the application of covalently immobilized antibodies through glutaraldehyde. A new paper-based, enzyme-linked immunosorbent assay (ELISA) was successfully developed and validated for the detection of IgG. This method does not require equipment, and it can detect 100 ng/ml of IgG. The fast-flow filter paper was more sensitive than the medium-flow filter paper. The incubation period of this assay was short and required small sample volumes. This naked-eye, colorimetric immunoassay can be extended to detect other targets that are identified with conventional ELISA.

Disc extrusions and bulges in nonspecific low back pain and sciatica: Exploratory randomised controlled trial comparing yoga therapy and normal medical treatment.

PubMed

Monro, Robin; Bhardwaj, Abhishek Kumar; Gupta, Ram Kumar; Telles, Shirley; Allen, Beth; Little, Paul

2015-01-01

Previous trials of yoga therapy for nonspecific low back pain (nsLBP) (without sciatica) showed beneficial effects. To test effects of yoga therapy on pain and disability associated with lumbar disc extrusions and bulges. Parallel-group, randomised, controlled trial. Sixty-one adults from rural population, aged 20-45, with nsLBP or sciatica, and disc extrusions or bulges. Randomised to yoga (n=30) and control (n=31). Yoga: 3-month yoga course of group classes and home practice, designed to ensure safety for disc extrusions. normal medical care. OUTCOME MEASURES (3-4 months) Primary: Roland Morris Disability Questionnaire (RMDQ); worst pain in past two weeks. Secondary: Aberdeen Low Back Pain Scale; straight leg raise test; structural changes. Disc projections per case ranged from one bulge or one extrusion to three bulges plus two extrusions. Sixty-two percent had sciatica. Intention-to-treat analysis of the RMDQ data, adjusted for age, sex and baseline RMDQ scores, gave a Yoga Group score 3.29 points lower than Control Group (0.98, 5.61; p=0.006) at 3 months. No other significant differences in the endpoints occurred. No adverse effects of yoga were reported. Yoga therapy can be safe and beneficial for patients with nsLBP or sciatica, accompanied by disc extrusions and bulges.

Quantitative measurement of intervertebral disc signal using MRI.

PubMed

Niemeläinen, R; Videman, T; Dhillon, S S; Battié, M C

2008-03-01

To investigate the spinal cord as an alternative intra-body reference to cerebrospinal fluid (CSF) in evaluating thoracic disc signal intensity. T2-weighted magnetic resonance imaging (MRI) images of T6-T12 were obtained using 1.5 T machines for a population-based sample of 523 men aged 35-70 years. Quantitative data on the signal intensities were acquired using an image analysis program (SpEx). A random sample of 30 subjects and intraclass correlation coefficients (ICC) were used to examine the repeatability of the spinal cord measurements. The validity of using the spinal cord as a reference was examined by correlating cord and CSF samples. Finally, thoracic disc signal was validated by correlating it with age without adjustment and adjusting for either cord or CSF. Pearson's r was used for correlational analyses. The repeatability of the spinal cord signal measurements was extremely high (>or=0.99). The correlations between the signals of spinal cord and CSF by level were all above 0.9. The spinal cord-adjusted disc signal and age correlated similarly with CSF-adjusted disc signal and age (r=-0.30 to -0.40 versus r=-0.26 to -0.36). Adjacent spinal cord is a good alternative reference to the current reference standard, CSF, for quantitative measurements of disc signal intensity. Clearly fewer levels were excluded when using spinal cord as compared to CSF due to missing reference samples.

The small observed scale of AGN-driven outflows, and inside-out disc quenching

NASA Astrophysics Data System (ADS)

Zubovas, Kastytis; King, Andrew

2016-11-01

Observations of massive outflows with detectable central active galactic nuclei (AGN) typically find them within radii ≲10 kpc. We show that this apparent size restriction is a natural result of AGN driving if this process injects total energy only of the order of the gas binding energy to the outflow, and the AGN varies over time (`flickers') as suggested in recent work. After the end of all AGN activity, the outflow continues to expand to larger radii, powered by the thermal expansion of the remnant-shocked AGN wind. We suggest that on average, outflows should be detected further from the nucleus in more massive galaxies. In massive gas-rich galaxies, these could be several tens of kpc in radius. We also consider the effect that pressure of such outflows has on a galaxy disc. In moderately gas-rich discs, with gas-to-baryon fraction <0.2, the outflow may induce star formation significant enough to be distinguished from quiescent by an apparently different normalization of the Kennicutt-Schmidt law. The star formation enhancement is probably stronger in the outskirts of galaxy discs, so coasting outflows might be detected by their effects upon the disc even after the driving AGN has shut off. We compare our results to the recent inference of inside-out quenching of star formation in galaxy discs.

Binary stars in the Galactic thick disc

NASA Astrophysics Data System (ADS)

Izzard, Robert G.; Preece, Holly; Jofre, Paula; Halabi, Ghina M.; Masseron, Thomas; Tout, Christopher A.

2018-01-01

The combination of asteroseismologically measured masses with abundances from detailed analyses of stellar atmospheres challenges our fundamental knowledge of stars and our ability to model them. Ancient red-giant stars in the Galactic thick disc are proving to be most troublesome in this regard. They are older than 5 Gyr, a lifetime corresponding to an initial stellar mass of about 1.2 M⊙. So why do the masses of a sizeable fraction of thick-disc stars exceed 1.3 M⊙, with some as massive as 2.3 M⊙? We answer this question by considering duplicity in the thick-disc stellar population using a binary population-nucleosynthesis model. We examine how mass transfer and merging affect the stellar mass distribution and surface abundances of carbon and nitrogen. We show that a few per cent of thick-disc stars can interact in binary star systems and become more massive than 1.3 M⊙. Of these stars, most are single because they are merged binaries. Some stars more massive than 1.3 M⊙ form in binaries by wind mass transfer. We compare our results to a sample of the APOKASC data set and find reasonable agreement except in the number of these thick-disc stars more massive than 1.3 M⊙. This problem is resolved by the use of a logarithmically flat orbital-period distribution and a large binary fraction.

Temporary Segmental Distraction in a Dog with Degenerative Lumbosacral Stenosis.

PubMed

Willems, Nicole; Kersten, Roel F M R; van Gaalen, Steven M; Öner, F Cumhur; Strijkers, Gustav J; Veraa, Stefanie; Beukers, Martijn; Tryfonidou, Marianna A; Meij, Björn P

2018-06-02

 Degenerative lumbosacral stenosis (DLSS) is characterized by intervertebral disc degeneration and causes lower back pain in dogs. Temporary distraction in rabbit models with induced intervertebral disc degeneration showed signs of intervertebral disc repair. In the present study, we assessed safety and efficacy of temporary segmental distraction in a dog with clinical signs of DLSS.  Distraction of the lumbosacral junction by pedicle screw-rod fixation was applied in a 5-year-old Greyhound with DLSS and evaluated by radiography, magnetic resonance imaging, and force plate analysis before and after distraction.  Safe distraction of the lumbosacral junction was demonstrated, with improvement of clinical signs after removal of the distraction device. Signal intensity of the intervertebral disc showed no changes over time. T2 value was highest directly after removal of the distraction device but decreased by 10% of the preoperative value at 9 months of follow-up. Disc height decreased (8%) immediately after removal of the distraction device, but recovered to the initial value. A decrease in the pelvic/thoracic propulsive force during pedicle screw-rod fixation and distraction was demonstrated, which slowly increased by 4% compared with the initial value.  Temporary pedicle screw-rod fixation in combination with distraction in a dog with DLSS was safe, improved clinical signs and retained disc height at 9 months of follow-up. Schattauer GmbH Stuttgart.

Active galactic nucleus outflows in galaxy discs

NASA Astrophysics Data System (ADS)

Hartwig, Tilman; Volonteri, Marta; Dashyan, Gohar

2018-05-01

Galactic outflows, driven by active galactic nuclei (AGNs), play a crucial role in galaxy formation and in the self-regulated growth of supermassive black holes (BHs). AGN feedback couples to and affects gas, rather than stars, and in many, if not most, gas-rich galaxies cold gas is rotationally supported and settles in a disc. We present a 2D analytical model for AGN-driven outflows in a gaseous disc and demonstrate the main improvements, compared to existing 1D solutions. We find significant differences for the outflow dynamics and wind efficiency. The outflow is energy-driven due to inefficient cooling up to a certain AGN luminosity (˜1043 erg s-1 in our fiducial model), above which the outflow remains momentum-driven in the disc up to galactic scales. We reproduce results of 3D simulations that gas is preferentially ejected perpendicular to the disc and find that the fraction of ejected interstellar medium is lower than in 1D models. The recovery time of gas in the disc, defined as the free-fall time from the radius to which the AGN pushes the ISM at most, is remarkably short, of the order 1 Myr. This indicates that AGN-driven winds cannot suppress BH growth for long. Without the inclusion of supernova feedback, we find a scaling of the BH mass with the halo velocity dispersion of MBH ∝ σ4.8.

Psychopathological Influence of Lumbar Disc Herniation in Male Adolescent

PubMed Central

Kim, Tae Woo; Oh, Chang Hyun; Shim, Yu Sik; Park, Hyeong-chun; Park, Chong Oon

2013-01-01

Purpose There is no report about psychopathological effect causing by disc herniation. The disease could impose psychopathological influence on the social life, the treatment period, and response to the treatment. This study was to evaluate retrospectively the psychopathological influence of lumbar disc herniation (LDH) among Korean 19-year-old males. Materials and Methods We compared the Korean military multiphasic personality inventory (KMPI) profiles of 74 LDH cases with the KMPI profiles of 150 controls. The LDH groups were categorized to 2 groups according to the presence of thecal sac compression by disc materials, and evaluated the relation between the KMPI and LDH. Results The decrease of the faking-good response scale and increase of the faking-bad response scale were observed more in the LDH group than in the normal volunteer group (p<0.05). The neurosis set such as anxiety, depression and somatization was markedly increased in the LDH group compared to the normal volunteers group (p<0.05). The scale of personality disorder was also increased more in the LDH group (p=0.002). The differences of KMPI scales were not correlated with the severe pathology of LDH. Conclusion Young male with LDH may tend to have more abnormal results of multiphasic personality inventory test compared to the normal volunteers, suggesting that LDH may be related to the psychopathology in young males in Korea. Therefore, clinicians are recommended to evaluate and treat the psychopathological aspects in patients with LDH. PMID:23709412

Effect of neonatal gene therapy on lumbar spine disease in mucopolysaccharidosis VII dogs

PubMed Central

Smith, Lachlan J; Martin, John T; O'Donnell, Patricia; Wang, Ping; Elliott, Dawn M; Haskins, Mark E; Ponder, Katherine P

2012-01-01

Mucopolysaccharidosis VII (MPS VII) is due to deficient β-glucuronidase (GUSB) activity, which leads to accumulation of chondroitin, heparan, and dermatan sulfate glycosaminoglycans in various tissues including those of the spine. Associated spine disease can be due to abnormalities in the vertebrae, the intervertebral discs, or other spine tissues. The goal of this study was to determine if neonatal gene therapy could prevent lumbar spine disease in MPS VII dogs. MPS VII dogs were injected intravenously with a retroviral vector (RV) expressing canine GUSB at 2 to 3 days after birth, which resulted in transduction of hepatocytes that secreted GUSB into blood. Expression was stable for up to 11 years, and mean survival was increased from 0.4 years in untreated dogs to 6.1 years in treated dogs. Despite a profound positive clinical effect, 6-month-old RV-treated MPS VII dogs still had hypoplastic ventral epiphyses with reduced calcification in the lumbar spine, which resulted in a reduced stiffness and increased range of motion that was not improved relative to untreated MPS VII dogs. At six to 11 years of age, ventral vertebrae remained hypoplastic in RV-treated MPS VII dogs, and there was desiccation of the nucleus pulposus in some discs. Histochemical staining demonstrated that discs did not have detectable GUSB activity despite high serum GUSB activity, which is likely due to poor diffusion into this relatively avascular structure. Thus, neonatal gene therapy cannot prevent lumbar spine disease in MPS VII dogs, which predicts that enzyme replacement therapy (ERT) will similarly be relatively ineffective even if started at birth. PMID:22510705

Competition among gene regulatory networks imposes order within the eye-antennal disc of Drosophila

PubMed Central

Weasner, Bonnie M.; Kumar, Justin P.

2013-01-01

The eye-antennal disc of Drosophila gives rise to numerous adult tissues, including the compound eyes, ocelli, antennae, maxillary palps and surrounding head capsule. The fate of each tissue is governed by the activity of unique gene regulatory networks (GRNs). The fate of the eye, for example, is controlled by a set of fourteen interlocking genes called the retinal determination (RD) network. Mutations within network members lead to replacement of the eyes with head capsule. Several studies have suggested that in these instances all retinal progenitor and precursor cells are eliminated via apoptosis and as a result the surrounding head capsule proliferates to compensate for retinal tissue loss. This model implies that the sole responsibility of the RD network is to promote the fate of the eye. We have re-analyzed eyes absent mutant discs and propose an alternative model. Our data suggests that in addition to promoting an eye fate the RD network simultaneously functions to actively repress GRNs that are responsible for directing antennal and head capsule fates. Compromising the RD network leads to the inappropriate expression of several head capsule selector genes such as cut, Lim1 and wingless. Instead of undergoing apoptosis, a population of mutant retinal progenitors and precursor cells adopt a head capsule fate. This transformation is accompanied by an adjustment of cell proliferation rates such that just enough head capsule is generated to produce an intact adult head. We propose that GRNs simultaneously promote primary fates, inhibit alternative fates and establish cell proliferation states. PMID:23222441

On-line damage detection in rotating machinery

NASA Astrophysics Data System (ADS)

Alkhalifa, Tareq Jawad

This work is concerned with a set of techniques to detect internal defects in uniform circular discs (rotors). An internal defect is intentionally manufactured in stereolithographic discs by a rapid prototyping process using cured resin SL 5170 material. The analysis and results presented here are limited to a uniform circular disc, with internal defects, mounted on a uniform flexible circular shaft. The setup is comprised of a Bently Nevada rotor kit connected to a data acquisition system. The rotor consists of a disc and shaft that is supported by journal bearings and is coupled to a motor by a rubber joint. Damage produces localized changes in the strain energy, which is quantified to characterize the damage. Based on previous research, the Strain Energy Damage Index (SEDI) is utilized to localize the damage due to strain energy differences between damaged and undamaged modes. To accomplish the objective, this work covers three types of analysis: finite element analysis, vibration analysis, and experimental modal analysis. Finite element analysis (using SDRC Ideas software) is performed to develop a multi-degree-of-freedom (MDOF) rotor system with internal damage, and its dynamic characteristics are investigated. The analysis is performed for two different types damage cases: radial damage and circular damage. Parametric study for radial damage and random noise to undamaged disc have been investigated to predict the effect of noise in the damage detection. The developed on-line damage detection technique for rotating equipment incorporates and couples both vibration analysis and experimental modal analysis. The dynamic investigation of the rotating discs (with and without defect) is conducted by vibration signal analysis (using proximity sensors, data acquisition and LabView). The vibration analysis provides a unique vibration signature for the damaged disc, which indicates the existence of the damage. The vibration data are acquired at different running speeds (1000, 2500, 5000 rpm). Then the dynamic investigation of non-rotating discs (with and without defect) is conducted by experimental modal analysis (using STAR software). While the vibration analysis detects and indicates the existence of damage while the disc is rotating, experimental modal analysis (using STAR and MATLAB software) provides the localization of damage through the modal parameters for a non-rotating disc. Both of the experimental diagnostic algorithms are based on measurement of the dynamic behavior of the damaged disc. The results are compared with the reference, or baseline, one, obtained initially for an undamaged disc. (Abstract shortened by UMI.)

Dentin abrasivity of various desensitizing toothpastes.

PubMed

Arnold, W H; Gröger, Ch; Bizhang, M; Naumova, E A

2016-04-02

The aim of this study was to compare the abrasivity of various commercially available toothpastes that claim to reduce dentin hypersensitivity. Dentin discs were prepared from 70 human extracted molars. The discs were etched with lemon juice for 5 min, and one half of the discs were covered with aluminum tape. Following this, they were brushed with 6 different toothpastes, simulating a total brushing time of 6 months. As a negative control, discs were brushed with tap water only. The toothpastes contained pro-arginine and calcium carbonate, strontium acetate, stannous fluoride, zinc carbonate and hydroxyapatite, new silica, or tetrapotassium pyrophosphate and hydroxyapatite. After brushing, the height differences between the control halves and the brushed halves were determined with a profilometer and statistically compared using a Mann-Whitney U test for independent variables. A significant difference (p < 0.001) in height difference between the controls and the toothpaste-treated samples was found in all cases, except for the stannous fluoride-containing toothpaste (p = 0.583). The highest abrasion was found in the toothpaste containing zinc carbonate and hydroxyapatite, and the lowest was found in the toothpaste containing pro-arginine and calcium carbonate. Desensitizing toothpastes with different desensitizing ingredients have different levels of abrasivity, which may have a negative effect on their desensitizing abilities over a long period of time.

Quantitative comparison of disc rim color in optic nerve atrophy of compressive optic neuropathy and glaucomatous optic neuropathy.

PubMed

Nakano, Eri; Hata, Masayuki; Oishi, Akio; Miyamoto, Kazuaki; Uji, Akihito; Fujimoto, Masahiro; Miyata, Manabu; Yoshimura, Nagahisa

2016-08-01

The purpose was to investigate an objective and quantitative method to estimate the redness of the optic disc neuroretinal rim, and to determine the usefulness of this method to differentiate compressive optic neuropathy (CON) from glaucomatous optic neuropathy (GON). In our study there were 126 eyes: 40 with CON, 40 with normal tension glaucoma (NTG), and 46 normal eyes (NOR). Digital color fundus photographs were assessed for the redness of disc rim color using ImageJ software. We separately measured the intensity of red, green, and blue pixels from RGB images. Three disc color indices (DCIs), which indicate the redness intensity, were calculated through existing formulas. All three DCIs of CON were significantly smaller than those of NOR (P < 0.001). In addition, when compared with NTG, DCIs were also significantly smaller in CON (P < 0.05). A comparison of mild CON and mild NTG (mean deviation (MD) > -6 dB), in which the extent of retinal nerve fiber layer thinning is comparable, the DCIs of mild CON were significantly smaller than those of mild NTG (P < 0.05). In contrast, DCIs did not differ between moderate-to-severe stages of CON and NTG (MD ≤ -6 dB), though the retinal nerve fibers of CON were more severely damaged than those of NTG. To differentiate between mild CON and mild NTG, all AUROCs for the three DCIs were above 0.700. A quantitative and objective assessment of optic disc color was useful in differentiating early-stage CON from GON and NOR.

Regulation of CCN2/CTGF Expression in the Nucleus Pulposus of the Intervertebral Disc: Role of Smad and AP1 Signaling

PubMed Central

Tran, Cassie M.; Markova, Dessislava; Smith, Harvey E.; Susarla, Bala; Ponnappan, Ravi Kumar; Anderson, D Greg; Symes, Aviva; Shapiro, Irving M.; Risbud, Makarand V.

2011-01-01

Objective To investigate TGFβ regulation of CTGF expression in cells of the nucleus pulposus. Methods Real Time RT-PCR and Western blot analysis was used to measure CTGF expression in the nucleus pulposus. Transfections were used to measure the effect of Smad2/3/7 and AP1on TGFβ mediated CTGF promoter activity. Results CTGF expression was lower in the neonatal disc compared with the skeletally mature rat disc. An increase in CTGF expression and promoter activity was observed in nucleus pulposus cells after TGFβ treatment. Deletion analysis indicated that promoter constructs lacking smad and AP1 motifs were unresponsive to treatment. Analysis showed that full-length Smad3 and the Smad3-MH2 domain alone increased CTGF activity. Further evidence of Smad3 and AP1 involvement was seen when DN-Smad3, SiRNA-Smad3, smad7 and DN-AP1 suppressed TGFβ mediated activation of the CTGF promoter. When either Smad3 or AP1 sites were mutated, CTGF promoter induction by TGFβ was suppressed. We also observed a decrease in expression of CTGF in discs of Smad3 null mice compared to the wild type. Analysis of human nucleus pulposus indicated a trend of increasing CTGF and TGFβ expression in the degenerate state. Conclusion TGFβ, through Smad3 and AP1, serves as a positive regulator of CTGF expression in the nucleus pulposus. We propose that CTGF is a part of the limited reparative response of the degenerate disc. PMID:20222112

The influence of exogenous cross-linking and compressive creep loading on intradiscal pressure.

PubMed

Chuang, Shih-Youeng; Lin, Leou-Chyr; Hedman, Thomas P

2010-10-01

This study involves a biomechanical evaluation of a prospective injectable treatment for degenerative discs. The high osmolarity of the non-degenerated nucleus pulposus attracts water contributing to the hydrostatic behavior of the tissue. This intradiscal pressure is known to drop as fluid is exuded from the matrix due to compressive loading. The objective of this study was to compare the changes in intradiscal pressure in control and genipin cross-linked intervertebral discs. Thirty bovine lumbar motion segments were randomly divided into a phosphate-buffered saline control group and a 0.33% genipin group and soaked at room temperature for 2 days. A needle pressure sensor was held in the center of the disc while short-term and static creep compressive loads were applied. The control group demonstrated a 25% higher average intradiscal pressure compared to genipin-treated discs under 750 N compressive load (p=0.029). Depressurization during static compressive creep was 56% higher in the control than in the genipin group (p=0.014). These results suggest cross-linking induced changes in the poroelastic properties of the involved tissues affected the mechanics of compressive load support in the disc with lower levels of nucleus pressure, a corresponding decrease in the elastic expansion of the annulus, and an increased axial compressive loading of the inner and outer annulus tissues. It is possible that concurrent changes in hydraulic permeability and proteoglycan retention known to be associated with genipin cross-linking were also contributors to poroelastic changes. Reduction of peak pressures and moderation of pressure fluctuations could be beneficial relative to discogenic pain.

Antifungal susceptibility testing of Malassezia yeast: comparison of two different methodologies.

PubMed

Rojas, Florencia D; Córdoba, Susana B; de Los Ángeles Sosa, María; Zalazar, Laura C; Fernández, Mariana S; Cattana, María E; Alegre, Liliana R; Carrillo-Muñoz, Alfonso J; Giusiano, Gustavo E

2017-02-01

All Malassezia species are lipophilic; thus, modifications are required in susceptibility testing methods to ensure their growth. Antifungal susceptibility of Malassezia species using agar and broth dilution methods has been studied. Currently, few tests using disc diffusion methods are being performed. The aim was to evaluate the in vitro susceptibility of Malassezia yeast against antifungal agents using broth microdilution and disc diffusion methods, then to compare both methodologies. Fifty Malassezia isolates were studied. Microdilution method was performed as described in reference document and agar diffusion test was performed using antifungal tablets and discs. To support growth, culture media were supplemented. To correlate methods, linear regression analysis and categorical agreement was determined. The strongest linear association was observed for fluconazole and miconazole. The highest agreement between both methods was observed for itraconazole and voriconazole and the lowest for amphotericin B and fluconazole. Although modifications made to disc diffusion method allowed to obtain susceptibility data for Malassezia yeast, variables cannot be associated through a linear correlation model, indicating that inhibition zone values cannot predict MIC value. According to the results, disc diffusion assay may not represent an alternative to determine antifungal susceptibility of Malassezia yeast. © 2016 Blackwell Verlag GmbH.

Subjects with temporomandibular joint disc displacement do not feature any peculiar changes in body posture.

PubMed

Rocha, T; Castro, M A; Guarda-Nardini, L; Manfredini, D

2017-02-01

The presence of body posture changes among patients with temporomandibular disorders (TMD) has been a controversial topic in dentistry. Based on that, the aim of this study was to assess postural features of pain-free subjects with internal derangement of the temporomandibular joint (TMJ), viz. disc displacement, when compared to subjects with normal disc position. A total of 21 subjects with unilateral, pain-free TMJ disc displacement (DD) and 21 subjects without any TMD signs of symptoms were assessed for body posture changes by means of posturographic evaluation of several body segments and postural balance reactions through the centre of mass during jaw movements using a balance platform. Posturographic measurements showed the absence of any significant differences between the two groups in any of the outcome parameters. Similarly, all balance platform responses to mandibular movements were not different between groups. There are no significant differences in body posture between subjects with and without unilateral disc displacement in the temporomandibular joint. Such observations, indicating a well-preserved postural balance in the presence of TMJ internal derangement, put into serious question the potential influence of TMJ disorders on whole body posture and viceversa. © 2016 John Wiley & Sons Ltd.

Super-Cavitating Flow Around Two-Dimensional Conical, Spherical, Disc and Stepped Disc Cavitators

NASA Astrophysics Data System (ADS)

Sooraj, S.; Chandrasekharan, Vaishakh; Robson, Rony S.; Bhanu Prakash, S.

2017-08-01

A super-cavitating object is a high speed submerged object that is designed to initiate a cavitation bubble at the nose which extends past the aft end of the object, substantially reducing the skin friction drag that would be present if the sides of the object were in contact with the liquid in which the object is submerged. By reducing the drag force the thermal energy consumption to move faster can also be minimised. The super-cavitation behavioural changes with respect to Cavitators of various geometries have been studied by varying the inlet velocity. Two-dimensional computational fluid dynamics analysis has been carried out by applying k-ε turbulence model. The variation of drag coefficient, cavity length with respect to cavitation number and inlet velocity are analyzed. Results showed conical Cavitator with wedge angle of 30° has lesser drag coefficient and cavity length when compared to conical Cavitators with wedge angles 45° and 60°, spherical, disc and stepped disc Cavitators. Conical cavitator 60° and disc cavitator have the maximum cavity length but with higher drag coefficient. Also there is significant variation of supercavitation effect observed between inlet velocities of 32 m/s to 40 m/s.

Suppression of atmospheric recycling of planets embedded in a protoplanetary disc by buoyancy barrier

NASA Astrophysics Data System (ADS)

Kurokawa, Hiroyuki; Tanigawa, Takayuki

2018-06-01

The ubiquity of super-Earths poses a problem for planet formation theory to explain how they avoided becoming gas giants. Rapid recycling of the envelope gas of planets embedded in a protoplanetary disc has been proposed to delay the cooling and following accretion of disc gas. We compare isothermal and non-isothermal 3D hydrodynamical simulations of the gas flow past a planet to investigate the influence on the feasibility of the recycling mechanism. Radiative cooling is implemented by using the β cooling model. We find that, in either case, gas enters the Bondi sphere at high latitudes and leaves through the midplane regions, or vice versa when disc gas rotates sub-Keplerian. However, in contrast to the isothermal case where the recycling flow reaches the deeper part of the envelope, the inflow is inhibited from reaching the deep envelope in the non-isothermal case. Once the atmosphere starts cooling, buoyant force prevents the high-entropy disc gas from intruding the low-entropy atmosphere. We suggest that the buoyancy barrier isolates the lower envelope from the recycling and allows further cooling, which may lead runaway gas accretion onto the core.

Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles

PubMed Central

Wu, Liang; Jackson, George; Müller, Erich A.

2013-01-01

We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the centre of mass. Even for isotropic attractive interactions, the resulting overall inter-particle potential is anisotropic, due to the orientation-dependent excluded volume of the underlying hard core. An algebraic equation of state for attractive disc particles is developed by adopting the Onsager trial function to characterize the orientational order in the nematic phase. The theory is then used to represent the fluid-phase behaviour (vapour-liquid, isotropic-nematic, and nematic-nematic) of the oblate attractive particles for varying values of the molecular aspect ratio and parameters of the attractive potential. When compared to the phase diagram of their athermal analogues, it is seen that the addition of an attractive interaction facilitates the formation of orientationally-ordered phases. Most interestingly, for certain aspect ratios, a coexistence between two anisotropic nematic phases is exhibited by the attractive disc-like fluids. PMID:23965962

Liquid crystal phase behaviour of attractive disc-like particles.

PubMed

Wu, Liang; Jackson, George; Müller, Erich A

2013-08-08

We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the centre of mass. Even for isotropic attractive interactions, the resulting overall inter-particle potential is anisotropic, due to the orientation-dependent excluded volume of the underlying hard core. An algebraic equation of state for attractive disc particles is developed by adopting the Onsager trial function to characterize the orientational order in the nematic phase. The theory is then used to represent the fluid-phase behaviour (vapour-liquid, isotropic-nematic, and nematic-nematic) of the oblate attractive particles for varying values of the molecular aspect ratio and parameters of the attractive potential. When compared to the phase diagram of their athermal analogues, it is seen that the addition of an attractive interaction facilitates the formation of orientationally-ordered phases. Most interestingly, for certain aspect ratios, a coexistence between two anisotropic nematic phases is exhibited by the attractive disc-like fluids.

Long term multiwavelength studies of the corona/disc connection in AGN

NASA Astrophysics Data System (ADS)

Buisson, D.; Lohfink, A.; Alston, W.; Fabian, A.; Gallo, L.; Kara, E.; Zoghbi, A.; Wilkins, D.; Miller, J.; Cackett, E.

2017-10-01

One way of increasing our understanding of AGN is determining the nature of the connection between the optical/UV emitting accretion disc and the X-ray emitting corona. Studies of variability in these two bands are a key tool for gaining insight into the processes involved. We will present results from a sample of long-term AGN monitoring campaigns in the optical, UV and X-ray with Swift. In particular, we will explore UV/optical-X-ray correlations and associated time lags. We will compare these measurements and the UV/optical RMS spectra with theoretical reprocessing models and confront recent claims of the observed lags being longer than those which are expected for a standard thin disc. Additionally, a new Swift monitoring campaign of the z=2 quasar PG 1247+267 allows us to probe the shorter wavelengths at the peak of the accretion disc spectrum, providing information on the region of the disc closest to the black hole. However, not all AGN show such correlations, including IRAS 13224-3809, the subject of a recent 1.5 Ms XMM observation. Using this and other examples, we will explore the possible reasons for the lack of observed correlation.

Fluid mechanics of heart valves.

PubMed

Yoganathan, Ajit P; He, Zhaoming; Casey Jones, S

2004-01-01

Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.

Growth factor effects on costal chondrocytes for tissue engineering fibrocartilage

PubMed Central

Johns, D.E.; Athanasiou, K.A.

2010-01-01

Tissue engineered fibrocartilage could become a feasible option for replacing tissues like the knee meniscus or temporomandibular joint disc. This study employed five growth factors insulin-like growth factor-I, transforming growth factor-β1, epidermal growth factor, platelet-derived growth factor-BB, and basic fibroblast growth factor in a scaffoldless approach with costal chondrocytes, attempting to improve biochemical and mechanical properties of engineered constructs. Samples were quantitatively assessed for total collagen, glycosaminoglycans, collagen type I, collagen type II, cells, compressive properties, and tensile properties at two time points. Most treated constructs were worse than the no growth factor control, suggesting a detrimental effect, but the IGF treatment tended to improve the constructs. Additionally, the 6wk time point was consistently better than 3wks, with total collagen, glycosaminoglycans, and aggregate modulus doubling during this time. Further optimization of the time in culture and exogenous stimuli will be important in making a more functional replacement tissue. PMID:18597118

Biotribological evaluation of artificial disc arthroplasty devices: influence of loading and kinematic patterns during in vitro wear simulation.

PubMed

Grupp, Thomas M; Yue, James J; Garcia, Rolando; Basson, Janet; Schwiesau, Jens; Fritz, Bernhard; Blömer, Wilhelm

2009-01-01

Wear simulation is an essential pre-clinical method to predict the mid- and long-term clinical wear behavior of newly introduced devices for total disc arthroplasty. The main requirement of a suitable method for spinal wear simulation has to be the ability to distinguish between design concepts and allow for a direct comparison of predicate devices. The objective of our study was to investigate the influence of loading and kinematic patterns based on two different protocols for spinal wear simulation (ISO/FDIS 18192-1 (2006) and ASTM F2423-05). In vitro wear simulation was performed with six activ L lumbar artificial disc devices (Aesculap Tuttlingen, Germany). The applied kinematic pattern of movement was multidirectional for ISO (elliptic track) and unidirectional with a curvilinear shape for ASTM. Testing was done for 10 million cycles in the ISO loading mode and afterwards with the same specimens for 5 million cycles according to the ASTM protocol with a customized six-station servohydraulic spinal wear simulator (EndoLab Thansau, Germany). Gravimetrical and geometrical wear assessment, a slide track analysis correlated to an optical surface characterization, and an estimation of particle size and morphology were performed. The gravimetric wear rate for the first 10 million cycles was ISO(initial) = 2.7 +/- 0.3 mg/million cycles. During the ASTM test period (10-15 million cycles) a gravimetric wear rate of 0.14 +/- 0.06 mg/million cycles was estimated. The wear rates between the ISO and ASTM driven simulations differ substantially (approximately 20-fold) and statistical analysis demonstrates a significant difference (p < 0.001) between the test groups. The main explanation of divergency between ISO and ASTM driven wear simulations is the multidirectional pattern of movement described in the ISO document resulting in a cross-shear stress on the polyethylene material. Due to previous retrieval observations, it seems to be very unlikely that a lumbar artificial disc is loaded with a linear wear path.Testing according to ASTM F2423-05 with pure unidirectional motion does not reflect the kinematics of TDA patients' daily activities. Based on our findings it seems to be more reliable to predict the clinical wear behavior of an artificial disc replacement using the ISO/FDIS 18192-1 method.

Biotribological evaluation of artificial disc arthroplasty devices: influence of loading and kinematic patterns during in vitro wear simulation

PubMed Central

Yue, James J.; Garcia, Rolando; Basson, Janet; Schwiesau, Jens; Fritz, Bernhard; Blömer, Wilhelm

2008-01-01

Wear simulation is an essential pre-clinical method to predict the mid- and long-term clinical wear behavior of newly introduced devices for total disc arthroplasty. The main requirement of a suitable method for spinal wear simulation has to be the ability to distinguish between design concepts and allow for a direct comparison of predicate devices. The objective of our study was to investigate the influence of loading and kinematic patterns based on two different protocols for spinal wear simulation (ISO/FDIS 18192-1 (2006) and ASTM F2423-05). In vitro wear simulation was performed with six activ® L lumbar artificial disc devices (Aesculap Tuttlingen, Germany). The applied kinematic pattern of movement was multidirectional for ISO (elliptic track) and unidirectional with a curvilinear shape for ASTM. Testing was done for 10 million cycles in the ISO loading mode and afterwards with the same specimens for 5 million cycles according to the ASTM protocol with a customized six-station servohydraulic spinal wear simulator (EndoLab Thansau, Germany). Gravimetrical and geometrical wear assessment, a slide track analysis correlated to an optical surface characterization, and an estimation of particle size and morphology were performed. The gravimetric wear rate for the first 10 million cycles was ISOinitial = 2.7 ± 0.3 mg/million cycles. During the ASTM test period (10–15 million cycles) a gravimetric wear rate of 0.14 ± 0.06 mg/million cycles was estimated. The wear rates between the ISO and ASTM driven simulations differ substantially (approximately 20-fold) and statistical analysis demonstrates a significant difference (p < 0.001) between the test groups. The main explanation of divergency between ISO and ASTM driven wear simulations is the multidirectional pattern of movement described in the ISO document resulting in a cross-shear stress on the polyethylene material. Due to previous retrieval observations, it seems to be very unlikely that a lumbar artificial disc is loaded with a linear wear path.Testing according to ASTM F2423-05 with pure unidirectional motion does not reflect the kinematics of TDA patients‘ daily activities. Based on our findings it seems to be more reliable to predict the clinical wear behavior of an artificial disc replacement using the ISO/FDIS 18192-1 method. PMID:19050942

Adjacent-level arthroplasty following cervical fusion.

PubMed

Rajakumar, Deshpande V; Hari, Akshay; Krishna, Murali; Konar, Subhas; Sharma, Ankit

2017-02-01

OBJECTIVE Adjacent-level disc degeneration following cervical fusion has been well reported. This condition poses a major treatment dilemma when it becomes symptomatic. The potential application of cervical arthroplasty to preserve motion in the affected segment is not well documented, with few studies in the literature. The authors present their initial experience of analyzing clinical and radiological results in such patients who were treated with arthroplasty for new or persistent arm and/or neck symptoms related to neural compression due to adjacent-segment disease after anterior cervical discectomy and fusion (ACDF). METHODS During a 5-year period, 11 patients who had undergone ACDF anterior cervical discectomy and fusion (ACDF) and subsequently developed recurrent neck or arm pain related to adjacent-level cervical disc disease were treated with cervical arthroplasty at the authors' institution. A total of 15 devices were implanted (range of treated levels per patient: 1-3). Clinical evaluation was performed both before and after surgery, using a visual analog scale (VAS) for pain and the Neck Disability Index (NDI). Radiological outcomes were analyzed using pre- and postoperative flexion/extension lateral radiographs measuring Cobb angle (overall C2-7 sagittal alignment), functional spinal unit (FSU) angle, and range of motion (ROM). RESULTS There were no major perioperative complications or device-related failures. Statistically significant results, obtained in all cases, were reflected by an improvement in VAS scores for neck/arm pain and NDI scores for neck pain. Radiologically, statistically significant increases in the overall lordosis (as measured by Cobb angle) and ROM at the treated disc level were observed. Three patients were lost to follow-up within the first year after arthroplasty. In the remaining 8 cases, the duration of follow-up ranged from 1 to 3 years. None of these 8 patients required surgery for the same vertebral level during the follow-up period. CONCLUSIONS Artificial cervical disc replacement in patients who have previously undergone cervical fusion surgery appears to be safe, with encouraging early clinical results based on this small case series, but more data from larger numbers of patients with long-term follow-up are needed. Arthroplasty may provide an additional tool for the management of post-fusion adjacent-level cervical disc disease in carefully selected patients.

Compressed 3D and 2D digital images versus standard 3D slide film for the evaluation of glaucomatous optic nerve features.

PubMed

Sandhu, Simrenjeet; Rudnisky, Chris; Arora, Sourabh; Kassam, Faazil; Douglas, Gordon; Edwards, Marianne C; Verstraten, Karin; Wong, Beatrice; Damji, Karim F

2018-03-01

Clinicians can feel confident compressed three-dimensional digital (3DD) and two-dimensional digital (2DD) imaging evaluating important features of glaucomatous disc damage is comparable to the previous gold standard of stereoscopic slide film photography, supporting the use of digital imaging for teleglaucoma applications. To compare the sensitivity and specificity of 3DD and 2DD photography with stereo slide film in detecting glaucomatous optic nerve head features. This prospective, multireader validation study imaged and compressed glaucomatous, suspicious or normal optic nerves using a ratio of 16:1 into 3DD and 2DD (1024×1280 pixels) and compared both to stereo slide film. The primary outcome was vertical cup-to-disc ratio (VCDR) and secondary outcomes, including disc haemorrhage and notching, were also evaluated. Each format was graded randomly by four glaucoma specialists. A protocol was implemented for harmonising data including consensus-based interpretation as needed. There were 192 eyes imaged with each format. The mean VCDR for slide, 3DD and 2DD was 0.59±0.20, 0.60±0.18 and 0.62±0.17, respectively. The agreement of VCDR for 3DD versus film was κ=0.781 and for 2DD versus film was κ=0.69. Sensitivity (95.2%), specificity (95.2%) and area under the curve (AUC; 0.953) of 3DD imaging to detect notching were better (p=0.03) than for 2DD (90.5%; 88.6%; AUC=0.895). Similarly, sensitivity (77.8%), specificity (98.9%) and AUC (0.883) of 3DD to detect disc haemorrhage were better (p=0.049) than for 2DD (44.4%; 99.5%; AUC=0.72). There was no difference between 3DD and 2DD imaging in detecting disc tilt (p=0.7), peripapillary atrophy (p=0.16), grey crescent (p=0.1) or pallor (p=0.43), although 3D detected sloping better (p=0.013). Both 3DD and 2DD imaging demonstrates excellent reproducibility in comparison to stereo slide film with experts evaluating VCDR, notching and disc haemorrhage. 3DD in this study was slightly more accurate than 2DD for evaluating disc haemorrhage, notching and sloping. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Effect of Interbody Fusion on the Remaining Discs of the Lumbar Spine in Subjects with Disc Degeneration.

PubMed

Ryu, Robert; Techy, Fernando; Varadarajan, Ravikumar; Amirouche, Farid

2016-02-01

To study effects (stress loads) of lumbar fusion on the remaining segments (adjacent or not) of the lumbar spine in the setting of degenerated adjacent discs. A lumbar spine finite element model was built and validated. The full model of the lumbar spine was a parametric finite element model of segments L 1-5 . Numerous hypothetical combinations of one-level lumbar spine fusion and one-level disc degeneration were created. These models were subjected to 10 Nm flexion and extension moments and the stresses on the endplates and consequently on the intervertebral lumbar discs measured. These values were compared to the stresses on healthy lumbar spine discs under the same load and fusion scenarios. Increased stress at endplates was observed only in the settings of L4-5 fusion and L3-4 disc degeneration (8% stress elevation at L2,3 in flexion or extension, and 25% elevation at L3,4 in flexion only). All other combinations showed less endplate stress than did the control model. For fusion at L3-4 and degeneration at L4-5 , the stresses in the endplates at the adjacent level inferior to the fused disc decreased for both loading disc height reductions. Stresses in flexion decreased after fusion by 29.5% and 25.8% for degeneration I and II, respectively. Results for extension were similar. For fusion at L2-3 and degeneration at L4-5 , stresses in the endplates decreased more markedly at the degenerated (30%), than at the fused level (14%) in the presence of 25% disc height reduction and 10 Nm flexion, whereas in extension stresses decreased more at the fused (24.3%) than the degenerated level (5.86%). For fusion at L3-4 and degeneration at L2-3 , there were no increases in endplate stress in any scenario. For fusion at L4-5 and degeneration at L3-4 , progression of degeneration from I to II had a significant effect only in flexion. A dramatic increase in stress was noted in the endplates of the degenerated disc (L3-4 ) in flexion for degeneration II. Stresses are greater in flexion at the endplates of L3-4 and in flexion and extension at L2-3 in the presence of L3-4 disc disease and L4-5 fusion than in the control group. In all other combinations of fusion and disc disease, endplate stress was less for all levels tested than in the control model. © 2016 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

Small vertebral cross-sectional area and tall intervertebral disc in adolescent idiopathic scoliosis.

PubMed

Ponrartana, Skorn; Fisher, Carissa L; Aggabao, Patricia C; Chavez, Thomas A; Broom, Alexander M; Wren, Tishya A L; Skaggs, David L; Gilsanz, Vicente

2016-09-01

When compared to boys, girls have smaller vertebral cross-sectional area, which conveys a greater spinal flexibility, and a higher prevalence of adolescent idiopathic scoliosis. To test the hypothesis that small vertebral cross-sectional area and tall intervertebral disc height are structural characteristics of patients with adolescent idiopathic scoliosis. Using multiplanar imaging techniques, measures of vertebral cross-sectional area, vertebral height and intervertebral disc height in the lumbar spine were obtained in 35 pairs of girls and 11 pairs of boys with and without adolescent idiopathic scoliosis of the thoracic spine matched for age, height and weight. Compared to adolescents without spinal deformity, girls and boys with adolescent idiopathic scoliosis had, on average, 9.8% (6.68 ± 0.81 vs. 7.40 ± 0.99 cm(2); P = 0.0007) and 13.9% (8.22 ± 0.84 vs. 9.55 ± 1.61 cm(2); P = 0.009) smaller vertebral cross-sectional dimensions, respectively. Additionally, patients with adolescent idiopathic scoliosis had significantly greater values for intervertebral disc heights (9.06 ± 0.85 vs. 7.31 ± 0.62 mm and 9.09 ± 0.87 vs. 7.61 ± 1.00 mm for girls and boys respectively; both P ≤ 0.011). Multiple regression analysis indicated that the presence of scoliosis was negatively associated with vertebral cross-sectional area and positively with intervertebral disc height, independent of sex, age and body mass index. We provide new evidence that girls and boys with adolescent idiopathic scoliosis have significantly smaller vertebral cross-sectional area and taller intervertebral disc heights - two major structural determinants that influence trunk flexibility. With appropriate validation, these findings may have implications for the identification of children at the highest risk for developing scoliosis.

Comparison of pressure-controlled provocation discography using automated versus manual syringe pump manometry in patients with chronic low back pain.

PubMed

Derby, Richard; Lee, Sang Hoon; Lee, Jeong-Eun; Lee, Sang-Heon

2011-01-01

The study compares the rate of positive discograms using an automated versus a manual pressure-controlled injection devise and compares the pressure and volume values at various pressures and initial evoked pain and 6/10 or greater evoked pain. A retrospective study prospectively collected patient study data used in a prior prospective study and with prospectively collected data which is routinely collected per our institutional standardized audit protocol. Two custom-built disc manometers (automated injection speed control; manual injection speed control) were sequentially employed during provocation discography in 510 discs of 151 consecutive patients. Two hundred thirty-seven discs of 67 patients with chronic low back pain were evaluated using the automated manometer (automated group) and 273 discs of 84 patients were evaluated with a manual manometer (manual group). No significant differences in positive discogram rates were found between the automated and manual groups (32.1% vs 32.6% per disc, respectively, P>0.05). No significant differences in low-pressure positive discogram rates were found (16.0% vs 15.0% per disc, automated group versus manual group, respectively, P>0.05). However, there were significantly increased volumes and lower pressures at initial and "bad" pain provocation. The study results found equivalent positive discogram rates following a series of pressure-controlled discography using either an automated or manual pressure devise. There were, however significant increases in volume at both initial onset of evoked pain and at 6/10 pain when using the automated injection devise that may have caused the observed lower opening pressure and lower pressure values at initial evoked pain. Assuming increased volumes are innocuous, automated injection is inherently more controlled and may better reduce unintended and often unrecorded spurious high dynamic pressure peaks thereby reducing conscious and unconscious operator bias. Wiley Periodicals, Inc.

Simple, miniaturized blood plasma extraction method.

PubMed

Kim, Jin-Hee; Woenker, Timothy; Adamec, Jiri; Regnier, Fred E

2013-12-03

A rapid plasma extraction technology that collects a 2.5 μL aliquot of plasma within three minutes from a finger-stick derived drop of blood was evaluated. The utility of the plasma extraction cards used was that a paper collection disc bearing plasma was produced that could be air-dried in fifteen minutes and placed in a mailing envelop for transport to an analytical laboratory. This circumvents the need for venipuncture and blood collection in specialized vials by a phlebotomist along with centrifugation and refrigerated storage. Plasma extraction was achieved by applying a blood drop to a membrane stack through which plasma was drawn by capillary action. During the course of plasma migration to a collection disc at the bottom of the membrane stack blood cells were removed by a combination of adsorption and filtration. After the collection disc filled with an aliquot of plasma the upper membranes were stripped from the collection card and the collection disc was air-dried. Intercard differences in the volume of plasma collected varied approximately 1% while volume variations of less than 2% were seen with hematocrit levels ranging from 20% to 71%. Dried samples bearing metabolites and proteins were then extracted from the disc and analyzed. 25-Hydroxy vitamin D was quantified by LC-MS/MS analysis following derivatization with a secosteroid signal enhancing tag that imparted a permanent positive charge to the vitamin and reduced the limit of quantification (LOQ) to 1 pg of collected vitamin on the disc; comparable to values observed with liquid-liquid extraction (LLE) of a venipuncture sample. A similar study using conventional proteomics methods and spectral counting for quantification was conducted with yeast enolase added to serum as an internal standard. The LOQ with extracted serum samples for enolase was 1 μM, linear from 1 to 40 μM, the highest concentration examined. In all respects protein quantification with extracted serum samples was comparable to that observed with serum samples obtained by venipuncture.

Lunar-forming impacts: processes and alternatives

PubMed Central

Canup, R. M.

2014-01-01

The formation of a protolunar disc by a giant impact with the early Earth is discussed, focusing on two classes of impacts: (i) canonical impacts, in which a Mars-sized impactor produces a planet–disc system whose angular momentum is comparable to that in the current Earth and Moon, and (ii) high-angular-momentum impacts, which produce a system whose angular momentum is approximately a factor of 2 larger than that in the current Earth and Moon. In (i), the disc originates primarily from impactor-derived material and thus is expected to have an initial composition distinct from that of the Earth's mantle. In (ii), a hotter, more compact initial disc is produced with a silicate composition that can be nearly identical to that of the silicate Earth. Both scenarios require subsequent processes for consistency with the current Earth and Moon: disc–planet compositional equilibration in the case of (i), or large-scale angular momentum loss during capture of the newly formed Moon into the evection resonance with the Sun in the case of (ii). PMID:25114302

Solid-phase extraction and on-disc derivatization of the major benzodiazepines in urine using enzyme hydrolysis and Toxi-Lab VC MP3 column.

PubMed

King, J W; King, L J

1996-01-01

Because of the increase in use of the newer benzodiazepines, we explored the opportunity to develop a gas chromatographic-mass spectrometric (GC-MS) method that encompasses most of the widely prescribed benzodiazepines in use today. The benzodiazepines included in our study are nordiazepam, oxazepam, temazepam, lorazepam, alpha-hydroxyalprazolam, alpha-hydroxytriazolam, desalkylflurazepam, and 2-hydroxyethylflurazepam. Using 1.0 mL of urine as the matrix, we added the enzyme Glusulase and incubated the specimens for 2 h to obtain the free drugs. The hydrolyzed samples were then loaded onto a Toxi-Lab Spec VC MP3 column containing a 15-mg disc. On-disc derivatization was accomplished by adding N-methyl-N-(t-butyldimethylsilyl) trifluroacetamide (MTBSTFA) with 1% TBDMSCI to the disc. The derivatives were then placed in a GC vial and analyzed by GC-MS in the selected ion monitoring mode. These results were then compared to confirmed positives by the traditional acid hydrolysis GC-MS method.

Size matters: Perceived depth magnitude varies with stimulus height.

PubMed

Tsirlin, Inna; Wilcox, Laurie M; Allison, Robert S

2016-06-01

Both the upper and lower disparity limits for stereopsis vary with the size of the targets. Recently, Tsirlin, Wilcox, and Allison (2012) suggested that perceived depth magnitude from stereopsis might also depend on the vertical extent of a stimulus. To test this hypothesis we compared apparent depth in small discs to depth in long bars with equivalent width and disparity. We used three estimation techniques: a virtual ruler, a touch-sensor (for haptic estimates) and a disparity probe. We found that depth estimates were significantly larger for the bar stimuli than for the disc stimuli for all methods of estimation and different configurations. In a second experiment, we measured perceived depth as a function of the height of the bar and the radius of the disc. Perceived depth increased with increasing bar height and disc radius suggesting that disparity is integrated along the vertical edges. We discuss size-disparity correlation and inter-neural excitatory connections as potential mechanisms that could account for these results. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Spectrum of Optic Disc Ischemia in Patients Younger than 50 Years (An Amercian Ophthalmological Society Thesis)

PubMed Central

Arnold, Anthony C.; Costa, Roberta M. S.; Dumitrascu, Oana M.

2013-01-01

Purpose: To identify the spectrum of clinical and fluorescein angiographic features of optic disc ischemia in patients younger than 50 years. Methods: This retrospective comparative case series from a university consultative neuro-ophthalmology practice consisted of two phases. The first compared 108 cases of nonarteritic anterior ischemic optic neuropathy in patients younger than 50 years (NAIONy) to a cohort of 108 cases in patients 50 years or older (NAIONo). Predisposing risk factors, fluorescein angiographic features, and clinical course were compared. In the second phase, 12 cases of diabetic papillopathy under age 50 were assessed by fluorescein angiographic criteria for evidence of optic disc ischemia and compared to patients with NAIONy. Results: NAIONy comprised 108 (12.7%) of 848 NAION cases reviewed. Chronic renal failure with dialysis and migraine were more common in NAIONy. Fellow eye involvement rate was significantly higher for NAIONy patients (46/108, 42.6%) than for NAIONo patients (32/108, 29.6%). Fluorescein angiographic features of ischemia were documented in 44 (81.5%) of 54 eyes studied. In one case, these features were documented in pre-NAION edema. Diabetic papillopathy demonstrated delayed filling consistent with ischemia in 7 of 10 (70.0%), without significant visual field loss. Conclusions: Ischemic optic neuropathy in patients younger than 50 years is not rare. Fellow eye involvement is more frequent in younger patients. Fluorescein angiography confirmation of impaired perfusion in multiple syndromes of optic neuropathy corroborates a spectrum of optic disc ischemia ranging from perfusion delay without visual loss to severely impaired perfusion and visual loss and incorporates optic neuropathies previously considered nonischemic. PMID:24167327

Percutaneous laser disc decompression versus conventional microdiscectomy in sciatica: a randomized controlled trial.

PubMed

Brouwer, Patrick A; Brand, Ronald; van den Akker-van Marle, M Elske; Jacobs, Wilco C H; Schenk, Barry; van den Berg-Huijsmans, Annette A; Koes, Bart W; van Buchem, M A; Arts, Mark P; Peul, Wilco C

2015-05-01

Percutaneous laser disc decompression (PLDD) is a minimally invasive treatment for lumbar disc herniation, with Food and Drug Administration approval since 1991. However, no randomized trial comparing PLDD to conventional treatment has been performed. In this trial, we assessed the effectiveness of a strategy of PLDD as compared with conventional surgery. This randomized prospective trial with a noninferiority design was carried out in two academic and six teaching hospitals in the Netherlands according to an intent-to-treat protocol with full institutional review board approval. One hundred fifteen eligible surgical candidates, with sciatica from a disc herniation smaller than one-third of the spinal canal, were included. The main outcome measures for this trial were the Roland-Morris Disability Questionnaire for sciatica, visual analog scores for back and leg pain, and the patient's report of perceived recovery. Patients were randomly allocated to PLDD (n=57) or conventional surgery (n=58). Blinding was impossible because of the nature of the interventions. This study was funded by the Healthcare Insurance Board of the Netherlands. The primary outcome, Roland-Morris Disability Questionnaire, showed noninferiority of PLDD at 8 (-0.1; [95% confidence interval (CI), -2.3 to 2.1]) and 52 weeks (-1.1; 95% CI, -3.4 to 1.1) compared with conventional surgery. There was, however, a higher speed of recovery in favor of conventional surgery (hazard ratio, 0.64 [95% CI, 0.42-0.97]). The number of reoperations was significantly less in the conventional surgery group (38% vs. 16%). Overall, a strategy of PLDD, with delayed surgery if needed, resulted in noninferior outcomes at 1 year. At 1 year, a strategy of PLDD, followed by surgery if needed, resulted in noninferior outcomes compared with surgery. Copyright © 2015 Elsevier Inc. All rights reserved.

Elimination of Subsidence with 26-mm-Wide Cages in Extreme Lateral Interbody Fusion.

PubMed

Lang, Gernot; Navarro-Ramirez, Rodrigo; Gandevia, Lena; Hussain, Ibrahim; Nakhla, Jonathan; Zubkov, Micaella; Härtl, Roger

2017-08-01

Extreme lateral interbody fusion (ELIF) has gained popularity as a minimally invasive technique for indirect decompression. However, graft subsidence potentially threatens long-term success of ELIF. This study evaluated whether 26-mm-wide cages can eliminate subsidence and subsequent loss of decompression in ELIF. Patients undergoing ELIF surgery using a 26-mm-wide cage were analyzed retrospectively. Patient demographics and perioperative data for radiographic and clinical outcomes were recorded. Radiographic parameters included regional sagittal lumbar lordosis and foraminal and disc height. Clinical parameters were evaluated using the Oswestry Disability Index and visual analog scale. Subsidence of 26-mm-wide cages was compared with previous outcomes of patients undergoing ELIF using 18-mm-wide and 22-mm-wide cages. There were 21 patients and 28 spinal segments analyzed. Radiographic outcome measures such as disc and foraminal height revealed significant improvement at follow-up compared with before surgery (P = 0.001). Postoperative to last follow-up cage subsidence translated into 0.34 mm ± 0.26 and -0.55 mm ± 0.64 in disc and foraminal height loss, respectively. Patients with 26-mm-wide cages experienced less subsidence by means of disc (26 mm vs. 18 mm and 22 mm, P ≤ 0.05) and foraminal height (26 mm vs. 18 mm, P = 0.005; 26 mm vs. 22 mm, P = 0.208) loss compared with patients receiving 18-mm-wide and 22-mm-wide cages. The 26-mm-wide cages almost eliminated cage subsidence in ELIF. Compared with 18-mm-wide and 22-mm-wide cages, 26-mm-wide cages significantly reduced cage subsidence in ELIF at midterm follow-up. A 26-mm-wide cage should be used in ELIF to achieve sustained indirect decompression. Copyright © 2017. Published by Elsevier Inc.

The role of rigid vs. dynamic instrumentation for stabilization of the degenerative lumbosacral spine.

PubMed

Korovessis, Panagiotis; Papazisis, Zisis; Lambiris, Elias

2002-01-01

This is a prospective comparative randomised study to compare the immediately postoperative effects of a rigid versus dynamic instrumentation for degenerative spine disease and stenosis on the standing sagittal lumbar spine alignment and to investigate if a dynamic spine system can replace the commonly used rigid systems in order to avoid the above mentioned disadvantages of rigid fixation. 15 randomly selected patients received the rigid instrumentation SCS and an equal number of randomly selected patients the dynamic TWINFLEX device for spinal stenosis associated degenerative lumbar disease. The age of the patients, who received rigid and dynamic instrumentation was 65 +/- 9 years and 62 +/- 10 years respectively. All patients had standing spine radiographs preoperatively and three months postoperatively. The parameters that were measured and compared pre- to postoperatively were: lumbar lordosis (L1-S1), total lumbar lordosis (T12-S1), sacral tilt, distal lordosis (L4-S1), intervertebral angulation, vertebral inclination and disc index. The instrumented levels in the spines that received rigid and dynamic instrumentation were 3.5 +/- 0.53 and 3 +/- 0.7 respectively. The instrumented levels from L3 to L5 were 23, the lumbosacral junction was instrumented in 3 patients of group A and in 4 patients of group B. Lumbar lordosis did not significantly change postoperatively, while total lordosis was significantly (P=0.04) increased in the patients who received the rigid instrumentation, while it was significantly (P=0.012) decreased in the group B. Intervertebral angulation of the non-instrumented level L1-L2 was increased in the group A (P=0.01), while the dynamic instrumentation increased (P=0.02) the intervertebral inclination of the adjacent level L2-L3, immediately above the uppermost instrumented level. Distal lordosis and sacral tilt did not change in any patient in both groups. Both instrumentations did not change the lateral vertebral inclination of L1 to L5 vertebrae. Rigid instrumentation increased the lordotic inclination of L5 (P=0.03) and of S1 (P=0.03). Rigid instrumentation increased (P=0.04) the intervertebral angulation at the uppermost instrumented level L3-L4 The most significant change in vertebral angulation was achieved at the instrumented level L4-L5 by the dynamic (P=0.007) and rigid (0.05). The disc index at the level L2-L3 was increased by both instrumentation [dynamic P=0.007 and rigid (P=0.02)]. The index L3-L4 was increased following dynamic fixation (P=0.0007). The disc index L4-L5 was postoperatively increased by both types of instrumentation (rigid P=0.006, dynamic P=0.02). The disc index L5-S1 did not significantly change postoperatively by either system. Both rigid and dynamic instrumentations restored lumbar lordosis, sacral tilt, distal lordosis and increased the foraminal diameter at the level L4-L5 resulting in an indirect decompression of the nerve roots at this level . Both rigid and dynamic instrumentations applied in the lumbosacral spine to treat degenerative disease secured L3 to S1 sagittal spine profile close to preoperative levels, that should theoretically guarantee a pain-free postoperative course. This study supports the belief that the dynamic system can be used with the same indications with the rigid in degenerative lumbar spine because it can offer equally good short-term results regarding sagittal spine alignment while simultaneously it has the previously mentioned advantages (avoidance stress shielding etc).

Scattering from randomly oriented circular discs with application to vegetation

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.

1984-01-01

A vegetation layer is modeled by a collection of randomly oriented circular discs over a half space. The backscattering coefficient from such a half space is computed using the radiative transfer theory. It is shown that significantly different results are obtained from this theory as compared with some earlier investigations using the same modeling approach but with restricted disc orientations. In particular, the backscattered cross polarized returns cannot have a fast increasing angular trend which is inconsistent with measurements. By setting the appropriate angle of orientation to zero the theory reduces to previously published results. Comparisons are shown with measurements taken from milo, corn and wheat and good agreements are obtained for both polarized and cross polarized returns.

Scattering from randomly oriented circular discs with application to vegetation

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.

1983-01-01

A vegetation layer is modeled by a collection of randomly oriented circular discs over a half space. The backscattering coefficient from such a half space is computed using the radiative transfer theory. It is shown that significantly different results are obtained from this theory as compared with some earlier investigations using the same modeling approach but with restricted disc orientations. In particular, the backscattered cross-polarized returns cannot have a fast increasing angular trend which is inconsistent with measurements. By setting the appropriate angle of orientation to zero the theory reduces to previously published results. Comparisons are shown with measurements taken from milo, corn and wheat and good agreements are obtained for both polarized and cross-polarized returns.

Prospective, Randomized Comparison of Cervical Total Disk Replacement Versus Anterior Cervical Fusion: Results at 48 Months Follow-up.

PubMed

Hisey, Michael S; Bae, Hyun W; Davis, Reginald J; Gaede, Steven; Hoffman, Greg; Kim, Kee D; Nunley, Pierce D; Peterson, Daniel; Rashbaum, Ralph F; Stokes, John; Ohnmeiss, Donna D

2015-05-01

This was a prospective, randomized, controlled multicenter trial. The purpose of this study was to compare clinical outcomes at 4-year follow-up of patients receiving cervical total disk replacement (TDR) with those receiving anterior cervical discectomy and fusion (ACDF). ACDF has been the traditional treatment for symptomatic disk degeneration. Several studies found single-level TDR to be as safe and effective as ACDF at ≥2 years follow-up. Patients from 23 centers were randomized in a 2:1 ratio with 164 receiving the investigational device (Mobi-C Cervical Disc Prosthesis) and 81 receiving ACDF using an anterior plate and allograft. Patients were evaluated preoperatively and 6 weeks, 3, 6, 12, 18, 24, 36, and 48 months postoperatively. Outcome assessments included a composite success score, Neck Disability Index, visual analog scales assessing neck and arm pain, patient satisfaction, major complications, subsequent surgery, segmental range of motion, and adjacent-segment degeneration. The composite success rate was similar in the 2 groups at 48-month follow-up. Mean Neck Disability Index, visual analog scale, and SF-12 scores were significantly improved in early follow-up in both groups with improvements maintained throughout 48 months. On some measures, TDR had significantly greater improvement during early follow-up. At no follow-up were TDR scores significantly worse than ACDF scores. Subsequent surgery rate was significantly higher for ACDF compared with TDR (9.9% vs. 3.0%, P<0.05). Range of motion was maintained with TDR having a mean baseline value of 8 degrees compared with 10 degrees at 48 months. The incidence of adjacent-segment degeneration was significantly higher with ACDF at inferior and superior segments compared with TDR (inferior: 50% vs. 30%, P<0.025; superior: 53% vs. 34%, P<0.025). Significant improvements were observed in pain and function. TDR patients maintained motion and had significantly lower rates of reoperation and adjacent-segment degeneration compared with ACDF. This study supports the safety and efficacy of TDR in appropriately selected patients.

[Research progress of intervertebral disc endogenous stem cells for intervertebral disc regeneration].

PubMed

Liang, Hang; Deng, Xiangyu; Shao, Zengwu

2017-10-01

To summarize the research progress of intervertebral disc endogenous stem cells for intervertebral disc regeneration and deduce the therapeutic potential of endogenous repair for intervertebral disc degeneration. The original articles about intervertebral disc endogenous stem cells for intervertebral disc regeneration were extensively reviewed; the reparative potential in vivo and the extraction and identification in vitro of intervertebral disc endogenous stem cells were analyzed; the prospect of endogenous stem cells for intervertebral disc regeneration was predicted. Stem cell niche present in the intervertebral discs, from which stem cells migrate to injured tissues and contribute to tissues regeneration under certain specific microenvironment. Moreover, the migration of stem cells is regulated by chemokines system. Tissue specific progenitor cells have been identified and successfully extracted and isolated. The findings provide the basis for biological therapy of intervertebral disc endogenous stem cells. Intervertebral disc endogenous stem cells play a crucial role in intervertebral disc regeneration. Therapeutic strategy of intervertebral disc endogenous stem cells is proven to be a promising biological approach for intervertebral disc regeneration.

Eyes with Suspicious Appearance of the Optic Disc and Normal Intraocular Pressure: Using Clinical and Epidemiological Characteristics to Differentiate Those with and without Glaucoma.

PubMed

Dias, Diego T; Ushida, Michele; Sousa, Marina C; Dorairaj, Syril; Biteli, Luis G; Leite, Mauro T; Paranhos, Augusto; Prata, Tiago S

2016-01-01

Among all glaucoma suspects, eyes with optic nerve head features suspicious or suggestive of early glaucoma are probably those that offer the greatest challenge for clinicians. In contrast with the robust longitudinal data published on ocular hypertension, there is no specific management guideline for these patients. Therefore, evaluating eyes with suspicious optic disc appearance and normal intraocular pressure (IOP), we sought to investigate potential differences in clinical and epidemiological characteristics to differentiate those with normal-tension glaucoma (NTG) from those with presumed large physiological optic disc cups (pLPC). In this observational case-control study, we consecutively enrolled individuals with pLPC and NTG. All eyes had vertical cup-to-disc ratio (VCDR)≥0.6 and untreated IOP<21 mmHg. Glaucomatous eyes had reproducible visual field defects. Eyes with pLPC required normal visual fields and ≥30 months of follow-up with no evidence of glaucomatous neuropathy. Clinical and epidemiological parameters were compared between groups. Eighty-four individuals with pLPC and 40 NTG patients were included. Regarding our main results, NTG patients were significantly older and with a higher prevalence of Japanese descendants (p<0.01). Not only did pLPC eyes have smaller mean VCDR, but also larger optic discs (p≤0.04). There were no significant differences for gender, central corneal thickness, and spherical equivalent (p≥0.38). Significant odds ratios (OR) were found for race (OR = 2.42; for Japanese ancestry), age (OR = 1.05), VCDR (OR = 5.03), and disc size (OR = 0.04; p≤0.04). In conclusion, in patients with suspicious optic disc and normal IOP, those with older age, Japanese ancestry, smaller optic discs, and larger VCDR are more likely to have NTG, and therefore, deserve deeper investigation and closer monitoring.

The bending stress distribution in bilayered and graded zirconia-based dental ceramics

PubMed Central

Fabris, Douglas; Souza, Júlio C.M.; Silva, Filipe S.; Fredel, Márcio; Mesquita-Guimarães, Joana; Zhang, Yu; Henriques, Bruno

2016-01-01

The purpose of this study was to evaluate the biaxial flexural stresses in classic bilayered and in graded zirconia-feldspathic porcelain composites. A finite element method and an analytical model were used to simulate the piston-on-ring test and to predict the biaxial stress distributions across the thickness of the bilayer and graded zirconia-feldspathic porcelain discs. An axisymmetric model and a flexure formula of Hsueh et al. were used in the FEM and analytical analysis, respectively. Four porcelain thicknesses were tested in the bilayered discs. In graded discs, continuous and stepwise transitions from the bottom zirconia layer to the top porcelain layer were studied. The resulting stresses across the thickness, measured along the central axis of the disc, for the bilayered and graded discs were compared. In bilayered discs, the maximum tensile stress decreased while the stress mismatch (at the interface) increased with the porcelain layer thickness. The optimized balance between both variables is achieved for a porcelain thickness ratio in the range of 0.30–0.35. In graded discs, the highest tensile stresses were registered for porcelain rich interlayers (p=0.25) whereas the zirconia rich ones (p=8) yield the lowest tensile stresses. In addition, the maximum stresses in a graded structure can be tailored by altering compositional gradients. A decrease in maximum stresses with increasing values of p (a scaling exponent in the power law function) was observed. Our findings showed a good agreement between the analytical and simulated models, particularly in the tensile region of the disc. Graded zirconia-feldspathic porcelain composites exhibited a more favourable stress distribution relative to conventional bilayered systems. This fact can significantly impact the clinical performance of zirconia-feldspathic porcelain prostheses, namely reducing the fracture incidence of zirconia and the chipping and delamination of porcelain. PMID:28104926

Metallicity of solar-type stars with debris discs and planets⋆

NASA Astrophysics Data System (ADS)

Maldonado, J.; Eiroa, C.; Villaver, E.; Montesinos, B.; Mora, A.

2012-05-01

Context. Around 16% of the solar-like stars in our neighbourhood show IR-excesses due to dusty debris discs and a fraction of them are known to host planets. Determining whether these stars follow any special trend in their properties is important to understand debris disc and planet formation. Aims: We aim to determine in a homogeneous way the metallicity of a sample of stars with known debris discs and planets. We attempt to identify trends related to debris discs and planets around solar-type stars. Methods: Our analysis includes the calculation of the fundamental stellar parameters Teff, log g, microturbulent velocity, and metallicity by applying the iron ionisation equilibrium conditions to several isolated Fe i and Fe ii lines. High-resolution échelle spectra (R ~ 57 000) from 2, 3 m class telescopes are used. Our derived metallicities are compared with other results in the literature, which finally allows us to extend the stellar samples in a consistent way. Results: The metallicity distributions of the different stellar samples suggest that there is a transition toward higher metallicities from stars with neither debris discs nor planets to stars hosting giant planets. Stars with debris discs and stars with neither debris nor planets follow a similar metallicity distribution, although the distribution of the first ones might be shifted towards higher metallicities. Stars with debris discs and planets have the same metallicity behaviour as stars hosting planets, irrespective of whether the planets are low-mass or gas giants. In the case of debris discs and giant planets, the planets are usually cool, - semimajor axis larger than 0.1 AU (20 out of 22 planets), even ≈65% have semimajor axis larger than 0.5 AU. The data also suggest that stars with debris discs and cool giant planets tend to have a low dust luminosity, and are among the less luminous debris discs known. We also find evidence of an anticorrelation between the luminosity of the dust and the planet eccentricity. Conclusions: Our data show that the presence of planets, not the debris disc, correlates with the stellar metallicity. The results confirm that core-accretion models represent suitable scenarios for debris disc and planet formation. These conclusions are based on a number of stars with discs and planets considerably larger than in previous works, in particular stars hosting low-mass planets and debris discs. Dynamical instabilities produced by eccentric giant planets could explain the suggested dust luminosity trends observed for stars with debris discs and planets. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC); observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica); observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias; and data obtained from the ESO Science Archive Facility.Full Tables 1 and 5 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/541/A40

Morphological and biochemical studies of the elastic fibres in the craniomandibular joint articular disc of the tight-skin mouse.

PubMed

O'dell, N L; Burlison, S K; Starcher, B C; Pennington, C B

1996-05-01

The tight-skin (TSK) mouse is characterized by the hyperplasia of loose connective tissues, and of excessive growth of cartilage and of bones including the mandible. Since the fibroelastic connective tissues of the craniomandibular joint (CMJ) are essential to the functions of this joint, the present histological study compared the presence and general distribution of elastic fibres in CMJ discal tissues of TSK and normal mice. The excised CMJs were processed for light microscopy. The tissues were fixed, demineralized, embedded in paraffin, sectioned and then stained with resorcin-fuchsin to demonstrate elastic fibres. There were no obvious histological differences in either the amount or the distribution of elastic fibres in the discs from the two groups. In both groups, elastic fibres were found in the disc and in many of the attachments of the disc to the mandible and squamosal bone. In addition to the morphological preparations, articular discs and samples of lung tissue were excised from other mice and subjected to a radioimmunoassay for desmosine in order to estimate the amounts of elastin in these tissues; the amount of elastin was significantly reduced in the TSK lung, but the amounts of elastin in the TSK and normal CMJ discal tissues were not significantly different statistically. These morphological and histochemical results suggest that the distribution and quantity of elastic fibres in the TSK mouse disc are not significantly different from those in the normal mouse articular disc. Moreover, these data may be interpreted to either suggest a differential effect on the elastic fibres in different TSK tissues, or to support the suggestion that abnormal degradation of elastic fibres may not be characteristic of the TSK mouse.

Shaken and stirred: the effects of turbulence and rotation on disc and outflow formation during the collapse of magnetized molecular cloud cores

NASA Astrophysics Data System (ADS)

Lewis, Benjamin T.; Bate, Matthew R.

2018-07-01

We present the results of 18 magnetohydrodynamical calculations of the collapse of a molecular cloud core to form a protostar. Some calculations include radiative transfer in the flux-limited diffusion approximation, while others employ a barotropic equation of state. We cover a wide parameter space, with mass-to-flux ratios ranging from μ = 5 to 20; initial turbulent amplitudes ranging from a laminar calculation (i.e. where the Mach number, M = 0) to transonic M = 1; and initial rotation rates from βrot = 0.005 to 0.02. We first show that using a radiative transfer scheme produces warmer pseudo-discs than the barotropic equation of state, making them more stable. We then `shake' the core by increasing the initial turbulent velocity field, and find that at all three mass-to-flux ratios transonic cores are weakly bound and do not produce pseudo-discs; M = 0.3 cores produce very disrupted discs; and M = 0.1 cores produce discs broadly comparable to a laminar core. In our previous paper, we showed that a pseudo-disc coupled with sufficient magnetic field is necessary to form a bipolar outflow. Here, we show that only weakly turbulent cores exhibit collimated jets. We finally take the M = 1.0, μ = 5 core and `stir' it by increasing the initial angular momentum, finding that once the degree of rotational energy exceeds the turbulent energy in the core the disc returns, with a corresponding (though slower), outflow. These conclusions place constraints on the initial mixtures of rotation and turbulence in molecular cloud cores which are conducive to the formation of bipolar outflows early in the star formation process.

Neurophysiological modification of CA1 pyramidal neurons in a transgenic mouse expressing a truncated form of disrupted-in-schizophrenia 1

PubMed Central

Booth, Clair A; Brown, Jonathan T; Randall, Andrew D

2014-01-01

A t(1;11) balanced chromosomal translocation transects the Disc1 gene in a large Scottish family and produces genome-wide linkage to schizophrenia and recurrent major depressive disorder. This study describes our in vitro investigations into neurophysiological function in hippocampal area CA1 of a transgenic mouse (DISC1tr) that expresses a truncated version of DISC1 designed to reproduce aspects of the genetic situation in the Scottish t(1;11) pedigree. We employed both patch-clamp and extracellular recording methods in vitro to compare intrinsic properties and synaptic function and plasticity between DISC1tr animals and wild-type littermates. Patch-clamp analysis of CA1 pyramidal neurons (CA1-PNs) revealed no genotype dependence in multiple subthreshold parameters, including resting potential, input resistance, hyperpolarization-activated ‘sag’ and resonance properties. Suprathreshold stimuli revealed no alteration to action potential (AP) waveform, although the initial rate of AP production was higher in DISC1tr mice. No difference was observed in afterhyperpolarizing potentials following trains of 5–25 APs at 50 Hz. Patch-clamp analysis of synaptic responses in the Schaffer collateral commissural (SC) pathway indicated no genotype-dependence of paired pulse facilitation, excitatory postsynaptic potential summation or AMPA/NMDA ratio. Extracellular recordings also revealed an absence of changes to SC synaptic responses and indicated input–output and short-term plasticity were also unaltered in the temporoammonic (TA) input. However, in DISC1tr mice theta burst-induced long-term potentiation was enhanced in the SC pathway but completely lost in the TA pathway. These data demonstrate that expressing a truncated form of DISC1 affects intrinsic properties of CA1-PNs and produces pathway-specific effects on long-term synaptic plasticity. PMID:24712988

High-resolution imaging of the retinal nerve fiber layer in normal eyes using adaptive optics scanning laser ophthalmoscopy.

PubMed

Takayama, Kohei; Ooto, Sotaro; Hangai, Masanori; Arakawa, Naoko; Oshima, Susumu; Shibata, Naohisa; Hanebuchi, Masaaki; Inoue, Takashi; Yoshimura, Nagahisa

2012-01-01

To conduct high-resolution imaging of the retinal nerve fiber layer (RNFL) in normal eyes using adaptive optics scanning laser ophthalmoscopy (AO-SLO). AO-SLO images were obtained in 20 normal eyes at multiple locations in the posterior polar area and a circular path with a 3-4-mm diameter around the optic disc. For each eye, images focused on the RNFL were recorded and a montage of AO-SLO images was created. AO-SLO images for all eyes showed many hyperreflective bundles in the RNFL. Hyperreflective bundles above or below the fovea were seen in an arch from the temporal periphery on either side of a horizontal dividing line to the optic disc. The dark lines among the hyperreflective bundles were narrower around the optic disc compared with those in the temporal raphe. The hyperreflective bundles corresponded with the direction of the striations on SLO red-free images. The resolution and contrast of the bundles were much higher in AO-SLO images than in red-free fundus photography or SLO red-free images. The mean hyperreflective bundle width around the optic disc had a double-humped shape; the bundles at the temporal and nasal sides of the optic disc were narrower than those above and below the optic disc (P<0.001). RNFL thickness obtained by optical coherence tomography correlated with the hyperreflective bundle widths on AO-SLO (P<0.001) AO-SLO revealed hyperreflective bundles and dark lines in the RNFL, believed to be retinal nerve fiber bundles and Müller cell septa. The widths of the nerve fiber bundles appear to be proportional to the RNFL thickness at equivalent distances from the optic disc.

Detecting a rotation in the ɛ Eridani debris disc

NASA Astrophysics Data System (ADS)

Poulton, C. J.; Greaves, J. S.; Collier Cameron, A.

2006-10-01

The evidence for a rotation of the ɛ Eridani debris disc is examined. Data at 850-μm wavelength were previously obtained using the Submillimetre Common User Bolometer Array (SCUBA) over periods of 1997-1998 and 2000-2002. By χ2 fitting after shift and rotation operations, images from these two epochs were compared to recover proper motion and orbital motion of the disc. The same procedures were then performed on simulated images to estimate the accuracy of the results. Minima in the χ2 plots indicate a motion of the disc of approximately 0.6 arcsec per year in the direction of the star's proper motion. This underestimates the true value of 1 arcsec per year, implying that some of the structure in the disc region is not associated with ɛ Eridani, originating instead from background galaxies. From the χ2 fitting for orbital motion, a counterclockwise rotation rate of per year is deduced. Comparisons with simulated data in which the disc is not rotating show that noise and background galaxies result in approximately Gaussian fluctuations with a standard deviation of per year. Thus, counterclockwise rotation of disc features is supported at approximately a 2σ level, after a 4-yr time difference. This rate is faster than the Keplerian rate of per year for features at ~65 au from the star, suggesting their motion is tracking a planet inside the dust ring. Future observations with SCUBA-2 can rule out no rotation of the ɛ Eridani dust clumps with ~4σ confidence. Assuming a rate of about per year, the rotation of the features after a 10-yr period could be shown to be >=1° per year at the 3σ level.

Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers

NASA Astrophysics Data System (ADS)

Lippuner, Jonas; Fernández, Rodrigo; Roberts, Luke F.; Foucart, Francois; Kasen, Daniel; Metzger, Brian D.; Ott, Christian D.

2017-11-01

We investigate the nucleosynthesis of heavy elements in the winds ejected by accretion discs formed in neutron star mergers. We compute the element formation in disc outflows from hypermassive neutron star (HMNS) remnants of variable lifetime, including the effect of angular momentum transport in the disc evolution. We employ long-term axisymmetric hydrodynamic disc simulations to model the ejecta, and compute r-process nucleosynthesis with tracer particles using a nuclear reaction network containing ∼8000 species. We find that the previously known strong correlation between HMNS lifetime, ejected mass and average electron fraction in the outflow is directly related to the amount of neutrino irradiation on the disc, which dominates mass ejection at early times in the form of a neutrino-driven wind. Production of lanthanides and actinides saturates at short HMNS lifetimes (≲10 ms), with additional ejecta contributing to a blue optical kilonova component for longer-lived HMNSs. We find good agreement between the abundances from the disc outflow alone and the solar r-process distribution only for short HMNS lifetimes (≲10 ms). For longer lifetimes, the rare-earth and third r-process peaks are significantly underproduced compared to the solar pattern, requiring additional contributions from the dynamical ejecta. The nucleosynthesis signature from a spinning black hole (BH) can only overlap with that from an HMNS of moderate lifetime (≲60 ms). Finally, we show that angular momentum transport not only contributes with a late-time outflow component, but that it also enhances the neutrino-driven component by moving material to shallower regions of the gravitational potential, in addition to providing additional heating.

Small Interfering RNA-Mediated Suppression of Fas Modulate Apoptosis and Proliferation in Rat Intervertebral Disc Cells.

PubMed

Park, Jong-Beom; Park, Chanjoo

2017-10-01

In vitro cell culture model. To investigate the effect of small interfering RNA (siRNA) on Fas expression, apoptosis, and proliferation in serum-deprived rat disc cells. Synthetic siRNA can trigger an RNA interference (RNAi) response in mammalian cells and precipitate the inhibition of specific gene expression. However, the potential utility of siRNA technology in downregulation of specific genes associated with disc cell apoptosis remains unclear. Rat disc cells were isolated and cultured in the presence of either 10% fetal bovine serum (FBS) (normal control) or 0% FBS (serum deprivation to induce apoptosis) for 48 hours. Fas expression, apoptosis, and proliferation were determined. Additionally, siRNA oligonucleotides against Fas (Fas siRNA) were transfected into rat disc cells to suppress Fas expression. Changes in Fas expression were assessed by reverse transcription-polymerase chain reaction and semiquantitatively analyzed using densitometry. The effect of Fas siRNA on apoptosis and proliferation of rat disc cells were also determined. Negative siRNA and transfection agent alone (Mock) were used as controls. Serum deprivation increased apoptosis by 40.3% ( p <0.001), decreased proliferation by 45.3% ( p <0.001), and upregulated Fas expression. Additionally, Fas siRNA suppressed Fas expression in serum-deprived cultures, with 68.5% reduction at the mRNA level compared to the control cultures ( p <0.001). Finally, Fas siRNA-mediated suppression of Fas expression significantly inhibited apoptosis by 9.3% and increased proliferation by 21% in serum-deprived cultures ( p <0.05 for both). The observed dual positive effect of Fas siRNA might be a powerful therapeutic approach for disc degeneration by suppression of harmful gene expression.

SEM evaluation of human gingival fibroblasts growth onto CAD/CAM zirconia and veneering ceramic for zirconia

PubMed Central

Zizzari, Vincenzo; Borelli, Bruna; De Colli, Marianna; Tumedei, Margherita; Di Iorio, Donato; Zara, Susi; Sorrentino, Roberto; Cataldi, Amelia; Gherlone, Enrico Felice; Zarone, Fernando; Tetè, Stefano

2013-01-01

Summary Aim To evaluate the growth of Human Gingival Fibroblasts (HGFs) cultured onto sample discs of CAD/CAM zirconia and veneering ceramic for zirconia by means of Scanning Electron Microscope (SEM) analysis at different experimental times. Methods A total of 26 experimental discs, divided into 2 groups, were used: Group A) CAD/CAM zirconia (3Y-TZP) discs (n=13); Group B) veneering ceramic for zirconia discs (n=13). HGFs were obtained from human gingival biopsies, isolated and placed in culture plates. Subsequently, cells were seeded on experimental discs at 7,5×103/cm2 concentration and cultured for a total of 7 days. Discs were processed for SEM observation at 3h, 24h, 72h and 7 days. Results In Group A, after 3h, HGFs were adherent to the surface and showed a flattened profile. The disc surface covered by HGFs resulted to be wider in Group A than in Group B samples. At SEM observation, after 24h and 72h, differences in cell attachment were slightly noticeable between the groups, with an evident flattening of HGFs on both surfaces. All differences between Group A and group B became less significant after 7 days of culture in vitro. Conclusions SEM analysis of HGFs showed differences in terms of cell adhesion and proliferation, especially in the early hours of culture. Results showed a better adhesion and cell growth in Group A than in Group B, especially up to 72h in vitro. Differences decreased after 7 days, probably because of the rougher surface of CAD/CAM zirconia, promoting better cell adhesion, compared to the smoother surface of veneering ceramic. PMID:24611089

Age-velocity dispersion relations and heating histories in disc galaxies

NASA Astrophysics Data System (ADS)

Aumer, Michael; Binney, James; Schönrich, Ralph

2016-10-01

We analyse the heating of stellar discs by non-axisymmetric structures and giant molecular clouds (GMCs) in N-body simulations of growing disc galaxies. The analysis resolves long-standing discrepancies between models and data by demonstrating the importance of distinguishing between measured age-velocity dispersion relations (AVRs) and the heating histories of the stars that make up the AVR. We fit both AVRs and heating histories with formulae ∝tβ and determine the exponents βR and βz derived from in-plane and vertical AVRs and tilde{β }_R and tilde{β }_z from heating histories. Values of βz are in almost all simulations larger than values of tilde{β }_z, whereas values of βR are similar to or mildly larger than values of tilde{β }_R. Moreover, values of βz (tilde{β }_z) are generally larger than values of βR (tilde{β }_R). The dominant cause of these relations is the decline over the life of the disc in importance of GMCs as heating agents relative to spiral structure and the bar. We examine how age errors and biases in solar neighbourhood surveys influence the measured AVR: they tend to decrease β values by smearing out ages and thus measured dispersions. We compare AVRs and velocity ellipsoid shapes σz/σR from simulations to solar neighbourhood data. We conclude that for the expected disc mass and dark halo structure, combined GMC and spiral/bar heating can explain the AVR of the Galactic thin disc. Strong departures of the disc mass or the dark halo structure from expectation spoil fits to the data.

Exoplanet recycling in massive white-dwarf debris discs

NASA Astrophysics Data System (ADS)

Van Lieshout, Rik

2017-06-01

When a star evolves into a white dwarf, the planetary system it hosts can become unstable. Planets in such systems may then be scattered onto star-grazing orbits, leading to their tidal disruption as they pass within the white dwarf’s Roche limit. We study the massive, compact debris discs that may arrise from this process using a combination of analytical estimates and numerical modelling. The discs are gravitationally unstable, resulting in an enhanced effective viscosity due to angular momentum transport associated with self-gravity wakes. For disc masses greater than ~1026 g (corresponding to progenitor objects comparable to the Galilean moons), viscous spreading dominates over Poynting-Robertson drag in the outer parts of the disc. In such massive discs, mass is transported both in- and outwards. When the outward-flowing material spreads beyond the Roche limit, it coagulates into new (minor) planets in a process analogous to the ongoing formation of Saturn’s innermost moonlets. This process recycles a substantial fraction of the original disc mass (tens of percents), with the bulk of the mass locked in a single large body orbitting in a 2:1 mean-motion resonance with the Roche limit. As such, the recycling of a tidally disrupted super-Earth could yield an Earth-mass planet on a 10--20 hr orbit. For white dwarfs with a temperature below 6000-7000 K (corresponding to a cooling age of >1--2 Gyr), this orbit is located in the white dwarf’s habitable zone. The recycling process also creates a string of smaller bodies just outside the Roche limit. These may account for the collection of minor planets postulated to orbit white dwarf WD 1145+017.

Spiral arms and disc stability in the Andromeda galaxy

NASA Astrophysics Data System (ADS)

Tenjes, P.; Tuvikene, T.; Tamm, A.; Kipper, R.; Tempel, E.

2017-04-01

Aims: Density waves are often considered as the triggering mechanism of star formation in spiral galaxies. Our aim is to study relations between different star formation tracers (stellar UV and near-IR radiation and emission from H I, CO, and cold dust) in the spiral arms of M 31, to calculate stability conditions in the galaxy disc, and to draw conclusions about possible star formation triggering mechanisms. Methods: We selected fourteen spiral arm segments from the de-projected data maps and compared emission distributions along the cross sections of the segments in different datasets to each other, in order to detect spatial offsets between young stellar populations and the star-forming medium. By using the disc stability condition as a function of perturbation wavelength and distance from the galaxy centre, we calculated the effective disc stability parameters and the least stable wavelengths at different distances. For this we used a mass distribution model of M 31 with four disc components (old and young stellar discs, cold and warm gaseous discs) embedded within the external potential of the bulge, the stellar halo, and the dark matter halo. Each component is considered to have a realistic finite thickness. Results: No systematic offsets between the observed UV and CO/far-IR emission across the spiral segments are detected. The calculated effective stability parameter has a lowest value of Qeff ≃ 1.8 at galactocentric distances of 12-13 kpc. The least stable wavelengths are rather long, with the lowest values starting from ≃ 3 kpc at distances R > 11 kpc. Conclusions: The classical density wave theory is not a realistic explanation for the spiral structure of M 31. Instead, external causes should be considered, such as interactions with massive gas clouds or dwarf companions of M 31.

Juvenile porcine temporomandibular joint: Three different cartilaginous structures?

PubMed

Tabeian, Hessam; Bakker, Astrid D; de Vries, Teun J; Zandieh-Doulabi, Behrouz; Lobbezoo, Frank; Everts, Vincent

2016-12-01

The temporomandibular joint (TMJ) consists of three cartilaginous structures: the fossa, disc, and condyle. In juvenile idiopathic arthritis (JIA), inflammation of the TMJ leads to destruction of the condyle, but not of the fossa or the disc. Such a different effect of inflammation might be related to differences in matrix composition of the cartilaginous structures. The matrix composition of the three TMJ structures was analyzed in juvenile porcine samples and in an in vitro system of cells isolated from each anatomical structure embedded in 3% agarose gels. The matrix of all three anatomical structures of the TMJ contained collagen type I and its gene expression was maintained after isolation. The condyle and the fossa stained positive for collagen type II and proteoglycans, but the condyle contained considerably more collagen type II and proteoglycans than the fossa. The disc contained neither collagen type II protein nor expression of its gene, and the disc did not stain positive for proteoglycans. Aggrecan gene expression was lower in the disc compared to condyle and fossa cell-isolates. In general, the cell-isolates in vitro closely mimicked the characteristic features found in the tissue. The collagen type II content of the condyle clearly distinguished this cartilaginous structure from the disc and fossa. Since autoimmunity against collagen type II is associated with JIA, the relatively abundant presence of this type of collagen in the condyle might provide an explanation why primarily this cartilaginous structure of the TMJ is affected in JIA patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

The multidirectional bending properties of the human lumbar intervertebral disc.

PubMed

Spenciner, David; Greene, David; Paiva, James; Palumbo, Mark; Crisco, Joseph

2006-01-01

While the biomechanical properties of the isolated intervertebral disc have been well studied in the three principal anatomic directions of flexion/extension, axial rotation, and lateral bending, there is little data on the properties in the more functional directions that are combinations of these principal anatomic directions. To determine the bending flexibility, range of motion (ROM), and neutral zone (NZ) of the human lumbar disc in multiple directions and to determine if the values about the combined moment axes can be predicted from the values about principal moment axes. Three-dimensional biomechanical analysis of the elastic bending properties of human lumbar discs about principal and combined moment axes. Pure, unconstrained moments were applied about multiple axes. The bending properties (flexibility, ROM, and NZ) of isolated lumbar discs (n=4 for L2/L3 and n=3 for L4/L5) were determined in the six principal directions and in 20 combined directions. The experimental values were compared with those predicted from the linear combination of the six principal moment axes. The maximum and minimum values of the biomechanical properties were found at the principal moment axes. Among combined moment axes, ROM and NZ (but not flexibility) values were predicted from the principal moment axis values. The principal moment axes coincide with the primary mechanical axes of the intervertebral disc and demonstrate significant differences in direction for values of flexibility, ROM, and NZ. Not all combined moment axis values can be predicted from principal moment axis values.

Long-term load duration induces N-cadherin down-regulation and loss of cell phenotype of nucleus pulposus cells in a disc bioreactor culture.

PubMed

Li, Pei; Zhang, Ruijie; Wang, Liyuan; Gan, Yibo; Xu, Yuan; Song, Lei; Luo, Lei; Zhao, Chen; Zhang, Chengmin; Ouyang, Bin; Tu, Bing; Zhou, Qiang

2017-04-30

Long-term exposure to a mechanical load causes degenerative changes in the disc nucleus pulposus (NP) tissue. A previous study demonstrated that N-cadherin (N-CDH)-mediated signalling can preserve the NP cell phenotype. However, N-CDH expression and the resulting phenotype alteration in NP cells under mechanical compression remain unclear. The present study investigated the effects of the compressive duration on N-CDH expression and on the phenotype of NP cells in an ex vivo disc organ culture. Porcine discs were organ cultured in a self-developed mechanically active bioreactor for 7 days. The discs were subjected to different dynamic compression durations (1 and 8 h at a magnitude of 0.4 MPa and frequency of 1.0 Hz) once per day. Discs that were not compressed were used as controls. The results showed that long-term compression duration (8 h) significantly down-regulated the expression of N-CDH and NP-specific molecule markers (Brachyury, Laminin, Glypican-3 and Keratin 19), attenuated Alcian Blue staining intensity, decreased glycosaminoglycan (GAG) and hydroxyproline (HYP) contents and decreased matrix macromolecule (aggrecan and collagen II) expression compared with the short-term compression duration (1 h). Taken together, these findings demonstrate that long-term load duration can induce N-CDH down-regulation, loss of normal cell phenotype and result in attenuation of NP-related matrix synthesis in NP cells. © 2017 The Author(s).

Lenticular astigmatism in tilted disc syndrome.

PubMed

Gündüz, Abuzer; Evereklioglu, Cem; Er, Hamdi; Hepşen, Ibrahim F

2002-10-01

To evaluate whether an abnormal optic disc shape in patients with tilted disc syndrome (TDS) is associated with an abnormal configuration of the crystalline lens measured as lenticular astigmatism. Department of Ophthalmology, Inönü University Medical Faculty, Turgut Ozal Medical Center, Malatya, Turkey. This cross-sectional masked case-control study comprised 32 eyes of 32 patients with established TDS (13 men, 19 women; mean age 21.31 years +/- 7.05 [SD]) and 20 age- and sex-matched healthy control subjects (8 men, 12 women; mean age 22.65 +/- 7.11 years) with a comparable amount of myopic astigmatism (spherical equivalent) without TDS. The optic disc was morphometrically analyzed by planimetric evaluation of optic disc photographs. The total refractive and keratometric corneal astigmatism was obtained, and lenticular astigmatism was calculated by vector analysis. The Mann-Whitney U test was used for statistical analysis; 1 eye of each patient was evaluated in both groups. A P value less than 0.05 was considered statistically significant. The mean spherical equivalent refraction was comparable in TDS patients (-4.73 +/- 1.12 diopters [D]) and controls (-4.28 +/- 1.29 D) (P =.210). The mean total astigmatism was higher in TDS patients (-2.96 +/- 1.04 D) than in the controls (-2.51 +/- 1.09 D), but the difference was not significant (P =.151). The mean corneal astigmatism was comparable in TDS patients (-2.07 +/- 0.83 D) and controls (-2.28 +/- 0.87 D) (P =.454), but the calculated mean lenticular astigmatism was significantly higher in TDS patients (-1.31 +/- 0.98 D and -0.20 +/- 0.35 D, respectively) (P <.001). Twenty-nine of 32 TDS patients (90.6%) had lenticular astigmatism; in 16 (50%), it was greater than -1.00 D. Lenticular astigmatism was present in 7 controls (35%); in 2 (10%), it was greater than -1.00 D. The mean keratometry was significantly higher in TDS patients (43.84 +/- 1.06 D) than in the controls (42.75 +/- 1.45 D) (P =.011). Clinically significant lenticular astigmatism was present in TDS patients. If an abnormal optic disc shape is found on ophthalmoscopy, lenticular astigmatism as well as corneal astigmatism should be carefully evaluated to prevent an unsatisfactory refractive outcome, especially in refractive surgery candidates.

Fibrotic-like changes in degenerate human intervertebral discs revealed by quantitative proteomic analysis.

PubMed

Yee, A; Lam, M P Y; Tam, V; Chan, W C W; Chu, I K; Cheah, K S E; Cheung, K M C; Chan, D

2016-03-01

Intervertebral disc degeneration (IDD) can lead to symptomatic conditions including sciatica and back pain. The purpose of this study is to understand the extracellular matrix (ECM) changes in disc biology through comparative proteomic analysis of degenerated and non-degenerated human intervertebral disc (IVD) tissues of different ages. Seven non-degenerated (11-46 years of age) and seven degenerated (16-53 years of age) annulus fibrosus (AF) and nucleus pulposus (NP) samples were used. Proteins were extracted using guanidine hydrochloride, separated from large proteoglycans (PGs) by caesium chloride (CsCl) density gradient ultracentrifugation, and identified using liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS). For quantitative comparison, proteins were labeled with iTRAQ reagents. Collagen fibrils in the NP were assessed using scanning electron microscopy (SEM). In the AF, quantitative analysis revealed increased levels of HTRA1, COMP and CILP in degeneration when compared with samples from older individuals. Fibronectin showed increment with age and degeneration. In the NP, more CILP and CILP2 were present in degenerated samples of younger individuals. Reduced protein solubility was observed in degenerated and older non-degenerated samples correlated with an accumulation of type I collagen in the insoluble fibers. Characterization of collagen fibrils in the NP revealed smaller mean fibril diameters and decreased porosity in the degenerated samples. Our study identified distinct matrix changes associated with aging and degeneration in the intervertebral discs (IVDs). The nature of the ECM changes, together with observed decreased in solubility and changes in fibril diameter is consistent with a fibrotic-like environment. Copyright © 2015 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Evaluation of the Surface Characteristics of Various Implant Abutment Materials Using Confocal Microscopy and White Light Interferometry.

PubMed

Park, Jun-Beom; Yang, Seung-Min; Ko, Youngkyung

2015-12-01

The purpose of this study was to evaluate the surface characteristics of various implant abutment materials, such as of titanium alloy (Ti6Al4V; Ma), machined cobalt-chrome-molybdenum alloy (CCM), titanium nitride coating on a titanium alloy disc (TiN), anodic oxidized titanium alloy disc (AO), composite resin coating on a titanium alloy disc (Res), and zirconia disc (Zr), using confocal microscopy and white light interferometry. Measurements from the 2 methods were evaluated to see if these methods would give equivalent results. The precision of measurements were evaluated by the coefficient of variation. Five discs each of Ma, CCM, TiN, AO, Res, and Zr were used. The surface roughness was evaluated by confocal laser microscopy and white light interferometry. Confocal microscopy showed that the Res group showed significantly greater Ra, Rq, Rz, Sa, Sq, and Sz values compared with those of the Ma group (P < 0.05). The white light interferometry results showed that the Res group had significantly higher Ra, Rq, Rz, Rt, Sa, Sq, Sz, and Sdr values compared with the Ma group (P < 0.05). All the roughness parameters obtained from the 2 methods differed, and the Sa values of the Zr group from confocal microscopy were greater by 0.163 μm than those obtained by white light interferometry. Least difference was seen in the TiN group where the difference was 0.058 μm. Roughness parameters of different abutment materials varied significantly. Precision of measurement differed according to the characteristics of the material used. White light interferometry could be recommended for measurement of TiN and AO. Confocal microscopy gave more precise measurements for Ma and CCM groups. The optical characteristics of the surface should be considered before choosing the examination method.

Influence of Total Knee Arthroplasty on Gait Mechanics of the Replaced and Non-Replaced Limb During Stair Negotiation.

PubMed

Standifird, Tyler W; Saxton, Arnold M; Coe, Dawn P; Cates, Harold E; Reinbolt, Jeffrey A; Zhang, Songning

2016-01-01

This study compared biomechanics during stair ascent in replaced and non-replaced limbs of total knee arthroplasty (TKA) patients with control limbs of healthy participants. Thirteen TKA patients and fifteen controls performed stair ascent. Replaced and non-replaced knees of TKA patients were less flexed at contact compared to controls. The loading response peak knee extension moment was greater in control and non-replaced knees compared with replaced. The push-off peak knee abduction moment was elevated in replaced limbs compared to controls. Loading and push-off peak hip abduction moments were greater in replaced limbs compared to controls. The push-off peak hip abduction moment was greater in non-replaced limbs compared to controls. Future rehabilitation protocols should consider the replaced knee and also the non-replaced knee and surrounding joints. Copyright © 2016 Elsevier Inc. All rights reserved.

Faraday's first dynamo: A retrospective

NASA Astrophysics Data System (ADS)

Smith, Glenn S.

2013-12-01

In the early 1830s, Michael Faraday performed his seminal experimental research on electromagnetic induction, in which he created the first electric dynamo—a machine for continuously converting rotational mechanical energy into electrical energy. His machine was a conducting disc, rotating between the poles of a permanent magnet, with the voltage/current obtained from brushes contacting the disc. In his first dynamo, the magnetic field was asymmetric with respect to the axis of the disc. This is to be contrasted with some of his later symmetric designs, which are the ones almost invariably discussed in textbooks on electromagnetism. In this paper, a theoretical analysis is developed for Faraday's first dynamo. From this analysis, the eddy currents in the disc and the open-circuit voltage for arbitrary positioning of the brushes are determined. The approximate analysis is verified by comparing theoretical results with measurements made on an experimental recreation of the dynamo. Quantitative results from the analysis are used to elucidate Faraday's qualitative observations, from which he learned so much about electromagnetic induction. For the asymmetric design, the eddy currents in the disc dissipate energy that makes the dynamo inefficient, prohibiting its use as a practical generator of electric power. Faraday's experiments with his first dynamo provided valuable insight into electromagnetic induction, and this insight was quickly used by others to design practical generators.