Sample records for additional screw fixation

  1. Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone

    Microsoft Academic Search

    A Weiler; RF Hoffmann; AC Stähelin; HJ Bail; CJ Siepe; NP Südkamp

    1998-01-01

    It has recently been shown that graft fixation close to the ACL insertion site is optimal in order to increase anterior knee stability. Hamstring tendon fixation using interference screws offers this possibility and a round threaded titanium interference screw has been previously developed. The use of a round threaded biodegradable interference screw may be equivalent. In addition, to increase initial

  2. Biodegradable Interference Screw Fixation Exhibits Pull-Out Force and Stiffness Similar to Titanium Screws

    Microsoft Academic Search

    Andreas Weiler; Henning J. Windhagen; Michael J. Raschke; Andrea Laumeyer; Reinhard F. G. Hoffmann

    1998-01-01

    Recently, increased interest in biodegradable interference screws for bone-tendon-bone graft fixation has led to numerous screws becoming available. The implants are made from different polymers and have different designs, which might influence their mechanical properties. Several studies have reported a wide range of mechanical results for these screws using different biomechanical models. The aim of the present study is to

  3. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...4880 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a)...

  4. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...4880 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a)...

  5. Use of self-tapping metal screws for temporary fixation of a resorbable plate system in maxillofacial surgery.

    PubMed

    Iwai, Toshinori; Omura, Susumu; Aoki, Noriaki; Tohnai, Iwai

    2015-05-01

    Resorbable plate systems have been used in maxillofacial surgery to obviate the need for plate removal. However, resorbable plates and screws are very costly, and refixation with additional screws may be necessary when reduction or repositioning of the bone segment is inaccurate. Here we report the use of self-tapping metal screws for temporary fixation of a resorbable plating system in maxillofacial surgery to avoid the use of additional screws following inaccurate fixation or the reuse of resorbable screws, which may result in loosening. PMID:25974798

  6. Fracture risk and initial fixation of a cementless glenoid implant: the effect of numbers and types of screws.

    PubMed

    Suarez, Daniel R; Valstar, Edward R; Rozing, Piet M; van Keulen, Fred

    2013-10-01

    The initial fixation of an anatomical cementless glenoid component, provided by different numbers and types of screws, and the risk of bone fracture were evaluated by estimating the bone-implant interface micromotions and the principal strains around the prosthesis. Four different fixation configurations using locking or compression screws were tested. Estimation of the micromotions at the bone-implant interface was performed both experimentally, using an in vitro model, and computationally, using a numerical model. Principal bone strains were estimated using the numerical model. Subject variability was included by modelling two different bone qualities (healthy and rheumatoid bone). For the fixation configurations that used two screws, experimental and modelling results found that the micromotions at the bone-implant interface did not change with screw type. However, screw type had a significant effect on fixation when only one screw was used; in this case, a locking screw resulted in less micromotion at the bone-implant interface compared with the compression screw. Bone strains were predicted by the numerical model, and strains were found to be independent of the screw type; however, the predicted strain levels calculated in rheumatoid bone were larger than the strain levels that may cause bone damage for most considered arm positions. Predicted bone strain in healthy bone did not reach this level. While proper initial component fixation that allows biological fixation can be achieved by using additional screws, the risk of bone failure around the screws must be considered, especially in cases of weak bone. PMID:23804951

  7. Sacroiliac screw fixation: A mini review of surgical technique

    PubMed Central

    Alvis-Miranda, Hernando Raphael; Farid-Escorcia, Hector; Alcalá-Cerra, Gabriel; Castellar-Leones, Sandra Milena; Moscote-Salazar, Luis Rafael

    2014-01-01

    The sacral percutaneous fixation has many advantages but can be associated with a significant exposure to X-ray radiation. Currently, sacroiliac screw fixation represents the only minimally invasive technique to stabilize the posterior pelvic ring. It is a technique that should be used by experienced surgeons. We present a practical review of important aspects of this technique. PMID:25336831

  8. Primary Stability of Interference Screw FixationInfluence of Screw Diameter and Insertion Torque

    Microsoft Academic Search

    Dieter Kohn; Christoph Rose

    1994-01-01

    Interference screw fixation is frequently used in anterior cruciate ligament reconstruction with the bone-patellar tendon-bone graft. There have been no data available about the influence of screw diameter and insertion torque on primary stability. We designed a cadaveric study using paired knees to analyze the comparative effectiveness of 20-mm long screws of different diam eters (9 mm versus 7 mm)

  9. Outpatient percutaneous screw fixation of the acute Jones fracture

    Microsoft Academic Search

    Norman Mindrebo; K. Donald Shelbourne; Charles D. Van Meter; Arthur C. Rettig

    1993-01-01

    Nine patients (8 men and 1 woman, ranging in age from 17 to 22 years) who sustained a Jones fracture were treated with percutaneous intramedullary screw fixation as outpatients. All of the patients were varsity athletes. Seven were Division I scholarship athletes. Beginning at 7 to 10 days after surgery, all patients were allowed weightbearing as tolerated with a CAM

  10. The EndoPearl device increases fixation strength and eliminates construct slippage of hamstring tendon grafts with interference screw fixation

    Microsoft Academic Search

    Andreas Weiler; Manuel Richter; Gerhard Schmidmaier; Frank Kandziora; Norbert P. Südkamp

    2001-01-01

    Purpose: The EndoPearl (Linvatec, Largo, FL), a biodegradable device to augment the femoral interference screw fixation of hamstring tendon grafts has been developed. The first objective of this study was to compare the initial fixation strength of quadrupled hamstring tendons and biodegradable interference screw fixation with and without the application of the EndoPearl device. The second objective was to determine

  11. Subaxial subluxation after atlantoaxial transarticular screw fixation in rheumatoid patients

    PubMed Central

    Neo, Masashi; Sakamoto, Takeshi; Fujibayashi, Shunsuke; Yoshitomi, Hiroyuki; Nakamura, Takashi

    2009-01-01

    The most common cervical abnormality associated with rheumatoid arthritis (RA) is atlantoaxial subluxation, and atlantoaxial transarticular screw fixation has proved to be one of the most reliable, stable fixation techniques for treating atlantoaxial subluxation. Following C1–C2 fixation, however, subaxial subluxation reportedly can bring about neurological deterioration and require secondary operative interventions. Rheumatoid patients appear to have a higher risk, but there has been no systematic comparison between rheumatoid and non-rheumatoid patients. Contributing radiological factors to the subluxation have also not been evaluated. The objective of this study was to evaluate subaxial subluxation after atlantoaxial transarticular screw fixation in patients with and without RA and to find contributing factors. Forty-three patients who submitted to atlantoaxial transarticular screw fixation without any concomitant operation were followed up for more than 1 year. Subaxial subluxation and related radiological factors were evaluated by functional X-ray measurements. Statistical analyses showed that aggravations of subluxation of 2.5 mm or greater were more likely to occur in RA patients than in non-RA patients over an average of 4.2 years of follow-up, and postoperative subluxation occurred in the anterior direction in the upper cervical spine. X-ray evaluations revealed that such patients had a significantly smaller postoperative C2–C7 angle, and that the postoperative AA angle correlated negatively with this. Furthermore, anterior subluxation aggravation was significantly correlated with the perioperative atlantoaxial and C2–C7 angle changes, and these two changes were strongly correlated to each other. In conclusion, after atlantoaxial transarticular screw fixation, rheumatoid patients have a greater risk of developing subaxial subluxations. The increase of the atlantoaxial angel at the operation can lead to a decrease in the C2–C7 angle, followed by anterior subluxation of the upper cervical spine and possibly neurological deterioration. PMID:19337758

  12. Cement Embolism into the Venous System after Pedicle Screw Fixation: Case Report, Literature Review, and Prevention Tips

    PubMed Central

    Kerry, Ghassan; Ruedinger, Claus; Steiner, Hans-Herbert

    2013-01-01

    The strength of pedicle screws attachment to the vertebrae is an important factor affecting their motion resistance and long term performance. Low bone quality, e.g. in osteopenic patients, keeps the screw bone interface at risk for subsidence and dislocation. In such cases, bone cement could be used to augment pedicle screw fixation. But its use is not free of risk. Therefore, clinicians, especially spine surgeons, radiologists, and internists should become increasingly aware of cement migration and embolism as possible complications. Here, we present an instructive case of cement embolism into the venous system after augmented screw fixation with fortunately asymptomatic clinical course. In addition we discuss pathophysiology and prevention methods as well as therapeutic management of this potentially life-threatening complication in a comprehensive review of the literature. However, only a few case reports of cement embolism into the venous system were published after augmented screw fixation. PMID:24191184

  13. Self-tapping versus standard tapped titanium screw fixation in the upper extremity.

    PubMed

    Bickley, M B; Hanel, D P

    1998-03-01

    Most screws used in fracture fixation necessitate a separate step for tapping of the screw hole. Titanium screw systems have been developed in which the screws can be inserted directly after a drill hole is made. These self-tapping screws thereby eliminate an operative step. A retrospective study was conducted that evaluated all wrist and hand procedures performed between January 1992 and December 1994 by 1 surgeon using screw fixation. The results of 39 cases treated with standard tapped titanium screws were compared with 28 cases treated with self-tapping titanium screws. Nearly identical union and complication rates were obtained in each group. Comparable results can be obtained with self-tapping screw fixation, which limits the number of instruments needed, eliminates an operative step, and thereby may diminish operative risk and shorten operative time. PMID:9556274

  14. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  15. Transarticular screw fixation for atlantoaxial instability - modified Magerl's technique in 38 patients

    Microsoft Academic Search

    Raj Bahadur; Tarun Goyal; Saravdeep S Dhatt; Sujit K Tripathy

    2010-01-01

    BACKGROUND: Symptomatic atlantoaxial instability needs stabilization of the atlantoaxial joint. Among the various techniques described in literature for the fixation of atlantoaxial joint, Magerl's technique of transarticular screw fixation remains the gold standard. Traditionally this technique combines placement of transarticular screws and posterior wiring construct. The aim of this study is to evaluate clinical and radiological outcomes in subjects of

  16. Initial fixation strength of polylactic acid interference screws in anterior cruciate ligament reconstruction

    Microsoft Academic Search

    JA Abate; PD Fadale; MJ Hulstyn; WR Walsh

    1998-01-01

    The initial fixation properties of bioresorbable polylactic acid (PLA) interference screws designed for anterior cruciate ligament reconstruction were evaluated using an in vitro bovine model. The surgical technique of interference screw fixation of the bone-patellar tendon-bone autograft complex performed clinically was reproduced in an adult bovine model. The reconstructed knee was tested oriented in 30 degrees of flexion to allow

  17. Biomechanical analysis of expansion screws and cortical screws used for ventral plate fixation on the cervical spine

    PubMed Central

    Ullrich, Bernhard; Huber, Gerd; Morlock, Michael M.

    2009-01-01

    Compared to bicortical screws, the surgical risk of injuring intraspinal structures can be minimized with the use of monocortical screws. However, this reduction should not be achieved at the expense of the stability of the fixation. With monocortical stabilization, the expansion screws have the potential of absorbing high loads. Therefore, they are expected to be a suitable alternative to bicortical screws for revision surgeries and in osteoporotic bone. The purpose of this in vitro study was to investigate the stiffness of the two screw-plate systems used for ventral stabilization of the cervical spine, by focusing on the suitability of expansion screws as tools for revision treatments. The study was conducted in ten functional units of human cervical spines. The device sample stiffness was determined for four conditions using a turning moment of 2.25 N m each around one of the three principle axes. The conditions were native, destabilized, primarily stabilized with one of the screw-plate systems, followed by secondary stabilization using the expansion screw implant. The stabilized samples achieved a comparable, in most cases higher stiffness than the native samples. The samples undergoing secondary stabilization using expansion screws tend to display greater stiffness for all three axes compared to the primarily stabilized samples. The achieved tightening moment of the screws was higher than the one achieved with primary fixation. Both plates revealed similar primary stability. Revision surgeries with secondary instrumentation achieve a high stiffness of the screwed up segments. Monocortical expansion screws combined with a trapezoidal plate allow ventral stabilization of the cervical spine that is comparable to the plate fixation using bicortical screws. PMID:19588171

  18. Bone cement or bone substitute augmentation of pedicle screws improves pullout strength in posterior spinal fixation

    Microsoft Academic Search

    S. L. Evans; C. M. Hunt; S. Ahuja

    2002-01-01

    Pedicle screws are widely used to fix posterior spinal implants. However, in some situations, such as at the ends of long constructs in scoliosis correction, the screws may pull out of the pedicles. This limits the use of pedicle screw fixation where bone quality is poor. The aim of this study was to investigate the effect of using either a

  19. Transforaminal lumbar interbody fusion using unilateral pedicle screw fixation plus contralateral translaminar facet screw fixation in lumbar degenerative diseases

    PubMed Central

    Liu, Fubing; Jiang, Chun; Cao, Yuanwu; Jiang, Xiaoxing; Feng, Zhenzhou

    2014-01-01

    Background: Transforaminal lumbar interbody fusion (TLIF) has been used in lumbar degenerative diseases. Some researchers have applied unilateral fixation in TLIF to reduce operational trauma without compromising the clinical outcome, but it is always suspected biomechanically unstable. The supplementary contralateral translaminar facet screw (cTLFS) seemed to be able to overcome the inherent drawbacks of unilateral pedicle screw (uPS) fixation theoretically. This study evaluates the safety, feasibility and efficacy of TLIF using uPS with cTLFS fixation in the treatment of lumbar degenerative diseases (LDD). Materials and Methods: 50 patients (29 male) underwent the aforementioned surgical technique for their LDD between December 2009 and April 2012. The results were evaluated based on visual analogue scale (VAS) of the leg and back, Japanese Orthopedic Association (JOA) score and Oswestry Disability Index (ODI) were recorded. The radiographic examinations in form of X-ray, computed tomography (CT) or magnetic resonance imaging was done preoperatively and 1 week, 3 months, 6 months, 12 months and 24 months postoperatively. The student t-test was used for comparison between the preoperative values and postoperative counterparts. P < 0.05 was considered to be statistically significant. Results: Among 50 patients, 22 received one level fusion and 28 two level's, with corresponding operation time and estimated blood loss being approximately 90 min, 150 ml and 120 min, 200 ml, respectively. No severe complications happened perioperatively. The mean VAS (back, leg) scores dropped from (7.6, 7.5) preoperatively to (2.1, 0.6) at 12 months’ followup, ODI from 49.1 preoperatively to 5.6 and JOA score raised from 10.6 preoperatively to 28.5, all P < 0.001, suggesting of good clinical outcome. From the three-dimensional reconstructed CT, 62 out of 70 segments displayed solid fusion with fusion rate of 88.6% at 12 months postoperatively. Conclusions: TLIF using uPS fixation plus cTLFS fixation is a safe, feasible and effective technique in the treatment of one or two level lumbar degenerative diseases short termly. PMID:25143640

  20. Prevention of arthrofibrosis after arthroscopic screw fixation of tibial spine fracture in children and adolescents.

    PubMed

    Parikh, Shital N; Myer, David; Eismann, Emily A

    2014-01-01

    Arthrofibrosis is a major complication of tibial spine fracture treatment in children, potentially resulting in knee pain, quadriceps weakness, altered gait, decreased function, inability to return to sports, and long-term osteoarthritis. Thus, prevention rather than treatment of arthrofibrosis is desirable. The purpose of this study was to evaluate an aggressive postoperative rehabilitation and early intervention approach to prevent permanent arthrofibrosis after tibial spine fracture treatment and to compare epiphyseal and transphyseal screws for fixation. A consecutive series of 24 patients younger than age 18 with displaced type II and III tibial spine fractures who underwent arthroscopic reduction and screw fixation between 2006 and 2011 were retrospectively reviewed. Final range of motion was compared between patients with epiphyseal (n=12) and transphyseal (n=9) screws. One-third (4 of 12) of patients with epiphyseal screws underwent arthroscopic debridement and screw removal approximately 3 months postoperatively; 3 patients lacked 5° to 15° of extension, 1 experienced pain with extension, and 1 had radiographic evidence of screw pullout, loss of reduction, and resultant malunion. In the transphyseal screw group, 3 patients had 10° loss of extension, and all corrected after arthroscopic debridement and screw removal. The two groups did not significantly differ in time to hardware removal or return to sports or final range of motion. No growth disturbances were identified in patients after transphyseal screw removal. An aggressive approach of postoperative rehabilitation and early intervention after arthroscopic reduction and screw fixation of tibial spine fractures in children was successful in preventing permanent arthrofibrosis. PMID:24683658

  1. Percutaneous Cement-Augmented Screws Fixation in the Fractures of the Aging Spine: Is It the Solution?

    PubMed Central

    Pesenti, Sébastien; Peltier, Emilie; Adetchessi, Tarek; Dufour, Henry; Fuentes, Stéphane

    2014-01-01

    Introduction. Management of elderly patients with thoracolumbar fractures is still challenging due to frequent osteoporosis and risk of screws pull-out. The aim of this study was to evaluate results of a percutaneous-only procedure to treat these fragile patients using cement-augmented screws. Methods. 12 patients diagnosed with a thoracolumbar fracture associated with an important loss of bone stock were included in this prospective study. Surgical procedure included systematically a percutaneous osteosynthesis using cemented fenestrated screws. When necessary, additional anterior support was performed using a kyphoplasty procedure. Clinical and radiographic evaluations were performed using CT scan. Results. On the whole series, 15 fractures were diagnosed and 96 cemented screws were inserted. The difference between the pre- and postoperative vertebral kyphosis was statistically significant (12.9° versus 4.4°, P = 0.0006). No extrapedicular screw was reported and one patient was diagnosed with a cement-related pulmonary embolism. During follow-up period, no infectious complications, implant failures, or pull-out screws were noticed. Discussion. Aging spine is becoming an increasing public health issue. Management of these patients requires specific attention due to the augmented risk of complications. Using percutaneous-only screws fixation with cemented screw provides satisfactory results. A rigorous technique is mandatory in order to achieve best outcomes. PMID:24696858

  2. Serial lead impedance measurements confirm fixation of helical screw electrodes during pacemaker implantation.

    PubMed

    Roelke, M; Bernstein, A D; Parsonnet, V

    2000-04-01

    The purpose of this study was to determine whether serial measurements of helical screw pacemaker lead impedance could reliably confirm electrode fixation in the right atrium and right ventricle. Fixation is generally assessed fluoroscopically, which can be misleading because the myocardium is radiolucent. Alternatively, because the electrical conductivity of blood is greater than that of myocardium, serial measurements of the lead impedance might be expected to show an impedance increase with appropriate fixation of the pacemaker electrode when the electrode becomes embedded in myocardial tissue. Impedance measurements were made during the placement of 23 atrial and 28 ventricular active fixation electrodes in 31 consecutive patients. Impedance measurements were recorded in unipolar and bipolar electrode configurations with the electrode free floating in the chamber, unfixed (with exposed screws) but touching the endocardial surface, and after fixation. No significant impedance differences were found between free-floating and unfixed electrode positions. With fixation, the lead impedance increased significantly in the ventricle (P = 0.0001, unipolar and bipolar) and the atrium (P = 0.0069 unipolar and 0.0052 bipolar). Typical increases, reflected by median values, were 197 ohms unipolar and 203 ohms bipolar in the ventricle and 47 ohms unipolar and 53 ohms bipolar in the atrium for electrodes with permanently exposed or retractable screw designs. Comparing serial measurements of lead impedance before and after electrode fixation is a valid electrical method of confirming appropriate fixation of helical screw electrodes. PMID:10793439

  3. Surgical Strategies to Improve Fixation in the Osteoporotic Spine: The Effects of Tapping, Cement Augmentation, and Screw Trajectory

    PubMed Central

    Kuhns, Craig A.; Reiter, Michael; Pfeiffer, Ferris; Choma, Theodore J.

    2013-01-01

    Study Design?Biomechanical study of pedicle screw fixation in osteoporotic bone. Objective?To investigate whether it is better to tap or not tap osteoporotic bone prior to placing a cement-augmented pedicle screw. Methods?Initially, we evaluated load to failure of screws placed in cancellous bone blocks with or without prior tapping as well as after varying the depths of tapping prior to screw insertion. Then we evaluated load to failure of screws placed in bone block models with a straight-ahead screw trajectory as well as with screws having a 23-degree cephalad trajectory (toward the end plate). These techniques were tested with nonaugmented (NA) screws as well as with bioactive cement (BioC) augmentation prior to screw insertion. Results?In the NA group, pretapping decreased fixation strength in a dose-dependent fashion. In the BioC group, the tapped screws had significantly greater loads to failure (p?screw orientation, the screws oriented at 23 degrees cephalad had a significantly higher failure force than their respective counterparts at 0 degrees (p?screw fixation is often inadequate in the osteoporotic spine, but this study suggests tapping prior to cement augmentation will substantially improve fixation when compared with not tapping. Angulating screws more cephalad also seems to enhance aging spine fixation. PMID:24494181

  4. Refracture of proximal fifth metatarsal (Jones) fracture after intramedullary screw fixation in athletes.

    PubMed

    Wright, R W; Fischer, D A; Shively, R A; Heidt, R S; Nuber, G W

    2000-01-01

    This study details six instances of refracture of clinically and radiographically healed fractures of the base of the fifth metatarsal after intramedullary screw fixation. Four professional football players, one college basketball player, and one recreational athlete underwent intramedullary screw fixation of fifth metatarsal fractures. The athletes were released to full activities an average of 8.5 weeks (range, 5.5 to 12) after fixation, when healing was clinically and radiographically documented. Three football players developed refracture within 1 day of return to full activity. The other three athletes refractured at 2.5, 4, and 4.5 months after return to activity. Two football players underwent repeat fixation with larger screws and returned to play in the same season. The college basketball player underwent bone grafting and returned to play in subsequent seasons. The other three athletes underwent nonoperative management and healed uneventfully over 6 to 8 weeks. On the basis of this series, we recommend that 1) screw fixation using a large-diameter screw should be given careful consideration for patients with large body mass for whom early return to activity is important; 2) functional bracing, shoe modification, or an orthosis should be considered for return to play; 3) if refracture occurs, exchange to a larger screw may allow return to play in the same season; and 4) alternative imaging should be considered to help document complete healing. PMID:11032233

  5. Efficacy analysis of pedicle screw internal fixation of fractured vertebrae in the treatment of thoracolumbar fractures.

    PubMed

    Huang, Weijie; Luo, Tao

    2013-03-01

    The present study aimed to discuss the method and effect of posterior internal fixation of thoracolumbar fractures strengthened by the vertical stress pedicle screw fixation of fractured vertebrae. Patients with single thoracolumbar fractures were examined retrospectively. Fourteen patients (group A) had been treated with vertical stress pedicle screw fixation of a fractured vertebra and sixteen patients (group B) received traditional double-plate fixation, as a control. All patients were diagnosed with fresh fractures with a complete unilateral or bilateral pedicle and no explosion of the inferior half of the vertebral body or inferior endplate. In group A, patients received conventional posterior distraction and lumbar lordosis restoration, as well as pedicle screws in the fractured vertebra in a vertical direction to relieve stress to achieve a local stress balance. All patients were followed up postoperatively for 4-18 months (average, 12.6 months). The vertical stress pedicle screw fixation assisted in the reduction of vertebrae fracture, which reduced the postoperative Cobb's angle loss. There was a significant difference in the change of Cobb's angle between the two groups one year after surgery (P<0.01). Conditional application of pedicle screws in a single thoracolumbar fracture enhances the stability of the internal fixation system and is conducive to the correction of kyphosis and maintenance of the corrective effects. PMID:23407593

  6. Bioabsorbable Versus Metallic Screw Fixation for Tibiofibular Syndesmotic Ruptures: A Meta-Analysis.

    PubMed

    van der Eng, Dorien M; Schep, Niels W L; Schepers, Tim

    2015-01-01

    Ankle fractures with syndesmotic rupture require operative treatment. In most cases, this consists of fixation of the tibiofibular joint with 1 or more screws. Bioabsorbable screws are used for the same purpose but have the advantage that screw removal is unnecessary. The aim of the present study was to compare the results of bioabsorbable and metallic syndesmotic screws. A systematic search was performed in the Ovid MEDLINE electronic database and Google Scholar. Three randomized controlled trials and one comparison study, with 260 patients, were included. The experimental group consisted of patients with syndesmotic injuries treated with bioabsorbable screws versus the control group (patients treated with metallic screws). The primary outcomes were complications and wound infections. No statistically significant difference was demonstrable in the overall number of complications between the 2 groups. In the group of patients with a bioabsorbable screw, 32 of 137 (23.4%) experienced a complication versus 7 of 123 patients (5.7%) with a metallic screw. Data on wound-related complications showed no statistically significant difference, 19.7% versus 5.7%. The average maximum range of motion in both groups was comparable. Bioabsorbable syndesmotic screws and metallic syndesmotic screws were comparable with respect to the incidence of complications and range of motion. However, the absolute number of complications was greater with bioabsorbable screws. PMID:25960058

  7. Simulation-based particle swarm optimization and mechanical validation of screw position and number for the fixation stability of a femoral locking compression plate.

    PubMed

    Lee, Chian-Her; Shih, Kao-Shang; Hsu, Ching-Chi; Cho, Tomas

    2014-01-01

    Locking compression plates (LCPs) have been used to fix femoral shaft fractures. Previous studies have attempted to identify the best LCP screw positions and numbers to achieve the fixation stability. However, the determined screw positions and numbers were mainly based on the surgeons' experiences. The aim of this study was to discover the best number and positions of LCP screws to achieve acceptable fixation stability. Three-dimensional numerical models of a fractured femur with the LCP were first developed. Then, the best screw position and number of LCPs were determined by using a simulation-based particle swarm optimization algorithm. Finally, the results of the numerical study were validated by conducting biomechanical tests. The results showed that the LCP with six locking screws resulted in the necessary fixation stability, and the best combination of positions of locking screws inserted into the LCP was 1-5-6-7-8-12 (three locking screws on either side of the bone fragment with two locking screws as close as practicable to the fracture site). In addition, the numerical models and algorithms developed in this study were validated by the biomechanical tests. Both the numerical and experimental results can provide clinical suggestions to surgeons and help them to understand the biomechanics of LCP systems. PMID:24090880

  8. Lumbosacral fixation using sacroiliac buttress screws: a modification to the Jackson technique with intrasacral rods

    PubMed Central

    2014-01-01

    Background The use of intrasacral rods has been previously reported for posterior lumbosacral fixation. However, problems associated with this technique include poor stability of the rod in the sacrum, difficulty in contouring the rod to fit the lateral sacral mass, and the complicated assembly procedure for the rod and pedicle screws in the thoracolumbar segments after insertion of the rod into the sacrum. Methods We used a screw with a polyaxial head instead of an intrasacral rod, which was inserted into the lateral sacral mass and assembled to the rod connected cephalad to pedicle screws. The dorsal side of the screw was stabilized by the sacral subchondral bone at the sacroiliac joint with iliac buttress coverage, and the tip of the screw was anchored by the sacral cortex. Results Three different cases were used to illustrate lumbosacral fixation using intrasacral screws as an anchor for the spinal instrumentation. Effective resistance of flexural bending moment and fusion were achieved in these patients at the lumbosacral level. Conclusions An intrasacral screw can be stabilized by subchondral bone with iliac buttress coverage at the dorsal and ventral sacral cortex. Posterior spinal fusion with this screw technique enables easier assembly of the instrumentation and presents better stabilization than that provided by the previously reported intrasacral rod technique for correction and fusion of thoracolumbar kyphoscoliosis. PMID:25050132

  9. Implant failure in a proximal femoral fracture treated with dynamic hip screw fixation

    PubMed Central

    Dabis, John; Abdul-Jabar, Hani B.; Dabis, Hosam

    2015-01-01

    Dynamic hip screw fixation is a common orthopaedic procedure and to date, still can cause difficulties to the senior trauma surgeon. We present a case where an extra-capsular fracture of the proximal femur was managed with a dynamic hip screw (DHS) fixation. She proceeded to the operating theatre, where the fracture was stabilized with a 75-mm DHS and short-barrelled plate. The implant position was checked with intraoperative screening and the position accepted. Following attempted mobilization at 11 days post-operatively, the patient developed a recurrence of her preoperative pain. X-ray showed that the implant screw had separated from the barrel. Later scrutiny of the intraoperative screening films revealed that the barrel and screw were not engaged at the time of surgery. Intraoperative screening films should be carefully checked to ensure congruity of implant components. PMID:26136561

  10. Implant failure in a proximal femoral fracture treated with dynamic hip screw fixation.

    PubMed

    Dabis, John; Abdul-Jabar, Hani B; Dabis, Hosam

    2015-01-01

    Dynamic hip screw fixation is a common orthopaedic procedure and to date, still can cause difficulties to the senior trauma surgeon. We present a case where an extra-capsular fracture of the proximal femur was managed with a dynamic hip screw (DHS) fixation. She proceeded to the operating theatre, where the fracture was stabilized with a 75-mm DHS and short-barrelled plate. The implant position was checked with intraoperative screening and the position accepted. Following attempted mobilization at 11 days post-operatively, the patient developed a recurrence of her preoperative pain. X-ray showed that the implant screw had separated from the barrel. Later scrutiny of the intraoperative screening films revealed that the barrel and screw were not engaged at the time of surgery. Intraoperative screening films should be carefully checked to ensure congruity of implant components. PMID:26136561

  11. Proximal screws placement in intertrochanteric fractures treated with external fixation: comparison of two different techniques

    PubMed Central

    2011-01-01

    Background To compare two different techniques of proximal pin placement for the treatment of intertrochanteric fractures in elderly patients utilizing the Orthofix Pertrochanteric Fixator. Methods Seventy elderly high-risk patients with an average age of 81 years were treated surgically for intertrochanteric fracture, resulting from a low energy trauma. Patients were randomly divided in two groups regarding to the proximal pin placement technique. In Group A the proximal pins were inserted in a convergent way, while in Group B were inserted in parallel. Results All fractures healed uneventfully after a mean time of 98 days. The fixator was well accepted and no patient had significant difficulties while sitting or lying. The mean VAS score was 5.4 in group A and 5.7 in group B. At 12 months after surgery, in group A the average Harris Hip Score and the Palmer and Parker mobility score was 67 and 5.8, respectively. In group B, the average Harris Hip Score and the Palmer and Parker mobility score was 62 and 5.6, respectively. No statistically significant difference was found regarding the functional outcome. The mean radiographic exposure during pin insertion in Group A and Group B was 15 and 6 seconds, respectively. The difference between the two groups, regarding the radiographic exposure, was found to be significant. Conclusion Proximal screw placement in a parallel way is simple, with significant less radiation exposure and shorter intraoperative duration. In addition, fixation stability is equal compared to convergent pin placement. PMID:21939534

  12. Posterior pelvic ring fractures: Closed reduction and percutaneous CT-guided sacroiliac screw fixation

    SciTech Connect

    Jacob, Augustinus Ludwig [Kantonsspital-Universitaetskliniken, Institute of Diagnostic Radiology (Switzerland); Messmer, Peter [Kantonsspital-Universitaetskliniken, Department of Surgery (Switzerland); Stock, Klaus-Wilhelm [Kantonsspital-Universitaetskliniken, Institute of Diagnostic Radiology (Switzerland); Suhm, Norbert [Kantonsspital-Universitaetskliniken, Department of Surgery (Switzerland); Baumann, Bernard [Kantonsspital-Universitaetskliniken, Institute of Diagnostic Radiology (Switzerland); Regazzoni, Pietro [Kantonsspital-Universitaetskliniken, Department of Surgery (Switzerland); Steinbrich, Wolfgang [Kantonsspital-Universitaetskliniken, Institute of Diagnostic Radiology (Switzerland)

    1997-07-15

    Purpose. To assess the midterm results of closed reduction and percutaneous fixation (CRPF) with computed tomography (CT)-guided sacroiliac screw fixation in longitudinal posterior pelvic ring fractures. Methods. Thirteen patients with 15 fractures were treated. Eleven patients received a unilateral, two a bilateral, screw fixation. Twenty-seven screws were implanted. Continuous on-table traction was used in six cases. Mean radiological follow-up was 13 months. Results. Twenty-five (93%) screws were placed correctly. There was no impingement of screws on neurovascular structures. Union occurred in 12 (80%), delayed union in 2 (13%), and nonunion in 1 of 15 (7%) fractures. There was one screw breakage and two axial dislocations. Conclusion. Sacroiliac CRPF of longitudinal fractures of the posterior pelvic ring is technically simple, minimally invasive, well localized, and stable. It should be done by an interventional/surgical team. CT is an excellent guiding modality. Closed reduction may be a problem and succeeds best when performed as early as possible.

  13. Use of resorbable screws for autogenous onlay block graft fixation: a histological analysis in rabbits.

    PubMed

    Klüppel, Leandro Eduardo; Stabile, Glaykon Alex Vitti; Antonini, Fernando; Nascimento, Frederico Felipe; de Moraes, Marcio; Mazzonetto, Renato

    2015-02-01

    The aim of the present in vivo study is to histologically evaluate and compare the use of resorbable screws based on poly(L-co-D,L lactide) 70:30 for fixation of autogenous bone grafts in rabbit tibiae. As control group, titanium (Ti-6Al-4V Grade V) screws were used. For this purpose, 15 white New Zealand male rabbits, aged 6 months and weighing between 3.8 and 4.5 kg, were used. From each animal, 2 total-thickness bone grafts were removed from the cranial vault: one was stabilized with a resorbable screw while the other was stabilized with a metallic one. Animals were divided into 3 groups, according to the sacrifice period: 3, 8, and 16 weeks postoperatively. After histological processing, cuts were stained with hematoxylin and eosin and submitted for descriptive histological analysis under light microscopy. It was found that the fixation system based on the polymer showed a histological behavior similar to metallic screws. For both groups, the bone graft was incorporated, with the presence of bone formation between the graft and receptor site. In none of the groups were undesirable inflammatory responses or foreign body reactions observed. Based on histological findings and on this experimental model, it is possible to conclude that the internal fixation system based on the poly(L-co-D,L lactide) 70:30 polymer is effective for fixation of autogenous bone grafts, with results that are comparable to the titanium fixation system. PMID:23414521

  14. Screw fixation of an OCD loose body: 21-year results.

    PubMed

    Cvetanovich, Gregory L; Mall, Nathan A; Van Thiel, Geoffrey S; Chahal, Jaskarndip; Bach, Bernard

    2013-12-01

    Osteochondritis dissecans (OCD) lesions can progress to loose body formation for which treatment is controversial and may involve excision or fixation. There is a paucity of published data regarding long-term outcomes following OCD loose body fixation. This case report presents an interval follow-up of a patient from a previous small case series of individuals who underwent open reduction internal fixation of large, lateral OCD loose bodies. At 21-year follow-up the patient has full, pain-free range of motion, and has not required subsequent surgery. This case, to our knowledge, is the first to report over 20-year follow-up from fixation of an OCD loose body and demonstrates a good long-term outcome. Clinicians should consider replacement and fixation of an OCD loose body when possible, as this may provide the best chance of long-term function. PMID:23288769

  15. Chitosan-coated Stainless Steel Screws for Fixation in Contaminated Fractures

    PubMed Central

    Greene, Alex H.; Bumgardner, Joel D.; Yang, Yunzhi; Moseley, Jon

    2008-01-01

    Stainless steel screws and other internal fixation devices are used routinely to stabilize bacteria-contaminated bone fractures from multiple injury mechanisms. In this preliminary study, we hypothesize that a chitosan coating either unloaded or loaded with an antibiotic, gentamicin, could lessen or prevent these devices from becoming an initial nidus for infection. The questions investigated for this hypothesis were: (1) how much of the sterilized coating remains on the screw with simulated functional use; (2) is the unloaded or loaded chitosan coating bacteriostatic and biocompatible; and (3) what amount and rate does an antibiotic elute from the coating? In this study, the gentamicin eluted from the coating at a detectable level during 72 to 96 hours. The coating was retained at the 90% level in simulated bone screw fixation and the unloaded and loaded chitosan coatings had encouraging in vitro biocompatibility with fibroblasts and stem cells and were bacteriostatic against at least one strain of Staphylococcus aureus. The use of an antibiotic-loaded chitosan coating on stainless steel bone screws and internal fixation devices in contaminated bone fracture fixation may be considered after optimization of antibiotic loading and elution and more expanded in vitro and in vivo investigations with other organisms and antibiotics. PMID:18443893

  16. The biomechanics of interference screw fixation of patellar tendon anterior cruciate ligament grafts

    Microsoft Academic Search

    Charles H. Brown; Aaron T. Hecker; John A. Hipp; Elizabeth R. Myers; Wilson C. Hayes

    1993-01-01

    Twenty-seven paired human cadaveric knee specimens were used to determine the effect of surgical technique and various interference screw parameters on the pullout strength of patellar tendon femoral bone blocks. The study compared the fixation strength of endoscop ically inserted and conventional \\

  17. Short segment screw fixation without fusion in treatment for unstable thoracolumbar burst fracture

    PubMed Central

    Tang, Jiaguang; Liu, Yishan; Cao, Zheng; Hu, Yuan; Lu, Xiang; Lin, Bin

    2014-01-01

    This study aims to evaluate clinical efficacy of short segment pedicle screw fixation without bone fusion for unstable thoracolumbar burst fracture. Nineteen patients younger than 40 years old with unstable thoracolumbar burst fractures were included. The surgical procedure included postural reduction for 3 days and screw fixations at one level above, one level below and at the fractured level itself. The implants were removed 12 months after initial operation. Imaging and clinical findings were analyzed at preoperative, 12 months after surgery, just before implant removal, and at six months after implant removal. Results indicated that difference was statistically significant between preoperative period or postoperative 1 year follow-up, just before implant removal and 6 months after implant removal (P < 0.05). Results at postoperative 1 year follow-up, just before implant removal and 6 months after implant removal were better than preoperative period. There were no significant complications or neurological deterioration after screws insert and removal in any patient. The rate of clinical outcome with excellent and good was 94.7%. In conclusion, short segment pedicle screw fixation without bone fusion can be an effective and safe operative srategytechnique in the management of young patients suffering from unstable burst fracture. PMID:25664090

  18. Use of C2 spinous process screw for posterior cervical fixation as substitute for laminar screw in a patient with thin laminae

    PubMed Central

    Nagata, Kosei; Baba, Satoshi; Chikuda, Hirotaka; Takeshita, Katsushi

    2013-01-01

    Rigid screw fixation of C2 including transarticular screw and pedicle screw contain the risk of vertebral artery (VA) injury. On the other hand, translaminar screws are considered to be safer for patients with anomalous VA. But C2 translaminar screw placement was limited in patients who have thin laminas and there is marked variation in C2 laminar thickness. Appropriate C2 fixation method for a patient who has thin laminas and high-riding VA together was controversial. Here, we present a case of an elderly Asian woman who had thin laminas and high-riding VA together with progressive myelopathy to report a first case of C2 spinous process screw insertion. Although the stability and safety of C2 spinous process screw was reported in cadaver series, there was no clinical report to our knowledge. Spinous process screw can be an option of C2 fixation for patients with high-riding VA and severe degenerated cervical spines including thin C2 laminas. PMID:23814004

  19. Anti-RANKL treatment improves screw fixation in cancellous bone in rats.

    PubMed

    Bernhardsson, Magnus; Sandberg, Olof; Aspenberg, Per

    2015-06-01

    Bisphosphonates improve implant fixation in randomised clinical trials of knee prostheses, hip prostheses and dental implants. However, a limited amount of bone resorption is required for bisphosphonates to exert an effect. Anti-RANKL treatment does not have this limitation, and we therefore tested whether if they might be more effective for improvement of implant fixation. This is of interest, as anti-RANKL treatment with denosumab is now in common clinical use. Male SD rats received a stain-less steel screw in the right proximal tibia and a drill hole in the left (n=42). They were randomised to subcutaneous injections of either alendronate (20?g/kg/day), alendronate (200?g/kg/day), osteoprotegerin with an Fc tag (OPG-Fc; 8mg/kg, twice weekly), or saline control. After 4 weeks, the fixation of the steel screw was measured by pull-out test. The tibia with the drill hole was evaluated with ?CT. OPG-Fc increased the pull-out force compared to saline controls by 153% (p<0.001). There was no significant difference between OPG-Fc and the alendronate groups. OPG-Fc increased the bone density (BV/TV) in the previous drill hole compared to controls 7-fold (p<0.001). This increase was higher than with any alendronate dose (p<0.001). OPG-Fc increased the bone density of the L5 vertebral body, but there was no significant difference between OPG-Fc and alendronate. Our results suggest that screw fixation in cancellous bone can be dramatically improved by an anti-RANKL agent. The effect was comparable to very high bisphosphonate doses. Screw insertion in cancellous bone elicits a metaphyseal fracture healing response, and our findings might be relevant not only for implant fixation, but also for fracture healing in cancellous bone. PMID:25744169

  20. A Comparison of Functional Outcomes After Metallic and Bioabsorbable Interference Screw Fixations in Arthroscopic ACL Reconstructions

    PubMed Central

    Rai, Deepak K; Kannampilly, Antony J

    2014-01-01

    Introduction: Anterior Cruciate Ligament (ACL) is as one of the most frequently injured ligaments in the modern contact sports scenario. Graft fixations can be achieved during anterior cruciate ligament (ACL) reconstructions by using either bioabsorbable screws or metal screws. The objective of this study was to compare the functional outcomes after bioabsorbable and metallic interference screw fixations in arthroscopic anterior cruciate ligament reconstructions done by using hamstring grafts. Materials and Methods: This was a prospective, randomized study. Patients in Group 1 received bioabsorbable interference screws and patients in Group 2 received metallic interference screws. Arthroscopic assisted, anterior cruciate ligament reconstructions with the use of hamstring grafts which were fixed proximally with endobuttons and distally with bioabsorbable or metallic interference screws, were undertaken. Progress in functional outcomes was assessed by using Mann Whitney U- test. Functional outcomes in the two groups were compared by using independent t-test. Observation and Results: In each group, there were statistically significant improvements in functional outcomes over successive follow-ups, which were seen on basis on Mann-Whitney U-test. The comparison of functional outcomes between the two groups, done by using independent t-test, showed no statistically significant differences between the two groups at 3 months, 6 months and 1 year of follow-up. p-value <0.05 was considered to be significant in our study. Conclusion: In our prospective study of comparison of functional outcomes between bioabsorbable and metallic interference screws in arthroscopic anterior cruciate ligament reconstuctions, which were evaluated by using Tegner activity scale and Lysholm knee scoring scale for a period of 1 year, no statistically significant difference was found. However, further authentication is required by doing long term studies. PMID:24959468

  1. Endovascular Treatment of a Vertebral Artery Pseudoaneurysm Following Posterior C1-C2 Transarticular Screw Fixation

    SciTech Connect

    Mendez, Jose C. [Hospital Virgen de la Salud, Avda., Department of Neuroradiology (Spain)], E-mail: jmendezce@hotmail.com; Gonzalez-Llanos, Francisco [Hospital Virgen de la Salud, Avda., Deparment of Neurosurgery (Spain)

    2005-01-15

    We present a case of vertebral artery pseudoaneurysm after a posterior C1-C2 transarticular screw fixation procedure that was effectively treated with endovascular coil occlusion. Vertebral artery pseudoaneurysm complicating posterior C1-C2 transarticular fixation is extremely rare, with only one previous case having been reported previously. Endovascular occlusion is better achieved in the subacute phase of the pseudoaneurysm, when the wall of the pseudoaneurysm has matured and stabilized. Further follow-up angiographies are mandatory in order to confirm that there is no recurrence of the lesion.

  2. Comparison between Bilateral C2 Pedicle Screwing and Unilateral C2 Pedicle Screwing, Combined with Contralateral C2 Laminar Screwing, for Atlantoaxial Posterior Fixation

    PubMed Central

    Hongo, Michio; Kobayashi, Takashi; Suzuki, Tetsuya; Abe, Eiji; Shimada, Yoichi

    2014-01-01

    Study Design A retrospective study. Purpose To compare clinical and radiological outcomes between bilateral C2 pedicle screwing (C2PS) and unilateral C2PS, combined with contralateral C2 laminar screwing (LS), for posterior atlantoaxial fixation. Overview of Literature Posterior fixation with C1 lateral mass screwing (C1LMS) and C2PS (C1LMS-C2PS method) is an accepted procedure for rigid atlantoaxial stabilization. However, conventional bilateral C2PS is not always allowed in this method due to anatomical variations of C2 pedicles and/or asymmetry of the vertebral artery. Although unilateral C2PS plus contralateral LS (C2PS+LS) is an alternative in such cases, the efficacy of this procedure has not been evaluated in controlled studies (i.e., with bilateral C2PS as a control). Methods Clinical and radiological records of patients who underwent the C1LMS-C2PS method, using unilateral C2PS+LS (n=9), and those treated using conventional bilateral C2PS (n=10) were compared, with a minimum two years follow-up. Results Postoperative complications related to the unilateral C2PS+LS technique included one case of spontaneous spinous process fracture of C2. A C1 anterior arch fracture occurred after a fall in one patient, who underwent bilateral C2PS and C1 laminectomy. No significant differences were seen between the groups in reduction of neck pain after surgery or improvement of neurological status, as evaluated using the Japanese Orthopaedic Association score. A delayed union occurred in one patient each of the groups, with the final fusion rate being 100% in both groups. Conclusions Clinical and radiological outcomes of unilateral C2PS+LS were comparable with those of the bilateral C2PS fixation technique for the C1LMS-C2PS method. PMID:25558320

  3. Mandibular fractures treated with maxillomandibular fixation screws (MMFS method).

    PubMed

    Imazawa, Takashi; Komuro, Yuzo; Inoue, Masahiro; Yanai, Akira

    2006-05-01

    The purpose of the treatment of mandibular fractures is to restore proper dental occlusion and stable temporomandibular joint movement, as well as the reduction of the displaced fracture. Consideration must be given to the selection of the most appropriate surgical and rehabilitation methods in such patients. Typical surgical methods for the treatment of mandibular fractures include the arch bar method or plating at the location of the fracture combined with fixing the mandible to the maxilla using the arch bar method. However arch bars and circumdental wires, which require teeth for fixation, damage teeth and periodontal tissue, and tend to be uncomfortable for patients during the fixation period. Moreover, daily maintenance of oral hygiene is difficult for patients with an arch bar. Surgeons are also exposed to the risk of blood-transmitted diseases through skin punctures by wires when affixing these devices. For these reasons, we chose to study the potential of the MMFS method, which is thought to lessen all of the following problems: tissue damage, operating time, patient discomfort, and possible exposure to percutaneous infectious disease due to puncture of gloves and skin by the wires. We demonstrated the utility of the MMFS method in the present study. PMID:16770195

  4. Tibial Inlay Press-fit Fixation Versus Interference Screw in Posterior Cruciate Ligament Reconstruction

    PubMed Central

    Ettinger, Max; Büermann, Sarah; Calliess, Tilman; Omar, Mohamed; Krettek, Christian; Hurschler, Christof; Jagodzinski, Michael; Petri, Maximilian

    2013-01-01

    Reconstruction of the posterior cruciate ligament (PCL) by a tibial press-fit fixation of the patellar tendon with an accessory bone plug is a promising approach because no foreign materials are required. Until today, there is no data about the biomechanical properties of such press-fit fixations. The aim of this study was to compare the biomechanical qualities of a bone plug tibial inlay technique with the commonly applied interference screw of patellar tendon PCL grafts. Twenty patellar tendons including a bone block were harvested from ten human cadavers. The grafts were implanted into twenty legs of adult German country pigs. In group P, the grafts were attached in a press-fit technique with accessory bone plug. In group S, the grafts were fixed with an interference screw. Each group consisted of 10 specimens. The constructs were biomechanically analyzed in cyclic loading between 60 and 250 N for 500 cycles recording elongation. Finally, ultimate failure load and failure mode were analyzed. Ultimate failure load was 598.6±36.3 N in group P and 653.7±39.8 N in group S (not significant, P>0.05). Elongation during cyclic loading between the 1st and the 20th cycle was 3.4±0.9 mm for group P and 3.1±1 mm for group S. Between the 20th and the 500th cycle, elongation was 4.2±2.3 mm in group P and 2.5±0.9 mm in group S (not significant, P>0.05). This is the first study investigating the biomechanical properties of tibial press-fit fixation of the patellar tendon with accessory bone plug in posterior cruciate ligament reconstruction. The implant-free tibial inlay technique shows equal biomechanical characteristics compared to an interference screw fixation. Further in vivo studies are desirable to compare the biological behavior and clinical relevance of this fixation device. PMID:24416479

  5. [Troublesome radiologic changes after reconstructive fixation of the anterior cruciate ligament with resorbable interference screws].

    PubMed

    Loubignac, F; Lecuire, F; Rubini, J; Basso, M

    1998-03-01

    The authors report worrisome radiological changes which were noted after implantation of absorbable interference screws in ligamentoplasty at the knee joint. Seventeen screws were implanted between September 1995 and July 1996, in eleven patients (average age 27) who were operated upon for chronic anterior knee instability. They underwent a modified Kenneth Jones procedure using autografts with absorbable interference screws (Acufex in 2 cases and Bio-interférix in 9 cases). Significant enlargement of bone tunnels and bony sclerosis of their edges were noted in every patient, but without any modification in the positioning of the graft. No clinical instability was observed in any of the patients, with one to two years follow-up. Publications on this topic are scarce except for one author who reported enlargement of bone tunnels after using bone-patellar tendon-bone allografts. Resorption of absorbable screws probably induces a marked inflammatory reaction, with radiological changes reminiscent of those sometimes observed after tendon allografts. Although the radiological changes reported here may not affect the graft fixation, the authors have reverted to using metallic interference screws. PMID:9586250

  6. Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability : Comparison with Bilateral Method

    PubMed Central

    Hue, Yun Hee; Yi, Hyeong-Joong; Oh, Seong Hoon; Oh, Suck Jun; Ko, Yong

    2009-01-01

    Objective Bilateral C1-2 transarticular screw fixation (TAF) with interspinous wiring has been the best treatment for atlantoaxial instability (AAI). However, several factors may disturb satisfactory placement of bilateral screws. This study evaluates the usefulness of unilateral TAF when bilateral TAF is not available. Methods Between January 2003 and December 2007, TAF was performed in 54 patients with AAI. Preoperative studies including cervical x-ray, three dimensional computed tomogram, CT angiogram, and magnetic resonance image were checked. The atlanto-dental interval (ADI) was measured in preoperative period, immediate postoperatively, and postoperative 1, 3 and 6 months. Results Unilateral TAF was performed in 27 patients (50%). The causes of unilateral TAF were anomalous course of vertebral artery in 20 patients (74%), severe degenerative arthritis in 3 (11%), fracture of C1 in 2, hemangioblastoma in one, and screw malposition in one. The mean ADI in unilateral group was measured as 2.63 mm in immediate postoperatively, 2.61 mm in 1 month, 2.64 mm in 3 months and 2.61 mm in 6 months postoperatively. The mean ADI of bilateral group was also measured as following; 2.76 mm in immediate postoperative, 2.71 mm in 1 month, 2.73 mm in 3 months, 2.73 mm in 6 months postoperatively. Comparison of ADI measurement showed no significant difference in both groups, and moreover fusion rate was 100% in bilateral and 96.3% in unilateral group (p=0.317). Conclusion Even though bilateral TAF is best option for AAI in biomechanical perspectives, unilateral screw fixation also can be a useful alternative in otherwise dangerous or infeasible cases through bilateral screw placement. PMID:19352478

  7. Open reduction and internal fixation of patellar fractures with tension band wiring through cannulated screws.

    PubMed

    Malik, Mudasir; Halwai, Manzoor Ahmad

    2014-10-01

    The purpose of this study was to evaluate effectiveness and safety of a relatively new technique of open reduction and internal fixation of displaced transverse patellar fractures with tension band wiring (TBW) through parallel cannulated compression screws. A total of 30 patients with displaced transverse patellar fracture were enrolled in this prospective study. Of the 30 patients, 20 patients had trauma due to fall, 5 due to road traffic accident, 2 due to fall of heavy object on the knee, 2 due to forced flexion of knee, and 1 had fracture due to being beaten. All 30 patients were treated with vertical skin exposure, fracture open reduction, and internal fixation by anterior TBW through 4.0?mm cannulated screws. The postoperative rehabilitation protocol was standardized. The patients were followed postsurgery to evaluate time required for radiographic bone union, knee joint range of motion (ROM), loss of fracture reduction, material failure, and the overall functional result of knee using Bostman scoring. All the fractures healed radiologically, at an average time of 10.7 weeks (range, 8-12 weeks). The average ROM arc was 129.7 degrees (range, 115-140 degrees). No patient had loss of fracture reduction, implant migration, or material failure. The average Bostman score was 28.6 out of 30. Anterior TBW through cannulated screws for displaced transverse fractures is safe and effective alternative treatment. Good functional results and recovery can be expected. PMID:24414389

  8. Effects of Lateral Mass Screw Rod Fixation to the Stability of Cervical Spine after Laminectomy

    NASA Astrophysics Data System (ADS)

    Rosli, Ruwaida; Kashani, Jamal; Kadir, Mohammed Rafiq Abdul

    There are many cases of injury in the cervical spine due to degenerative disorder, trauma or instability. This condition may produce pressure on the spinal cord or on the nerve coming from the spine. The aim of this study was, to analyze the stabilization of the cervical spine after undergoing laminectomy via computational simulation. For that purpose, a three-dimensional finite element (FE) model for the multilevel cervical spine segment (C1-C7) was developed using computed tomography (CT) data. There are various decompression techniques that can be applied to overcome the injury. Usually, decompression procedures will create an unstable spine. Therefore, in these situations, the spine is often surgically restabilized by using fusion and instrumentation. In this study, a lateral mass screw-rod fixation was created to stabilize the cervical spine after laminectomy. Material properties of the titanium alloy were assigned on the implants. The requirements moments and boundary conditions were applied on simulated implanted bone. Result showed that the bone without implant has a higher flexion and extension angle in comparison to the bone with implant under applied 1Nm moment. The bone without implant has maximum stress distribution at the vertebrae and ligaments. However, the bone with implant has maximum stress distribution at the screws and rods. Overall, the lateral mass screw-rod fixation provides stability to the cervical spine after undergoing laminectomy.

  9. Experimental and Numerical Analysis of Screw Fixation in Anterior Cruciate Ligament Reconstruction

    NASA Astrophysics Data System (ADS)

    Chizari, Mahmoud; Wang, Bin; Snow, Martyn; Barrett, Mel

    2008-09-01

    This paper reports the results of an experimental and finite element analysis of tibial screw fixation in anterior cruciate ligament (ACL) reconstruction. The mechanical properties of the bone and tendon graft are obtained from experiments using porcine bone and bovine tendon. The results of the numerical study are compared with those from mechanical testing. Analysis shows that the model may be used to establish the optimum placement of the tunnel in anterior cruciate ligament reconstruction by predicting mechanical parameters such as stress, strain and displacement at regions in the tunnel wall.

  10. Balancing Rigidity and Safety of Pedicle Screw Fixation via a Novel Expansion Mechanism in a Severely Osteoporotic Model

    PubMed Central

    Shea, Thomas M.; Doulgeris, James J.; Gonzalez-Blohm, Sabrina A.; Lee, William E.; Vrionis, Frank D.

    2015-01-01

    Many successful attempts to increase pullout strength of pedicle screws in osteoporotic bone have been accompanied with an increased risk of catastrophic damage to the patient. To avoid this, a single-armed expansive pedicle screw was designed to increase fixation strength while controlling postfailure damage away from the nerves surrounding the pedicle. The screw was then subsequently tested in two severely osteoporotic models: one representing trabecular bone (with and without the presence of polymethylmethacrylate) and the other representing a combination of trabecular and cortical bone. Maximum pullout strength, stiffness, energy to failure, energy to removal, and size of the resulting block damage were statistically compared among conditions. While expandable pedicle screws produced maximum pullout forces less than or comparable to standard screws, they required a higher amount of energy to be fully removed from both models. Furthermore, damage to the cortical layer in the composite test blocks was smaller in all measured directions for tests involving expandable pedicle screws than those involving standard pedicle screws. This indicates that while initial fixation may not differ in the presence of cortical bone, the expandable pedicle screw offers an increased level of postfailure stability and safety to patients awaiting revision surgery. PMID:25705655

  11. Biomechanical Comparison Between Bashti Bone Plug Technique and Biodegradable Screw for Fixation of Grafts in Ligament surgery

    PubMed Central

    Bashti, Kaveh; Tahmasebi, Mohammad N; Kaseb, Hasan; Farahmand, Farzam; Akbar, Mohammad; Mobini, Amir

    2015-01-01

    Background: Ligament reconstruction is a common procedure in orthopedic surgery. Although several popular techniques are currently in use, new methods are proposed for secure fixation of the tendon graft into the bone tunnel. Purposes: We sought to introduce our new technique of Bashti bone plug for fixation of soft tissue graft in anterior cruciate ligament (ACL) reconstruction and to compare its biomechanical features with conventional absorbable interference screw technique in a bovine model. Methods: Twenty pairs of bovine knees were harvested after death. Soft tissue was removed and the Achilles tendon was harvested to be used as an ACL graft. It was secured into the bone tunnel on the tibial side via two different methods: Bashti Bone Plug technique and conventional screw method. Biomechanical strength was measured using 200 N and 300 N cyclic loading on the graft. Pull out strength was also tested until the graft fails. Results: No graft failure was observed after 200 N and 300 N cyclic loading in either fixation methods. When testing for pull out failure, 21 tendons (53%) were torn and 19 tendons (48%) slipped out. No fixation failure occurred, which did not reveal a significant difference between the bone plug or interference screw group (P=0.11). The mean pull out force until failure of the graft was 496±66 N in the screw group and 503±67 N in the bone plug group (P=0.76). Conclusions: Our suggested fixation technique of Bashti bone plug is a native, cheap, and feasible method that provides comparable biomechanical strength with interference screw when soft tissue fixation was attempted in bovine model. PMID:25692166

  12. Minimally invasive percutaneous screw fixation of traumatic spondylolisthesis of the axis.

    PubMed

    Buchholz, Avery Lee; Morgan, Steven L; Robinson, Leslie C; Frankel, Bruce M

    2015-05-01

    OBJECT Most cases of traumatic spondylolisthesis of the axis (hangman's fracture) can be treated nonoperatively with reduction and subsequent immobilization in a rigid cervical collar or halo. However, in some instances, operative management is necessary and can be accomplished by using either anterior or posterior fusion techniques. Because open posterior procedures can result in significant blood loss, pain, and limited cervical range of motion, other less invasive options for posterior fixation are needed. The authors describe a minimally invasive, navigation-guided technique for surgical treatment of Levine-Edwards (L-E) Type II hangman's fractures. METHODS For 5 patients with L-E Type II hangman's fracture requiring operative reduction and internal fixation, percutaneous screw fixation directed through the fracture site was performed. This technique was facilitated by use of intraoperative 3D fluoroscopy and neuronavigation. RESULTS Of the 5 patients, 2 were women, 3 were men, and age range was 46-67 years. No intraoperative or postoperative complications occurred. All patients wore a rigid cervical collar, and flexion-extension radiographs were obtained at 6 months. For all patients, dynamic imaging demonstrated a stable construct. CONCLUSIONS L-E type II hangman's fractures can be safely repaired by using percutaneous minimally invasive surgical techniques. This technique may be appropriate, depending on circumstances, for all L-E Type I and II hangman's fractures; however, the degree of associated ligament injury and disc disruption must be accounted for. Percutaneous fixation is not appropriate for L-E Type III fractures because of significant displacement and ligament and disc disruption. This report is meant to serve as a feasibility study and is not meant to show superiority of this procedure over other surgical options. PMID:25723118

  13. Biomechanical Analysis of Fusion Segment Rigidity Upon Stress at Both the Fusion and Adjacent Segments: A Comparison between Unilateral and Bilateral Pedicle Screw Fixation

    PubMed Central

    Kim, Ho-Joong; Kang, Kyoung-Tak; Chang, Bong-Soon; Lee, Choon-Ki; Kim, Jang-Woo

    2014-01-01

    Purpose The purpose of this study was to investigate the effects of unilateral pedicle screw fixation on the fusion segment and the superior adjacent segment after one segment lumbar fusion using validated finite element models. Materials and Methods Four L3-4 fusion models were simulated according to the extent of decompression and the method of pedicle screws fixation in L3-4 lumbar fusion. These models included hemi-laminectomy with bilateral pedicle screw fixation in the L3-4 segment (BF-HL model), total laminectomy with bilateral pedicle screw fixation (BF-TL model), hemi-laminectomy with unilateral pedicle screw fixation (UF-HL model), and total laminectomy with unilateral pedicle screw fixation (UF-TL model). In each scenario, intradiscal pressures, annulus stress, and range of motion at the L2-3 and L3-4 segments were analyzed under flexion, extension, lateral bending, and torsional moments. Results Under four pure moments, the unilateral fixation leads to a reduction in increment of range of motion at the adjacent segment, but larger motions were noted at the fusion segment (L3-4) in the unilateral fixation (UF-HL and UF-TL) models when compared to bilateral fixation. The maximal von Mises stress showed similar patterns to range of motion at both superior adjacent L2-3 segments and fusion segment. Conclusion The current study suggests that unilateral pedicle screw fixation seems to be unable to afford sufficient biomechanical stability in case of bilateral total laminectomy. Conversely, in the case of hemi-laminectomy, unilateral fixation could be an alternative option, which also has potential benefit to reduce the stress of the adjacent segment. PMID:25048501

  14. Analysis of the Stress and Displacement Distribution of Inferior Tibiofibular Syndesmosis Injuries Repaired with Screw Fixation: A Finite Element Study

    PubMed Central

    Liu, Qinghua; Zhang, Kun; Zhuang, Yan; Li, Zhong; Yu, Bin; Pei, Guoxian

    2013-01-01

    Background Studies of syndesmosis injuries have concentrated on cadaver models. However, they are unable to obtain exact data regarding the stress and displacement distribution of various tissues, and it is difficult to compare models. We investigated the biomechanical effects of inferior tibiofibular syndesmosis injuries (ITSIs) and screw fixation on the ankle using the finite element (FE) method. Methodology/Principal Findings A three-dimensional model of a healthy ankle complex was developed using computed tomography (CT) images. We established models of an ITSI and of screw fixation at the plane 2.5 cm above and parallel to the tibiotalar joint surface of the injured syndesmosis. Simulated loads were applied under three conditions: neutral position with single-foot standing and internal and external rotation of the ankle. ITSI reduced contact forces between the talus and fibula, helped periarticular ankle ligaments withstand more load-resisting movement, and increased the magnitude of displacement at the lower extreme of the tibia and fibula. ITSI fixation with a syndesmotic screw reduced contact forces in all joints, decreased the magnitude of displacement at the lower extreme of the tibia and fibula, and increased crural interosseous membrane stress. Conclusions/significance Severe syndesmosis injuries cause stress and displacement distribution of the ankle to change multidirectional ankle instability and should be treated by internal fixation. Though the transverse syndesmotic screw effectively stabilizes syndesmotic diastasis, it also changes stress distribution around the ankle and decreases the joint's range of motion (ROM). Therefore, fixation should not be performed for a long period of time because it is not physiologically suitable for the ankle joint. PMID:24312464

  15. Transarticular screw fixation of C1-2 for the treatment of arthropathy-associated occipital neuralgia.

    PubMed

    Pakzaban, Peyman

    2011-02-01

    Two patients with occipital neuralgia due to severe arthropathy of the C1-2 facet joint were treated using atlantoaxial fusion with transarticular screws without decompression of the C-2 nerve root. Both patients experienced immediate postoperative relief of occipital neuralgia. The resultant motion elimination at C1-2 eradicated not only the movement-evoked pain, but also the paroxysms of true occipital neuralgia occurring at rest. A possible pathophysiological explanation for this improvement is presented in the context of the ignition theory of neuralgic pain. This represents the first report of C1-2 transarticular screw fixation for the treatment of arthropathy-associated occipital neuralgia. PMID:21214317

  16. Placement of occipital condyle screws for occipitocervical fixation in a pediatric patient with occipitocervical instability after decompression for Chiari malformation.

    PubMed

    Bekelis, Kimon; Duhaime, Ann-Christine; Missios, Symeon; Belden, Clifford; Simmons, Nathan

    2010-08-01

    In cadaveric studies and recently in one adult patient the occipital condyle has been studied as an option to allow bone purchase by fixation devices. In the current case the authors describe the use of occipital condyle screws in a child undergoing occipitocervical fixation. To the best of the authors' knowledge this case is the first reported instance of this technique in a pediatric patient. This girl had a history of posterior fossa decompression for Chiari malformation Type I when she was 22 months of age. When she was 6 years old she presented with neck pain on flexion and extension of her head. Magnetic resonance imaging in flexion and extension revealed occipitocervical instability. She underwent an occiput to C-2 posterior arthrodesis with bilateral screw placement in the occipital condyles, C-2 lamina, and C-1 lateral masses. Postoperatively, she was neurologically intact. Computed tomography demonstrated a stable construct, and her cervical pain had resolved on follow-up. PMID:20672939

  17. Effect of Crosslinks on the Stability of the Spine and the Pedicle Screw Fixation.

    PubMed

    Xiang-Yu, Zhang; Feng, S U; Shi, Yan; Zhi-Min, Zhang; Pei-Nan, Zhang

    2015-06-30

    Objective To evaluate the effect of crosslinks on the stability of the spine and pedicle screws. Methods Compression fracture of the L1 vertebra was produced in 30 fresh thoracic and lumbar vertebrae samples obtained from adult sheep,which were divided into 3 groups(n=10)with lot-drawing method. Four screws were fixed onto the superior and inferior pedicles of vertebral arch close to the fractured vertebrae,with different number of crosslinks(0 in Group A,1 in Group B,and 2 in Group C)on the rods. After fixation,the samples were subject to 10 000 times of fatigue test with 1.5 Hz load on the HY-3080 computer-control electronic universal test machine and HY-1000NM computer-control torsion test machine. The axial compressive stiffness,maximum pullout strength,and range of motion(ROM)of 6 directions,i.e.,flexion,extension,left and right lateral bending,and left and right axial rotation of the 3 groups were measured and compared. Results There were no statistically significant differences in axial compressive stiffness as well as the ROM of flexion,extension,and left and right lateral bending(all P>0.05). The maximum pullout strength was significantly smaller in Group A and Group B than in Group C [(129.56±29.63)N vs.(294.67±23.25)N,P=0.000;(254.02±36.29)vs.(294.67±23.25)N,P=0.006]. The ROM of left axial rotation was the highest in Group A(13.35°±1.06°),followed by Group B(12.23°±1.06°)and Group C(11.04°±0.74°)(F=13.44,P=0.000;Group B vs. Group A,P=0.000;Group B vs. Group C,P=0.001;Group C vs. Group A,P=0.000). The ROM of right axial rotation was also the highest in Group A(13.56°±1.15°),lower in Group B(12.39°±1.01°)and the lowest in Group C(10.81°±0.51°)(F=21.91,P=0.000;Group B vs. Group A,P=0.002;Group B vs. Group C,P=0.001;Group C vs. Group A,P=0.000). Conclusion Crosslinks may reinforce the pullout strength of the screws and improve the axial stability of the spine. PMID:26149138

  18. Anterior transpedicular screw fixation of cervical spine: Is it safe? Morphological feasibility, technical properties, and accuracy of manual insertion.

    PubMed

    Koktekir, Ender; Toktas, Zafer Orkun; Seker, Askin; Akakin, Akin; Konya, Deniz; Kilic, Turker

    2015-06-01

    OBJECT Due to lack of construct stability of the current anterior cervical approaches, supplemental posterior cervical approaches are frequently employed. The use of an anterior-only approach with anterior transpedicular screws (ATPSs) has been proposed as a means of providing 3-column fixation. This study was designed to investigate the feasibility of anterior transpedicular screw (ATPS) fixation of cervical spine, to obtain the morphological measurements for technical prerequisites, and to evaluate the accuracy of the ATPS using fluoroscopy. METHODS The study included both radiological and anatomical investigations. The radiological investigations were based on data from cervical spine CT scans performed in 65 patients. Technical prerequisites of ATPS were calculated using OsiriX for Mac OS. In the anatomical part of the study, 30 pedicles (C3-7) from 6 formalin-preserved cadavers were manually instrumented. Measurements obtained included pedicle width (PW), pedicle height (PH), pedicle transverse angle (PTA), distance of the entry point from the midline (DEPM), and distance of the entry point from the superior endplate (DEPSEP). The authors also analyzed screw position in the manually instrumented vertebrae. RESULTS The mean PW and PH values showed a tendency to increase from C-3 to C-7 in both males and females. The means were significantly larger for both PW and PH in males than in females at all levels (p = 0.001). The overall mean PTA value was significantly lower at C-7 (p < 0.0001). The mean value for the distance of entry point from the midline (DEPM) represented a point at the contralateral side of the pedicle for every level except C-7. The mean DEPSEP values showed significant differences between all levels (p < 0.0001). Seven of the 30 screws were identified as breaching the pedicle (23.3%); these screw malplacements were seen at C-3 (3 screws), C-4 (2 screws), and C-5 (2 screws). CONCLUSIONS The morphological measurements of this study demonstrated that ATPS fixation is feasible in selected cases. They indicate that ATPS insertion using a fluoroscopy-assisted pedicle axis view is safe at the C-6 and C-7 levels, but the results at the other levels did not prove the safety of this technique. PMID:25815805

  19. Titanium-alloy enhances bone-pedicle screw fixation: mechanical and histomorphometrical results of titanium-alloy versus stainless steel

    Microsoft Academic Search

    Finn Bjarke Christensen; Michel Dalstra; Flemming Sejling; Søren Overgaard; Cody Bünger

    2000-01-01

    Several types of pedicle screw systems have been utilized to augment lumbar spine fusion. The majority of these systems are\\u000a made of stainless steel (Ss), but titanium-alloy (Ti-alloy) devices have recently been available on the market. Ti-alloy implants\\u000a have several potential advantages over Ss ones. High bioactivity and more flexibility may improve bone ingrowth and mechanical\\u000a fixation, and the material

  20. Analysis of failure following anterior screw fixation of Type II odontoid fractures in geriatric patients.

    PubMed

    Osti, Michael; Philipp, Helmut; Meusburger, Berthold; Benedetto, Karl Peter

    2011-11-01

    Anterior screw fixation of Type II odontoid fractures has been recommended. Only few publications analyse the mechanism of failure in geriatric patients. We reviewed 18 male and 15 female patients aged 65 and above for parameters that influence the development of postoperative loss of correction, delayed union or non-union. Patients were stratified in two groups: 21 cases in Group A (union) and 12 patients in Group B (loss of correction, delayed union, non-union, revision surgery). Statistically significant correlation (p < 0.05) could be detected between failure to heal and: (1) degenerative changes in the atlanto-odontoid joint, (2) severity of osteoporosis in the odontoid process, (3) posterior oblique fracture type, (4) suboptimal fracture reduction, (5) suboptimal position of implant following demanding intraoperative conditions, (6) quality of fracture compression and (7) severity of fracture comminution. The overall morbidity and mortality rates were 29.0 and 8.6%, respectively. Our results indicate that these factors should be addressed regarding the selection of the operative treatment method in the geriatric patient. PMID:21728075

  1. When Planning Screw Fracture Fixation Why the 5.5?mm Screw is the Goldilocks Screw. An Observational Computer Tomographic Study of Fifth Metatarsal Bone Anatomy in a Sample of Patients.

    PubMed

    Iselin, Lukas D; Ramawat, Sunil; Hanratty, Brian; Klammer, Georg; Stavrou, Peter

    2015-05-01

    We wanted to verify our clinical experience that the 5.5?mm screw was ideal in the majority of fifth metatarsal fracture fixation. The size of a screw is important for the successful surgical treatment of these fractures in order to obtain the maximal stability while reducing the risk for iatrogenic fracture.A sample of patients undergoing computer tomographic imaging of the foot for investigation other than fifth metatarsal pathology were recruited. The parameters of the fifth metatarsal bone anatomy were measured.These parameters of the 5.5?mm screw were correlated with this data. The upper parameter (the diameter of the threads) was 5.5 and the lower parameter (the diameter of the shank) was 4.0?mm.Twenty seven patients were recruited.The proximal third internal diameter ranged from 3.6 to 7.0?mm with a mean of 5.0?mm. 93% of the metatarsals could easily accommodate the 5.5?mm screw. Two of the metatarsals had an internal diameter of < 4?mm (7%).It is our belief that the 5.5?mm screw may be used safely in the majority of patients with fifth metatarsal fractures. PMID:25950685

  2. CT-based morphometric analysis of C1 laminar dimensions: C1 translaminar screw fixation is a feasible technique for salvage of atlantoaxial fusions

    PubMed Central

    Yew, Andrew; Lu, Derek; Lu, Daniel C.

    2015-01-01

    Background: Translaminar screw fixation has become an alternative in the fixation of the axial and subaxial cervical spine. We report utilization of this approach in the atlas as a salvage technique for atlantoaxial stabilization when C1 lateral mass screws are precluded. To assess the feasibility of translaminar fixation at the atlas, we have characterized the dimensions of the C1 lamina in the general adult population using computed tomography (CT)-based morphometry. Methods: A 46-year-old male with symptomatic atlantoaxial instability secondary to os odontoideum underwent bilateral C1 and C2 translaminar screw/rod fixation as C1 lateral mass fixation was precluded by an anomalous vertebral artery. The follow-up evaluation 2½ years postoperatively revealed an asymptomatic patient without recurrent neck/shoulder pain or clinical signs of instability. To better assess the feasibility of utilizing this approach in the general population, we retrospectively analyzed 502 consecutive cervical CT scans performed over a 3-month period in patients aged over 18 years at a single institution. Measurements of C1 bicortical diameter, bilateral laminar length, height, and angulation were performed. Laminar and screw dimensions were compared to assess instrumentation feasibility. Results: Review of CT imaging found that 75.9% of C1 lamina had a sufficient bicortical diameter, and 63.7% of C1 lamina had sufficient height to accept bilateral translaminar screw placement. Conclusions: CT-based measurement of atlas morphology in the general population revealed that a majority of C1 lamina had sufficient dimensions to accept translaminar screw placement. Although these screws appear to be a feasible alternative when lateral mass screws are precluded, further research is required to determine if they provide comparable fixation strength versus traditional instrumentation methods. PMID:26005585

  3. Interference Screw Fixation of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction: Part 1Effect of Tunnel Compaction by Serial Dilators Versus Extraction Drilling on the Initial Fixation Strength

    Microsoft Academic Search

    Janne T. Nurmi; Pekka Kannus; Harri Sievänen; Timo Järvelä; Markku Järvinen; Teppo L. N. Järvinen

    2004-01-01

    Background:Compaction of the bone-tunnel walls by serial dilation is believed to enhance the interference screw fixation strength of the soft tissue grafts in anterior cruciate ligament (ACL) reconstruction.Hypothesis:Serial dilation enhances the fixation strength of soft tissue grafts in ACL reconstruction over extraction drilling.Study Design:Randomized experimental study.Methods:Initial fixation strength of the doubled anterior tibialis tendon grafts (fixed with a bioabsorbable interference

  4. Three-dimensional image navigation system-assisted anterior cervical screw fixation for treatment of acute odontoid fracture

    PubMed Central

    Zou, Debo; Zhang, Kaining; Ren, Yanjun; Wu, Yingguang; Yang, Yun; Li, Yu

    2014-01-01

    This study is to investigate the role of three-dimensional image navigation system for surgical treatment of odontoid fracture. A total of 21 patients were enrolled in this study. The anterior cervical hollow screw fixation was performed for treatment of acute odontoid fracture under monitoring of isocentric C-arm three-dimensional navigation system (Iso-C 3D) navigation system. The postoperative follow-up investigation duration was 13.8 ± 4.4 months. Twenty patients with odontoid fracture had bone union without intraoperative and postoperative complications. No loosening, dislocation or fracture of screw occurred. The average healing time was from 3 to 4 months. The cervical postoperative organ function evaluation of patients was scored by Smiley-Webster scoring methods. Eighteen cases were scored as excellent; 2 cases were scored as fine; 1 case was scored as good; and no case was scored as poor. Iso-C 3D image navigation system-assisted anterior cervical screw fixation is an effective approach for treatment of odontoid fracture. PMID:25550950

  5. Subsidence of metal interbody cage after posterior lumbar interbody fusion with pedicle screw fixation.

    PubMed

    Tokuhashi, Yasuaki; Ajiro, Yasumitsu; Umezawa, Natsuki

    2009-04-01

    Posterior lumbar interbody fusion is considered to be an excellent fusion procedure to stabilize anterior support, correct alignment in the sagittal and coronal plane, and achieve foraminal decompression by lifting the disk height. The metal interbody cage in posterior lumbar interbody fusion is thought to be useful to prevent collapse of the graft bone and to correct and maintain disk height; however, some studies have noted a gradual decrease of disk height due to cage subsidence. Therefore, to investigate the significance of cage subsidence, 86 disk levels radiographically confirmed to have good union in 66 patients with posterior lumbar interbody fusion combined with pedicle screw fixation and a single metal cage for degenerative lumbar disease were retrospectively evaluated. The follow-up period ranged from 3 years to 10 years 3 months, with a mean of 7 years 9 months. Cage subsidence often showed a gradual increase over time. At final follow-up, subsidence averaged 4.0 mm on the cranial surface and 2.7 mm on the caudal surface. Although the average increase of disk height was 3.2 mm immediately postoperatively, the final disk height decreased by 4.2 mm on average from that time. The degree of cage subsidence and decrease of disk height were not correlated with the final clinical results. Subsidence was not correlated with bone mineral density in the vertebral body, body weight, or site of the insertion. On the other hand, the wedge shape of the cage and the thickness of the resected endplate had a significant influence on cage subsidence. PMID:19388615

  6. Comparison of the tissue response to absorbable self-reinforced polylactide screws and metallic screws in the fixation of cancellous bone osteotomies: an experimental study on the rabbit distal femur.

    PubMed

    Viljanen, J T; Pihlajamäki, H K; Törmälä, P O; Rokkanen, P U

    1997-05-01

    The availability of absorbable fracture-fixation devices for clinical use calls for better knowledge of the reaction of bone tissue to absorbable polyester implants as compared with similar metallic devices. To examine and compare the tissue response to biodegradable and metallic screws within cancellous bone, a transverse transcondylar osteotomy of the distal femur was fixed with absorbable self-reinforced polylevolactide screws in 35 rabbits and with stainless-steel screws in 35 rabbits. New bone formation and consolidation of the osteotomy were examined histologically, histomorphometrically, and microradiographically within standardized sample fields 1, 3, 6, 12, 24, 36, and 48 weeks postoperatively. The intact contralateral femur served as the control. A vigorous osteoconductive response to the polylevolactide screws was observed at 3 weeks postoperatively, and the osteoid surface fraction was significantly higher in all follow-ups than in the contralateral femora. In the femora with metallic screws, new bone formation was seen 3, 6, and 12 weeks postoperatively, but at 24, 36, and 48 weeks the osteoid surface fraction did not differ significantly from that of the intact control femora. The total bone area was significantly larger in the femora with self-reinforced polylevolactide screws than in the control bone 6-48 weeks postoperatively; in the femora with metallic screws, this was found only at 6 and 12 weeks. After 48 weeks, the femora fixed with metallic screws had statistically smaller total bone area than the intact control femora. Solid bone union was seen in 84% of the osteotomies in the self-reinforced polylevolactide group and in 76% of those in the metallic group after 3 weeks or more. No signs of degradation of the self-reinforced polyleuolactide implant and only a mild foreign-body reaction with no accumulations of inflammatory cells to either self-reinforced polylevolactide or metallic screws were observed during the follow-up period. Both types of screws seemed to induce an osteostimulatory response around their threads. This phenomenon was transient for metallic screws but lasted for at least 48 weeks for self-reinforced polylevolactide screws. The polylevolactide screw does not seem to cause osteopenia at the implantation site. The fixation properties of both self-reinforced polylevolactide screws and metallic screws appear to be sufficient for the fixation of small fragments of cancellous bone. PMID:9246086

  7. Intraoperative Computed Tomography Navigation for Transpedicular Screw Fixation to Treat Unstable Thoracic and Lumbar Spine Fractures: Clinical Analysis of a Case Series (CARE-Compliant).

    PubMed

    Lee, Ching-Yu; Wu, Meng-Huang; Li, Yen-Yao; Cheng, Chin-Chang; Hsu, Chu-Hsiang; Huang, Tsung-Jen; Hsu, Robert Wen-Wei

    2015-05-01

    Transpedicular screw (TPS) fixation in unstable thoracic and lumbar (TL) spine fractures remains technically difficult because of destroyed anatomical landmarks, unstable gross segments, and discrepancies in anatomic orientation using conventional anatomic landmarks, fluoroscopic guidance, or computed tomography (CT)-based navigation. In this study, we evaluated the safety and accuracy of TPS placement under intraoperative computed tomography (iCT) navigation in managing unstable TL spine fractures.From 2010 to 2013, we retrospectively reviewed the Spine Operation Registry records of patients who underwent posterior instrumented fusion to treat unstable TL spine fractures via the iCT navigation system. An unstable spine fracture was identified as AO/Magerl classification type B or type C.In all, 316 screws in 37 patients with unstable TL spine fractures were evaluated and involved 7 thoracic, 23 thoracolumbar junctional, and 7 lumbar fractures. The accuracy of TPS positioning in the pedicle without breach was 98% (310/316). The average number of iCT scans per patient was 2.1 (range 2-3). The average total radiation dose to patients was 15.8?mSv; the dose per single level exposure was 2.7?mSv. The TPS intraoperative revision rate was 0.6% (2/316) and no neurovascular sequela was observed. TPS fixation using the iCT navigation system obtained a 98% accuracy in stabilizing unstable TL spine fractures. A malplaced TPS could be revised during real-time confirmation of the TPS position, and no secondary operation was required to revise malplaced screws.The iCT navigation system provides accurate and safe management of unstable TL spine fractures. In addition, operating room personnel, including surgeons and nurses, did not need to wear heavy lead aprons as they were not exposed to radiation. PMID:25997042

  8. C1-C3 Lateral Mass Screw-Rod Fixation and Fusion for C2 Pathologies and Hangman's Fractures

    PubMed Central

    Haque, Mohammod Raziul

    2014-01-01

    Study Design Retrospective clinical study. Purpose We report our experience of eight patients treated with C1-C3 lateral mass rod-screw stabilization and fusion in the treatment of Hangman's fracture and other axis pathologies. Overview of Literature Different surgical approaches, both anterior and posterior, have been described for treating Hangman's fracture and other pathologies where surgery is indicated. Methods All patients who underwent surgical treatment for Hangman's fracture and axial pathology where C1-C3 lateral mass screw-rod stabilization and fusion done, following reduction of the fracture or removal of the pathology were included in this series. The recorded patient management data was retrospectively studied. Results There were 8 cases in total. All were male, with an average age of 40.75 years. Hangman's fracture occurred in 6 cases (75%), one with metastatic squamous cell carcinoma and the remaining with plasmocytoma. Among the Hangman's fractures 4 (66.66%) had no neuro-deficit. Reduction and bilateral C1-C3 lateral mass screw and rod fixation with posterior fusion by bone graft was performed in all cases. In 2 cases, a C2 body tumor was removed transorally. All patients with neuro-deficit fully recovered, except one who expired in the early post-operative period. Rest of all patients were leading a normal life till last follow up. Conclusions Although the number of cases was very small with a relatively short follow up period, C1 and C3 lateral mass screw-rod fixation followed by fusion showed promise as an effective and biomechanically sound way for the treatment of properly selected Hangman's fracture cases, and may also be suitable in other axial pathologies. PMID:25558315

  9. A single-stage posterior approach with open reduction and pedicle screw fixation in subaxial cervical facet dislocations.

    PubMed

    Park, Jin Hoon; Roh, Sung Woo; Rhim, Seung Chul

    2015-07-01

    OBJECT The optimal treatment for cervical facet dislocations is controversial, but the generally accepted process recommends an initial closed reduction with the next step determined according to the success of the closed reduction and the presence of traumatic disc herniation. This study aimed to show the efficacy of a posterior approach performed with an open reduction and pedicle screw fixation with removal of disc particles, if required, in the management of subaxial cervical dislocations. METHODS Between March 2012 and September 2013, 21 consecutive patients with cervical facet dislocations were enrolled. The affected levels were as follows: 4 at C3-4; 2 at C4-5; 5 at C5-6; and 10 at the C6-7 level. Seven patients had traumatic disc herniations. Closed reduction was not attempted; a prompt posterior cervical surgery was performed instead. After open reduction, pedicle screw fixation was performed. In cases with traumatic disc herniation, herniated disc fragments were excised via a posterolateral approach and successful decompressions were determined by postoperative MRI studies. Clinical outcomes were assessed using the American Spinal Injury Association (ASIA) grading system. Radiological outcomes were assessed by comparing the degree of subluxation and the angle of segmental lordosis between pre- and postoperative CT scans. RESULTS All patients improved neurologically. The mean segmental angles improved from 7.3° ± 8.68° to -5.9° ± 4.85°. The mean subluxation improved from 23.4% ± 16.52% to 2.6% ± 7.19%. Disc fragments were successfully removed from the 7 patients with herniated discs, as shown on MRI. CONCLUSIONS Open reduction followed by pedicle screw fixation or posterolateral removal of herniated disc fragments is a good treatment option for cervical facet dislocations. PMID:25909272

  10. Posterior short segment pedicle screw fixation and TLIF for the treatment of unstable thoracolumbar/lumbar fracture

    PubMed Central

    2014-01-01

    Background Currently, Posterior Short Segment Pedicle Screw Fixation is a popular procedure for treating unstable thoracolumbar/lumbar burst fracture. But progressive kyphosis and a high rate of hardware failure because of lack of the anterior column support remains a concern. The efficacy of different methods remains debatable and each technique has its advantages and disadvantages. Methods A consecutive series of 20 patients with isolated thoracolumbar/lumbar burst fractures were treated by posterior short segment pedicle screw fixation and transforaminal thoracolumbar/lumbar interbody fusion (TLIF) between January 2005 and December 2007. All patients were followed up for a minimum of 2 years. Demographic data, neurologic status, anterior vertebral body heights, segmental Cobb angle and treatment-related complications were evaluated. Results The mean operative time was 167 minutes (range, 150–220). Blood loss was 450 ~ 1200 ml, an average of 820 ml. All patients recovered with solid fusion of the intervertebral bone graft, without main complications like misplacement of the pedicle screw, nerve or vessel lesion or hard ware failure. The post-operative radiographs demonstrated a good fracture reduction and it was well maintained until the bone graft fusion. Neurological recovery of one to three Frankel grade was seen in 14 patients with partial neurological deficit, three grades of improvement was seen in one patient, two grades of improvement was observed in 6 patients and one grade of improvement was found in 6 patients. All the 6 patients with no paraplegia on admission remained neurological intact, and in one patient with Frankel D on admission no improvement was observed. Conclusion Posterior short-segment pedicle fixation in conjunction with TLIF seems to be a feasible option in the management of selected thoracolumbar/lumbar burst fractures, thereby addressing all the three columns through a single approach with less trauma and good results. PMID:24517217

  11. 3D Mapping of Safe and Danger Zones in the Maxilla and Mandible for the Placement of Intermaxillary Fixation Screws

    PubMed Central

    Purmal, Kathiravan; Alam, Mohammad Khursheed; Pohchi, Abdullah; Abdul Razak, Noor Hayati

    2013-01-01

    Intermaxillary (IMF) screws feature several advantages over other devices used for intermaxillary fixation, but using cone beam computed tomography (CBCT) scans to determine the safe and danger zones to place these devices for all patients can be expensive. This study aimed to determine the optimal interradicular and buccopalatal/buccolingual spaces for IMF screw placement in the maxilla and mandible. The CBCT volumetric data of 193 patients was used to generate transaxial slices between the second molar on the right to the second molar on the left in both arches. The mean interradicular and buccopalatal/buccolingual distances and standard deviation values were obtained at heights of 2, 5, 8 and 11 mm from the alveolar bone crest. An IMF screw with a diameter of 1.0 mm and length of 7 mm can be placed distal to the canines (2 - 11 mm from the alveolar crest) and less than 8 mm between the molars in the maxilla. In the mandible, the safest position is distal to the first premolar (more than 5 mm) and distal to the second premolar (more than 2 mm). There was a significant difference (p<0.05) between the right and left quadrants. The colour coding 3D template showed the safe and danger zones based on the mesiodistal, buccopalatal and buccolingual distances in the maxilla and mandible.The safest sites for IMF screw insertion in the maxilla were between the canines and first premolars and between the first and second molars. In the mandible, the safest sites were between the first and second premolars and between the second premolar and first molar. However, the IMF screw should not exceed 1.0 mm in diameter and 7 mm in length. PMID:24367643

  12. Continued growth of the hip after fixation of slipped capital femoral epiphysis using a single cannulated screw with a proximal threading

    Microsoft Academic Search

    Frédéric Sailhan; Aurélien Courvoisier; Océane Brunet; Franck Chotel; Jérôme Berard

    2011-01-01

    Background  The most commonly used method for unstable slipped capital femoral epiphysis (SCFE) remains in situ fixation. Depending on\\u000a the surgeon’s preference, screws or Kirschner wires are used for stabilizing the slipped upper femoral epiphysis. The purpose\\u000a of this study was to evaluate the ability of a single cannulated screw with a proximal threading to ensure stabilization,\\u000a growth, and remodeling of

  13. A Systematic Review and Meta-Analysis of Unilateral versus Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody Fusion

    PubMed Central

    Hu, Xu-Qi; Wu, Xin-Lei; Xu, Cong; Zheng, Xu-Hao; Jin, Yong-Long; Wu, Li-Jun; Wang, Xiang-Yang; Xu, Hua-Zi; Tian, Nai-Feng

    2014-01-01

    Background Transforaminal lumbar interbody fusion (TLIF) has become one of the most widely used procedures for lumbar spinal disorders. However, it is still unclear whether TLIF with unilateral pedicle screw (PS) fixation is as effective as that with bilateral PS fixation. We performed a meta-analysis of the literatures and aimed to gain a better understanding of whether TLIF with unilateral PS fixation was safe and effective for lumbar diseases. Methodology/Principal Findings We systematically searched Ovid, Springer, and Medline databases for relevant randomized controlled trials (RCTs) that compared the clinical and radiological outcomes of unilateral versus bilateral PS fixation in TLIF. Risk of bias in included studies was assessed using the Cochrane Risk of Bias tool. We generated pooled risk ratios or weighted mean differences across studies. According to our predefined inclusion criteria, seven RCTs with a total of 441 patients were included in this study. Baseline characteristics were similar between the unilateral and bilateral groups. Our meta-analysis showed that no significant difference was detected between the two groups in terms of postoperative clinical function, fusion status, reoperation rate, complication rate, and hospital stay (p>0.05). Pooled estimates revealed that the unilateral group was associated with significantly reduced implant cost, operative time and blood loss (p<0.05). Conclusions/Significances Our meta-analysis suggested TLIF with unilateral PS fixation was as safe and effective as that with bilateral PS fixation for lumbar diseases in selected patients. Despite these findings, our meta-analysis was based on studies with small sample size and different study characteristics that might lead to the inconsistent results such as various functional outcomes among the included studies. Therefore, high-quality randomized controlled trials with larger sample size are also needed to further clarify these issues and to provide the long-term outcomes. PMID:24489929

  14. Biodegradable wire fixation in olecranon and patella fractures combined with biodegradable screws or plugs and compared with metallic fixation

    Microsoft Academic Search

    T. Juutilainen; H. Patiälä; P. Rokkanen; P. Törmälä

    1995-01-01

    The outcome of olecranon and patella fractures fixed with biodegradable implants (self-reinforced poly-l-lactide wire combined with self-reinforced polyglycolide screw or self-reinforced poly-l-lactide plug) or with metallic implants (tension band wiring, Kirschner wire and metallic cerclage wire) was compared in a prospective, randomized study. Twenty-five olecranon fractures (15 with biodegradable implants and 10 with metallic ones) and 10 patella fractures (6

  15. The radiological feature of anterior occiput-to-axis screw fixation as it guides the screw trajectory on 3D printed models: a feasibility study on 3D images and 3D printed models.

    PubMed

    Wu, Ai-Min; Wang, Sheng; Weng, Wan-Qing; Shao, Zhen-Xuan; Yang, Xin-Dong; Wang, Jian-Shun; Xu, Hua-Zi; Chi, Yong-Long

    2014-12-01

    Anterior occiput-to-axis screw fixation is more suitable than a posterior approach for some patients with a history of posterior surgery. The complex osseous anatomy between the occiput and the axis causes a high risk of injury to neurological and vascular structures, and it is important to have an accurate screw trajectory to guide anterior occiput-to-axis screw fixation. Thirty computed tomography (CT) scans of upper cervical spines were obtained for three-dimensional (3D) reconstruction. Cylinders (1.75?mm radius) were drawn to simulate the trajectory of an anterior occiput-to-axis screw. The imitation screw was adjusted to 4 different angles and measured, as were the values of the maximized anteroposterior width and the left-right width of the occiput (C0) to the C1 and C1 to C2 joints. Then, the 3D models were printed, and an angle guide device was used to introduce the screws into the 3D models referring to the angles calculated from the 3D images. We found the screw angle ranged from ?1 (left: 4.99±4.59°; right: 4.28±5.45°) to ?2 (left: 20.22±3.61°; right: 19.63±4.94°); on the lateral view, the screw angle ranged from ?1 (left: 13.13±4.93°; right: 11.82±5.64°) to ?2 (left: 34.86±6.00°; right: 35.01±5.77°). No statistically significant difference was found between the data of the left and right sides. On the 3D printed models, all of the anterior occiput-to-axis screws were successfully introduced, and none of them penetrated outside of the cortex; the mean ?4 was 12.00±4.11 (left) and 12.25±4.05 (right), and the mean ?4 was 23.44±4.21 (left) and 22.75±4.41 (right). No significant difference was found between ?4 and ?4 on the 3D printed models and ?3 and ?3 calculated from the 3D digital images of the left and right sides. Aided with the angle guide device, we could achieve an optimal screw trajectory for anterior occiput-to-axis screw fixation on 3D printed C0 to C2 models. PMID:25526447

  16. Iatrogenic Injury of Profunda Femoris Artery Branches after Intertrochanteric Hip Screw Fixation for Intertrochanteric Femoral Fracture: A Case Report and Literature Review

    PubMed Central

    Koutsoumpelis, Andreas; Vergadis, Chrysovalantis; Mourikis, Anastasios; Georgopoulos, Sotiris E.

    2014-01-01

    A case of arterial rupture of the profunda femoris arterial branches, following dynamic hip screw (DHS) fixation for an intertrochanteric femoral fracture, is presented. Bleeding is controlled by coil embolization, but, later on, the patient underwent orthopedic material removal due to an infection of a large femoral hematoma. PMID:24716097

  17. Lag screw fixation of an extensor process fracture in a foal with flexural deformity.

    PubMed Central

    MacLellan, K N; MacDonald, D G; Crawford, W H

    1997-01-01

    A 4-month-old colt with stage I flexural deformity of the distal interphalangeal joint was diagnosed as having a type IV nondisplaced fracture of the extensor process of the 3rd phalanx. An inferior check ligament desmotomy and internal fixation of the fracture were performed. Favorable long-term results for internal fixation of extensor process fractures are presented. Images Figure 1a. Figure 1b. PMID:9105720

  18. Palmar Fixation of Dorsally Displaced Distal Radius Fractures Using Locking Plates with Smartlock Locking Screws

    Microsoft Academic Search

    T. C. WONG; C. C. YEUNG; Y. CHIU; S. H. YEUNG; F. K. IP

    2009-01-01

    We performed a prospective cohort study on a consecutive series of 35 unstable, dorsally displaced distal radius fractures, which were treated with palmar locking plates and SmartLock locking screws. There were 17 men and 18 women with a mean age of 44 years who were reviewed at a mean follow-up of 10 months. All the fractures healed at a mean

  19. [Sagittal splitting with screw fixation in patients with mesial bite wearing dentures--planning surgery and prosthetic design].

    PubMed

    Krenkel, Ch; Anthofer, R; Lixl, G

    1989-03-01

    In fully or partially edentulous patients with mesial bite undergoing surgical correction, the possibilities for avoiding intermaxillary fixation were studied. For stable osteosynthesis of mandibular osteotomies preoperative prostheses are needed in these patients to keep the jaws in their proper relation during surgery. This requires cephalic adjustment of the maxillary cast and articular adjustment of the mandibular cast in the articulator. The mandibular cast is shifted along an aluminum wedge designed to match the inclination of the occlusal plane until the alveolar rests are in proper relation to one another. If the occlusal plane is neglected, uncontrollable tilting of the mandible may occur. This may favor relapses. As Slavicek (1984) showed the mean inclination of the occlusal plane relative to the hinge axis-orbital plane to be 12.87 degrees (scatter 5.99 degrees) with dorsal convergence in 1,213 patients, 3 aluminium wedges with different inclinations were designed. These are suited for 92.5% of all cases with tolerances of +/- 3 degrees. Mandibular casts are pasted to geometric paper and shifted along the aluminium wedge to the desired position; the distance they are shifted is read from the paper. This distance is transferred to the teleradiograph and the changes in profile are checked. Preoperatively, prostheses can then be tailored to match the desired alveolar crest relation. During surgery, these prostheses serve as splints for setting the mandible as designed in the model. The osteotomy fragments are then screwed together transbuccally with miniscrews and clawed washers. The latter provide for a firm seat of the traction screws in the mandible at a safe distance from the mandibular canal. Postoperative intermaxillary fixation can thus be avoided. PMID:2700405

  20. Oesophageal perforation caused by screw displacement 16 months following anterior cervical spine fixation.

    PubMed

    Leaver, Nicholas; Colby, Alexandra; Appleton, Nathan; Vimalachandran, Dale

    2015-01-01

    Anterior cervical spine plating is a standard procedure for fixing unstable vertebral fractures. Following surgery, oesophageal perforation has an incidence of 0.25% and this is usually hours following surgery, due to over prominent screws or friction between the oesophagus and the plate. Instrumentation failure of these plates months or years following surgery is very rare but potentially life-threatening. We report a case of microcytic anaemia which was investigated by oesophagogastroduodenoscopy, and subsequently found that a screw from the anterior plate had lifted off and perforated the oesophagus. This is very rare, but emphasises an important lesson. Anyone presenting with gastrointestinal bleeding or infectious signs, with a history of cervical spine plating should be investigated immediately for instrumentation failure as it brings a high mortality. PMID:25796082

  1. Late foreign-body reaction to PLLA screws used for fixation of acetabular osteotomy

    Microsoft Academic Search

    D. Seino; S. Fukunishi; S. Yoshiya

    2007-01-01

    A 31-year-old woman underwent rotational acetabular osteotomy for acetabular dysplasia. At surgery, the acetabular fragment\\u000a and the grafted bone were fixed with PLLA screws. One year 7 months after surgery, the patient returned to our clinic with\\u000a acute swelling and pain with sinus formation. Based on the diagnosis of an infection, local debridement was performed. Histological\\u000a examination of the debrided

  2. Early Weight Bearing of Calcaneal Fractures Treated by Intraoperative 3D-Fluoroscopy and Locked-Screw Plate Fixation

    PubMed Central

    Kienast, B; Gille, J; Queitsch, C; Kaiser, M.M; Thietje, R; Juergens, C; Schulz, A.P

    2009-01-01

    Operative therapy of intraarticular fractures of the calcaneus is an established surgical standard. The aim is an accurate reduction of the fracture with reconstruction of Boehler’s angle, length, axis and subtalar joint surface. Intraoperative 3D-fluoroscopy with the Siremobil Iso-C 3D® mobile C-arm system is a valuable assistant for accurate reconstruction of these anatomical structures. Remaining incongruities can be recognized and corrected intraoperatively. The achieved reduction can be fixed by the advantages of an internal fixator (locked-screw plate interface). In the period of October 2002 until April 2007 we operated 136 patients with intraarticular fractures of the calcaneus by means of anatomical reduction, and internal plate fixator under intraoperative control of 3D-fluoroscopy. All patients were supplied with an orthesis after the operation which allowed weight bearing of 10 kg for 12 weeks for the patients operated between October 2002 and October 2004 (Group A). Transient local osteoporosis was observed in all X-Rays at follow-up after an average of 8,6 months. Therefore we changed our postoperative treatment plan for the patients operated between November 2004 and April 2007 (Group B). Weight bearing started with 20 KG after 6 weeks, was increased to 40 KG after 8 weeks and full weight bearing was allowed after 10 weeks for these patients. In no case a secondary dislocation of the fracture was seen. No bone graft was used. At follow up the average American Foot and Ankle Society Score (AOFAS) were 81 for Group_A, compared to 84 for Group B, treated with earlier weight bearing. Autologous bone graft was not necessary even if weight bearing was started after a period of six weeks postoperatively. The combination of 3D-fluoroscopy with locked internal fixation showed promising results. If the rate of patients developing subtalar arthrosis will decrease by this management will have to be shown in long term follow up. PMID:19750017

  3. Bilateral atlas laminar hook combined with transarticular screw fixation for an unstable bursting atlantal fracture

    Microsoft Academic Search

    Xiang Guo; Bin Ni; Mingfei Wang; Jian Wang; Songkai Li; Fengjin Zhou

    2009-01-01

    Introduction  The unstable atlas burst fracture (“Jefferson fracture”) is a fracture of the anterior and posterior atlantal arch with rupture\\u000a of the transverse atlantal ligament and an incongruence of the atlanto-occipital and the atlanto-axial joint facets. The posterior\\u000a atlantoaxial fusion is frequently used to reconstruct the stability of atlantoaxial joint. Conventional posterior atlantoaxial\\u000a fixations are associated with high rates of pseudoarthrosis

  4. Four lateral mass screw fixation techniques in lower cervical spine following laminectomy: a finite element analysis study of stress distribution

    PubMed Central

    2014-01-01

    Background Lateral mass screw fixation (LSF) techniques have been widely used for reconstructing and stabilizing the cervical spine; however, complications may result depending on the choice of surgeon. There are only a few reports related to LSF applications, even though fracture fixation has become a severe complication. This study establishes the three-dimensional finite element model of the lower cervical spine, and compares the stress distribution of the four LSF techniques (Magerl, Roy-Camille, Anderson, and An), following laminectomy -- to explore the risks of rupture after fixation. Method CT scans were performed on a healthy adult female volunteer, and Digital imaging and communication in medicine (Dicom) data was obtained. Mimics 10.01, Geomagic Studio 12.0, Solidworks 2012, HyperMesh 10.1 and Abaqus 6.12 software programs were used to establish the intact model of the lower cervical spines (C3-C7), a postoperative model after laminectomy, and a reconstructive model after applying the LSF techniques. A compressive preload of 74 N combined with a pure moment of 1.8 Nm was applied to the intact and reconstructive model, simulating normal flexion, extension, lateral bending, and axial rotation. The stress distribution of the four LSF techniques was compared by analyzing the maximum von Mises stress. Result The three-dimensional finite element model of the intact C3-C7 vertebrae was successfully established. This model consists of 503,911 elements and 93,390 nodes. During flexion, extension, lateral bending, and axial rotation modes, the intact model’s angular intersegmental range of motion was in good agreement with the results reported from the literature. The postoperative model after the three-segment laminectomy and the reconstructive model after applying the four LSF techniques were established based on the validated intact model. The stress distribution for the Magerl and Roy-Camille groups were more dispersive, and the maximum von Mises stress levels were lower than the other two groups in various conditions. Conclusion The LSF techniques of Magerl and Roy-Camille are safer methods for stabilizing the lower cervical spine. Therefore, these methods potentially have a lower risk of fixation fracture. PMID:25106498

  5. Comparison between the rigidity of bicortical screws and a miniplate for fixation of a mandibular setback after a simulated bilateral sagittal split osteotomy

    Microsoft Academic Search

    Wichit Tharanon

    1998-01-01

    Purpose: This investigation compared the biomechanical stability of three bicortical screws with that of a single four-hole miniplate after 5-mm mandibular setback after a bilateral sagittal split osteotomy (BSSO) in cadaver mandibles.Materials and Methods: Thirty human cadaver hemimandibles underwent BSSO followed by two different rigid fixation techniques. All specimens had no third molar, bony pathology, or evidence of mandibular fracture,

  6. Evaluation of stress distribution in resorbable screw fixation system: three-dimensional finite element analysis of mandibular setback surgery with bilateral sagittal split ramus osteotomy.

    PubMed

    Choi, Jae-Pyong; Baek, Seung-Hak; Choi, Jin-Young

    2010-07-01

    The purpose of this study was to evaluate the stress distribution of resorbable screw (RS) and cortical/cancellous bone in the mandibular setback surgery with bilateral sagittal split ramus osteotomy (BSSRO) according to fixation geometry and number of RSs using three-dimensional finite element analysis. Three-dimensional virtual models of the mandible and bicortical RS (INION CPS System; diameter, 2.5 mm; length, 12 mm [Inion Ltd, Tampere, Finland]) were constructed by Mimics (Materialise, Ann Arbor, MI) using three-dimensional computed tomography DICOM data with 0.5-mm-thickness cut. After 8-mm setback BSSRO was performed, fixation between the proximal and distal segments of the mandible was done with bicortical RS. Fixation options were classified into 3RL (3 RSs with linear configuration at the retromolar area), 2R1A (2 RSs at the retromolar area and 1 RS at the mandibular angle area), 2R1B (2 RSs at the retromolar area and 1 RS at the mandibular body area), and 3R1A (3 RSs at the retromolar area and 1 RS at the mandibular angle area). After applying the occlusal load of 132 N on the lower first molar, stress distributions of the RSs and cortical/cancellous bone in each option were analyzed by ANSYS program (ANSYS Inc, Canonsburg, PA). Maximum stress concentration was found at the anterior RS fixation in the retromolar area in all options. Although 3R1A fixation showed more even distribution of stress concentration than other fixation options, 2R1A fixation was comparable with 3R1A fixation in view of yield stress in RSs. In terms of fixation geometry and number of RSs, both 2R1A and 3R1A fixation configurations might provide proper stress distribution in BSSRO. PMID:20613578

  7. Trans-iliac pin/bolt/screw internal fixation for sacroiliac luxation or separation in cats: six cases.

    PubMed

    Yap, Fui W; Dunn, Andrew L; Farrell, Michael; Calvo, Ignacio

    2014-04-01

    Trans-iliac pin, bolt or screw stabilisation was performed on six cats with sacroiliac (SI) luxation and separation. For the purpose of this study, SI luxation is defined as the separation of the iliac wing from the sacrum without fracture of the sacral or iliac wing; SI separation is defined as the separation of the iliac wing from the sacrum secondary to fracture of the sacrum and/or the iliac wing. Complications, surgical time and medium-to-long-term outcome were assessed by a retrospective review of the clinical records and owner questionnaires. Postoperative reduction of the SI joint was good-to-excellent in all cases and the outcome was considered good-excellent in all cats apart from one, where the trans-iliac bolt migrated dorsally from the iliac wing. This cat had bilateral SI luxations. Based on our results, trans-iliac fixation of SI luxation/separation is associated with good clinical outcome and should be considered as a treatment option in unilateral SI luxation in cats. Caution should be exercised in the use of trans-iliac pin/bolt as the sole method of stabilisation in bilateral SI luxations. PMID:24043721

  8. Biomechanical evaluation of a medial knee reconstruction with comparison of bioabsorbable interference screw constructs and optimization with a cortical button.

    PubMed

    Wijdicks, Coen A; Brand, Emily J; Nuckley, David J; Johansen, Steinar; LaPrade, Robert F; Engebretsen, Lars

    2010-11-01

    Current fixation techniques in medial knee reconstructions predominantly utilize interference screws alone for soft tissue graft fixation. The use of concurrent fixation techniques as part of a hybrid fixation technique has also been suggested to strengthen soft tissue fixation, although these hybrid fixation techniques have not been biomechanically validated. The purpose was to biomechanically evaluate two distal tibial superficial MCL graft fixation techniques that consisted of an interference screw alone and in combination with a cortical button. Furthermore, the aim was to compare interference screws of different constructs. Twenty-four porcine tibias (average bone mineral density of 1.3 ± 0.2 g/cm(2); range, 1.0-1.6 g/cm(2), measured by DEXA scan) were divided into 4 groups of six specimens each. Group Ia consisted of a 7 × 23-mm poly-L-lactide (PLLA) interference screw. Group Ib utilized a PLLA interference screw in combination with a cortical button. Group IIa consisted of a 7 × 23-mm composite 70% poly(L-lactide-co-D, L-lactide) and 30% biphasic calcium phosphate (BCP) interference screw. Group IIb also utilized a composite interference screw in combination with a cortical button. The specimens were biomechanically tested with cyclic (500 cycles, 50-250 N, 1 Hz) and load-to-failure (20 mm/min) parameters. During cyclic loading, a significant increase in stiffness was seen for the PLLA hybrid 29.6 (±6.9) N/mm fixation compared to the PLLA screw-only 21.2 (±3.8) N/mm group (P < 0.05). Failure loads were 407.8 (±77.9) N for the composite screw, 445 (±72.2) N for the PLLA screw-only, 473.9 (±69.6) N for the composite hybrid fixation, and 511.0 (±78.5) N for the PLLA hybrid fixation. The PLLA screw alone was found to provide adequate fixation for a superficial MCL reconstruction, and the use of a cortical suture button combined with the PLLA screw resulted in a stiffer fixation during cyclic loading. The current reconstruction superficial MCL graft fixation technique utilizing a PLLA interference screw alone serves as an adequate recreation of the native tibial superficial MCL strength. In addition, a hybrid fixation with a cortical button which lends additional cyclic stiffness to its fixation would be advisable for use in suboptimal fixation cases. PMID:20563561

  9. Pedicle Screw Configuration for Thoracolumbar Burst Fracture Treatment: Short versus Long Posterior Fixation Constructs with and without Anterior Column Augmentation

    PubMed Central

    Peters, Todd; Hussain, Mir; Khalil, Saif

    2014-01-01

    Study Design An in-vitro study. Purpose The current study is aimed at investigating the differences in stability between short posterior fixation (SPF), hybrid posterior fixation (HPF), and long posterior fixation (LPF) with and without anterior column augmentation using calcium phosphate bone cement (CaP) for treating burst fractures (BFs). Overview of Literature The ideal treatment for thoracolumbar BF is controversial regarding the use of short or LPF constructs. Methods Seven human thoracolumbar spines (T9-L4) were tested on a six degree of freedom spine simulator in three physiologic planes, flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Tested surgical constructs included the following: intact, injury (BF), SPF (T12-L2), HPF (T11-L2), LPF (T11-L3), SPF+CaP, HPF+CaP, LPF+CaP, and CaP alone (CaP). Range of motion (ROM) was recorded at T12-L2 in FE, LB, and AR. Results The reduction in mean ROM trended as follows: LPF>HPF>SPF. Only LPF constructs and HPF with anterior column augmentation significantly reduced mean ROM in FE and LB compared to the intact state. All instrumented constructs (SPF, HPF, and LPF) significantly reduced ROM in FE and LB compared to the injured condition. Furthermore, the instrumented constructs did not provide significant rotational stability. Injecting CaP provided minimal additional stability. Conclusions For the injury created, LPF and HPF provided better stability than SPF with and without anterior column augmentation. Therefore, highly unstable fractures may require extended, long or hybrid fusion constructs for optimum stability. PMID:24596603

  10. Pooled Analysis of Non-Union, Re-Operation, Infection, and Approach Related Complications after Anterior Odontoid Screw Fixation

    PubMed Central

    Tian, Nai-Feng; Hu, Xu-Qi; Wu, Li-Jun; Wu, Xin-Lei; Wu, Yao-Sen; Zhang, Xiao-Lei; Wang, Xiang-Yang; Chi, Yong-Long; Mao, Fang-Min

    2014-01-01

    Background Anterior odontoid screw fixation (AOSF) has been one of the most popular treatments for odontoid fractures. However, the true efficacy of AOSF remains unclear. In this study, we aimed to provide the pooled rates of non-union, reoperation, infection, and approach related complications after AOSF for odontoid fractures. Methods We searched studies that discussed complications after AOSF for type II or type III odontoid fractures. A proportion meta-analysis was done and potential sources of heterogeneity were explored by meta-regression analysis. Results Of 972 references initially identified, 63 were eligible for inclusion. 54 studies provided data regarding non-union. The pooled non-union rate was 10% (95% CI: 7%–3%). 48 citations provided re-operation information with a pooled proportion of 5% (95% CI: 3%–7%). Infection was described in 20 studies with an overall rate of 0.2% (95% CI: 0%–1.2%). The main approach related complication is postoperative dysphagia with a pooled rate of 10% (95% CI: 4%–17%). Proportions for the other approach related complications such as postoperative hoarseness (1.2%, 95% CI: 0%–3.7%), esophageal/retropharyngeal injury (0%, 95% CI: 0%–1.1%), wound hematomas (0.2%, 95% CI: 0%–1.8%), and spinal cord injury (0%, 95% CI: 0%–0.2%) were very low. Significant heterogeneities were detected when we combined the rates of non-union, re-operation, and dysphagia. Multivariate meta-regression analysis showed that old age was significantly predictive of non-union. Subgroup comparisons showed significant higher non-union rates in age ?70 than that in age ?40 and in age 40 to <50. Meta-regression analysis did not reveal any examined variables influencing the re-operation rate. Meta-regression analysis showed age had a significant effect on the dysphagia rate. Conclusions/Significances This study summarized the rates of non-union, reoperation, infection, and approach related complications after AOSF for odontoid factures. Elderly patients were more likely to experience non-union and dysphagia. PMID:25058011

  11. Unilateral C1 Lateral Mass and C2 Pedicle Screw Fixation for Atlantoaxial Instability in Rheumatoid Arthritis Patients: Comparison with the Bilateral Method

    PubMed Central

    Paik, Seung-Chull; Bak, Koang Hum; Ryu, Jeil; Choi, Kyu-Sun

    2015-01-01

    Objective Bilateral C1 lateral mass and C2 pedicle screw fixation (C1LM-C2P) is an ideal technique for correcting atlantoaxial instability (AAI). However, the inevitable situation of vertebral artery injury or unfavorable bone structure may necessitate the use of unilateral C1LM-C2P. This study compares the fusion rates of the C1 lateral mass and C2 pedicle screw in the unilateral and bilateral methods. Methods Over five years, C1LM-C2P was performed in 25 patients with AAI in our institute. Preoperative studies including cervical X-ray, three-dimensional computed tomography (CT), CT angiogram, and magnetic resonance imaging were performed. To evaluate bony fusion, measurements of the atlanto-dental interval (ADI) and CT scans were performed in the preoperative period, immediate postoperative period, and postoperatively at 1, 3, 6, and 12 months. Results Unilateral C1LM-C2P was performed in 11 patients (44%). The need to perform unilateral C1LM-C2P was due to anomalous course of the vertebral artery in eight patients (73%) and severe degenerative arthritis in three patients (27%). The mean ADI in the bilateral group was 2.09 mm in the immediate postoperative period and 1.75 mm in 12-months postoperatively. The mean ADI in the unilateral group was 1.82 mm in the immediate postoperative period and 1.91 mm in 12-months postoperatively. Comparison of ADI measurements showed no significant differences in either group (p=0.893), and the fusion rate was 100% in both groups. Conclusion Although bilateral C1LM-C2P is effective for AAI from a biomechanical perspective, unilateral screw fixation is a useful alternative in patients with anatomical variations. PMID:26180616

  12. The Warwick Hip Trauma Evaluation One -an abridged protocol for the WHiTE One Study: An embedded randomised trial comparing the X-bolt with slidinghip screw fixation in extracapsular hip fractures.

    PubMed

    Griffin, X L; McArthur, J; Achten, J; Parsons, N; Costa, M L

    2013-01-01

    Fractures of the proximal femur are one of the greatest challenges facing the medical community, constituting a heavy socioeconomic burden worldwide. Controversy exists regarding the optimal treatment for patients with unstable trochanteric proximal femoral fractures. The recognised treatment alternatives are extramedullary fixation usually with a sliding hip screw and intramedullary fixation with a cephalomedullary nail. Current evidence suggests that best results and lowest complication rates occur using a sliding hip screw. Complications in these difficult fractures are relatively common regardless of type of treatment. We believe that a novel device, the X-Bolt dynamic plating system, may offer superior fixation over a sliding hip screw with lower reoperation risk and better function. We therefore propose to investigate the clinical effectiveness of the X-bolt dynamic plating system compared with standard sliding hip screw fixation within the framework of a the larger WHiTE (Warwick Hip Trauma Evaluation) Comprehensive Cohort Study. Cite this article: Bone Joint Res 2013;2:206-9. PMID:24089290

  13. The use of a virtual three-dimensional model to evaluate the intraosseous space available for percutaneous screw fixation of acetabular fractures.

    PubMed

    Attias, N; Lindsey, R W; Starr, A J; Borer, D; Bridges, K; Hipp, J A

    2005-11-01

    We created virtual three-dimensional reconstruction models from computed tomography scans obtained from patients with acetabular fractures. Virtual cylindrical implants were placed intraosseously in the anterior column, the posterior column and across the dome of the acetabulum. The maximum diameter which was entirely contained within the bone was determined for each position of the screw. In the same model, the cross-sectional diameters of the columns were measured and compared to the maximum diameter of the corresponding virtual implant. We found that the mean maximum diameter of virtual implant accommodated by the anterior columns was 6.4 mm and that the smallest diameter of the columns was larger than the maximum diameter of the equivalent virtual implant. This study suggests that the size of the screw used for percutaneous fixation of acetabular fractures should not be based solely on the measurement of cross-sectional diameter and that virtual three-dimensional reconstructions might be useful in pre-operative planning. PMID:16260671

  14. Internal Reduction Established by Occiput-C2 Pedicle Polyaxial Screw Stabilization in Pediatric Atlantoaxial Rotatory Fixation

    Microsoft Academic Search

    Deniz Belen; Serkan Simsek; Kazim Yigitkanli; Murad Bavbek

    2006-01-01

    Atlantoaxial rotatory fixation is an uncommon disorder of childhood, which can be treated conservatively whendiagnosed early. Although spontaneous correction occasionally occurs, most of the patients usually benefit from collar or traction therapies. If there is no intervention or if all external therapeutic modalities fail, the deformity may become chronic and irreducible. In such rare cases, surgical correction and stabilization are

  15. Comparison of healing process in open osteotomy model and open fracture model: Delayed healing of osteotomies after intramedullary screw fixation.

    PubMed

    Klein, Moritz; Stieger, Andrea; Stenger, David; Scheuer, Claudia; Holstein, Jörg H; Pohlemann, Tim; Menger, Michael D; Histing, Tina

    2015-07-01

    Murine osteotomy and fracture models have become the standard to study molecular mechanisms of bone healing. Because there is little information whether the healing of osteotomies differs from that of fractures, we herein studied in mice the healing of femur osteotomies compared to femur fractures. Twenty CD-1 mice underwent a standardized open femur osteotomy. Another 20 mice received a standardized open femur fracture. Stabilization was performed by an intramedullary screw. Bone healing was studied by micro-CT, biomechanical, histomorphometric and protein expression analyses. Osteotomies revealed a significantly lower biomechanical stiffness compared to fractures. Micro-CT showed a reduced bone/tissue volume within the callus of the osteotomies. Histomorphometric analyses demonstrated also a significantly lower amount of osseous tissue in the callus of osteotomies (26% and 88% after 2 and 5 weeks) compared to fractures (50% and 100%). This was associated with a delayed remodeling. Western blot analyses demonstrated comparable BMP-2 and BMP-4 expression, but higher levels of collagen-2, CYR61 and VEGF after osteotomy. Therefore, we conclude that open femur osteotomies in mice show a markedly delayed healing when stabilized less rigidly with an intramedullary screw. This should be considered when choosing a model for studying the mechanisms of bone healing in mice. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:971-978, 2015. PMID:25732349

  16. One-stage partial vertebrectomy, titanium mesh implantation and pedicle screw fixation in the treatment of thoracolumbar burst fractures through a posterior approach

    PubMed Central

    Liu, Yueju; Li, Guangbin; Dong, Tianhua; Zhang, Yingze; Li, Heng

    2014-01-01

    OBJECTIVE: To analyze the clinical results of a partial vertebrectomy with titanium mesh implantation and pedicle screw fixation using a posterior approach to reconstruct the spine in the treatment of thoracolumbar burst fractures. METHOD: From January 2006 to August 2008, 20 patients with severe thoracolumbar fractures were treated.For vertebral bodies associated with one injured intervertebral disk, subtotal vertebrectomy surgery and single-segment fusion were performed. For vertebral bodies with two injured adjacent intervertebral disks, partial vertebrectomy surgery and two-segment fusion were performed. RESULTS: All 20 patients were followed up for 12 to 24 months (average of 18 months). There were no complications such as wound infections, hemopneumothorax or abdominal infections in any of the patients. The neurological status of all of the patients was improved by at least one American Spinal Injury Association grade by the last follow-up. The anterior vertebral body height was an average of 50.77% before surgery, 88.51% after surgery and 87.86% at the last follow up; the sagittal Cobb angle was improved, on average, from 26.15° to 5.39° and was 5.90° at the last follow up. The percentage of spinal stenosis was improved, on average, from 26.07% to 4.93%° and was 6.15% at the last follow up. There were significant differences in the anterior vertebral body height pre- and post-surgery and in the sagittal Cobb angle and the percentage of spinal stenosis (p<0) in all patients. CONCLUSIONS: This surgical procedure is simple and can accomplish decompression, reduction, fixation and fusion of the spine in one stage. This approach could be widely used in orthopedics. PMID:25627991

  17. Fixation using alternative implants for the treatment of hip fractures (FAITH): design and rationale for a multi-centre randomized trial comparing sliding hip screws and cancellous screws on revision surgery rates and quality of life in the treatment of femoral neck fractures

    PubMed Central

    2014-01-01

    Background Hip fractures are a common type of fragility fracture that afflict 293,000 Americans (over 5,000 per week) and 35,000 Canadians (over 670 per week) annually. Despite the large population impact the optimal fixation technique for low energy femoral neck fractures remains controversial. The primary objective of the FAITH study is to assess the impact of cancellous screw fixation versus sliding hip screws on rates of revision surgery at 24 months in individuals with femoral neck fractures. The secondary objective is to determine the impact on health-related quality of life, functional outcomes, health state utilities, fracture healing, mortality and fracture-related adverse events. Methods/Design FAITH is a multi-centre, multi-national randomized controlled trial utilizing minimization to determine patient allocation. Surgeons in North America, Europe, Australia, and Asia will recruit a total of at least 1,000 patients with low-energy femoral neck fractures. Using central randomization, patients will be allocated to receive surgical treatment with cancellous screws or a sliding hip screw. Patient outcomes will be assessed at one week (baseline), 10 weeks, 6, 12, 18, and 24 months post initial fixation. We will independently adjudicate revision surgery and complications within 24 months of the initial fixation. Outcome analysis will be performed using a Cox proportional hazards model and likelihood ratio test. Discussion This study represents major international efforts to definitively resolve the treatment of low-energy femoral neck fractures. This trial will not only change current Orthopaedic practice, but will also set a benchmark for the conduct of future Orthopaedic trials. Trial registration The FAITH trial is registered at ClinicalTrials.gov (Identifier NCT00761813). PMID:24965132

  18. Resorbable screws versus pins for optimal transplant fixation (SPOT) in anterior cruciate ligament replacement with autologous hamstring grafts: rationale and design of a randomized, controlled, patient and investigator blinded trial [ISRCTN17384369

    PubMed Central

    Stengel, Dirk; Matthes, Gerrit; Seifert, Julia; Tober, Volker; Mutze, Sven; Rademacher, Grit; Ekkernkamp, Axel; Bauwens, Kai; Wich, Michael; Casper, Dirk

    2005-01-01

    Background Ruptures of the anterior cruciate ligament (ACL) are common injuries to the knee joint. Arthroscopic ACL replacement by autologous tendon grafts has established itself as a standard of care. Data from both experimental and observational studies suggest that surgical reconstruction does not fully restore knee stability. Persisting anterior laxity may lead to recurrent episodes of giving-way and cartilage damage. This might at least in part depend on the method of graft fixation in the bony tunnels. Whereas resorbable screws are easy to handle, pins may better preserve graft tension. The objective of this study is to determine whether pinning of ACL grafts reduces residual anterior laxity six months after surgery as compared to screw fixation. Design/ Methods SPOT is a randomised, controlled, patient and investigator blinded trial conducted at a single academic institution. Eligible patients are scheduled to arthroscopic ACL repair with triple-stranded hamstring grafts, conducted by a single, experienced surgeon. Intraoperatively, subjects willing to engage in this study will be randomised to transplant tethering with either resorbable screws or resorbable pins. No other changes apply to locally established treatment protocols. Patients and clinical investigators will remain blinded to the assigned fixation method until the six-month follow-up examination. The primary outcome is the side-to-side (repaired to healthy knee) difference in anterior translation as measured by the KT-1000 arthrometer at a defined load (89 N) six months after surgery. A sample size of 54 patients will yield a power of 80% to detect a difference of 1.0 mm ± standard deviation 1.2 mm at a two-sided alpha of 5% with a t-test for independent samples. Secondary outcomes (generic and disease-specific measures of quality of life, magnetic resonance imaging morphology of transplants and devices) will be handled in an exploratory fashion. Conclusion SPOT aims at showing a reduction in anterior knee laxity after fixing ACL grafts by pins compared to screws. PMID:15723704

  19. EFFECT OF NITROGEN AND METAL ADDITIONS ON NITROGEN FIXATION ACTIVITY IN BIOLOGICAL SOIL CRUSTS

    NASA Astrophysics Data System (ADS)

    Alexander, K.; Lui, D.; Anbar, A. D.; Garcia-Pichel, F.; Hartnett, H. E.

    2009-12-01

    Biological soil crusts (BSCs) are diverse consortia of microorganisms that live in intimate association with soils in arid environments. Also called cryptogamic or microbiotic crusts, these communities can include cyanobacteria, algae, heterotrophic bacteria, fungi, lichens, and mosses. Together, these organisms provide many services to their surrounding ecosystems, including reduction of water runoff, promotion of water infiltration, and prevention of soil erosion. The cyanobacteria and algae also provide fixed carbon (C) to the soil through photosynthesis, and because atmospheric deposition of nitrogen (N) in arid environments is low, the major input of biologically available N comes from cyanobacteria capable of converting nitrogen gas (N2) to ammonium (NH4+). Biological soil crusts are easily destroyed by livestock grazing, motor vehicle travel, and many forms of recreational and agricultural land use. Loss of BSC cover can leave the soil vulnerable to intense erosion that can remove the nutrients necessary to sustain plant and animal life, thus accelerating the process of desertification. In order to preserve existing crusts and encourage the development of new crusts, it is crucial to understand the nutrient requirements of metabolism and growth in these microbial communities. This study investigated the affect of nitrogen and metal additions on N2-fixation activity in cyanobacterially-dominated crusts from the Colorado Plateau near Moab, Utah. Although N2-fixation has been studied in this system before, the affect of nutrient additions on N2-fixation activity has not been documented. The goal of this work was to understand how N and metal supplementation affects crust N metabolism. Three experiments were conducted to observe how N2-fixation activity changed with the addition of N, molybdenum (Mo), and vanadium (V). Molybdenum and vanadium were chosen because they are most commonly found at the active site of the enzyme nitrogenase, the molecule responsible for the biological conversion of N2 to NH4+. The Mo-dependent version of the enzyme is the most efficient, and it is used by the majority of N2-fixing organisms. Elements were added as aqueous solutions of NH4NO3, Na2MoO4, and Na3VO4 respectively. Nitrogen fixation potential was assayed using a modified acetylene reduction technique. Results from the N-addition experiment show that when N is provided, BSC organisms stop N2-fixation activity. This confirms that under natural conditions, the community is limited with respect to N. In general, crusts under Mo-addition fix at higher rates than crusts with no added Mo. This implies that crusts may also be limited with respect to Mo. However, contrary to our expectations, crusts fix at lower rates when V is added as compared to a no-V control. It is possible that this is the result of V-toxicity, or that V competes with the uptake and utilization of available Mo, thus exacerbating Mo-limitation. Experiments are currently underway to investigate how the geochemistry of the soil porewater changes as a result of these nutrient additions.

  20. Retrieval of broken iliosacral screws: The power of a push screw.

    PubMed

    El Dafrawy, Mostafa H; Osgood, Greg M

    2015-07-01

    Percutaneous iliosacral screw fixation is a common technique that is widely used for unstable posterior pelvic ring disruptions. Complications of posterior percutaneous iliosacral screw fixation include implant malpositioning and hardware failure. Removal of iliosacral screws in broken or symptomatic hardware is sometimes necessary. To our knowledge, there are few reports addressing pelvic implant removal, and most of those report on anterior pelvic implants and symphyseal plates. There are no reports describing techniques for retrieval of broken iliosacral screws. We present two cases involving removal of broken sacroiliac screws, review the literature regarding iliosacral implant extraction, and identify important aspects of safe extraction of iliosacral screws and the potential complications associated with their retrieval. We further describe a novel and powerful technique to facilitate percutaneous removal of broken screw fragments, using a "push screw" to drive a broken screw fragment from a position buried in bone. PMID:25986663

  1. Direct repair of defects in lumbar spondylolysis with a new pedicle screw hook fixation: clinical, functional and Ct-assessed study

    PubMed Central

    Troussel, Serge

    2007-01-01

    Spondylolysis is a common entity, a minority of people affected by this disease need medical care, and only a few require surgery. Reconstruction of the pars interarticularis is an interesting alternative to segmental fusion; this technique has the advantage of preserving segmental motion. Most authors report good results for young patients without intervertebral disk or facet degenerative changes. Moreover Louis also showed good to excellent results with his technique carried out among people who presented a satisfactory disk height (equal to two thirds of normal height). This could extend the number of patients for whom pars interarticularis repair could be proposed. In this study, the limit of reconstruction was set at grade 3of the Pfirrmann’s classification. The fixation of the isthmus was done with a new kind of pedicle screw hook system. This stable and strong device is easy to use, allows an anatomic pars interarticularis reconstruction of spondylolysis and avoids a postoperative bracing. Twenty-three patients were assessed in this study, the mean age at operation was 34 (range 16–52 years) and the average follow-up was for 59 months (range 6–113 months). Eight patients showed moderate degenerative disk disease before the surgery and 12 patients had a grade 1 spondylolisthesis. The visual analogical scale, the Oswestry disability index (ODI) and the modified Prolo score were used for assessment of pain and clinical outcome before and after surgery. The results were from “excellent” to “good” for twenty patients (87%) and “fair” for three of them (13%). The consolidation of the isthmus was assessed at the end of the study (CT-scan); the fusion rate was observed in 91%. Among patients aged less than 30 years results are from “good”, to “excellent” in all cases and consolidation was always observed. All of them showed normal disc signal before the surgery. In the group aged more than 30 years, the results varied from “good” to “excellent’ in 73% and fusion of the defect was discovered in 82% of cases. Eight of them (73%) had moderate disk signal modification before the surgery. All people with fair results displayed moderate disk degeneration signs at MRI before surgery; but two of those three patients had a failure of defect consolidation too and it is also associated with poor results by several authors. No complication was found in this series. According to the good results reported by Louis and upto the current finding, the authors believe that pars interarticularis repair can be carried out on patients with moderate degenerative disk disease; the stage 3 of Pfirrmann’s classification seems a good limit. The Bone and joint research (B.J.R. system) is readily usable by any surgeon using pedicle screw systems and having a short learning curve. No device failure has been observed in this series. PMID:17520298

  2. Direct repair of defects in lumbar spondylolysis with a new pedicle screw hook fixation: clinical, functional and Ct-assessed study.

    PubMed

    Debusscher, Felix; Troussel, Serge

    2007-10-01

    Spondylolysis is a common entity, a minority of people affected by this disease need medical care, and only a few require surgery. Reconstruction of the pars interarticularis is an interesting alternative to segmental fusion; this technique has the advantage of preserving segmental motion. Most authors report good results for young patients without intervertebral disk or facet degenerative changes. Moreover Louis also showed good to excellent results with his technique carried out among people who presented a satisfactory disk height (equal to two thirds of normal height). This could extend the number of patients for whom pars interarticularis repair could be proposed. In this study, the limit of reconstruction was set at grade 3 of the Pfirrmann's classification. The fixation of the isthmus was done with a new kind of pedicle screw hook system. This stable and strong device is easy to use, allows an anatomic pars interarticularis reconstruction of spondylolysis and avoids a postoperative bracing. Twenty-three patients were assessed in this study, the mean age at operation was 34 (range 16-52 years) and the average follow-up was for 59 months (range 6-113 months). Eight patients showed moderate degenerative disk disease before the surgery and 12 patients had a grade 1 spondylolisthesis. The visual analogical scale, the Oswestry disability index (ODI) and the modified Prolo score were used for assessment of pain and clinical outcome before and after surgery. The results were from "excellent" to "good" for twenty patients (87%) and "fair" for three of them (13%). The consolidation of the isthmus was assessed at the end of the study (CT-scan); the fusion rate was observed in 91%. Among patients aged less than 30 years results are from "good", to "excellent" in all cases and consolidation was always observed. All of them showed normal disc signal before the surgery. In the group aged more than 30 years, the results varied from "good" to "excellent' in 73% and fusion of the defect was discovered in 82% of cases. Eight of them (73%) had moderate disk signal modification before the surgery. All people with fair results displayed moderate disk degeneration signs at MRI before surgery; but two of those three patients had a failure of defect consolidation too and it is also associated with poor results by several authors. No complication was found in this series. According to the good results reported by Louis and upto the current finding, the authors believe that pars interarticularis repair can be carried out on patients with moderate degenerative disk disease; the stage 3 of Pfirrmann's classification seems a good limit. The Bone and joint research (B.J.R. system) is readily usable by any surgeon using pedicle screw systems and having a short learning curve. No device failure has been observed in this series. PMID:17520298

  3. Scarf osteotomy without screw fixation

    Microsoft Academic Search

    M. Maestro

    2007-01-01

    The scarf osteotomy is now well recognised as reliable and effective to contribute to the correction of the majority of hallux\\u000a valgus. The challenge remains for the correction of severe deformities with metatarsus varus angle >18? and Distal Metatarsal\\u000a Articular Angle (DMAA) >15?. In order to significantly improve in 3D the metatarsal head displacements, our scarf design became more oblique,

  4. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8?N compared to the failure load for calf vertebrae's 1264?N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890?N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective. PMID:25991716

  5. Early clinical results with cortically based pedicle screw trajectory for fusion of the degenerative lumbar spine.

    PubMed

    Andrew Glennie, R; Dea, Nicolas; Kwon, Brian K; Street, John T

    2015-06-01

    This study reviews the outcomes and revision rates of degenerative lumbar fusion surgery using cortical trajectory pedicle screws in lieu of traditional pedicle screw instrumentation. Pedicle screw fixation can be a challenge in patients with low bone mineral density. Wide posterior approaches to the lumbar spine exposing lateral to the facet joints and onto transverse processes causes an additional degree of muscular damage and blood loss not present with a simple laminectomy. A cortical bone trajectory pedicle screw has been proposed as an alternative to prevent screw pullout and decrease the morbidity associated with the wide posterior approach to the spine. We present a series of eight consecutive patients using a cortical bone trajectory instead of traditional pedicle screw fixation for degenerative conditions of the lumbar spine. A retrospective review of our institutional registry data identified eight patients who had cortical screws placed with the assistance of O-arm Stealth navigation (Medtronic Sofamor Danek, Memphis, TN, USA) from 2010-2013. We analyzed the need for revision, the maintenance of reduction and the incidence of screw pullout or breakage. Our review demonstrated that two of eight patients were revised at an average of 12months. The reasons for these revisions were pseudarthrosis and caudal adjacent segment failure. All patients who were revised had frank screw loosening. We present early clinical results of a new technique that has been shown to have a better fixation profile in laboratory testing. Our less than favorable early clinical results should be interpreted with caution and highlight important technical issues which should be considered. PMID:25769253

  6. Pedicle Instrumentation Failure in Thoracolumbar Fixation

    Microsoft Academic Search

    Mohamed Lotfy; Nasser M. Sayed Ahmed; Alaa A. Farag; Walid Raafat; Walid A. Badawy; Hossam Ibrahim; Islam Abou El Fotouh; Ahmed Saleh

    2007-01-01

    Objective: The authors reviewed factors related to the surgical techniques resulting in failure of the construct of the internal fixation of thoracolumbar fractures through transpedicular screw systems and how to be avoided. Patients and Methods: The authors reviewed 280 consecutive patients with traumatic thoracolumbar fractures who underwent spinal surgical fixation with short segment transpedicular screw instrumentation at three institutions, between

  7. Clinical Comparison of Fixation Methods for Patellar Bone Quadriceps Tendon Autografts in Anterior Cruciate Ligament ReconstructionAbsorbable Cross-pins Versus Absorbable Screws

    Microsoft Academic Search

    Ottmar Gorschewsky; Robert Stapf; Laurent Geiser; Ulrich Geitner; Wolfram Neumann

    2007-01-01

    Background: Recently, the use of the quadriceps tendon transplant with bone block (patellar bone quadriceps tendon autografts) for anterior cruciate ligament reconstruction has increasingly been reported.Hypothesis: Clinical results after the implantation of a patellar bone quadriceps tendon autograft fixed with cross-pins or screws will show no significant difference between the 2 techniques with regard to stability, function, and subjective satisfaction.

  8. An Innovative Universal Screw Removal Instrument

    PubMed Central

    Elmada?, Mehmet; Uzer, Gökçer; Acar, Mehmet Ali

    2015-01-01

    Objective To present the clinical benefits of an instrument designed to facilitate removal of polyaxial screws during revision surgery. Methods All polyaxial screws can be removed without additional materials or a large amount of debridement using our newly designed instrument. Forty-two screws were removed from five patients without any complications using this instrument. Results We removed the cap screws and rods from the 42 polyaxial screws in five patients and made them monoaxial using the new screw removal apparatus. The screws and rods were removed quickly in a minimally invasive way with no complications. No damage to the pedicle or surrounding soft tissue occurred during screw removal. No neurogenic changes developed during revision surgery after changing the screws. Conclusion This newly designed screw removal instrument was used safely and effectively to remove all polyaxial and monoaxial pedicle screws. PMID:25883660

  9. A Case of Pedicle Screw Loosening Treated by Modified Transpedicular Screw Augmentation with Polymethylmethacrylate

    PubMed Central

    Kang, Suk-Hyung; Kim, Kyoung-Tae; Park, Seung Won

    2011-01-01

    We report a case of pedicle screw loosening treated by modified transpedicular screw augmentation technique using polymethylmethacrylate (PMMA), which used the anchoring effect of hardened PMMA. A 56-year-old man who had an L3/4/5 fusion operation 3 years ago complained of continuous low back pain after this operation. The computerized tomography showed a radiolucent halo around the pedicle screw at L5. We augmented the L5 pedicle screw with modified pedicle screw augmentation technique using PMMA and performed an L3/4/5 pedicle screw fixation without hook or operation field extension. This modified technique is a kind of transpedicular stiffness augmentation using PMMA for the dead space around the loosed screw. After filling the dead space with 1-2 cc of PMMA, we inserted a small screw. Once the PMMA hardened, we removed the small screw and inserted a thicker screw along the existing screw threading to improve the pedicle screws' pullout strength. At 10 months' follow-up, x-ray showed strong fusion of L3/4/5. The visual analogue scale (VAS) of his back pain was improved from 9 to 5. This modified transpedicular screw augmentation with PMMA using anchoring effect is a simple and effective surgical technique for pedicle screw loosening. However, clinical analyses of long-term follow-up and biomechanical studies are needed. PMID:21494370

  10. Medial malleolar fractures: a biomechanical study of fixation techniques.

    PubMed

    Fowler, T Ty; Pugh, Kevin J; Litsky, Alan S; Taylor, Benjamin C; French, Bruce G

    2011-08-01

    Fracture fixation of the medial malleolus in rotationally unstable ankle fractures typically results in healing with current fixation methods. However, when failure occurs, pullout of the screws from tension, compression, and rotational forces is predictable. We sought to biomechanically test a relatively new technique of bicortical screw fixation for medial malleoli fractures. Also, the AO group recommends tension-band fixation of small avulsion type fractures of the medial malleolus that are unacceptable for screw fixation. A well-documented complication of this technique is prominent symptomatic implants and secondary surgery for implant removal. Replacing stainless steel 18-gauge wire with FiberWire suture could theoretically decrease symptomatic implants. Therefore, a second goal was to biomechanically compare these 2 tension-band constructs. Using a tibial Sawbones model, 2 bicortical screws were compared with 2 unicortical cancellous screws on a servohydraulic test frame in offset axial, transverse, and tension loading. Second, tension-band fixation using stainless steel wire was compared with FiberWire under tensile loads. Bicortical screw fixation was statistically the stiffest construct under tension loading conditions compared to unicortical screw fixation and tension-band techniques with FiberWire or stainless steel wire. In fact, unicortical screw fixation had only 10% of the stiffness as demonstrated in the bicortical technique. In a direct comparison, tension-band fixation using stainless steel wire was statistically stiffer than the FiberWire construct. PMID:21815575

  11. Morphometric evaluation of subaxial cervical spine using multi-detector computerized tomography (MD-CT) scan: the consideration for cervical pedicle screws fixation

    PubMed Central

    2014-01-01

    Background Cervical pedicle screw (CPS) insertion is a technically demanding procedure. The quantitative understanding of cervical pedicle morphology, especially the narrowest part of cervical pedicle or isthmus, would minimize the risk of catastrophic damage to surrounding neurovascular structures and improve surgical outcome. The aim of this study was to investigate morphology and quantify cortical thickness of the cervical isthmus by using Multi-detector Computerized Tomography (MD-CT) scan. Methods The cervical CT scans were performed in 74 patients (37 males and 37 females) with 1-mm slice thickness and then retro-reconstructed into sagittal and coronal planes to measure various cervical parameters as follows: outer pedicle width (OPW), inner pedicle width (IPW), outer pedicle height (OPH), inner pedicle height (IPH), pedicle cortical thickness, pedicle sagittal angle (PSA), and pedicle transverse angle (PTA). Results Total numbers of 740 pedicles were measured in this present study. The mean OPW and IPW significantly increased from C3 to C7 while the mean OPH and IPH of those showed non-significant difference between any measured levels. The medial-lateral cortical thickness was significantly smaller than the superior-inferior one. PTA in the upper cervical spine was significantly wider than the lower ones. The PSA changed from upward inclination at upper cervical spine to the downward inclination at lower cervical spine. Conclusions This study has demonstrated that cervical vertebra has relatively small and narrow inner pedicle canal with thick outer pedicle cortex and also shows a variable in pedicle width and inconsistent transverse angle. To enhance the safety of CPS insertion, the entry point and trajectories should be determined individually by using preoperative MD-CT scan and the inner pedicle width should be a key parameter to determine the screw dimensions. PMID:24725394

  12. A new adhesive technique for internal fixation in midfacial surgery

    Microsoft Academic Search

    Kira Endres; Rudolf Marx; Joachim Tinschert; Dieter Christian Wirtz; Christian Stoll; Dieter Riediger; Ralf Smeets

    2008-01-01

    BACKGROUND: The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could

  13. Assessment of different screw augmentation techniques and screw designs in osteoporotic spines

    PubMed Central

    Chavanne, A.; Spitaler, R.; Kropik, K.; Aigner, N.; Ogon, M.; Redl, H.

    2008-01-01

    This is an experimental study on human cadaver spines. The objective of this study is to compare the pullout forces between three screw augmentation methods and two different screw designs. Surgical interventions of patients with osteoporosis increase following the epidemiological development. Biomechanically the pedicle provides the strongest screw fixation in healthy bone, whereas in osteoporosis all areas of the vertebra are affected by the disease. This explains the high screw failure rates in those patients. Therefore PMMA augmentation of screws is often mandatory. This study involved investigation of the pullout forces of augmented transpedicular screws in five human lumbar spines (L1–L4). Each spine was treated with four different methods: non-augmented unperforated (solid) screw, perforated screw with vertebroplasty augmentation, solid screw with vertebroplasty augmentation and solid screw with balloon kyphoplasty augmentation. Screws were augmented with Polymethylmethacrylate (PMMA). The pullout forces were measured for each treatment with an Instron testing device. The bone mineral density was measured for each vertebra with Micro-CT. The statistical analysis was performed with a two-sided independent student t test. Forty screws (10 per group and level) were inserted. The vertebroplasty-augmented screws showed a significant higher pullout force (mean 918.5 N, P = 0.001) than control (mean 51 N), the balloon kyphoplasty group did not improve the pullout force significantly (mean 781 N, P > 0.05). However, leakage occurred in some cases treated with perforated screws. All spines showed osteoporosis on Micro-CT. Vertebroplasty-augmented screws, augmentation of perforated screws and balloon kyphoplasty augmented screws show higher pullout resistance than non-augmented screws. Significant higher pullout forces were only reached in the vertebroplasty augmented vertebra. The perforated screw design led to epidural leakage due to the position of the perforation in the screw. The position of the most proximal perforation is critical, depending on screw design and proper insertion depth. Nevertheless, using a properly designed perforated screw will facilitate augmentation and instrumentation in osteoporotic spines. PMID:18781342

  14. Acute changes in the pacing threshold after lead implantation. Comparison between retractable and sweet-tip active-fixation leads.

    PubMed

    Kashiwase, Kazunori; Kobayashi, Hiroshi; Hirata, Akio; Wada, Mitsuru; Nakanishi, Hiroyuki; Ueda, Yasunori

    2012-01-01

    Although the pacing threshold of steroid-eluting active-fixation leads remains stable over the long term, it changes rapidly after screw-in. We compared the pacing threshold in the acute phase between retractable and Sweet-Tip active-fixation leads. We studied 132 patients who were implanted with active-fixation leads for new pacemaker implantation or additional leads required due to disconnected/leaking leads. Pacing threshold was measured at 4 time points: before screw-in, immediately, and 5 and 10 minutes after screw-in. If the pacing threshold was > 1.5 volts (V) at 5 minutes, we changed the pacing site so that it became ? 1.5 V. A total of 169 retractable leads (Medtronic: 107 leads, St. Jude Medical: 62 leads) and 33 Sweet-Tip leads (Boston: 33 leads) were implanted. Eighty-nine leads were implanted in the atrium and 113 leads in the ventricle. Seventy patients were implanted with both atrial and ventricular leads. The pacing threshold of Sweet-Tip leads increased immediately after screw-in, while that of retractable leads decreased (Sweet-Tip: 0.20 ± 0.57 V, Retractable: -0.15 ± 0.53 V, P < 0.05). The pacing threshold of both types of leads decreased similarly from immediately to 5 minutes after screw-in (Sweet Tip: -0.29 ± 0.43 V, Retractable: -0.25 ± 0.36 V, P = NS). Few changes in the threshold were detected between 5 and 10 minutes. Because the pacing threshold of Sweet-Tip active-fixation leads increased immediately after screw-in and that of both type leads decreased from immediately to 5 minutes, we should measure the pacing threshold from 5 minutes after screw-in. PMID:22688314

  15. Screw prominences related to palmar locking plating of distal radius

    Microsoft Academic Search

    T. S. Sügün; N. Karabay; Y. Gürbüz; K. Özaksar; T. Toros; M. Kayalar

    2011-01-01

    Fixation of unstable distal radius fractures with palmar locking plates provides a stable reduction and early return of function, but complications arising from unrecognized dorsally prominent screws penetrating the extensor compartments are increasingly reported. Standard radiographs and fluoroscopy may not adequately visualize screw lengths, owing to the complex shape of the dorsum of the distal radius. We examined 46 distal

  16. Double-Bundle Anterior Cruciate Ligament Reconstruction Using Hamstring Autografts and Bioabsorbable Interference Screw Fixation Prospective, Randomized, Clinical Study With 2Year Results

    Microsoft Academic Search

    Timo Järvelä; Anna-Stina Moisala; Raine Sihvonen; Sally Järvelä; Pekka Kannus; Markku Järvinen

    Results: There were no differences between the study groups preoperatively. Seventy-three patients (95%) were available at a minimum 2-year follow-up (range, 24-35 mo). The rotational stability of the knee, as evaluated by the pivot-shift test, was the best in the patients in the double-bundle group. In addition, the patients in the single-bundle groups had more graft failures than those in

  17. Minimally Invasive Pedicle Screw Placement in A Case of L4 Fracture: Case Report with Review of Literature

    PubMed Central

    Agrawal, Abhishek; Mizuno, Junichi; Kato, Yoko; Inoue, Tatsushi; Sano, Hirotoshi

    2010-01-01

    Introduction: Pedicle screw instrumentation provides a rigid construct to promote fusion in cases of spinal trauma and degenerative diseases. Minimally invasive percutaneous technique in lumbar spine is a safe and reliable procedure as compared to the well established Magerl technique. It is a straight forward alternative to open approaches or minimally invasive ones and the accuracy of screw placement is also similar to that reported for other techniques. Case Report: A 16 year old high school boy presented to us with accidental fall from third floor. He was suffering from common cold with resulting high fever. He developed low back ache with bilateral radiculopathy and weakness of dorsiflexors. Neuro-imaging revealed a burst fracture of L4 vertebral body (type A 3.3 according to Magerl/AO spine classification), with bone fragments compromising the spinal canal. Delayed surgery was planned in view of anticipated excessive bleeding from the wound site in addition to poor general condition. Using a bone impactor, the bony fragments were impacted back into the original vertebral body space. Sextant (Medtronic Sofamor Danek, Tennessee, USA) percutaneous pedicle screw and rod fixation device was then used as a rigid construct to stabilize the lumbar spine. Post-operative CT scan and MRI revealed accurate pedicle screw fixation with adequately decompressed spinal canal. Conclusion: Short segment fusion with minimally invasive pedicle screwing following decompression of cauda equina was considered to be a minimally invasive approach for this case. PMID:22028760

  18. Evaluation of 3 Fixation Devices for Tibial-Sided Anterior Cruciate Ligament Graft Backup Fixation.

    PubMed

    Verioti, Christopher A; Sardelli, Matthew C; Nguyen, Tony

    2015-07-01

    We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for anterior cruciate ligament reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw (all Arthrex). Thirty skeletally mature porcine tibiae were used. The first group was prepared by graft fixation within the tibial tunnel using only an interference screw. The second and third groups included an interference screw with 2 types of secondary fixation: 4.5-mm bicortical post and SwiveLock anchor. Mechanical testing consisted of 500 cycles between 50 and 250 N at 1 Hz, followed by a pull to failure conducted at 20 mm per minute. Ultimate load-to-failure testing demonstrated the largest mean (SD) load tolerated in the post/washer group, 1148 (186) N, versus the SwiveLock group, 1007 (176) N, and the screw-only group, 778 (139) N. There was no statistical difference between the 2 backup fixation groups. Use of a SwiveLock anchor as backup fixation at the tibial side in soft-tissue anterior cruciate ligament reconstruction is a safe, effective alternative to a bicortical post and provides statistically equivalent pullout strength with unlikely requirement for future hardware removal. PMID:26161768

  19. Cell-specific CO2 fixation rates of two distinct groups of plastidic protists in the Atlantic Ocean remain unchanged after nutrient addition.

    PubMed

    Grob, Carolina; Jardillier, Ludwig; Hartmann, Manuela; Ostrowski, Martin; Zubkov, Mikhail V; Scanlan, David J

    2015-04-01

    To assess the role of open-ocean ecosystems in global CO2 fixation, we investigated how picophytoplankton, which dominate primary production, responded to episodic increases in nutrient availability. Previous experiments have shown nitrogen alone, or in combination with phosphorus or iron, to be the proximate limiting nutrient(s) for total phytoplankton grown over several days. Much less is known about how nutrient upshift affects picophytoplankton CO2 fixation over the duration of the light period. To address this issue, we performed a series of small volume (8-60 ml) - short term (10-11 h) nutrient addition experiments in different regions of the Atlantic Ocean using NH4 Cl, FeCl3 , K medium, dust and nutrient-rich water from 300 m depth. We found no significant nutrient stimulation of group-specific CO2 fixation rates of two taxonomically and size-distinct groups of plastidic protists. The above was true regardless of the region sampled or nutrient added, suggesting that this is a generic phenomenon. Our findings show that at least in the short term (i.e. daylight period), nutrient availability does not limit CO2 fixation by the smallest plastidic protists, while their taxonomic composition does not determine their response to nutrient addition. PMID:25345650

  20. A finite element parametric study of clavicle fixation plates.

    PubMed

    Pendergast, Megan; Rusovici, Razvan

    2015-06-01

    A finite element simulation on a fracture fixated clavicle was performed to study the effects of different fracture fixation parameters on the callus region. Specifically, parameters such as plate material, thickness, plate/bone gap, screw length, and locking vs. non-locking screws were explored. Plate thickness and locking vs. non-locking screws were found to be influential to construct stiffness where plate/bone gap and number of screws were not as sensitive. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25641811

  1. Anatomical study of axis for odontoid screw thickness, length, and angle

    PubMed Central

    Tun, Kagan; Cemil, Berker; Yorubulut, Mehmet; Karahan, S. Tuna; Tekdemir, Ibrahim

    2008-01-01

    Anterior odontoid screw fixation is a safe and effective method for treatment of odontoid fractures. The screw treads should fit into the odontoid medulla, should pass the fracture line, and should pull fractured odontoid tip against body of axis in order to achieve optimum screw placement and treatment. This study has demonstrated optimal anterior odontoid screw thickness, length, and optimal angle for safe and strong anterior odontoid screw placement. Dry bone axis vertebrae were evaluated by direct measurements, X-ray measurements, and computerized tomography (CT) measurements. The screw thickness (inner diameter of the odontoid) was measured as well as screw length (distance between anterior-inferior point body of axis and tip of odontoid), and screw angle (the angle between basis of axis and tip of odontoid). The inner diameter of odontoid bone was measured as 6.5 ± 1.9 mm, the screw length was 37.6 ± 3.3 mm, and the screw angle was 62.4 ± 4.7 on CT. There was no statistical difference between X-ray and CT in the measurements of screw thickness and angle. X-ray and CT measurements are both safe methods to determine the inner odontoid diameter and angle preoperatively. Screw length should be measured on CT only. To provide safe and strong anterior odontoid screw fixation, screw thickness, length, and angle should be known preoperatively, and these can be measured on X-ray and CT. PMID:19005694

  2. Biomechanical and morphometric evaluation of occipital condyle for occipitocervical segmental fixation.

    PubMed

    Hong, Jae Taek; Takigawa, Tomoyuki; Sugisaki, Keizo; Espinoza Orías, Alejandro A; Inoue, Nozomu; An, Howard S

    2011-01-01

    Two recent novel techniques of occipital fixation are the occipitoatlantal (C0-C1) transarticular screw technique and the direct occipital condyle screw technique. The present study evaluated and compared the biomechanical stability of the direct occipital condyle screw and C0-C1 transarticular screw with the established method for craniocervical spine fixation using the midline occipital keel screw and C1 lateral mass screw. Morphometric evaluation of the occipital condyle and the hypoglossal canal was performed to avoid hypoglossal nerve injury during the screw placement. Thirteen recently frozen cadaveric specimens were used. The occipital condyle anatomy and the hypoglossal canal dimension were measured using reconstructed computed tomography images. Insertion torque and pullout strength were evaluated to compare the midline occipital keel screw, C0-C1 transarticular screw, C1 lateral mass screw, and direct occipital condyle screw. The dimensions of the occipital condyle allow use of a 3.5 or 4.0-mm diameter screw. Mean pullout strength was 1619.6 N for the midline occipital keel screw, 870.7 N for the C0-C1 transarticular screw, 707.0 N for the C1 lateral mass screw, and 431.7 N for the direct occipital condyle screw. Mean insertion torque was 0.55 Nm for the midline occipital keel screw, 0.32 Nm for the C0-C1 transarticular screw, 0.14 Nm for the C1 lateral mass screw, and 0.11 Nm for the direct occipital condyle screw. The condylar anatomy allows direct insertion of the occipital condyle screw and C0-C1 transarticular screw. These techniques are suitable options for the treatment of craniovertebral junction instabilities in selected patients. PMID:22027245

  3. The acetabular component in total hip arthroplasty. Evaluation of different fixation principles.

    PubMed

    Thanner, J

    1999-08-01

    Initial stability is necessary for permanent fixation of acetabular cups. Biologic reactions to submicron particles such as localized bone resorption may lead to implant failure. The aim of the study was to evaluate different fixation principles of acetabular components. Four randomized studies and one case-control study were performed to evaluate different bone cements, different cup designs, use of ceramic coating or not, different type of screws and the need of additional screw fixation or not. Radiostereometry (RSA) makes it possible to analyze small translations and rotations of implants with a high accuracy. This method is suitable for evaluation of early stability and was used in four of the studies. Clinical and radiological follow-up were performed regularly. The cements were tested in the laboratory. 30 patients (mean age 71 years, range: 63-76) received total hip arthroplasties and were randomised to fixation with Boneloc (14) or Palacos cum gentamicin (16) bone cement. The curing temperature was 23 degrees lower for the Boneloc cement but the tensile strength was reduced and the elastic modulus was lower compared to Palacos. The proximal cup migration was greater in the Boneloc group up to 12 months (p 0.04) and these cups migrated medially in contrast to a small lateral migration seen in the Palacos group (p 0.04). Radiolucencies were more pronounced in the Boneloc group at 12 months (p 0.04). 155 patients (171 hips, mean age 50 years, range: 24-64) received uncemented hip arthroplasties. 84 hips were randomised to the PCA and 87 to the Harris-Galante I designs. The 10-year survival rates were 85% for the PCA and 99% for the Harris-Galante I cups (revision as end-point). The wear and clinical results did not differ. 43 patients (mean age 60 years, range 44-68) received uncemented porous cups with a titanium mesh in pure titanium (Harris-Galante II) and were randomised to additional fixation with either biodegradable screws (23, poly-L-lactic acid, PLLA) or screws made of titanium alloy (20). Increased proximal and medial-lateral translations (p 0.02, 0.04) but less rotation around the longitudinal axis (p 0.04) were seen in the PLLA group up to 2 years. There were also more pronounced radiolucencies anteriorly in this group at 2 years. The clinical results did not differ. 23 uncemented porous cups (Harris-Galante II) with hydroxyapatite-tricalciumphosphate coating (HA/TCP) were pair-wise matched to uncoated cups. Up to 2 years, decreased rotations around the horizontal axis were recorded in the HA/TCP-coated cups. Central postoperative gaps were more frequently seen in the HA/TCP group (p < 0.01), but at 2 years radiolucencies were more pronounced in the uncoated group (p < 0.01). The wear and clinical results did not differ. 62 patients (64 hips, mean age 56 years, range: 32-75) were randomized to porous Trilogy cups with (30) and without (34) cluster holes for additional screw fixation. Up to 2 years there were no differences in migration, wear, radiographic findings or clinical results. In conclusion Boneloc cement was associated with poor fixation due to inferior mechanical properties. The PLLA screws did not provide sufficient stability. Unacceptably high failure rates were recorded for the PCA cup. HA/TCP coating improved the fixation and the interface of porous cups. HA/TCP coated porous cups can be fixed without adjunctive screw fixation. PMID:10572504

  4. A new concept for implant fixation: bone-to-bone biologic fixation.

    PubMed

    Kim, D Y; Kim, J R; Jang, K Y; Lee, K B

    2015-01-01

    Many attempts have been made to reduce complications of bone implant, such as pedicle screw loosening. To address this problem, the authors suggest a new concept of bone-to-bone biologic fixation using recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded cannulated pedicle screws. Recombinant human bone morphogenetic protein-2 is an osteoinductive cytokine. Four types of titanium pedicle screws were tested (uncannulated, cannulated with no loading, beta-tricalcium phosphate (TCP)-loaded, and TCP/BMP2 loaded) using 16 miniature pigs. Radiological evaluation was conducted to assess the fusion and loosening of pedicle screws. Twelve weeks after implantation, peak torsional extraction torque was measured, and the pedicle screw and bone interface was evaluated by micro-computed tomography (µCT) and histologic examination. The mean value of the radiological score was significantly greater in the TCP/BMP2 loaded group at 12 weeks post-operation compared to those in the other groups. CT images showed distinct bone formation surrounding TCP/BMP2 loaded cannulated pedicle screws compared to the other groups. Mean extraction torsional peak torque at 12 weeks postoperative was more than 10-fold higher in the TCP/BMP2 loaded pedicle screw group than in the other groups. Bone surface and bone volume, as quantitated through µCT, were higher in the TCP/BMP2 loaded group. Histologic examination revealed bone-to-bone fixation at the interface of pedicle screws and pre-existing bone. Bone-to-bone biologic fixation through the holes of TCP/BMP2 loaded pedicle screws significantly increased fixation strength and represents a novel method that can be applied to osteoporotic or tumour spine surgeries. PMID:25978116

  5. Tangential View and Intraoperative Three-Dimensional Fluoroscopy for the Detection of Screw-Misplacements in Volar Plating of Distal Radius Fractures

    PubMed Central

    Rausch, Sascha; Marintschev, Ivan; Graul, Isabel; Wilharm, Arne; Klos, Kajetan; Hofmann, Gunther O.; Florian Gras, Marc

    2015-01-01

    Background: Volar locking plate fixation has become the gold standard in the treatment of unstable distal radius fractures. Juxta-articular screws should be placed as close as possible to the subchondral zone, in an optimized length to buttress the articular surface and address the contralateral cortical bone. On the other hand, intra-articular screw misplacements will promote osteoarthritis, while the penetration of the contralateral bone surface may result in tendon irritations and ruptures. The intraoperative control of fracture reduction and implant positioning is limited in the common postero-anterior and true lateral two-dimensional (2D)-fluoroscopic views. Therefore, additional 2D-fluoroscopic views in different projections and intraoperative three-dimensional (3D) fluoroscopy were recently reported. Nevertheless, their utility has issued controversies. Objectives: The following questions should be answered in this study; 1) Are the additional tangential view and the intraoperative 3D fluoroscopy useful in the clinical routine to detect persistent fracture dislocations and screw misplacements, to prevent revision surgery? 2) Which is the most dangerous plate hole for screw misplacement? Patients and Methods: A total of 48 patients (36 females and 13 males) with 49 unstable distal radius fractures (22 x 23 A; 2 x 23 B, and 25 x 23 C) were treated with a 2.4 mm variable angle LCP Two-Column volar distal radius plate (Synthes GmbH, Oberdorf, Switzerland) during a 10-month period. After final fixation, according to the manufactures' technique guide and control of implant placement in the two common perpendicular 2D-fluoroscopic images (postero-anterior and true lateral), an additional tangential view and intraoperative 3D fluoroscopic scan were performed to control the anatomic fracture reduction and screw placements. Intraoperative revision rates due to screw misplacements (intra-articular or overlength) were evaluated. Additionally, the number of surgeons, time and radiation-exposure, for each step of the operating procedure, were recorded. Results: In the standard 2D-fluoroscopic views (postero-anterior and true lateral projection), 22 screw misplacements of 232 inserted screws were not detected. Based on the additional tangential view, 12 screws were exchanged, followed by further 10 screws after performing the 3D fluoroscopic scan. The most lateral screw position had the highest risk for screw misplacement (accounting for 45.5% of all exchanged screws). The mean number of images for the tangential view was 3 ± 2.5 images. The mean surgical time was extended by 10.02 ± 3.82 minutes for the 3D fluoroscopic scan. An additional radiation exposure of 4.4 ± 4.5seconds, with a dose area product of 39.2 ± 14.5 cGy/cm2 were necessary for the tangential view and 54.4 ± 20.9 seconds with a dose area product of 2.1 ± 2.2 cGy/cm2, for the 3D fluoroscopic scan. Conclusions: We recommend the additional 2D-fluoroscopic tangential view for detection of screw misplacements caused by overlength, with penetration on the dorsal cortical surface of the distal radius, predominantly observed for the most lateral screw position. The use of intraoperative 3D fluoroscopy did not become accepted in our clinical routine, due to the technical demanding and time consuming procedure, with a limited image quality so far. PMID:26101762

  6. Lateral Mass Fixation in the Subaxial Cervical Spine.

    PubMed

    Kurd, Mark F; Millhouse, Paul W; Schroeder, Gregory D; Kepler, Christopher K; Vaccaro, Alexander R

    2015-08-01

    The use of lateral mass screws and rods in the subaxial spine has become the standard method of fixation for posterior cervical spine fusions. Multiple techniques have been described for the placement of lateral mass screws, including the Magerl, the Anderson, and the An techniques. While these techniques are all slightly different, the overall goal is to obtain solid bony fixation while avoiding the neurovascular structures. The use of lateral mass screws has been shown to be a safe and effective technique for achieving a posterior cervical fusion. PMID:26049972

  7. Delayed Esophageal Pseudodiverticulum after Anterior Cervical Spine Fixation: Report of 2 Cases

    PubMed Central

    Sadrizadeh, Ali; Soltani, Ehsan; Abili, Mehdi; Dehghanian, Paria

    2015-01-01

    Introduction: Although perforation of the esophagus, in the anterior cervical spine fixation, is well established, cases with delayed onset, especially cases that present pseudodiverticulum, are not common. In addition, management of the perforation in this situation is debated. Case Report: Delayed esophageal pseudodiverticulum was managed in two patients with a history of anterior spine fixation. Patients were operated on, the loose plate and screws were extracted, the wall of the diverticulum was excised, the perforation on the nasogastric tube was suboptimally repaired, and a closed suction drain was placed there. The NGT was removed on the 7th day and barium swallow demonstrated no leakage at the operation site; therefore, oral feeding was started without any problem Conclusion: In cases with delayed perforation, fistula, or diverticulum removal of anterior fixation instruments, gentle repair of the esophageal wall without persistence on definitive and optimal perforation closure, wide local drainage, early enteral nutrition via NGT, and antibiotic prescription is suggested. PMID:25938087

  8. Treatment of fractures of the condylar head with resorbable pins or titanium screws: an experimental study.

    PubMed

    Schneider, Matthias; Loukota, Richard; Kuchta, Anne; Stadlinger, Bernd; Jung, Roland; Speckl, Katrin; Schmiedekampf, Robert; Eckelt, Uwe

    2013-07-01

    We aimed to compare in vivo the stability of fixation of condylar fractures in sheep using sonic bone welding and standard titanium screws. We assessed stability of the osteosynthesis and maintenance of the height of the mandibular ramus. Height decreased slightly in both groups compared with the opposite side. The volume of the condyle increased considerably in both groups mainly because callus had formed. The results showed no significant disadvantages for pin fixation compared with osteosynthesis using titanium screws. PMID:22901526

  9. Use of Cortical Bone Screws in Maxillofacial Surgery - A Prospective Study

    PubMed Central

    Satish, Madatanapalli; Rahman, NM Mujeeb; Reddy, V Sridhar; Yuvaraj, A; Muliyar, Sabir; Razak, P Abdul

    2014-01-01

    Background: The aim of this study is to evaluate the various applications of cortical bone screws in oral and maxillofacial surgery. Materials & Methods: The study was conducted in a teaching hospital located in, Bangalore, India, on 20 patients. These patients were categorized into three groups depending on the applications of these screws like, for achieving intermaxillary fixation in Group-1, for treatment of simple, undisplaced fractures by “Tension wire” method in Group-2, and further application of these screws were evaluated in Group-3. Different parameters were used to evaluate the efficacy of these screws. Results: In Group-1(n=12) there was satisfactory occlusion in all the patients with minimal incidence of complications. In Group-2 (n=4) post-operative reduction and fixation was satisfactory and in Group-3 (n=4) the function of these screws was satisfactory when it was used for vestibuloplasty and also as a suspension wiring in treatment of comminuted fracture of zygoma with minimal incidence of complications. Conclusion: Use of cortical bone screws is a valid alternative for achieving intermaxillary fixation, reduction and fixation of simple, undisplaced or minimally displaced fractures through Tension wire method owing to its simplicity, economy and ease of use, and as a fixation method for apically positioned flap in vestibuloplasty procedure. How to cite the article: Satish M, Rahman NM, Reddy VS, Yuvaraj A, Muliyar S, Razak PA. Use of Cortical Bone Screws in Maxillofacial Surgery - A Prospective Study. J Int Oral Health 2014;6(2):62-7. PMID:24876704

  10. Guide to radiation fixatives

    SciTech Connect

    Tawil, J.J.; Bold, F.C.

    1983-11-01

    This report identifies and then characterizes a variety of substances available in the market place for potential effectiveness as a fixative on radiologically contaminated surfaces. The substances include both generic chemicals and proprietary products. In selecting a fixative for a particular application, several attributes of the fixative may be relevant to the choice. These attributes include: toxicity, durability, and cleanliness and removability. In addition to the attributes of the fixative, one should also take into account certain characteristics of the site to be treated. These characteristics relate to climate, nature of the surface, use to which the treated surface will be put, subsequent cleanup operations, and type of neighboring surfaces. Finally, costs and potential environmental effects may influence the decision. A variety of fixatives are evaluated with respect to these various attributes and summarized in a reference table.

  11. Anatomic Consideration of the C1 Laminar Arch for Lateral Mass Screw Fixation via C1 Lateral Lamina : A Landmark between the Lateral and Posterior Lamina of the C1

    PubMed Central

    Kim, Jung-Hwan; Kwak, Dai-Soon; Han, Seung-Ho; Cho, Sung-Min; You, Seung-Hoon

    2013-01-01

    Objective To clarify the landmark for deciding the entry point for C1 lateral mass screws via the posterior arch by using 3-dimensional (3D) computed images. Methods Resnick insisted that the C1 posterior arch could be divided into pure posterior and lateral lamina (C1 pedicle). Authors studied where this transition point (TP) is located between the posterior lamina and the C1 pedicle and how it can be recognized. The 3D computed images of 86 cadaver C1s (M : F=45 : 41) were used in this study. Results The superior ridge of the C1 posterior arch had 2 types of orientation. One was in the vertical direction in the C1 posterior lamina and the other was in the horizontal direction in the C1 pedicle. The TP was located at the border between the 2 areas, the same site as the posterior end of the groove of the vertebral artery. On posterior-anterior projection, the posterior arch was sharpened abruptly at TP. We were unable to identify the TP in 6.4% of specimens due to complete or partial osseous bridges. A total of 93.8% of the TP were located between the most enlarged point of the spinal canal and the medial wall of the vertebral artery. Conclusion The anatomic entry zone of C1 lateral laminar screws was clarified and identified based on the TP by using preoperative 3D computed images. PMID:24044076

  12. Biomechanical testing of implant free wedge shaped bone block fixation for bone patellar tendon bone anterior cruciate ligament reconstruction in a bovine model

    PubMed Central

    2010-01-01

    Background The use of an interference fit wedged bone plug to provide fixation in the tibial tunnel when using bone-patellar tendon-bone autograft for anterior cruciate ligament reconstruction offers many theoretic advantages including the potential to offer a more economical and biological alternative to screw fixation. This technique has not been subjected to biomechanical testing. We hypothesised that a wedged bone plug fixation technique provides equivalent tensile load to failure as titanium interference screw fixation. Methods In a controlled laboratory setting, anterior cruciate ligament reconstruction was performed in 36 bovine knees using bone-patella-bone autograft. In 20 knees tibial fixation relied upon a standard cuboid bone block and interference screw. In eight knees a wedge shaped bone block with an 11 mm by 10 mm base without a screw was used. In a further eight knees a similar wedge with a 13 mm by 10 mm base was used. Each specimen used a standard 10 mm tibial tunnel. The reconstructions were tested biomechanically in a physiological environment using an Instron machine to compare ultimate failure loads and modes of failure. Results Statistical analysis revealed no significant difference between wedge fixation and screw fixation (p = 0.16), or between individual groups (interference screw versus 11 mm versus 13 mm wedge fixation) (P = 0.35). Conclusions Tibial tunnel fixation using an impacted wedge shaped bone block in anterior cruciate ligament reconstruction has comparable ultimate tensile strength to titanium interference screw fixation. PMID:20813059

  13. Fractures of the Proximal Fifth Metatarsal: Percutaneous Bicortical Fixation

    PubMed Central

    Mahajan, Vivek; Chung, Hyun Wook

    2011-01-01

    Background Displaced intraarticular zone I and displaced zone II fractures of the proximal fifth metatarsal bone are frequently complicated by delayed nonunion due to a vascular watershed. Many complications have been reported with the commonly used intramedullary screw fixation for these fractures. The optimal surgical procedure for these fractures has not been determined. All these observations led us to evaluate the effectiveness of percutaneous bicortical screw fixation for treating these fractures. Methods Twenty-three fractures were operatively treated by bicortical screw fixation. All the fractures were evaluated both clinically and radiologically for the healing. All the patients were followed at 2 or 3 week intervals till fracture union. The patients were followed for an average of 22.5 months. Results Twenty-three fractures healed uneventfully following bicortical fixation, with a mean healing time of 6.3 weeks (range, 4 to 10 weeks). The average American Orthopaedic Foot & Ankle Society (AOFAS) score was 94 (range, 90 to 99). All the patients reported no pain at rest or during athletic activity. We removed the implant in all cases at a mean of 23.2 weeks (range, 18 to 32 weeks). There was no refracture in any of our cases. Conclusions The current study shows the effectiveness of bicortical screw fixation for displaced intraarticular zone I fractures and displaced zone II fractures. We recommend it as one of the useful techniques for fixation of displaced zone I and II fractures. PMID:21629475

  14. Suture Bridge Fixation of a Femoral Condyle Traumatic Osteochondral Defect

    PubMed Central

    Bowers, Andrea L.

    2008-01-01

    Internal fixation of a traumatic osteochondral defect presents a challenge in terms of obtaining anatomic reduction, fixation, and adequate compression for healing. Fixation with countersunk intraarticular screws, Herbert screws, bioabsorbable screws and pins, mini-cancellous screws, and glue tissue adhesive have been reported with varying results. We present an alternative fixation method used in two patients for femoral condylar defects that achieved anatomic reduction with compression via a cruciate-shaped suture bridge construct tied down over a bony bridge. This fixation method allowed early passive range of motion and permitted high-quality MRI for followup of fracture healing and articular cartilage integrity. Arthroscopic examination of one of two patients at 6 months followup showed the gross appearance of a healed, anatomically reduced fracture. With 1 year followup for one patient and 2 years for the other, the patients have resumed activity as tolerated with full, painless range of motion at the knee. Longer-term outcomes are unknown. However, the suture bridge is an alternative means of fixation with encouraging early results for treatment of traumatic osteochondral fragments in the knee. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18584263

  15. Absorbable Screws Versus Metallic Screws for Distal Tibiofibular Syndesmosis Injuries: A Meta-Analysis.

    PubMed

    Xie, Yuanlong; Cai, Lin; Deng, Zhouming; Ran, Bing; Hu, Chao

    2015-01-01

    A meta-analysis was performed to investigate the outcomes between absorbable screw (AS) and metallic screw (MS) fixation for distal tibiofibular syndesmosis injuries (DTSIs). Randomized controlled trials comparing AS versus MS fixation in DTSIs were searched systematically, and the outcomes were analyzed using Review Manager Software, version 5.2. The risk ratio (RR) or mean difference with the 95% confidence interval (CI) was calculated using the fixed effects or random effects model. A total of 16 studies were included in the meta-analysis. No statistically significant difference was found between AS and MS fixation in excellent and good functional recovery rate (RR 1.11, 95% CI 1.00 to 1.23, I(2) = 60%, p = .06), infection (RR 1.66, 95% CI 0.73 to 3.79, I(2) = 0%, p = .23), incidence of pain (RR 0.68, 95% CI 0.24 to 1.92, I(2) = 12%, p = .47), screw broken (RR 0.31, 95% CI 0.03 to 2.93, I(2) = %, p = .31), heterotopic ossification (RR 1.93, 95% CI 0.21 to 17.62, I(2) = 51%, p = .56; 472 cases in 4 studies), fracture healing time (mean difference -1.88, 95% CI -3.51 to -0.26, I(2) = 93%, p = .02,), duration of operation time (mean difference 7.64, 95% CI -3.80 to 19.09, I(2) = 98%, p = .19). The incidence of foreign body reaction was higher with AS fixation (RR 6.07, 95% CI 2.54 to 14.50, I(2) = 0%, p < .001). The reoperation rate was higher with MS fixation (RR 0.08, 95% CI 0.03 to 0.18, I(2) = 77%, p < .01). The functional outcomes of AS were as good as those with MS for DTSIs. Other than the foreign body reaction, the complications occurring after AS fixation were not as serious as those with MS fixation. AS fixation might be a preferable alternative for reconstruction of DTSIs. PMID:25956019

  16. Augmentation of implant fixation in osteoporotic bone.

    PubMed

    Jones, Clifford B

    2012-12-01

    Osteoporosis presents a dilemma for the orthopedic surgeon. Screw fixation within the bone is crucial for mechanical stabilization, maintenance of reduction, and ultimately, fracture healing. For the patient, soft bones and physiological fragility usually benefit from immediate weight bearing and mobility to avoid further disuse osteoporosis, deconditioning, and immobility. For implant companies, traditional screws, plates, and nails function for simple fractures and compliant patients. Locked plating has improved screw purchase in osteoporotic bone and has expanded fracture fixation capabilities but is not the panacea for all fractures. For orthopedic surgeons, traditional surgical augmentation for osteoporosis consisting of dual plating, augmentation with polymethyl methacrylate, joint replacement, and now locked plating are beneficial. In order to advance orthopedic care in the expanding population of elderly osteoporotic patients, modern solutions utilizing the dual properties of secure fixation and relatively flexible implants are required. Endosteal substitution, extraosteal substitution, and combined nail/plate combinations are methods of utilizing traditional implants in a nontraditional way. Nonsurgical augmentation of fracture fixation is also paramount. PMID:23054960

  17. Influence of micro- and nano-hydroxyapatite coatings on the osteointegration of metallic (Ti6Al4 V) and bioabsorbable interference screws: an in vivo study.

    PubMed

    Aksakal, B; Kom, M; Tosun, H B; Demirel, M

    2014-07-01

    The purpose of this study is to show and compare the fixation and osteointegration capability of metallic and bioabsorbable interference screws. For this, 8×20-mm interference screws were implanted into the bone tunnel in the proximal tibial metaphysis of sheep. The nano- (25 nm±0.8) and microscale (25 ?m±0.5) hydroxyapatite were both dip-coated on Ti6Al4 V interference screws via an in vivo study. After the initial 12 weeks of postoperative, the pullout test, histopathology, X-ray diffraction and scanning electron microscopy examinations were performed. This multidisiplined work showed that the coated screws particularly those with nano-sized-HA coating and the bioabsorbable screws enhanced fixation and provided better stabilization, bone ingrowth and osteointegration than that of uncoated and microscale HA-coated screws. The bioabsorbable screws showed better histopathologic results. PMID:23689912

  18. Screw dislocations in the field theory of elastoplasticity

    NASA Astrophysics Data System (ADS)

    Lazar, Markus

    2002-10-01

    A (microscopic) static elastoplastic field theory of dislocations with moment and force stresses is considered. The relationship between the moment stress and the Nye tensor is used for the dislocation Lagrangian. We discuss the stress field of an infinitely long screw dislocation in a cylinder, a dipole of screw dislocations and a coaxial screw dislocation in a finite cylinder. The stress fields have no singularities in the dislocation core and they are modified in the core due to the presence of localized moment stress. Additionally, we calculated the elastoplastic energies for the screw dislocation in a cylinder and the coaxial screw dislocation. For the coaxial screw dislocation we find a modified formula for the so-called Eshelby twist which depends on a specific intrinsic material length.

  19. Screw dislocations in the field theory of elastoplasticity

    E-print Network

    Markus Lazar

    2002-09-30

    A (microscopic) static elastoplastic field theory of dislocations with moment and force stresses is considered. The relationship between the moment stress and the Nye tensor is used for the dislocation Lagrangian. We discuss the stress field of an infinitely long screw dislocation in a cylinder, a dipole of screw dislocations and a coaxial screw dislocation in a finite cylinder. The stress fields have no singularities in the dislocation core and they are modified in the core due to the presence of localized moment stress. Additionally, we calculated the elastoplastic energies for the screw dislocation in a cylinder and the coaxial screw dislocation. For the coaxial screw dislocation we find a modified formula for the so-called Eshelby twist which depends on a specific intrinsic material length.

  20. Cervical screw missing secondary to delayed esophageal fistula: case report.

    PubMed

    Cagli, Sedat; Isik, H Serdar; Zileli, Mehmet

    2009-10-01

    Although anterior surgical approaches to the cervical spine have become popular and safe in recent years, they also have some complications. We present a case of loss of an anterior cervical plate screw by the natural tracts. The patient was a 47- year-old woman who was operated on for cervical spondylotic myelopathy at another institution. Surgical interference included two levels of anterior discectomy, iliac graft placement and fixation using plate and screws. Two years later, plate dislocation and partial migration of the upper screws were observed. After 7 years the patient complained of dysphagia and she accepted removal of the osteosynthesis. Radiographical examination showed that one of the upper screws was missing and two lower screws were broken. Esophageal perforation was found during the surgery and repaired. Further progress was favourable. Complications associated with esophageal perforation may range from massive infection and death to spontaneous recovery. Erosion of the esophageal wall due to extruded bulky constructs may lead to a persistent fistula, abscess or septic diffusion. Spontaneous perforation of the esophagus and screw loss via the gastrointestinal tract make this case interesting.. PMID:19847769

  1. Parallel analysis of finite element model controlled trial and retrospective case control study on percutaneous internal fixation for vertical sacral fractures

    PubMed Central

    2013-01-01

    Background Although percutaneous posterior-ring tension-band metallic plate and percutaneous iliosacral screws are used to fix unstable posterior pelvic ring fractures, the biomechanical stability and compatibility of both internal fixation techniques for the treatment of Denis I, II and III type vertical sacral fractures remain unclear. Methods Using CT and MR images of the second generation of Chinese Digitized Human “male No. 23”, two groups of finite element models were developed for Denis I, II and III type vertical sacral fractures with ipsilateral superior and inferior pubic ramus fractures treated with either a percutaneous metallic plate or a percutaneous screw. Accordingly, two groups of clinical cases that were fixed using the above-mentioned two internal fixation techniques were retrospectively evaluated to compare postoperative effect and function. Parallel analysis was performed with a finite element model controlled trial and a case control study. Results The difference of the postoperative Majeed standards and outcome rates between two case groups was no statistically significant (P?>?0.05). Accordingly, the high values of the maximum displacements/stresses of the plate-fixation model group approximated those of the screw-fixation model group. However, further simulation of Denis I, II and III type fractures in each group of models found that the biomechanics of the plate-fixation models became increasingly stable and compatible, whereas the biomechanics of the screw-fixation models maintained tiny fluctuations. When treating Denis III fractures, the biomechanical effects of the pelvic ring of the plate-fixation model were better than the screw-fixation model. Conclusions Percutaneous plate and screw fixations are both appropriate for the treatment of Denis I and II type vertical sacral fractures; whereas percutaneous plate fixation appears be superior to percutaneous screw fixation for Denis III type vertical sacral fracture. Biomechanical evidence of finite element evaluations combined with clinical evidence will contribute to our ability to distinguish between indications that require plate or screw fixation for vertical sacral fractures. PMID:23879618

  2. Mechanical properties of two canine iliac fracture fixation systems

    E-print Network

    VanGundy, Thomas Eugene

    1988-01-01

    to plate fixation for o lique canine iliac fracture fixation. The savings on implant fees and ease of lag screw application also may be a consideration for the veterinary surgeon. REFERENCES 1. Brinker WO, Piermattei DL, Flo GL. Handbook of Small..., for providng the funding that made this project possible. vi1 TABLE OF CONTENTS Page INTRODUCTION MATERIALS AND METHODS RESULTS Specimen Dimensions Static Testing Dynamic Testing DISCUSSION Pretesting Considerations Testing Considerations...

  3. Intra-operative computer navigation guided cervical pedicle screw insertion in thirty-three complex cervical spine deformities

    PubMed Central

    Rajasekaran, S.; Kanna, P. Rishi Mugesh; Shetty, T. Ajoy Prasad

    2010-01-01

    Background: Cervical pedicle screw fixation is challenging due to the small osseous morphometrics and the close proximity of neurovascular elements. Computer navigation has been reported to improve the accuracy of pedicle screw placement. There are very few studies assessing its efficacy in the presence of deformity. Also cervical pedicle screw insertion in children has not been described before. We evaluated the safety and accuracy of Iso-C 3D-navigated pedicle screws in the deformed cervical spine. Materials and Methods: Thirty-three patients including 15 children formed the study group. One hundred and forty-five cervical pedicle screws were inserted using Iso-C 3D-based computer navigation in patients undergoing cervical spine stabilization for craniovertebral junction anomalies, cervico-thoracic deformities and cervical instabilities due to trauma, post-surgery and degenerative disorders. The accuracy and containment of screw placement was assessed from postoperative computerized tomography scans. Results: One hundred and thirty (89.7%) screws were well contained inside the pedicles. Nine (6.1%) Type A and six (4.2%) Type B pedicle breaches were observed. In 136 levels, the screws were inserted in the classical description of pedicle screw application and in nine deformed vertebra, the screws were inserted in a non-classical fashion, taking purchase of the best bone stock. None of them had a critical breach. No patient had any neurovascular complications. Conclusion: Iso-C navigation improves the safety and accuracy of pedicle screw insertion and is not only successful in achieving secure pedicle fixation but also in identifying the best available bone stock for three-column bone fixation in altered anatomy. The advantages conferred by cervical pedicle screws can be extended to the pediatric population also. PMID:20890413

  4. Subclavian artery injury secondary to clavicular plate fixation: a novel operative approach

    PubMed Central

    Perera, Kalpa G.; Clifford, Celia; Maddock, Lachlan

    2015-01-01

    We present the case of a 32-year-old male with a delayed symptomatic left subclavian artery pseudoaneurysm secondary to protruding screws from prior perpendicular clavicular plate fixations. The pseudoaneurysm development and our operative approach are unique to the few similar cases available in the literature. The patient presented with a progressive pulsatile mass behind his left clavicle associated with paraesthesia. Angiography demonstrated a subclavian pseudoaneurysm adjacent to a prominent fixation screw. Offending screws were removed and the pseudoaneurysm was repaired using a reversed greater saphenous vein graft. This case illustrates an unusual aetiology for pseudoaneurysm development and highlights a successful operative intervention. PMID:25877827

  5. Comparison of plate-screw systems used in mandibular fracture reduction: finite element analysis.

    PubMed

    Lovald, Scott T; Khraishi, Tariq; Wagner, Jon; Baack, Bret; Kelly, James; Wood, John

    2006-10-01

    A finite element model of the human dentate mandible has been developed to provide a comparison of fixation systems used currently for fracture reduction. Volume domains for cortical bone, cancellous bone, and teeth were created and meshed in ANSYS 8.0 based on IGES curves created from computerized tomography data. A unilateral molar clench was loaded on the model with a fracture gap simulated along the symphysis. Results based on Von Mises stress in cortical and cancellous bone surrounding the screws, and on fracture surface spatial fixation, show some relative differences between different screw-plate systems, yet all were judged to be appropriate in their reduction potential. PMID:16995751

  6. Helical screw viscometer

    DOEpatents

    Aubert, J.H.; Chapman, R.N.; Kraynik, A.M.

    1983-06-30

    A helical screw viscometer for the measurement of the viscosity of Newtonian and non-Newtonian fluids comprising an elongated cylindrical container closed by end caps defining a circular cylindrical cavity within the container, a cylindrical rotor member having a helical screw or ribbon flight carried by the outer periphery thereof rotatably carried within the cavity whereby the fluid to be measured is confined in the cavity filling the space between the rotor and the container wall. The rotor member is supported by axle members journaled in the end caps, one axle extending through one end cap and connectable to a drive source. A pair of longitudinally spaced ports are provided through the wall of the container in communication with the cavity and a differential pressure meter is connected between the ports for measuring the pressure drop caused by the rotation of the helical screw rotor acting on the confined fluid for computing viscosity.

  7. The utility of the fluoroscopic skyline view during volar locking plate fixation of distal radius fractures.

    PubMed

    Vaiss, Lucile; Ichihara, Satoshi; Hendriks, Sarah; Taleb, Chihab; Liverneaux, Philippe; Facca, Sybille

    2014-11-01

    Background?Open reduction and internal fixation (ORIF) using a volar locking plate is a common method for treating displaced distal radius fractures. There is, however, the risk of extensor tendon rupture due to protrusion of the screw tips past the dorsal cortex, which cannot always be adequately seen on a lateral fluoroscopic view. We therefore wished to compare the sensitivity of an intraoperative fluoroscopic skyline view to a lateral fluorosocopic view in detecting past pointing of these screws. Material and Methods?Our series included 75 patients with an average age of 59 years who underwent volar locked plate fixation of a displaced distal radius fracture. Intraoperative anteroposterior (AP), lateral, and skyline fluoroscopic views were performed in each case. The number of screws that were seen to protrude past the dorsal cortex of the distal fracture fragment were recorded for both the lateral and skyline views. The number of screws that required exchange was also documented. Results?No screws were seen to protrude past the dorsal cortical bone on the lateral fluroscopic views. 15 of 300 screws (5%) were seen to protrude past the dorsal cortex by an average of 0.8?mm (range, 0.5 to 2 mm) and were exchanged for shorter screws in 11/75 patients. Conclusion?Our results demonstrate that the skyline is more sensitive than a lateral fluoroscopic view at demonstrating protrusion of the screws in the distal fracture fragment following volar locked plate fixation. Level of Evidence?IV. PMID:25364637

  8. Subtrochanteric femur fracture after removal of screws for femoral neck fracture in a child.

    PubMed

    Song, Kwang Soon; Lee, Si Wook

    2015-01-01

    Displaced femoral neck fractures are rare in children and are associated with a high rate of complications. Subtrochanteric fractures after cannulated screw fixation of femoral neck fractures in adults are well recognized, and there are several reports on the topic. However, there are no reports on complications related to hardware or subtrochanteric fractures after removal of the screws in the treatment of femoral neck fractures in children. Here we report the case of a 10-year-old boy who sustained a subtrochanteric fracture after the screw removal and healing that followed a femoral neck fracture. PMID:25566556

  9. A geometrical introduction to screw theory

    E-print Network

    Minguzzi, E

    2012-01-01

    Since the addition of applied forces must take into account the line of action, applied forces do not belong to a vector space. Screw theory removes this geometrical limitation and solves other mechanical problems by unifying, in a single concept, the translational and rotational degrees of freedom. Although venerable this theory is little known. By introducing some innovations, I show how screw theory can help us to rapidly develop several standard and less standard results in classical mechanics. The connection with the Lie algebra of the group of rigid maps is clarified.

  10. Numerical simulation research to both the external fixation surgery scheme of intertrochanteric fracture and the healing process, and its clinical application.

    PubMed

    Wang, Xian-Kang; Ye, Jin-Duo; Gu, Fu-Shun; Wang, Ai-guo; Zhang, Chun-Qiu; Tian, Qian-Qian; Li, Xue; Dong, Li-Min

    2014-01-01

    In this paper, the single arm external fixation of intertrochanteric fracture healing process after surgery was simulated to obtain a postoperative fracture healing and stress distribution in the external fixator. Firstly CT images of intertrochanteric fracture are reconstructed into the femur solid model. Then based, the external fixator is installed on the model, which lastly formed a finite element model of unilateral external fixation for intertrochanteric fracture. The calculated results show: during the beginning of the fracture healing, there is much higher stress in both screws and femur in the model with solid screws than that in the model with hollow screw. The stress of the femur in the model with hollow screw is more evenly. During the middle time of Fracture healing, stress in the femoral head significantly decreases. And the stress at fracture site gradually increased with the healing occurrence. According to the results, the authors designed hollow screws to use external fixation surgery. Surgery confirmed that the use of hollow screws in fractures treatment can satisfy the strength requirements, and can effectively reduce operative time, less patient suffering. The research for external fixation can provide a reference, and promote the use of external fixation hollow screws. PMID:24211947

  11. Treatment and complications in flaccid neuromuscular scoliosis (Duchenne muscular dystrophy and spinal muscular atrophy) with posterior-only pedicle screw instrumentation

    Microsoft Academic Search

    Hitesh N. Modi; Seung-Woo Suh; Jae-Young Hong; Jae-Woo Cho; Jong-Hoon Park; Jae-Hyuk Yang

    2010-01-01

    Literature has described treatment of flaccid neuromuscular scoliosis using different instrumentation; however, only one article\\u000a has been published using posterior-only pedicle screw fixation. Complications using pedicle screws in paralytic neuromuscular\\u000a scoliosis has not been described before. To present results and complications with posterior-only pedicle screws, a retrospective\\u000a study was carried out in 27 consecutive patients with flaccid neuromuscular scoliosis (Duchenne

  12. In vitro and in vivo studies on the degradation of high-purity Mg (99.99wt.%) screw with femoral intracondylar fractured rabbit model.

    PubMed

    Han, Pei; Cheng, Pengfei; Zhang, Shaoxiang; Zhao, Changli; Ni, Jiahua; Zhang, Yuanzhuang; Zhong, Wanrun; Hou, Peng; Zhang, Xiaonong; Zheng, Yufeng; Chai, Yimin

    2015-09-01

    High-purity magnesium (HP Mg) takes advantage in no alloying toxic elements and slower degradation rate in lack of second phases and micro-galvanic corrosion. In this study, as rolled HP Mg was fabricated into screws and went through in vitro immersion tests, cytotoxicity test and bioactive analysis. The HP Mg screws performed uniform corrosion behavior in vitro, and its extraction promoted cell viability, bone alkaline phosphatase (ALP) activity, and mRNA expression of osteogenic differentiation related gene, i.e. ALP, osteopontin (OPN) and RUNX2 of human bone marrow mesenchymal stem cells (hBMSCs). Then HP Mg screws were implanted in vivo as load-bearing implant to fix bone fracture and subsequently gross observation, range of motion (ROM), X-ray scanning, qualitative micro-computed tomography (?CT) analysis, histological analysis, bending-force test and SEM morphology of retrieved screws were performed respectively at 4, 8, 16 and 24 weeks. As a result, the retrieved HP Mg screws in fixation of rabbit femoral intracondylar fracture showed uniform degradation morphology and enough bending force. However, part of PLLA screws was broken in bolt, although its screw thread was still intact. Good osseointegration was revealed surrounding HP Mg screws and increased bone volume and bone mineral density were detected at fracture gap, indicating the rigid fixation and enhanced fracture healing process provided by HP Mg screws. Consequently, the HP Mg showed great potential as internal fixation devices in intra-articular fracture operation. PMID:26117658

  13. A novel fixation system for acetabular quadrilateral plate fracture: a comparative biomechanical study.

    PubMed

    Zha, Guo-Chun; Sun, Jun-Ying; Dong, Sheng-Jie; Zhang, Wen; Luo, Zong-Ping

    2015-01-01

    This study aims to assess the biomechanical properties of a novel fixation system (named AFRIF) and to compare it with other five different fixation techniques for quadrilateral plate fractures. This in vitro biomechanical experiment has shown that the multidirectional titanium fixation (MTF) and pelvic brim long screws fixation (PBSF) provided the strongest fixation for quadrilateral plate fracture; the better biomechanical performance of the AFRIF compared with the T-shaped plate fixation (TPF), L-shaped plate fixation (LPF), and H-shaped plate fixation (HPF); AFRIF gives reasonable stability of treatment for quadrilateral plate fracture and may offer a better solution for comminuted quadrilateral plate fractures or free floating medial wall fracture and be reliable in preventing protrusion of femoral head. PMID:25802849

  14. Strength analysis of clavicle fracture fixation devices and fixation techniques using finite element analysis with musculoskeletal force input.

    PubMed

    Marie, Cronskär

    2015-08-01

    In the cases, when clavicle fractures are treated with a fixation plate, opinions are divided about the best position of the plate, type of plate and type of screw units. Results from biomechanical studies of clavicle fixation devices are contradictory, probably partly because of simplified and varying load cases used in different studies. The anatomy of the shoulder region is complex, which makes it difficult and expensive to perform realistic experimental tests; hence, reliable simulation is an important complement to experimental tests. In this study, a method for finite element simulations of stresses in the clavicle plate and bone is used, in which muscle and ligament force data are imported from a multibody musculoskeletal model. The stress distribution in two different commercial plates, superior and anterior plating position and fixation including using a lag screw in the fracture gap or not, was compared. Looking at the clavicle fixation from a mechanical point of view, the results indicate that it is a major benefit to use a lag screw to fixate the fracture. The anterior plating position resulted in lower stresses in the plate, and the anatomically shaped plate is more stress resistant and stable than a regular reconstruction plate. PMID:25850983

  15. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  16. Dynamic-locking-screw (DLS)–leads to less secondary screw perforations in proximal humerus fractures

    PubMed Central

    2014-01-01

    Background Loss of reduction and screw perforation causes high failure rates in the treatment of proximal humerus fractures. The purpose of the present study was to evaluate the early postoperative complications using modern Dynamic Locking Screws (DLS 3.7) for plating of proximal humerus fractures. Methods Between 03/2009 and 12/2010, 64 patients with acute proximal humerus fractures were treated by angular stable plate fixation using DLSs in a limited multi-centre study. Follow-up examinations were performed three, six, twelve and twenty-four weeks postoperatively and any complications were carefully collected. Results 56 of 64 patients were examined at the six-month follow-up. Complications were observed in 12 patients (22%). In five cases (9%), a perforation of the DLS 3.7 occurred. Conclusions Despite the use of modern DLS 3.7, the early complications after plating of proximal humerus fractures remain high. The potential advantage of the DLS 3.7 regarding secondary screw perforation has to be confirmed by future randomized controlled trials. PMID:24894637

  17. A Pitfall in Fixation of Distal Humeral Fractures with Pre-Contoured Locking Compression Plate

    PubMed Central

    Jayakumar, Prakash; Ring, David

    2015-01-01

    Anatomically precontoured locking plates are intended to facilitate the fixation of articular fractures and particularly those associated with osteoporosis. Fractures of the distal humerus are relatively uncommon injuries where operative intervention can be exceptionally challenging. The distal humeral trochlea provides a very narrow anatomical window through which to pass a fixed-angle locking screw, which must also avoid the olecranon, coronoid, and radial fossae. We describe 3 patients (ages 27, 49, and 73 years) with a bicolumnar fracture of the distal humerus where very short distal locking screws were used. Intra-articular screw placement was avoided but loss of fixation occurred in two patients and a third was treated with a prolonged period of immobilization. We postulate that fixed-angle screw trajectories may make it difficult for the surgeon to place screws of adequate length in this anatomically confined region, and may lead to insufficient distal fixation. Surgical tactics should include placement of as many screws as possible into the distal fragment, as long as possible and that each screw passes through a plate without necessarily locking in. PMID:26110181

  18. Prevention of excessive medialisation of trochanteric fracture by a buttress screw: a novel method and finite element analysis.

    PubMed

    Mahaisavariya, Banchong; Chantarapanich, Nattapon; Riansuwan, Kongkhet; Sitthiseripratip, Kriskrai

    2014-09-01

    This paper proposes a novel method of using an antero-posterior buttress screw at the distal fragment just below the fracture site in conjunction with the sliding hip screw (SHS) to resist excessive femoral medialisation. A virtual assessment of the effectiveness of this new method was performed using the finite element analysis. The results indicate that the use ofa sliding hip screw (SHS) combined with a buttress screw can help resistfemoral medialisation better than using an SHS with no buttress screw. The von Mises equivalent stress (EQ ) was found to be in a safe range, which indicates increased integrity of the lateral wall with the addition of the buttress screw. PMID:25365905

  19. Novel posterior fixation keratoprosthesis

    NASA Astrophysics Data System (ADS)

    Lacombe, Emmanuel

    1992-08-01

    The keratoprosthesis is the last solution for corneally blind patients that cannot benefit from corneal transplants. Keratoprostheses that have been designed to be affixed anteriorly usually necessitate multi-step surgical procedures and are continuously subjected to the extrusion forces generated by the positive intraocular pressure; therefore, clinical results in patients prove inconsistent. We proposed a novel keratoprosthesis concept that utilizes posterior corneal fixation which `a priori' minimizes the risk of aqueous leakage and expulsion. This prosthesis is implanted in a single procedure thereby reducing the number of surgical complications normally associated with anterior fixation devices. In addition, its novel design makes this keratoprosthesis implantable in phakic eyes. With an average follow-up of 13 months (range 3 to 25 months), our results on 21 cases are encouraging. Half of the keratoprostheses were implanted in severe burn cases, with the remainder in cases of pseudo- pemphigus. Good visual results and cosmetic appearance were obtained in 14 of 21 eyes.

  20. The Screw-worm. 

    E-print Network

    Francis, M. (Mark)

    1890-01-01

    TEXAS AGRICULTURAL EXP II,HIMEXT Srl'ATION. BULLETIN No. 12, ~*fZkRP ** SEPTEMBER, 1890. .$, y~, 'TWORM. AGRICULTURAL' AND MECHANICAL COLLEGE OF TEXAS. All Bulletins of this Station are issued free. Any one interested... to Director. ,nt Agriculturist. . . naala~ant in Chemistrv. . . LVL~L~OI' . . Assists . . Assista A ..-:-A- TEXAS AGYLICULTUliAL EXYEliIMEXT STATION. THE SCREW-WORM. - . . . .. .-. -- M. FRANCIS, D. V. M. ~ - - In the First Annual Report...

  1. Drill Free Screws: a new form of osteosynthesis screw.

    PubMed

    Heidemann, W; Gerlach, K L; Gröbel, K H; Köllner, H G

    1998-06-01

    Although the application of self-tapping and non self-tapping screws is virtually universal in cranio-maxillofacial surgery, the inevitable, time consuming procedure of drilling a pilot hole has some potential disadvantages, such as damage to nerves, tooth roots or tooth germs, thermal necrosis of the bone and drill bit breakage. Drill Free Screws (DFS) are a recently developed type of osteosynthesis screws, having a tip like a cork screw and specially formed cutting flutes which enable insertion of the screws without drilling. DFS 1.5 and 2 mm were inserted into discs of wood, polyvinylchloride (PVC) and porcine mandibular bone of varying thicknesses between 2 and 4 mm. The values of insertion torque and maximum torque were recorded using an electric torque tester. Thereafter, the screws were inserted with a fixed torque and uniaxial pull out tests were performed. In comparison with this, the same procedure was performed using 1.5 and 2 mm self-tapping titanium screws. Ten trials for each screw-material-combination were conducted to determine insertion torque, maximum torque and pull out analysis. The results showed that the holding power of DFS lay between 70 and 104% of the holding power of self-tapping titanium screws; only in PVC was the difference more than 15%. PMID:9702635

  2. Tangential views of the articular surface of the distal radius—aid to open reduction and internal fixation of fractures

    Microsoft Academic Search

    Deepak Kumar; L Breakwell; S. C Deshmukh; B. K Singh

    2001-01-01

    Open reduction and internal fixation of comminuted, displaced intra-articular or potentially unstable fractures of the distal radius with plate and screws has increasingly become a favoured treatment. Intra-operative assessment of fixation with the help of an image intensifier has always been difficult because of the anatomy of the distal radius. Imaging of the implants placed as distal as possible to

  3. Bone registration method for robot assisted surgery: pedicle screw insertion.

    PubMed

    Abdel-Malek, K; McGowan, D P; Goel, V K; Kowalski, D; Smith, S B

    1997-01-01

    A registration method that identifies bone geometry with respect to a robotic manipulator arm is presented. Although the method is generally applicable to many orthopaedic internal fixation procedures, it was only demonstrated for the insertion of pedicle screws in vertebral bodies for spine fixation. The method relies upon obtaining an impression of the vertebral bodies. Computerized tomography (CT) scans of both vertebrae and mould are reconstructed using a computer aided engineering (CAE) system. From the reconstructions, the surgeon is able to do preoperative planning including selection of pedicle screw diameter, direction of screw through pedicle, point of entry and length of engagement. The three-dimensional models are than meshed to determine positions of the surgeon's preoperative plan relative to the mould. Intra-operative positions are defined in space by a mechanical fixture rigidly attached to the mould and designed to allow a manipulator end-effector to recognize the global coordinates of the in vivo spine. The theory and methodology were validated using a five-axis manipulator arm. This initial presentation assumes and allows no relative motion between vertebrae in vivo. PMID:9255999

  4. Low noise lead screw positioner

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (inventor)

    1986-01-01

    A very precise and low noise lead screw positioner, for positioning a retroreflector in an interferometer is described. A gas source supplies inert pressurized gas, that flows through narrow holes into the clearance space between a nut and the lead screw. The pressurized gas keeps the nut out of contact with the screw. The gas flows axially along the clearance space, into the environment. The small amount of inert gas flowing into the environment minimizes pollution. By allowing such flow into the environment, no seals are required between the end of the nut and the screw.

  5. Reduced bone tunnel enlargement post hamstring ACL reconstruction with poly- l-lactic acid\\/hydroxyapatite bioabsorbable screws

    Microsoft Academic Search

    James Robinson; Chris Huber; Paul Jaraj; Philippe Colombet; Michel Allard; Philippe Meyer

    2006-01-01

    Bone tunnel enlargement following anterior cruciate ligament (ACL) reconstruction can complicate revision surgery. This study compared postoperative tibial tunnel widening in patients who underwent arthroscopically assisted, single-incision, four-strand hamstring ACL reconstruction using a poly-l-lactic acid\\/hydroxyapatite blend (PLLA+HA) bioabsorbable interference screw for tibial fixation, with those in whom a plain poly-l-lactic acid (PLLA) screw was used. Thirty-four patients (13 with PLLA+HA

  6. Radiographic Evaluation of Dorsal Screw Penetration After Volar Fixed-Angle Plating of the Distal Radius: A Cadaveric Study

    Microsoft Academic Search

    Steven D. Maschke; Peter J. Evans; David Schub; Richard Drake; Jeffrey N. Lawton

    2007-01-01

    Introduction  Extensor tendon irritation and attritional tendon ruptures are potentially serious complications after open reduction and\\u000a internal fixation of distal radius fractures. These complications are well recognized after dorsal plating of distal radii;\\u000a and these are now being reported after errant screw placement during volar fixed-angle plating. Intraoperative detection of\\u000a improper screw placement is critical, as corrective action can be taken

  7. Comparison of Expansive Pedicle Screw and Polymethylmethacrylate-Augmented Pedicle Screw in Osteoporotic Sheep Lumbar Vertebrae: Biomechanical and Interfacial Evaluations

    PubMed Central

    Zhang, Bo; Xie, Qing-yun; Wang, Cai-ru; Liu, Jin-biao; Liao, Dong-fa; Jiang, Kai; Lei, Wei; Pan, Xian-ming

    2013-01-01

    Background It was reported that expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) could be used to increase screw stability in osteoporosis. However, there are no studies comparing the two kinds of screws in vivo. Thus, we aimed to compare biomechanical and interfacial performances of EPS and PMMA-PS in osteoporotic sheep spine. Methodology/Principal Findings After successful induction of osteoporotic sheep, lumbar vertebrae in each sheep were randomly divided into three groups. The conventional pedicle screw (CPS) was inserted directly into vertebrae in CPS group; PMMA was injected prior to insertion of CPS in PMMA-PS group; and the EPS was inserted in EPS group. Sheep were killed and biomechanical tests, micro-CT analysis and histological observation were performed at both 6 and 12 weeks post-operation. At 6-week and 12-week, screw stabilities in EPS and PMMA-PS groups were significantly higher than that in CPS group, but there were no significant differences between EPS and PMMA-PS groups at two study periods. The screw stability in EPS group at 12-week was significantly higher than that at 6-week. The bone trabeculae around the expanding anterior part of EPS were more and denser than that in CPS group at 6-week and 12-week. PMMA was found without any degradation and absorption forming non-biological “screw-PMMA-bone” interface in PMMA-PS group, however, more and more bone trabeculae surrounded anterior part of EPS improving local bone quality and formed biological “screw-bone” interface. Conclusions/Significance EPS can markedly enhance screw stability with a similar effect to the traditional method of screw augmentation with PMMA in initial surgery in osteoporosis. EPS can form better biological interface between screw and bone than PMMA-PS. In addition, EPS have no risk of thermal injury, leakage and compression caused by PMMA. We propose EPS has a great application potential in augmentation of screw stability in osteoporosis in clinic. PMID:24086381

  8. Comparison of costs in ankle fractures treated with absorbable or metallic fixation devices

    Microsoft Academic Search

    T. Juutilainen; H. Pätiälä; M. Ruuskanen; P. Rokkanen

    1997-01-01

    The economic costs of ankle fractures treated operatively with self-reinforced polyglycolide acid (SR-PGA) screws, with self-reinforced poly-L-lactide acid (SR-PLLA) screws or with metallic implants was determined. All patients were divided into three groups according to the fixation material used. Open and otherwise complicated fractures were excluded. The total expense of operations in each group was taken into account. The average

  9. Comparative clinical study of locking screws versus smooth locking pegs in volar plating of distal radius fractures.

    PubMed

    Boretto, J G; Pacher, N; Giunta, D; Gallucci, G L; Alfie, V; De Carli, P

    2014-09-01

    The present study was performed to test the null hypothesis on no difference in stability of fixation after volar plating of intra-articular distal radius fractures (AO C2-C3) with either locking smooth pegs or locking screws in a clinical setting. A retrospective evaluation included adult patients with C2-C3 AO fractures treated with a volar plate with locking smooth pegs or locking screws. Radiographic assessment was performed to evaluate extra- and intra-articular parameters in the early postoperative period and after bone union. Twenty-seven consecutive patients were included. Thirteen cases had fixation with locking screws and 14 had fixation with locking smooth pegs. Both groups had bone fragment displacement after fixation. However, there were no significant differences between the groups either in extra- or intra-articular parameters defined by Kreder et al. (1996). Our study shows that, in a clinical setting, there is no difference in stability fixation between locking screws or smooth locking pegs in C2-C3 distal radius fractures. PMID:24401740

  10. Validation of an improved method to calculate the orientation and magnitude of pedicle screw bending moments.

    PubMed

    Freeman, Andrew L; Fahim, Mina S; Bechtold, Joan E

    2012-10-01

    Previous methods of pedicle screw strain measurement have utilized complex, time consuming methods of strain gauge application, experience high failure rates, do not effectively measure resultant bending moments, and cannot predict moment orientation. The purpose of this biomechanical study was to validate an improved method of quantifying pedicle screw bending moment orientation and magnitude. Pedicle screws were instrumented to measure biplanar screw bending moments by positioning four strain gauges on flat, machined surfaces below the screw head. Screws were calibrated to measure bending moments by hanging certified weights a known distance from the strain gauges. Loads were applied in 30?deg increments at 12 different angles while recording data from two independent strain channels. The data were then analyzed to calculate the predicted orientation and magnitude of the resultant bending moment. Finally, flexibility tests were performed on a cadaveric motion segment implanted with the instrumented screws to demonstrate the implementation of this technique. The difference between the applied and calculated orientation of the bending moments averaged (±standard error of the mean (SEM)) 0.3?±?0.1?deg across the four screws for all rotations and loading conditions. The calculated resultant bending moments deviated from the actual magnitudes by an average of 0.00?±?0.00 Nm for all loading conditions. During cadaveric testing, the bending moment orientations were medial/lateral in flexion-extension, variable in lateral bending, and diagonal in axial torsion. The technique developed in this study provides an accurate method of calculating the orientation and magnitude of screw bending moments and can be utilized with any pedicle screw fixation system. PMID:23083202

  11. Technical tips: dualplate fixation technique for comminuted proximal humerus fractures.

    PubMed

    Choi, Sungwook; Kang, Hyunseong; Bang, Hyeongsig

    2014-08-01

    The authors report dualplate fixation technique for providing stable fixation in comminuted proximal humerus fractures. This technique has been used for proximal humerus fractures with metaphyseal comminution and provides excellent anatomical reduction and neck shaft angle (NSA). The recently locking plate is clinically more widely used due to its small size, low rigidity, high elasticity, and biomechanical properties such as fixed initial angle and rotational stability. However, in severely comminuted complex type proximal metaphyseal humerus fractures, the use of locking plate alone does not provide stable fixation, leading to complications such as varus collapse, anterior-posterior angulation, screw cutout, nonunion, malunion, and metal failure. Therefore, a more robust and enhanced fixation method, the dual plating technique using the locking compression plate (Proximal Humeral Internal Locking System and Variable Angle Locking Compression Plate) was developed. PMID:24813097

  12. Early fracture of a bioabsorbable tibial interference screw after ACL reconstruction with subsequent chondral injury.

    PubMed

    Hall, Michael P; Hergan, David M; Sherman, Orrin H

    2009-03-01

    Graft fixation in anterior cruciate ligament (ACL) reconstruction is commonly performed with bioabsorbable devices. This article presents a case of a broken bioabsorbable tibial interference screw (Gentle Threads; Biomet, Warsaw, Indiana) that presented as an intra-articular loose body 4 months after ACL reconstruction with posterior tibialis tendon allograft. A 19-year-old man presented with symptoms of pain and catching for 1 week but reported no history of trauma. The broken screw tip was identified on magnetic resonance imaging examination, and the remaining screw appeared to be overinserted into the tibia. During arthroscopic removal, a 10-mm screw tip was found in the lateral gutter. The ACL graft was found to be well fixed, but small areas of chondral damage were found in the patellofemoral and medial compartment. The patient's symptoms resolved postoperatively. To our knowledge, this is the earliest report of a broken bioabsorbable interference screw and only the second report of subsequent chondral injury due to intra-articular migration. Although rare, late breakage and intra-articular migration of bioabsorbable interference screws should be considered during the postoperative evaluation of any patient with pain or mechanical symptoms, regardless of trauma. This case also supports the importance of both measurement of tibial tunnel length and inspection of the intercondylar notch following interference screw insertion. Orthopedic surgeons performing ACL reconstruction must be aware of this possible complication and its potential for devastating chondral injury. PMID:19309052

  13. Occipital condyle screw placement and occipitocervical instrumentation using three-dimensional image-guided navigation.

    PubMed

    Le, Tien V; Burkett, Clint; Ramos, Edwin; Uribe, Juan S

    2012-05-01

    Occipital condyle (OC) screws are an alternative cephalad fixation point in occipitocervical fusion. Safe placement of occipital, C1 lateral mass, and C2 pars screws have been described previously, but not OC screws. The craniocervical junction is complex, and a thorough understanding of the anatomy is needed. Three-dimensional (3D) image-guided navigation was used in six patients. There were no complications related to image-guided navigation during the placement of 12 OC screws and we found that this navigation can serve as a useful adjunct when placing an OC screw. Technical considerations of placing OC and C1 lateral mass screws are discussed with particular reference to patient positioning and the StealthStation® S7™ image-guided navigational platform (Medtronic, Minneapolis, MN, USA). The reference arc is attached to the head-clamp and faces forward. The optical camera and monitor are positioned at the head of the table for a direct, non-obstructed line-of-sight. To minimize intersegmental movement, the OC should not be drilled until all other screws have been placed. We conclude that 3D image-guided navigation is a useful adjunct that can be safely and effectively used for placement of instrumentation of the upper cervical spine including the OC. PMID:22356730

  14. Placement of C2 laminar screws using three-dimensional fluoroscopy-based image guidance

    PubMed Central

    Foy, Andrew B.

    2007-01-01

    The use of C2 laminar screws in posterior cervical fusion is a relatively new technique that provides rigid fixation of the axis with minimal risk to the vertebral artery. The techniques of C2 laminar screw placement described in the literature rely solely on anatomical landmarks to guide screw insertion. The authors report on their experience with placement of C2 laminar screws using three-dimensional (3D) fluoroscopy-based image-guidance in eight patients undergoing posterior cervical fusion. Overall, fifteen C2 laminar screws were placed. There were no complications in any of the patients. Average follow-up was 10 months (range 3–14 months). Postoperative computed tomographic (CT) scanning was available for seven patients allowing evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. The intraoperative planning function of the image-guided system allowed for 4-mm diameter screws to be placed in all cases. Using modified Odom’s criteria, excellent or good relief of preoperative symptoms was noted in all patients at final follow-up. PMID:18034268

  15. Is the Etiology of Pretibial Cyst Formation After Absorbable Interference Screw Use Related to a Foreign Body Reaction?

    Microsoft Academic Search

    Guillem Gonzalez-Lomas; Ryan T. Cassilly; Fabrizio Remotti; William N. Levine

    2011-01-01

    Background  Arthroscopically assisted anterior cruciate ligament reconstruction using a bioabsorbable tibial fixation screw is occasionally\\u000a complicated by pretibial cyst formation. The few case reports describing pretibial cyst formation noted several graft types\\u000a and fixation techniques, making it difficult to establish one etiology. Some literature suggests cysts form from communication\\u000a between the joint and pretibial area leading to extravasation of joint fluid,

  16. Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats.

    PubMed

    Agarwal, Rachit; González-García, Cristina; Torstrick, Brennan; Guldberg, Robert E; Salmerón-Sánchez, Manuel; García, Andrés J

    2015-09-01

    Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted ?5?1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings. PMID:26100343

  17. Histoplasma complement fixation

    MedlinePLUS

    Histoplasma complement fixation is a blood test that checks for infection due to a fungus called Histoplasma capsulatum ( H. ... for Histoplasma antibodies using a laboratory method called complement fixation. This technique checks if your body has ...

  18. Long-term results of pediculo-body fixation and posterolateral fusion for lumbar spondylolisthesis

    Microsoft Academic Search

    Antonino Zagra; Fabrizio Giudici; Leone Minoia; Andrea Saverio Corriero; Luigi Zagra

    2009-01-01

    Grob et al. (Eur Spine J 5:281–285, 1996) illustrated a new fixation technique in inveterate cases of grade 2–3 spondylolisthesis (degenerative or spondylolytic):\\u000a a fusion without reduction of the spondylolisthesis. Fixation of the segment was achieved by two cancellous bone screws inserted\\u000a bilaterally through the pedicles of the lower vertebra into the body of the upper slipped vertebra. Since 1998

  19. A new technique for retaining double crowns on implants via custom-positioned vertical screws.

    PubMed

    Frisch, Eberhard; Ziebolz, Dirk; Ratka-Krüger, Petra; Rinke, Sven

    2014-01-01

    This report describes the use of custom-positioned vertical screws (CVS) to attach primary telescopic crowns to implant abutments. In a private practice setting, 37 patients with 40 double crown-retained implant overdentures (IODs) with a clearance fit (Marburg double crowns) were followed. All primary crowns on the 120 implant abutments were retained using CVS. After a mean followup period of 3.55 ± 1.37 years (range: 1.5 to 6.3 years), one abutment screwloosening incident was reported (incidence: 0.08%). No loosening of any of the screw-retained primary crowns occurred. CVS may represent a viable fixation concept for IODs. PMID:25390875

  20. Vertebral body compression fracture after percutaneous pedicle screw removal in a young man.

    PubMed

    Cappuccio, M; De Iure, F; Amendola, L; Martucci, A

    2014-11-23

    Hazards and potential complications associated with pedicle screw insertions have been reported. In contrast, complications due to implant removal are rarely described. An unreported case of acute vertebral body compression fracture following pedicle screw removal in a young man occurred during an episode of forceful coughing. Spinal implants need to be removed in cases of complications, pain or tissue irritation, and removal is mandatory when fixation involves L2 or the lower segments. Complications associated with spinal implant removal are rare but possible, and patients must be informed of this potential risk. PMID:25417175

  1. Biomechanical evaluation of a new fixation device for the thoracic spine.

    PubMed

    Hongo, Michio; Ilharreborde, Brice; Gay, Ralph E; Zhao, Chunfeng; Zhao, Kristin D; Berglund, Lawrence J; Zobitz, Mark; An, Kai-Nan

    2009-08-01

    The technology used in surgery for spinal deformity has progressed rapidly in recent years. Commonly used fixation techniques may include monofilament wires, sublaminar wires and cables, and pedicle screws. Unfortunately, neurological complications can occur with all of these, compromising the patients' health and quality of life. Recently, an alternative fixation technique using a metal clamp and polyester belt was developed to replace hooks and sublaminar wiring in scoliosis surgery. The goal of this study was to compare the pull-out strength of this new construct with sublaminar wiring, laminar hooks and pedicle screws. Forty thoracic vertebrae from five fresh frozen human thoracic spines (T5-12) were divided into five groups (8 per group), such that BMD values, pedicle diameter, and vertebral levels were equally distributed. They were then potted in polymethylmethacrylate and anchored with metal screws and polyethylene bands. One of five fixation methods was applied to the right side of the vertebra in each group: Pedicle screw, sublaminar belt with clamp, figure-8 belt with clamp, sublaminar wire, or laminar hook. Pull-out strength was then assessed using a custom jig in a servohydraulic tester. The mean failure load of the pedicle screw group was significantly larger than that of the figure-8 clamp (P = 0.001), sublaminar belt (0.0172), and sublaminar wire groups (P = 0.04) with no significant difference in pull-out strength between the latter three constructs. The most common mode of failure was the fracture of the pedicle. BMD was significantly correlated with failure load only in the figure-8 clamp and pedicle screw constructs. Only the pedicle screw had a statistically significant higher failure load than the sublaminar clamp. The sublaminar method of applying the belt and clamp device was superior to the figure-8 method. The sublaminar belt and clamp construct compared favorably to the traditional methods of sublaminar wires and laminar hooks, and should be considered as an alternative fixation device in the thoracic spine. PMID:19404687

  2. Mechanical testing of a device for subcutaneous internal anterior pelvic ring fixation versus external pelvic ring fixation

    PubMed Central

    2014-01-01

    Background Although useful in the emergency treatment of pelvic ring injuries, external fixation is associated with pin tract infections, the patient’s limited mobility and a restricted surgical accessibility to the lower abdomen. In this study, the mechanical stability of a subcutaneous internal anterior fixation (SIAF) system is investigated. Methods A standard external fixation and a SIAF system were tested on pairs of Polyoxymethylene testing cylinders using a universal testing machine. Each specimen was subjected to a total of 2000 consecutive cyclic loadings at 1 Hz with sinusoidal lateral compression/distraction (+/?50 N) and torque (+/? 0.5 Nm) loading alternating every 200 cycles. Translational and rotational stiffness were determined at 100, 300, 500, 700 and 900 cycles. Results There was no significant difference in translational stiffness between the SIAF and the standard external fixation when compared at 500 (p?=?.089), 700 (p?=?.081), and 900 (p?=?.266) cycles. Rotational stiffness observed for the SIAF was about 50 percent higher than the standard external fixation at 300 (p?=?.005), 500 (p?=?.020), and 900 (p?=?.005) cycles. No loosening or failure of the rod-pin/rod-screw interfaces was seen. Conclusions In comparison with the standard external fixation system, the tested device for subcutaneous internal anterior fixation (SIAF) in vitro has similar translational and superior rotational stiffness. PMID:24684828

  3. Occipital condyle to cervical spine fixation in the pediatric population.

    PubMed

    Kosnik-Infinger, Libby; Glazier, Steven S; Frankel, Bruce M

    2014-01-01

    Fixation at the craniovertebral junction (CVJ) is necessary in a variety of pediatric clinical scenarios. Traditionally an occipital bone to cervical fusion is preformed, which requires a large amount of hardware to be placed on the occiput of a child. If a patient has previously undergone a posterior fossa decompression or requires a decompression at the time of the fusion procedure, it can be difficult to anchor a plate to the occipital bone. The authors propose a technique that can be used when faced with this difficult challenge by using the occipital condyle as a point of fixation for the construct. Adult cadaveric and a limited number of case studies have been published using occipital condyle (C-0) fixation. This work was adapted for the pediatric population. Between 2009 and 2012, 4 children underwent occipital condyle to axial or subaxial spine fixation. One patient had previously undergone posterior fossa surgery for tumor resection, and 1 required decompression at the time of operation. Two patients underwent preoperative deformity reduction using traction. One child had a Chiari malformation Type I. Each procedure was performed using polyaxial screw-rod constructs with intraoperative neuronavigation supplemented by a custom navigational drill guide. Smooth-shanked 3.5-mm polyaxial screws, ranging in length from 26 to 32 mm, were placed into the occipital condyles. All patients successfully underwent occipital condyle to cervical spine fixation. In 3 patients the construct extended from C-0 to C-2, and in 1 from C-0 to T-2. Patients with preoperative halo stabilization were placed in a cervical collar postoperatively. There were no new postoperative neurological deficits or vascular injuries. Each patient underwent postoperative CT, demonstrating excellent screw placement and evidence of solid fusion. Occipital condyle fixation is an effective option in pediatric patients requiring occipitocervical fusion for treatment of deformity and/or instability at the CVJ. The use of intraoperative neuronavigation allows for safe placement of screws into C-0, especially when faced with a challenging patient in whom fixation to the occipital bone is not possible or is less than ideal. PMID:24206344

  4. Biomechanical analysis of different types of pedicle screw augmentation: a cadaveric and synthetic bone sample study of instrumented vertebral specimens.

    PubMed

    Chao, Kuo-Hua; Lai, Yu-Shu; Chen, Wen-Chuan; Chang, Chia-Ming; McClean, Colin J; Fan, Chang-Yuan; Chang, Chia-Hao; Lin, Leou-Chyr; Cheng, Cheng-Kung

    2013-10-01

    This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing. Mechanical pull-out strength, stiffness and energy-to-failure ratio were recorded for cement-augmented and non-cement-augmented screws. Synthetic bone simulating a human spinal bone with severe osteoporosis was used to measure the maximum extraction torque. The pull-out strength and stiffness-to-failure ratio of cement pre-filled and cement-injected screws were significantly higher than the non-cement-augmented control group. However, the cement pre-filled and cement-injected groups did not differ significantly across these values (p=0.07). The cement pre-filled group had the highest failure pull-out energy, approximately 2.8 times greater than that of the cement-injected (p<0.001), and approximately 11.5 times greater than that of the control groups (p<0.001). In the axial pull-out test, the cement-injected group had a greater maximum extraction torque than the cement pre-filled group, but was statistically insignificant (p=0.17). The initial fixation strength of cannulated screws pre-filled with cement is similar to that of cannulated screws injected with cement through perforations. This comparable strength, along with the heightened pull-out energy and reduced extraction torque, indicates that pedicle screws pre-filled with cement are superior for bone fixation over pedicle screws injected with cement. PMID:23669371

  5. A comparison of stress distributions for different surgical procedures, screw dimensions and orientations for a Temporomandibular joint implant

    Microsoft Academic Search

    Amit Roy Chowdhury; Ajay Kashi; Subrata Saha

    2011-01-01

    Finite element analysis is a useful analytical tool for the design of biomedical implants. The aim of this study was to investigate the behavior of temporomandibular joint implants with multiple design variables of the screws used for fixation of the implant. A commercially available implant with full mandible was analyzed using a finite element software package. The effects of different

  6. Methodological Underestimation of Oceanic Nitrogen Fixation Rates

    PubMed Central

    Mohr, Wiebke; Großkopf, Tobias; Wallace, Douglas W. R.; LaRoche, Julie

    2010-01-01

    The two commonly applied methods to assess dinitrogen (N2) fixation rates are the 15N2-tracer addition and the acetylene reduction assay (ARA). Discrepancies between the two methods as well as inconsistencies between N2 fixation rates and biomass/growth rates in culture experiments have been attributed to variable excretion of recently fixed N2. Here we demonstrate that the 15N2-tracer addition method underestimates N2 fixation rates significantly when the 15N2 tracer is introduced as a gas bubble. The injected 15N2 gas bubble does not attain equilibrium with the surrounding water leading to a 15N2 concentration lower than assumed by the method used to calculate 15N2-fixation rates. The resulting magnitude of underestimation varies with the incubation time, to a lesser extent on the amount of injected gas and is sensitive to the timing of the bubble injection relative to diel N2 fixation patterns. Here, we propose and test a modified 15N2 tracer method based on the addition of 15N2-enriched seawater that provides an instantaneous, constant enrichment and allows more accurate calculation of N2 fixation rates for both field and laboratory studies. We hypothesise that application of N2 fixation measurements using this modified method will significantly reduce the apparent imbalances in the oceanic fixed-nitrogen budget. PMID:20838446

  7. Carbon consequences of a nitrogen fixation feedback

    NASA Astrophysics Data System (ADS)

    Levy, J.; Medvigy, D.; Hedin, L.; Batterman, S. A.; Xu, X.

    2014-12-01

    Tropical forests constitute a globally important carbon sink but it is unclear how their productivity and carbon storage depend upon nutrients. There is increasing evidence of an ecosystem carbon-nitrogen feedback mechanism, by which symbiotic dinitrogen (N2) fixing trees can provide the nitrogen needed to maintain high rates of forest biomass growth following disturbance. Field-based evaluation of this feedback is difficult, however, as the expected effects on forest carbon stores would emerge very slowly, over decades to centuries of ecological succession. Moreover, there is no known way to inhibit the fixation process in trees without causing structural damage and perturbing the carbon cycle. Coupled land biogeochemistry-vegetation models offer a way to examine the role of feedbacks that unfold over successional time. However, it is unclear how the process of nitrogen fixation ought to be represented in models so that they can capture the potential effect of fixation on the long-term forest carbon sink. In this study, we integrate a newly developed individual-based model with field observations across Panamanian tropical forests to address: 1) whether N2 fixation enhances tropical forest carbon storage; 2) whether models must resolve fixation at the individual plant level to capture the fixation feedback; and 3) whether fixation interacts with plant functional types (i.e., early, mid, vs. late succession) to determine the carbon sink? We find that forests that have fixation recover faster and store more carbon in the long term than forests without fixation. This results in 94-118% more plant carbon stored by 30 years and an additional 13 tons C ha -1 stored over 300 years when compared to forests without fixation. Additionally, resolving fixation at the individual plant level is necessary to capture nitrogen dynamics over time and is particularly important for modeling succession and disturbance events. Finally, we find that the overall fixation effect is the result of two processes, the direct effect of the fixation on carbon accumulation and the indirect effect of fixation on the successional plant functional type sequence.

  8. Lateral mass fixation in subaxial cervical spine: anatomic review.

    PubMed

    Mohamed, Elrahmany; Ihab, Zidan; Moaz, Anwar; Ayman, Nabawi; Haitham, Abo-Elw

    2012-03-01

    Introduction?The cervical spine is a highly mobile segment of the spinal column, liable to a variety of diseases and susceptible to trauma. It is a complex region where many vital structures lie in close proximity. Lateral mass screw fixation has become the method of choice in stabilizing subaxial cervical spine among other posterior cervical fixation techniques whenever the posterior elements are absent or compromised. Objective?This study examined cervical specimens of cadavers and cervical computed tomography (CT) scans to minimize as much as possible complications of cervical lateral mass screw placement such as vertebral artery or nerve root injuries, facet joint violations, or inadequate placement. Methods?Forty normal cervical CT scans, obtained from the emergency unit as part of the trauma workup, were included in this study plus 10 cervical cadaveric specimens obtained from the Alexandria Neuro-anatomy laboratory. There were three fixed parameters for screw insertion in this study. First, the point of screw insertion was the midpoint of the lateral mass; it was the crossing point between the sagittal and axial planes of the posterior cortex of the lateral mass. Second, the direction of the screw in the craniocaudal plane was 30 degrees cranially to avoid facet joint penetration. Third, the exit point of the screw was located on the ventral cortex of the lateral mass just lateral to the root of the transverse process in the midaxial cut of each lateral mass, to make a sound bicortical fixation without injuring the vertebral artery or the nerve root. The selected screw trajectory in this study was the line drawn between the inlet and exit points. The depth and width of the lateral mass of the cervical vertebrae from C3 to C7 were measured as well as the angle of screw trajectory from the sagittal plane. All these measures were applied on the cadaveric specimens to make sure that no injury to the vertebral artery, nerve root, or facet joint occurred. Results?As regards the collected measurements of the lateral mass of all subaxial cervical vertebrae, the study revealed that the average depth of the lateral mass was 12.83?±?1.28 mm. The average width of the lateral mass was 11.92?±?0.96 mm. The average divergent angle of bicortical screw insertion without injury to the vertebral artery or the nerve root was 19.51?±?1.83 degrees. As regard the cadaveric specimens, based on all the collected measurements taken from the CT scans, there was no reported injury to the vertebral arteries or nerve roots or penetration to the facet joints. Conclusion?Lateral mass fixation can be applied easily and safely for all levels of subaxial cervical spine from C3 to C6 with the following parameters: (1) the point of entry is the midpoint of the lateral mass; (2) the screw trajectory is directed 30 degrees cranially and 20 degrees laterally; (3) the screw length is 13 to 15 mm. PMID:24353945

  9. Soft Tissue Tendon Graft Fixation in Serially Dilated or Extraction-Drilled Tibial TunnelsA Porcine Model Study Using High-Resolution Quantitative Computerized Tomography

    Microsoft Academic Search

    Brad S. Dunkin; John Nyland; Andrew R. Duffee; Jeffrey A. Brunelli; Robert Burden; David Caborn

    2007-01-01

    Background: Tibial tunnel preparation may contribute to improved soft tissue graft fixation.Hypothesis: Step dilation produces greater tunnel wall bone volume than does extraction drilling and increases fixation strength. Bioabsorbable interference screw divergence decreases fixation strength, regardless of tunnel preparation method.Study Design: Controlled laboratory study.Methods: Twenty porcine tibias were divided into 2 groups of 10 with matching mean apparent bone mineral

  10. Ionising radiation during internal fixation of extracepsular neck of femur fractures

    Microsoft Academic Search

    P. V. Giannoudis; J. McGuigan; D. L. Shaw

    1998-01-01

    This study analyses the relationship between the level of experience of both surgeon and radiographer and the radiation dose administered in theatre, during fixation of extracapsular proximal femoral fractures. From the 63 dynamic hip screw procedures performed, 10 were done by Senior House Officers (SHOs), 10 by Consultants and 43 by Registrars, whereas Basic Radiographers were involved in all cases.

  11. Outcome After Open Reduction and Internal Fixation of Lisfranc Joint Injuries

    Microsoft Academic Search

    R. S. KUO; N. C. TEJWANI; C. W. DIGIOVANNI; S. K. HOLT; S. K. BENIRSCHKE; S. T. HANSEN; B. J. SANGEORZAN

    2000-01-01

    Background: Open reduction and internal fixation has been recommended as the treatment for most un- stable injuries of the Lisfranc (tarsometatarsal) joint. It has been thought that purely ligamentous injuries have a poor outcome despite such surgical management. Methods: We performed a retrospective study of patients who underwent open reduction and screw fixa- tion of a Lisfranc injury in a

  12. Direct pediculo-body fixation in cases of spondylolisthesis with advanced intervertebral disc degeneration

    Microsoft Academic Search

    D. Grob; T. Humke; J. Dvorak

    1996-01-01

    In inveterate cases of grade 2–3 spondylolisthesis (degenerative or spondylolytic), segmental mobility may be reduced by radiologically confirmed disc resorption. Fusion may be indicated in patients with persistent pain. A simple technique for fusion without reduction of the spondylolisthesis is presented. Fixation of the segment is achieved by two cancellous bone screws inserted bilaterally through the pedicles of the lower

  13. Computer-Assisted Percutaneous Scaphoid Fixation: Concepts and Evolution

    PubMed Central

    Smith, Erin J.; Ellis, Randy E.; Pichora, David R.

    2013-01-01

    Background?The treatment for undisplaced scaphoid waist fractures has evolved from conventional cast immobilization to percutaneous screw insertion. Percutaneous fixation reduces some of the risks of open surgery, but can be technically demanding and carries the risk of radiation exposure. Recently, computer-assisted percutaneous scaphoid fixation (CAPSF) has been gaining interest. Materials and Methods?Conventional percutaneous scaphoid fixation is performed under fluoroscopic guidance and involves insertion of a guide wire along the length of the scaphoid to facilitate placement of a cannulated screw. Adapting computer-assisted techniques for scaphoid fixation poses several unique challenges including patient tracking and registration. Results?To date, five groups have successfully implemented systems for CAPSF. These systems have implemented wrist immobilization strategies to resolve the issue of patient tracking and have developed unique guidance techniques incorporating 2D fluoroscope, cone-beam CT, and ultrasound, to circumvent patient-based registration. Conclusions?Computer-aided percutaneous pinning of scaphoid waist fractures can significantly reduce radiation exposure and has the potential to improve the accuracy of this procedure. This article reviews the rationale for, and the evolution of, CAPSF and describes the key principles of computer-assisted technology. PMID:24436833

  14. The role of the kneading paddle and the effects of screw revolution speed and water content on the preparation of solid dispersions using a twin-screw extruder.

    PubMed

    Nakamichi, Kouichi; Nakano, Tomio; Yasuura, Hiroyuki; Izumi, Shogo; Kawashima, Yoshiaki

    2002-07-25

    The twin-screw hot-melt extrusion process is useful for preparing solid dispersions which can improve the dissolution and absorption of drugs. The kneading paddle elements of the screws play an important role in changing the crystallinity and dissolution properties of a solid dispersion of kneaded nifedipine-hydroxypropylmethylcellulose phthalate (NP-HPMCP). After operating the machine, a small amount of kneaded material adhering to the screws was collected and its physicochemical properties examined. Samples from the kneading paddle with a twist angle of 60 degrees were transparent and exhibited super-saturation on dissolution testing. When the kneading paddle elements were detached from the screws and only the feed screw elements were operated, the physicochemical properties of the extruded material were significantly influenced by the operating conditions of the machine e.g. revolution rate of screws, and the amount of water added to the feed materials. Slow revolution of the screws and the addition of a suitable amount of water to the mixture increased the rate of drug dissolution, although no super-saturation occurred. As the kneading paddle elements can retain the mixture in the machine for a longer period under intense shear, desired solid dispersions can be prepared routinely irrespective of the operating conditions. Moreover, a capillary rheometer can be useful to predetermine the amount of water added and the temperature for the preparation of solid dispersions using a twin-screw extruder. PMID:12100848

  15. Expandable insert serves as screw anchor

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Expandable self-locking adapter secures components to panels having one accessible side. Mounting holes in the panels may not be threaded to accommodate screws, therefore, the adapter contains a female thread that will mate a mounting screw.

  16. Limiting the dimension of a screw-access hole with an interim screw-retained prosthesis.

    PubMed

    Wadhwani, Chandur; Chung, Kwok-Hung

    2015-06-01

    Fabricating an interim screw-retained prosthesis often involves obliteration of the abutment screw access site, which later must be exposed. This frequently results in excessive preparation of the screw access site with poor esthetics and a weaker restoration. The technique described expedites the process by locating the access site and limits the size of the screw access hole preparation. PMID:25858223

  17. Screw symmetry in columnar crystals

    E-print Network

    A. Mughal

    2013-06-12

    We show that the optimal packing of hard spheres in an infinitely long cylinder yields structures characterised by a screw symmetry. Each packing can be assembled by stacking a basic unit cell ad infinitum along the length of the cylinder with each subsequent unit cell rotated by the same twist angle with respect to the previous one. In this paper we quantitatively describe the nature of this screw operation for all such packings in the range 1 <= D/d <= 2.715 and also briefly discuss their helicity.

  18. Design of a head fixation device for experiments in behaving monkeys.

    PubMed

    Isoda, Masaki; Tsutsui, Ken-Ichiro; Katsuyama, Narumi; Naganuma, Tomoka; Saito, Naohiro; Furusawa, Yoshihito; Mushiake, Hajime; Taira, Masato; Tanji, Jun

    2005-02-15

    We have designed a new device for head fixation of behaving monkeys. The fixation device consists of a duralumin head ring mounted with four screw holders. It is firmly fixed to the animal's skull with four stainless steel screw pins. The head ring is then attached to a primate chair in any desirable position and angle using a set of adjustable plates. The device has been used for behavioral training that requires accurate gaze monitoring and for recording single-unit activity over a several-month period. The advantage of our device is that it is simple to use; it can be attached readily without major surgical procedures and it can be quickly removed when experiments are not running. This head fixation system is suitable for behavioral experiments and single-unit recording studies. It may also be applicable for studies on functional imaging of the macaque brain, by constructing it of non-magnetic materials. PMID:15661310

  19. The role of reduction and internal fixation of Lisfranc fracture–dislocations: a systematic review of the literature

    PubMed Central

    Stavlas, Panagiotis; Roberts, Craig S.; Xypnitos, Fragiskos N.

    2010-01-01

    A systematic review of the literature was performed in order to evaluate the role of reduction and internal fixation in the management of Lisfranc joint fracture–dislocations. Articles were extracted from the Pubmed database and the retrieved reports were included in the study only if pre-specified eligibility criteria were fulfilled. Eleven articles were eligible for the final analysis, reporting data for the management of 257 patients. Injuries of the first three metatarsal rays were treated by closed reduction and internal fixation with screws in 16.3% of the patients, open reduction and internal fixation with screws in 66.5% and open reduction and internal fixation with Kirschner wires (K-wires) in 17.1% of the patients. The preferred method for the stabilisation of the fourth and fifth metatarsal rays was K-wires. Screw-related complications were common and were reported in 16.1% of the cases. The mean American Orthopaedic Foot and Ankle Society midfoot score was 78.1 points. Post-traumatic radiographic arthritis was reported in 49.6% of the patients, but only in 7.8% of them it was severe enough to warrant an arthrodesis. We conclude that open reduction and internal fixation of the first three metatarsal rays with screws is a reliable method for the management of Lisfranc injuries. This can be complemented by K-wires application in the fourth and fifth metatarsal rays if needed. PMID:20683593

  20. An eigenproblem approach to classical screw theory

    Microsoft Academic Search

    Sandipan Bandyopadhyay; Ashitava Ghosal

    2009-01-01

    This paper presents a novel algebraic formulation of the central problem of screw theory, namely the determination of the principal screws of a given system. Using the algebra of dual numbers, it shows that the principal screws can be determined via the solution of a generalised eigenproblem of two real, symmetric matrices. This approach allows the study of the principal

  1. Some refinements of the theory of the viscous screw pump.

    NASA Technical Reports Server (NTRS)

    Elrod, H. G.

    1972-01-01

    Recently performed analysis for herringbone thrust bearings has been incorporated into the theory of the viscous screw pump for Newtonian fluids. In addition, certain earlier corrections for sidewall and channel curvature effects have been simplified. The result is a single, refined formula for the prediction of the pressure-flow relation for these pumps.

  2. A new adhesive technique for internal fixation in midfacial surgery

    PubMed Central

    Endres, Kira; Marx, Rudolf; Tinschert, Joachim; Wirtz, Dieter Christian; Stoll, Christian; Riediger, Dieter; Smeets, Ralf

    2008-01-01

    Background The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market. Methods The adhesive bonding strengths were measured using tension tests. For this, metal plates with 2.0 mm diameter screw holes were cemented with PMMA bone cement to cortical bovine bone samples from the femur diaphysis. The bone was conditioned with an amphiphilic bone bonding agent prior to cementing. The samples were stored for 1 to 42 days at 37 degrees C, either moist or completely submerged in an isotonic NaCl-solution, and then subjected to the tension tests. Results Without the bone bonding agent, the bonding strength was close to zero (0.2 MPa). Primary stability with bone bonding agent is considered to be at ca. 8 MPa. Moist storage over 42 days resulted in decreased adhesion forces of ca. 6 MPa. Wet storage resulted in relatively constant bonding strengths of ca. 8 MPa. Conclusion A new amphiphilic bone bonding agent was developed, which builds an optimizied interlayer between the hydrophilic bone surface and the hydrophobic PMMA bone cement and thus leads to adhesive bonding between them. Our in vitro investigations demonstrated the adhesive bonding of PMMA bone cement to cortical bone, which was also stable against hydrolysis. The newly developed adhesive fixing technique could be applied clinically when the fixation of osteosynthesis plates with screws is impossible. With the detected adhesion forces of ca. 6 to 8 MPa, it is assumed that the adhesive fixation system is able to secure bone fragments from the non-load bearing midfacial regions in their orthotopic positions until fracture consolidation is complete. PMID:18489785

  3. A screw propelling capsule robot

    Microsoft Academic Search

    Huajin Liang; Yisheng Guan; Zhiguang Xiao; Chao Hu; Zhiyong Liu

    2011-01-01

    This paper presents a novel approach to active capsule robot, traversing in a tubular and compliant environment containing solid-liquid mixture. One of the application fields is active capsule endoscopy intended to navigate inside the gastrointestinal tract for diagnosis and therapy. This robot is driven by a screw impeller, which converts rotation to axial motion in two ways: one is through

  4. Air-Lubricated Lead Screw

    NASA Technical Reports Server (NTRS)

    Perkins, G. S.

    1983-01-01

    Air lubricated lead screw and nut carefully machined to have closely matched closely fitting threads. Compressed air injected into two plenums encircle nut and flow through orifices to lubricate mating threads. Originally developed to position precisely interferometer retroreflector for airborne measurement of solar infrared radiation, device now has positioning accuracy of 0.25 micron.

  5. Recurrent Laryngeal Edema Imitating Angioedema Caused by Dislocated Screw after Anterior Spine Surgery

    PubMed Central

    Wójtowicz, Piotr; Szafarowski, Tomasz; Migacz, Ewa; Krzeski, Antoni

    2015-01-01

    The anterior cervical spine surgery is a common procedure to stabilize vertebrae damaged by various diseases. The plates and screws are usually used in the spine fixation. This kind of instrumentation may detach from the bones which is a rare but well-known complication. A 77-year-old male presented to the otorhinolaryngology department with throat pain, choking, and dysphagia. At first the angioedema was diagnosed and he was treated conservatively. The endoscopy revealed laryngeal edema, being more defined on the right side with right vocal fold paresis. CT scans showed the stabilizing plate with two screws attached tightly and the back-out of the third screw toward soft tissue of the neck. In the meantime, his condition deteriorated and he needed tracheotomy. In few days the surgical removal of the dislocated screw was performed successfully. Although two-month follow-up reported no obstruction of the larynx, the vocal folds paresis with gradual functional improvement was observed. Long-term complication of anterior spine surgery sometimes may suggest laryngeal angioedema at first. If the conservative treatment is ineffective and there is a history of anterior spine surgery, the clinicians should consider the displacement of the plate or screws in differential diagnosis. PMID:25755901

  6. Designs and Techniques That Improve the Pullout Strength of Pedicle Screws in Osteoporotic Vertebrae: Current Status

    PubMed Central

    Shea, Thomas M.; Laun, Jake; Gonzalez-Blohm, Sabrina A.; Doulgeris, James J.; Lee, William E.; Vrionis, Frank D.

    2014-01-01

    Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein. PMID:24724097

  7. Evaluation of unilateral cage-instrumented fixation for lumbar spine

    PubMed Central

    2010-01-01

    Background To investigate how unilateral cage-instrumented posterior lumbar interbody fusion (PLIF) affects the three-dimensional flexibility in degenerative disc disease by comparing the biomechanical characteristics of unilateral and bilateral cage-instrumented PLIF. Methods Twelve motion segments in sheep lumbar spine specimens were tested for flexion, extension, axial rotation, and lateral bending by nondestructive flexibility test method using a nonconstrained testing apparatus. The specimens were divided into two equal groups. Group 1 received unilateral procedures while group 2 received bilateral procedures. Laminectomy, facectomy, discectomy, cage insertion and transpedicle screw insertion were performed sequentially after testing the intact status. Changes in range of motion (ROM) and neutral zone (NZ) were compared between unilateral and bilateral cage-instrumented PLIF. Results Both ROM and NZ, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF, transpedicle screw insertion procedure did not revealed a significant difference between flexion-extension, lateral bending and axial rotation direction except the ROM in the axial rotation. The bilateral group's ROM (-1.7 ± 0. 8) of axial rotation was decreased significantly after transpedicle screw insertion procedure in comparison with the unilateral group (-0.2 ± 0.1). In the unilateral cage-instrumented PLIF group, the transpedicle screw insertion procedure did not demonstrate a significant difference between right and left side in the lateral bending and axial rotation direction. Conclusions Based on the results of this study, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF have similar stability after transpedicle screw fixation in the sheep spine model. The unilateral approach can substantially reduce exposure requirements. It also offers the biomechanics advantage of construction using anterior column support combined with pedicle screws just as the bilateral cage-instrumented group. The unpleasant effect of couple motion resulting from inherent asymmetry was absent in the unilateral group. PMID:21070626

  8. Modeling of wet gas compression in twin-screw multiphase pump

    E-print Network

    Xu, Jian

    2009-05-15

    Twin-screw multiphase pumps experience a severe decrease in efficiency, even the breakdown of pumping function, when operating under wet gas conditions. Additionally, field operations have revealed significant vibration and thermal issues which can...

  9. Causes and managements of postoperative complications after degenerative scoliosis treatments with internal fixation

    PubMed Central

    Yang, Yong-Hong; Zheng, Jie; Lou, Shu-Liang

    2014-01-01

    Objective: To investigate the causes and managements of early postoperative complications of degenerative scoliosis (DS) treated with internal pedicle screw fixation. Methods: From Jan 2000 to Apr 2013, 325 DS patients treated with internal pedicle screw fixation in our hospital were retrospectively involved. The categories, causes, managements and outcomes of early postoperative complications were statistically analyzed. Results: Early postoperative complications occurred in 10.76% of the patients including 16 cases of lower limb numb or pain, 6 cases of decreased lower limb sensitivity and motor functions, which accounted for 62.86% of all complications, followed by incision infections (4/35, 11.43%) and rare cases of cerebrospinal fluid leakage, cardiac and renal inadequacy, urinary system and pulmonary infections. The incidence of overall complications (19.79%, p = 0.001) and nerve injuries (11.46%, p = 0.000) were significantly higher in long-segment than in short-segment fixations. Improper screw implanting, over correction of scoliosis and insufficient blood supply of the spinal cord during operation were risk factors for early postoperative complications and most of them were cured by anti-infection medication, incision dressing change, nerve nourishment, adjusting the screws and anti-osteoporosis treatments within 6 months after surgery. Only three cases with severe nerve injury did not improve until the 6 months postoperative follow-up. Conclusions: Most of the postoperative complications in our DS patients disappeared within 6 months after surgery and more than half of complications were nerve injuries. PMID:25550945

  10. Safe Osteocutaneous Radial Forearm Flap Harvest with Prophylactic Internal Fixation

    PubMed Central

    Shnayder, Yelizaveta; Tsue, Terance T.; Toby, E. Bruce; Werle, Andreas H.; Girod, Douglas A.

    2011-01-01

    We studied the efficacy of prophylactic plate fixation technique and a modified harvest of the osteocutaneous radial forearm free flap (OCRFFF) to minimize the incidence of postoperative donor radius pathological fracture. We retrospectively studied of the first 70 consecutive patients undergoing OCRFFF harvest by the University of Kansas Head and Neck Microvascular Reconstruction Team. Mean follow-up was 13 months. One of two patients undergoing OCRFFF harvest without prophylactic fixation developed a pathological radius fracture. The 68 subsequent OCRFFF patients underwent prophylactic fixation of the donor radius, and none developed a symptomatic radius fracture. Five of 68 patients did have a radiographically visible fracture requiring no intervention. The plate fixation technique was further modified to exclude monocortical screws in the radius bone donor defect (subsequent 39 patients), without any further fractures detected. One patient required forearm hardware removal for an attritional extensor tendon tear. The described modified OCRFFF harvest and prophylactic plate fixation technique may eliminate postoperative pathological fracture of the donor radius. Donor morbidity is similar to that of the fasciocutaneous radial forearm free flap , affording safe use of OCRFFF in head and neck reconstruction. PMID:22942941

  11. Safe osteocutaneous radial forearm flap harvest with prophylactic internal fixation.

    PubMed

    Shnayder, Yelizaveta; Tsue, Terance T; Toby, E Bruce; Werle, Andreas H; Girod, Douglas A

    2011-09-01

    We studied the efficacy of prophylactic plate fixation technique and a modified harvest of the osteocutaneous radial forearm free flap (OCRFFF) to minimize the incidence of postoperative donor radius pathological fracture. We retrospectively studied of the first 70 consecutive patients undergoing OCRFFF harvest by the University of Kansas Head and Neck Microvascular Reconstruction Team. Mean follow-up was 13 months. One of two patients undergoing OCRFFF harvest without prophylactic fixation developed a pathological radius fracture. The 68 subsequent OCRFFF patients underwent prophylactic fixation of the donor radius, and none developed a symptomatic radius fracture. Five of 68 patients did have a radiographically visible fracture requiring no intervention. The plate fixation technique was further modified to exclude monocortical screws in the radius bone donor defect (subsequent 39 patients), without any further fractures detected. One patient required forearm hardware removal for an attritional extensor tendon tear. The described modified OCRFFF harvest and prophylactic plate fixation technique may eliminate postoperative pathological fracture of the donor radius. Donor morbidity is similar to that of the fasciocutaneous radial forearm free flap , affording safe use of OCRFFF in head and neck reconstruction. PMID:22942941

  12. Assessment of sagittal split ramus osteotomy rigid internal fixation techniques using a finite element method.

    PubMed

    Albougha, S; Darwich, K; Darwich, M A; Albogha, M H

    2015-07-01

    In this study, finite element analysis (FEA) was used to evaluate nine rigid internal fixation techniques for sagittal split ramus osteotomy. To achieve this, a computed tomography (CT) scan of a healthy patient was obtained and used to generate the geometry of a half-mandible. The geometries of bicortical screws, miniplates, and monocortical screws were designed and combined with the mandible in nine models simulating various techniques. Four models used bicortical screws in various arrangements and four used miniplates of various designs. One model represented a hybrid technique. A load of 500N was applied to the posterior teeth and FEA was applied. The most stable techniques were the hybrid technique and a single straight miniplate, presenting the least displacement among all models. Bicortical screws, while presenting reasonable stability, showed high strain areas near the anterior ramus ridge, superoposterior to the screws, implying a risk of bone fracture in this area. On the other hand, the T-shaped and double Y-shaped miniplates were associated with high von Mises stresses that would impair their rigidity, especially where angles appeared in their designs. We recommend the use of a single straight miniplate because it provides sufficient stable fixation with minimal risks or disadvantages. PMID:25766461

  13. [The Herbert screw in pseudoarthrosis of the carpal scaphoid].

    PubMed

    Massart, P; Tazi, F; Finet, P; Bèzes, H

    1990-01-01

    For nearly three years, the authors have ensured scaphoid union by fixation with a double thread T.J. Herbert's screw. In these 25 cases a cancellous bone graft was used to fill the defect which would have left shortening of the scaphoid Twenty-two of the 25 cases, obtained rapid union, and 20 had a good or very good clinical result. One doubtful union and two cases of non-union occurred. One of these non-unions required revision. The main advantage of this procedure is to allow early mobilization of the wrist. This early is very appreciated by the patients who were immobilized several months by conservative treatment for their initial fracture. PMID:1703425

  14. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  15. Helical screw expander evaluation project

    NASA Astrophysics Data System (ADS)

    McKay, R.

    1982-03-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  16. Photographic fixative poisoning

    MedlinePLUS

    Photographic developer poisoning; Hydroquinone poisoning; Quinone poisoning; Sulfite poisoning ... Hydroquinones Quinones Sodium thiosulfate Sodium sulfite/bisulfite Boric acid Photographic fixative can also break down (decompose) to form sulfur ...

  17. Analysis of plastic deformation in cortical bone after insertion of coated and non-coated self-tapping orthopaedic screws.

    PubMed

    Koistinen, A P; Korhonen, H; Kiviranta, I; Kröger, H; Lappalainen, R

    2011-07-01

    Insertion of internal fracture fixation devices, such as screws, mechanically weakens the bone. Diamond-like carbon has outstanding tribology properties which may decrease the amount of damage in tissue. The purpose of this study was to investigate methods for quantification of cortical bone damage after orthopaedic bone screw insertion and to evaluate the effect of surface modification on tissue damage. In total, 48 stainless steel screws were inserted into cadaver bones. Half of the screws were coated with a smooth amorphous diamond coating. Geometrical data of the bones was determined by peripheral quantitative computed tomography. Thin sections of the bone samples were prepared after screw insertion, and histomorphometric evaluation of damage was performed on images obtained using light microscopy. Micro-computed tomography and scanning electron microscopy were also used to examine tissue damage. A positive correlation was found between tissue damage and the geometric properties of the bone. The age of the cadaver significantly affected the bone mineral density, as well as the damage perimeter and diameter of the screw hole. However, the expected positive effect of surface modification was probably obscured by large variations in the results and, thus, statistically significant differences were not found in this study. This can be explained by natural variability in bone tissue, which also made automated image analysis difficult. PMID:21870370

  18. Unifying screw geometry and matrix transformations

    SciTech Connect

    Samuel, A.E.; McAree, P.R.; Hunt, K.H. (Univ. of Melbourne, Parkville (Australia))

    1991-10-01

    Transformation matrices are widely used in robotics for kinematic analysis and trajectory planning. Screw geometry offers better geometric insight into such analyses. In this article the authors unify the two approaches through the use of invariant properties of orthogonal matrices under similarity transformations. They give a complete expression for the finite screw motion in terms of the entires of a 3 {times} 3 dual-number transformation matrix. Their analysis suggests that the finite screw is suitable for trajectory planning, and they develop a concise expression that gives the transformation matrix describing the displacement at each point along the path of the finite screw motion.

  19. Augmentation of unstable pertrochanteric fractures in the osteoporotic elderly patient: operative technique for 1 or 2 head screw systems.

    PubMed

    Dall'Oca, C; Maluta, T; Lavini, F; Micheloni, G M; Bondi, M; Magnan, B

    2014-01-01

    The incidence of proximal femoral fractures has substantially risen in the elderly. This rise has been attributed to an increase in their life span and the underlying poor bone stock and osteoporosis. One of the main reasons for revision surgery, reported to be as high as 19%, is the cut-out of the fixation device at the apex of the femoral head. Augmentation, facilitated by injecting cement (PMMA) around the apex of the proximal screw of the fixation device is considered a useful method with regards to the increased purchase between the bone and implant interface. The aim of this study is the description of the cement Augmentation operative technique for unstable osteoporotic pertrochanteric fractures with 1-2 femoral head screw devices. PMID:25409720

  20. Biomechanical comparison of mono-segment transpedicular fixation with short-segment fixation for treatment of thoracolumbar fractures: a finite element analysis.

    PubMed

    Xu, Guijun; Fu, Xin; Du, Changling; Ma, Jianxiong; Li, Zhijun; Tian, Peng; Zhang, Tao; Ma, Xinlong

    2014-10-01

    Mono-segment transpedicular fixation is a method for the treatment of certain types of thoracolumbar spinal fracture. Finite element models were constructed to evaluate the biomechanics of mono-segment transpedicular fixation of thoracolumbar fracture. Spinal motion (T10-L2) was scanned and used to establish the models. The superior half of the cortical bone of T12 was removed and the superior half of the cancellous bone of the T12 body was assigned the material properties of injured bone to mimic vertebral fracture. Transpedicular fixation of T11 and T12 was performed to produce a mono-segment fixation model; T11 and L1 were fixed to produce a short-segment fixation model. Motion differences between functional units and von Mises stress on the spine and implants were measured under axial compression, anterior bending, extensional bending, lateral bending and axial rotation. We found no significant difference between mono- and short-segment fixations in the motion of any functional unit. Stress on the T10/T11 nucleus pulposus and T10/T11 and L1/L2 annulus fibrosus increased significantly by about 75% on anterior bending, extensional bending and lateral bending. In the fracture model, stress was increased by 24% at the inferior endplate of T10 and by 43% at the superior endplate of L2. All increased stresses were reduced after fixation and lower stress was observed with mono-segment fixation. In summary, the biomechanics of mono-segment pedicle screw instrumentation was similar to that of conventional short-segment fixation. As a minimally invasive treatment, mono-segment fixation would be appropriate for the treatment of selected thoracolumbar spinal fractures. PMID:25267283

  1. Degradation behaviour of LAE442-based plate-screw-systems in an in vitro bone model.

    PubMed

    Wolters, Leonie; Besdo, Silke; Angrisani, Nina; Wriggers, Peter; Hering, Britta; Seitz, Jan-Marten; Reifenrath, Janin

    2015-04-01

    The use of absorbable implant materials for fixation after bone fracture helps to avoid a second surgery for implant removal and the risks and costs involved. Magnesium (Mg) is well known as a potential metallic material for degradable implants. The aim of the present in vitro study was to evaluate if degradable LAE442-based magnesium plate-screw-systems are suitable candidates for osteosynthesis implants in load-bearing bones. The corrosion behaviour was tested concerning the influence of different surface treatments, coatings and screw torques. Steel plates and screws of the same size served as control. Plates without special treatment screwed on up to a specified torque of 15cNm or 7cNm, NaOH treated plates (15cNm), magnesium fluoride coated plates (15cNm) and steel plates as control (15cNm) were examined in pH-buffered, temperature-controlled SBF solution for two weeks. The experimental results indicate that the LAE442 plates and screws coated with magnesium fluoride revealed a lower hydrogen evolution in SBF solution as well as a lower weight loss and volume decrease in ?-computed tomography (?CT). The nanoindentation and SEM/EDX measurements at several plate areas showed no significant differences. Summarized, the different screw torques did not affect the corrosion behaviour differently. Also the NaOH treatment seemed to have no essential influence on the degradation kinetics. The plates coated with magnesium fluoride showed a decreased corrosion rate. Hence, it is recommended to consider this coating for the next in vivo study. PMID:25686954

  2. In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III)

    Microsoft Academic Search

    Heiko Koller; Wolfgang Hitzl; Frank Acosta; Mark Tauber; Juliane Zenner; Herbert Resch; Yasutsugu Yukawa; Oliver Meier; Rene Schmidt; Michael Mayer

    2009-01-01

    Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization\\u000a strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly\\u000a in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced\\u000a the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its

  3. Magnetic Resonance Imaging of Bioabsorbable Polylactic Acid Interference Screws During the First 2 Years After Anterior Cruciate Ligament Reconstruction

    Microsoft Academic Search

    William H. Warden; Robert Friedman; Louis M. Teresi; Douglas W. Jackson

    1999-01-01

    Summary: Bioabsorbable screws composed of poly(L-lactic acid) (PLA) were used for graft fixation and studied prospectively with serial magnetic resonance imaging (MRI) scans at 8, 16, and 24 months after autogenous patellar tendon anterior cruciate ligament (ACL) reconstruction in 10 patients. Conventional spin echo, proton density , and T2-weighted double echo sequences were obtained, as well as T2-weighted fat-saturated fast

  4. Osteomyelitis after TightRope(®) fixation of the ankle syndesmosis: a case report and review of the literature.

    PubMed

    Hong, Choon Chiet; Lee, Wei Ting; Tan, Ken Jin

    2015-01-01

    Fixation of ankle syndesmosis injuries using the Ankle TightRope(®) has been gaining popularity. It has been shown to produce good results, facilitate early weightbearing, reduce the need for implant removal, and allow an earlier return to work and, possibly, a more anatomic syndesmotic reduction compared with screw fixation. However, its usage has been associated with complications such as soft tissue irritation, infection and wound breakdown, suture-button subsidence, and pathologic fracture from the screw tract. We describe a case of chronic osteomyelitis and suture-button migration associated with TightRope(®) fixation and a limited contact-dynamic compression plate for ankle syndesmosis disruption and lateral malleolus fracture. PMID:25451206

  5. Long stemmed total knee arthroplasty with interlocking screws: a computational bone adaptation study.

    PubMed

    Nyman, Jeffry S; Hazelwood, Scott J; Rodrigo, Juan J; Martin, R Bruce; Yeh, Oscar C

    2004-01-01

    The ability of an interlocking screw fixation technique to minimize bone loss related to stress shielding in the tibia was investigated and compared to the abilities of cement and press-fit fixation. Full bony ingrowth has been associated with greater stress shielding than partial ingrowth; therefore, the effect of intimate bonding of the stem to bone on subsequent bone loss was also studied. A damage- and disuse-based remodeling theory was coupled with a two-dimensional finite element model of the tibia to predict changes in bone remodeling following long stemmed total knee arthroplasty (TKA) for four different fixation techniques (cement, press-fit, interlock with bony ingrowth, and interlock without bony ingrowth). Remodeling changes commenced with the model state variables--bone area fraction, mechanical stimulus, damage, and remodeling activity--at steady-state values predicted by the intact tibia simulation. After TKA and irrespective of fixation technique, the model predicted elevated remodeling due to disuse, in which more bone was removed than replenished. In regions below the tibial tray and along the cortices, the interlocking stem with full bony ingrowth and the cemented stem caused the least amount of bone loss. An interlocking stem with a smooth, matted finish did not reduce the bone loss associated with interlocking fixation. PMID:14656659

  6. Bone ingrowth and stress shielding with a porous surface coated fracture fixation plate.

    PubMed

    Pilliar, R M; Cameron, H U; Binnington, A G; Szivek, J; Macnab, I

    1979-09-01

    The extent of bone remodelling under metal fixation plates attached to bone by (i) normal screw fixation and (ii) bone ingrowth into a porous metallic surface underlayer sintered to the metal plate was investigated. Extensive bone remodelling was observed under the integrally bonded porous surface layered plate. This remodelling could be attributed to the more extensive stress transfer from bone to metal plate because of the good bone-to-implant bonding. The importance of stress shielding with high stiffness implants is demonstrated. PMID:383716

  7. Migration pattern of cementless press fit cups in the presence of stabilizing screws in total hip arthroplasty

    PubMed Central

    2011-01-01

    The aim of this study was to evaluate the initial acetabular implant stability and late acetabular implant migration in press fit cups combined with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary total hip arthroplasty. One hundred and seven hips were available for follow-up after primary THA using a cementless, porous-coated acetabular component. A total of 631 standardized radiographs were analyzed digitally by the "single-film-x-ray-analysis" method (EBRA). One hundred 'and one (94.4%) acetabular components did not show significant migration of more than 1 mm. Six (5.6%) implants showed migration of more than 1 mm. Statistical analysis did not reveal preoperative patterns that would identify predictors for future migration. Our findings suggest that the use of screw fixation for cementless porous- coated acetabular components for primary THA does not prevent cup migration. PMID:21486725

  8. Improved screw theory using second order terms

    Microsoft Academic Search

    Jun Takamatsu; H. Kimura; Katsushi Ikeuchi

    2002-01-01

    The local displacement of an object is very useful for deciding grasp stability, generating trajectories, recognizing assembly tasks, and so on. To calculate this displacement, the screw theory is employed. It is equivalent to the first order Taylor expansion of the displacement. The screw theory is very convenient, because the displacement is formulated as simultaneous linear inequalities, and a powerful

  9. Nitrogen fixation and nitrogen fertilization of soybeans.

    PubMed

    Merbach, W; Jacob, H J

    1996-08-01

    Abstract In pot experiments with (15)N labelled soil and mineral (15)N, the influence of Bradyrhizobium (Rhizobium japonicum) inoculation and N fertilization on the symbiotic N(2) fixation and yield of soybeans [Glycine max (L.) Merill., cv. 'Fiskeby V'] was investigated. Symbiotic N(2) fixation only occured after inoculation with Bradyrhizobium. Considerable differences in efficiency of the bacterial preparations were observed. Shortly after flowering, the symbiotic nitrogen fixation was finished and, subsequently, soybeans took up considerable N amounts from the soil. N fertilization at seeding suppressed N(2) fixation of soybeans. In this case, the dry matter and nitrogen yield increased, because the loss of fixed nitrogen was overcompensated by the mineral N uptake. During flowering of soybeans, the N(2) fixation was not affected by N supply, because this process was already terminated. The mineral N was additionally available to the plants and led to increased N amounts in plants. It was absorbed to a considerable degree by soybeans. The mineral N was translocated (partly, after intermediate storage in the vegetative organs) into the seeds thus increasing their yields. PMID:22088108

  10. Coexistence of fixation-off sensitivity and inverted fixation-off sensitivity in a female child with Panayiotopoulos syndrome: Video-electroencephalography documentation?

    PubMed Central

    Saadeldin, Imad Y.; Matlik, Hussein N.

    2015-01-01

    Fixation-off sensitivity (FOS) is a rare phenomenon elicited by elimination of central vision and fixation, which even in the presence of light induces occipital paroxysms or generalized paroxysmal discharges. It is most commonly encountered in patients with idiopathic childhood occipital epilepsies but may also be observed in cases of symptomatic focal and generalized epilepsies. We describe a female Emirati child with Panayiotopoulos syndrome who exhibited FOS in addition to the reverse phenomenon called “inverted fixation-off sensitivity,” in which the electroencephalographic discharges were suppressed by the absence of central vision or fixation and activated by central vision or fixation. PMID:26101745

  11. Twin screw granulation: steps in granule growth.

    PubMed

    Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2012-11-15

    The present work focuses on the study of the progression of granules in different compartments along the length of screws in a twin screw granulator (TSG). The effects of varying powder feed rate; liquid to solid ratio and viscosity of granulation liquid on properties of granules was studied. The bigger granules produced at the start of the process were found to change in terms of size, shape and strength along the screw length at all the conditions investigated. The granules became more spherical and their strength increased along the screw length. Tracer granules were also introduced in order to understand the role of kneading and conveying elements in the TSG. The kneading elements promoted consolidation and breakage while the conveying elements led to coalescence, breakage and some consolidation. The results presented here help to provide a qualitative and quantitative understanding of the twin screw granulation process. PMID:22960611

  12. Update: Biological Nitrogen Fixation.

    ERIC Educational Resources Information Center

    Wiseman, Alan; And Others

    1985-01-01

    Updates knowledge on nitrogen fixation, indicating that investigation of free-living nitrogen-fixing organisms is proving useful in understanding bacterial partners and is expected to lead to development of more effective symbioses. Specific areas considered include biochemistry/genetics, synthesis control, proteins and enzymes, symbiotic systems,…

  13. The Fixation of Nitrogen.

    ERIC Educational Resources Information Center

    Andrew, S. P. S.

    1978-01-01

    Discusses the fixation of atmospheric nitrogen in the form of ammonia as one of the foundations of modern chemical industry. The article describes ammonia production and synthesis, purifying the hydrogen-nitrogen mix, nitric acid production, and its commericial plant. (HM)

  14. Late migration of threaded wire (schanz screw) from right distal clavicle to the cervical spine.

    PubMed

    Tsai, Chun-Hao; Hsu, Horng-Chaung; Huan, Chun-Yin; Chen, Hsien-Te; Fong, Yi-Chin

    2009-01-01

    We report a 49-year-old man who had undergone osteosynthesis to treat right distal clavicular fracture with a threaded wire (Schanz screw). The wire could not be removed due to its firm fixation within the bone. Eight years later, migration of the broken wire to the right 7th cervical vertebra punctured the lamina, with no spinal cord injury noted. The threaded wire was extracted from the C7 lamina emergently. No complication occurred after pin removal or during the 1-year postoperative follow-up. PMID:19181599

  15. Endoscopic transforaminal decompression, interbody fusion, and percutaneous pedicle screw implantation of the lumbar spine: A case series report

    PubMed Central

    Osman, Said G.

    2012-01-01

    Background On the basis of the experiences gained from conventional open spinal procedures, a long list of desirable objectives have emerged with the evolution of the lesser invasive spinal procedures. At the top of that list is the desire to minimize the trauma of surgery. The rest of the objectives, which include reductions of operating time, surgical blood loss, hospital stay, postoperative narcotic medication, convalescence, complication rates, and escalating health care costs, as well as the desire of elderly patients to continue rigorous physical activities, largely depend on the ability to minimize the trauma of surgery. The purpose of this study was to investigate the feasibility of the least invasive lumbar decompression, interbody fusion and percutaneous pedicle screw implantation, to minimize surgical trauma without compromising the quality of the treatment outcome, as well as to minimize risk of complications. Methods In this case series, 60 patients with diagnoses of degenerative disc disease, degenerative motion segments with stenosis, and spondylolisthesis, in whom nonoperative treatments failed, were treated with endoscopic transforaminal decompression and interbody fusion by 1 surgeon in 2 centers. The outcome measures were as follows: operating time, intraoperative blood loss, hospital stay, Visual Analogue Scale (VAS) scores for back and leg pain, scores on the Roland-Morris Disability Questionnaire, and postoperative imaging studies. A consecutive series of patients who met the treatment criteria completed VAS forms and Roland-Morris questionnaires preoperatively. Surgical procedures included arthroscopic decompression of the foramina and the discs; endplate preparation and implantation of allograft bone chips and bone morphogenetic protein 2 on absorbable collagen sponge into the disc space; and percutaneous implantation of pedicle screws. Postoperatively, the patients again completed the VAS forms and Roland-Morris questionnaires. Their charts were reviewed for office notes, operative notes, hospital stay, medications, and imaging studies. The latest X-ray and computed tomography scan films were reviewed and analyzed. Patients were followed up for a minimum of 6 months. The literature was reviewed for comparison of outcomes. Results Sixty patients met the inclusion criteria. The mean age was 52.8 years. The duration of illness averaged 5 years. Follow-up ranged from 6 to 25 months, with a mean of 12 months. Preoperative diagnoses included degenerative disc disease, degenerative motion segments with stenosis, and spondylolisthesis. The mean time in the operating room was 2 hours 54 minutes. Estimated blood loss averaged 57.6 mL. The duration of the hospital stay averaged 2.6 days. Preoperative back pain and leg pain were significantly reduced (P < .005). Forty-seven imaging studies obtained at the last visit, including X-ray and computed tomography scans, showed solid fusion in 28 patients (59.6%), stable fixation in 17 (36.2%), and osteolysis around the pedicle screws in 2 (4.2%). All patients had improvement of motor function, whereas 2 patients complained of residual numbness. In addition, 8 patients (13%) complained of residual discomfort on extension of the lumbar spine. Two patients had pedicle screw–related complications requiring surgery. A review of the literature showed that endoscopic transforaminal decompression and interbody fusion performed better than open transforaminal lumbar interbody fusion/posterior lumbar interbody fusion, minimally invasive transforaminal lumbar interbody fusion, and extreme lateral lumbar interbody fusion, with regard to most parameters studied. Conclusions The endoscopic transforaminal lumbar decompression, interbody fusion, and percutaneous pedicle screw instrumentation consistently produced satisfactory results in all demographics. It performed better than the alternative procedures for most parameters studied. PMID:25694885

  16. External Fixation combined with Limited Internal Fixation versus Open Reduction Internal Fixation for Treating Ruedi-Allgower Type III Pilon Fractures

    PubMed Central

    Guo, Yongzhi; Tong, Liangyong; Li, Shaoguang; Liu, Zhi

    2015-01-01

    Background The optimal treatment of type III pilon fractures remains controversial. Hence, we performed this study to investigate whether open reduction and internal fixation (ORIF) is superior to external fixations combined with limited internal fixations (EFLIF). Material/Methods From January 2012 to October 2013, a total of 78 patients were included. Twenty-six patients underwent EFLIF and 52 patients underwent ORIF. All subjects were followed up at 1, 3, 6, and 12 months postoperatively. All outcomes and complications were recorded. Results No statistical differences were observed in Mazur score or ROM between the 2 groups. There were significant differences between the 2 groups in hospital stay (P<0.001), reduction results (P=0.019), screw loosening (P=0.025), and traumatic arthritis (P=0.037). Conclusions Similar functional outcomes were achieved in EFLIF and ORIF groups. Due to several limitations of this study, a well-designed randomized controlled trial involving more patients and long-term follow-up is needed to find an optimal treatment protocol. PMID:26050786

  17. External Fixation combined with Limited Internal Fixation versus Open Reduction Internal Fixation for Treating Ruedi-Allgower Type III Pilon Fractures.

    PubMed

    Guo, Yongzhi; Tong, Liangyong; Li, Shaoguang; Liu, Zhi

    2015-01-01

    BACKGROUND The optimal treatment of type III pilon fractures remains controversial. Hence, we performed this study to investigate whether open reduction and internal fixation (ORIF) is superior to external fixations combined with limited internal fixations (EFLIF). MATERIAL AND METHODS From January 2012 to October 2013, a total of 78 patients were included. Twenty-six patients underwent EFLIF and 52 patients underwent ORIF. All subjects were followed up at 1, 3, 6, and 12 months postoperatively. All outcomes and complications were recorded. RESULTS No statistical differences were observed in Mazur score or ROM between the 2 groups. There were significant differences between the 2 groups in hospital stay (P<0.001), reduction results (P=0.019), screw loosening (P=0.025), and traumatic arthritis (P=0.037). CONCLUSIONS Similar functional outcomes were achieved in EFLIF and ORIF groups. Due to several limitations of this study, a well-designed randomized controlled trial involving more patients and long-term follow-up is needed to find an optimal treatment protocol. PMID:26050786

  18. Biomechanical comparison of internal fixation techniques for the Akin osteotomy of the proximal phalanx.

    PubMed

    Chacon, Yolanda; Fallat, Lawrence M; Dau, Nathan; Bir, Cynthia

    2012-01-01

    The Akin osteotomy is performed at the proximal phalanx for correction of an abducted great toe in a hallux abducto valgus deformity. Several internal fixation techniques have been widely advocated; however, their respective stabilities have not been compared. A biomechanical analysis was performed comparing 5 commonly used fixation techniques for the Akin osteotomy to determine the strongest method in simulated weightbearing in sawbone models. An Akin osteotomy was uniformly performed on 25 sawbones and fixated with 5 different internal fixation types, including a 2-hole locking plate and locking screws, a heat-sensitive memory staple (8 mm × 8 mm), a 28-gauge monofilament wire, 2.7-mm bicortical screws, and crossed 0.062-in. Kirschner wires. The results of simulated weightbearing load to failure rates with an Instron compression device demonstrated the following mean load to failures: crossed Kirschner wire, 57.05 N; 2-hole locking plate, 36.49 N; monofilament wire, 35.69 N; heat-sensitive memory staple, 34.32 N; and 2.7-mm bicortical screw, 13.66 N. Statistical analysis demonstrated the crossed Kirschner wire technique performed significantly better than the other fixation techniques (p < .007); the 4 other techniques were found not to be significantly different statistically (p = .041) from each another. Our study results suggest a crossing Kirschner wire construct significantly increases the stability of the Akin osteotomy in a sawbone model. This might be clinically extrapolated in an effort to improve patient outcomes because these osteotomies can undergo nonunion and malunion, resulting in postoperative pain and swelling. PMID:22819001

  19. A geometrical introduction to screw theory

    NASA Astrophysics Data System (ADS)

    Minguzzi, E.

    2013-05-01

    This work introduces screw theory, a venerable but little known theory aimed at describing rigid body dynamics. This formulation of mechanics unifies in the concept of screw the translational and rotational degrees of freedom of the body. It captures a remarkable mathematical analogy between mechanical momenta and linear velocities, and between forces and angular velocities. For instance, it clarifies that angular velocities should be treated as applied vectors and that, under the composition of motions, they sum with the same rules of applied forces. This work provides a short and rigorous introduction to screw theory intended for an undergraduate and general readership.

  20. A geometrical introduction to screw theory

    E-print Network

    E. Minguzzi

    2012-11-20

    This work introduces screw theory, a venerable but yet little known theory aimed at describing rigid body dynamics. This formulation of mechanics unifies in the concept of screw the translational and rotational degrees of freedom of the body. It captures a remarkable mathematical analogy between mechanical momenta and linear velocities, and between forces and angular velocities. For instance, it clarifies that angular velocities should be treated as applied vectors and that, under the composition of motions, they sum with the same rules of applied forces. This work provides a short and rigorous introduction to screw theory intended to an undergraduate and general readership.

  1. Optical and Exciton Dynamical Properties of a Screw-Dislocation-Driven ZnO:Sn Microstructure.

    PubMed

    Dai, Jun; Lu, Junfeng; Wang, Fang; Guo, Jiyuan; Gu, Ning; Xu, Chunxiang

    2015-06-17

    Screw dislocation plays a critical role in crystal growth and significantly affects the carrier dynamics process of luminescent semiconductor materials. In this paper, we report a novel screw-dislocation-induced ZnO:Sn hillock microstructure. The detailed growth process and possible formation mechanism of screw dislocation are demonstrated. The temperature-dependent photoluminescence reveals the free exciton recombination emission mechanism of the ZnO:Sn hillock microstructure. By comparing time-resolved photoluminescence spectra with those of two other samples without screw dislocations, it is found that the screw dislocation in the ZnO:Sn microstructures effectively decreases the carrier lifetime. In addition, UV Fabry-Perot lasing action is observed from the ZnO:Sn hillock microstructure, and the numerical simulation of the standing wave pattern and light intensity distribution further confirm the Fabry-Perot lasing mechanism. Therefore, ZnO:Sn can be utilized as a UV laser gain medium, and its optical properties can be modulated by screw dislocation. PMID:26011860

  2. CARBON DIOXIDE FIXATION.

    SciTech Connect

    FUJITA,E.

    2000-01-12

    Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.

  3. Screw pull-out force is dependent on screw orientation in an anterior cervical plate construct.

    PubMed

    DiPaola, Christian P; Jacobson, Justin A; Awad, Hani; Conrad, Bryan P; Rechtine, Glenn R

    2007-07-01

    Two common justifications for orienting cervical screws in an angled direction is to increase pull-out strength and to allow use of longer screws. This concept is widely taught and has guided implant design. Fixed versus variable angle systems may offer strength advantages. The purpose of our study is to test the influence of screw orientation and plate design on the maximum screw pull-out load. Variable and fixed angle 4.0 x 15 mm and 4.0 x 13 mm self-tapping screws were used to affix a Medtronic Atlantis cervical plate to polyurethane foam bone samples (density 0.160/cm). This synthetic product is a model of osteoporotic cancellous bone. The fixed angle screws can only be placed at 12 degrees convergent to the midline and 12 degrees in the cephalad/caudal ("12 degrees up and in") direction. Three groups were tested: (1) all fixed angle screws, (2) variable angle, all screws 12 degrees up and in, (3) variable angle, all screws 90 degrees to the plate. Plate constructs were pulled off with an Instron DynaMight 8841 servohydrolic machine measuring for maximum screw pull-out force. There was no difference between group 1, fixed angle (288.4 +/- 37.7 N) (mean +/- SD) and 2, variable angle group (297.7 +/- 41.31 N P< or =0.73). There was a significant increase in maximum pull-out force to failure for the construct with all screws at 90 degrees (415.2+/-17.4 N) compared with all screws 12 degrees "up and in" (297.4 +/- 41.3 N, P< or =0.0016). Group 3 done with 13 mm screws, showed a trend toward better pull-out strength, compared to group 2 w/15 mm screws (345.2 +/- 20.5 vs. 297.4 +/- 41.3, P< or =0.06). In this plate pull-out model, screw orientation influences maximum force to failure. When all 4 screws are 90 degrees to the plate the construct has the greatest ability to resist pullout. Fixed angle designs show no advantage over variable angle. These findings are contrary to current teaching. PMID:17607102

  4. Internal fixation versus hemiarthroplasty versus total hip arthroplasty for displaced subcapital fractures of femur — 13 year results of a prospective randomised study

    Microsoft Academic Search

    Kasetti J. Ravikumar; Gavin Marsh

    2000-01-01

    In this prospective randomised trial we compare the mortality, morbidity and functional results of patients following each of the three principal methods of treatment for displaced subcapital fractures of the femur. Two hundred and ninety patients over the age of 65 years were included and randomly allocated to undergo closed reduction and internal fixation with a sliding compression screw plate

  5. Bicondylar tibial plateau fractures treated with fine-wire circular external fixation.

    PubMed

    Ferreira, N; Marais, L C

    2014-04-01

    Bicondylar tibial plateau fractures are serious injuries to a major weight-bearing joint. These injuries are often associated with severe soft tissue injuries that complicate surgical management. We reviewed 54 consecutive patients who sustained bicondylar tibial plateau fractures that were treated with limited open reduction and cannulated screw fixation combined with fine-wire circular external fixation. Forty-six patients met the inclusion criteria of this retrospective review. Eight patients were excluded because they did not complete a minimum of 1-year follow-up. Thirty-six patients had Schatzker type-VI, and ten patients had Schatzker type-V fractures. All fractures were united without loss of reduction; there were no incidences of wound complications, osteomyelitis or septic arthritis. The average Knee Society Clinical Rating Score was 81.6, translating to good clinical results. Minor pin track infection was the most common complication encountered. This review concludes that fine-wire circular external fixation, combined with limited open reduction and cannulated screw fixation, consistently produces good functional results without serious complications. PMID:24510395

  6. Elastically suspending the screw holes of a locked osteosynthesis plate can dampen impact loads.

    PubMed

    Capanni, Felix; Hansen, Kirk; Fitzpatrick, Daniel C; Madey, Steven M; Bottlang, Michael

    2015-06-01

    Impact damping by elastic fixation is a principal engineering strategy to increase the durability of load-bearing structures exposed to prolonged dynamic loading. This biomechanical study evaluated axial impact damping provided by a novel dynamic locking plate. In this design, locking screw holes are elastically suspended within a silicone envelope inside the locking plate. Axial impact damping was assessed for 3 distinct fixation constructs applied to bridge a 10-mm fracture gap of a femoral diaphysis surrogate: a standard locking plate, a dynamic locking plate, and an Ilizarov ring fixator. First, the 3 fixation constructs were characterized by determining their axial stiffness. Subsequently, constructs were subjected to a range of axial impact loads to quantify damping of force transmission. Compared with standard locked plating constructs, dynamic plating constructs were 58% less stiff (P < .01) and Ilizarov constructs were 88% less stiff (P < .01). Impact damping correlated inversely with construct stiffness. Compared with standard plating, dynamic plating constructs and Ilizarov constructs dampened the transmission of impact loads by up to 48% (P < .01) and 74% (P < .01), respectively. In conclusion, lower construct stiffness correlated with superior damping of axial impact loads. Dynamic locking plates provide significantly greater impact damping compared with standard locking plates. PMID:25642697

  7. Rotordynamics of Twin-Screw Pumps 

    E-print Network

    Aboel Hassan Muhammed, Ameen

    2013-02-26

    geometry, the circumferential pressure field around the screws is not balanced, resulting in net dynamic and static pressures applied on the rotors. The research work presented here aims at building and verifying a model to predict both: (1) the exciting...

  8. Rotordynamics of Twin-Screw Pumps

    E-print Network

    Aboel Hassan Muhammed, Ameen

    2013-02-26

    geometry, the circumferential pressure field around the screws is not balanced, resulting in net dynamic and static pressures applied on the rotors. The research work presented here aims at building and verifying a model to predict both: (1) the exciting...

  9. Cycling Losses During Screw Air Compressor Operation 

    E-print Network

    Maxwell, J. B.; Wheeler, G.; Bushnell, D.

    1995-01-01

    Air compressors use 10-13 % of a typical industrial facilities' total electricity. Because they often operate at part load, their part load efficiency significantly affects plant energy cost. An intensive study of screw air compressor part load...

  10. Semi-Empirical Screw Compressor Chiller Model

    E-print Network

    Nelson, I. C.; Culp, C.; Graves, R. D.

    Director, Energy Systems Laboratory College Station, TX USA Rhett D. Graves, P.E. Research Associate II, Department of Mechanical Engineering Mississippi State University Starkville, MS USA ABSTRACT A screw chiller model which is based on a first...

  11. Early tissue responses to zoledronate, locally delivered by bone screw, into a compromised cancellous bone site: a pilot study

    PubMed Central

    2014-01-01

    Background In fracture treatment, adequate fixation of implants is crucial to long-term clinical performance. Bisphosphonates (BP), potent inhibitors of osteoclastic bone resorption, are known to increase peri-implant bone mass and accelerate primary fixation. However, adverse effects are associated with systemic use of BPs. Thus, Zoledronic acid (ZOL) a potent BP was loaded on bone screws and evaluated in a local delivery model. Whilst mid- to long-term effects are already reported, early cellular events occurring at the implant/bone interface are not well described. The present study investigated early tissue responses to ZOL locally delivered, by bone screw, into a compromised cancellous bone site. Methods ZOL was immobilized on fibrinogen coated titanium screws. Using a bilateral approach, ZOL loaded test and non-loaded control screws were implanted into femoral condyle bone defects, created by an overdrilling technique. Histological analyses of the local tissue effects such as new bone formation and osteointegration were performed at days 1, 5 and 10. Results Histological evaluation of the five day ZOL group, demonstrated a higher osseous differentiation trend. At ten days an early influx of mesenchymal and osteoprogenitor cells was seen and a higher level of cellular proliferation and differentiation (p?screw contact and bone volume values within the defect tended to increase. Local drug release did not induce any adverse cellular effects. Conclusion This study indicates that local ZOL delivery into a compromised cancellous bone site actively supports peri-implant osteogenesis, positively affecting mesenchymal cells, at earlier time points than previously reported in the literature. PMID:24656151

  12. [Implant materials for the internal fixation of midfacial fractures].

    PubMed

    Stuck, B A; Heller, T

    2011-11-01

    The material used for osteosynthesis plays a crucial role in the management of facial fractures. Plates need to be flexible enough to be bent and should not be palpable through the skin, while ensuring stable fixation und adequate biocompatibility. Although stainless steel was initially the material of choice, titanium has become the standard material due to its superior biocompatibility. While the explantation of titanium plates and screws appears unnecessary in general, it should be considered in cases of dislocation, cosmetic concerns, pain and infection. Due to their limited initial stability and a potential increase in local complications, resorbable materials based on polymeric lactose are used with caution in midfacial fractures in adults. Our own retrospective study comparing the postoperative complications after fixation of lateral midfacial fractures with titanium and resorbable systems demonstrated a low complication rate for both systems (7-8%) and no statistically significant difference between the two. The appropriate material for fixation should be selected based on the localization and severity of the fracture, the experience of the surgeon as well as on the age and overall condition of the patient. PMID:22012485

  13. Absorbable biologically based internal fixation.

    PubMed

    Ibrahim, Ahmed M S; Koolen, Pieter G L; Kim, Kuylhee; Perrone, Gabe S; Kaplan, David L; Lin, Samuel J

    2015-01-01

    Absorbable devices for use in internal fixation have advanced over the years to become reliable and cost-effective alternatives to metallic hardware. In the past, biodegradable fixation involved a laborious implantation process, and induced osteolysis and inflammatory reactions. Modern iterations exhibit increased strength, smoother resorption, and lower rates of reactivity. A newer generation manufactured from silk has emerged that may address existing limitations and provide a greater range of fixation applications. PMID:25440418

  14. Displaced avulsion fractures of the posterior cruciate ligament: Treated by stellate steel plate fixation

    PubMed Central

    Li, Lijun; Tian, Wei

    2015-01-01

    Background: The open reduction with internal fixation is an effective approach for treatment of avulsion fracture of posterior cruciate ligament. The previously used internal fixation materials including hollow screws, absorbable screw, tension bands and sutures have great defects such as insufficient fixation strength, susceptibility to re-fracture, etc. Stellate steel plate is novel material for internal fixation which has unique gear-like structure design. We used stellate steel plate for treatment of displaced avulsion fractures of posterior cruciate ligament in this study. Materials and Methods: 14 patients (9 men, 5 women; aged, 19–35 years; mean age, 28 years) with displaced avulsion fractures of the tibial insertion of the posterior cruciate ligament were retrospectively analyzed between June 2009 and June 2011. The mean duration from injury to the operation was 8.3 days (range 6–15 days). All the patients were treated with open reduction and internal fixation of a stellate steel plate (DePuy, Raynham, MA 02767, USA). The Lysholm-Tegner knee function score criteria were used to analyze results. Results: The mean followup was 24.6 months (range 18–32 months). After 6 months, all the fractures healed and knee joint activity was normal, with no knee stiffness or instability. The Lysholm-Tegner scores were 97.1 ± 1.7 points at the final followup. Conclusion: Owing to its unique gear structure, the stellate steel plate design can effectively fix an avulsion fracture block and it is a simple operation with short postoperative rehabilitation time and firm fixation. PMID:26015605

  15. Basic study for ultrasound-based navigation for pedicle screw insertion using transmission and backscattered methods.

    PubMed

    Chen, Ziqiang; Wu, Bing; Zhai, Xiao; Bai, Yushu; Zhu, Xiaodong; Luo, Beier; Chen, Xiao; Li, Chao; Yang, Mingyuan; Xu, Kailiang; Liu, Chengcheng; Wang, Chuanfeng; Zhao, Yingchuan; Wei, Xianzhao; Chen, Kai; Yang, Wu; Ta, Dean; Li, Ming

    2015-01-01

    The purpose of this study was to understand the acoustic properties of human vertebral cancellous bone and to study the feasibility of ultrasound-based navigation for posterior pedicle screw fixation in spinal fusion surgery. Fourteen human vertebral specimens were disarticulated from seven un-embalmed cadavers (four males, three females, 73.14 ± 9.87 years, two specimens from each cadaver). Seven specimens were used to measure the transmission, including tests of attenuation and phase velocity, while the other seven specimens were used for backscattered measurements to inspect the depth of penetration and A-Mode signals. Five pairs of unfocused broadband ultrasonic transducers were used for the detection, with center frequencies of 0.5 MHz, 1 MHz, 1.5 MHz, 2.25 MHz, and 3.5 MHz. As a result, good and stable results were documented. With increased frequency, the attenuation increased (P<0.05), stability of the speed of sound improved (P<0.05), and penetration distance decreased (P>0.05). At about 0.6 cm away from the cortical bone, warning signals were easily observed from the backscattered measurements. In conclusion, the ultrasonic system proved to be an effective, moveable, and real-time imaging navigation system. However, how ultrasonic navigation will benefit pedicle screw insertion in spinal surgery needs to be determined. Therefore, ultrasound-guided pedicle screw implantation is theoretically effective and promising. PMID:25861053

  16. Nitrogen fixation apparatus

    DOEpatents

    Chen, Hao-Lin (Walnut Creek, CA)

    1984-01-01

    A method and apparatus for achieving nitrogen fixation includes a volumetric electric discharge chamber. The volumetric discharge chamber provides an even distribution of an electron beam, and enables the chamber to be maintained at a controlled energy to pressure (E/p) ratio. An E/p ratio of from 5 to 15 kV/atm of O.sub.2 /cm promotes the formation of vibrationally excited N.sub.2. Atomic oxygen interacts with vibrationally excited N.sub.2 at a much quicker rate than unexcited N.sub.2, greatly improving the rate at which NO is formed.

  17. A comparison of four tibial-fixation systems in hamstring-graft anterior ligament reconstruction.

    PubMed

    Robert, Henri; Bowen, Mark; Odry, Guillaume; Collette, Michel; Cassard, Xavier; Lanternier, Hubert; De Polignac, Thierry

    2015-02-01

    The aim of this study was to evaluate at time-zero four tibial fixations on four major criteria: the elongation and cyclic stiffness of the hamstring graft construct under cyclic loading, the yield load and pullout stiffness under load at failure. Four fixation systems were tested: the Delta screw, the WasherLoc, the TightRope Reverse and the tape locking screw on 32 tibiae of adult pigs using 32 pairs of human semitendinosus and gracilis tendons. Two tests were performed: cyclic tests using loads at 70-220 N, to measure the elongation at the end of the cycles, followed by load-to-failure testing to measure the yield load and the cyclic stiffness. The mean elongation was 1.23 mm for the TLS, 3.81 mm for the Delta, 3.59 mm for the WasherLoc and 3.91 mm for the TightRope. The mean yield loads and SD were 1,015 ± 129 N for the TLS, 844 ± 394 N for the Delta, 511 ± 95 N for the WasherLoc and 567 ± 112 N for the TightRope. The results showed the significant superiority of TLS and Delta over WasherLoc and tibial TightRope in regard to yield load. The results showed the significant superiority of TLS over the other fixations in regard to slippage. The TLS system and the Delta screw provide a better quality of primary fixation to the tibia, but further in vitro studies are needed. PMID:24816761

  18. Eighth international congress on nitrogen fixation

    SciTech Connect

    Not Available

    1990-01-01

    This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

  19. Navigation of Pedicle Screws in the Thoracic Spine with a New Electromagnetic Navigation System: A Human Cadaver Study

    PubMed Central

    Hahn, Patrick; Oezdemir, Semih; Komp, Martin; Giannakopoulos, Athanasios; Kasch, Richard; Merk, Harry; Liermann, Dieter; Godolias, Georgios; Ruetten, Sebastian

    2015-01-01

    Introduction. Posterior stabilization of the spine is a standard procedure in spinal surgery. In addition to the standard techniques, several new techniques have been developed. The objective of this cadaveric study was to examine the accuracy of a new electromagnetic navigation system for instrumentation of pedicle screws in the spine. Material and Method. Forty-eight pedicle screws were inserted in the thoracic spine of human cadavers using EMF navigation and instruments developed especially for electromagnetic navigation. The screw position was assessed postoperatively by a CT scan. Results. The screws were classified into 3 groups: grade 1 = ideal position; grade 2 = cortical penetration <2?mm; grade 3 = cortical penetration ?2?mm. The initial evaluation of the system showed satisfied positioning for the thoracic spine; 37 of 48 screws (77.1%, 95% confidence interval [62.7%, 88%]) were classified as group 1 or 2. Discussion. The screw placement was satisfactory. The initial results show that there is room for improvement with some changes needed. The ease of use and short setup times should be pointed out. Instrumentation is achieved without restricting the operator's mobility during navigation. Conclusion. The results indicate a good placement technique for pedicle screws. Big advantages are the easy handling of the system. PMID:25759814

  20. Biomechanical analysis of acetabular revision constructs: is pelvic discontinuity best treated with bicolumnar or traditional unicolumnar fixation?

    PubMed

    Gililland, Jeremy M; Anderson, Lucas A; Henninger, Heath B; Kubiak, Erik N; Peters, Christopher L

    2013-01-01

    Pelvic discontinuity in revision total hip arthroplasty presents problems with component fixation and union. A construct was proposed based on bicolumnar fixation for transverse acetabular fractures. Each of 3 reconstructions was performed on 6 composite hemipelvises: (1) a cup-cage construct, (2) a posterior column plate construct, and (3) a bicolumnar construct (no. 2 plus an antegrade 4.5-mm anterior column screw). Bone-cup interface motions were measured, whereas cyclical loads were applied in both walking and descending stair simulations. The bicolumnar construct provided the most stable construct. Descending stair mode yielded more significant differences between constructs. The bicolumnar construct provided improved component stability. Placing an antegrade anterior column screw through a posterior approach is a novel method of providing anterior column support in this setting. PMID:22595181

  1. [3-D finite element modeling of internal fixation of mandibular mental fracture and the design of boundary constraints].

    PubMed

    Luo, Xiaohui; Wang, Hang; Fan, Yubo

    2007-04-01

    This study was aimed to develop a 3-D finite element (3-D FE) model of the mental fractured mandible and design the boundary constrains. The CT images from a health volunteer were used as the original information and put into ANSYS program to build a 3-D FE model. The model of the miniplate and screw which were used for the internal fixation was established by Pro/E. The boundary constrains of different muscle loadings were used to simulate the 3 functional conditions of the mandible. A 3-D FE model of mental fractured mandible under the miniplate-screw internal fixation system was constructed. And by the boundary constraints, the 3 biting conditions were simulated and the model could serve as a foundation on which to analyze the biomechanical behavior of the fractured mandible. PMID:17591250

  2. Biomechanical in vitro evaluation of three stable internal fixation techniques used in sagittal osteotomy of the mandibular ramus: a study in sheep mandibles

    PubMed Central

    de OLIVERA, Leandro Benetti; SANT'ANA, Eduardo; MANZATO, Antonio José; GUERRA, Fábio Luis Bunemer; ARNETT, G. William

    2012-01-01

    Among the osteotomies performed in orthognathic surgery, the sagittal osteotomy of the mandibular ramus (SOMR) is the most common, allowing a great range of movements and stable internal fixation (SIF), therefore eliminating the need of maxillomandibular block in the postoperative period. Objectives: The purpose of this study was to evaluate the biomechanical resistance of three national systems used for SIF in SOMR in sheep mandibles. Material and methods: The study was performed in 30 sheep hemi-mandibles randomly divided into 3 experimental groups, each containing 10 hemi-mandibles. The samples were measured to avoid discrepancies and then subjected to SOMR with 5-mm advancement. In group I, 2.0x12 mm screws were used for fixation, inserted in an inverted "L" pattern (inverted "L" group). In group II, fixation was performed with two 2.0x12 mm screws, positioned in a linear pattern and a 4-hole straight miniplate and four 2.0x6.0 mm monocortical screws (hybrid group). In group III, fixation was performed with two 4-hole straight miniplates and eight 2.0x6.0 mm monocortical screws (mini plate group). All materials used for SIF were supplied by Osteosin - SIN. The hemimandibles were subjected to vertical linear load test by Kratos K2000MP mechanical testing unit for loading registration and displacement. Results: All groups showed similar resistance during mechanical test for loading and displacement, with no statistically significant differences between groups according to analysis of variance. Conclusion: These results indicate that the three techniques of fixation are equally effective for clinical fixation of SOMR. PMID:23032203

  3. DINITROGEN FIXATION IN ILLINOIS BUNDLEFLOWER

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMillan] is a warm-season perennial forage legume that may serve as a pulse crop. Its productivity is influenced by its N2 fixation capability. Our objective was to estimate symbiotic N2 fixation of three Illinois bundleflower accessions from ...

  4. Overdesign of external fixation systems.

    PubMed

    Habboushe, M P

    1992-05-01

    This article reviews 850 cases of open fractures of the extremities caused by high velocity missiles and shell fragments, and treated by two varieties of external fixation devices. If a protocol for grading the severity of injury is followed, the results encourage avoiding sophisticated, expensive, and overdesigned external fixation systems. PMID:1589355

  5. Twin screw wet granulation: Binder delivery.

    PubMed

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration. PMID:25869451

  6. Maxillary sinus perforation by orthodontic anchor screws.

    PubMed

    Motoyoshi, Mitsuru; Sanuki-Suzuki, Rina; Uchida, Yasuki; Saiki, Akari; Shimizu, Noriyoshi

    2015-01-01

    To facilitate safe placement of orthodontic anchor screws (miniscrews), we investigated the frequency of maxillary sinus perforation after screw placement and the effect of sinus perforation on screw stability. Maxillary sinus perforations involving 82 miniscrews (diameter, 1.6 mm; length, 8 mm) were evaluated using cone-beam computed tomography. All miniscrews were placed in maxillary alveolar bone between the second premolar and first molar for anchorage for anterior retraction in patients undergoing first premolar extraction. The placement torque and screw mobility of each implant were determined using a torque tester and a Periotest device, and variability in these values in relation to sinus perforation was evaluated. Eight of the 82 miniscrews perforated the maxillary sinus. There was no case of sinusitis in patients with miniscrew perforation and no significant difference in screw mobility or placement torque between perforating and non-perforating miniscrews. The sinus floor was significantly thinner in perforated cases than in non-perforated cases. A sinus floor thickness of 6.0 mm or more is recommended in order to avoid miniscrew perforation of the maxillary sinus. (J Oral Sci 57, 95-100, 2015). PMID:26062857

  7. Surgical rib fixation - technical aspects.

    PubMed

    Marasco, Silvana; Saxena, Pankaj

    2015-05-01

    Surgical rib fixation (SRF) for severe rib fracture injuries is increasingly becoming an accepted treatment modality. There is now adequate evidence in randomised controlled trials that rib fixation in flail chest patients reduces ventilator times, intensive care stay and costs of treatment in ventilator dependent patients [1-3]. Despite this, rib fixation has not become standard of care for these patients and remains a treatment modality practised by few centres, usually those with large trauma loads who see high volumes of severe rib fracture injury patients. The purpose of this article is to outline the available prostheses, indications, operative planning and techniques of rib fixation. Surgical approaches to rib fractures in anterior, lateral and posterior positions are described as are the use of currently available cortical and medullary fixation prostheses. PMID:25624272

  8. The stability of fixation of proximal femoral fractures: a radiostereometric analysis.

    PubMed

    van Embden, D; Stollenwerck, G A N L; Koster, L A; Kaptein, B L; Nelissen, R G H H; Schipper, I B

    2015-03-01

    The aim of this study was to quantify the stability of fracture-implant complex in fractures after fixation. A total of 15 patients with an undisplaced fracture of the femoral neck, treated with either a dynamic hip screw or three cannulated hip screws, and 16 patients with an AO31-A2 trochanteric fracture treated with a dynamic hip screw or a Gamma Nail, were included. Radiostereometric analysis was used at six weeks, four months and 12 months post-operatively to evaluate shortening and rotation. Migration could be assessed in ten patients with a fracture of the femoral neck and seven with a trochanteric fracture. By four months post-operatively, a mean shortening of 5.4 mm (-0.04 to 16.1) had occurred in the fracture of the femoral neck group and 5.0 mm (-0.13 to 12.9) in the trochanteric fracture group. A wide range of rotation occurred in both types of fracture. Right-sided trochanteric fractures seem more rotationally stable than left-sided fractures. This prospective study shows that migration at the fracture site occurs continuously during the first four post-operative months, after which stabilisation occurs. This information may allow the early recognition of patients at risk of failure of fixation. PMID:25737524

  9. A testing technique allowing cyclic application of axial, bending, and torque loads to fracture plates to examine screw loosening.

    PubMed

    Szivek, J A; Yapp, R A

    1989-04-01

    Orthopaedic internal fracture fixation plates are subjected to combined axial, bending, and torsional loads in vivo which can cause screw loosening and implant failure. This paper outlines a relatively simple technique which allows controlled application of combined axial, bending, and torsional loading to examine the loosening rate of cortical screws used to attach these plates. Fiber reinforced polycarbonate rods with a tensile strength similar to that of cortical bone were cut at half their length to simulate fractured tibii. These were compression plated using a standardized technique and placed in a loading fixture. Joint loads at the knee determined from force plate analysis and statics were applied to a plated fixture during testing. The design of the fixture allowed adjustment of the proportion of bending and torsional loads applied to the test samples. It also allowed a reproducible means of applying a predetermined axial, bending, and torsional load. Screw loosening following cyclical loading was evaluated by measuring the amount of angular displacement required to retighten screws to a prescribed torque value. A torque wrench was modified to allow the measurement of these displacements. PMID:2722901

  10. Screw expander for light duty diesel engines

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

  11. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... “Warning: The safety and effectiveness of pedicle screw spinal systems have been established...requiring fusion with instrumentation. These conditions...pseudarthrosis). The safety and effectiveness of these...pedicle screw spinal systems should be...

  12. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... “Warning: The safety and effectiveness of pedicle screw spinal systems have been established...requiring fusion with instrumentation. These conditions...pseudarthrosis). The safety and effectiveness of these...pedicle screw spinal systems should be...

  13. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... “Warning: The safety and effectiveness of pedicle screw spinal systems have been established...requiring fusion with instrumentation. These conditions...pseudarthrosis). The safety and effectiveness of these...pedicle screw spinal systems should be...

  14. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... “Warning: The safety and effectiveness of pedicle screw spinal systems have been established...requiring fusion with instrumentation. These conditions...pseudarthrosis). The safety and effectiveness of these...pedicle screw spinal systems should be...

  15. KINEMATIC ANALYSIS OF LOWER MOBILITY COOPERATIVE ARMS BY SCREW THEORY

    E-print Network

    Paris-Sud XI, Université de

    KINEMATIC ANALYSIS OF LOWER MOBILITY COOPERATIVE ARMS BY SCREW THEORY Philip Long1 , St´ephane Caro.secondname}@irccyn.ec-nantes.fr Keywords: Cooperative Manipulators:Humanoid Robots: Screw theory Abstract: This paper studies the kinematic

  16. Decreased Fixation Stability of the Preferred Retinal Location in Juvenile Macular Degeneration

    PubMed Central

    Bethlehem, Richard A. I.; Dumoulin, Serge O.; Dalmaijer, Edwin S.; Smit, Miranda; Berendschot, Tos T. J. M.; Nijboer, Tanja C. W.; Van der Stigchel, Stefan

    2014-01-01

    Macular degeneration is the main cause for diminished visual acuity in the elderly. The juvenile form of macular degeneration has equally detrimental consequences on foveal vision. To compensate for loss of foveal vision most patients with macular degeneration adopt an eccentric preferred retinal location that takes over tasks normally performed by the healthy fovea. It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision. Here, we investigated whether the fixation characteristics of the preferred retinal locus resemble those of the healthy fovea. For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker. The fixation-offset paradigm measures release from fixation under different fixation conditions and has been shown useful to distinguish between foveal and non-foveal fixation. We measured eye-movements in nine healthy age-matched controls and five patients with juvenile macular degeneration. In addition, we performed a simulation with the same task in a group of five healthy controls. Our results show that the preferred retinal locus does not adopt a foveal type of fixation but instead drifts further away from its original fixation and has overall increased fixation instability. Furthermore, the fixation instability is most pronounced in low frequency eye-movements representing a slow drift from fixation. We argue that the increased fixation instability cannot be attributed to fixation under an unnatural angle. Instead, diminished visual acuity in the periphery causes reduced oculomotor control and results in increased fixation instability. PMID:24937090

  17. Lumbopelvic fusion with a new fixation technique in lumbosacral agenesis: three cases

    PubMed Central

    Akel, Ibrahim; Demirkiran, Halil Gokhan

    2011-01-01

    Purpose Patients with lumbosacral agenesis characteristically sit on their iliac wings with their torsos bent forward, which yields an increase in intra-abdominal pressure and, subsequently, negative effects on their diaphragm. The sacrum is not available as an anchor point for instrumentation. Dunn-McCarthy rods or Galveston fixations cannot be performed due to these limited anatomic properties. On the other hand, the absence of necessary bone mass for fusion anteriorly limits the fusion interventions to the posterior. Therefore, a secure and rigid fixation is essential to preclude the need for an external support. There are limited publications discussing different techniques due to the relatively rare incidence of the disease. We report the clinical and radiological results of a new technique applied to three patients in which previously recommended methods are modified. Methods Two 6-year-old female patients and one 5-year-old male patient with lumbosacral agenesis underwent posterior lumbopelvic instrumentation and fusion. Together with standard pedicle screw spinal instrumentation, pelvic fixation is obtained with a combination of supero-inferior directed rod and/or screw to overcome deforming forces created at the flexion–extension pivot points of the lumbopelvic junction. Autogenic anterior tibial cortical structural graft is used for laminopelvic bridging, and demineralized bone matrix is used for the augmentation of osteoinduction. A single leg hip spica is applied for 4 months to protect the fixation. Results Total correction yielded an aligned spine with a posture that allows for sitting on the ischial spines for all three patients. Solid fusion was observed to maintain this correction at the final follow-up. Conclusion The use of new-generation pediatric spinal instrumentation systems with a new technique without knee disarticulation provides a safe and effective fixation and fusion in lumbosacral agenesis. PMID:22295050

  18. Screw Systems, Singular Trajectories and DarbouxType Motions

    E-print Network

    Donelan, Peter

    Screw Systems, Singular Trajectories and Darboux­Type Motions M. W. Cocke and C. G. Gibson by the associated screw system. We present a classification of screw systems based on a Lie group representation body motions abound in theory and practice. The instantaneous centre of rotation for a continuous (or

  19. A Novel Pedicle Screw with Mobile Connection: A Pilot Study

    PubMed Central

    Oshima, Masashi; Ajiro, Yasumitsu; Uei, Hiroshi

    2014-01-01

    To prevent adjacent disc problems after spinal fusion, a pedicle screw with a mobile junction between the head and threaded shaft was newly developed. The threaded shaft of the screw has 10 degrees mobility in all directions, but its structure is to prevent abnormal translation and tilting. This screw was evaluated as follows: (1) endurance test: 106 times rotational stress was applied; (2) biological reactions: novel screws with a mobile head and conventional screws with a fixed head were inserted into the bilateral pedicles of the L3, L4, and L5 in two mini pigs with combination. Eight months after surgery, vertebral units with the screw rod constructs were collected. After CT scan, the soft and bony tissues around the screws were examined grossly and histologically. As a result, none of the screws broke during the endurance test stressing. The mean amount of abrasion wear was 0.0338?g. In the resected mini pig section, though zygapophyseal joints between fixed-head screws showed bony union, the amount of callus in the zygapophyseal joints connected with mobile-head screws was small, and joint space was confirmed by CT. No metalloses were noted around any of the screws. Novel screws were suggested to be highly durable and histologically safe. PMID:24724103

  20. Design and experimental evaluation of adjustable bone plates for mandibular fracture fixation.

    PubMed

    Cervantes, Thomas M; Slocum, Alexander H; Seldin, Edward B

    2012-01-01

    Conventional bone plates are commonly used for surgical mandibular fracture fixation. Improper alignment between bone segments, however, can result in malocclusion. Current methods of fixation require a surgeon to visually align segments of bone and affix a metal plate using bone screws, after which little can be done to adjust alignment. A method of adjusting fracture alignment after plate placement, without screw removal, presents an improvement over costly and risky revision surgery. A modified bone plate has been designed with a deformable section to give surgeons the ability to reduce misalignments at the fracture site. The mechanics of deformation for various adjustment mechanisms was explored analytically, numerically, and experimentally to ensure that the adjustable plate is comparable to conventional bone plates. A static force of 358.8 N is required to deform the adjustable bone plate, compared with predicted values of 351 N using numerical simulation and 362 N using a simple beam theory. Dynamic testing was performed to simulate in vivo loading conditions and evaluate load-capacity in both deformed and un-deformed bone plates. Results indicate that bending stiffness of a rectangular bone plate is 709 N/mm, compared with 174 N/mm for an octagonal plate and 176 N/mm for standard plates. Once deformed, the rectangular and octagonal plates had a stiffness of 323 N/mm and 228 N/mm, respectively. Un-deformed and deformed adjustable bone plates have efficacy in bone segment fixation and healing. PMID:22036033

  1. Bioabsorbable fixation of scaphoid fractures and non-unions; analysis of early clinical outcomes.

    PubMed

    Ya'ish, F; Bailey, C A; Kelly, C P; Craigen, M A

    2013-01-01

    The vast majority of devices used for internal fixation of the scaphoid are metallic. This two-center study aimed to report the results of scaphoid fixation using a cannulated, bioabsorbable device made from a hydroxyapatite and poly-L-lactide composite in 29 consecutive patients. Fixation was performed for seven acute fractures and twenty-two established non-unions. Union was achieved in 72.4% of patients. Six of the acute fractures and fifteen of the non-unions united successfully. Modified Mayo Wrist Score ranged between good to excellent in all patients who successfully united, whereas patients who failed to unite ranged between poor to excellent, with one poor and two moderate scores. No adverse biocompatibility reactions were seen. Two failures with broken screws were re-explored and one of these was thought to be due to screw mal-placement. The device used is an alternative to conventional metal implants and produces comparable union rates to metallic devices in the short term. PMID:24156576

  2. A piezoelectric screw dislocation interacting with a nonuniformly coated circular inclusion

    Microsoft Academic Search

    M. H. Shen; S. N. Chen; F. M. Chen

    2006-01-01

    This paper investigated the interaction of a piezoelectric screw dislocation with a nonuniformly coated circular inclusion in an unbounded piezoelectric matrix subjected to remote antiplane shear and electric fields. In addition to having a discontinuous displacement and a discontinuous electric potential across the slip plane, the dislocation is subjected to a line force and a line charge at the core.

  3. Southwick Osteotomy Stabilised with External Fixator

    PubMed Central

    Grubor, Predrag; Mitkovic, Milorad; Grubor, Milan

    2014-01-01

    ABSTRACT Introduction: Epiphysiolysis of the femoral head is the most common accident occurring towards the end of pre-puberty and puberty growth. Case report: The author describes the experience in the treatment of chronic epiphysiolysis in two patients treated by Southwick osteotomy. The site is accessed by way of a 15-cm long lateral skin incision and the trochanteric region is reached through the layers. The osteotomy angles prepared beforehand on a thin aluminium model are used to mark the Southwick osteotomy site on the anterior and lateral sides at the level of the lesser trochanter. Before performing the trochanteric osteotomy, two Mitkovi? convergent pins type M20 are applied distally and proximally, above the planned osteotomy site. A tenotomy of the iliopsas muscle is performed, and then the previously marked bone triangle is redissected up to three quarters of the width of the femur. The distal part of the femur is rotated inwards, so that the patella is turned towards the ceiling. The osteotomised fragments of the femur are adapted, repositioned and fixated by installing an external fixator on the previously placed pins. Two more pins are placed, one proximally and one distally, with a view to adequately stabilising the femur. The patient was mobile from day two after the surgery. If, after the surgery, the lead surgeon realises that there is a requirement to make a correction of 5, 10 and 15 degrees of the valgus, varus, anteversion or retroversion deformity, the correction shall be performed without surgically opening the patient, using the fixator pins. Conclusion: After performing a Southwick osteotomy it is easier to adapt, reposition and fixate the osteotomised fragments of the femur using a fixator type M20. Adequate stability allows regaining mobility quickly, which in turn is the best prevention of chondrolysis of the hip. It is possible to make post-operative valgus, varus, anteversion and retroversion corrections of 5, 10 and 15 degrees without performing a surgery. Once the osteotomy is healed, the fixator type M20 is removed without any additional surgery. PMID:25568571

  4. Failure of posterior titanium atlantoaxial cable fixation

    Microsoft Academic Search

    Rolando Garcia; Stephen Gorin

    2003-01-01

    Background context: The operative treatment of rotatory atlantoaxial instability remains controversial. The use of cable fixation has largely replaced the use of wire for interlaminar fixation. Although cable fixation offers biomechanical advantages over wire fixation, it is still at risk of fatigue failure. The authors were unable to locate any published reports of fatigue failure of titanium cables in the

  5. Molybdenum limitation of asymbiotic nitrogen fixation in tropical forest soils

    NASA Astrophysics Data System (ADS)

    Barron, Alexander R.; Wurzburger, Nina; Bellenger, Jean Phillipe; Wright, S. Joseph; Kraepiel, Anne M. L.; Hedin, Lars O.

    2009-01-01

    Nitrogen fixation, the biological conversion of di-nitrogen to plant-available ammonium, is the primary natural input of nitrogen to ecosystems, and influences plant growth and carbon exchange at local to global scales. The role of this process in tropical forests is of particular concern, as these ecosystems harbour abundant nitrogen-fixing organisms and represent one third of terrestrial primary production. Here we show that the micronutrient molybdenum, a cofactor in the nitrogen-fixing enzyme nitrogenase, limits nitrogen fixation by free-living heterotrophic bacteria in soils of lowland Panamanian forests. We measured the fixation response to long-term nutrient manipulations in intact forests, and to short-term manipulations in soil microcosms. Nitrogen fixation increased sharply in treatments of molybdenum alone, in micronutrient treatments that included molybdenum by design and in treatments with commercial phosphorus fertilizer, in which molybdenum was a `hidden' contaminant. Fixation did not respond to additions of phosphorus that were not contaminated by molybdenum. Our findings show that molybdenum alone can limit asymbiotic nitrogen fixation in tropical forests and raise new questions about the role of molybdenum and phosphorus in the tropical nitrogen cycle. We suggest that molybdenum limitation may be common in highly weathered acidic soils, and may constrain the ability of some forests to acquire new nitrogen in response to CO2 fertilization.

  6. Parameter estimation during automated screw insertions

    Microsoft Academic Search

    Mongkom Klingajay; Lakmal D. Seneviratne; Kaspar Althoefer

    2002-01-01

    Threaded fastenings are a common assembly method, accounting for over a quarter of all assembly operations. Threaded fastenings are popular because they permit easy disassembly for maintenance, repair, relocation and recycling. Screw insertions are typically carried out manually and are a difficult problem to automate. As a result there is very little published research on automating threaded fastenings, and most

  7. Computer simulation of screw dislocation in aluminum

    NASA Technical Reports Server (NTRS)

    Esterling, D. M.

    1976-01-01

    The atomic structure in a 110 screw dislocation core for aluminum is obtained by computer simulation. The lattice statics technique is employed since it entails no artificially imposed elastic boundary around the defect. The interatomic potential has no adjustable parameters and was derived from pseudopotential theory. The resulting atomic displacements were allowed to relax in all three dimensions.

  8. ROBOT WELDING TRAJECTORY PLANNING USING SCREW THEORY

    Microsoft Academic Search

    Renato Ventura; Bayan Henriques; Carlos Eduardo Pereira; Alexandre Queiroz Bracarense; Raul Guenther; Antonio O. Dourado; Daniel Martins

    This article presents a methodology for trajectory plannin g in robot welding applications, which handles parts with geometric restrictions . Differential kinematics are calc ulated using the screws theory and an optimal welding positi on (plain position) is obtained when defining the welding seque nce. The latter is the major contribution of the proposed methodology, since previous work have only

  9. A screw theory of static beams

    Microsoft Academic Search

    J. M. Selig; X. Ding

    2001-01-01

    We derive the deflection equation of a simple beam using the screw theory. The effects of tension, torsion and bending of the beam can be unified into a single equation. We begin by looking at the compliance matrix for small elements of the beam. This is loosely based on the work by von Mises (1924). We reproduce von Mises' results

  10. Screw Compressor Characteristics for Helium Refrigeration Systems

    Microsoft Academic Search

    Venkatarao Ganni; Peter Knudsen; Jonathan Creel; Dana Arenius; Fabio Casagrande; Matt Howell

    2008-01-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system.

  11. A model for biomass screw feeding

    Microsoft Academic Search

    Jianjun Dai; John R. Grace

    2008-01-01

    Successful feeding is critical to biomass utilization processes, but trouble-free delivery is difficult due to particle heterogeneity, physical characteristics and moisture content. A model, extended from previous models in the literature, is proposed to delineate what limits screw feeding in terms of the mechanisms of blockage and to predict torque requirements for biomass materials. Predictions on feeding of wood pellets,

  12. Long-term results of pediculo-body fixation and posterolateral fusion for lumbar spondylolisthesis.

    PubMed

    Zagra, Antonino; Giudici, Fabrizio; Minoia, Leone; Corriero, Andrea Saverio; Zagra, Luigi

    2009-06-01

    Grob et al. (Eur Spine J 5:281-285, 1996) illustrated a new fixation technique in inveterate cases of grade 2-3 spondylolisthesis (degenerative or spondylolytic): a fusion without reduction of the spondylolisthesis. Fixation of the segment was achieved by two cancellous bone screws inserted bilaterally through the pedicles of the lower vertebra into the body of the upper slipped vertebra. Since 1998 we have been using this technique according to the authors' indications: symptomatic spondylolisthesis with at least 25% anterior slippage and advanced disc degeneration. Afterwards this technique was used also in spondylolisthesis with low reduction of the disc height and slippage less than 25%. In every case we performed postero-lateral fusion and fixation with two AO 6.5 Ø thread 16 mm cancellous screws. From 1998 to 2002 we performed 62 fusions for spondylolisthesis with this technique: 28 males (45.16%) and 34 females (54.84%), mean age 45 years (14-72 years). The slipped vertebra was L5 in 57 cases (92%), L4 in 2 cases (3.2%), L3 in 1 case (1.6%), combined L4 and L5 in 2 cases (3.2%). In all cases there was an ontogenetic spondylolisthesis with lysis. Lumbar pain was present in 22 patients and lumbar-radicular pain was present in 40 patients. The mean preoperative VAS was 6.2 (range 5-8) for lumbar pain, and 5.5 (range 4-7) for leg pain. The fusion area was L5-S1 in 53 cases (85.5%), L3-L4 in 1 case (1.6%), L4-S1 in 8 cases (12.9%). A decompression of the spinal canal by laminectomy was performed in 33 procedures (53%). When possible a bone graft was done from the removed neural arc, and from the posterior iliac crest in the other cases. The mean blood loss was about 254 ml (100-1,000). The mean operative time was 75 min (range 60-90). The results obtained by computerized analysis at follow-up at least 5 years after surgery showed a significant improvement in preoperative symptoms. The patients were asymptomatic in 52 cases (83.9%); strained-back pain was present in 8 cases (12.9%), and there was persistent lumbar-radicular pain in 2 cases (3.2%). The mean ODI score was 2.6%, the mean VAS back pain was 1.3, the mean VAS leg pain 0.7. Some complications were observed: a nerve root compression by a screw invasion of intervertebral foramen, resolved by screw removal; an iliac artery compression by a lateral exit screw from pediculo, resolved by screw removal; a deep iliac vein phlebitis with thrombosis caused by external compression due to a wrong intraoperative position, treated by medicine. Two cases of synthesis mobilization and two cases of broken screws was detected. No cases of pseudoarthrosis and immediate or late superficial or deep infection were observed. The analysis of the long-term results of the spondylolisthesis surgical treatment with direct pediculo-body screw fixation and postero-lateral fusion gave a very satisfactory response. The technique is reliable in allowing an optimal primary stability, creating the best biomechanical conditions to obtain a solid fusion. PMID:19444490

  13. Spinal somatosensory evoked potential evaluation of acute nerve-root injury associated with pedicle-screw placement procedures: an experimental study.

    PubMed

    Jou, I-Ming; Hsu, Che-Chia; Chern, Tai-Chang; Chen, Wen-Yi; Dau, Yuan-Chang

    2003-03-01

    Pedicle screws for spinal fixation risk neural damage because of the proximity between screw and nerve root. We assessed whether spinal somatosensory evoked potential (SSEP) could selectively detect pedicle-screw-related acute isolated nerve injury. Because pedicle screws are too large for a rat's spine, we inserted a K-wire close to the pedicle in 32 rats, intending not to injure the nerve root in eight (controls), and to injure the L4 or L5 root in 24. We used sciatic-nerve-elicited SSEP pre- and postinsertion. Radiologic, histologic, and postmortem observations confirmed the level and degree of root injury. Sciatic (SFI), tibial (TFI), and peroneal function indices (PFI) were calculated and correlated with changes in potential. Although not specific for injuries to different roots, amplitude reduction immediately postinsertion was significant in the experimental groups. Animals with the offending wire left in place for one hour showed a further non-significant deterioration of amplitude. Electrophysiologic changes correlated with SFI and histologic findings in all groups. SSEP monitoring provided reliable, useful diagnostic and intraoperative information about the functional integrity of single nerve-root injury. These findings are clinically relevant to acute nerve-root injury and pedicle-screw insertion. If a nerve-root irritant remains in place, a considerable neurologic deficit will occur. PMID:12568971

  14. A Biomechanical Comparison of Intralaminar C7 Screw Constructs with and without Offset Connector Used for C6-7 Cervical Spine Immobilization : A Finite Element Study

    PubMed Central

    Qasim, Muhammad; Natarajan, Raghu N.; An, Howard S.

    2013-01-01

    Objective The offset connector can allow medial and lateral variability and facilitate intralaminar screw incorporation into the construct. The aim of this study was to compare the biomechanical characteristics of C7 intralaminar screw constructs with and without offset connector using a three dimensional finite element model of a C6-7 cervical spine segment. Methods Finite element models representing C7 intralaminar screw constructs with and without the offset connector were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the two techniques were compared under pure moments in flexion, extension, lateral bending and axial rotation. Results ROM for intralaminar screw construct with offset connector was less than the construct without the offset connector in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in both constructs. Maximum von Mises stress in the construct without offset connector was found to be 12-30% higher than the corresponding stresses in the construct with offset connector in the three principal directions. Conclusion This study demonstrated that the intralaminar screw fixation with offset connector is better than the construct without offset connector in terms of biomechanical stability. Construct with the offset connector reduces the ROM of C6-7 segment more significantly compared to the construct without the offset connector and causes lower stresses around the C7 pedicle-vertebral body complex. PMID:24003366

  15. Cortical screw trajectory for instrumentation and fusion in the setting of osteopathic compression fracture allows for percutaneous kyphoplasty for adjacent level compression fractures.

    PubMed

    Pacione, Donato; Kim, Irene; Wilson, Taylor A; Frempong-Boadu, Anthony

    2015-05-01

    Spinal fixation in the osteoporotic patient can be challenging due to the poor trabecular bone quality of the vertebral body. Patients with osteoporotic vertebral body compression fractures are at risk for future compression fractures at adjacent levels, especially after cement augmentation. The purpose of this technical report is to describe the utilization of a cortical screw trajectory along with kyphoplasty for a patient with an osteoporotic compression fracture as well as degenerative spinal disease. This trajectory allows for the possibility of percutaneous pedicle access in the event of future compression fractures. Our patient underwent a decompressive laminectomy and kyphoplasty at the level of an osteoporotic compression fracture. The fracture was stabilized with cortical screw instrumentation and fusion at a level above and a level below the fracture. Subsequently the patient developed an adjacent level fracture within the fusion construct. Due to the utilization of a cortical screw trajectory for the initial fusion, the traditional pedicle trajectory was still accessible. As a result, the new fracture was treated with a percutaneous kyphoplasty through a standard pedicle trajectory. In conclusion, the use of a cortical screw trajectory for stabilization of osteoporotic compression fractures provides for a stronger bone screw interface and avoids osteoporotic trabecular vertebral body bone. At the same time this trajectory allows for future percutaneous pedicular access in the event that the patient suffers future compression fractures. PMID:25724313

  16. Anatomic Feasibility of Posterior Cervical Pedicle Screw Placement in Children: Computerized Tomographic Analysis of Children Under 10 Years Old

    PubMed Central

    Lee, HoJin; Kim, Il Sup; Kim, Moon Suk; Sung, Jae Hoon; Lee, Sang Won

    2014-01-01

    Objective To evaluate the anatomical feasibility of 3.5 mm screw into the cervical spine in the pediatric population and to establish useful guidelines for their placement. Methods A total of 37 cervical spine computerized tomography scans (24 boys and 13 girls) were included in this study. All patients were younger than 10 years of age at the time of evaluation for the period of 2007-2011. Results For the C1 screw placement, entry point height (EPH) was the most restrictive factor (47.3% patients were larger than 3.5 mm). All C2 lamina had a height larger than 3.5 mm and 68.8% (51/74) of C2 lamina had a width thicker than 3.5 mm. For C2 pedicle width, 55.4% (41/74) of cases were larger than 3.5 mm, while 58.1% (43/74) of pedicle heights were larger than 3.5 mm. For pedicle width of subaxial spine, 75.7% (C3), 73% (C4), 82.4% (C5), 89.2% (C6), and 98.1% (C7, 1/54) were greater than 3.5 mm. Mean lamina width of subaxial cervical spine was 3.1 (C3), 2.7 (C4), 2.9 (C5), 3.8 (C6), and 4.0 mm (C7), respectively. Only 34.6% (127/370) of subaxial (C3-7) lamina thickness were greater than 3.5 mm. Mean length of lateral mass for the lateral mass screw placement was 9.28 (C3), 9.08 (C4), 8.81 (C5), 8.98 (C6), and 10.38 mm (C7). Conclusion C1 lateral mass fixation could be limited by the morphometrics of lateral mass height. C2 trans-lamina approach is preferable to C2 pedicle screw fixation. In subaxial spines, pedicle screw placement was preferable to trans-lamina screw placement, except at C7. PMID:25628806

  17. Posterior lumbar interbody fusion using one diagonal fusion cage with transpedicular screw\\/rod fixation

    Microsoft Academic Search

    Jie Zhao; Tiesheng Hou; Xinwei Wang; Shengzhong Ma

    2003-01-01

    Posterior lumbar interbody fusion (PLIF) using threaded cages has gained wide popularity for lumbosacral spinal disease. Our biomechanical tests showed that PLIF using a single diagonal cage with unilateral facetectomy does add a little to spinal stability and provides equal or even higher postoperative stability than PLIF using two posterior cages with bilateral facetectomy. Studies also demonstrated that cages placed

  18. Use of a synthetic bone void filler to augment screws in osteopenic ankle fracture fixation

    Microsoft Academic Search

    GeirStray Andreassen; PerReidar Høiness; Inge Skraamm; Odd Granlund; Lars Engebretsen

    2004-01-01

    IntroductionSufficiently stable constructs may be difficult to obtain with ankle fractures in patients with severe osteopenic bone. Augmentation of the osteosynthesis with a new synthetic bone void filler may help to solve this problem, and it can improve the clinical outcome.Materials and methodsA prospective, open-label study was performed in two surgical clinics in Norway. In 37 of 42 selected patients

  19. Posterior interbody fusion using laminectomy bone and transpedicular screw fixation in the treatment of lumbar spondylolisthesis

    Microsoft Academic Search

    György I Csécsei; Álmos P Klekner; József Dobai; Attila Lajgut; Judit Sikula

    2000-01-01

    BACKGROUNDLaminectomy bone is used widely in posterolateral lumbar fusion, but not interbody fusion. No prospective evaluation of interbody fusion using bone grafts from the posterior neural arch in spondylolisthesis has been found in the literature. We prospectively studied series of patients operated on for lumbar spondylolisthesis to evaluate clinical improvement and bony fusion.METHODSForty-six patients were operated on for lumbar spondylolisthesis

  20. One point fixation of zygomatic tripod fractures in the zygomatic buttress through Keen's intraoral approach: A review of 30 cases

    PubMed Central

    Dakir, Abu; Muthumani, T.; Prabu, N. P.; Mohan, Rakesh; Maity, Abhishek

    2015-01-01

    For decades, facial beauty and esthetics have been one of the most important quests of the human race. The lateral prominence and convexity of the zygomatic bone makes it the most important bone for providing the aesthetic facial look and sets up the facial width but at the same time this prominence and convexity makes this bone more vulnerable to injury. Zygomatic complex fractures or tripod fractures are the second most common fractures after nasal fractures among facial injuries. Several studies have been undertaken regarding the reduction and fixation of zygomatic fractures with mini plates and screws. In 2002 Fujioka et al in vivo studies successfully proved that one point fixation at the zygomaticomaxillary complex gives three point alignment and sufficient rigidity when the fractures are not comminuted. In this article, 30 cases have been reviewed with one point fixation of zygomatic complex tripod fractures at the zygomatic buttress through Keen's intraoral approach along with advantages and disadvantages. PMID:26015722

  1. Flexor tendon repair after rupture caused by volar plate fixation of the distal radius.

    PubMed

    Rubensson, Carin C; Ydreborg, Karin; Boren, Linda; Karlander, Lars-Erik

    2015-04-01

    Volar plate fixation of unstable fractures of the distal radius is preferred by a majority of surgeons today. One known complication is the rupture of flexor tendons. The aim of this paper is to present flexor tendon ruptures after volar plate fixation analysing the clinical outcome after tendon surgery, aetiology, and methods of prevention. Seventeen consecutive ruptures in 14 patients were included. The incidence was 1.4%. Three patients declined tendon surgery. Eleven patients were treated with a free tendon graft. Only two patients showed excellent results regarding mobility in the thumb and/or fingers. Analysis of radiographs demonstrated sub-optimal placement of plate or screws in all cases. Rupture of a flexor tendon is a serious complication where the functional outcome after surgical reconstruction is uncertain. Early removal of the plate when the placement is sub-optimal or when local volar tenderness appears would probably prevent many ruptures. PMID:25162925

  2. Percutaneous Cannulated Screws with Tension Band Wiring Technique in Patella Fractures

    PubMed Central

    2013-01-01

    Introduction Most patellar fractures are transverse involving the central third. Open reduction and stabilization of transverse patellar fractures is indicated if there is more than 2-3 mm of fragment separation and/or articular incongruity. Surgical Technique This study describes a percutaneous 2 cannulated screws and modified tension band wiring technique to treat transverse patellar fractures. Materials and Methods We performed 30 cases of displaced transverse patellar fractures with this technique. The clinical outcomes of these patients were evaluated with simple radiographs, range of motion and Lyshom score. Results This technique has shown to provide satisfactory clinical results and excellent knee functions. Conclusions This technique provide stable fixation, allows early motion exercise by minimizing injury to extensor mechanism and reduce cosmetic problem in scar. PMID:24369000

  3. Strategy for salvage pedicle screw placement: A technical note

    PubMed Central

    Fujibayashi, Shunsuke; Takemoto, Mitsuru; Neo, Masashi; Matsuda, Shuichi

    2013-01-01

    Background Salvage surgery for failed lumbar spine fusion with a loosened pedicle screw is challenging. In general, the strategy includes replacement with larger and longer pedicle screws, augmentation with polymethylmethacrylate cement or hydroxyapatite granules, and extension of fused segments. The purpose of this study is to introduce a new technique for pedicle screw replacement after failed lumbar spine fusion. Methods Five salvage operations were performed using a different trajectory (DT) pedicle screw replacement technique based on 3-dimensional radiological information. Position of the alternative pedicle screws was planned carefully on the computer screen of a computed tomography-based navigation system before the operation. To obtain sufficient initial stability, 1 of 2 techniques was chosen, depending on the patient. One technique created a completely new route, which did not interfere with the existing screw hole, and the other involved penetration of the existing screw hole. Results DT pedicle screws were replaced successfully according to the preoperative plan. In all patients, bony union were achieved at the final follow-up period without any instrument failure. Extension of the fused segments could be avoided by using the DT pedicle screw replacement technique combined with transforaminal lumbar interbody fusion. Conclusions The DT pedicle screw replacement technique is a treatment option for salvage lumbar spine surgery. Clinical relevance The current technique is a treatment option for salvage operations that can both avoid extension of a fused segment and achieve successful bony union. PMID:25694906

  4. Biomass granular screw feeding: An experimental investigation

    Microsoft Academic Search

    Jianjun Dai; John R. Grace

    2011-01-01

    Successful feeding is critical to biomass utilization processes, but difficult due to the heterogeneity, physical properties and moisture content of the particles. The objectives of the present study were to find the mechanisms of blockage in screw feeding and to determine the effects of particle mean size (0.5–15mm), size distribution, shape, moisture content (10–60%), density and compressibility on biomass particle

  5. Autistic Symptomatology, Face Processing Abilities, and Eye Fixation Patterns

    ERIC Educational Resources Information Center

    Kirchner, Jennifer C.; Hatri, Alexander; Heekeren, Hauke R.; Dziobek, Isabel

    2011-01-01

    Deviant gaze behavior is a defining characteristic of autism. Its relevance as a pathophysiological mechanism, however, remains unknown. In the present study, we compared eye fixations of 20 adults with autism and 21 controls while they were engaged in taking the Multifaceted Empathy Test (MET). Additional measures of face emotion and identity…

  6. Global patterns of marine nitrogen fixation and denitrification

    Microsoft Academic Search

    Nicolas Gruber; Jorge L. Sarmiento

    1997-01-01

    A new quasi-conservative tracer N*, defined as a linear combination of nitrate and phosphate, is proposed to investigate the distribution of nitrogen fixation and denitrification in the world oceans. Spatial patterns of N* are determined in the different ocean basins using data from the Geochemical Ocean Sections Study (GEOSECS) cruises (1972-1978) and from eight additional cruises in the Atlantic Ocean.

  7. Phosphorus limitation controls rates of biological N2-fixation in boreal peatlands

    NASA Astrophysics Data System (ADS)

    Dynarski, K. A.; Wieder, R.; Vile, M. A.

    2013-12-01

    N2-fixation, once thought to occur at negligible rates in pristine boreal peatlands, has recently been demonstrated to be the dominant input of nitrogen (N) to these ecosystems. The controls of biological N2-fixation in pristine boreal peatlands are not well understood, but limitation of the nutrients molybdenum (Mo) and phosphorus (P) may play a key role. Because the enzyme nitrogenase requires molybdenum-containing cofactors to function, biological N2-fixation may be limited by the trace metal molybdenum. Recent studies have shown that Mo limits nitrogen fixation rates in tropical soils. P availability may also be important in regulating N2-fixation rates; N2-fixation is a P-intensive process because the nitrogenase enzyme is rich in P, and P is likely to be the most limiting nutrient to boreal peatland productivity, next to N. In this study, we examined the role of Mo and P limitation in controlling rates of biological N2-fixation in boreal peatlands. We applied Mo and P nutrient amendments equivalent to 5 mg m-2 yr-1and 10 kg ha-1 yr-1 respectively, both alone and in combination, to fifteen 0.36 m2 plots in a pristine Alberta fen throughout the summer 2013 growing season. We periodically assessed N2-fixation rates in Sphagnum angustifolium moss samples using the acetylene reduction assay with subsequent calibration using 15N2. We found a significant overall treatment effect (F3,44=15.62, p<0.0001). A posteriori analysis using Tukey's HSD indicates that N2-fixation rates were significantly higher in plots receiving P additions relative to control plots. However, Mo additions had no effect on N2-fixation rates. These results indicate that P, not Mo, availability is dominant in controlling rates of biological N2-fixation in boreal peatland ecosystems.

  8. UK DRAFFT - A randomised controlled trial of percutaneous fixation with kirschner wires versus volar locking-plate fixation in the treatment of adult patients with a dorsally displaced fracture of the distal radius

    PubMed Central

    2011-01-01

    Background Fractures of the distal radius are extremely common injuries in adults. However, the optimal management remains controversial. In general, fractures of the distal radius are treated non-operatively if the bone fragments can be held in anatomical alignment by a plaster cast or orthotic. However, if this is not possible, then operative fixation is required. There are several operative options but the two most common in the UK, are Kirschner-wire fixation (K-wires) and volar plate fixation using fixed-angle screws (locking-plates). The primary aim of this trial is to determine if there is a difference in the Patient-Reported Wrist Evaluation one year following K-wire fixation versus locking-plate fixation for adult patients with a dorsally-displaced fracture of the distal radius. Methods/design All adult patients with an acute, dorsally-displaced fracture of the distal radius, requiring operative fixation are potentially eligible to take part in this study. A total of 390 consenting patients will be randomly allocated to either K-wire fixation or locking-plate fixation. The surgery will be performed in trauma units across the UK using the preferred technique of the treating surgeon. Data regarding wrist function, quality of life, complications and costs will be collected at six weeks and three, six and twelve months following the injury. The primary outcome measure will be wrist function with a parallel economic analysis. Discussion This pragmatic, multi-centre trial is due to deliver results in December 2013. Trial registration Current Controlled Trials ISRCTN31379280 UKCRN portfolio ID 8956 PMID:21914196

  9. Molybdenum Trafficking for Nitrogen Fixation

    PubMed Central

    Hernandez, Jose A.; George, Simon J.; Rubio, Luis M.

    2009-01-01

    The molybdenum nitrogenase is responsible for most biological nitrogen fixation, a prokaryotic metabolic process that determines the global biogeochemical cycles of nitrogen and carbon. Here we describe the trafficking of molybdenum for nitrogen fixation in the model diazotrophic bacterium Azotobacter vinelandii. The genes and proteins involved in molybdenum uptake, homeostasis, storage, regulation, and nitrogenase cofactor biosynthesis are reviewed. Molybdenum biochemistry in A. vinelandii reveals unexpected mechanisms and a new role for iron-sulfur clusters in the sequestration and delivery of molybdenum. PMID:19772354

  10. Foam granulation: new developments in pharmaceutical solid oral dosage forms using twin screw extrusion machinery.

    PubMed

    Thompson, M R; Weatherley, S; Pukadyil, R N; Sheskey, P J

    2012-07-01

    This paper investigates foam granulation in a twin screw extruder as a new continuous wet granulation technique for pharmaceutical powder drug formulations. Foamed aqueous binder has a reportedly lower soak-to-spread ratio than drop or spray liquid addition in batch granulation. This work demonstrates a twin screw extruder configuration for foam granulation and subsequently compares the new approach against liquid injection in the granulation of ?-lactose monohydrate with a methylcellulose binder. Trials were conducted at high powder output rates (20-40 kg/h) and high screw speeds (220-320 RPM) with two screw configurations. Process stability improved with the new technique allowing granulation with less binder. The extruded mass maintained a low exit temperature, being insensitive to operating conditions unlike the liquid injection approach, where temperatures rose significantly as flow rate increased. The particle size distribution by foam granulation reflected a more uniformly wetted mass with larger granule growth noted even for conditions where dry powder exited by liquid injection. Other factors were found similar between the two binder delivery methods such as consumed mechanical energy, as well as fracture strength and compressibility of produced granules. PMID:22085462

  11. What Is the Relevance of the Tip-Apex Distance as a Predictor of Lag Screw Cut-Out?

    PubMed Central

    Goffin, Jérôme M.; Jenkins, Paul J.; Ramaesh, Rishikesan; Pankaj, Pankaj; Simpson, A. Hamish

    2013-01-01

    Using a simple mathematical formulation, the relationship between the position of the lag screw tip (relevant to both intramedullary and extramedullary devices) and the concept of tip-apex distance (TAD) was derived. TAD is widely used in operating theaters as a surgical guideline in relation to the fixation of trochanteric fractures, and in clinical studies as a predictor of lag screw cut-out. In order to visualize better this concept, the locus of points having the same TAD was plotted and the dependence of TAD on the location of the lag screw tip was also reported. It was shown that TAD should be adjusted for the size of the femoral head (a variable which varies a lot according to the sex of the patient) while no correlation was found between TAD and bone morphometry indices obtained from micro-CT data (BV/TV and Tb.Th). Therefore, these results seem to suggest that TAD lacks mechanical justification and that predictors which are based on mechanical properties, such as bone density, should be investigated further. PMID:24015184

  12. The gauge theory of dislocations: A nonuniformly moving screw dislocation

    NASA Astrophysics Data System (ADS)

    Lazar, Markus

    2010-07-01

    We investigate the nonuniform motion of a straight screw dislocation in infinite media in the framework of the translational gauge theory of dislocations. The equations of motion are derived for an arbitrarily moving screw dislocation. The fields of the elastic velocity, elastic distortion, dislocation density and dislocation current surrounding the arbitrarily moving screw dislocation are derived explicitly in the form of integral representations. We calculate the radiation fields and the fields depending on the dislocation velocities.

  13. Screw theoretic view on dynamics of spatially compliant beam

    Microsoft Academic Search

    Xi-lun Ding; J. M. Selig

    2010-01-01

    Beams with spatial compliance can be deformed as bending in a plane, twisting, and extending. In terms of the screw theory\\u000a on rigid body motions, the concept of “deflection screw” is introduced, a spatial compliant beam theory via the deflection\\u000a screw is proposed, and the spatial compliance of such a beam system is presented and analysed based on the material

  14. Complement fixation test to C. burnetii

    MedlinePLUS

    The complement fixation test to C. burnetii is a blood test that checks for infection due to bacterium called ... for Coxiella antibodies using a laboratory method called complement fixation. This technique checks if the body has ...

  15. Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

    PubMed Central

    Kogias, Evangelos; Sircar, Ronen; Krüger, Marie T.; Volz, Florian; Scheiwe, Christian; Hubbe, Ulrich

    2015-01-01

    Purpose. To describe the minimally invasive technique for cement augmentation of cannulated and fenestrated screws using an injection cannula as well as to report its safety and efficacy. Methods. A total of 157 cannulated and fenestrated pedicle screws had been cement-augmented during minimally invasive posterior screw-rod spondylodesis in 35 patients from January to December 2012. Retrospective evaluation of cement extravasation and screw loosening was carried out in postoperative plain radiographs and thin-sliced triplanar computed tomography scans. Results. Twenty-seven, largely prevertebral cement extravasations were detected in 157 screws (17.2%). None of the cement extravasations was causing a clinical sequela like a new neurological deficit. One screw loosening was noted (0.6%) after a mean follow-up of 12.8 months. We observed no cementation-associated complication like pulmonary embolism or hemodynamic insufficiency. Conclusions. The presented minimally invasive cement augmentation technique using an injection cannula facilitates convenient and safe cement delivery through polyaxial cannulated and fenestrated screws during minimally invasive screw-rod spondylodesis. Nevertheless, the optimal injection technique and design of fenestrated screws have yet to be identified. This trial is registered with German Clinical Trials DRKS00006726.

  16. Tissue fixation and the effect of molecular fixatives on downstream staining procedures

    PubMed Central

    Howat, William J.; Wilson, Beverley A.

    2014-01-01

    It is impossible to underplay the importance of fixation in histopathology. Whether the scientist is interested in the extraction of information on lipids, proteins, RNA or DNA, fixation is critical to this extraction. This review aims to give a brief overview of the current “state of play” in fixation and focus on the effect fixation, and particularly the effect of the newer brand of “molecular fixatives” have on morphology, histochemistry, immunohistochemistry and RNA/DNA analysis. A methodology incorporating the creation of a fixation tissue microarray for the study of the effect of fixation on histochemistry is detailed. PMID:24561827

  17. CARBON FIXATION BY CULTURED CLAMSCARBON FIXATION BY CULTURED CLAMSCARBON FIXATION BY CULTURED CLAMSCARBON FIXATION BY CULTURED CLAMS Patrick BakerPatrick Baker

    E-print Network

    Florida, University of

    CARBON FIXATION BY CULTURED CLAMSCARBON FIXATION BY CULTURED CLAMSCARBON FIXATION BY CULTURED, Gainesville, FL, USA Clam Farming in FloridaClam Farming in Florida Calculating Carbon per Clam Bag E t l th E th g Calculating Carbon per Clam Bag Eat a clam, save the EarthEat a clam, save the Earth · Northern

  18. FIXATIVES AND EMBEDDING MEDIA FOR IMMUNOCYTOCHEMISTRY

    Microsoft Academic Search

    B. B. Rawdon

    1998-01-01

    In this article fixation and embedding procedures compatible with preparation of animal tissues for immunocytochemistry are reviewed. A number of methods is available for light microscopic immunocytochemistry: these include cryostat, freeze-dried and wax sections of tissue fixed with either vapour or immersion fixatives. Use of the microwave oven to fix tissues for immunocytochemistry is also discussed. Fixation methods for immuno-electron

  19. Transit Fixatives: An Innovative Study

    PubMed Central

    A, Ravi Prakash; G, Sreenath; JK, Sonia Bai; NDVN, Shyam

    2015-01-01

    Background: Universally accepted fixative is 10% formalin which has been used for preserving the tissues and their architecture. In certain conditions, formalin might not be readily available for immediate fixation. We here by explore more economical, eco-friendly and easily available solutions that can be used as transit media/ transporting media for tissue specimens. Materials and Methods: The study included commonly available solutions like Spirit, Saline, Betadine solution, Hydrogen peroxide (H2O2), Local anesthesia (L.A), Rose water, Coconut oil, Coconut water, Ice cold water, Honey and Milk while keeping formalin as control. The fresh tissue sample was cut into multiple bits and placed in different containers for a period of 8 hours before transferring to formalin solution. Conclusion: Transit fixatives are very important in certain situations where formalin is not readily available. These fixatives can be used to fix the tissues for a period of at least 8 hours without causing any damage or distortion before they are fixed in formalin solution. PMID:25954725

  20. Posterior atlantoaxial fixation: A cadaveric and fluoroscopic step-by-step technical guide

    PubMed Central

    Sattarov, Kamran; Skoch, Jesse; Abbasifard, Salman; Patel, Apar S.; Avila, Mauricio J.; Walter, Christina M.; Baaj, Ali A.

    2015-01-01

    Background: Atlantoaxial surgical fixation is widely employed treatment strategy for a myriad of pathologies affecting the stability of the atlantoaxial joint. The most common technique used in adults, and in certain cases in children, involves a posterior construct with C1 lateral mass screws, and C2 pars or pedicle screws. This technical note aims to provide a step-by-step guide to this procedure using cadaveric and fluoroscopic images. Methods: An embalmed, human, cadaveric, specimen was used for this study. The subject did not have obvious occipital-cervical pathology. Dissections and techniques were performed to mimic actual surgical technique. Photographs were taken during each step, and the critical aspects of each step were highlighted. Fluoroscopic images from a real patient undergoing C1/C2 fixation were also utilized to further highlight the anatomic-radiographic relationships. This study was performed without external or industry funding. Results: Photographic and radiographic pictures and drawings are presented to illustrate the pertinent anatomy and technical aspects of this technique. The nuances of each step, including complication avoidance strategies are also highlighted. Conclusions: Given the widespread utilization of this technique, described step-by-step guide is timely for surgeons and trainees alike. PMID:26005587

  1. Postfusion pullout strength comparison of a novel pedicle screw with classical pedicle screws on synthetic foams.

    PubMed

    Arslan, Arslan K; Demir, Teyfik; Ormeci, Mehmet F; Camu?cu, Necip; Türeyen, Kudret

    2013-02-01

    Pullout is a very common failure mode on the use of pedicle screws. Numerous studies were completed to increase the pullout strength of pedicle screws especially for osteoporotic bones. In this study, a previously designed pedicle screw type was tested before and after fusion condition. Synthetic polyurethane foams were used in all tests. Three different grades of foams were used in tests to simulate severely osteoporotic, osteoporotic, and healthy bones. Test blocks were produced and characterized in our clinical biomechanics laboratory. Foaming of polyurethane was accepted as fusion process (bone in growth). Pedicle screw including radial holes (new design) was tested both before and after the fusion. It also exhibited remarkably higher pullout strength after fusion than before fusion and most of other alternatives stated in the literature. In total, 70% higher pullout strength was achieved with new design after fusion. On the other hand, new design did not dominate other alternatives when comparison was carried out on severely osteoporotic and healthy bones. To the knowledge of the authors, this is the first study investigating the postfusion properties on synthetic foams. PMID:23513982

  2. Wet granulation in a twin-screw extruder: implications of screw design.

    PubMed

    Thompson, M R; Sun, J

    2010-04-01

    Wet granulation in twin-screw extrusion machinery is an attractive technology for the continuous processing of pharmaceuticals. The performance of this machinery is integrally tied to its screw design yet little fundamental knowledge exists in this emerging field for granulation to intelligently create, troubleshoot, and scale-up such processes. This study endeavored to systematically examine the influence of different commercially available screw elements on the flow behavior and granulation mechanics of lactose monohydrate saturated at low concentration (5-12%, w/w) with an aqueous polyvinyl-pyrrolidone binder. The results of the work showed that current screw elements could be successfully incorporated into designs for wet granulation, to tailor the particle size as well as particle shape of an agglomerate product. Conveying elements for cohesive granular flows were shown to perform similar to their use in polymer processing, as effective transport units with low specific mechanical energy input. The conveying zones provided little significant change to the particle size or shape, though the degree of channel fill in these sections had a significant influence on the more energy-intensive mixing elements studied. The standard mixing elements for this machine, kneading blocks and comb mixers, were found to be effective for generating coarser particles, though their mechanisms of granulation differed significantly. PMID:19890935

  3. Modeling bicortical screws under a cantilever bending load.

    PubMed

    James, Thomas P; Andrade, Brendan A

    2013-12-01

    Cyclic loading of surgical plating constructs can precipitate bone screw failure. As the frictional contact between the plate and the bone is lost, cantilever bending loads are transferred from the plate to the head of the screw, which over time causes fatigue fracture from cyclic bending. In this research, analytical models using beam mechanics theory were developed to describe the elastic deflection of a bicortical screw under a statically applied load. Four analytical models were developed to simulate the various restraint conditions applicable to bicortical support of the screw. In three of the models, the cortical bone near the tip of the screw was simulated by classical beam constraints (1) simply supported, (2) cantilever, and (3) split distributed load. In the final analytical model, the cortices were treated as an elastic foundation, whereby the response of the constraint was proportional to screw deflection. To test the predictive ability of the new analytical models, 3.5?mm cortical bone screws were tested in a synthetic bone substitute. A novel instrument was developed to measure the bending deflection of screws under radial loads (225?N, 445?N, and 670?N) applied by a surrogate surgical plate at the head of the screw. Of the four cases considered, the analytical model utilizing an elastic foundation most accurately predicted deflection at the screw head, with an average difference of 19% between the measured and predicted results. Determination of the bending moments from the elastic foundation model revealed that a maximum moment of 2.3?N m occurred near the middle of the cortical wall closest to the plate. The location of the maximum bending moment along the screw axis was consistent with the fracture location commonly observed in clinical practice. PMID:24105350

  4. Displacement field of a screw dislocation in a <011> Cu nanowire: An atomistic study

    NASA Astrophysics Data System (ADS)

    Gailhanou, Marc; Roussel, Jean-Marc

    2013-12-01

    By performing atomistic calculations with a tight-binding potential, we study the displacement field induced by a screw dislocation lying along a free <011> Cu cylindrical nanowire. For this anisotropic orientation that is often encountered experimentally, we show that the displacement field uz along the nanowire can be seen as the superposition of three different fields: the screw dislocation field in an infinite medium, the warping displacement field caused by the so-called Eshelby twist, and an additional image field induced by the free surfaces. A Fourier series analysis of this latter image displacement and stress fields is given. For a circular cross section of the wire, this image field corresponds mainly to an additional warping displacement uz?xy. The dissociation mechanism of the dislocation into partials and the surface stress effects being also captured in our simulations, the present study enables one to quantify the various contributions to the formation of the x-ray diffractograms.

  5. Screw-type pump for coal feeding

    SciTech Connect

    Hilbert, J.D. Jr.

    1983-05-01

    This article describes the Type-M pumps system, which provides the reliable and accurate coal feeding needed for the success of fluidized-bed combustion and other coal-firing requirements. The Type-M pump feed unit provides the safety feature with its internal flapper valve to prevent the possibility of blowback. It features bearing supports at both ends of the screw impeller shaft which permits smooth running and maintenance-free operation under variable feed and light load conditions. It has demonstrated its capability to handle not only finely pulverized coal but also coarse coal as well as a mixture of coarse coal and 1/8 x 0 limestone.

  6. Injection of coal by screw feed

    NASA Technical Reports Server (NTRS)

    Fisher, R.

    1977-01-01

    The use of the screw feeder for injecting solids through a 20 to 30 psi barrier is common practice in the cement making industry. An analytical extrapolation of that design, accounting for pressure holding characteristics of a column of solids, shows that coal can be fed to zones at several hundred psi with minimal or no loss of gas. A series of curves showing the calculated pressure gradient through a moving column of solids is presented. Mean particle size, solids velocity, and column length are parameters. Further study of this system to evaluate practicality is recommended.

  7. A Robot-Assisted Surgical System Using a Force-Image Control Method for Pedicle Screw Insertion

    PubMed Central

    Tian, Wei; Han, Xiaoguang; Liu, Bo; Liu, Yajun; Hu, Ying; Han, Xiao; Xu, Yunfeng; Fan, Mingxing; Jin, Haiyang

    2014-01-01

    Objective To introduce a robot-assisted surgical system for spinal posterior fixation that can automatically recognize the drilling state and stop potential cortical penetration with force and image information and to further evaluate the accuracy and safety of the robot for sheep vertebra pedicle screw placement. Methods The Robotic Spinal Surgery System (RSSS) was composed of an optical tracking system, a navigation and planning system, and a surgical robot equipped with a 6-DOF force/torque sensor. The robot used the image message and force signals to sense the different operation states and to prevent potential cortical penetration in the pedicle screw insertion operation. To evaluate the accuracy and safety of the RSSS, 32 screw insertions were conducted. Furthermore, six trajectories were deliberately planned incorrectly to explore whether the robot could recognize the different drilling states and immediately prevent cortical penetration. Results All 32 pedicle screws were placed in the pedicle without any broken pedicle walls. Compared with the preoperative planning, the average deviations of the entry points in the axial and sagittal views were 0.50±0.33 and 0.65±0.40 mm, and the average deviations of the angles in the axial and sagittal views were 1.9±0.82° and 1.48±1.2°. The robot successfully recognized the different drilling states and prevented potential cortical penetration. In the deliberately incorrectly planned trajectory experiments, the robot successfully prevented the cortical penetration. Conclusion These results verified the RSSS’s accuracy and safety, which supported its potential use for the spinal surgery. PMID:24466043

  8. Fixations on objects in natural scenes: dissociating importance from salience

    PubMed Central

    't Hart, Bernard M.; Schmidt, Hannah C. E. F.; Roth, Christine; Einhäuser, Wolfgang

    2013-01-01

    The relation of selective attention to understanding of natural scenes has been subject to intense behavioral research and computational modeling, and gaze is often used as a proxy for such attention. The probability of an image region to be fixated typically correlates with its contrast. However, this relation does not imply a causal role of contrast. Rather, contrast may relate to an object's “importance” for a scene, which in turn drives attention. Here we operationalize importance by the probability that an observer names the object as characteristic for a scene. We modify luminance contrast of either a frequently named (“common”/“important”) or a rarely named (“rare”/“unimportant”) object, track the observers' eye movements during scene viewing and ask them to provide keywords describing the scene immediately after. When no object is modified relative to the background, important objects draw more fixations than unimportant ones. Increases of contrast make an object more likely to be fixated, irrespective of whether it was important for the original scene, while decreases in contrast have little effect on fixations. Any contrast modification makes originally unimportant objects more important for the scene. Finally, important objects are fixated more centrally than unimportant objects, irrespective of contrast. Our data suggest a dissociation between object importance (relevance for the scene) and salience (relevance for attention). If an object obeys natural scene statistics, important objects are also salient. However, when natural scene statistics are violated, importance and salience are differentially affected. Object salience is modulated by the expectation about object properties (e.g., formed by context or gist), and importance by the violation of such expectations. In addition, the dependence of fixated locations within an object on the object's importance suggests an analogy to the effects of word frequency on landing positions in reading. PMID:23882251

  9. Suppression of spontaneous nystagmus during different visual fixation conditions.

    PubMed

    Hirvonen, Timo P; Juhola, Martti; Aalto, Heikki

    2012-07-01

    Analysis of spontaneous nystagmus is important in the evaluation of dizzy patients. The aim was to measure how different visual conditions affect the properties of nystagmus using three-dimensional video-oculography (VOG). We compared prevalence, frequency and slow phase velocity (SPV) of the spontaneous nystagmus with gaze fixation allowed, with Frenzel's glasses, and in total darkness. Twenty-five patients (35 measurements) with the peripheral vestibular pathologies were included. The prevalence of nystagmus with the gaze fixation was 40%, and it increased significantly to 66% with Frenzel's glasses and regular room lights on (p < 0.01). The prevalence increased significantly to 83% when the regular room lights were switched off (p = 0.014), and further to 100% in total darkness (p = 0.025). The mean SPV of nystagmus with visual fixation allowed was 1.0°/s. It increased to 2.4°/s with Frenzel's glasses and room lights on, and additionally to 3.1°/s, when the regular room lights were switched off. The mean SPV in total darkness was 6.9°/s. The difference was highly significant between all test conditions (p < 0.01). The frequency of nystagmus was 0.7 beats/s with gaze fixation, 0.8 beats/s in both the test conditions with Frenzel's glasses on, and 1.2 beats/s in total darkness. The frequency in total darkness was significantly higher (p < 0.05) than with Frenzel's glasses, and more so than with visual fixation (p = 0.003). The VOG in total darkness is superior in detecting nystagmus, since Frenzel's glasses allow visual suppression to happen, and this effect is reinforced with gaze fixation allowed. Strict control of visual surroundings is essential in interpreting peripheral nystagmus. PMID:22057154

  10. Fatigue strength of common tibial intramedullary nail distal locking screws

    Microsoft Academic Search

    Lanny V. Griffin; Robert M Harris; Joseph J Zubak

    2009-01-01

    BACKGROUND: Premature failure of either the nail and\\/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision

  11. Screw dislocation in zirconium: an ab initio study Emmanuel Clouet

    E-print Network

    Paris-Sud XI, Université de

    Screw dislocation in zirconium: an ab initio study Emmanuel Clouet CEA, DEN, Service de Recherches in zirconium is controlled by 1/3 1¯210 screw dislocations gliding in the prism planes of the hexagonal close zirconium and is known to be related to the number of valence electrons in the d band. We use ab initio

  12. Accuracy analysis of SCARA industrial robot based on screw theory

    Microsoft Academic Search

    Zhao Liang; Su Meng; Diao Changkun

    2011-01-01

    Based on an analysis of error sources of industrial robots, we build a pose error model of industrial robots with screw theory, which overcomes the defect that the error on the y-axis could not be reflected by the classical D-H parameter method. Given the error sources which influence the end- executor's accuracy, we established a screw representation of the static

  13. Manufacturing of the composite screw rotors by resin transfer molding

    Microsoft Academic Search

    Young Goo Kim; Dai Gil Lee; Park Kyoun Oh

    1995-01-01

    A screw-type pump with at least two rotors that are composed of male and female rotors with helical extending lands and grooves is increasingly used because it has a smaller weight to power ratio and produces less noise and vibration compared to conventional reciprocating pumps.Most male and female rotors of the screw type pump have been manufactured by machining. The

  14. A simple method to ensure proper screw position and plate size selection using the Morscher cervical spine locking plate. Technical note.

    PubMed

    Ball, P A; Benzel, E C; Baldwin, N G

    1994-04-01

    The use of bone plate instrumentation with screw fixation has proved to be a useful adjunctive measure in anterior cervical spine fusion surgery. Proper fitting, positioning, and attachment of this instrumentation have been shown to be frequently suboptimal if done without radiographic guidance. The most commonly used method of radiographic assistance for placement of this instrumentation is fluoroscopy. While this gives satisfactory technical results, it is expensive and time-consuming, and exposes the patient and the operating room personnel to ionizing radiation. The authors present a simple technique to ensure screw placement and plate fitting using Kirschner wires and a single lateral radiograph. This technique saves time, reduces exposure to radiation, and has led to satisfactory results in over 20 operative cases. PMID:8151358

  15. Outcome of double bundle anterior cruciate ligament reconstruction using crosspin and aperture fixation

    PubMed Central

    Joshi, Deepak; Jain, Vineet; Goyal, Ankit; Bahl, Vibhu; Modi, Prashant; Chaudhary, Deepak

    2014-01-01

    Background: Double bundle anterior cruciate ligament (DBACL) reconstruction is said to reproduce the native anterior cruciate ligament (ACL) anatomy better than single bundle anterior cruciate ligament, whether it leads to better functional results is debatable. Different fixation methods have been used for DBACL reconstruction, the most common being aperture fixation on tibial side and cortical suspensory fixation on the femoral side. We present the results of DBACL reconstruction technique, wherein on the femoral side anteromedial (AM) bundle is fixed with a crosspin and aperture fixation was done for the posterolateral (PL) bundle. Materials and Methods: Out of 157 isolated ACL injury patients who underwent ACL reconstruction, 100 were included in the prospective study. Arthroscopic DBACL reconstruction was done using ipsilateral hamstring autograft. AM bundle was fixed using Transfix (Arthrex, Naples, FL, USA) on the femoral side and bio interference screw (Arthrex, Naples, FL, USA) on the tibial side. PL bundle was fixed on femoral as well as on tibial side with a biointerference screw. Patients were evaluated using KT-1000 arthrometer, Lysholm score, International Knee Documentation Committee (IKDC) Score and isokinetic muscle strength testing. Methods: Out of 157 isolated ACL injury patients who underwent ACL reconstruction, 100 were included in the prospective study. Arthroscopic DBACL reconstruction was done using ipsilateral hamstring autograft. AM bundle was fixed using Transfix (Arthrex, Naples, FL, USA) on the femoral side and bio interference screw (Arthrex, Naples, FL, USA) on the tibial side. PL bundle was fixed on femoral as well as on tibial side with a biointerference screw. Patients were evaluated using KT-1000 arthrometer, Lysholm score, International Knee Documentation Committee (IKDC) Score and isokinetic muscle strength testing. Results: The KT-1000 results were evaluated using paired t test with the P value set at 0.001. At the end of 1 year, the anteroposterior side to side translation difference (KT-1000 manual maximum) showed mean improvement from 5.1 mm ± 1.5 preoperatively to 1.6 mm ± 1.2 (P < 0.001) postoperatively. The Lysholm score too showed statistically significant (P < 0.001) improvement from 52.4 ± 15.2 (range: 32-76) preoperatively to a postoperative score of 89.1 ± 3.2 (range 67-100). According to the IKDC score 90% patients had normal results (Category A and B). The AM femoral tunnel initial posterior blow out was seen in 4 patients and confluence in the intraarticular part of the femoral tunnels was seen in 6 patients intraoperatively. The quadriceps strength on isokinetic testing had an average deficit of 10.3% while the hamstrings had a 5.2% deficit at the end of 1 year as compared with the normal side. Conclusion: Our study revealed that the DBACL reconstruction using crosspin fixation for AM bundle and aperture fixation for PL bundle on the femoral side resulted in significant improvement in KT 1000, Lysholm and IKDC scores. PMID:24600062

  16. Screw dislocations in GaN

    SciTech Connect

    Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack; O'Keefe, Michael A.

    2002-02-15

    GaN has received much attention over the past few years because of several new applications, including light emitting diodes, blue laser diodes and high-power microwave transistors. One of the biggest problems is a high density of structural defects, mostly dislocations, due to a lack of a suitable lattice-matched substrate since bulk GaN is difficult to grow in large sizes. Transmission Electron Microscopy (TEM) has been applied to study defects in plan-view and cross-sections on samples prepared by conventional techniques such as mechanical thinning and precision ion milling. The density of dislocations close to the sample surface of a 1 mm-thick HVPE sample was in the range of 3x109 cm-2. All three types of dislocations were present in these samples, and almost 50 percent were screw dislocations. Our studies suggest that the core structure of screw dislocations in the same material might differ when the material is grown by different methods.

  17. Glutaraldehyde fixation revisited.

    PubMed

    Nimni, M E

    2001-01-01

    Our ability to stabilize animal heart valves and to manufacture equivalent prostheses using collagenous tissues has proven to be of significant value to large number of patients over the last 30 years. Such tissue-derived bioprostheses are being gradually improved by modifications of design and slight changes in the processing of the tissues from which they originate. Nevertheless their durability does not seem to have significantly improved, and some of their drawbacks, such as their propensity to calcify, have not been eliminated. Because of this children are excluded from receiving such implants. Enhancing such structures using cells from various sources or with the aid of growth factors does not seem likely to succeed because such inert matrices are not compatible with growth and remodeling. On the other hand, stabilizing these structures by means of novel crosslinking approaches, the addition of "plasticizing" molecules, or the addition of covalently bound residues that inhibit the growth of mineral deposits, could prove to be practical ways of improving such devices. PMID:11921661

  18. Lateral Movement of Screw Dislocations During Homoepitaxial Growth and Devices Yielded Therefrom Free of the Detrimental Effects of Screw Dislocations

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

    2004-01-01

    The present invention is related to a method that enables and improves wide bandgap homoepitaxial layers to be grown on axis single crystal substrates, particularly SiC. The lateral positions of the screw dislocations in epitaxial layers are predetermined instead of random, which allows devices to be reproducibly patterned to avoid performance degrading crystal defects normally created by screw dislocations.

  19. Salvage of failed osteosynthesis of an intracapsular fracture of the femoral neck using two cannulated compression screws and a vascularised iliac crest bone graft.

    PubMed

    Xiaobing, Y; Dewei, Z

    2015-07-01

    We evaluated the outcome of treatment of nonunion of an intracapsular fracture of the femoral neck in young patients using two cannulated screws and a vascularised bone graft. A total of 32 patients (15 women and 17 men, with a mean age of 36.5 years; 20 to 50) with failed internal fixation of an intracapsular fracture were included in the study. Following removal of the primary fixation, two cannulated compression screws were inserted with a vascularised iliac crest bone graft based on the ascending branch of the lateral femoral circumflex artery. At a mean follow-up of 6.8 years (4 to 10), union was achieved in 27 hips (84%). A total of five patients with a mean age of 40.5 years (35 to 50) had a persistent nonunion and underwent total hip arthroplasty as also did two patients whose fracture united but who developed osteonecrosis of the femoral head two years post-operatively. Statistical analysis showed that younger patients achieved earlier and more reliable union (p < 0.001). The functional outcome, as assessed by the Harris Hip score, was better in patients aged < 45 years compared with those aged > 45 years (p < 0.001). These findings suggest that further fixation using two cannulated compression screws and a vascularised iliac crest bone graft is an effective salvage treatment in patients aged < 45 years, in whom osteosynthesis of a displaced intracapsular fractures of the femoral neck has failed. Cite this article: Bone Joint J 2015; 97-B:988-91. PMID:26130357

  20. Clinical application of a new plate fixation system in open-door laminoplasty.

    PubMed

    Jiang, Liangjun; Chen, Weishan; Chen, Qixin; Xu, Kan; Wu, Qionghua; Li, Fangcai

    2012-02-01

    The purpose of this retrospective clinical series was to evaluate the benefits and complications of plate fixation for open-door laminoplasty in cervical spondylotic myelopathy with multilevel spinal stenosis compared with open-door laminoplasty without fixation. Forty-nine patients underwent open-door laminoplasty for cervical myelopathy with multilevel spinal stenosis with at least 13 months of follow-up. A plate was used as the sole method of fixation between the lateral mass and lamina with 3 screws. Computed tomography scans obtained pre- and postoperatively were assessed for plate complications and spinal canal enlargement. Pre- and postoperative neurological condition was assessed by the Japanese Orthopedic Association (JOA) myelopathy score. Overall cervical spine range of motion (ROM) was measured in full flexion and extension radiographs pre- and postoperatively. No restenosis due to door reclosure was noted, and no plates failed. No screws were backed out or broken. Almost all patients showed neurological improvement. The JOA score increased by 3.9±0.7 points in the suture group and 4.3±0.8 points in the plate group (P>.05). The postoperative increase in mean anteroposterior diameter of the spinal canal from C3 to C7 was 4.5±0.6 mm in the suture group and 5.1±0.5 mm in the plate group. The greater mean anteroposterior diameter increase in the plate group was statistically significant (P<.01). The mean cervical ROM decreased in the plate and suture groups postoperatively (P<.001). No significant difference was found in mean cervical ROM reduction between the groups (P>.05). No difference in axial symptoms was found between the 2 groups. PMID:22310411

  1. Machining of a bioactive nanocomposite orthopedic fixation device.

    PubMed

    Sparnell, Amie; Aniket; El-Ghannam, Ahmed

    2012-08-01

    Bioactive ceramics bond to bone and enhance bone formation. However, they have poor mechanical properties which restrict their machinability as well as their application as load bearing implants. The goal of this study was to machine bioactive fixation screws using a silica-calcium phosphate nanocomposite (SCPC50). The effect of compact pressure, holding time, and thermal treatment on the microstructure, machinability, and mechanical properties of SCPC50 cylinders were investigated. Samples prepared by powder metallurgy technique at compact pressure range of 100-300 MPa and treated at 900°C/1 h scored a poor machinability rating of (1/5) due to the significant formation of amorphous silicate phase at the grain boundaries. On the other hand, lowering of compact pressure and sintering temperature to 30 MPa/3 h and 700°C/2 h, respectively, minimized the formation of the amorphous phase and raised the machinability rating to (5/5). The modulus of elasticity and ultimate strength of machinable SCPC50 were 10.8 ± 2.0 GPa and 72.8 ± 22.8 MPa, respectively, which are comparable to the corresponding values for adult human cortical bone. qRT-PCR analyses showed that bone cells attached to SCPC50 significantly upregulated osteocalcin mRNA expression as compared to the cells on Ti-6Al-4V. Moreover, cells attached to SCPC50 produced mineralized bone-like tissue within 8 days. On the other hand, cells attached to Ti-6Al-4V failed to produce bone mineral under the same experimental conditions. Results of the study suggest that machinable SCPC50 has the potential to serve as an attractive new material for orthopedic fixation devices. PMID:22692822

  2. High potential of nitrogen fixation in pristine, ombrotrophic bogs in Southern Patagonia

    NASA Astrophysics Data System (ADS)

    Knorr, Klaus-Holger; Horn, Marcus A.; Bahamonde Aguilar, Nelson A.; Borken, Werner

    2015-04-01

    Nitrogen (N) input in pristine peatlands occurs via natural input of inorganic N through atmospheric deposition or biological dinitrogen (N2) fixation. However, N2 fixation is to date mostly attributed to bacteria and algae associated to Sphagnum and its contribution to plant productivity and peat buildup has been often underestimated in previous studies. Based on net N storage, exceptionally low N deposition, and high abundance of vascular plants at pristine peatlands in Southern Patagonia, we hypothesized that there must be a high potential of non-symbiotic N2 fixation not limited to the occurrence of Sphagnum. To this end, we chose two ombrotrophic bogs with spots that are dominated either by Sphagnum or by vascular, cushion-forming plants and sampled peat from different depths for incubation with 15N2 to determine N2 fixation potentials. Moreover, we analyzed 15N2 fixation by a nodule-forming, endemic conifer inhabiting the peatlands. Results from 15N2 uptake were compared to the conventional approach to study N2 fixation by the acetylene reduction assay (ARA). Using 15N2 as a tracer, high non-symbiotic N2 fixation rates of 0.3-1.4 ?mol N g-1 d-1 were found down to 50 cm under micro-oxic conditions (2 vol.%) in samples from both plots either covered by Sphagnum magellanicum or by vascular cushion plants. Peat N concentrations suggested a higher potential of non-symbiotic N2 fixation under cushion plants, likely because of the availability of easily decomposable organic compounds as substrates and oxic conditions in the rhizosphere. In the Sphagnum plots, high N2 fixation below 10 cm depth would rather reflect a potential fixation that may switch on during periods of low water levels when oxygen penetrates deeper into the peat. 15N natural abundance of live Sphagnum from 0-10 cm pointed to N uptake solely from atmospheric deposition and non-symbiotic N2 fixation. 15N signatures of peat from the cushion plant plots indicated additional N supply from N mineralization. Nitrogen fixation by the conifer Lepidothamnus fonkii was exceptionally high, reaching 3.1 ?mol N g-1 d.w. d-1 detected in roots, stems, and green biomass. For L. fonkii, we could identify a specific association with Beijerinckiaceae as N2 fixing bacteria in the root nodules, whereas the rhizosphere peat was dominated by other diazotrophs. The ARA considerably underestimated N2 fixation and can thus not be recommended for peatland studies. Our findings suggest that non-symbiotic or associative N2 fixation overcomes N deficiency in different vegetation communities and has great significance for N cycling and peat accumulation in pristine peatlands.

  3. Atomistic studies of jogged screw dislocations in {gamma}-TiAl alloys

    SciTech Connect

    Chen, K.Y.; Li, M.; Zhou, S.J.

    1999-03-01

    The behavior of jogged screw dislocations in {gamma}-TiAl alloys has been investigated with large-scale molecular dynamics (MD) simulations. The authors find a new mechanism for formation of pinning points in jogged screw dislocations. They also find that the critical height for the jogs in the {+-}[{bar 1}10] directions on the (001) plane to move nonconservatively is between 3r{sub 0} and 4r{sub 0}, where r{sub 0} is the nearest neighbor distance of aluminum atoms. Interstitials and vacancies are created during the nonconservative motions of the jogs. In addition, the formation of dislocation dipole and loops around the jogs is also observed.

  4. Validation of discrete element simulations in the field of solids conveying in single-screw extruders

    NASA Astrophysics Data System (ADS)

    Lessmann, Johann-Sebastian; Schoeppner, Volker

    2015-05-01

    This paper deals with possibilities to validate DEM simulations in the solids conveying zone of single-screw extruders. Apart from determining coefficients of friction, the representation of the pellets' shape is crucial. On the basis of DEM simulations of the bulk density within the screw channel, it is shown that most common plastic pellets can be represented adequately by combining two spheres. Additionally, simulations of the feed opening's pellet flow during a solids conveying process are conducted and validated by comparisons with experimental studies. Good conformity is obtained if the pellets are represented by several spheres as described above. Furthermore, the throughput of simulations and experiments is compared, also yielding good conformity. All the mentioned solids conveying simulations have so far been conducted without pressure build-up. To obtain an initial indication of the situation when pressure build-up is taken into account, simulations and experimental compression tests were also conducted.

  5. Impacts of Fertilization on Rates of Autotrophic N2 Fixation in Salt Marshes and Cranberry Bogs of Massachusetts

    E-print Network

    Vallino, Joseph J.

    Impacts of Fertilization on Rates of Autotrophic N2 Fixation in Salt Marshes and Cranberry Bogs fixation in salt marshes and cranberry bogs of MA. I measured pools of NH4, NO3, and PO4, in addition to total C and N content of the soils of salt marshes and cranberry bogs, each under two different

  6. N 2 fixation in three perennial Trifolium species in experimental grasslands of varied plant species richness and composition

    Microsoft Academic Search

    Georg Carlsson; Cecilia Palmborg; Ari Jumpponen; Michael Scherer-Lorenzen; Peter Högberg; Kerstin Huss-Danell

    2009-01-01

    This study is the first to investigate quantitative effects of plant community composition and diversity on N2 fixation in legumes. N2 fixation in three perennial Trifolium species grown in field plots with varied number of neighbouring species was evaluated with the 15N natural abundance method (two field sites, several growing seasons, no N addition) and the isotope dilution method (one

  7. Salvaging the pullout strength of stripped screws in osteoporotic bone.

    PubMed

    Pechon, Pierre H M; Mears, Simon C; Langdale, Evan R; Belkoff, Stephen M

    2013-06-01

    Our goal was to determine whether the pullout strength of stripped screw holes in osteoporotic bone could be increased with readily available materials from the operating room. We inserted 3.5-mm stainless steel nonlocking self-tapping cortical screws bicortically into 5 osteoporotic humeri. Each screw was first stripped by rotating it 1 full turn past maximum torque. In the control group, the screw was pulled out using an MTS machine (858; MTS Inc, Eden Prairie, Minnesota). In the treatment groups, the screw was removed, the hole was augmented with 1 of the 3 materials (stainless steel wire, polysorb suture, or polyethylene terephthalate glycol plastic sheet), and the screws were replaced and then pulled out. The effect of material on pullout strength was checked for significance (P < .05) using a general linearized latent and mixed model (Stata10; StataCorp, College Station, Texas). The mean (95% confidence interval) pullout strength for the unaugmented hole was 138 N (range 88-189), whereas the holes augmented with plastic, suture, or wire had mean pullout strengths of 255 N (range 177-333), 228 N (range 149-308), and 396 N (range 244-548), respectively. Although wire augmentation resulted in pullout strength that was significantly greater than that of the unaugmented screw, it was still below that of the intact construct. PMID:24093076

  8. Salvaging the Pullout Strength of Stripped Screws in Osteoporotic Bone

    PubMed Central

    Pechon, Pierre H. M.; Mears, Simon C.; Langdale, Evan R.; Belkoff, Stephen M.

    2013-01-01

    Our goal was to determine whether the pullout strength of stripped screw holes in osteoporotic bone could be increased with readily available materials from the operating room. We inserted 3.5-mm stainless steel nonlocking self-tapping cortical screws bicortically into 5 osteoporotic humeri. Each screw was first stripped by rotating it 1 full turn past maximum torque. In the control group, the screw was pulled out using an MTS machine (858; MTS Inc, Eden Prairie, Minnesota). In the treatment groups, the screw was removed, the hole was augmented with 1 of the 3 materials (stainless steel wire, polysorb suture, or polyethylene terephthalate glycol plastic sheet), and the screws were replaced and then pulled out. The effect of material on pullout strength was checked for significance (P < .05) using a general linearized latent and mixed model (Stata10; StataCorp, College Station, Texas). The mean (95% confidence interval) pullout strength for the unaugmented hole was 138 N (range 88-189), whereas the holes augmented with plastic, suture, or wire had mean pullout strengths of 255 N (range 177-333), 228 N (range 149-308), and 396 N (range 244-548), respectively. Although wire augmentation resulted in pullout strength that was significantly greater than that of the unaugmented screw, it was still below that of the intact construct. PMID:24093076

  9. Sacrospinous ligament fixation for vaginal vault prolapse

    Microsoft Academic Search

    T. Lantzsch; C. Goepel; M. Wolters; H. Koelbl; H. D. Methfessel

    2001-01-01

    Introduction. To assess intra- and postoperative complications and to look for long term follow-up results in women with sacrospinous ligament\\u000a fixation. Methods. Between 1988 and 1999, 200 women (mean age 59.8 years, range 33 to 83 years) underwent vaginal unilateral sacrospinous ligament\\u000a fixation. 172 patients had had prior hysterectomy. In 28 patients concomitant hysterectomy and sacrospinous ligament fixation\\u000a was performed.

  10. Helical screw rheometer: a new concept in rotational rheometry

    SciTech Connect

    Kraynik, A.M.; Aubert, J.H.; Chapman, R.N.; Gyure, D.C.

    1984-01-01

    The helical screw rheometer represents a new concept in viscometry: a rotational instrument that generates a pressure difference and therefore does not require torque measurement. The device is basically a metering screw that operates with no discharge. The results that are necessary to obtain the power-law constitutive parameters from pressure drop and rotation rate data are presented along with comparisons between theory and experiment for a prototype instrument operated at ambient conditions. The helical screw rheometer may offer advantages over conventional instruments for: 1) high-pressure measurements, 2) chemically-reacting fluids, 3) heterogeneous fluids and 4) on-line measurements.

  11. Analysis of Material Flow in Screw Extrusion of Aluminum

    SciTech Connect

    Haugen, Bjoern; Oernskar, Magnus; Welo, Torgeir; Wideroee, Fredrik [Department of Engineering Design and Materials, NTNU (Norway)

    2010-06-15

    Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process.The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes equations. Aluminum material properties are modeled using the Zener-Holloman material model. Effects of stick-slip conditions are investigated with respect to pressure build up and mixing quality of the extrusion process.The numerical results are compared with physical experiments using an experimental screw extruder.

  12. Noninvasive method for retrieval of broken dental implant abutment screw.

    PubMed

    Gooty, Jagadish Reddy; Palakuru, Sunil Kumar; Guntakalla, Vikram Reddy; Nera, Mahipal

    2014-04-01

    Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants. PMID:24963261

  13. Optically driven Archimedes micro-screws for micropump applications: multiple blade design

    NASA Astrophysics Data System (ADS)

    Baldeck, Patrice L.; Lin, Chih-Lang; Lin, Yu-Sheng; Lin, Chin-Te; Chung, Tien-Tung; Bouriau, Michel; Vitrant, Guy

    2011-10-01

    We study the rotation of photo-driven Archimedes screw with multiple blades. The micron-sized Archimedes screws are readily made by the two-photon polymerization technique. Free-floating screws that are trapped by optical tweezers align in the laser irradiation direction, and rotate spontaneously. In this study we demonstrate that the rotation speeds of two-blade-screws is twice the rotation speed of one-blade-screw. However, more complex 3-blade-screws rotate slower than 2-blade-screws due to their limited geometry resolution at this micron scale.

  14. Modeling fixation locations using spatial point processes.

    PubMed

    Barthelmé, Simon; Trukenbrod, Hans; Engbert, Ralf; Wichmann, Felix

    2013-01-01

    Whenever eye movements are measured, a central part of the analysis has to do with where subjects fixate and why they fixated where they fixated. To a first approximation, a set of fixations can be viewed as a set of points in space; this implies that fixations are spatial data and that the analysis of fixation locations can be beneficially thought of as a spatial statistics problem. We argue that thinking of fixation locations as arising from point processes is a very fruitful framework for eye-movement data, helping turn qualitative questions into quantitative ones. We provide a tutorial introduction to some of the main ideas of the field of spatial statistics, focusing especially on spatial Poisson processes. We show how point processes help relate image properties to fixation locations. In particular we show how point processes naturally express the idea that image features' predictability for fixations may vary from one image to another. We review other methods of analysis used in the literature, show how they relate to point process theory, and argue that thinking in terms of point processes substantially extends the range of analyses that can be performed and clarify their interpretation. PMID:24084942

  15. PERIODATE-LYSINE-PARAFORMALDEHYDE FIXATIVE A NEW FIXATIVE FOR IMMUNOELECTRON MICROSCOPY

    Microsoft Academic Search

    PAUL K. NAKANE

    A new fixative which primarily stabilizes carbohydrate moieties was developed for immunoelectron microscopy. It contains periodate, lysine and paraformaldehyde. Theoreti- cally, the carbohydrates are oxidized by periodate and cross-linked by lysine. The fixative can preserve antigenicity as well as paraformaldehyde and ultrastructure as well as glutaraldehyde. Using this fixative and the peroxidase-labeled antibody technique, base- ment membrane antigen was localized

  16. Nitrogen fixation method and apparatus

    DOEpatents

    Chen, H.L.

    1983-08-16

    A method and apparatus for achieving nitrogen fixation includes a volumetric electric discharge chamber. The volumetric discharge chamber provides an even distribution of an electron beam, and enables the chamber to be maintained at a controlled energy to pressure (E/p) ratio. An E/p ratio of from 5 to 15 kV/atm of O[sub 2]/cm promotes the formation of vibrationally excited N[sub 2]. Atomic oxygen interacts with vibrationally excited N[sub 2] at a much quicker rate than unexcited N[sub 2], greatly improving the rate at which NO is formed. 1 fig.

  17. Nitrogen fixation method and apparatus

    DOEpatents

    Chen, Hao-Lin (Walnut Creek, CA)

    1983-01-01

    A method and apparatus for achieving nitrogen fixation includes a volumetric electric discharge chamber. The volumetric discharge chamber provides an even distribution of an electron beam, and enables the chamber to be maintained at a controlled energy to pressure (E/p) ratio. An E/p ratio of from 5 to 15 kV/atm of O.sub.2 /cm promotes the formation of vibrationally excited N.sub.2. Atomic oxygen interacts with vibrationally excited N.sub.2 at a much quicker rate than unexcited N.sub.2, greatly improving the rate at which NO is formed.

  18. A new approach to modeling the influence of image features on fixation selection in scenes

    PubMed Central

    Nuthmann, Antje; Einhäuser, Wolfgang

    2015-01-01

    Which image characteristics predict where people fixate when memorizing natural images? To answer this question, we introduce a new analysis approach that combines a novel scene-patch analysis with generalized linear mixed models (GLMMs). Our method allows for (1) directly describing the relationship between continuous feature value and fixation probability, and (2) assessing each feature's unique contribution to fixation selection. To demonstrate this method, we estimated the relative contribution of various image features to fixation selection: luminance and luminance contrast (low-level features); edge density (a mid-level feature); visual clutter and image segmentation to approximate local object density in the scene (higher-level features). An additional predictor captured the central bias of fixation. The GLMM results revealed that edge density, clutter, and the number of homogenous segments in a patch can independently predict whether image patches are fixated or not. Importantly, neither luminance nor contrast had an independent effect above and beyond what could be accounted for by the other predictors. Since the parcellation of the scene and the selection of features can be tailored to the specific research question, our approach allows for assessing the interplay of various factors relevant for fixation selection in scenes in a powerful and flexible manner. PMID:25752239

  19. A new approach to scaffold fixation by magnetic forces: Application to large osteochondral defects.

    PubMed

    Russo, Alessandro; Shelyakova, Tatiana; Casino, Daniela; Lopomo, Nicola; Strazzari, Alessandro; Ortolani, Alessandro; Visani, Andrea; Dediu, Valentin; Marcacci, Maurilio

    2012-11-01

    Scaffold fixation represents one of the most serious challenges in osteochondral defect surgery. Indeed, the fixation should firmly hold the scaffold in the implanted position as well as it should guaranty stable bone/scaffold interface for efficient tissue regeneration. Nonetheless successful results have been achieved for small defect repair, the fixation remains really problematic for large defects, i.e. defects with areas exceeding 2cm(2). This paper advances an innovative magnetic fixation approach based on application of magnetic scaffolds. Finite element modeling was exploited to investigate the fixation efficiency. We considered three magnetic configurations: (1) external permanent magnet ring placed around the leg near the joint; (2) four small permanent magnet pins implanted in the bone underlying the scaffold; (3) four similarly implanted stainless steel pins which magnetization was induced by the external magnet. It was found that for most appropriate magnetic materials and optimized magnet-scaffold positioning all the considered configurations provide a sufficient scaffold fixation. In addition to fixation, we analyzed the pressure induced by magnetic forces at the bone/scaffold interface. Such pressure is known to influence significantly the bone regeneration and could be used for magneto-mechanical stimulation. PMID:22381395

  20. Changes in North Atlantic nitrogen fixation controlled by ocean circulation.

    PubMed

    Straub, Marietta; Sigman, Daniel M; Ren, Haojia; Martínez-García, Alfredo; Meckler, A Nele; Hain, Mathis P; Haug, Gerald H

    2013-09-12

    In the ocean, the chemical forms of nitrogen that are readily available for biological use (known collectively as 'fixed' nitrogen) fuel the global phytoplankton productivity that exports carbon to the deep ocean. Accordingly, variation in the oceanic fixed nitrogen reservoir has been proposed as a cause of glacial-interglacial changes in atmospheric carbon dioxide concentration. Marine nitrogen fixation, which produces most of the ocean's fixed nitrogen, is thought to be affected by multiple factors, including ocean temperature and the availability of iron and phosphorus. Here we reconstruct changes in North Atlantic nitrogen fixation over the past 160,000?years from the shell-bound nitrogen isotope ratio ((15)N/(14)N) of planktonic foraminifera in Caribbean Sea sediments. The observed changes cannot be explained by reconstructed changes in temperature, the supply of (iron-bearing) dust or water column denitrification. We identify a strong, roughly 23,000-year cycle in nitrogen fixation and suggest that it is a response to orbitally driven changes in equatorial Atlantic upwelling, which imports 'excess' phosphorus (phosphorus in stoichiometric excess of fixed nitrogen) into the tropical North Atlantic surface. In addition, we find that nitrogen fixation was reduced during glacial stages 6 and 4, when North Atlantic Deep Water had shoaled to become glacial North Atlantic intermediate water, which isolated the Atlantic thermocline from excess phosphorus-rich mid-depth waters that today enter from the Southern Ocean. Although modern studies have yielded diverse views of the controls on nitrogen fixation, our palaeobiogeochemical data suggest that excess phosphorus is the master variable in the North Atlantic Ocean and indicate that the variations in its supply over the most recent glacial cycle were dominated by the response of regional ocean circulation to the orbital cycles. PMID:23965620

  1. Heterotrophic organisms dominate nitrogen fixation in the South Pacific Gyre.

    PubMed

    Halm, Hannah; Lam, Phyllis; Ferdelman, Timothy G; Lavik, Gaute; Dittmar, Thorsten; LaRoche, Julie; D'Hondt, Steven; Kuypers, Marcel M M

    2012-06-01

    Oceanic subtropical gyres are considered biological deserts because of the extremely low availability of nutrients and thus minimum productivities. The major source of nutrient nitrogen in these ecosystems is N(2)-fixation. The South Pacific Gyre (SPG) is the largest ocean gyre in the world, but measurements of N(2)-fixation therein, or identification of microorganisms involved, are scarce. In the 2006/2007 austral summer, we investigated nitrogen and carbon assimilation at 11 stations throughout the SPG. In the ultra-oligotrophic waters of the SPG, the chlorophyll maxima reached as deep as 200 m. Surface primary production seemed limited by nitrogen, as dissolved inorganic carbon uptake was stimulated upon additions of (15)N-labeled ammonium and leucine in our incubation experiments. N(2)-fixation was detectable throughout the upper 200 m at most stations, with rates ranging from 0.001 to 0.19 nM N h(-1). N(2)-fixation in the SPG may account for the production of 8-20% of global oceanic new nitrogen. Interestingly, comparable (15)N(2)-fixation rates were measured under light and dark conditions. Meanwhile, phylogenetic analyses for the functional gene biomarker nifH and its transcripts could not detect any common photoautotrophic diazotrophs, such as, Trichodesmium, but a prevalence of ?-proteobacteria and the unicellular photoheterotrophic Group A cyanobacteria. The dominance of these likely heterotrophic diazotrophs was further verified by quantitative PCR. Hence, our combined results show that the ultra-oligotrophic SPG harbors a hitherto unknown heterotrophic diazotrophic community, clearly distinct from other oceanic gyres previously visited. PMID:22170429

  2. Heterotrophic organisms dominate nitrogen fixation in the South Pacific Gyre

    PubMed Central

    Halm, Hannah; Lam, Phyllis; Ferdelman, Timothy G; Lavik, Gaute; Dittmar, Thorsten; LaRoche, Julie; D'Hondt, Steven; Kuypers, Marcel MM

    2012-01-01

    Oceanic subtropical gyres are considered biological deserts because of the extremely low availability of nutrients and thus minimum productivities. The major source of nutrient nitrogen in these ecosystems is N2-fixation. The South Pacific Gyre (SPG) is the largest ocean gyre in the world, but measurements of N2-fixation therein, or identification of microorganisms involved, are scarce. In the 2006/2007 austral summer, we investigated nitrogen and carbon assimilation at 11 stations throughout the SPG. In the ultra-oligotrophic waters of the SPG, the chlorophyll maxima reached as deep as 200?m. Surface primary production seemed limited by nitrogen, as dissolved inorganic carbon uptake was stimulated upon additions of 15N-labeled ammonium and leucine in our incubation experiments. N2-fixation was detectable throughout the upper 200?m at most stations, with rates ranging from 0.001 to 0.19?nM?N?h?1. N2-fixation in the SPG may account for the production of 8–20% of global oceanic new nitrogen. Interestingly, comparable 15N2-fixation rates were measured under light and dark conditions. Meanwhile, phylogenetic analyses for the functional gene biomarker nifH and its transcripts could not detect any common photoautotrophic diazotrophs, such as, Trichodesmium, but a prevalence of ?-proteobacteria and the unicellular photoheterotrophic Group A cyanobacteria. The dominance of these likely heterotrophic diazotrophs was further verified by quantitative PCR. Hence, our combined results show that the ultra-oligotrophic SPG harbors a hitherto unknown heterotrophic diazotrophic community, clearly distinct from other oceanic gyres previously visited. PMID:22170429

  3. Comminuted quadrilateral plate fracture fixation through the iliofemoral approach.

    PubMed

    Sen, Ramesh Kumar; Tripathy, Sujit Kumar; Aggarwal, Sameer; Goyal, Tarun; Mahapatra, Santosh Kumar

    2013-02-01

    Comminuted quadrilateral plate fracture with medial displacement is a technically difficult fracture to treat. Minimal bone stock, proximity to the hip joint with limited surgical access, and difficulty in obtaining a stable fixation at this area, contribute to the surgical challenge of open reduction and internal fixation. Fixation of a medial buttress plate in an infrapectineal fashion is a well-described technique to address such fractures. However, this plate alone may be inadequate to buttress all the fragments in a grossly comminuted quadrilateral plate fracture. An additional spring plate is often placed underneath the infrapectineal plate to hold the fracture fragments. Conventionally, these spring plates are fixed to the ilium superiorly while the other end buttresses the quadrilateral plate when placed underneath the infrapectineal reconstruction plate. The standard ilioinguinal approach and modified Stoppa approach have been described for the surgical access to the quadrilateral plate. Both the approaches have some limitations in addressing quadrilateral plate fracture. The ilioinguinal approach requires extensive dissection and mobilisation of inguinal neurovascular bundle. The modified Stoppa approach does not permit visualisation of the entire anterior column and the hip joint. The authors, in this article, describe the fixation of the comminuted quadrilateral plate fracture through the iliofemoral approach combined with a medial ilioinguinal window. The technique involves fixation of a spring plate (Allis T-plate) at right angle to the infrapectineal buttress plate (90°-90° plate construct). The vertical limb of the T-plate is fixed to the iliopectineal eminence whereas the horizontal limb buttresses the quadrilateral plate Hence, this technique addresses fractures of both the iliopectineal eminence and the quadrilateral plate. Other than that, the iliofemoral approach permits direct visualisation of the entire anterior column and the hip joint without the necessity to dissect the ilioinguinal neurovascular structures. PMID:23199759

  4. 21 CFR 868.5770 - Tracheal tube fixation device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Tracheal tube fixation device. 868.5770 Section...Therapeutic Devices § 868.5770 Tracheal tube fixation device. (a) Identification. A tracheal tube fixation device is a device used to...

  5. 21 CFR 868.5770 - Tracheal tube fixation device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Tracheal tube fixation device. 868.5770 Section...Therapeutic Devices § 868.5770 Tracheal tube fixation device. (a) Identification. A tracheal tube fixation device is a device used to...

  6. 21 CFR 868.5770 - Tracheal tube fixation device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Tracheal tube fixation device. 868.5770 Section...Therapeutic Devices § 868.5770 Tracheal tube fixation device. (a) Identification. A tracheal tube fixation device is a device used to...

  7. 21 CFR 868.5770 - Tracheal tube fixation device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Tracheal tube fixation device. 868.5770 Section...Therapeutic Devices § 868.5770 Tracheal tube fixation device. (a) Identification. A tracheal tube fixation device is a device used to...

  8. 21 CFR 868.5770 - Tracheal tube fixation device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Tracheal tube fixation device. 868.5770 Section...Therapeutic Devices § 868.5770 Tracheal tube fixation device. (a) Identification. A tracheal tube fixation device is a device used to...

  9. 21 CFR 888.3060 - Spinal intervertebral body fixation orthosis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...Spinal intervertebral body fixation orthosis. 888.3060 Section 888.3060...Spinal intervertebral body fixation orthosis. (a) Identification. A spinal intervertebral body fixation orthosis is a device intended to...

  10. 21 CFR 888.3060 - Spinal intervertebral body fixation orthosis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...Spinal intervertebral body fixation orthosis. 888.3060 Section 888.3060...Spinal intervertebral body fixation orthosis. (a) Identification. A spinal intervertebral body fixation orthosis is a device intended to...

  11. 21 CFR 888.3050 - Spinal interlaminal fixation orthosis.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...false Spinal interlaminal fixation orthosis. 888.3050 Section 888.3050...3050 Spinal interlaminal fixation orthosis. (a) Identification. A spinal interlaminal fixation orthosis is a device intended to...

  12. 21 CFR 888.3050 - Spinal interlaminal fixation orthosis.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...false Spinal interlaminal fixation orthosis. 888.3050 Section 888.3050...3050 Spinal interlaminal fixation orthosis. (a) Identification. A spinal interlaminal fixation orthosis is a device intended to...

  13. A Screw -Theoretic Framework for Musculoskeletal System Modeling and Analysis

    E-print Network

    Krovi, Venkat

    A Screw -Theoretic Framework for Musculoskeletal System Modeling and Analysis by Michael J. Del of tools for musculoskeletal system analysis, leveraging methodologies which have revolutionized can model, simulate, and analyze a redundant musculoskeletal system with (i) an adequate degree

  14. Screw anchors economically control pipeline buoyancy in muskeg

    SciTech Connect

    Robertson, R.; Curle, R. [NOVA Gas Transmission Ltd., Calgary, Alberta (Canada)

    1995-04-24

    To control buoyancy of large-diameter pipelines that cross such wet areas as muskeg swamps in Alberta Province, Canada, NOVA Gas Transmission Ltd., Calgary, for more than 6 years investigated alternatives to traditional concrete weights. The company`s research indicated that helical screw anchors offer cost-effective buoyancy control for natural-gas pipelines 20-in. OD and larger. Muskegs are organic soils with high water tables, low shear strengths, and low densities (specific gravity of 1.04). NOVA`s experience demonstrated practical and cost benefits of screw anchors to resist uplift forces. And among other benefits, substitution of screw anchors for concrete weights significantly reduced the number of heavy trucks that must be moved across the muskeg. The paper discusses buoyancy control, pipeline adaptation, pipe stresses and corrosion, pipeline construction and screw-anchor installation, economics and other benefits.

  15. Wet-gas compression in twin-screw multiphase pumps 

    E-print Network

    Chan, Evan

    2009-05-15

    encountered when operating under conditions with high gas volume fractions (GVF). Twin-screw multiphase pumps experience a severe decrease in efficiency when operating under wet-gas conditions, GVF over 95%. Field operations have revealed severe vibration...

  16. Wet-gas compression in twin-screw multiphase pumps

    E-print Network

    Chan, Evan

    2009-05-15

    Multiphase pumping with twin-screw pumps is a relatively new technology that has been proven successful in a variety of field applications. By using these pumps to add energy to the combined gas and liquid wellstream with minimal separation...

  17. Screw-matrix method in dynamics of multibody systems

    NASA Astrophysics Data System (ADS)

    Yanzhu, Liu

    1988-05-01

    In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson/Wittenberg formalism. We can expand the application of the screw theory to the general case of multibody systems. For a tree system, the dynamical equations for each j-th subsystem, composed of all the outboard bodies connected by j-th joint can be formulated without the constraint reaction forces in the joints. For a nontree system, the dynamical equations of subsystems and the kinematical consistency conditions of the joints can be derived using the loop matrix. The whole process of calculation is unified in matrix form. A three-segment manipulator is discussed as an example.

  18. Unilateral fixation for treatment of occipitocervical instability in children with congenital vertebral anomalies of the craniocervical junction.

    PubMed

    Mazur, Marcus D; Ravindra, Vijay M; Brockmeyer, Douglas L

    2015-04-01

    OBJECT Patients with occipitocervical (OC) instability from congenital vertebral anomalies (CVAs) of the craniocervical junction (CCJ) often have bony abnormalities that make instrumentation placement difficult. Within this patient population, some bilateral instrumentation constructs either fail or are not feasible, and a unilateral construct must be used. The authors describe the surgical management and outcomes of this disorder in patients in whom unilateral fixation constructs were used to treat OC instability. METHODS From a database of OC fusion procedures, the authors identified patients who underwent unilateral fixation for the management of OC instability. Patient characteristics, surgical details, and radiographic outcomes were reviewed. In each patient, CT scans were performed at least 4 months after surgery to evaluate for fusion. RESULTS Eight patients with CVAs of the CCJ underwent unilateral fixation for the treatment of OC instability. For 4 patients, the procedure occurred after a bilateral OC construct failed or infection forced hardware removal. For the remainder, it was the primary procedure. Two patients required reoperation for hardware revision and 1 developed nonunion requiring revision of the bone graft. Ultimately, 7 patients demonstrated osseous fusion on CT scans and 1 had a stable fibrous union. CONCLUSIONS These findings demonstrate that a unilateral OC fixation is effective for the treatment of OC instability in children with CVAs of the CCJ in whom bilateral screw placement fails or is not feasible. PMID:25828503

  19. Monitoring the reduced scattering coefficient of bone tissues on the trajectory of pedicle screw placement using near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Yangyang; Wang, Yuyan; Qian, Zhiyu; Zhao, Jinzhe; Cao, Xinzhi; Li, Weitao

    2014-11-01

    Pedicle screw (PS) fixation has been widely used for spine diseases. Scientists and clinicians employ several approaches to navigate PS during operation. We have demonstrated the feasibility of monitoring the reduced scattering coefficient (?s?) on the trajectory of PS using near-infrared spectroscopy (NIRS). To perform the in-vitro monitoring, an NIRS measurement system was introduced and the reduced scattering coefficients of different sites in porcine pedicle were accurately deduced from the spectrum. Moreover, the changes of the reduced scattering coefficient along the different paths were studied. The results show reduced scattering coefficients on different regions of bones can be significantly distinguished. Furthermore, monitoring experiments along different paths confirmed that a reduced scattering coefficient would change versus the depth of puncture in pedicles. Thus, the proposed monitoring system based on NIRS provides a potential for guiding PS during operation.

  20. Numerical Synthesis of Overconstrained Mechanisms Based on Screw Theory

    Microsoft Academic Search

    René Bartkowiak; Christoph Woernle

    \\u000a An approach for the synthesis of overconstrained single-loop mechanisms with helical joints using screw theory is presented.\\u000a By expressing higher-order derivatives of the screw axes with respect to the joint coordinates a local approximation of the\\u000a closure conditions is obtained. The approximation is used to define conditions for the finite mobility of overconstrained\\u000a mechanisms.

  1. Design of Limb for Parallel Mechanism Based on Screw Theory

    Microsoft Academic Search

    Zhigang Lai; Lixin Li; Ping' an Liu

    2010-01-01

    \\u000a Based on the reciprocal relationship of twist and wrench in screw theory, the mathematical model for limb of parallel manipulator\\u000a is established in this paper. According to the motion modes of mobile platform (translation or rotation), we concluded the\\u000a geometric conditions which the prismatic joint or revolute joint must meet with by analyzing the constraint screw on the platform,\\u000a which

  2. Finite displacements of points, planes, and lines via screw theory

    Microsoft Academic Search

    I. A. Parkin

    1995-01-01

    Geometrical elements, namely point, directed plane, and directed line, are here taken in isolation from any rigid body to which they may belong. The available finite screws are fully determined for a general finite displacement of each element. Each screw carries a quasi-pitch, or “quatch”, that reduces to the commonly-accepted pitch when a displacement becomes infinitesimal. Each element-displacement has its

  3. Crystal geometry of screw dislocation glide in tungsten nanocrystals

    NASA Astrophysics Data System (ADS)

    Sadanov, E. V.

    2015-02-01

    A zigzag pattern of low-temperature dislocation glide occurring in tungsten nanocrystals in the intersecting planes {110} and {211}, which belong to the <111> crystallographic zone, has been revealed using field ion microscopy. It has been shown that cores of 1/2[111] screw dislocations are undissociated within the limits of the resolution of the field ion microscope. It has been found experimentally that surface atoms are displaced into metastable positions in the region of the trace of screw dislocation motion.

  4. Eighth international congress on nitrogen fixation. Final program

    SciTech Connect

    Not Available

    1990-12-31

    This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

  5. Backflow in twin-screw-type multiphase pump

    SciTech Connect

    Egashira, Kazuyuki; Shoda, Shinji; Tochikawa, Tetsuro [Japan National Oil Corp., Chiba (Japan); Furukawa, Akinori [Kyushu Univ. (Japan)

    1998-02-01

    The performance of a twin-screw-type multiphase pump was investigated from the viewpoints of backflow in a gap along the twin-screw shafts and of scaleup parameters. Although both the backflow and the scaleup parameters have been recognized as important factors in developing multiphase pumps, they have not yet been clarified. The twin-screw pump was equipped with pressure sensors, set in the multiphase-test facility, and experimented with under various conditions to clarify the relationship between backflow rates and factors such as differential pressure, gas-void fractions (GVF`s), and the rotation speed of the shaft. A physical model was proposed with the empirical relationship of pressure distribution along the screw, and was successfully associated with scaleup parameters, such as the geometrical data of the twin-screw pump. Then it was used successfully to simulate the backflow in twin-screw pumps on relatively broad experimental conditions, judging from the comparison between the model and the experimental data.

  6. Biochemical Approaches to Improved Nitrogen Fixation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improving symbiotic nitrogen fixation by legumes has emerged again as an important topic on the world scene due to the energy crisis and lack of access to nitrogen fertilizer in developing countries. We have taken a biochemical genomics approach to improving symbiotic nitrogen fixation in legumes. L...

  7. Bioabsorbable fixation in orthopaedic surgery and traumatology

    Microsoft Academic Search

    Pentti U Rokkanen; Ole Böstman; Eero Hirvensalo; E. Antero Mäkelä; Esa K Partio; Hannu Pätiälä; Seppo Vainionpää; Kimmo Vihtonen; Pertti Törmälä

    2000-01-01

    Bioabsorbable internal fixation devices were introduced clinically in the treatment of fractures and osteotomies of the extremities at the Department of Orthopaedics and Traumatology, Helsinki University, in 1984. Since November 5, 1984, a total of 3200 patients were managed using bone or ligament fixation devices made of self-reinforced (matrix and fibres of the same polymer) bioabsorbable alpha-hydroxy polyesters. The devices

  8. Whole Animal Perfusion Fixation for Rodents

    PubMed Central

    Gage, Gregory J.; Kipke, Daryl R.; Shain, William

    2012-01-01

    The goal of fixation is to rapidly and uniformly preserve tissue in a life-like state. While placing tissue directly in fixative works well for small pieces of tissue, larger specimens like the intact brain pose a problem for immersion fixation because the fixative does not reach all regions of the tissue at the same rate 5,7. Often, changes in response to hypoxia begin before the tissue can be preserved 12. The advantage of directly perfusing fixative through the circulatory system is that the chemical can quickly reach every corner of the organism using the natural vascular network. In order to utilize the circulatory system most effectively, care must be taken to match physiological pressures 3. It is important to note that physiological pressures are dependent on the species used. Techniques for perfusion fixation vary depending on the tissue to be fixed and how the tissue will be processed following fixation. In this video, we describe a low-cost, rapid, controlled and uniform fixation procedure using 4% paraformaldehyde perfused via the vascular system: through the heart of the rat to obtain the best possible preservation of the brain for immunohistochemistry. The main advantage of this technique (vs. gravity-fed systems) is that the circulatory system is utilized most effectively. PMID:22871843

  9. [Intrascleral haptic fixation of intraocular lenses].

    PubMed

    Scharioth, G B

    2014-03-01

    Scharioth's intrascleral haptic fixation in cases of no or insufficient capsular support has become a standardized and safe procedure for long-term fixation of intraocular lenses. The surgical technique is explained in detail. The postoperative results have demonstrated a low complication rate and a lack of contraindications for this technique. PMID:24549683

  10. Nitrogen fixation in Lake Mendota, Madison, Wisconsin

    Microsoft Academic Search

    MARGUERITE SHERMAN TORREY; G. F. LEE

    1976-01-01

    The cffccts of various environmental conditions, and of ccl1 composition, heterocyst con- tent, and nitrogen content of algal s'amples, on fixation of N, by colonial and filamentous algae in Lake Mendota were investigated. IIctcrocyst content and temperature were significantly and positively related to accty- lcnc recluction activity ( NB fixation); depth of sample collection was negatively related. Rvailablc data do

  11. In vivo quantification of the apical fixation forces of different mitral valved stent designs in the beating heart.

    PubMed

    Pokorny, S; Huenges, K; Engel, A; Gross, J; Frank, D; Morlock, M M; Cremer, J; Lutter, G

    2015-05-01

    The aim of this study was the quantification of the apical fixation forces of mitral valved stents for the first time. A test set-up was developed to measure the forces acting on the apical fixation of mitral valved stents. Twenty pigs received a self-expanding valved stent in the mitral position via a transapical approach in an off-pump procedure. Following stent deployment in the beating heart, the apical fixation forces were recorded following a standardized protocol and normalized. The apical fixation force of two different valved stent designs (AP: sole apical fixation, n = 10; SA: additional sub-annular fixation, n = 10) was compared to quantify the impact of the design change. Force measurement was successfully conducted in 18 of 20 animals (design AP: n = 10; design SA: n = 8). Evaluation showed higher mean forces and amplitude in the group with sole apical fixation (p = 0.046; Table 1). The impact of the additional sub-annular fixation was shown by a significant reduction of the force acting upon the apex of the heart. Quantification of these in vivo forces provides important information about the impact of different stent designs and might provide an objective parameter for stent performance evaluation in clinical application. PMID:25352439

  12. Fixation, processing, and immunochemical reagent effects on preservation of T-lymphocyte surface membrane antigens in paraffin-embedded tissue.

    PubMed

    Pollard, K; Lunny, D; Holgate, C S; Jackson, P; Bird, C C

    1987-11-01

    Fixatives, fixation additives, paraffin processing reagents, and immunochemical reagents were investigated for effects on preservation of T-lymphocyte surface membrane antigens CD3, CD4, and CD8 in human tonsil. Individual reagent effects were assessed in frozen sections by use of monoclonal antibodies and this information was used to optimize T-cell immunostaining in paraffin sections. Harmful factors were fixation delay, fixation at acid pH, fixation and processing at temperatures above 4 degrees C, hot paraffin wax, proteolytic enzymes, methanolic hydrogen peroxide, Triton X-100, and prolonged iodine treatment. Optimal T-cell demonstration in paraffin sections followed tissue fixation in periodate-lysine-paraformaldehyde dichromate at 4 degrees C, pH 7.5; processing through isopropanol, then xylene or chloroform, at 4 degrees C; and embedding in low melting point wax at 45-50 degrees C. Graded antigen stability occurred: CD3 most stable, CD8 least, and CD4 intermediate. CD4 and CD8 antigen preservation in paraffin sections required critical optimal tissue handling. CD3 was more stable and was also demonstrated in tissue fixed in commercial formalin, glutaraldehyde, and Bouin's fluid when fixation and processing conditions were optimized for pH and temperature. Of the fixation additives studied, polyethylene glycol and several potassium and magnesium salts enhanced immunostaining, whereas calcium chloride and lidocaine were deleterious. PMID:3309048

  13. [A comparative analysis of results of operative treatment of olecranon fracture utilizing Gruca screw and Weber girth].

    PubMed

    Bednarenko, Marcin; Kotela, Ireneusz; Bo?tu?, Witold; Jakubowski, Lukasz

    2006-01-01

    An injury to the elbow constitutes 3.5% of all injuries of the movement system and of these 31% concern olecranon fractures. In the majority of cases they are intra-articular fractures, unstable because of the action of the triceps muscle of the arm. Most of the patients require operative treatment. In the years 1984-2001 in the Traumatic and Orthopedic Ward we treated 49 patients with olecranon fractures. In 30 patient we utilized Gruca screw and in 10 of them Weber girth. 3 fractures were fixed with a wire loop and the remaining 6 did not require operative but only conservative treatment. The results were estimated according to the Hofbauer's scale in 37 patients among whom 27 were treated making a fixation with a Gruca screw and 10 by using Weber girth. Altogether, we achieved good and satisfactory results in 33 cases and bad results in 4 cases. Based on these results there is no evident superiority of one method over the other. The study emphasizes the importance of the correct qualification to either therapeutic method. PMID:17784540

  14. The prognostic value of tip-to-apex distance (TAD index) in intertrochanteric fractures fixed by dynamic hip screw

    PubMed Central

    Sedighi, Ali; Sales, Jafar Ganjpour; Alavi, Sahar

    2012-01-01

    Intertrochanteric fractures (ITFs) are the most common type of fractures requiring surgical intervention. They also have the highest surgical mortality among orthopedic operations. Among the many different techniques used for fixation of this type of fracture, use of the Dynamic Hip Screw (DHS) has gained wide acceptance. This current study was designed to assess positive predictive value of tip-to-apex distance (TAD) index in the prognosis of patients treated with DHS. The study was designed according to a descriptive-analytic protocol, made up of 100 cases of ITFs caused by falling, treated in the Shohada Orthopedic Center, Tabriz, Iran. All patients underwent lateral and antero-posterior hip X-ray to measure TAD index. The cohort was followed for three months after DHS placement. Of a total of 100 cases (53 male, 47 female) with a mean age of 76.7 years (range 29–100 years), 43% had grade 4, 29% grade 3, 21% grade 5, 5% grade 2 and 2% grade 6 osteoporosis. The screw position was postero-inferior in 57%, central in 40% and superior in 3% of patients. Minimum and maximum TAD index were 20 and 28 mm, respectively. Mean TAD was 23.5 mm. There were no post-operative complications in 84% of cases. Screw failure was the most common complication in the remaining 16% of patients. The study shows a statistically significant correlation between TAD index and cut-off rate in patients with intertrochanteric fractures of femoral bone treated by DHS. This validates the use of TAD index in determining the prognosis of patients treated by DHS. PMID:23589760

  15. Effect of screw position on single cycle to failure in bending and torsion of a locking plate-rod construct in a synthetic feline femoral gap model.

    PubMed

    Niederhäuser, Simone K; Tepic, Slobodan; Weber, Urs T

    2015-05-01

    OBJECTIVE To evaluate the effect of screw position on strength and stiffness of a combination locking plate-rod construct in a synthetic feline femoral gap model. SAMPLE 30 synthetic long-bone models derived from beechwood and balsa wood. PROCEDURES 3 constructs (2 locking plate-rod constructs and 1 locking plate construct; 10 specimens/construct) were tested in a diaphyseal bridge plating configuration by use of 4-point bending and torsion. Variables included screw position (near the fracture gap and far from the fracture gap) and application of an intramedullary pin. Constructs were tested to failure in each loading mode to determine strength and stiffness. Failure was defined as plastic deformation of the plate or breakage of the bone model or plate. Strength, yield angle, and stiffness were compared by use of a Wilcoxon test. RESULTS Placement of screws near the fracture gap did not increase bending or torsional stiffness in the locking plate-rod constructs, assuming the plate was placed on the tension side of the bone. Addition of an intramedullary pin resulted in a significant increase in bending strength of the construct. Screw positioning did not have a significant effect on any torsion variables. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study suggested that, in the investigated plate-rod construct, screw insertion adjacent to the fracture lacked mechanical advantages over screw insertion at the plate ends. For surgeons attempting to minimize soft tissue dissection, the decision to make additional incisions for screw placement should be considered with even more caution. PMID:25909372

  16. A computational study on the effect of fracture intrusion distance in three- and four-part trochanteric fractures treated with Gamma nail and sliding hip screw.

    PubMed

    Goffin, Jérôme M; Pankaj, Pankaj; Simpson, A Hamish

    2014-01-01

    Using finite element analysis, the behaviors of the Gamma nail and the sliding hip screw (SHS) were compared in an osteoporotic bone model for the fixation of three- and four-part trochanteric fractures (31-A2 in the AO classification, types IV and V in Evans' classification). The size of the medial fragment was varied based on clinical data, and the case of a fractured greater trochanter was also considered. Our results showed that for Evans' type V stabilized with a Gamma nail and for Evans' types IV and V with the SHS, cancellous bone around the lag screw is susceptible to yielding, thus indicating a risk of cut-out. The volume of bone susceptible to yielding increases with an increase in size of the medial fragment. Conversely, Evans' type IV with a Gamma nail was not predicted to cut out. Our findings suggest that future clinical trials investigating fixation of unstable proximal fractures should include the size of the medial fragment and the integrity of the greater trochanter as covariables and be powered to evaluate whether intramedullary devices are superior to SHSs for Evans' type IV fractures and inferior/equivalent for type V. PMID:24123306

  17. Dinitrogen fixation in aphotic oxygenated marine environments

    PubMed Central

    Rahav, Eyal; Bar-Zeev, Edo; Ohayon, Sarah; Elifantz, Hila; Belkin, Natalia; Herut, Barak; Mulholland, Margaret R.; Berman-Frank, Ilana

    2013-01-01

    We measured N2 fixation rates from oceanic zones that have traditionally been ignored as sources of biological N2 fixation; the aphotic, fully oxygenated, nitrate (NO?3)-rich, waters of the oligotrophic Levantine Basin (LB) and the Gulf of Aqaba (GA). N2 fixation rates measured from pelagic aphotic waters to depths up to 720 m, during the mixed and stratified periods, ranged from 0.01 nmol N L?1 d?1 to 0.38 nmol N L?1 d?1. N2 fixation rates correlated significantly with bacterial productivity and heterotrophic diazotrophs were identified from aphotic as well as photic depths. Dissolved free amino acid amendments to whole water from the GA enhanced bacterial productivity by 2–3.5 fold and N2 fixation rates by ~2-fold in samples collected from aphotic depths while in amendments to water from photic depths bacterial productivity increased 2–6 fold while N2 fixation rates increased by a factor of 2 to 4 illustrating that both BP and heterotrophic N2 fixation were carbon limited. Experimental manipulations of aphotic waters from the LB demonstrated a significant positive correlation between transparent exopolymeric particle (TEP) concentrations and N2 fixation rates. This suggests that sinking organic material and high carbon (C): nitrogen (N) micro-environments (such as TEP-based aggregates or marine snow) could support high heterotrophic N2 fixation rates in oxygenated surface waters and in the aphotic zones. Indeed, our calculations show that aphotic N2 fixation accounted for 37 to 75% of the total daily integrated N2 fixation rates at both locations in the Mediterranean and Red Seas with rates equal or greater to those measured from the photic layers. Moreover, our results indicate that that while N2 fixation may be limited in the surface waters, aphotic, pelagic N2 fixation may contribute significantly to new N inputs in other oligotrophic basins, yet it is currently not included in regional or global N budgets. PMID:23986748

  18. Nitrogen fixation by blue-green algae associated with the siphonous green seaweed Codium decorticatum: effects on ammonium uptake

    Microsoft Academic Search

    G. Rosenberg; H. W. Paerl

    1981-01-01

    Nitrogen fixation (acetylene reduction) at rates of up to 1.2 µg N2 g dry wt-1 h-1 was measured for the siphonous green seaweed Codium decorticatum. No nitrogenase activity was detected in C. isthmocladum. The nitrogenase activity was light sensitive and was inhibited by the addition of DCMU and triphenyl tetrazolium chloride. Additions of glucose did not stimulate nitrogen fixation. Blue-green

  19. The biomechanical analysis of three plating fixation systems for periprosthetic femoral fracture near the tip of a total hip arthroplasty

    PubMed Central

    2010-01-01

    Background A variety of techniques are available for fixation of femoral shaft fractures following total hip arthroplasty. The optimal surgical repair method still remains a point of controversy in the literature. However, few studies have quantified the performance of such repair constructs. This study biomechanically examined 3 different screw-plate and cable-plate systems for fixation of periprosthetic femoral fractures near the tip of a total hip arthroplasty. Methods Twelve pairs of human cadaveric femurs were utilized. Each left femur was prepared for the cemented insertion of the femoral component of a total hip implant. Femoral fractures were created in the femurs and subsequently repaired with Construct A (Zimmer Cable Ready System), Construct B (AO Cable-Plate System), or Construct C (Dall-Miles Cable Grip System). Right femora served as matched intact controls. Axial, torsional, and four-point bending tests were performed to obtain stiffness values. Results All repair systems showed 3.08 to 5.33 times greater axial stiffness over intact control specimens. Four-point normalized bending (0.69 to 0.85) and normalized torsional (0.55 to 0.69) stiffnesses were lower than intact controls for most comparisons. Screw-plates provided either greater or equal stiffness compared to cable-plates in almost all cases. There were no statistical differences between plating systems A, B, or C when compared to each other (p > 0.05). Conclusions Screw-plate systems provide more optimal mechanical stability than cable-plate systems for periprosthetic femur fractures near the tip of a total hip arthroplasty. PMID:20653962

  20. Femoral supracondylar focal dome osteotomy with plate fixation for acute correction of frontal plane knee deformity.

    PubMed

    El Ghazaly, Sherif Ahmed; El-Moatasem, El-Hussein Mohamed

    2015-04-01

    Focal dome osteotomy (FDO) allows deformity correction without secondary translational deformity. The purpose of this study was to evaluate the degree of correction and knee functional outcome after correction of frontal knee deformity using femoral supracondylar FDO fixed with plate and screws. A prospective study included 12 consecutive cases of femoral frontal plane deformity that underwent correction using supracondylar focal osteotomy fixed by plate and screws. Average age was 27 years, while mean follow-up was 2.1 years. Functional assessment was done using the Hospital for Special Surgery (HSS) knee score. The HSS knee score improved from 85 to 96.8 points. Desired correction was achieved in all cases. Postoperative mechanical axis analysis on long film and scanogram showed no secondary deformity. The overall postoperative mechanical axis was at 3.2 mm medially (range 2-5 mm). Autogenous bone graft was not used in any case, and uneventful osteotomy union was achieved at a mean of 13.8 weeks. Minor complications were encountered in two cases. There were no implant failures or reoperations. Supracondylar FDO of the femur with plate fixation is a reproducible technique that can produce full correction of distal femoral frontal plane deformity, while avoiding creating a secondary deformity. Knee function was improved with good patient satisfaction. PMID:25861038

  1. In vitro biomechanical comparison of six different fixation methods following 5-mm sagittal split advancement osteotomies.

    PubMed

    Oguz, Y; Watanabe, E R; Reis, J M; Spin-Neto, R; Gabrielli, M A; Pereira-Filho, V A

    2015-08-01

    The sagittal split ramus osteotomy (SSRO) is a surgical technique used widely to treat many congenital and acquired mandibular discrepancies. Stabilization of the osteotomy site and the potential for skeletal relapse after the procedure are still major problems. The aim of this study was to compare the mechanical stability of six methods of rigid fixation in SSRO using a biomechanical test model. Sixty polyurethane replicas of human hemimandibles were divided into six groups. In group I, the osteotomies were fixed with two four-hole titanium miniplates; in group II, with one four-hole miniplate; in group III, with one four-hole miniplate+a bicortical screw; in group IV, with a grid miniplate; in group V, with a four-hole locking miniplate; and in group VI, with a six-hole miniplate. A linear load in the premolar region was applied to the hemimandibles. The resistance forces (N) needed to displace the distal segment by 1, 3, and 5mm were recorded and the data transmitted from the load cell to a computer. One-way analysis of variance with Tukey's post hoc test was performed to compare the means between groups. For the three displacement conditions, there was a strong tendency for the 2.0-mm plate+screw and the grid plate to have higher values. PMID:25840861

  2. Locking screw apparatus and method for underwater remote replacement

    SciTech Connect

    Balog, L.J.

    1987-07-28

    A method is described for locking in place a screw which secures together first and second structures in the internal region of a nuclear reactor core. The first structure has a screw bore with a counterbore portion formed in an outer surface. The method comprises the steps of: forming a lateral recess in the counterbore portion and spaced from the outer surface, providing an elongated screw having an enlarged shoulder flange and an angular drive head with a lateral width substantially less than that of the counterbore portion, disposing the screw through the screw bore in threaded engagement with the second structure and with the shoulder rotatably seated in the counterbore portion. This provides a locking member having an angular opening and disposing it in the counterbore portion against the flange with the drive head received in the opening for engagement with the locking member to prevent rotation. This deforms a portion of the locking member into the recess for engagement to prevent movement of the locking member with respect to the first structure.

  3. Application of microwave fixation techniques in pathology to neuroscience studies: a review.

    PubMed

    Login, G R; Dvorak, A M

    1994-12-01

    The introduction of microwave energy into the scientist's repertoire of fixation modalities offers for the first time in relatively large specimens the potential for 'instantaneous' preservation of cellular structure for light and electron microscopy with minimal alteration of cellular biochemistry and antigenicity. Because of the rapid evolution of this new technology, we provide a classification system of newly generated microwave methods as applied to specimen preservation for microscopic analysis. With emphasis on neuronal tissue, we review qualitative and quantitative microscopy data of specimens fixed by two microwave methods in common use: (1) microwave stabilization and (2) fast and ultrafast, primary microwave-chemical fixation. In addition, we provide a table of neuropeptides or proteins in neuronal tissues that are preserved by various microwave fixation methods for histochemistry, immunohistochemistry, and immuno-electron microscopy studies. Commercial microwave ovens have limitations which can result in irreproducible fixation results. Therefore, we present a calibration protocol that is used to identify the best locations for fixation within large cavity (i.e., household) microwave ovens. We also provide a standardization protocol to improve the reproducibility of microwave fixation in calibrated, large-cavity microwave ovens. PMID:7723381

  4. Persistence and phase synchronisation properties of fixational eye movements

    NASA Astrophysics Data System (ADS)

    Moshel, S.; Zivotofsky, A. Z.; Jin-Rong, L.; Engbert, R.; Kurths, J.; Kliegl, R.; Havlin, S.

    2008-07-01

    When we fixate our gaze on a stable object, our eyes move continuously with extremely small involuntary and autonomic movements, that even we are unaware of during their occurrence. One of the roles of these fixational eye movements is to prevent the adaptation of the visual system to continuous illumination and inhibit fading of the image. These random, small movements are restricted at long time scales so as to keep the target at the centre of the field of view. In addition, the synchronisation properties between both eyes are related to binocular coordination in order to provide stereopsis. We investigated the roles of different time scale behaviours, especially how they are expressed in the different spatial directions (vertical versus horizontal). We also tested the synchronisation between both eyes. Results show different scaling behaviour between horizontal and vertical movements. When the small ballistic movements, i.e., microsaccades, are removed, the scaling behaviour in both axes becomes similar. Our findings suggest that microsaccades enhance the persistence at short time scales mostly in the horizontal component and much less in the vertical component. We also applied the phase synchronisation decay method to study the synchronisation between six combinations of binocular fixational eye movement components. We found that the vertical-vertical components of right and left eyes are significantly more synchronised than the horizontal-horizontal components. These differences may be due to the need for continuously moving the eyes in the horizontal plane in order to match the stereoscopic image for different viewing distances.

  5. Ilizarov hip reconstruction without external fixation: a new technique

    PubMed Central

    Lenze, U.; Hasler, C. C.

    2010-01-01

    Purpose The Ilizarov hip reconstruction is a well accepted but complication-prone operative salvage procedure in chronically dislocated hips, not least due to the long-term application of external fixation. Although the advantages of fully implantable devices are well known in limb lengthening and are described consistently, until now, external fixation has been used exclusively to perform the Ilizarov hip reconstruction procedure. We present a new technique of Ilizarov hip reconstruction with purely internal implants. Methods A 14-year-old girl with a history of spina bifida presented with a 4-cm-short right leg, a Trendelenburg gait and a complex neurological disease expression. Because of refusal of external fixation by the patient and significantly lower complication rates, an Ilizarov hip reconstruction without external fixation was performed. A locking compression plate was applied to fix the proximal femoral valgus-extension osteotomy and a motorised intramedullary distraction nail was used for the distal, lengthening–varisation osteotomy. Results A healing index of 33 days/cm and full weight bearing after 6 months were noted. At the 1 year follow-up, the patient showed an improvement of the Trendelenburg gait, as well as successful leg equalisation. Satisfaction to a high degree was additionally noted by factors such as reduced pain, the ability to wear workaday clothes and cosmetically appealing scars. No complications were recorded. Conclusion The exclusive use of internal implants for Ilizarov hip reconstruction is a feasible and patient-friendly alternative to traditional methods. Their use, however, may be restricted by geometric preconditions. PMID:21629378

  6. Biodegradable interlocking nails for fracture fixation.

    PubMed

    van der Elst, M; Bramer, J A; Klein, C P; de Lange, E S; Patka, P; Haarman, H J

    1998-12-01

    Serious problems such as stress shielding, allergic reactions, and corrosion are associated with the use of metallic fracture fixation devices in fractured long bones. Metal implants often are removed during a second retrieval operation after fracture healing has completed. A biocompatible implant that degrades slowly during implantation would obviate the need for a second operation and save the patient from considerable physical, psychologic, and financial discomfort. The biodegradable implant must provide the fractured limb sufficient support for a certain time, allowing early loading. A gradual transfer of load from the biodegradable implant to the bone would result in a better product of bone healing and avoid stress shielding. In an animal model using adult sheep, two types of biodegradable polymer interlocking nails were tested in comparison with a stainless steel interlocking nail. Fracture healing, mechanical properties of the bones, degradation behavior in vivo and in vitro, and tissue response were monitored during a 2 1/2-year followup study. To detect shifts in acid base relations caused by the release of acid compounds, pH measurements were performed. Fracture healing was unimpaired, and the mechanical test results of all three groups were excellent. Histologic analysis showed a mild inflammatory response, but no pH shifts were observed. The results of this study justify additional research on these promising materials. PMID:9917717

  7. Nitrogen fixation on Arctic glaciers, Svalbard

    NASA Astrophysics Data System (ADS)

    Telling, Jon; Anesio, Alexandre M.; Tranter, Martyn; Irvine-Fynn, Tristram; Hodson, Andy; Butler, Catriona; Wadham, Jemma

    2011-09-01

    Glacier surfaces contain a wide diversity of microorganisms and can host a range of microbial activities. However, microbial nutrient cycling on glaciers is poorly understood. This study is the first to document nitrogen fixation (nitrogenase activity) on glaciers and demonstrate its importance in supporting microbial growth. Rates of nitrogen fixation (nitrogenase activity) in cryoconite holes on three valley glaciers in Svalbard ranged from <2.0 to 99.9 ?mol ethylene m-2 d-1 with rates inversely correlated to concentrations of available inorganic nitrogen. Annual inputs of nitrogen by nitrogen fixation on a glacier catchment scale are more than 2 orders of magnitude lower than the combined nitrogen inputs from snowmelt and rain. However, nitrogen fixation can be important for supporting microbial growth on the glaciers during the middle to late melt season after the snowline has retreated upslope.

  8. Methanotrophy Induces Nitrogen Fixation in Boreal Mosses

    NASA Astrophysics Data System (ADS)

    Tiirola, M. A.

    2014-12-01

    Many methanotrophic bacterial groups fix nitrogen in laboratory conditions. Furthermore, nitrogen (N) is a limiting nutrient in many environments where methane concentrations are highest. Despite these facts, methane-induced N fixation has previously been overlooked, possibly due to methodological problems. To study the possible link between methanotrophy and diazotrophy in terrestrial and aquatic habitats, we measured the co-occurrence of these two processes in boreal forest, peatland and stream mosses using a stable isotope labeling approach (15 N2 and 13 CH4 double labeling) and sequencing of the nifH gene marker. N fixation associated with forest mosses was dependent on the annual N deposition, whereas methane stimulate N fixation neither in high (>3 kg N ha -1 yr -1) nor low deposition areas, which was in accordance with the nifH gene sequencing showing that forest mosses (Pleurozium schreberi and Hylocomium splendens ) carried mainly cyanobacterial N fixers. On the other extreme, in stream mosses (Fontinalis sp.) methane was actively oxidized throughout the year, whereas N fixation showed seasonal fluctuation. The co-occurrence of the two processes in single cell level was proven by co-localizing both N and methane-carbon fixation with the secondary ion mass spectrometry (SIMS) approach. Methanotrophy and diazotrophy was also studied in peatlands of different primary successional stages in the land-uplift coast of Bothnian Bay, in the Siikajoki chronosequence, where N accumulation rates in peat profiles indicate significant N fixation. Based on experimental evidence it was counted that methane-induced N fixation explained over one-third of the new N input in the younger peatland successional stages, where the highest N fixation rates and highest methane oxidation activities co-occurred in the water-submerged Sphagnum moss vegetation. The linkage between methanotrophic carbon cycling and N fixation may therefore constitute an important mechanism in the rapid accumulation of N during the primary succession of peatlands. It is still an open issue whether methanotrophy induces N fixation directly or by enhancing phototrophic or heterotrophic N fixation.

  9. Dynamics of free, straight dislocation pairs. I. Screw dislocations

    SciTech Connect

    Eykholt, R.; Trugman, S.A.; Srolovitz, D.J.

    1989-06-01

    Analytic expressions are derived for the motion of a pair of interacting, straight, parallel (or antiparallel) screw dislocations in an applied stress field. Analysis of the equations of motion of the dislocations shows that, under most circumstances, the velocity of a dislocation is proportional to the driving force (i.e., the motion is overdamped), and, in this limit, the results are exact. However, when the two dislocations are very close together, inertial terms begin to play a role, and the resultant ''finite-mass'' corrections are treated perturbatively. For the case of antiparallel screw dislocations, a capture cross section exists and is given by the product of the shear modulus and the Burgers vector over the applied stress. Based on these results, a simple statistical analysis of the motion of a large number of screw dislocations is presented.

  10. CMM probe compensation methods for measuring complex screw surface

    NASA Astrophysics Data System (ADS)

    Zhao, Qiancheng; Yang, Tianlong; Yin, Xiyun

    2013-01-01

    At present, probe compensation is the key problem in measuring geometric parameters of complex screw surface with CMM due to its complicated 3D shape, aiming at this problem, some new measurement methods are proposed based on geometric feature models, expressing the screw surface and its offset surface separately. Supposing the parameter lead of a screw surface is known, it's realized by scanning one single profile to complete probe compensation and calculate out all parameters, and the probe compensation is done by two improved methods, named as modified cross product and offset surface virtual measurement respectively, the theory and detailed process of which are discussed in this paper. After performing systematic experiments of profile scan, probe compensation and error evaluation, results show that the new measurement methods provide higher precision, stability and realizability.

  11. Optically driven Archimedes micro-screws for micropump application.

    PubMed

    Lin, Chih-Lang; Vitrant, Guy; Bouriau, Michel; Casalegno, Roger; Baldeck, Patrice L

    2011-04-25

    Archimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6 pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface. PMID:21643076

  12. Tunable helium bubble superlattice ordered by screw dislocation network

    NASA Astrophysics Data System (ADS)

    di, Zengfeng; Bai, Xian-Ming; Wei, Qiangmin; Won, Jonghan; Hoagland, Richard G.; Wang, Yongqiang; Misra, Amit; Uberuaga, Blas P.; Nastasi, Michael

    2011-08-01

    Helium bubble nucleation at low-angle twist boundaries in gold has been investigated. It is found that the helium bubbles preferentially nucleate at screw dislocation nodal points and result in helium bubble superlattice formation, which is completely isomorphic with the screw dislocation network along the twist-grain boundary. Molecular statics calculations reveal that defect formation/solution energies along the screw dislocations, especially at the nodal points, are lower than their bulk counterparts. It is believed that this driving force is responsible for the helium bubble superlattice formation. Our study suggests that grain boundary engineering via adjustable twist angles in parallel boundaries to form tunable 3D bubble superlattices could afford a very promising approach for design of radiation tolerant materials.

  13. Special Aspects of Nitrogen Fixation by Blue-Green Algae

    Microsoft Academic Search

    Rosalie M. Cox; P. Fay

    1969-01-01

    When carbon dioxide fixation was over 90% inhibited by CMU, nitrogen fixation remained unaffected in nitrogen-starved cells of Anabaena cylindrica. In normal cells under the same conditions nitrogen fixation was about 50% inhibited by CMU. These data suggest, first, that nitrogen fixation in this organism is independent of reducing potential generated by non-cyclic photo-electron transport and, secondly, that nitrogen fixation

  14. Pin loosening in external skeletal fixation 

    E-print Network

    Vittal, Bamini

    1993-01-01

    OF TABLES Page TABLE 1 Table showing the problems and complications of external fixations. TABLE 2 Table showing the experimental design. . . 22 TABLE 3 Table showing the number of cadaver dogs tested and the twist out rates and the pull out rates... included a chapter outlining technical details pertinent to the prevention of unnecessary complications associated with the use of external fixation. While their discussion of the strategies for avoiding complications was extensive, Shaar and Document...

  15. Biological nitrogen fixation: A scientific perspective

    Microsoft Academic Search

    R. H. Burris

    1988-01-01

    The discoveries of Hellriegel and Wilfarth ended the period of controversy about the existence of biological N2 fixation and launched a period featuring the agronomic application of the inoculation of legumes. Serious studies of the\\u000a biochemistry of N2 fixation started in the late 1920's, and defined some of the basic properties of the N2-fixing system. Application of15N as a tracer

  16. Stability of external skeletal fixation clamps

    E-print Network

    Sandel, Mark Eugene

    1995-01-01

    STABILITY OF EXTERNAL SKELETAL FIXATION CLAMPS A Thesis by MARK EUGENE SANDEL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1995 Major... Eugene Sandel, B. S. , Texas A%M University Chair of Advisory Committee: Dr. William A. Hyman External skeletal fixation is commonly used for treatment of many orthopedic diseases and injuries in both human and animal patients. It is mainly used...

  17. Simple technique for removing broken pedicular screw with plain and serviceable screwdriver

    Microsoft Academic Search

    Ahmet H. Kaya; Adnan Dagcinar; Fahrettin Celik; Alparslan Senel

    2008-01-01

    Removing the broken pedicular screw after spinal hardware failure is usually problematic. A specially designed simple screwdriver\\u000a and easy removal technique of broken pedicular screw with this screwdriver are described in this article.

  18. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section 1926.305...Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. ...otherwise secured at once. (ii) Hydraulic jacks exposed to freezing...

  19. Screw Placement and Osteoplasty Under Computed Tomographic-Fluoroscopic Guidance in a Case of Advanced Metastatic Destruction of the Iliosacral Joint

    SciTech Connect

    Trumm, Christoph Gregor, E-mail: christoph.trumm@med.lmu.de [University of Munich, Department of Clinical Radiology (Germany); Rubenbauer, Bianca; Piltz, Stefan [University of Munich, Department of Surgery (Germany); Reiser, Maximilian F.; Hoffmann, Ralf-Thorsten [University of Munich, Department of Clinical Radiology (Germany)

    2011-02-15

    We present a case of combined surgical screw placement and osteoplasty guided by computed tomography-fluoroscopy (CTF) in a 68-year-old man with unilateral osteolytic destruction and a pathological fracture of the iliosacral joint due to a metastasis from renal cell carcinoma. The patient experienced intractable lower back pain that was refractory to analgesia. After transarterial particle and coil embolization of the tumor-feeding vessels in the angiography unit, the procedure was performed under general anesthesia by an interdisciplinary team of interventional radiologists and trauma surgeons. Under intermittent single-shot CTF, two K wires were inserted into the left iliosacral joint from a lateral transiliac approach at the S1 level followed by two self-tapping surgical screws. Continuous CTF was used for monitoring of the subsequent polymethylmethacrylate injection through two vertebroplasty cannulas for further stabilization of the screw threads within the osteolytic sacral ala. Both the screw placement and cement injection were successful, with no complications occurring during or after the procedure. With additional nonsteroidal anti-inflammatory and opioid medication, the patient reported a marked decrease in his lower back pain and was able to move independently again at the 3-month follow-up assessment. In our patient with intolerable back pain due to tumor destruction and consequent pathological fracture of the iliosacral joint, CTF-guided iliosacral screw placement combined with osteoplasty was successful with respect to joint stabilization and a reduction in the need for analgesic therapy.

  20. Fracture fixation problems in osteoporosis.

    PubMed

    Strømsøe, Knut

    2004-02-01

    Osteoporosis, or loss of bone mass and microarchitectural deterioration of bone tissue, does not only enhance risk of fracture but also represents a problem in osteofixation of fractures in fracture treatment. Aging of the western population changes the epidemiology of fractures. An increasing socioeconomic interest in geriatric traumatology makes the need for much urgent study in the field of osteoporotic fractures self evident. It is no longer the province of only one medical group to look for fragmented solutions in the treatment of osteoporotic fractures. Efforts have to be united across professional boundaries to meet the challenge of this problem. Assessment of bone mineral may be used in evaluation of fracture risk but also in the choice of implant as well as in the design of implants used in fracture treatment. The differences in mechanical properties of different types of bone in the same individual have to be respected. Changes in the pattern of fractures and problems with implant anchorage in bone, due to a demographic increase in patients with osteoporosis remain problems requiring new solutions. Still basic principals in fracture treatment may not be eclipsed by new fixation devices. PMID:14736465

  1. Biomechanical and Histological Evaluation of Roughened Surface Titanium Screws Fabricated by Electron Beam Melting

    PubMed Central

    Yang, Jun; Cai, Hong; Lv, Jia; Zhang, Ke; Leng, Huijie; Wang, Zhiguo; Liu, Zhongjun

    2014-01-01

    Background Various fabrication methods are used to improve the stability and osseointegration of screws within the host bone. The aim of this study was to investigate whether roughened surface titanium screws fabricated by electron beam melting can provide better stability and osseointegration as compared with smooth titanium screws in sheep cervical vertebrae. Methods Roughened surface titanium screws, fabricated by electron beam melting, and conventional smooth surface titanium screws were implanted into sheep for 6 or 12 weeks (groups A and B, respectively). Bone ingrowth and implant stability were assessed with three-dimensional imaging and reconstruction, as well as histological and biomechanical tests. Results No screws in either group showed signs of loosening. Fibrous tissue formation could be seen around the screws at 6 weeks, which was replaced with bone at 12 weeks. Bone volume/total volume, bone surface area/bone volume, and the trabecular number were significantly higher for a define region of interest surrounding the roughened screws than that surrounding the smooth screws at 12 weeks. Indeed, for roughened screws, trabecular number was significantly higher at 12 weeks than at 6 weeks. On mechanical testing, the maximum pullout strength was significantly higher at 12 weeks than at 6 weeks, as expected; however, no significant differences were found between smooth and roughened screws at either time point. The maximum torque to extract the roughened screws was higher than that required for the smooth screws. Conclusions Electron beam melting is a simple and effective method for producing a roughened surface on titanium screws. After 12 weeks, roughened titanium screws demonstrated a high degree of osseointegration and increased torsional resistance to extraction over smooth titanium screws. PMID:24788866

  2. Biodegradation of Inion fast-absorbing biodegradable plates and screws.

    PubMed

    Losken, H Wolfgang; van Aalst, John A; Mooney, Mark P; Godfrey, Virginia L; Burt, Tripti; Teotia, Sumeet; Dean, Shay B; Moss, Jonathan R; Rahbar, Reza

    2008-05-01

    Biodegradable plates and screws are recommended for use in surgery of the craniofacial skeleton of children. To be effective and not interfere with growth of the child's skull, the plates must biodegrade sufficiently to release the holding power of the plate and screw within 1 year. It is also essential that excessive foreign body reaction and cyst formation does not occur when the plates and screws biodegrade. The purpose of this experimental study was to evaluate the rate of biodegradation of Inion CPS Baby biodegradable plates and screws under different clinical circumstances in the rabbit craniofacial skeleton and evaluate their efficacy for use in pediatric craniofacial surgery. Foreign body reaction would be evaluated. Inion baby plates and screws were tested in a rabbit model. Plates were applied to the frontal bone, over a bony defect of the parietal bone, to a nasal bone fracture, and inserted in the subcutaneous space over the occipital bone in thirty 6-week-old rabbits. Six rabbits were euthanized at 9, 12, 15, and 18 months' postoperative time point and examined for residual plates and screws. Bone from each surgical site was excised, fixed by immersion in 10% neutral-buffered formalin, decalcified in Immunocal solution, and examined by 7-microm paraffin sections stained with hematoxylin and eosin. At 9 months, the plates and screws had effectively biodegraded and no longer had holding power on the bones. Fragmentation of the implant material was noted. Residual implant material was still present on gross and histologic examination in rabbits at 9, 12, 15, and 18 months. Residue of a screw was still palpable in 1 rabbit at 18 months. There was no evidence of cyst formation in any of the examined specimens. Macrophages and giant cells were present in most of the specimens at 9, 12, 15, and 18 months. Findings from the current study revealed a relative short resorption time (9 mo) and normal inflammatory sequelae in an adult rabbit model. These findings suggest that these plates may be used safely in fixing the pediatric craniofacial skeleton. PMID:18520394

  3. Determination of the of rate cross slip of screw dislocations

    PubMed

    Vegge; Rasmussen; Leffers; Pedersen; Jacobsen

    2000-10-30

    The rate for cross slip of screw dislocations during annihilation of screw dipoles in copper is determined by molecular dynamics simulations. The temperature dependence of the rate is seen to obey an Arrhenius behavior in the investigated temperature range: 225-375 K. The activation energy and the effective attempt frequency can therefore be extracted from the simulations. The transition state energy for the annihilation process is calculated by identifying the transition state using the nudged elastic band path technique. The two activation energies agree very well, indicating that transition state theory is applicable for this type of process. PMID:11041947

  4. Virtual estimates of fastening strength for pedicle screw implantation procedures

    NASA Astrophysics Data System (ADS)

    Linte, Cristian A.; Camp, Jon J.; Augustine, Kurt E.; Huddleston, Paul M.; Robb, Richard A.; Holmes, David R.

    2014-03-01

    Traditional 2D images provide limited use for accurate planning of spine interventions, mainly due to the complex 3D anatomy of the spine and close proximity of nerve bundles and vascular structures that must be avoided during the procedure. Our previously developed clinician-friendly platform for spine surgery planning takes advantage of 3D pre-operative images, to enable oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating, and placement of virtual pedicle implants. Here we extend the capabilities of the planning platform and demonstrate how the virtual templating approach not only assists with the selection of the optimal implant size and trajectory, but can also be augmented to provide surrogate estimates of the fastening strength of the implanted pedicle screws based on implant dimension and bone mineral density of the displaced bone substrate. According to the failure theories, each screw withstands a maximum holding power that is directly proportional to the screw diameter (D), the length of the in-bone segm,ent of the screw (L), and the density (i.e., bone mineral density) of the pedicle body. In this application, voxel intensity is used as a surrogate measure of the bone mineral density (BMD) of the pedicle body segment displaced by the screw. We conducted an initial assessment of the developed platform using retrospective pre- and post-operative clinical 3D CT data from four patients who underwent spine surgery, consisting of a total of 26 pedicle screws implanted in the lumbar spine. The Fastening Strength of the planned implants was directly assessed by estimating the intensity - area product across the pedicle volume displaced by the virtually implanted screw. For post-operative assessment, each vertebra was registered to its homologous counterpart in the pre-operative image using an intensity-based rigid registration followed by manual adjustment. Following registration, the Fastening Strength was computed for each displaced bone segment. According to our preliminary clinical study, a comparison between Fastening Strength, displaced bone volume and mean voxel intensity showed similar results (p < 0.1) between the virtually templated plans and the post-operative outcome following the traditional clinical approach. This study has demonstrated the feasibility of the platform in providing estimates the pedicle screw fastening strength via virtual implantation, given the intrinsic vertebral geometry and bone mineral density, enabling the selection of the optimal implant dimension adn trajectory for improved strength.

  5. Screw- versus cement-retained implant restorations: current concepts.

    PubMed

    Lee, Angie; Okayasu, Kozue; Wang, Hom-Lay

    2010-02-01

    The debate between screw- versus cement-retained implant prostheses has long been discussed but the best type of implant prosthesis remains controversial among practitioners. An understanding of their properties will help the clinician in selecting the ideal prosthesis for each clinical case while promoting final esthetic outcomes. With the evolving technology and knowledge, an update of the current trends is necessary. This article provides an overview of the different characteristics of screw- and cement-retained implant restorations, and how they may influence the esthetics, retrievability, retention, passivity, occlusion, accessibility, cost, and provisional restorations. Problems and complications frequently encountered are discussed and treatment solutions are proposed. PMID:20147811

  6. Effect of cement washout on loosening of abutment screws and vice versa in screw- and cement- retained implant-supported dental prosthesis

    PubMed Central

    Kim, Seok-Gyu; Son, Mee-Kyoung

    2015-01-01

    PURPOSE The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and noncemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening. PMID:26140172

  7. Superior border versus inferior border fixation in displaced mandibular angle fractures: prospective randomized comparative study.

    PubMed

    Singh, V; Khatana, S; Bhagol, A

    2014-07-01

    A prospective randomized comparative study was conducted to compare open reduction and internal fixation of displaced fractures (>2mm) via intraoral approach with application of a single monocortical miniplate according to Champy's ideal line of osteosynthesis (group A) versus an extraoral approach with application of an inferior border plate with at least two holes (bicortical screws) on either side of the fracture line (group B). Clinical and radiographic assessment was done preoperatively, immediately postoperative, and at 1, 4, and 12 weeks of follow-up. Parametric and non-parametric data were evaluated by independent samples t-test and ?(2) analysis, respectively; P<0.05 was considered statistically significant. There was no significant difference between the two groups with regard to complication rates, although functional outcomes including pain (visual analogue scale score) at the 1-week follow-up and inter-incisal mouth opening at the 12-week follow-up were found to be better in group B. On radiographic assessment, the inferior border was better aligned in group B than in group A, with no superior border distraction in group B. The duration of surgery was shorter in group B, and this was considered to be the easier approach for fixation of the device as assessed by the surgeons. PMID:24636170

  8. Combined Chronic Occipito-atlantal and Atlanto-axial Rotator Fixation with Cerebral Palsy.

    PubMed

    Kim, Jae Hong; Kim, Jung Hee; Jang, Se Youn; Kong, Min Ho

    2013-09-01

    Occipito-atlantalrotatory subluxation that occurs in conjunction with atlanto-axial rotator fixation is extremely rare. The common clinical characteristics are painful torticollis and cock robin position presented with the head tilted to one side and rotated to the other side. The object of this report is to emphasize that AARF combined with OARF may be caused by a variety of conditions, to be must need algorithm for proper management, apparently. A torticollis patient who had cerebral palsy presented with severe nuchal pain and wryneck for a long period. The patient had a history of fallen down 16 years ago which caused severe nuchal pain. The conservative management had failed to correct the deformity and instability. we decided to operate using occiput-C1-C2 arthrodesis and C3-4-5 bilateral screw fixation for reinforcement. Now he doesn't have neurologic deficit and shows good outcome enough to sustain his head, not using his hands, in his daily life. PMID:24757487

  9. Fractured neck of femur below long spinopelvic fixation for Charcot spine: a case report

    PubMed Central

    2013-01-01

    Introduction We present a case of a patient with a previously undescribed complication: intertrochanteric femoral neck insufficiency fracture after long-segment instrumented spinopelvic fusion to the ilium for Charcot spine. Case presentation A 42-year-old Caucasian man with post-traumatic complete T6 paraplegia presented to our institution after developing Charcot spinal arthropathy at L3 and L4 and symptoms of autonomic dysreflexia 21 years after his original spinal cord injury. Multiple anterior and posterior surgeries were required to eventually achieve stabilization of his thoracolumbar spine to his pelvis and resolution of symptoms. The most distal fixation point was two iliac wing screws bilaterally. At 10 weeks after the final spinal surgery and after posterior spinal bony consolidation had occurred, he sustained an intertrochanteric femoral neck fracture, distal to the iliac fixation, whilst bending forward in his wheelchair. His proximal femoral fracture was internally fixed with an intramedullary device. Conclusions Spinal Charcot’s arthropathy is a rare condition that may occur in patients with post-traumatic spinal cord injury. Although associated with high risk of complications, circumferential instrumented fusion in Charcot spine can restore spinal stability. Insufficiency fractures of the proximal femur are possible complications of long spinopelvic fusions. PMID:24378187

  10. Rates of Dinitrogen Fixation and the Abundance of Diazotrophs in North American Coastal Waters Between Cape Hatteras and Georges Bank

    NASA Technical Reports Server (NTRS)

    Mulholland, M.R.; Bernhardt, P. W.; Blanco-Garcia, J. L.; Mannino, A.; Hyde, K.; Mondragon, E.; Turk, K.; Moisander, P. H.; Zehr, J. P.

    2012-01-01

    We coupled dinitrogen (N2) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid-Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N2 fixation were as high as 49.8 nmol N L(sup -1) d(sup -1) and areal rates as high as 837.9 micromol N m(sup -2) d(sup -1) in our study area. Our results suggest that N2 fixation occurs at high rates in coastal shelf waters that were previously thought to be unimportant sites of N2 fixation and so were excluded from calculations of pelagic marine N2 fixation. Unicellular N2-fixing group A cyanobacteria were the most abundant diazotrophs in the Atlantic coastal waters and their abundance was comparable to, or higher than, that measured in oceanic regimes where they were discovered. High rates of N2 fixation and the high abundance of diazotrophs along the North American Mid-Atlantic continental shelf highlight the need to revise marine N budgets to include coastal N2 fixation. Integrating areal rates of N2 fixation over the continental shelf area between Cape Hatteras and Nova Scotia, the estimated N2 fixation in this temperate shelf system is about 0.02 Tmol N yr(sup -1), the amount previously calculated for the entire North Atlantic continental shelf. Additional studies should provide spatially, temporally, and seasonally resolved rate estimates from coastal systems to better constrain N inputs via N2 fixation from the neritic zone.

  11. A novel approach toward pedicle screw placement in the thoracic spine

    Microsoft Academic Search

    John Thalgott; Mark Kabins; James Giuffre

    2002-01-01

    Purpose of study: Because of the smaller size of the thoracic pedicle, primarily in the coronal plane, most surgeons have opted to avoid the used of transpedicular screws in the thoracic spine. A new technique for placement of screws through thoracic pedicles with and without lateral wall violation is described.Methods used: From April 1992 through February 1999, 1,064 pedicle screws

  12. Influence of the coating material on the loosing of dental implant abutment screw joints

    Microsoft Academic Search

    C. N. Elias; D. C. Figueira; P. R. Rios

    2006-01-01

    Dental implant abutment screw joints tend to loosen and prosthesis rotation has been observed under clinical conditions. Some dental implant manufacturers suggest coated abutment screw to prevent the displacement of dental prosthesis. In the present work, the opening torque (N cm) was measured as a function of tightening torque (N cm) for dental implant abutment screws coated with four different

  13. MECHANICS OF THE TAPER INTEGRATED SCREWED-IN (TIS) ABUTMENTS USED IN DENTAL IMPLANTS

    E-print Network

    Müftü, Sinan

    1 MECHANICS OF THE TAPER INTEGRATED SCREWED-IN (TIS) ABUTMENTS USED IN DENTAL IMPLANTS by Dinçer. Keywords: Dental implants; Taper lock; Morse taper; Conical interference fit; Tapered screw; Screw mechanics; Loosening torque, Tightening torque #12;3 INTRODUCTION A dental implant system serves

  14. On Screw-Transform Manifolds Russell A. Manning Charles R. Dyer

    E-print Network

    Dyer, Charles R.

    describes the mathematical theory of screw-transform manifolds and their use in camera self cali- brationOn Screw-Transform Manifolds Russell A. Manning Charles R. Dyer Department of Computer Sciences transformation that moves the camera from the first location to the second location is equivalent to a screw

  15. Improved Screw Theory using Second Order Terms Jun Takamatsu Hiroshi Kimurat Katsushi Ikeuchi

    E-print Network

    Ikeuchi, Katsushi

    Improved Screw Theory using Second Order Terms Jun Takamatsu Hiroshi Kimurat Katsushi Ikeuchi this displacement, the screw theory is employed. It is equivalent to the first order Taylor expansion of the displacement. The screw theory is very convenient, because the displacement is formulated as simulta- neous

  16. Calculating Possible Local Displacement of Curve Objects using Improved Screw Theory

    E-print Network

    Ikeuchi, Katsushi

    Calculating Possible Local Displacement of Curve Objects using Improved Screw Theory Jun Takamatsu of objects have been pro- posed. To calculate this displacement, the screw theory is employed polyhedral objects only. Because the screw theory cannot treat curvature information of objects

  17. The singularity study of spatial hybrid mechanisms based on screw theory

    Microsoft Academic Search

    J.-S. Zhao; K. Zhou; Z.-J. Feng; Z.-Y. Tan

    2005-01-01

    In this paper, a novel methodology based on screw theory to study the singularity of spatial hybrid mechanisms is presented. According to the physical meaning of inverse screws, we introduce the equivalent kinematic screws to replace the function of those of the parallel limbs, and therefore the hybrid branch can be transformed into a pure series kinematic chain which can

  18. Gauge-field-theory solution of the elastic state of a screw dislocation in a dispersive

    E-print Network

    Sharma, Pradeep

    Gauge-field-theory solution of the elastic state of a screw dislocation in a dispersive (non the solution of most screw dislocation problems in the gauge non-local theory of defects, provided, NY 12309, USA The relaxed state of a type of topological defect (screw dislocation) located

  19. Collision Prediction for Polyhedra under Screw Motions Byungmoon Kim Jarek Rossignac

    E-print Network

    Rossignac, Jarek

    General Terms Theory Keywords Collision Detection, Screw Motion, Polyhedra Permission to make digitalCollision Prediction for Polyhedra under Screw Motions Byungmoon Kim Jarek Rossignac bmkim the relative motion between pairs of objects by a sequence of screw motion segments, each defined

  20. Screw-theoretic analysis models for felid jaw mechanisms Michael J. Delsignore, Venkat N. Krovi *

    E-print Network

    Krovi, Venkat

    Elsevier Ltd. All rights reserved. Keywords: Screw-theory; Musculoskeletal systems; Optimization; CableScrew-theoretic analysis models for felid jaw mechanisms Michael J. Delsignore, Venkat N. Krovi of quasi-static computational models for musculoskeletal analysis, leverag- ing screw-theoretic techniques

  1. Atlantoaxial Screw Fixation for the Treatment of Isolated and Combined Unstable Jefferson Fractures – Experiences with 8 Patients

    Microsoft Academic Search

    C. Hein; H.-P. Richter; S. A. Rath

    2002-01-01

    Summary.  \\u000a ?The unstable atlas burst fracture (“Jefferson fracture”) is a fracture of the anterior and posterior atlantal arch with rupture\\u000a of the transverse atlantal ligament and an incongruence of the atlanto-occipital and the atlanto-axial joint facets. The question\\u000a whether it has to be treated surgically or nonsurgically is still discussed and remains controversial. During the last decade\\u000a 8 patients with

  2. Screw fixation via diploic bone paralleling to occiput table: anatomical analysis of a new technique and report of 11 cases

    Microsoft Academic Search

    Tan Mingsheng; Wang Huimin; Jiang Xin; Yi Ping; Wei Hongyu; Yang Feng; Wang Wu; Zhang Guangbo

    2007-01-01

    Several types of posterior approaches have been adopted for occipitocervical fusion. Prior to this study, Foerater et al.\\u000a in 1927 used a fibular strut graft in the site between the occiput and the lower cervical spine to achieve fusion. Since then,\\u000a various techniques including wrings, Hartshill loop, AO reconstructive plate, and AXIS occipital plate were described and\\u000a used widely. As

  3. Calculation of axial forces on the screw in rubber extruders

    Microsoft Academic Search

    S. P. Konclrakov; M. S. Samoilov; N. V. Tyabin; A. G. Govsha

    1972-01-01

    A special hydraulic thrust bearing (Fig. 1) was developed for measuring the axial forces of the screw. The thrust bearing consists of a body 7, a guiding collar 4, a rubber collar 6, assembled in one unit using a clamping nut 5. The cavity formed between the body 7 and the collar 6, and also the connecting pipe 9 and

  4. INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE INTERIOR OF FITTINGS ON ONE IN A BANK OF TAPPING MACHINES, EACH OPERATED BY THE SAME WORKER SIMULTANEOUSLY BUT TIMED TO REQUIRE WORKER ACTION AT INTERVALS THAT DO NOT INTERFERE WITH THE OTHER MACHINES. - Stockham Pipe & Fittings Company, Tapping Room, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  5. Twin-screw extrusion of ‘Pesta’-encapsulated biocontrol agents

    Microsoft Academic Search

    D. J. Daigle; W. J. Connick; C. D. Boyette; M. P. Lovisa; K. S. Williams; M. Watson

    1997-01-01

    ‘Pesta’ granules in which fungal propagules are encapsulated in a wheat gluten matrix were prepared in multipound quantities by twin-screw extrusion and fluid bed drying. Dough formulations for extrusion contained wheat flour and kaolin, or wheat flour, kaolin and rice flour, plus water and fungal inoculum. Conidial inoculum of Colletotrichum truncatum, a pathogen of the weed hemp sesbania (Sesbania exaltata),

  6. Successive Screw Approximation in Ising Lattice Gauge Theory

    NASA Astrophysics Data System (ADS)

    Katsumori, H.

    1984-01-01

    Kramers and Wannier's successive screw technique is applied to the three-dimensional Ising lattice gauge theory. The largest eigenvalue of the transfer matrix is directly calculated on a computer, independently of Monte Carlo simulation. Anomalous behavior of the specific heat implies the existence of a phase transition.

  7. Force between two parallel screw dislocations - gauge theory result

    NASA Astrophysics Data System (ADS)

    Valsakumar, M. C.; Sahoo, Debendranath

    1996-02-01

    The expression for the force between two parallel screw dislocations is derived in the framework of the Yang-Mills-type gauge theory of dislocations earlier proposed by Kadic and Edelen [A gauge theory of dislocations and disclinations (Springer, Berlin, 1983)] and later developed by Valsakumar and Sahoo [Bull. Mater. Sci. 10 (1988) 3].

  8. Dynamics of parallel manipulators by means of screw theory

    Microsoft Academic Search

    J. Gallardo; J. M. Rico; A. Frisoli; D. Checcacci; M. Bergamasco

    2003-01-01

    An approach to the dynamic analysis of parallel manipulators is presented. The proposed method, based on the theory of screws and on the principle of virtual work, allows a straightforward calculation of the actuator forces as a function of the external applied forces and the imposed trajectory. In order to show the generality of such a methodology, two case studies

  9. Jerk Influence Coefficients, via Screw Theory, of Closed Chains

    Microsoft Academic Search

    J. Gallardo-Alvarado; J. M. Rico-Martinez

    2001-01-01

    In this paper a novel method for determining the kinematic influence coefficients up to the jerk analysis of closed chains with multiple degrees of freedom by means of screw theory, also known as motor algebra, is introduced. A closed chain is obtained by rigidly attaching the end-effector of a serial chain to the base link. This condition ensures that the

  10. Force between two parallel screw dislocations — gauge theory result

    Microsoft Academic Search

    M. C. Valsakumar; Debendranath Sahoo

    1996-01-01

    The expression for the force between two parallel screw dislocations is derived in the framework of the Yang-Mills-type gauge theory of dislocations earlier proposed by Kadic and Edelen [A gauge theory of dislocations and disclinations (Springer, Berlin, 1983)] and later developed by Valsakumar and Sahoo [Bull. Mater. Sci. 10 (1988) 3].

  11. A computational analysis of screw transformations in robotics

    Microsoft Academic Search

    JANEZ FUNDA; RICHARD P. PAUL

    1990-01-01

    A computational analysis and a comparison of line-oriented representations of general (i.e. rotational and translational) spatial displacements of rigid bodies are presented. Four mathematical formalisms for effecting a general spatial screw displacement are discussed and analyzed in terms of computational efficiency in performing common operations needed in kinematic analysis of multilinked spatial mechanisms. The corresponding algorithms are analyzed in terms

  12. 39. VIEW OF VESSEL STERNON IN DRYDOCK. NOTE TWIN SCREWS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    39. VIEW OF VESSEL STERN-ON IN DRYDOCK. NOTE TWIN SCREWS AND RUDDER. GENTLEMEN IN VIEW UNKNOWN Original 5'x5' photograph taken by Robert S. Douglas in 1966 - Pilot Schooner "Alabama", Moored in harbor at Vineyard Haven, Vineyard Haven, Dukes County, MA

  13. The empirical modeling of a Lysholm screw expander

    Microsoft Academic Search

    R. F. Stiedel; K. A. Brown; D. H. Pankow

    1983-01-01

    This is a description of the development of an engine model for the prediction of mass flow rate, power, efficiency and exhaust quality for a Lysholm Screw Expander at a given set of operating conditions. The testing of an expander having a rotor diameter of 130 mm (5.12 inches) and an expansion ratio of 5.3 was performed with simulated geothermal

  14. Screw Type Steam Compressors for Mechanical Vapor Recompression (MVR) Systems 

    E-print Network

    Kawamura, K.; Apaloo, Thomas-L.

    1986-01-01

    the low pressure steam to a usable pressure for reinjection into the process stream. Mycom has developed, designed and installed two large MVR systems using screw compressors: one for a brewery and the other for a whiskey plant. This paper discusses...

  15. Review Article: Screw Compressors in Refrigeration and Air Conditioning

    Microsoft Academic Search

    Nikola Stoši?

    2004-01-01

    Recent advances in the techniques for manufacturing vital parts, such as rotors and bearings, have enabled improvements to be made to screw compressors that were difficult to imagine only a few years ago. This has inevitably influenced the prospects for these machines in refrigeration and air-conditioning applications. Some aspects of this are presented, together with well known but not always

  16. A Screw Syzygy with Applications to Robot Singularity Computation

    Microsoft Academic Search

    J. M. Selig; Peter Donelan

    A syzygy is a relation between invariants. In this paper a syzygy is presented between invariants of sequences of six screws\\u000a under the action of the Euclidean group. This relation is useful in simplifying the computation of the determinant of a robot\\u000a Jacobian and hence can be used to investigate the singularities of robot manipulators.

  17. Numerical study on mixing performance of glass fiber dispersion in a twin-screw extruder with backward-mixing elements

    NASA Astrophysics Data System (ADS)

    Hirata, Kunihiro; Ishida, Hiroshi; Hiragori, Motohiro; Nakayama, Yasuya; Kajiwara, Toshihisa

    2015-05-01

    In the kneading of glass-fiber-reinforced plastics by twin-screw extrusion, the use of a backward-mixing screw (BMS) element for melt mixing has been found to be effective in dispersing glass-fiber bundles. In this study, we use the computational fluid dynamics (CFD) to study the mechanism of dispersion by a BMS element for glass fiber bundles. The result of CFD for a BMS and a forward kneading disk (FKD) reveals that the melt mixing by a BMS is highly effective to act the required stress on overall resin. In addition, there is a good correlation between the incidence of undispersed glass-fiber bundles measured experimentally and the minimum value of distribution of the time-integrated stress calculated numerically. On the basis of the above results, we propose a method to predict the operating conditions in which the incident probability of undispersed glass-fiber bundles and thermal degradation are controlled.

  18. Binocular eye orientation during fixations: Listing's law extended to include eye vergence.

    PubMed

    Van Rijn, L J; Van den Berg, A V

    1993-01-01

    Any eye position can be reached from a position called the primary position by rotation about a single axis. Listing's law states that for targets at optical infinity all rotation axes form a plane; the so-called Listing plane. Listing's law is not valid for fixation of nearby targets. To document these deviations of Listing's law we studied binocular eye positions during fixations of point targets in the dark. We tested both symmetric (targets in a sagittal plane) and asymmetric vergence conditions. For upward fixation both eyes showed intorsion relative to the position that would have been taken if each eye followed Listing's law. For downward fixation we found extorsion. The in- or extorsion increased approximately linearly with the vergence angle. The direction of the Listing axis and the turn angle about this axis can be described by rotation vectors. Our observations indicate that for fixation of nearby targets the rotation vectors of the two eyes become different and are no longer located in a single plane. However, we find that it is possible to decomose the rotation vector of each eye into the sum of a symmetric and an anti-symmetric part, each with its own properties. (1) The symmetric part is associated with eye version. This component of the rotation vector is identical for both eyes and lies in Listing's plane. In contrast to the classical form of Listing's law, this part of the rotation vector lies in Listing's plane irrespective of the fixation distance. (2) The anti-symmetric part of the rotation vector is related to eye vergence. This component is of equal magnitude but oppositely directed in each eye. The anti-symmetric part lies in the mid-sagittal plane, also irrespective of fixation distance. For fixation of targets at optical infinity the anti-symmetric part equals zero and the eye positions obey the classical form of Listing's law. Thus, the symmetric and anti-symmetric parts of the rotation vectors are restricted to two perpendicular planes. Combining these restrictions in a model, with the additional restriction that the vertical vergence equals zero during fixation of point targets, we arrive at the prediction that the cyclovergence is proportional to the product of elevation and horizontal vergence angles. This was well born out by the data. The model allows to describe the binocular eye position for fixation of any target position in terms of the bipolar coordinates of the target only (i.e. using only three degrees of freedom instead of the six needed for two eyes). PMID:8351841

  19. Covering the screw-access holes of implant restorations in the esthetic zone: a clinical report.

    PubMed

    Saboury, Abolfazl; Gooya, Ali

    2014-11-01

    Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics. PMID:25628703

  20. The Fixation and Saccade P3

    PubMed Central

    Dandekar, Sangita; Ding, Jian; Privitera, Claudio; Carney, Thom; Klein, Stanley A.

    2012-01-01

    Although most instances of object recognition during natural viewing occur in the presence of saccades, the neural correlates of objection recognition have almost exclusively been examined during fixation. Recent studies have indicated that there are post-saccadic modulations of neural activity immediately following eye movement landing; however, whether post-saccadic modulations affect relatively late occurring cognitive components such as the P3 has not been explored. The P3 as conventionally measured at fixation is commonly used in brain computer interfaces, hence characterizing the post-saccadic P3 could aid in the development of improved brain computer interfaces that allow for eye movements. In this study, the P3 observed after saccadic landing was compared to the P3 measured at fixation. No significant differences in P3 start time, temporal persistence, or amplitude were found between fixation and saccade trials. Importantly, sensory neural responses canceled in the target minus distracter comparisons used to identify the P3. Our results indicate that relatively late occurring cognitive neural components such as the P3 are likely less sensitive to post saccadic modulations than sensory neural components and other neural activity occurring shortly after eye movement landing. Furthermore, due to the similarity of the fixation and saccade P3, we conclude that the P3 following saccadic landing could possibly be used as a viable signal in brain computer interfaces allowing for eye movements. PMID:23144959

  1. The general theory of blade screws including propellers, fans, helicopter screws, helicoidal pumps, turbo-motors, and different kinds of helicoidal blades

    NASA Technical Reports Server (NTRS)

    De Bothezat, George

    1920-01-01

    Report presents a theory which gives a complete picture and an exact quantitative analysis of the whole phenomenon of the working of blade screws, but also unites in a continuous whole the entire scale of states of work conceivable for a blade screw. Chapter 1 is devoted to the establishment of the system of fundamental equations relating to the blade screw. Chapter 2 contains the general discussion of the 16 states of work which may establish themselves for a blade screw. The existence of the vortex ring state and the whirling phenomenon are established. All the fundamental functions which enter the blade-screw theory are submitted to a general analytical discussion. The general outline of the curve of the specific function is examined. Two limited cases of the work of the screw, the screw with a zero constructive pitch and the screw with an infinite constructive pitch, are pointed out. Chapter 3 is devoted to the study of the propulsive screw or propeller. (author)

  2. The Role of Nitrogen Fixation in Cyanobacterial Bloom Toxicity in a Temperate, Eutrophic Lake

    PubMed Central

    Beversdorf, Lucas J.; Miller, Todd R.; McMahon, Katherine D.

    2013-01-01

    Toxic cyanobacterial blooms threaten freshwaters worldwide but have proven difficult to predict because the mechanisms of bloom formation and toxin production are unknown, especially on weekly time scales. Water quality management continues to focus on aggregated metrics, such as chlorophyll and total nutrients, which may not be sufficient to explain complex community changes and functions such as toxin production. For example, nitrogen (N) speciation and cycling play an important role, on daily time scales, in shaping cyanobacterial communities because declining N has been shown to select for N fixers. In addition, subsequent N pulses from N2 fixation may stimulate and sustain toxic cyanobacterial growth. Herein, we describe how rapid early summer declines in N followed by bursts of N fixation have shaped cyanobacterial communities in a eutrophic lake (Lake Mendota, Wisconsin, USA), possibly driving toxic Microcystis blooms throughout the growing season. On weekly time scales in 2010 and 2011, we monitored the cyanobacterial community in a eutrophic lake using the phycocyanin intergenic spacer (PC-IGS) region to determine population dynamics. In parallel, we measured microcystin concentrations, N2 fixation rates, and potential environmental drivers that contribute to structuring the community. In both years, cyanobacterial community change was strongly correlated with dissolved inorganic nitrogen (DIN) concentrations, and Aphanizomenon and Microcystis alternated dominance throughout the pre-toxic, toxic, and post-toxic phases of the lake. Microcystin concentrations increased a few days after the first significant N2 fixation rates were observed. Then, following large early summer N2 fixation events, Microcystis increased and became most abundant. Maximum microcystin concentrations coincided with Microcystis dominance. In both years, DIN concentrations dropped again in late summer, and N2 fixation rates and Aphanizomenon abundance increased before the lake mixed in the fall. Estimated N inputs from N2 fixation were large enough to supplement, or even support, the toxic Microcystis blooms. PMID:23405255

  3. Easy retrieval of polyaxial tulip-head pedicle screws by “U” rod technique

    PubMed Central

    Isik, Cengiz; Altinel, Levent; Ates, Ali; Ozdemir, Mustafa

    2009-01-01

    The number of fusion surgeries increase each year which also increase the need for implant removal. In some cases, it can be extremely hard to remove a pedicle screw especially when there is a mismatch of the screw and the screwdriver. Also the screwdrivers can be contaminated during the operation, and this will cause a delay till the instruments are re-sterilized. There is a need for the removal of screws without special instruments. We describe a method for removing tulip-head polyaxial pedicle screws without special instruments. The screws are removed using an Allen key, a rod bender and a “U” shaped rod. We successfully removed 76 screws in 11 recent cases without any complications. The “U” rod technique is a simple and useful technique for the removal of tulip-head polyaxial screws. PMID:19618219

  4. Biometric recognition via fixation density maps

    NASA Astrophysics Data System (ADS)

    Rigas, Ioannis; Komogortsev, Oleg V.

    2014-05-01

    This work introduces and evaluates a novel eye movement-driven biometric approach that employs eye fixation density maps for person identification. The proposed feature offers a dynamic representation of the biometric identity, storing rich information regarding the behavioral and physical eye movement characteristics of the individuals. The innate ability of fixation density maps to capture the spatial layout of the eye movements in conjunction with their probabilistic nature makes them a particularly suitable option as an eye movement biometrical trait in cases when free-viewing stimuli is presented. In order to demonstrate the effectiveness of the proposed approach, the method is evaluated on three different datasets containing a wide gamut of stimuli types, such as static images, video and text segments. The obtained results indicate a minimum EER (Equal Error Rate) of 18.3 %, revealing the perspectives on the utilization of fixation density maps as an enhancing biometrical cue during identification scenarios in dynamic visual environments.

  5. Fluorinated Alcohols as Activators for the Solvent-Free Chemical Fixation of Carbon Dioxide into Epoxides.

    PubMed

    Gennen, Sandro; Alves, Margot; Méreau, Raphaël; Tassaing, Thierry; Gilbert, Bernard; Detrembleur, Christophe; Jerome, Christine; Grignard, Bruno

    2015-06-01

    The addition of fluorinated alcohols to onium salts provides highly efficient organocatalysts for the chemical fixation of CO2 into epoxides under mild experimental conditions. The combination of online kinetic studies, NMR titrations and DFT calculations allows understanding this synergistic effect that provides an active organocatalyst for CO2 /epoxides coupling. PMID:25951520

  6. Synthesis and efficiency of a new chemical fixation agent for stabilizing MSWI fly ash

    Microsoft Academic Search

    Wu-Jang Huang; Jui-Shih Lo

    2004-01-01

    In this study, a novel chemical fixation agent, colloidal aluminate oxide (CAO), has been synthesized and characterized in detail. CAO does not require cementitious additives, and can be used as a stabilizer of lead in the fly ash from municipal solid waste incineration (MSWI) plants. CAO reveals a high reduction ratio for the leachability of Pb of 94.8% when compared

  7. The effect of shear forces and addition of a mixture of a protease and a hemicellulase on chemical, physical and physiological parameters during extrusion of soybean meal

    Microsoft Academic Search

    G. J. P. Marsman; H. Gruppen; J. W. Resink; M. W. A. Verstegen; A. G. J. Voragen

    1995-01-01

    The influence of shear forces during extrusion of toasted soybean meal (TSBM) and the addition of enzymes before and after extrusion on some chemical, physical and physiological parameters were studied. Shear forces were introduced by the use of 0, 1 and 2 twin lead slotted screws (TLSSs) during extrusion of TSBM with a single-screw extruder. The experiment included 6 treatments:

  8. MICROBIOLOGY: A Fifth Pathway of Carbon Fixation

    NSDL National Science Digital Library

    Rudolf K. Thauer (Max Planck Institute for Terrestrial Microbiology; )

    2007-12-14

    Access to the article is free, however registration and sign-in are required. Genome sequence analyses and enzymatic studies reveal a novel CO2 fixation cycle in some autotrophic archaea. Autotrophs are organisms that can grow using carbon dioxide (CO2) as their sole source of carbon. Four mechanisms are known by which autotrophic organisms fix carbon. Berg et al. describe a fifth autotrophic CO2 fixation pathway in archaea that may have been used by some of the earliest organisms on Earth.

  9. Interface effects on elastic behavior of a screw dislocation around double nanowires

    NASA Astrophysics Data System (ADS)

    Li, Jia; Fang, Qihong; Liu, Youwen

    2014-06-01

    The elastic behavior of a screw dislocation around double nanowires (NWs) is addressed with taking into account the interface stress effect in controlling mechanical response of nanoscale structures. The stress boundary conditions at the interface of the NWs are modified by incorporating surface/interface stress. The analytic solution of complex functions of the right NW, the infinite matrix and the left NW are obtained by applying the complex variable method. The equilibrium positions and the image force acting on the dislocation of a screw dislocation near one of the NWs are discussed in detail and compared with those obtained within the classical theory of elasticity. It is shown that the NWs possess a significant local softening or hardening at the interface, which can change the nature of the equilibrium positions for the dislocation. The radius ratio between NWs has profound effects on the equilibrium position. Additionally, the soft NW with the positive interface stress inhibits the dislocation motion to enhance its own structural stability.

  10. m=1 ideal kink modes in a line-tied screw pinch with finite plasma pressure

    SciTech Connect

    Svidzinski, V. A.; Li, H. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Mirnov, V. V. [Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)

    2008-09-15

    A new method for computing ideal magnetohydrodynamic linear eigenmodes in a cylindrical screw pinch with line-tying boundary conditions at the axial ends is presented. In this method, plasma volume is reflected over one of the end planes, and equations and field components are continued into the extended volume with the continuation rules prescribed by the line-tying boundary conditions. Field components in the combined volume are expanded in Fourier series in the axial coordinate. The resulting set of coupled differential equations is solved numerically in the radial coordinate by a finite difference method yielding growth rates and eigenmodes for the system. An example of an m=1 (m is the poloidal wave number) internal kink instability in a force-free plasma equilibrium with uniform pressure is considered. In contrast to a periodic screw pinch, marginally stable perturbations are essentially compressible in the line-tied geometry. Finite compressibility makes the mode more stable in addition to the usual line-tying stabilization in zero pressure plasma. The critical length corresponding to the marginal stability increases with the increase of plasma beta. A universal axial dependence for marginally stable density perturbations {rho}(r,z)={rho}(r)exp[-iz{mu}(r)] is predicted analytically and confirmed numerically, where {mu}(r) depends on the equilibrium magnetic field components as {mu}(r)=B{sub {theta}}/rB{sub z}.

  11. Contribution of dinitrogen fixation to bacterial and primary productivity in the Gulf of Aqaba (Red Sea)

    NASA Astrophysics Data System (ADS)

    Rahav, E.; Herut, B.; Mulholland, M. R.; Voß, B.; Stazic, D.; Steglich, C.; Hess, W. R.; Berman-Frank, I.

    2013-06-01

    We evaluated the seasonal contribution of heterotrophic and autotrophic diazotrophy to the total dinitrogen (N2) fixation in a representative pelagic station in the northern Gulf of Aqaba in early spring when the water column was mixed and during summer under full thermal stratification. N2 fixation rates were low during the mixed period (˜ 0.1 nmol N L-1 d-1) and were significantly coupled with both primary and bacterial productivity. During the stratified period N2 fixation rates were four-fold higher (˜ 0.4 nmol N L-1 d-1) and were significantly correlated solely with bacterial productivity. Furthermore, while experimental enrichment of seawater by phosphorus (P) enhanced bacterial productivity and N2 fixation rates during both seasons primary productivity was stimulated by P only in the early spring. Metatranscriptomic analyses from the stratified period identified the major diazotrophic contributors as related to heterotrophic prokaryotes from the Euryarchaeota and Desulfobacterales (Deltaproteobacteria) or Chlorobiales (Chlorobia). Moreover, during this season, experimental amendments to seawater applying a combination of the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and a mixture of amino acids increased both bacterial productivity and N2 fixation rates. Our findings from the northern Gulf of Aqaba indicate a~shift in the diazotrophic community from phototrophic and heterotrophic populations, including small blooms of the cyanobacterium Trichodesmium, in winter/early spring, to predominantly heterotrophic diazotrophs in summer that may be both P and carbon limited as the additions of P and amino acids illustrated.

  12. External transpedicular fixation test of the lumbar spine correlates with the outcome of subsequent lumbar fusion.

    PubMed

    Soini, J; Slätis, P; Kannisto, M; Sandelin, J

    1993-08-01

    External transpedicular fixation was applied to the lower lumbar spine in a prospective study on 42 patients with chronic low back pain combined with suspected instability of the lumbar segments; the diagnosis was failed disk surgery, spondylolisthesis, and degenerative disk disease. The aim was to realign the involved segments, to restore disk height, and to record changes in pain and performance during the external fixation test. Pain was recorded on a visual analog scale, and performance was assessed using the Oswestry disability score. As independent observer assessed the test and treatment results. Twenty-nine patients experienced relief of pain and performed better in the fixator; they were subjected to anterior interbody fusion, the external frame being kept as a stabilizing device for an additional four months. Twenty-two patients have had follow-up evaluations for two years. One and two years after successful lumbar fusion, significantly (p < 0.02) better pain and performance scores were recorded; the results of lumbar fusion corresponded to the preoperative fixation test. A temporary external fixation test may be a useful procedure in patients considered for subsequent spondylodesis. PMID:8339515

  13. Aphotic N2 Fixation in the Eastern Tropical South Pacific Ocean

    PubMed Central

    Bonnet, Sophie; Dekaezemacker, Julien; Turk-Kubo, Kendra A.; Moutin, Thierry; Hamersley, Robert M.; Grosso, Olivier; Zehr, Jonathan P.; Capone, Douglas G.

    2013-01-01

    We examined rates of N2 fixation from the surface to 2000 m depth in the Eastern Tropical South Pacific (ETSP) during El Niño (2010) and La Niña (2011). Replicated vertical profiles performed under oxygen-free conditions show that N2 fixation takes place both in euphotic and aphotic waters, with rates reaching 155 to 509 µmol N m?2 d?1 in 2010 and 24±14 to 118±87 µmol N m?2 d?1 in 2011. In the aphotic layers, volumetric N2 fixation rates were relatively low (<1.00 nmol N L?1 d?1), but when integrated over the whole aphotic layer, they accounted for 87–90% of total rates (euphotic+aphotic) for the two cruises. Phylogenetic studies performed in microcosms experiments confirm the presence of diazotrophs in the deep waters of the Oxygen Minimum Zone (OMZ), which were comprised of non-cyanobacterial diazotrophs affiliated with nifH clusters 1K (predominantly comprised of ?-proteobacteria), 1G (predominantly comprised of ?-proteobacteria), and 3 (sulfate reducing genera of the ?-proteobacteria and Clostridium spp., Vibrio spp.). Organic and inorganic nutrient addition bioassays revealed that amino acids significantly stimulated N2 fixation in the core of the OMZ at all stations tested and as did simple carbohydrates at stations located nearest the coast of Peru/Chile. The episodic supply of these substrates from upper layers are hypothesized to explain the observed variability of N2 fixation in the ETSP. PMID:24349048

  14. Fibula fracture stabilization with a guide wire as supplementary fixation in tibia fractures.

    PubMed

    Dombroski, Derek; Scolaro, John A; Pulos, Nicholas; Beingessner, Daphne M; Dunbar, Robert; Mehta, Samir

    2012-05-01

    The tibia is the most commonly fractured long bone. Although the goals of fracture management are straightforward, methods for achieving anatomical alignment and stable fixation are limited. Type of management depends on fracture pattern, local soft-tissue involvement, and systemic patient factors. Tibial shaft fractures with concomitant fibula fractures, particularly those at the same level, may be difficult to manage because of their inherent instability. Typically, management of lower extremity fractures is focused on the tibia fixation, and the associated fibula fracture is managed without fixation. In this article, we describe a novel technique for intramedullary fixation of the fibula, using a humeral guide wire as an adjunct to tibia fixation in the setting of tibial shaft fracture. This technique aids in determining length, alignment, and rotation of the tibia fracture and may help support the lower extremity as whole by stabilizing the lateral column. In addition, this technique can be used to help maintain reduction of the fibula when there is concern about the soft tissues of the lower extremity secondary to swelling or injury. Our clinical case series demonstrates the safety, effectiveness, and cost-sensitivity of this technique in managing select concurrent fractures of the tibia and fibula. PMID:22715436

  15. Effect of banana flour, screw speed and temperature on extrusion behaviour of corn extrudates.

    PubMed

    Kaur, Amritpal; Kaur, Seeratpreet; Singh, Mrinal; Singh, Narpinder; Shevkani, Khetan; Singh, Baljit

    2015-07-01

    Effect of extrusion parameters (banana flour, screw speed, extrusion temperature) on extrusion behaviour of corn grit extrudates were studied. Second order quadratic equations for extrusion properties as function of banana flour (BF), screwspeed (SS) and extrusion temperature (ET) were computed. BF had predominant effect on the Hunter color (L*, a*, b*) parameters of the extrudates. Addition of BF resulted in corn extrudates with higher L* and lower a* and b* values. Higher ET resulted in dark colored extrudates with lower L* and a* value. Higher SS enhanced the lightness of the extrudates. Expansion of the extrudates increased with increase in the level of BF and ET. WAI of the extrudates decreased with BF whereas increased with SS. However, reversed effect of BF and SS on WSI was observed. Flextural strength of the extrudates increased with increase in SS followed by BF and ET. The addition of BF and higher ET resulted in extrudates with higher oil uptake. PMID:26139892

  16. Treatment and complications in flaccid neuromuscular scoliosis (Duchenne muscular dystrophy and spinal muscular atrophy) with posterior-only pedicle screw instrumentation

    PubMed Central

    Modi, Hitesh N.; Hong, Jae-Young; Cho, Jae-Woo; Park, Jong-Hoon; Yang, Jae-Hyuk

    2009-01-01

    Literature has described treatment of flaccid neuromuscular scoliosis using different instrumentation; however, only one article has been published using posterior-only pedicle screw fixation. Complications using pedicle screws in paralytic neuromuscular scoliosis has not been described before. To present results and complications with posterior-only pedicle screws, a retrospective study was carried out in 27 consecutive patients with flaccid neuromuscular scoliosis (Duchenne muscular dystrophy and spinal muscular atrophy), who were operated between 2002 and 2006 using posterior-only pedicle screw instrumentation. Immediate postoperative and final follow-up results were compared using t test for Cobb angle, pelvic obliquity, thoracic kyphosis and lumbar lordosis. Perioperative and postoperative complications were noted from the hospital records of each patient. Complications, not described in literature, were discussed in detail. Average follow-up was 32.2 months. Preoperative, immediate postoperative and final follow-up Cobb angle were 79.8°, 30.2° (63.3% correction, p < 0.0001) and 31.9°, respectively; and pelvic obliquity was 18.3°, 8.9° (52% correction, p < 0.0001) and 8.9°. Postoperative thoracic kyphosis remained unchanged from 27.6° to 19.9° (p = 0.376); while lumbar lordosis improved significantly from +15.6° to ?22.4° lordosis (p = 0.0002). Most patients had major to moderate improvement in postoperative functional and ambulatory status compared to the preoperative status. Thirteen (48.1%) perioperative complications were noted with five major complications (four respiratory in the form of hemothorax or respiratory failure that required ventilator support and one death) and eight minor complications (three UTI, two atelectasis, two neurological and one ileus). Postoperatively, we noted complications, such as coccygodynia with subluxation in 7, back sore on the convex side in 4 and dislodging of rod distally in 1 patient making a total of 12 (44.4%) postoperative complications. Of 12 postoperative complications, 6 (50%) required secondary procedure. We conclude that although flaccid neuromuscular scoliosis can be well corrected with posterior-only pedicle screw, there is a high rate of associated complications. PMID:19885687

  17. Clinical Results of Technique for Double Bundle Anterior Cruciate Ligament Reconstruction Using Hybrid Femoral Fixation and Retroscrew

    PubMed Central

    Kim, Doo-Sup; Yi, Chang-Ho; Chung, Hoi-Jung

    2011-01-01

    Background Anatomic anterior cruciate ligament (ACL) reconstruction has been presented as a means to more accurately restore the native anatomy of this ligament. This article describes a new method that uses a double bundle to perform ACL reconstruction and to evaluate the clinical outcome. Methods Grafts are tibialis anterior tendon allograft for anteromedial bundle (AMB) and hamstring tendon autograft without detachment of the tibial insertion for posterolateral bundle (PLB). This technique creates 2 tunnels in both the femur and tibia. Femoral fixation was done by hybrid fixation using Endobutton and Rigidfix for AMB and by biointerference screw for PLB. Tibial fixations are done by Retroscrew for AMB and by native insertion of hamstring tendon for PLB. Both bundles are independently and differently tensioned. We performed ACL reconstruction in 63 patients using our new technique. Among them, 47 participated in this study. The patients were followed up with clinical examination, Lysholm scales and International Knee Documentation Committee (IKDC) scoring system and radiological examination with a minimum 12 month follow-up duration. Results Significant improvement was seen on Lachman test and pivot-shift test between preoperative and last follow-up. Only one of participants had flexion contracture about 5 degrees at last follow-up. In anterior drawer test by KT-1000, authors found improvement from average 8.3 mm (range, 4 to 18 mm) preoperatively to average 1.4 mm (range, 0 to 6 mm) at last follow-up. Average Lysholm score of all patients was 72.7 ± 8.8 (range, 54 to 79) preoperatively and significant improvement was seen, score was 92.2 ± 5.3 (range, 74 to 97; p < 0.05) at last follow-up. Also IKDC score was normal in 35 cases, near normal in 11 cases, abnormal in 1 case at last follow-up. Conclusions Our new double bundle ACL reconstruction technique used hybrid fixation and Retroscrew had favorable outcomes. PMID:22162791

  18. Single-Dose Local Simvastatin Injection Improves Implant Fixation via Increased Angiogenesis and Bone Formation in an Ovariectomized Rat Model

    PubMed Central

    Tan, Jie; Yang, Ning; Fu, Xin; Cui, Yueyi; Guo, Qi; Ma, Teng; Yin, Xiaoxue; Leng, Huijie; Song, Chunli

    2015-01-01

    Background Statins have been reported to promote bone formation. However, taken orally, their bioavailability is low to the bones. Implant therapies require a local repair response, topical application of osteoinductive agents, or biomaterials that promote implant fixation. Material/Methods The present study evaluated the effect of a single local injection of simvastatin on screw fixation in an ovariectomized rat model of osteoporosis. Results Dual-energy X-ray absorptiometry, micro-computed tomography, histology, and biomechanical tests revealed that 5 and 10 mg simvastatin significantly improved bone mineral density by 18.2% and 22.4%, respectively (P<0.05); increased bone volume fraction by 51.0% and 57.9%, trabecular thickness by 16.4% and 18.9%, trabeculae number by 112.0% and 107.1%, and percentage of osseointegration by 115.7% and 126.3%; and decreased trabeculae separation by 34.1% and 36.6%, respectively (all P<0.01). Bone mineral apposition rate was significantly increased (P<0.01). Furthermore, implant fixation was significantly increased (P<0.05), and bone morphogenetic protein 2 (BMP2) expression was markedly increased. Local injection of a single dose of simvastatin also promoted angiogenesis. Vessel number, volume, thickness, surface area, and vascular volume per tissue volume were significantly increased (all P<0.01). Vascular endothelial growth factor (VEGF), VEGF receptor-2, von Willebrand factor, and platelet endothelial cell adhesion molecule-1 expression were enhanced. Conclusions A single local injection of simvastatin significantly increased bone formation, promoted osseointegration, and enhanced implant fixation in ovariectomized rats. The underlying mechanism appears to involve enhanced BMP2 expression and angiogenesis in the target bone. PMID:25982481

  19. A network-analysis-based comparative study of the throughput behavior of polymer melts in barrier screw geometries

    NASA Astrophysics Data System (ADS)

    Aigner, M.; Köpplmayr, T.; Kneidinger, C.; Miethlinger, J.

    2014-05-01

    Barrier screws are widely used in the plastics industry. Due to the extreme diversity of their geometries, describing the flow behavior is difficult and rarely done in practice. We present a systematic approach based on networks that uses tensor algebra and numerical methods to model and calculate selected barrier screw geometries in terms of pressure, mass flow, and residence time. In addition, we report the results of three-dimensional simulations using the commercially available ANSYS Polyflow software. The major drawbacks of three-dimensional finite-element-method (FEM) simulations are that they require vast computational power and, large quantities of memory, and consume considerable time to create a geometric model created by computer-aided design (CAD) and complete a flow calculation. Consequently, a modified 2.5-dimensional finite volume method, termed network analysis is preferable. The results obtained by network analysis and FEM simulations correlated well. Network analysis provides an efficient alternative to complex FEM software in terms of computing power and memory consumption. Furthermore, typical barrier screw geometries can be parameterized and used for flow calculations without timeconsuming CAD-constructions.

  20. Potassium fixation of different soil types and nutrient levels

    Microsoft Academic Search

    K. Sardi; G. Csitari

    1998-01-01

    Potassium (K) fixation plays a significant role in the soil?plant system influencing the effectiveness of fertilizaiton. Among the factors controlling fixation capacity of soils, clay mineralogy and soil moisture are of primary importance. The objective of this experiment was to study the K fixation capacity of different soil types and K levels as well as to develop quantitative relationships between

  1. Unfixing Design Fixation: From Cause to Computer Simulation

    ERIC Educational Resources Information Center

    Dong, Andy; Sarkar, Somwrita

    2011-01-01

    This paper argues that design fixation, in part, entails fixation at the level of meta-representation, the representation of the relation between a representation and its reference. In this paper, we present a mathematical model that mimics the idea of how fixation can occur at the meta-representation level. In this model, new abstract concepts…

  2. Eye movement and visual fixation during profound sleepiness

    Microsoft Academic Search

    W. R. Miles; H. R. Laslett

    1931-01-01

    Five college men who had gone without sleep for 66 hours were studied by photographing their eye movements and consecutive fixations of two points separated by a visual angle of 40 degrees. Speed of saccadic eye movements was 30% below normal; visual fixations were profoundly modified; corrective movements were larger and less exact; there was wavering of fixation and drifting

  3. Nitrogen control of nitrogen fixation in free-living diazotrophs

    E-print Network

    Merrick, Mike

    Chapter 9 Nitrogen control of nitrogen fixation in free-living diazotrophs M. J. MERRICK Department of nitrogen fixation is found distributed amongst a taxonomically very diverse range of microorganisms the efficiency of nitrogen fixation some common themes are now becoming clear. The physiological issues

  4. An eye fixation database for saliency detection Subramanian Ramanathan

    E-print Network

    Sebe, Nicu

    An eye fixation database for saliency detection in images Subramanian Ramanathan Harish Katti+ Nicu- an eye fixation database compiled from a pool of 758 images and 75 subjects. Eye fixations feature-driven approaches em- ployed by saliency computation algorithms. The database comprises fix- ation

  5. Systematic comparison of tissue fixation with alternative fixatives to conventional tissue fixation with buffered formalin in a xenograft-based model.

    PubMed

    Nietner, Thorben; Jarutat, Tiantom; Mertens, Alfred

    2012-09-01

    In our study we systematically compared the alternative fixatives acidified formal alcohol (AFA), PAXgene®, HOPE®, and combinations of AFA or formalin with ultrasound treatment to standard (buffered) formalin fixation. We examined general morphology and detectability of protein structures by immunohistochemistry of the membrane receptors epidermal growth factor receptor (EGFR), insulin-like growth factor 1 receptor (IGF-1R), and phosphorylated human epidermal growth factor receptor 2 (phospho-HER2). In order to allow for stringent comparability of different fixation techniques, we used matched mouse xenograft tumor samples from three different human cancer cell lines (colon, ovarian, and non-small cell lung cancer), either fixed conventionally with formalin or an alternative fixative. Tissue morphology after fixation with AFA and PAXgene® was comparable to formalin-fixed paraffin-embedded tissue (FFPET) morphology. Ultrasound fixations resulted in slightly inferior morphology and HOPE® fixation preserved morphology only poorly compared to FFPET in this system. None of the tested alternative fixatives enabled immunohistochemical detectability of all three targets in the same manner as FFPET. Pronounced staining was possible for EGFR and IGF-1R with all alternative fixatives but HOPE®, and phospho-HER2 staining was only noteworthy with formalin-ultrasound-fixed tissue. Therefore, the use of alternative fixatives comes with the need for careful validation of obtained IHC results individually for each target. PMID:22814649

  6. Nitrogen fixation : the microbial world the nitrogen cycle and nitrogen fixation

    NSDL National Science Digital Library

    Jim Deacon

    2007-01-01

    A nicely organized, reader friendly webpage. Provides a table of natural and synthetic nitrogen fixation processes. Includes photographs of plants, roots and nitrogen fixing bacteria nodules. A graphic representation of the nitrogen cycle is included.

  7. ORIGINAL ARTICLE Carbon and nitrogen fixation and

    E-print Network

    Capone, Douglas G.

    cells of Anabaena oscillarioides Radu Popa1 , Peter K Weber2 , Jennifer Pett-Ridge2 , Juliette A Finzi3 incubations of Anabaena oscillarioides, we imaged the cellular distributions of C, N and P and 13 C and 15 N: cyanobacteria; heterocyst; nitrogen fixation; nitrogenase; Anabaena Introduction Some cyanobacteria are uniquely

  8. Stability of external skeletal fixation clamps 

    E-print Network

    Sandel, Mark Eugene

    1995-01-01

    FIGURES INTRODUCTION TABLE OF CONTENTS Page 1V V1 BACKGROUND Loads Applied to Skeletal Components . . . . Terminology. . Basic Biomechanics . . . . . . . . . . . . . . . Implant Failure and Complications . . . . . . . . . . . . MEI... complications associated with the use of external fixation. This document is styled after journal of Biomechanical Engineering. Unfortunately, they did not provide any documentation on the incidence or the details of the associated complications. However...

  9. Chemical fixation of sewage sludge derived ash

    Microsoft Academic Search

    Farhana Mohamed; I. Y. Sam Cheng; Ruey S. Huang; Evelyn C. Santos

    1991-01-01

    Los Angeles processes sewage sludge by dehydration and combustion at its Hyperion Treatment Plant. The ash product is usually classified as hazardous because of its heavy metal content, and four readily?available fixing agents have been evaluated for possible use as stabilizers. The ash leachability was assessed before and after fixation using the California Waste Extraction Test. The leaching characteristics of

  10. WHITE LUPIN NITROGEN FIXATION UNDER PHOSPHORUS DEFICIENCY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    White lupin is highly adapted to growth in a low P environment. The objective of the present study was to evaluate whether white lupin grown under P-stress has adaptations in nodulation and N2 fixation that facilitate continued functioning. Nodulated plants were grown in silica sand supplied with N-...

  11. Adjustment of fixation duration in visual search

    Microsoft Academic Search

    Ignace Th. C. Hooge; Casper J. Erkelens

    1998-01-01

    To investigate whether fixation durations are adjusted to the duration of a foveal analysis task, we designed a search task in which each stimulus element yielded information about the position of the target. We asked subjects to look for the target by making eye movements in the direction indicated by each stimulus element. We explicitly asked the subjects to make

  12. Biomechanical evaluation of rotator cuff fixation methods

    Microsoft Academic Search

    E. Paul France; Lonnie E. Paulos; Chris D. Harner; Chris B. Straight

    1989-01-01

    Initial fixation strength and failure mode for various rotator cuff reattachment techniques (variations of the McLaughlin technique) were evaluated. Repair methods included standard suture (control), reinforced suture [expanded polytetrafluoroethylene (PTFE) patch and polydioxanone (PDS) tape augmentation] and stapling (nonarthroscopic and arthroscopic soft-tissue staples). The average strength of intact rotator cuff tissue (su praspinatus tendon) was also determined. The different rotator

  13. Structure of screw dislocation core in Ta at high pressure

    SciTech Connect

    Wang, Shaofeng, E-mail: sfwang@cqu.edu.cn; Jiang, Na; Wang, Rui; Zhou, Ying [Institute for Structure and Function and Department of Physics, Chongqing University, Chongqing 400030 (China)

    2014-03-07

    The core structure and Peierls stress of the 1/2 ?111?(110) screw dislocation in Ta have been investigated theoretically using the modified Peierls–Nabarro theory that takes into account the discreteness effect of crystal. The lattice constants, the elastic properties, and the generalized-stacking-fault energy(?-surface) under the different pressures have been calculated from the electron density functional theory. The core structure of dislocation is determined by the modified Peierls equation, and the Peierls stress is evaluated from the dislocation energy that varies periodically as dislocation moves. The results show the core width and Peierls stress in Ta are weakly dependent of the pressure up to 100?GPa when the length and stress are measured separately by the Burgers vector b and shear modulus ?. This indicates that core structure is approximately scaling invariant for the screw dislocation in Ta. The scaled plasticity of Ta changes little in high pressure environment.

  14. Analysis of Eyring-Powell Fluid in Helical Screw Rheometer

    PubMed Central

    Siddiqui, A. M.; Haroon, T.; Zeb, M.

    2014-01-01

    This paper aims to study the flow of an incompressible, isothermal Eyring-Powell fluid in a helical screw rheometer. The complicated geometry of the helical screw rheometer is simplified by “unwrapping or flattening” the channel, lands, and the outside rotating barrel, assuming the width of the channel is larger as compared to the depth. The developed second order nonlinear differential equations are solved by using Adomian decomposition method. Analytical expressions are obtained for the velocity profiles, shear stresses, shear at wall, force exerted on fluid, volume flow rates, and average velocity. The effect of non-Newtonian parameters, pressure gradients, and flight angle on the velocity profiles is noticed with the help of graphical representation. The observation confirmed the vital role of involved parameters during the extrusion process. PMID:24707194

  15. Structure of screw dislocation core in Ta at high pressure

    NASA Astrophysics Data System (ADS)

    Wang, Shaofeng; Jiang, Na; Wang, Rui; Zhou, Ying

    2014-03-01

    The core structure and Peierls stress of the 1/2?111?{110} screw dislocation in Ta have been investigated theoretically using the modified Peierls-Nabarro theory that takes into account the discreteness effect of crystal. The lattice constants, the elastic properties, and the generalized-stacking-fault energy(?-surface) under the different pressures have been calculated from the electron density functional theory. The core structure of dislocation is determined by the modified Peierls equation, and the Peierls stress is evaluated from the dislocation energy that varies periodically as dislocation moves. The results show the core width and Peierls stress in Ta are weakly dependent of the pressure up to 100 GPa when the length and stress are measured separately by the Burgers vector b and shear modulus ?. This indicates that core structure is approximately scaling invariant for the screw dislocation in Ta. The scaled plasticity of Ta changes little in high pressure environment.

  16. Kinematics of a Hybrid Manipulator by Means of Screw Theory

    Microsoft Academic Search

    J. GALLARDO-ALVARADO

    2005-01-01

    In this work the kinematics of a hybrid manipulator, namely a fully parallel-serial manipulator, with a particular topology\\u000a is approached by means of the theory of screws. Given the length of the six independent limbs, the forward position analysis\\u000a of the mechanism under study, indeed the computation of the resulting pose, position and orientation, of the end-platform\\u000a with respect to

  17. A magnetoelectric screw dislocation interacting with a circular layered inclusion

    Microsoft Academic Search

    Ming-Ho Shen

    2008-01-01

    Within the framework of the linear theory of magnetoelectroelasticity, the problem of a circular layered inclusion interacting with a generalized screw dislocation under remote anti-plane shear stress and in-plane magnetoelectric loads is investigated in this paper. The generalized dislocation can be located either in the matrix or in the circular layered inclusion. The layers are coaxial cylinders of annular cross-sections

  18. Suitability of DCPs with screw locking elements to allow sufficient interfragmentary motion to promote secondary bone healing of osteoporotic fractures.

    PubMed

    Cuadrado, A; Yánez, A; Carta, J A; Garcés, G

    2013-06-01

    This paper analyses the suitability of a system comprising a Dynamic Compression Plate (DCP) and Screw Locking Elements (SLEs) to allow sufficient interfragmentary motion to promote secondary bone healing in osteoporotic fractures. Four fixation systems were mounted on bone-simulating reinforced epoxy bars filled with solid rigid polyurethane foam. Group 1, used for comparison purposes, represents a system comprised of a Locking Compression Plate (LCP) and eight locking screws. Groups 2 and 3 represent a system comprised of a DCP plate with eight cortical screws and two SLEs placed on the screws furthest from (group 2) and nearest to (group 3) the fracture. Group 4 represents the system comprised of a DCP plate with SLEs placed on all eight cortical screws. Cyclic compression tests of up to 10,000 load cycles were performed in order to determine the parameters of interest, namely the stiffnesses and the interfragmentary motion of the various configurations under consideration. Tukey's multiple comparison test was used to analyse the existence or otherwise of significant differences between the means of the groups. At 10,000 cycles, interfragmentary motion at the far cortex for group 2 was 0.60±0.04 mm and for group 3 0.59±0.03 mm (there being no significant differences: p=0.995). The mean interfragmentary motion at the far cortex of the LCP construct was 70% less than that of the two groups with 2SLEs (there being significant differences: p=1.1×10(-8)). In the case of group 4 this figure was 45% less than in groups 2 and 3 (there being significant differences: p=5.6×10(-6)). At 10,000 cycles, interfragmentary motion at the near cortex for group 2 was 0.24±0.06 mm and for group 3 0.24±0.03 mm (there being no significant differences: p=1.000). The mean interfragmentary motion at the near cortex of the LCP construct was 70.8% less than that of the two groups with 2SLEs (there being significant differences: p=0.011). In the case of group 4 this figure was 66.7% less than in groups 2 and 3 (there being significant differences: p=0.016). The mean stiffness at 10,000 cycles was 960±110 N mm(-1) for group 2 and 969±53 N mm(-1) for group 3 (there being no significant differences: p=1.000). For group 1 (the LCP construct) the mean stiffness at 10,000 cycles was 3144±446 N mm(-1), 3.25 times higher than that of groups 2 and 3 (there being significant differences: p=0.00002), and 1.6 times higher than that of the DCP+8SLEs construct (1944±408 N mm(-1), there being significant differences: p=0.007). It is concluded that using the DCP+2SLEs construct sufficient interfragmentary motion is ensured to promote secondary bone healing. However, if too many SLEs are used the result may be, as with the LCP, an excessively rigid system for callus formation. PMID:22998895

  19. Decoupled Parallel Manipulator with Universal Joints and Additional Constraints

    Microsoft Academic Search

    Leonid Tyves; Victor Glazunov; Pavel Danilin; Nguyen Minh Thanh

    \\u000a Decoupled parallel manipulator with three parallel kinematic chains is considered. Each kinematic chain contains two universal\\u000a joints with additional constraints. The synthesis of this manipulator is carried out by means of screw groups. This approach\\u000a allows avoiding completed equations by synthesis and singularity analysis of mechanisms.

  20. Continuous expression of slurry in a screw press

    SciTech Connect

    Shirato, M.; Hayashi, N.; Iwata, M.; Murase, T.; Ogawa, Y.

    1985-01-01

    An approximate method is described for predicting the steadystate performance of a screw press for the continuous expression of a slurry, with the worm channel being modified as the path between two flat plates. Screw expression of a slurry involves two mechanisms of dewatering which, for a batch operation, can be analyzed by the variable-pressure, variable-rate theory of filtration and by consolidation theory. By assuming that the expression consists of a succession of batch processes, basic equations are derived for the relationship between the dehydration rate, the feed rate, and the expression pressure distribution in a constant-pitch, straighttaper screw press. The thickness of the filter cake in the worm channel and the flow distribution in the consolidated cake are calculated for a given pressure distribution and feed rate, and the solids concentration and rate of discharge of the cake are estimated. The critical speed of rotation of the worm, at which the slurry becomes highly deliquored, is strongly influenced by the external diameter and helical angle of the worm. The theoretical results are in good agreement with experimental data for clay slurries with a concentration of 0.31-0.46 in the feed.