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1

Influence of Prosthetic Screw Material on Joint Stability in Passive and Non-Passive Implant-Supported Dentures  

PubMed Central

Objectives: This study evaluated the influence of prosthetic screw material on joint stability in implantsupported dentures at two levels of fit. Methods: Ten mandibular implant-supported dentures were fabricated. Twenty cast models were fabricated using these dentures. Four groups (n=10) were tested, according to the vertical fit of the dentures [passive and non-passive] and prosthetic screw materials [titanium (Ti) or gold (Au) alloy]. The one-screw test was performed to quantify the vertical misfits using an optic microscope. The loosening torque for the prosthetic screws was measured 24 hours after the tightening torque (10 Ncm) using a digital torque meter. Data were analyzed by two-way ANOVA and Tukey’s test (?=0.05). Results: Overall, dentures with passive fit and Ti screws resulted in significantly higher loosening torque of the prosthetic screws (p<0.05). No significant interaction was found between fit level and screw material (p=0.199). The prosthetic screw material and fit of implant-supported dentures have an influence on screw joint stability. Ti screws presented higher joint stability than Au screws and minimum of misfit should be found clinically to improve the mechanical behavior of the screw joint. PMID:20148135

Spazzin, Aloísio Oro; Henriques, Guilherme Elias Pessanha; de Arruda Nóbilo, Mauro Antônio; Consani, Rafael Leonardo Xediek; Correr-Sobrinho, Lourenço; Mesquita, Marcelo Ferraz

2009-01-01

2

Influence of the implant-abutment connection design and diameter on the screw joint stability  

PubMed Central

PURPOSE This study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability. MATERIALS AND METHODS Regular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (?=0.05). RESULTS The postload removal torque value was high in the following order with regard to magnitude: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05). CONCLUSION The results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate. PMID:24843398

Shin, Hyon-Mo; Huh, Jung-Bo; Yun, Mi-Jeong; Jeon, Young-Chan; Chang, Brian Myung

2014-01-01

3

Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns  

NASA Astrophysics Data System (ADS)

The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided into 5 groups ( n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V). The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical cycling up to 106 cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical cycling. ANOVA revealed statistically significant difference ( P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited the highest misfit values. Pearson correlation test did not demonstrate significant correlation ( P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance and the abutments cast in titanium exhibited the highest misfit values.

Assunção, Wirley Gonçalves; Delben, Juliana Aparecida; Tabata, Lucas Fernando; Barão, Valentim Adelino Ricardo; Gomes, Érica Alves

2011-08-01

4

The effect of different implant-abutment connections on screw joint stability.  

PubMed

Dental implants with an internal connection have been designed to establish a better stress distribution when lateral external forces act on the prosthesis and minimize the forces transmitted to the fastening screw. In the present study, 10 externally and 10 internally hexed implants were tested with a compressive force applied with an Instron Universal machine. Four cycles of loading-unloading were applied to each specimen to achieve displacements of 0.5, 1, 2, and 2.5 mm. The mean loads for the first cycle were 256.70 N for the external connection and 256 N for the internal connection implants. The independent t test did not reveal any significant differences among the 2 tested groups (P = .780). For the second cycle, the mean loads needed for a displacement of 1 mm were 818.19 N and 780.20 N for the external connection and the internal connection implants, respectively. The independent t test revealed significant differences among the 2 tested groups (P < .001). In the third cycle, the mean load values for a 2-mm displacement were 1394.10 N and 1225.00 N. The independent t test revealed significant differences among the 2 tested groups (P < .001). The mean loads for the fourth cycle were 1488.00 N for the external connection and 1029.00 N for the internal connection implants. These loads were required for a displacement of 2.5 mm. The independent t test revealed significant differences among the 2 tested groups (P < .001). The results of this in vitro study suggest that the internal connection design of the examined implant system could not prevent screw loosening during overloading. No implant or prosthesis failure was noticed in either group. PMID:24779947

Michalakis, Konstantinos X; Calvani, Pasquale Lino; Muftu, Sinan; Pissiotis, Argiris; Hirayama, Hiroshi

2014-04-01

5

Crossed-Screws Provide Greater Tarsometatarsal Fusion Stability Compared to Compression Plates.  

PubMed

Background. Hallux valgus is a common deformity that is often treated with a fusion of the first tarsometatarsal (TMT) joint. Crossed-screws are currently the accepted standard but advances in plate systems present opportunities for improved clinical outcomes; however, in vitro testing should be performed prior to clinical implementation. The purpose of this study was to determine whether a locking plate with surgeon-mediated compression provides similar fusion stability compared to crossed-screws and if bone density or joint size are related to construct success. Methods. Ten matched-pair cadaveric specimens received first TMT fusions with either crossed-screws or a compression plate and were loaded for 1000 cycles to assess the amount of joint motion measured as plantar gapping. Bone density was quantified using computed tomography images of each specimen, and joint height was measured with calipers. Results. Crossed-screws provided 3 times greater resistance to plantar gapping compared to compression plates after 1000 cycles. Bone density and joint size did not affect resistance to plantar gapping for either construct. Conclusion. Lag screws or a plantarly applied plate are needed to maximize TMT fusion stability prior to osseous union. Dorsomedially applied plates are also effective when paired with a lag screw placed across the TMT joint. These constructs do not appear to depend on bone density or joint size, suggesting that patients with osteoporosis are viable candidates. Clinical Relevance. The results of this study suggest that traditional, lagged cross-screws provide greater stability to that of a dorsally place compression plate and may lead to better rates of union. PMID:25053793

Baxter, Josh R; Mani, Sriniwasan B; Chan, Jeremy Y; Vulcano, Ettore; Ellis, Scott J

2014-07-21

6

Anterior transarticular screw fixation as a conventional operation for rigid stabilization  

PubMed Central

Background: Anterior transarticular screw (ATS) fixation is a useful surgical option for atlantoaxial (AA) stabilization. This report presents a revised ATS method for AA fusion. Methods: A 79-year-old male presented with AA instability attributed both to an old odontoid fracture and severe degeneration of the lateral atlantoaxial joints (LAAJs). ATS fixation was performed through the conventional anterior cervical approach. The longest screw trajectories were planned preoperatively using multiplanar reconstruction computed tomography (CT) scans, with entry points of the screws situated at the midpoint on the inferior border of the axial body. The surgical exposure was limited to opening at the entry points alone. Our retractor of choice was the Cusco speculum; it sufficiently secured space for utilizing the required instruments for screw placement while offering sufficient protection of soft tissues. Cannulated full-threaded bicortical screws stabilized the LAAJs. Screw insertion required a significant amount of coronal angulation up to the superior articular process of the atlas under open-mouth and lateral fluoroscopy image guidance. After ATS fixation, bone grafting was performed between the posterior laminae of the axis and the atlas through a conventional posterior approach. Results: Bony fusion between the atlas and the axis was confirmed radiographically. Arthrodesis of the LAAJs occurred despite no bone grafting. Conclusions: Rigid fixation of the LAAJs was obtained by our ATS technique, indicating that it is an alternative method for AA fixation when posterior rigid internal fixation is not applicable.

Sasaki, Manabu; Matsumoto, Katsumi; Tsuruzono, Koichiro; Yoshimura, Kazuhiro; Shibano, Katsuhiko; Yonenobu, Kazuo

2014-01-01

7

Torsional stability of interference screws derived from bovine bone - a biomechanical study  

Microsoft Academic Search

BACKGROUND: In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws. METHODS: In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC) and a

Joscha Bauer; Turgay Efe; Silke Herdrich; Leo Gotzen; Bilal Farouk El-Zayat; Jan Schmitt; Nina Timmesfeld; Markus Dietmar Schofer

2010-01-01

8

Proponents of fixation of an ACL graft at the joint line with an interference screw base their opinions on several  

E-print Network

anterior laxity and knee stiffness as well as joint line fixation with an interference screw in human bone of the bone were reconstructed with a double-looped tendon graft and fixed with an interference screw and 3Proponents of fixation of an ACL graft at the joint line with an interference screw base

Hull, Maury

9

Torsional stability of interference screws derived from bovine bone - a biomechanical study  

PubMed Central

Background In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws. Methods In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC) and a commercial 8 mm interference screw (Tutofix®). Furthermore, we compared the torsional strength of BC screws with different diameters. For screwing in, a hexagon head and an octagon head were tested. Maximum breaking torques in polymethyl methacrylate resin were recorded by means of an electronic torque screw driver. In the second part of the study the tibial part of a bone-patellar tendon-bone graft was fixed in porcine test specimens using an 8 mm BC screw and the maximum insertion torques were recorded. Each interference screw type was tested 5 times. Results There was no statistically significant difference between the different 8 mm interference screws (p = 0.121). Pairwise comparisons did not reveal statistically significant differences, either. It was demonstrated for the BC screws, that a larger screw diameter significantly leads to higher torsional stability (p = 9.779 × 10-5). Pairwise comparisons showed a significantly lower torsional stability for the 7 mm BC screw than for the 8 mm BC screw (p = 0.0079) and the 9 mm BC screw (p = 0.0079). Statistically significant differences between the 8 mm and the 9 mm BC screw could not be found (p = 0.15). During screwing into the tibial graft channel of the porcine specimens, insertion torques between 0.5 Nm and 3.2 Nm were recorded. In one case the hexagon head of a BC screw broke off during the last turn. Conclusions The BC screws show comparable torsional stability to Tutofix® interference screws. As expected the torsional strength of the screws increases significantly with the diameter. The safety and in vivo performance of products derived from xenogeneic bone should be the focus of further investigations. PMID:20433761

2010-01-01

10

Small Joint Fusions of the Hand using the Herbert Bone Screw  

Microsoft Academic Search

The Herbert Bone Screw has a thread at both ends and was originally developed for internal fixation of fractured scaphoid bones. The two main advantages of compression and no head, make it most suitable for internal splinting of the small joints of the hand.The authors have used this device on thirty-nine joints in ten different sites of the hand, and

D. K. FAITHFULL; T. J. HERBERT

1984-01-01

11

Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage  

Microsoft Academic Search

Recently, implant anchors such as titanium screws have been used for absolute anchorage during edgewise treatment. However, there have been few human studies reporting on the stability of implant anchors placed in the posterior region. The purpose of this study was to examine the success rates and to find the factors associated with the stability of titanium screws placed into

Shouichi Miyawaki; Isao Koyama; Masahide Inoue; Katsuaki Mishima; Toshio Sugahara; Teruko Takano-Yamamoto

2003-01-01

12

A retrospective comparison of four plate constructs for first metatarsophalangeal joint fusion: static plate, static plate with lag screw, locked plate, and locked plate with lag screw.  

PubMed

The primary treatment for progressive first metatarsophalangeal (MTP) joint arthritis is arthrodesis. Multiple fixation types have been used to accomplish fusion including plating. There have been no published articles reporting the outcomes of these 4 plate and/or screw constructs. We present our experience with 138 first MTP joint fusions using these constructs. A retrospective comparison and radiographic chart review of 132 patients (138 feet) was performed to compare different constructs in regards to successful union and time to fusion. All operations were performed by 4 fellowship-trained foot and ankle surgeons. The radiographs were independently read by 2 authors not involved in the index procedures. Radiographic fusion was determined by bridging cortices across the joint line. The mean time to union (in days) and rate of fusion were static plate: 59, 95%, static plate with lag screw: 56, 86%, locked plate: 66, 92%, and locked plate with lag screw: 53, 96%. There was not a statistically significant difference between the groups in regards to patient age, time to weight bearing, time to fusion, or rate of fusion. We report on the results of fusion comparing 4 different plate and/or screw constructs for first MTP joint fusion. The data reveal no significant difference in time to fusion or rate of fusion between static and locked plates, with or without a lag screw. PMID:22459423

Hyer, Christopher F; Scott, Ryan T; Swiatek, Michael

2012-01-01

13

Disc-repositioning surgery of the temporomandibular joint using bioresorbable screws.  

PubMed

For successful disc-repositioning surgery, following arthrotomy and disc recovery by the release of attachments, the disc must be fixed and stabilized in the correct relationship with the condyle and fossa. This report describes a new surgical technique for fixing the disc to the condyle using two resorbable screws. PMID:16962741

Sembronio, S; Robiony, M; Politi, M

2006-12-01

14

Preload Analysis of Screw Bolt Joints on the First Wall Graphite Tiles in EAST  

NASA Astrophysics Data System (ADS)

The first wall in the Experimental Advanced Superconducting Tokamak (EAST) used graphite tiles to withstand high thermal energy. The graphite tiles are mounted on the heat sink using screw bolts which have been preloaded to produce a clamp force. The clamp force is very important to keep the graphite tiles tightly on the surface of the heat sink so that the heat flux crosses this contacting surface in a small thermal resistor. Without the clamp force, the small gap between the graphite tiles and the heat sink will make it impossible for thermal power to be carried away by cooling water. Some bolts may even fall off with the loss of clamp force. From the mathematical models, the loss process of the clamp force has been studied. Research results explain how the different thermal expansions of three members of the screw joint makes the clamp force decrease to zero under temperature rise and external force, and how the stiffness affects the relation between the clamp force and temperature. The research also gives the critical temperature at which the clamp force can remain above zero. Analysis results indicate that the current screw joints are almost destined to lose their clamp force during the running time of EAST, so the bolt joints should be redesigned in order to improve its reliability.

Cao, Lei; Song, Yuntao

2012-09-01

15

Acromioclavicular Joint Fixation Using an Acroplate Combined With a Coracoclavicular Screw  

PubMed Central

Background Appropriate treatment of acromioclavicular joint dislocation is controversial. Acroplate fixation is one of the most common treatment methods of acromioclavicular joint (ACJ) dislocation. Based on the risk of re-dislocation after Acroplate fixation, we assumed that combined fixation with an Acroplate and a coracoclavicular screw helps improve the outcome. Objectives The main purpose of the current study was to compare the outcome of ACJ dislocation treated with an Acroplate alone and in combination with coracoclavicular screw. Patients and Methods This study was carried out on 40 patients with ACJ dislocation types III to VI who were divided randomly into two equal groups: Acroplate group (P) and Acroplate in combination with coracoclavicular screw group (P + S). The screws were extracted 3-6 months postoperatively. The patients were followed for 1 year and Imatani’s score was calculated. Finally, the data were compared between the groups. Results The mean Imatani’s score was significantly higher in P + S group (83.4 ± 14.1) than P group (81.2 ± 10.3) (P < 0.001). The mean duration of surgery was the same in the two groups (59.8 ± 9.4 minutes in group P V.s 64.3 ± 10.9 minutes in group P + S; P = 0.169). There were no cases of re-dislocation, degenerative changes and ossification and all patients returned to their previous jobs or sporting activities. Conclusions Using a coracoclavicular screw combined with an Acroplate can improve the patients’ function after ACJ disruption without any significant increase in surgical duration. Authors recommend this technique in the fixation of ACJ dislocation. PMID:24396788

Tavakoli Darestani, Reza; Ghaffari, Arash; Hosseinpour, Mehrdad

2013-01-01

16

Stability of two-fold screw axis structures for cellulose  

Technology Transfer Automated Retrieval System (TEKTRAN)

Diffraction crystallography indicates that most forms of crystalline cellulose have two-fold screw axis symmetry. Even if exact symmetry is absent, the degree of pseudo symmetry is very high. On the other hand, this symmetry leads to short contacts between H4 and H1' across the glycosidic linkage....

17

The study of lifetime of polymer and composite bone joint screws under cyclical loads and in vitro conditions  

Microsoft Academic Search

The “strain-life time” method has been adapted for life-time prediction of polymer and composite bone joint screws. Mechanical\\u000a and fatigue properties of screws made of biostable (polysulfone), biosorbable (poly(lactide-co-glycolide) and short carbon\\u000a fibre reinforced polymer composite materials have been examined in this study. The lifetime predictions under in vitro conditions were calculated for polymer and composite implants. The forecasting of

Ch?opek Jan; Kmita Grzegorz

2005-01-01

18

Comparison of in-vitro motion and stability between techniques for index metacarpophalangeal joint radial collateral ligament reconstruction  

PubMed Central

Purpose To evaluate a technique using interference screws to reconstruct the radial collateral ligament (RCL) of the index finger metacarpophalangeal (MP) joint. We hypothesized that this technique would provide equivalent stability and flexion as a 4-tunnel reconstruction. Methods The RCL was isolated in 17 cadaveric index fingers. A cyclic load was applied to the intact RCL across the MP joint to assess flexion, ulnar deviation at neutral (UD@0), and ulnar deviation at 90° of MP joint flexion (UD@90). The RCL was excised from its bony origin and insertion. Each reconstruction (4-tunnel and interference screw) was performed sequentially on each specimen in randomized order. Testing was repeated after each reconstruction. Differences from the intact state were compared between the techniques using paired t-tests for all joint positions (flexion/UD@0/UD@90). Results There was no statistically significant difference in UD@0 or UD@90 between the intact state and after interference screw reconstruction. Compared to the intact state, there was significantly less UD@0 and significantly more UD@90 after 4-tunnel reconstruction. There was no statistically significant difference between techniques when comparing change in -UD@0 or change in UD@90. Change in flexion was statistically significantly different, indicating that the interference screw technique better replicated intact MP joint flexion compared to the 4-tunnel technique. Discussion Interference screw reconstruction of the index RCL provided stability comparable to 4-tunnel reconstruction but is less technically challenging. These results substantiate our clinical experience that interference screw technique provides an optimal combination of stability and flexion at the index MP joint. Clinical Relevance Using an interference screw to reconstruct the index RCL is less challenging and provides stability and range of motion that closely resembles the native MP joint. PMID:23747165

Dy, Christopher J.; Tucker, Scott M.; Carlson, Michelle Gerwin

2013-01-01

19

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

NASA Astrophysics Data System (ADS)

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.

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

20

Painful knee joint after ACL reconstruction using biodegradable interference screws- SPECT/CT a valuable diagnostic tool? A case report  

PubMed Central

With the presented case we strive to introduce combined single photon emission computerized tomography and conventional computer tomography (SPECT/CT) as new diagnostic imaging modality and illustrate the possible clinical value in patients after ACL reconstruction. We report the case of a painful knee due to a foreign body reaction and delayed degradation of the biodegradable interference screws after ACL reconstruction. The MRI showed an intact ACL graft, a possible tibial cyclops lesion and a patella infera. There was no increased fluid collection within the bone tunnels. The 99mTc-HDP-SPECT/CT clearly identified a highly increased tracer uptake around and within the tibial and femoral tunnels and the patellofemoral joint. On 3D-CT out of the SPECT/CT data the femoral graft attachment was shallow (50% along the Blumensaat's line) and high in the notch. At revision arthroscopy a diffuse hypertrophy of the synovium, scarring of the Hoffa fat pad and a cyclops lesion of the former ACL graft was found. The interference screws were partially degraded and under palpation and pressure a grey fluid-like substance drained into the joint. The interference screws and the ACL graft were removed and an arthrolysis performed. In the case presented it was most likely a combination of improper graft placement, delayed degradation of the interference screws and unknown biological factors. The too shallow and high ACL graft placement might have led to roof impingement, chronic intraarticular inflammation and hence the delayed degradation of the screws. SPECT/CT has facilitated the establishment of diagnosis, process of decision making and further treatment in patients with knee pain after ACL reconstruction. From the combination of structural (tunnel position in 3D-CT) and metabolic information (tracer uptake in SPECT/CT) the patient's cause of the pain was established. PMID:20846410

2010-01-01

21

Clinical application of combined fixation in the cervical spine using posterior transfacet screws and pedicle screws.  

PubMed

The aim of the present study was to describe the clinical application of combined fixation in the cervical spine using posterior transfacet and pedicle screws. Ten patients with cervical disorders requiring stabilization were treated from May 2006 to December 2008. The operative details varied depending on indication, the need for decompression, and the number of levels to be included in the spinal construct. Radiographic analysis of the fusion was performed after surgery. A total of 23 transfacet screws were inserted at or caudal to the C4/5 facet. A total of 21 pedicle screws were placed. All patients underwent operative treatment without neurovascular complications. Fusion was achieved in all patients. When performed appropriately, the method of using posterior transfacet screws in the caudal cervical joints combined with pedicle screw fixation in the cephalic cervical spine is reliable and deserves more widespread use. PMID:23232101

Liu, Guanyi; Ma, Weihu; Xu, Rongming; Godinsky, Ryan; Sun, Shaohua; Feng, Jianxiang; Zhao, Liujun; Hu, Yong; Zhou, Leijie; Liu, Jiayong

2013-04-01

22

Abrasion of abutment screw coated with TiN  

PubMed Central

STATEMENT OF PROBLEM Screw loosening has been a common complication and still reported frequently. PURPOSE The purpose of this study was to evaluate abrasion of the implant fixture and TiN coated abutment screw after repeated delivery and removal with universal measuring microscope. MATERIAL AND METHODS Implant systems used for this study were Osstem and 3i. Seven pairs of implant fixtures, abutments and abutment screws for each system were selected and all the fixtures were perpendicularly mounted in liquid unsaturated polyesther with dental surveyor. After 20 times of repeated closing and opening test, the evaluation for the change of inner surface of implant and TiN-coated abutment screw, and weight loss were measured. Mann-Whitney test with SPSS statistical software for Window was applied to analyze the measurement of weight loss. RESULTS TiN-coated abutment screws of Osstem and 3i showed lesser loss of weight than non-coated those of Osstem and 3i (P < .05, Mann-Whitney test). CONCLUSION Conclusively, TiN coating of abutment screw showed better resistance to abrasion than titanium abutment screw. It was concluded that TiN coating of abutment screw would reduce the loss of preload with good abrasion resistance and low coefficient of friction, and help to maintain screw joint stability. PMID:21165263

Jung, Seok-Won; Son, Mee-Kyoung; Chung, Chae-Heon

2009-01-01

23

46 CFR 154.524 - Piping joints: Welded and screwed couplings.  

Code of Federal Regulations, 2012 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2012-10-01

24

46 CFR 154.524 - Piping joints: Welded and screwed couplings.  

Code of Federal Regulations, 2011 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2011-10-01

25

46 CFR 154.524 - Piping joints: Welded and screwed couplings.  

Code of Federal Regulations, 2010 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2010-10-01

26

46 CFR 154.524 - Piping joints: Welded and screwed couplings.  

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2014-10-01

27

46 CFR 154.524 - Piping joints: Welded and screwed couplings.  

Code of Federal Regulations, 2013 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2013-10-01

28

Comparison of cranial facet joint violation rate between percutaneous and open pedicle screw placement: a systematic review and meta-analysis.  

PubMed

Percutaneous and open pedicle screw placements have been widely used in lumbar fusion surgery. However, there are conflicting reports of cranial facet joint violation rate for the 2 techniques.To better determine the rate of cranial facet joint violation, a systematic review and meta-analysis was performed in the present study.We searched the established electronic literature databases including MEDLINE, EMBASE, World of Science, and the Cochrane Central Register of Controlled Trials databases for trials involving the 2 pedicle screw placement techniques. Odds ratio (OR) and 95% confidence interval (CI) were calculated.Four comparative trials with a cumulative sample size of 881 patients and 1755 cranial pedicle screws were identified and analyzed. The results showed that cranial facet joint violation rate was 18.18% (154/847) in percutaneous group and 18.72% (170/908) in open group. The pooled data revealed that there was no significant difference in the violation rate (OR 0.75, 95% CI 0.24-2.30, P?=?0.62). In addition, there was also no significant difference for the rate of severe violation between the 2 techniques (OR 1.20, 95% CI 0.55-2.62, P?=?0.64, random effect model).Based on the current data, the meta-analysis shows that similar cranial facet joint violation rate occurs during the percutaneous and open pedicle screw placement techniques. In addition, taking the limitations of this study into consideration, it was still not appropriate to draw such a strong conclusion. More well-designed prospective randomized controlled trials are needed to assess violation rate for the 2 techniques in the future. PMID:25654397

Wang, Liang; Wang, Yipeng; Yu, Bin; Li, Zhengyao; Li, Ye

2015-02-01

29

Stability conditions of prestressed pin-jointed structures  

Microsoft Academic Search

Pin-jointed structures are first classified to trusses, tensile structures, and tensegrity structures in view of their respective stability properties. A sufficient condition for stability of an equilibrium state is derived for tensegrity structures. The condition is based on the bilinear forms of the linear and geometrical stiffness matrices considering the flexibility of members. The stability is defined by the positive

Makoto Ohsaki; Jingyao Zhang

2006-01-01

30

Internal reduction established by occiput-C2 pedicle polyaxial screw stabilization in pediatric atlantoaxial rotatory fixation.  

PubMed

Atlantoaxial rotatory fixation is an uncommon disorder of childhood, which can be treated conservatively when diagnosed 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 needed to prevent future head and neck deformity or facial asymmetry. In this report we describe a novel surgical technique used in a pediatric case presenting with delayed type 2 atlantoaxial rotatory fixation, in whom all external reduction methods had failed. The patient's deformity was treated by occiput-C2 pedicle polyaxial screw stabilization. This technique is effective for reducing the atlantoaxial fixation in children. PMID:16902349

Belen, Deniz; Simsek, Serkan; Yigitkanli, Kazim; Bavbek, Murad

2006-01-01

31

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

PubMed Central

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

2014-01-01

32

Non-fusion stabilization of the lumbar spine in the case of degenerative diseases with a dynamic pedicle screw rod Estabilização dinâmica da coluna lombar no tratamento das doenças degenerativas ARTIGO ORIGINAL \\/ ORIGINAL ARTICLE  

Microsoft Academic Search

Objective: To compare the results of the posterior non-fusion stabilizations and fusion in the treatment of painful degenerative diseases of the lumbar spine. Methods: Cosmic is a dynamic non-fusion pedicle screw rod system for the stabilization of the lumbar vertebral column. The hinged pedicle screw provides for the load being shared between the implant and the vertebral column and allows

Archibald von Strempel; Christoph Stoss; Dieter Moosmann; Arno Martin

33

Biomechanical In Vitro - Stability Testing on Human Specimens of a Locking Plate System Against Conventional Screw Fixation of a Proximal First Metatarsal Lateral Displacement Osteotomy  

PubMed Central

Introduction: The aim of this study was to examine resistance to angulation and displacement of the internal fixation of a proximal first metatarsal lateral displacement osteotomy, using a locking plate system compared with a conventional crossed screw fixation. Materials and Methodology: Seven anatomical human specimens were tested. Each specimen was tested with a locking screw plate as well as a crossed cancellous srew fixation. The statistical analysis was performed by the Friedman test. The level of significance was p = 0.05. Results: We found larger stability about all three axes of movement analyzed for the PLATE than the crossed screws osteosynthesis (CSO). The Friedman test showed statistical significance at a level of p = 0.05 for all groups and both translational and rotational movements. Conclusion: The results of our study confirm that the fixation of the lateral proximal first metatarsal displacement osteotomy with a locking plate fixation is a technically simple procedure of superior stability. PMID:22675409

Arnold, Heino; Stukenborg-Colsman, Christina; Hurschler, Christof; Seehaus, Frank; Bobrowitsch, Evgenij; Waizy, Hazibullah

2012-01-01

34

Biomechanical stability of a supra-acetabular pedicle screw Internal Fixation device (INFIX) vs External Fixation and plates for vertically unstable pelvic fractures  

PubMed Central

Background We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model. Methods Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons Results The mean displacement at the pubic symphysis was 20, 9 and 0.8?mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P?=?0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P?=?0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups. Conclusions Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used. PMID:23017093

2012-01-01

35

Muscle contribution to elbow joint valgus stability Fang Lin, DSc,a,b,c  

E-print Network

Muscle contribution to elbow joint valgus stability Fang Lin, DSc,a,b,c Navjot Kohli, MD,d Sam stabilizer for elbow valgus stability, incorporating with the MUCL for all tested joint configurations. Our by several authors.19,32,33 However, little is known about the dynamic stability of the elbow joint--that is

Makhsous, Mohsen

36

An experimental study of the biomechanical stability of ultrasound-activated pinned (SonicWeld Rx ® + Resorb-X ®) and screwed fixed (Resorb-X ®) resorbable materials for osteosynthesis in the treatment of simulated craniosynostosis in sheep  

Microsoft Academic Search

We compared a conventional resorbable screw osteosynthesis with a resorbable, ultrasound-activated pin osteosynthesis, and studied mechanical load capacity and operative handling. This new form of osteosynthesis aims to reduce operation times, and to avoid torque loads and screw fractures to achieve stability.A sheep craniotomy model simulated an operation for dysmorphia on an infant skull. Two rectangular craniotomies of equal size

E. Pilling; H. Meissner; R. Jung; R. Koch; R. Loukota; R. Mai; B. Reitemeier; G. Richter; B. Stadlinger; E. Stelnicki; U. Eckelt

2007-01-01

37

The Effects of Screw Length on Stability of Simulated Osteoporotic Distal Radius Fractures Fixed with Volar Locking Plates  

PubMed Central

Purpose Volar plating for distal radius fractures has caused extensor tendon ruptures secondary to dorsal screw prominence. This study was designed to determine the biomechanical impact of placing unicortical distal locking screws and pegs in an extra-articular fracture model. Methods Volar-locking distal radius plates were applied to 30 osteoporotic distal radius models. Radii were divided into 5 groups based on distal locking fixation: bicortical locked screws, 3 lengths of unicortical locked screws (abutting the dorsal cortex [full length], 75% length, and 50% length to dorsal cortex), and unicortical locked pegs. Distal radius osteotomy simulated a dorsally comminuted, extra-articular, fracture. Each constructs stiffness was determined under physiologic loads (axial compression, dorsal bending volar bending) before and after 1000 cycles of axial conditioning and prior to axial loading to failure (2mm of displacement) and subsequent catastrophic failure. Results Cyclic conditioning did not alter constructs stiffness. Stiffness to volar bending and dorsal bending forces were similar between groups. Final stiffness(N/mm) under axial load was statistically equivalent for all groups: bicortical screws(230), full-length unicortical screws(227), 75% length unicortical screws(226), 50% length unicortical screws(187), unicortical pegs(226). Force(N) at 2 mm displacement was significantly less for 50% length unicortical screws(311) compared to bicortical screws(460), full-length unicortical screws(464), 75% length unicortical screws(400), and unicortical pegs(356). Force(N) to catastrophic fracture was statistically equivalent between groups but mean values for pegs(749) and 50% length unicortical(702) screws were 16-21% less than means for bicortical(892), full-length unicortical(860), and 75% length(894) unicortical constructs. Discussion Locked unicortical distal screws of at least 75% length produce construct stiffness similar to bicortical fixation. Unicortical distal fixation for extra-articular distal radius fractures should be entertained to avoid extensor tendon injury since it does not appear to compromise initial fixation. Clinical Relevance Biomechanical comparison of distal fixation techniques during volar locked plating for distal radius fracture. PMID:22305729

Wall, Lindley B.; Brodt, Michael D.; Silva, Matthew J.; Boyer, Martin I.; Calfee, Ryan P.

2013-01-01

38

Ankle syndesmotic fixation using two screws: risk of injury to the perforating branch of the peroneal artery.  

PubMed

Trans-syndesmotic screws are commonly used to repair syndesmosis ruptures and stabilize the ankle joint. Just as with any surgery, the neurovascular structures can be compromised, causing complications. We evaluated the position of the perforating branch of the peroneal artery to define the risk of arterial compromise during placement of 2 trans-syndesmotic screws. In 37 cadaveric specimens, 2 trans-syndesmotic screws were inserted 2 and 4 cm proximal to the ankle joint. The distances between the perforating branch of the peroneal artery and the screws and the other anatomic landmarks were measured. Significant differences were calculated between the male and female limbs, and regression analysis was used to determine the significant associations between the tibial length and screw location. The perforating branch of the peroneal artery passed through the interosseous membrane 3.42 ± 0.6 cm proximal to the tibial plafond. The artery was located up to 4 mm from the superior and inferior screws 51.4% and 10.8% of the time, respectively. A greater percentage of male specimens displayed close proximity between the artery and the superior screw, and the distance of the artery from the distal fibula was statistically significant compared with the distance in the female specimens. Regression analysis revealed that the greater the tibial length, the closer the superior screw was to the artery, with a negative correlation discovered for the inferior screw. We concluded that superior screw placement increased the risk of injuring the perforating branch of the peroneal artery injury, and the likelihood of injuring the artery with the inferior screw increased as the length of the tibia decreased. PMID:24875967

Penera, Keith; Manji, Karim; Wedel, Mathew; Shofler, David; Labovitz, Jonathan

2014-01-01

39

Human-Humanoid Joint Haptic Table Carrying Task with Height Stabilization using Vision  

E-print Network

Human-Humanoid Joint Haptic Table Carrying Task with Height Stabilization using Vision Don Joven, a first step is taken towards using vision in human-humanoid haptic joint actions. Haptic joint actions robot. We then demonstrate all this by an experiment where a human and the HRP-2 humanoid jointly

Paris-Sud XI, Université de

40

Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems  

PubMed Central

PURPOSE This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material. PMID:25551010

Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung

2014-01-01

41

Clinical study of temporary anchorage devices for orthodontic treatment--stability of micro/mini-screws and mini-plates: experience with 455 cases.  

PubMed

The aim of this retrospective study was to determine factors that might cause complications in use of temporary anchorage devices (TADs) for orthodontic anchorage. We investigated 904 TADs in 455 patients. Clinical diagnoses requiring orthodontic treatment were malocclusion, jaw deformity, various syndromes, cleft lip and palate and impacted teeth. All patients underwent surgery at Tokyo Dental College Chiba Hospital between November 2000 and June 2009. Three kinds of titanium screw of different diameter and length were used: self-drilling mini-screws (Dual Top Autoscrew® and OSAS®), pre-drilling micro-screws (K1 system®) and palatal screws (PIAS®). Mini-plates fixed with 2 or 3 screws (SAS system®) were also used for skeletal anchorage. Patients were aged between 8 and 68 years (25.7±9.8 years). A total of 460 screw-type and 444 plate-type TADs were used. These comprised the following: mini-plates, 444; self-drilling mini-screws, 225; pre-drilling micro-screws, 83; and palatal screws, 152. Each type of implant had a high success rate of over about 90%. Failure rates were as follows: micro-screws, 7%; mini-screws, 6%; palatal implants, 11%; and mini-plates, 6%. Inflammation rate occurring in soft tissue surrounding TADs was follows: plate-type, 7.6%; mini-screws, 1.3%; micro-screws, 0%; and palatal implants, 2.5%. Inflammation frequencies depended on degree of mucosal penetration. Granulation rate in soft tissue surrounding TADs occurred as follows: micro-screws, 5.7%; self-drilling mini-screws, 0%; palatal screws, 0.6%; plate-type, 0.9%. Both plate- and screwtype orthodontic implants showed excellent clinical performance. PMID:20877162

Takaki, Takashi; Tamura, Naoki; Yamamoto, Masae; Takano, Nobuo; Shibahara, Takahiko; Yasumura, Toshihiko; Nishii, Yasushi; Sueishi, Kenji

2010-01-01

42

The beauty of stability: distal radioulnar joint stability in arthroscopic triangular fibrocartilage complex repair.  

PubMed

The triangular fibrocartilage complex (TFCC) has an important role in the stability of the distal radioulnar joint (DRUJ) stability. We designed a new method of TFCC tear repair that has satisfactory post-operative DRUJ stability. From May 2004 to August 2010, 14 patients who underwent this operation were reviewed. The average post-operative follow-up period was 8.2 months; 66.7% of the patients with TFCC tear in sigmoid notch had clinical DRUJ instability, while only 50% of tear in fovea and 16.7% of tear in base of ulnar styloid had clinical DRUJ instability. Transosseous suture via inside-outside technique was used for repair. At the final follow-up, all 14 patients have soft end point with < 5 mm translations of the DRUJ shown by the stress test. Based on this small sample with satisfactory outcome assessed by the Mayo modified wrist score and DRUJ stability, we recommend TFCC tear in sigmoid notch, which has a higher chance of DRUJ instability, to be repaired by transosseous suture. PMID:23413845

Tang, Chris; Fung, Boris; Chan, Rebecca; Fok, Margaret

2013-01-01

43

The mast cell stabilizer ketotifen reduces joint capsule fibrosis in a rabbit model of post-traumatic joint contractures  

PubMed Central

Objectives Using a rabbit model of post-traumatic joint contractures, we investigated whether treatment with a mast cell stabilizer after joint injury would lessen the molecular manifestations of joint capsule fibrosis. Methods Surgical joint injury was used to create stable post-traumatic contractures of the knee in skeletally mature New Zealand white rabbits. Four groups of animals were studied: a non-operated control group (n = 8), an operated contracture group (n = 13) and two operated groups treated with the mast cell stabilizer, ketotifen, at doses of 0.5 mg/kg (n = 9) and 1.0 mg/kg (n = 9) twice daily. Joint capsule fibrosis was assessed by quantifying the mRNA and protein levels of ?-SMA, tryptase, TGF-?1, collagen I and collagen III. Significance was tested using an ANOVA analysis of variance. Results The protein and mRNA levels of ?-SMA, TGF-?1, tryptase and collagen I and III were significantly elevated in the operated contracture group compared to control (p < 0.01). In both ketotifen-treated groups, protein and mRNA levels of ?-SMA, TGF-?1 and collagen I were significantly reduced compared to the operated contracture group (p < 0.01). Conclusions These data suggest an inflammatory pathway mediated by mast cell activation is involved in joint capsule fibrosis after traumatic injury. PMID:22173279

Hart, David A.; Befus, A. Dean; Salo, Paul T.; Zhang, Mei; Hildebrand, Kevin A.

2013-01-01

44

Understanding stability of the distal radioulnar joint through an understanding of its anatomy.  

PubMed

The authors describe the anatomy of the distal radioulnar joint (DRUJ) and delineate the importance of viewing this joint as part of the whole forearm. The osseous congruity and ligamentous integrity is of essence for the stability of the DRUJ, according to the principles of tensegrity. The neuromuscular control and possible proprioceptive function of the DRUJ are also outlined. PMID:20951895

Hagert, Elisabet; Hagert, Carl-Göran

2010-11-01

45

Comparison of Cotrel-Dubousset pedicle screws and hooks in the treatment of idiopathic scoliosis  

Microsoft Academic Search

Eighty-two patients with idiopathic scoliosis were treated by Cotrel-Dubousset instrumentation between 1987 and 1991. Twenty were treated with hooks only, 47 with screws and hooks, and 15 with screws only. The methods were compared and the findings showed that screw fixation can be used in the thoracic spine without neurological complications. The screws provided immediate stability with rigid fixation, together

S. I. Suk; C. K. Lee; H. J. Min; K. H. Cho; J. H. Oh

1994-01-01

46

Joint Scalar versus Joint Velocity-Scalar PDF Simulations of Bluff-Body Stabilized Flames with REDIM  

Microsoft Academic Search

Two transported PDF strategies, joint velocity-scalar PDF (JVSPDF) and joint scalar PDF (JSPDF), are investigated for bluff-body\\u000a stabilized jet-type turbulent diffusion flames with a variable degree of turbulence–chemistry interaction. Chemistry is modeled\\u000a by means of the novel reaction-diffusion manifold (REDIM) technique. A detailed chemistry mechanism is reduced, including\\u000a diffusion effects, with N\\u000a 2 and CO\\u000a 2 mass fractions as reduced

B. Merci; B. Naud; D. Roekaerts; U. Maas

2009-01-01

47

Effect of the application of local vibration in scaption on joint stability  

PubMed Central

[Purpose] The aim of this study was to determine the initial effect of local vibration on the stability of the shoulder joints by applying local vibration to the shoulder joints. [Subjects and Methods] For the test, the subjects held a FlexBar with one hand, at about 10?cm from one end, and performed the oscillation movement with the shoulder at 90° flexion and the elbow in the full-extension position in scaption; the vibration stimulus was set to 5?Hz. Then, the subjects underwent the Upper Quarter Y Balance Test to evaluate the stability of the shoulder joints. [Results] The moving distances in the left, right, and upper directions after the oscillation movement were increased significantly compared with the results before the oscillation movement. [Conclusion] A vibration stimulus is effective as an exercise method to increase the stability of the shoulder joints.

Jung, Da-eun; Moon, Dong-chul

2015-01-01

48

Articular and ligamentous contributions to the stability of the elbow joint  

Microsoft Academic Search

This preliminary study of four elbow specimens inves tigates the relationship of articular geometry and liga mentous structures in providing stability to the elbow joint. A technique is presented that describes the con straining features of varus-valgus and distraction in extension and at 90° of elbow flexion. Valgus stability is equally divided among the medial collateral ligament, anterior capsule, and

Bernard F. Morrey; Kai-Nan An

1983-01-01

49

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

Microsoft Academic Search

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

Deniz Belen; Serkan Simsek; Kazim Yigitkanli; Murad Bavbek

2006-01-01

50

Surgical screw segmentation for mobile C-arm CT devices  

NASA Astrophysics Data System (ADS)

Calcaneal fractures are commonly treated by open reduction and internal fixation. An anatomical reconstruction of involved joints is mandatory to prevent cartilage damage and premature arthritis. In order to avoid intraarticular screw placements, the use of mobile C-arm CT devices is required. However, for analyzing the screw placement in detail, a time-consuming human-computer interaction is necessary to navigate through 3D images and therefore to view a single screw in detail. Established interaction procedures of repeatedly positioning and rotating sectional planes are inconvenient and impede the intraoperative assessment of the screw positioning. To simplify the interaction with 3D images, we propose an automatic screw segmentation that allows for an immediate selection of relevant sectional planes. Our algorithm consists of three major steps. At first, cylindrical characteristics are determined from local gradient structures with the help of RANSAC. In a second step, a DBScan clustering algorithm is applied to group similar cylinder characteristics. Each detected cluster represents a screw, whose determined location is then refined by a cylinder-to-image registration in a third step. Our evaluation with 309 screws in 50 images shows robust and precise results. The algorithm detected 98% (303) of the screws correctly. Thirteen clusters led to falsely identified screws. The mean distance error for the screw tip was 0.8 +/- 0.8 mm and for the screw head 1.2 +/- 1 mm. The mean orientation error was 1.4 +/- 1.2 degrees.

Görres, Joseph; Brehler, Michael; Franke, Jochen; Wolf, Ivo; Vetter, Sven Y.; Grützner, Paul A.; Meinzer, Hans-Peter; Nabers, Diana

2014-03-01

51

Effects of individual strengthening exercises for the stabilization muscles on the nutation torque of the sacroiliac joint in a sedentary worker with nonspecific sacroiliac joint pain  

PubMed Central

[Purpose] We investigated the effects of individual strengthening exercises for the stabilization muscles on the nutation torque of the sacroiliac joint in a sedentary worker with nonspecific sacroiliac joint pain. [Subject] A 36-year-old female complained of pain in the sacroiliac joints. [Methods] The subject performed individual strengthening exercises for the stabilization muscles for nutation torque of the sacroiliac joint for 3 weeks. Pain-provocation tests and visual analog scale (VAS) scores were evaluated before and after the exercises. [Results] After performing the individual strengthening exercises for the erector spinae, rectus abdominis, and biceps femoris muscles for 3 weeks, the subject displayed no pain in the pain provocation tests, and the VAS score was 2/10. [Conclusion] The individual strengthening exercises for the stabilization muscles of the sacroiliac joint performed in the present study appear to be effective for sedentary workers with sacroiliac joint pain.

Yoo, Won-gyu

2015-01-01

52

Stability enhancement by joint phase measurements in a single cold atomic fountain  

E-print Network

We propose a method of joint interrogation in a single atom interferometer which overcomes the dead time between consecutive measurements in standard cold atomic fountains. The joint operation enables for a faster averaging of the Dick effect associated with the local oscillator noise in clocks and with vibration noise in cold atom inertial sensors. Such an operation allows achieving the lowest stability limit due to atom shot noise. We demonstrate a multiple joint operation in which up to five clouds of atoms are interrogated simultaneously in a single setup. The essential feature of multiple joint operation, demonstrated here for a micro-wave Ramsey interrogation, can be generalized to go beyond the current stability limit associated with dead times in present-day cold atom interferometer inertial sensors.

Meunier, M; Geiger, R; Guerlin, C; Alzar, C L Garrido; Landragin, A

2015-01-01

53

Stability enhancement by joint phase measurements in a single cold atomic fountain  

NASA Astrophysics Data System (ADS)

We propose a method of joint interrogation in a single atom interferometer which overcomes the dead time between consecutive measurements in standard cold atomic fountains. The joint operation enables for a faster averaging of the Dick effect associated with the local oscillator noise in clocks and with vibration noise in cold atom inertial sensors. Such an operation allows one to achieve the lowest stability limit due to atom shot noise. We demonstrate a multiple joint operation in which up to five clouds of atoms are interrogated simultaneously in a single setup. The essential feature of multiple joint operation, demonstrated here for a microwave Ramsey interrogation, can be generalized to go beyond the current stability limit associated with dead times in present-day cold atom interferometer inertial sensors.

Meunier, M.; Dutta, I.; Geiger, R.; Guerlin, C.; Garrido Alzar, C. L.; Landragin, A.

2014-12-01

54

The effect of screw fixation type on a modular hemi-pelvic prosthesis: a 3-D finite element model.  

PubMed

In this article, a 3-D finite element (FE) model of human pelvic with a modular hemi-pelvic prosthesis was constructed to study the effect of screw fixation type on the biomechanics of the prosthesis. The results showed that the elimination of the screw far away from the pelvic arcuate line did not induce the instability and stress increase in the prosthesis. On the contrary, some stress in the sustain and acetabular parts decreased by 26.4% and 11.4%, respectively. In conclusion, the optimization of screw fixation can maintain the prosthesis stability and reduced stress concentration on some prosthesis parts. It was deduced that the optimization of the prosthesis could help surgeon reconstruct the pelvic joint function better and diminish the clinical time and cost. PMID:23244444

Hao, Zhixiu; Wan, Chao; Gao, Xiangfei; Ji, Tao; Wang, Haosen

2013-03-01

55

Fatigue Effects on Knee Joint Stability During Two Jump Tasks in Women  

PubMed Central

Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 ± 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury–predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes. PMID:20300024

Ortiz, Alexis; Olson, Sharon L.; Etnyre, Bruce; Trudelle-Jackson, Elaine E.; Bartlett, William; Venegas-Rios, Heidi L.

2010-01-01

56

Fatigue effects on knee joint stability during two jump tasks in women.  

PubMed

Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 +/- 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury-predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes. PMID:20300024

Ortiz, Alexis; Olson, Sharon L; Etnyre, Bruce; Trudelle-Jackson, Elaine E; Bartlett, William; Venegas-Rios, Heidi L

2010-04-01

57

Biodegradable magnesium-based screw clinically equivalent to titanium screw in hallux valgus surgery: short term results of the first prospective, randomized, controlled clinical pilot study  

PubMed Central

Purpose Nondegradable steel-and titanium-based implants are commonly used in orthopedic surgery. Although they provide maximal stability, they are also associated with interference on imaging modalities, may induce stress shielding, and additional explantation procedures may be necessary. Alternatively, degradable polymer implants are mechanically weaker and induce foreign body reactions. Degradable magnesium-based stents are currently being investigated in clinical trials for use in cardiovascular medicine. The magnesium alloy MgYREZr demonstrates good biocompatibility and osteoconductive properties. The aim of this prospective, randomized, clinical pilot trial was to determine if magnesium-based MgYREZr screws are equivalent to standard titanium screws for fixation during chevron osteotomy in patients with a mild hallux valgus. Methods Patients (n=26) were randomly assigned to undergo osteosynthesis using either titanium or degradable magnesium-based implants of the same design. The 6 month follow-up period included clinical, laboratory, and radiographic assessments. Results No significant differences were found in terms of the American Orthopaedic Foot and Ankle Society (AOFAS) score for hallux, visual analog scale for pain assessment, or range of motion (ROM) of the first metatarsophalangeal joint (MTPJ). No foreign body reactions, osteolysis, or systemic inflammatory reactions were detected. The groups were not significantly different in terms of radiographic or laboratory results. Conclusion The radiographic and clinical results of this prospective controlled study demonstrate that degradable magnesium-based screws are equivalent to titanium screws for the treatment of mild hallux valgus deformities. PMID:23819489

2013-01-01

58

Treatment of Pelvic Ring Fractures: Percutaneous Computer Assisted Iliosacral Screwing  

Microsoft Academic Search

This paper describes the development and preliminary testing of an image-guided system for the placement of iliosacral screws\\u000a to stabilize pelvic ring fractures percutaneously, with the aim of decreasing the incidence of surgical complications and\\u000a increasing the accuracy of screw placement. Pre-operative planning of screw trajectories is performed on a 3D model of the\\u000a pelvis constructed from CT scans. During

Lionel Carrat; Jerome Tonetti; Stéphane Lavallée; Philippe Merloz; Laurence Pittet; Jean-paul Chirossel

1998-01-01

59

The synergistic action of the anterior cruciate ligament and thigh muscles in maintaining joint stability  

Microsoft Academic Search

The synergistic action of the ACL and the thigh muscles in maintaining joint stability was studied experimentally. The EMG from the quadriceps and hamstring muscle groups was recorded and analyzed in three separate experimental procedures in which the knee was stressed. The test revealed that direct stress of the ACL has a moderate inhibitory effect on the quadriceps, but simultaneously

M. Solomonow; R. Baratta; B. H. Zhou; H. Shoji; W. Bose; C. Beck; R. DAmbrosia

1987-01-01

60

Determinants of Stability in International Joint Ventures: Evidence from a Developing Country Context  

Microsoft Academic Search

Though the number of international joint ventures (IJVs) from developing countries has grown considerably, little has been reported on their operations and performance. The extant literature is based largely on IJVs from developed countries. To help fill this knowledge gap, this paper examines the determinants of stability from a study of 59 IJVs from developing and developed countries operating in

A. B. Sim; M. Yunus Ali

2000-01-01

61

Screw-locking wrench  

NASA Technical Reports Server (NTRS)

A tool comprises a first handle and a second handle, each handle extending from a gripping end portion to a working end portion, the first handle having first screw threads disposed circumferentially about an inner portion of a first through-hole at the working end portion thereof, the second handle having second screw threads disposed circumferentially about an inner portion of a second through-hole at the working end portion thereof, the first and second respective through-holes being disposed concentrically about a common axis of the working end portions. First and second screw locks preferably are disposed concentrically with the first and second respective through-holes, the first screw lock having a plurality of locking/unlocking screw threads for engaging the first screw threads of the first handle, the second screw lock having a plurality of locking/unlocking screw threads for engaging the second screw threads of the second handle. A locking clutch drive, disposed concentrically with the first and second respective through-holes, engages the first screw lock and the second screw lock. The first handle and the second handle are selectively operable at their gripping end portions by a user using a single hand to activate the first and second screw locks to lock the locking clutch drive for either clockwise rotation about the common axis, or counter-clockwise rotation about the common axis, or to release the locking clutch drive so that the handles can be rotated together about the common axis either the clockwise or counter-clockwise direction without rotation of the locking clutch drive.

Vranish, John M. (Inventor)

2007-01-01

62

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

PubMed Central

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 atlantoaxial instability who were operated using transarticular screws and iliac crest bone graft, without the use of sublaminar wiring (a modification of Magerl's technique). Methods We evaluated retrospectively 38 subjects with atlantoaxial instability who were operated at our institute using transarticular screw fixation. The subjects were followed up for pain, fusion rates, neurological status and radiographic outcomes. Final outcome was graded both subjectively and objectively, using the scoring system given by Grob et al. Results Instability in 34 subjects was secondary to trauma, in 3 due to rheumatoid arthritis and 1 had tuberculosis. Neurological deficit was present in 17 subjects. Most common presenting symptom was neck pain, present in 35 of the 38 subjects. Postoperatively residual neck and occipital pain was present in 8 subjects. Neurological deficit persisted in only 7 subjects. Vertebral artery injury was seen in 3 subjects. None of these subjects had any sign of neurological deficit or vertebral insufficiency. Three cases had nonunion. At the latest follow up, subjectively, 24 subjects had good result, 6 had fair and 8 had bad result. On objective grading, 24 had good result, 11 had fair and 3 had bad result. The mean follow up duration was 41 months. Conclusions Transarticular screw fixation is an excellent technique for fusion of the atlantoaxial complex. It provides highest fusion rates, and is particularly important in subjects at risk for nonunion. Omitting the posterior wiring construct that has been used along with the bone graft in the traditional Magerl' s technique achieves equally good fusion rates and is an important modification, thereby avoiding the complications of sublaminar wire passage. PMID:21092173

2010-01-01

63

Stability and oscillations in a slow-fast flexible joint system with transformation delay  

NASA Astrophysics Data System (ADS)

Flexible joints are usually used to transfer velocities in robot systems and may lead to delays in motion transformation due to joint flexibility. In this paper, a link-rotor structure connected by a flexible joint or shaft is firstly modeled to be a slow-fast delayed system when moment of inertia of the lightweight link is far less than that of the heavy rotor. To analyze the stability and oscillations of the slow-fast system, the geometric singular perturbation method is extended, with both slow and fast manifolds expressed analytically. The stability of the slow manifold is investigated and critical boundaries are obtained to divide the stable and the unstable regions. To study effects of the transformation delay on the stability and oscillations of the link, two quantitatively different driving forces derived from the negative feedback of the link are considered. The results show that one of these two typical driving forces may drive the link to exhibit a stable state and the other kind of driving force may induce a relaxation oscillation for a very small delay. However, the link loses stability and undergoes regular periodic and bursting oscillation when the transformation delay is large. Basically, a very small delay does not affect the stability of the slow manifold but a large delay affects substantially.

Jiang, Shan-Ying; Xu, Jian; Yan, Yao

2014-10-01

64

Strategy for salvage pedicle screw placement: A technical note  

PubMed Central

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.

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

2013-01-01

65

Optimisation of screw compressors  

Microsoft Academic Search

Increasing demands for more efficient screw compressors require that compressor designs are tailored upon their duty, capacity and manufacturing capability. A suitable procedure for optimisation of the screw compressor shape, size, dimension and operating parameters is described here, which results in the most appropriate design for a given compressor application and fluid. It is based on a rack generation algorithm

N. Stosic; I. K. Smith; A. Kovacevic

2003-01-01

66

Multistrand titanium cable for the coracoclavicular stabilization of acute acromioclavicular joint dislocation.  

PubMed

The aim of this retrospective study was to evaluate the outcome of the surgical treatment of acute complete acromioclavicular (AC) joint dislocation with multistrand titanium cable for coracoclavicular (CC) stabilization. Forty-two patients with acute complete AC joint dislocation, Rockwood III, IV, V, were treated with CC stabilization using multistrand titanium cable. Thirty-nine patients could be evaluated after a mean follow-up period of 42 months (range, 34-60). The mean VAS score improved from 5.6 +/- 1.5 to 0.4 +/- 1.2 (p < 0.05). The mean Constant score from 64.8 +/- 8.9 preoperatively to 95.3 +/- 9.3 (p < 0.05). Radiographs showed anatomical reduction in 32 out of 39 patients. Cable breakage occurred in 2 patients. CC stabilization with multistrand titanium cables is an effective and safe alternative to other procedures. This procedure provides immediate joint stabilization and allows early mobilization with satisfying functional recovery. PMID:25090789

Ye, Tianwen; Ouyang, Yueping; Chen, Aimin

2014-06-01

67

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

Microsoft Academic Search

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

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

1998-01-01

68

The Sensorimotor System, Part II: The Role of Proprioception in Motor Control and Functional Joint Stability  

PubMed Central

Objective: To discuss the role of proprioception in motor control and in activation of the dynamic restraints for functional joint stability. Data Sources: Information was drawn from an extensive MEDLINE search of the scientific literature conducted in the areas of proprioception, motor control, neuromuscular control, and mechanisms of functional joint stability for the years 1970–1999. Data Synthesis: Proprioception is conveyed to all levels of the central nervous system. It serves fundamental roles for optimal motor control and sensorimotor control over the dynamic restraints. Conclusions/Applications: Although controversy remains over the precise contributions of specific mechanoreceptors, proprioception as a whole is an essential component to controlling activation of the dynamic restraints and motor control. Enhanced muscle stiffness, of which muscle spindles are a crucial element, is argued to be an important characteristic for dynamic joint stability. Articular mechanoreceptors are attributed instrumental influence over gamma motor neuron activation, and therefore, serve to indirectly influence muscle stiffness. In addition, articular mechanoreceptors appear to influence higher motor center control over the dynamic restraints. Further research conducted in these areas will continue to assist in providing a scientific basis to the selection and development of clinical procedures. PMID:16558671

Riemann, Bryan L.; Lephart, Scott M.

2002-01-01

69

Muscle Co-Contraction Modulates Damping and Joint Stability in a Three-Link Biomechanical Limb  

PubMed Central

Computational models of neuromotor control require forward models of limb movement that can replicate the natural relationships between muscle activation and joint dynamics without the burdens of excessive anatomical detail. We present a model of a three-link biomechanical limb that emphasizes the dynamics of limb movement within a simplified two-dimensional framework. Muscle co-contraction effects were incorporated into the model by flanking each joint with a pair of antagonist muscles that may be activated independently. Muscle co-contraction is known to alter the damping and stiffness of limb joints without altering net joint torque. Idealized muscle actuators were implemented using the Voigt muscle model which incorporates the parallel elasticity of muscle and tendon but omits series elasticity. The natural force-length-velocity relationships of contractile muscle tissue were incorporated into the actuators using ideal mathematical forms. Numerical stability analysis confirmed that co-contraction of these simplified actuators increased damping in the biomechanical limb consistent with observations of human motor control. Dynamic changes in joint stiffness were excluded by the omission of series elasticity. The analysis also revealed the unexpected finding that distinct stable (bistable) equilibrium positions can co-exist under identical levels of muscle co-contraction. We map the conditions under which bistability arises and prove analytically that monostability (equifinality) is guaranteed when the antagonist muscles are identical. Lastly we verify these analytic findings in the full biomechanical limb model. PMID:22275897

Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

2012-01-01

70

EMG recordings of abdominal and back muscles in various standing postures: validation of a biomechanical model on sacroiliac joint stability  

Microsoft Academic Search

In a biomechanical model we described that for stability of the flat sacroiliac joints (SIJ) muscle forces are required which press the sacrum between the two hip bones (self-bracing). Shear loading of these joints is caused by gravity and longitudinally oriented muscles. Protection against shearing can come from transversely oriented muscles like the internal oblique (OI) abdominal muscles. For validation

Chris J Snijders; Margreet T. L. M Ribbers; Hans V de Bakker; Rob Stoeckart; Henk J Stam

1998-01-01

71

Errors in applying the screw deviation method to calculate general motion produced by single degree of freedom mechanisms  

SciTech Connect

The screw deviation method can only be applied to joints whose mechanisms are a single screw, a single revolute, or linear (prismatic) mechanism. In all other situations, the method cannot measure the movements of the mechanism, nor can it represent the motion of the moving segments. Single evolutes and multi-degree of freedom systems cannot be accurately represented by the screw deviation method. The authors conclude that the kinematic mechanism must be known prior to application of the screw deviation method and that application of the method can produce reasonable results only in cases in which the joint mechanism is a screw or a revolute.

Hollerbach, K.; Vorhis, R.L. Van [Lawrence Livermore National Lab., CA (United States); Hollister, A. [Louisiana State Univ., Shreveport, LA (United States). Medical Center

1996-03-01

72

Biomechanical and Histological Evaluation of Roughened Surface Titanium Screws Fabricated by Electron Beam Melting  

PubMed Central

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

Yang, Jun; Cai, Hong; Lv, Jia; Zhang, Ke; Leng, Huijie; Wang, Zhiguo; Liu, Zhongjun

2014-01-01

73

JOINT UNITED STATES/IAEA PROPOSED APPROACH FOR SAFEGUARDS DURING PLUTONIUM STABILIZATION, PACKAGING, AND SHIPMENT  

SciTech Connect

For safety reasons, the U.S. Department of Energy (DOE) is preparing to stabilize and package plutonium oxide currently subject to International Atomic Energy Agency safeguards at the Rocky Flats Environmental Technology Site (RFETS) beginning in the year 2001. The Hanford Site will also stabilize and package plutonium materials under IAEA safeguards. The U.S. and the IAEA began consultations in late 1996 to develop an approach to the application of safeguards during stabilization and packaging. With the plans to ship RFETS plutonium to Savannah River for interim storage prior to final disposition, this work has been extended to include safeguards during shipment. This paper will discuss the elements of a joint U.S./IAEA proposal for this task.

L. KWEI; B. SMITH; ET AL

2001-02-01

74

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

PubMed Central

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

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

2013-01-01

75

Pullout of a lumbar plate with varying screw lengths  

PubMed Central

Background Screw length pertains to stability in various orthopedic fixation devices. There is little or no information on the relationship between plate pullout strength and screw length in anterior lumbar interbody fusion (ALIF) plate constructs in the literature. Such a description may prove useful, especially in the treatment of osteoporotic patients where maximizing construct stability is of utmost importance. Our purpose is to describe the influence of screw length on ALIF plate stability in severely and mildly osteoporotic bone foam models. Methods Testing was performed on polyurethane foam blocks with densities of 0.08 g/cm3 and 0.16 g/cm3. Four-screw, single-level ALIF plate constructs were secured to the polyurethane foam blocks by use of sets of self-tapping cancellous bone screws that were 20, 24, 28, 32, and 36 mm in length and 6.0 mm in diameter. Plates were pulled out at 1 mm/min to failure, as defined by consistently decreasing load despite increasing displacement. Results Pullout loads in 0.08-g/cm3 foam for 20-, 24-, 28-, 32-, and 36-mm screws averaged 303, 388, 479, 586, and 708 N, respectively, increasing at a mean of 25.2 N/mm. In 0.16-g/cm3 foam, pullout loads for 20-, 24-, 28-, 32-, and 36-mm screws averaged 1004, 1335, 1569, 1907, and 2162 N, respectively, increasing at a mean of 72.2 N/mm. Conclusions The use of longer screws in ALIF plate installation is expected to increase construct stability. Stabilization from screw length in osteoporotic patients, however, is limited.

Palmer, Daniel Kyle; Rios, David; Patacxil, Wyzscx Merfil; Williams, Paul A.; Cheng, Wayne K.; ?nceo?lu, Serkan

2012-01-01

76

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

PubMed Central

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

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

2013-01-01

77

Effect of boot shaft stiffness on stability joint energy and muscular co-contraction during walking on uneven surface.  

PubMed

Increased boot shaft stiffness may have a noticeable impact on the range of motion of the ankle joint. Therefore, the ability of the ankle joint to generate power for propulsion might be impaired. This might result in compensatory changes at the knee and hip joint. Besides, adaptability of the subtalar joint to uneven surface might be reduced, which could in turn affect stability. The aim of the study was therefore to investigate the influence of boot shaft stiffness on biomechanical gait parameters. Fifteen healthy young adults walked over coarse gravel wearing two different hiking boots that differed by 50% in passive shaft stiffness. Leg kinematics, kinetics and electromyography were measured. Gait velocity and indicators for stability were not different when walking with the hard and soft boot shaft over the gravel surface. However, the hard boot shaft decreased the ankle range of motion as well as the eccentric energy absorbed at the ankle joint. As a consequence, compensatory changes at the knee joint were observed. Co-contraction was increased, and greater eccentric energy was absorbed. Therefore, the efficiency of gait with hard boots might be decreased and joint loading at the knee might be increased, which might cause early fatigue of knee muscles during walking or hiking. The results of this study suggest that stiffness and blocking of joint motion at the ankle should not be equated with safety. A trade-off between lateral stiffness and free natural motion of the ankle joint complex might be preferable. PMID:20541206

Böhm, Harald; Hösl, Matthias

2010-09-17

78

Posterior Reduction and Temporary Fixation for Odontoid Fracture-a Salvage Maneuver to Anterior Screw Fixation.  

PubMed

Study Design. A prospective study.Objective. To evaluate the outcomes of posterior reduction and temporary fixation using the C1-C2 screw-rod system for odontoid fracture unsuitable for anterior screw fixation.Summary of Background Data. Anterior screw fixation has become the most widely used surgical procedure for the stabilization of odontoid fractures. However, if there is any contraindication for anterior fixation, posterior atlantoaxial fusion is preferred, eliminating the normal rotation of the atlantoaxial complex.Methods. A consecutive series of 22 patients with odontoid fracture unsuitable for anterior screw fixation were involved in this study. Posterior reduction and fixation without fusion using the C1-C2 screw-rod system was performed. Once fracture healing was obtained, instrumentation was removed. The visual analog scale (VAS) of neck pain, neck stiffness, American Spinal Injury Association (ASIA) impairment scale, patient satisfaction, and neck disability index (NDI) were recorded. The range of motion (ROM) of C1-C2 in flexion-extension and rotation was calculated.Results. The average age at internal fixation surgery was 40.2±11.3 years. The mean duration of follow up was 41.8±26.8 months. There were no complications associated with instrumentation. All patients returned to their pre-operative work. Fracture healing was observed in 21 patients and the instrumentation was removed. After removing the instrumentation, the VAS was reduced and neck stiffness were relieved (all P < 0.01). Patient satisfaction and NDI were improved (all P < 0.01). The ROM of C1-C2 was returned to 4.75°±1.62°and 25.70°±5.51°in flexion-extension and in rotation, respectively. No osteoarthritis was observed at the C1-C2 lateral mass joints.Conclusions. Posterior reduction and temporary fixation using the C1-C2 screw-rod system was an optimal salvage maneuver to anterior screw fixation for odontoid fracture. It could effectively avoid the motion loss of C1-C2 caused by posterior atlantoaxial fusion. PMID:25398034

Ni, Bin; Guo, Qunfeng; Lu, Xuhua; Xie, Ning; Wang, Liang; Guo, Xiang; Chen, Fei

2014-11-13

79

Joint time and frequency dissemination network over delay-stabilized fiber optic links  

E-print Network

A precise fiber-based time and frequency dissemination scheme for multiple users with a tree-like branching topology is proposed. Through this scheme, ultra-stable signals can be easily accessed online anywhere along the fiber without affecting other sites. The scheme is tested through an experiment, in which a modulated frequency signal and a synchronized time signal are transferred to multiple remote sites over a delay-stabilized fiber optic links that are over 50 km long. Results show that the relative stabilities are 5E-14@1s and 2E-17@10000s. Meanwhile, compared with each site, time synchronization precision is less than 80 ps. These results can pave the way to practical applications in joint time and frequency dissemination network systems.

Chen, Wei; Cheng, Nan; Xu, Dan; Yang, Fei; Gui, Youzhen; Cai, Haiwen

2015-01-01

80

Helical screw viscometer  

DOEpatents

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.

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

1983-06-30

81

The effect of sagittal alignment on adjacent joint mobility after lumbar instrumentation––a biomechanical study of lumbar vertebrae in a porcine model  

Microsoft Academic Search

Background. The mechanisms and changes in range of motion of neighboring mobile segment (adjacent level) after the instrumented posterior stabilization are not completely understood. This study aims to investigate the effect of sagittal alignment on the adjacent joint mobility after lumbar instrumentation.Methods. Eight fresh porcine lumbar spines were instrumented with pedicle screw implants from L2 to L4. Each specimen was

Wen-Jer Chen; Po-Liang Lai; Ching-Lung Tai; Lih-Huei Chen; Chi-Chien Niu

2004-01-01

82

Blocks and Screws  

NSDL National Science Digital Library

In this lesson, each student is given a block of wood and a screw (or nail), and is asked to put the screw into the block, without any tool (like a screwdriver or hammer). Their efforts, with varying success, lead to a discussion of contrivances, using various items and strategies as make-do (contrived) tools for which they were not intended, and an exploration of many examples of contrivances or adaptive compromises and other imperfections in the living world, especially in humans. This situation may be better explained by evolution rather than the result of intelligent design.

Patterson, Tim

83

Pedicle screw instrumentation of thoracolumbar burst fractures: Biomechanical evaluation of screw configuration with pedicle screws at the level of the fracture  

PubMed Central

Background Posterior fixation alone may not be adequate to achieve and maintain burst fracture reduction. Adding screws in the fractured body may improve construct stiffness. This in vitro study evaluates the biomechanical effect of inserting pedicle screws in the fractured body compared with conventional short- and long-segment posterior fixation. Methods Stable and unstable L2 burst fractures were created in 8 calf spines (aged 18 weeks). Constructs were tested at 8 Nm in the intact state and then with instrumentation consisting of long- and short-segment posterior fixation with and without screws in the fractured L2 vertebral body after (1) stable burst fracture and (2) unstable burst fracture. Range of motion was recorded at L1-3 for flexion-extension, lateral bending, and axial rotation. Statistical analysis was performed with repeated-measures analysis of variance, with significance set at P < .05. The data were normalized to the intact state (100%). Results Both long- and short-segment constructs with screws in the fractured body significantly reduced motion compared with the stable and unstable burst fracture in flexion-extension and lateral bending. Fracture screws enhanced construct stability by 68% (on average) relative to conventional short-segment posterior fixation and were comparable to long-segment posterior fixation. Conclusions Screws at the fracture level improve construct stiffness. Short-segment constructs may suffice for stable burst fractures. More severe injuries may benefit from fracture screws and can be considered as an alternative treatment to long-segment constructs.

Bolesta, Michael J.; Caron, Troy; Chinthakunta, Suresh R.; Vazifeh, Pedram Niknam; Khalil, Saif

2012-01-01

84

Transcutaneous migration of a tibial bioabsorbable interference screw after anterior cruciate ligament reconstruction  

Microsoft Academic Search

We present a case of a poly-L-lactic acid (PLLA) tibial bioabsorbable interference screw disengaging and migrating transcutaneously 12 months after successful anterior cruciate ligament reconstruction with quadrupled hamstrings autograft. No graft insufficiency or joint inflammatory reaction was present. The screw was removed surgically with no evidence of resorption. The graft was well incorporated into the tibial tunnel. The patient recovered

Greg Sassmannshausen; Charles F Carr

2003-01-01

85

Biomechanical Behaviour of Double Threaded Screw in Tibia Fixation  

Microsoft Academic Search

The aim of the work was assessment of stability of tibia fixation realized with the use of double threaded screw. Biomechanical\\u000a analysis of the tibia – double threaded screw system was carried our for the implant made of two biomaterials used in bone\\u000a surgery – Cr-Ni-Mo stainless steel and Ti-6Al-4V alloy. Finite element method was applied to calculate displacements, strains

Witold Walke; Jan Marciniak; Zbigniew Paszenda; Marcin Kaczmarek; Jerzy Cieplak

2008-01-01

86

Tapered orthodontic miniscrews induce bone - screw cohesion following immediate loading  

Microsoft Academic Search

SUMMARY The aim of this study was to investigate the initial stability of tapered orthodontic miniscrews (T-type screws) after placement, the necessity of a healing period, and the propriety of immediate loading. Twenty male Wistar rats with a mean age of 20 weeks were divided into two groups. In the immediate- loading groups, straight orthodontic miniscrews (S-type screws) and T-type

Shinya Yano; Mituru Motoyoshi; Miwa Uemura; Akiko Ono; Noriyoshi Shimizu

2006-01-01

87

Effects of muscular activation patterns on the ankle joint stabilization: An investigation under different Degrees of Freedom.  

PubMed

Altered biomechanical demands of a stabilization task lead to specific changes in coordination patterns among the involved muscles. The objective of this work was to investigate the effects of increased Degrees of Freedom (DoF) of an external object on the stabilization process of the ankle joint in a voluntary force production task. Four muscles (vastus medialis, VM; tibialis anterior, TA; peroneus longus, PL; gastrocnemius medialis, GM) were recorded using surface electromyography and synchronized to dynamometric data. The subject's task was to exert force against the external object by performing a knee extension under 0, 1 or 3 DoF. Forces were measured using three dimensional force transducers and temporal coordination was assessed using the cross-correlation function (CCF). While the force decreased with increasing DoF the muscles showed a selective gain scaling in order to stabilize the ankle joint. Muscles fulfilling mainly stabilizing functions (TA and PL) tended to increase their activities, while the muscles with motor functions either decreased (GM) or increased (VM). The CCF revealed different intermuscular coordination strategies depending on the environmental condition, showing an advanced phasing in the ankle stabilizing PL in unstable environmental conditions (3 DoF). Nevertheless, the overall sequence of muscle activation was preserved. It is concluded that the process of joint stabilization is controlled in dependency of the status of the external system. The associated neuromuscular system adjustments underline the role of movement coordination in the stabilization process. PMID:21050773

Wuebbenhorst, Kati; Zschorlich, Volker

2011-04-01

88

Dynamic Stability of a Rotating Shaft Driven Through a Universal Joint  

NASA Astrophysics Data System (ADS)

The dynamic stability of a system composed of driving and driven shafts connected by a universal joint is investigated. Due to the characteristics of the joint, even if the driving shaft experiences constant torque and rotational speed, the driven shaft experiences fluctuating rotational speed, bending moments and torque. These are sources of potential parametric, forced and flutter type instabilities. The focus of this work is on the lateral instabilities of the driven shaft. Two distinct models are developed, namely, a rigid body model (linear and non-linear) and a flexible model (linear). The driven shaft is taken to be pinned at the joint end and to be resting on a compliant damped bearing at the other end. Both models lead to sets of differential equations with time dependent coefficients. For both rigid (linear and non-linear) and flexible models, flutter instabilities were found but occurred outside the practical range of operation (rotational speed and torque) for lightly damped systems. Parametric instability charts were obtained by using the monodromy matrix technique for both rigid and flexible linear models. The transmitted bending moments were found to cause strong parametric instabilities in the system. By comparing the results from the two linear models, it is shown that the inclusion of flexibility leads to new zones of instability, not predicted by previous models. These zones, depending on the physical parameters of the system, can occur for practical conditions of operation. Using direct numerical integration for a few sets of specific parameter values, forced resonances were found when the rotational speed reached a value equal to a natural frequency of the system divided by two.

Mazzei, A. J., Jr.; Argento, A.; Scott, R. A.

1999-04-01

89

Use of specialized bone screws for intermaxillary fixation.  

PubMed

Fixation of the injured mandible to the maxilla is a proven method of stabilizing mandibular fractures and ensuring proper occlusion. The authors report their results with new specialized intraoral bone screws (IMF Screw System; Howmedica Leibinger, Inc., Carrollton, TX) that are designed for the purpose of achieving intermaxillary fixation (IMF). Nineteen patients were placed into rigid IMF using IMF screws alone. Indications were nondisplaced mandibular fractures; symphyseal, body, and angle fractures; midfacial fractures requiring temporary IMF; and edentulous patients with any of these fracture types and an adequate prosthesis. All procedures were performed with the patient under general anesthesia. The authors found that the operative time was markedly shorter than with standard IMF techniques, patient satisfaction was high, and there were no infections related to the screws. All 19 patients remained in stable, accurate occlusion and had adequate healing. One patient continues to have paraesthesias in the mental nerve distribution after screw removal. Although there is the potential for tooth and nerve injury when screws are placed improperly, the IMF Screw System seems to be a safe and reliable method of achieving secure mandibular fixation. PMID:10696041

Schneider, A M; David, L R; DeFranzo, A J; Marks, M W; Molnar, J A; Argenta, L C

2000-02-01

90

The Screw-worm.  

E-print Network

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...

Francis, M. (Mark)

1890-01-01

91

Effect of filler metal composition on the strength of yttria stabilized zirconia joints brazed with Pd-Ag-CuOx  

SciTech Connect

The Ag-CuOx system is of interest to be used to be used as an air braze filler metal for joining high temperature electrochemical devices. Previous work has shown that the melting temperatures can be increased by adding palladium to Ag-CuOx and it is expected that this may aid high temperature stability. This work compares the room temperature bend strength of joints made between yttria-stabilized zirconia (YSZ) air brazed using Ag-CuOx without palladium and with 5 and 15mol% palladium additions. It has been found that in general palladium decreases joint strength, especially in low copper oxide compositions filler metals. At high copper oxide contents, brittle fracture through both copper oxide rich phases and the YSZ limits joint strength.

Darsell, Jens T.; Weil, K. Scott

2008-09-08

92

Abstract--The anterior cruciate ligament (ACL) functions as a mechanical stabilizer in the tibiofemoral joint. Over  

E-print Network

Abstract-- The anterior cruciate ligament (ACL) functions as a mechanical stabilizer in the tibiofemoral joint. Over 250,000 Americans each year suffer from ACL ruptures and tears, making the ACL due to the small length scale (ACL insertions. This study utilizes ultrasound

Konofagou, Elisa E.

93

Abstract--The anterior cruciate ligament (ACL) functions as a mechanical stabilizer in the tibiofemoral joint. Over  

E-print Network

Abstract-- The anterior cruciate ligament (ACL) functions as a mechanical stabilizer in the tibiofemoral joint. Over 250,000 Americans each year suffer ACL ruptures and tears, making the ACL the most commonly injured knee ligament. Methods which permit the in situ monitoring of changes in ACL graft

Konofagou, Elisa E.

94

Reconstruction of lateral knee joint stability following resection of proximal fibula tumors  

PubMed Central

Managing tumors of the proximal fibula may require en bloc resection of the fibular head with the attachment site of the lateral collateral ligament (LCL) and biceps femoris tendon. The aim of the present study was to evaluate knee stability and the Musculoskeletal Tumor Society (MSTS) functional score of patients with proximal fibula tumors. Twenty-nine patients with proximal fibula tumors were retrospectively reviewed (18 patients in the reconstruction group and 11 patients in the non-reconstruction group). A comparative analysis was conducted of knee stability (measuring the degree of lateral joint space opening using varus stress radiographs with a 30º knee flexion) and MSTS functional score between the two groups. The mean follow-up period was 42.8±20.9 months (range 24–117) and 40.8±26.0 months (range 24–117) for the reconstruction and the non-reconstruction groups, respectively. Fifteen patients (83.3%) in the reconstruction group had a stable knee, one (5.6%) had grade 1 instability and two (11.1%) had grade 2 instability. Four patients (36.4%) in the non-reconstruction group had a stable knee, three (27.3%) had grade 1 instability, one (9.1%) had grade 2 instability and three (27.3%) had grade 3 instability. Patients who underwent reconstructive surgery exhibited a higher rate of knee stability compared with those in the non-reconstruction group (P<0.05). The MSTS function scores were 93% (range, 93–100%) for the reconstruction group and 87% (range, 60–100%) for the non-reconstruction group (P<0.05). Reconstruction of the LCL and biceps femoris tendon to the lateral tibial metaphysis with a suture anchor was a safe, reliable and simple technique following resection of proximal fibula tumors. PMID:24396415

ZHAO, SHI-CHANG; ZHANG, CHANG-QING; ZHANG, CHUN-LIN

2014-01-01

95

Dynamic stability analysis of torsional vibrations of a shaft system connected by a Hooke's joint through a continuous system model  

NASA Astrophysics Data System (ADS)

Stability of parametrically excited torsional vibrations of a shaft system composed of two torsionally elastic shafts interconnected through a Hooke's joint is studied. The shafts are considered to be continuous (distributed-parameter) systems and an approximate discrete model for the torsional vibrations of the shaft system is derived via a finite element scheme. The stability of the solutions of the linearized equations of motion, consisting of a set of Mathieu-Hill type equations, is examined by means of a monodromy matrix method and the results are presented in the form of a Strutt-Ince diagram visualizing the effects of the system parameters on the stability of the shaft system.

Bulut, Gökhan

2014-08-01

96

Joint Adaptive Mean-Variance Regularization and Variance Stabilization of High Dimensional Data  

PubMed Central

The paper addresses a common problem in the analysis of high-dimensional high-throughput “omics” data, which is parameter estimation across multiple variables in a set of data where the number of variables is much larger than the sample size. Among the problems posed by this type of data are that variable-specific estimators of variances are not reliable and variable-wise tests statistics have low power, both due to a lack of degrees of freedom. In addition, it has been observed in this type of data that the variance increases as a function of the mean. We introduce a non-parametric adaptive regularization procedure that is innovative in that : (i) it employs a novel “similarity statistic”-based clustering technique to generate local-pooled or regularized shrinkage estimators of population parameters, (ii) the regularization is done jointly on population moments, benefiting from C. Stein's result on inadmissibility, which implies that usual sample variance estimator is improved by a shrinkage estimator using information contained in the sample mean. From these joint regularized shrinkage estimators, we derived regularized t-like statistics and show in simulation studies that they offer more statistical power in hypothesis testing than their standard sample counterparts, or regular common value-shrinkage estimators, or when the information contained in the sample mean is simply ignored. Finally, we show that these estimators feature interesting properties of variance stabilization and normalization that can be used for preprocessing high-dimensional multivariate data. The method is available as an R package, called ‘MVR’ (‘Mean-Variance Regularization’), downloadable from the CRAN website. PMID:22711950

Dazard, Jean-Eudes; Rao, J. Sunil

2012-01-01

97

Screw Dislocations in Light Wavefronts  

Microsoft Academic Search

We discuss screw dislocations of a phase surface as the one type of wavefront of a monochromatic wave. The simple method for construction of the optical wavefronts with an isolated screw dislocation is reported. Laser beams with the dislocations of different orders were experimentally achieved by using diffraction on computer-synthesized gratings.

V. Yu. Bazhenov; M. S. Soskin; M. V. Vasnetsov

1992-01-01

98

Optimization Of Screw Compressor Design  

Microsoft Academic Search

Ever increasing demands for efficient screw compressors require that compressor designs are tailored upon their duty, capacity and manufacturing capability. A suitable procedure for optimisation of screw compressor shape, dimension and operating parameters is described here, which results in the most appropriate design for a given compressor duty. It is based on a rack generation algorithm for rotor profile combined

N. Stosic; Ian K Smith; A. Kovacevic

2002-01-01

99

Modified Posterior Approach to Total Hip Arthroplasty to Enhance Joint Stability  

PubMed Central

We modified the posterior approach by preserving the external rotator muscles to enhance joint stability after primary THA. We asked whether this modified posterior approach would have a lower dislocation rate than the conventional posterior approach, with and without a repair of external rotator muscles. We retrospectively divided 557 patients (670 hips) who had undergone primary THA into three groups based on how the external rotator muscles had been treated during surgery: (1) not repaired after sectioning, (2) repaired after sectioning, or (3) not sectioned and preserved. The minimum followup was 1 year. In the group with preserved external rotator muscles, we observed no dislocations; in comparison, the dislocation rates for the repaired rotator group and the no-repair group were 3.9% and 5.3%, respectively. This modified posterior approach, which preserves the short external rotator muscles, seemed effective in preventing early dislocation after primary THA. Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18196409

Kwon, Soon Yong; Sun, Doo Hoon; Han, Suk Ku; Maloney, William J.

2008-01-01

100

[Can steel screws be combined with titanium plates? Hard polishing technique and SEM in animal experiments].  

PubMed

To clarify the compatibility of steel and titanium, mandibular resections were performed on 24 sheep and the defects bridged with titanium plates and steel vs. titanium screws. 6, 12 and 24 weeks after osteosynthesis the implants were removed along with the surrounding bone segment and thin ground sections were prepared using the Donath method. The sections were then studied by light, fluorescence, polarization and scanning electron microscopy. The stability and easy removal are advantages of steel screws rendering them particularly suitable for temporary implantations. Moreover, they are 50-75% less expensive than titanium screws. After 3 and 6 months some minimum friction corrosion was observed at the screw/plate interface of steel screws. None of the specimens, however, showed signs of local tissue damage such as metallosis. From this it may be concluded that at least on a temporary basis a combination of steel screws and titanium plantes seems to be possible. PMID:1816958

Wächter, R; Stoll, P

1991-01-01

101

Influence of Thickness and Contact Surface Geometry of Condylar Stem of TMJ Implant on Its Stability  

NASA Astrophysics Data System (ADS)

The aim of this study is to examine the effect thickness and contact surface geometry of condylar stem of TMJ implant on its stability in total reconstruction system and evaluate the micro strain resulted in bone at fixation screw holes in jaw bone embedded with eight different designs of temporomandibular joint implants. A three dimensional model of a lower mandible of an adult were developed from a Computed Tomography scan images. Eight different TMJ implant designs and fixation screws were modeled. Three dimensional finite element models of eight implanted mandibles were analyzed. The forces assigned to the masticatory muscles for incisal clenching were applied consisting of nine important muscular loads. In chosen loading condition, The results indicated that the anatomical curvature contact surface design of TMJ implant can moderately improve the stability and the strain resulted in fixation screw holes in thinner TMJ implant was diminished in comparison with other thicknesses.

Arabshahi, Zohreh; Kashani, Jamal; Kadir, Mohammed Rafiq Abdul; Azari, Abbas

102

Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study  

PubMed Central

Background Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces. A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied. Methods The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed. Results The mean loads to failure for each group were 295,44 N (Group 1; 9 × 23 screw), 564,05 N (Group 2; 9 × 28), 614,95 N (Group 3; 9 × 35), 651,14 N (Group 4; 10 × 28) and 664,99 (Group 5; 10 × 35). No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P < 0.001). Conclusions Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm) do not achieve optimal fixation and should be implanted only with special requirements. PMID:20591177

2010-01-01

103

Estimation of Complex Anatomical Joint Motions Using a Spatial Goniometer  

E-print Network

of human joints has numerous applications. The screw axis can be determined using optical motion capture of the instantaneous screw axis in human anatomical joints from the data given by a spatial mechanical goniometer. 1 systems with cameras and optical markers, or medical imaging modalities to mea- sure the movement of bones

Hayward, Vincent

104

[Computerized tomography monitoring of the position of pedicle screws in scoliosis surgery].  

PubMed

With the increasing use of pedicle screws in instrumented spine surgery the neurological risk must be evaluated critically. Studies, which evaluated the accuracy of pedicle screw placement in scoliosis surgery, have not been published up to date to our knowledge. In 25 consecutive patients with idiopathic scoliosis, who underwent posterior instrumented curve correction and stabilization, the accuracy of pedicle screw placement was evaluated using axial computed tomography. There was a total of 178 screws between T5 and L4. The preoperative Cobb angle of the curve averaged 60.7 degrees, the mean rotation of the instrumented vertebrae was 19.1 degrees according to Perdriolle. 145 pedicle screws (81.5%) were placed correctly within the pedicles, of which 4 screws (4.5%) penetrated the anterior aspect of the vertebral body with a mean of 0.9 mm. 22 screws (12.4%) showed lateral penetration of the pedicle with a mean of 1.9 mm, of which one screw was placed completely lateral of the pedicle. 8 screws (4.5%) penetrated the medial wall of the pedicle by 1.3 mm on average. One screw each penetrated the cranial and caudal border of the pedicle. Statistical analysis did not reveal any significant relationships between pedicle screw misplacement and grade of vertebral rotation or site of instrumentation. Neurological complications were not noted in any of the cases. In our mind the risk of pedicle screw threaded curve correction and fusion in scoliosis surgery in the hands of an experienced spine surgeon is calculated acceptably low. PMID:9027118

Halm, H; Liljeqvist, U; Link, T; Jerosch, J; Winkelmann, W

1996-01-01

105

[The biomechanics of screws, cerclage wire and cerclage cable].  

PubMed

In contrast to fracture fixation, when performing an osteotomy the surgeon is able to plan preoperatively. The resulting fixation and compression of the bone fragments are the most important points. A stable osteosynthesis should prevent dislocation of bone fragments and improve bone healing. Beside plates, cerclages can be used for tension band or diaphysis bone fixation. Moreover, cortical or cancellous screws can be used for osteotomy fixation. This work describes biomechanical principles for fixation after an osteotomy with cerclages and cortical or cancellous screws. It also summarizes the materials and geometries used, as well as their influence on the stability of the osteosynthesis. PMID:23615626

Schröder, C; Woiczinski, M; Utzschneider, S; Kraxenberger, M; Weber, P; Jansson, V

2013-05-01

106

Sterile Pretibial Abscess After Anterior Cruciate Reconstruction From Bioabsorbable Interference Screws: A Report of 2 Cases  

Microsoft Academic Search

We report 2 cases of extra-articular pretibial sterile abscesses with minimal osteolysis after anterior cruciate ligament reconstruction with poly-L-lactic acid bioabsorbable interference screw fixation. No joint involvement was evident in either case. Both patients underwent surgical exploration for incision, drainage, and excision with debridement of the biodegradable screw debris from the tibial bone tunnel. The cystic area in case 1

Benjamin T. Busfield; Lesley J. Anderson

2007-01-01

107

Screw behavior in large diameter slewing bearing assemblies: numerical and experimental analyses  

Microsoft Academic Search

This paper investigates the behavior of large diameter bearing bolted joint in order to evaluate fatigue resistance of the\\u000a screws. Based on experimental results, a sector of a slewing bearing is modeled using 3D finite elements. The model is built\\u000a via hypothesis of sine-distributed efforts on the roller tracks. The simulations are carried out for the most loaded screw,\\u000a which

Zouhair Chaib; Alain Daidié; Dimitri Leray

2007-01-01

108

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

PubMed

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

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

2013-07-01

109

Cortical screws used to rescue failed lumbar pedicle screw construct: a biomechanical analysis.  

PubMed

OBJECT Cortical trajectory screw constructs, developed as an alternative to pedicle screw fixation for the lumbar spine, have similar in vitro biomechanics. The possibility of one screw path having the ability to rescue the other in a revision scenario holds promise but has not been evaluated. The objective in this study was to investigate the biomechanical properties of traditional pedicle screws and cortical trajectory screws when each was used to rescue the other in the setting of revision. METHODS Ten fresh-frozen human lumbar spines were instrumented at L3-4, 5 with cortical trajectory screws and 5 with pedicle screws. Construct stiffness was recorded in flexion/extension, lateral bending, and axial rotation. The L-3 screw pullout strength was tested to failure for each specimen and salvaged with screws of the opposite trajectory. Mechanical stiffness was again recorded. The hybrid rescue trajectory screws at L-3 were then tested to failure. RESULTS Cortical screws, when used in a rescue construct, provided stiffness in flexion/extension and axial rotation similar to that provided by the initial pedicle screw construct prior to failure. The rescue pedicle screws provided stiffness similar to that provided by the primary cortical screw construct in flexion/extension, lateral bending, and axial rotation. In pullout testing, cortical rescue screws retained 60% of the original pedicle screw pullout strength, whereas pedicle rescue screws retained 65% of the original cortical screw pullout strength. CONCLUSIONS Cortical trajectory screws, previously studied as a primary mode of fixation, may also be used as a rescue option in the setting of a failed or compromised pedicle screw construct in the lumbar spine. Likewise, a standard pedicle screw construct may rescue a compromised cortical screw track. Cortical and pedicle screws each retain adequate construct stiffness and pullout strength when used for revision at the same level. PMID:25478820

Calvert, Graham C; Lawrence, Brandon D; Abtahi, Amir M; Bachus, Kent N; Brodke, Darrel S

2015-02-01

110

A cementless, elastic press-fit socket with and without screws  

PubMed Central

Background The acetabular component has remained the weakest link in hip arthroplasty regarding achievement of long-term survival. Primary fixation is a prerequisite for long-term performance. For this reason, we investigated the stability of a unique cementless titanium-coated elastic monoblock socket and the influence of supplementary screw fixation. Patient and methods During 2006–2008, we performed a randomized controlled trial on 37 patients (mean age 63 years (SD 7), 22 females) in whom we implanted a cementless press-fit socket. The socket was implanted with additional screw fixation (group A, n = 19) and without additional screw fixation (group B, n = 18). Using radiostereometric analysis with a 2-year follow-up, we determined the stability of the socket. Clinically relevant migration was defined as > 1 mm translation and > 2º rotation. Clinical scores were determined. Results The sockets without screw fixation showed a statistically significantly higher proximal translation compared to the socket with additional screw fixation. However, this higher migration was below the clinically relevant threshold. The numbers of migratory sockets were not significantly different between groups. After the 2-year follow-up, there were no clinically relevant differences between groups A and B regarding the clinical scores. 1 patient dropped out of the study. In the others, no sockets were revised. Interpretation We found that additional screw fixation is not necessary to achieve stability of the cementless press-fit elastic RM socket. We saw no postoperative benefit or clinical effect of additional screw fixation. PMID:23083434

2012-01-01

111

Biomechanical impact of C2 pedicle screw length in an atlantoaxial fusion construct  

PubMed Central

Background: Posterior, atlantoaxial (AA) fusions of the cervical spine may include either standard (26 mm) or short (16 mm) C2 pedicle screws. This manuscript focused on an in vitro biomechanical comparison of standard versus short C2 pedicle screws to perform posterior C1-C2 AA fusions. Methods: Twelve human cadaveric spines underwent C1 lateral mass screw and standard C2 pedicle screw (n = 6) versus short C2 pedicle screw (n = 6) fixation. Six additional controls were not instrumented. The peak torque, peak rotational interval, and peak stiffness of the constructs were analyzed to failure levels. Results: The peak torque to construct failure was not statistically significantly different among the control spine (12.2 Nm), short pedicle fixation (15.5 Nm), or the standard pedicle fixation (11.6 Nm), P = 0.79. While the angle at the peak rotation statistically significantly differed between the control specimens (47.7° of relative motion) and the overall instrumented specimens (P < 0.001), the 20.7° of relative rotation in the short C2 pedicle screw specimens was not statistically significantly higher than the 13.7° of relative rotation in the standard C2 pedicle screw specimens (P = 0.39). Similarly, although the average stiffness was statistically significantly lower in control group (0.026 Nm/degree) versus the overall instrumented specimens (P = 0.001), the standard C2 pedicle screws (2.54 Nm/degree) did not differ from the short C2 pedicle screws Conclusions: Both standard and short C2 pedicle screws allow for equally rigid fixation of C1 lateral mass-C2 AA fusions. Usage of a short C2 pedicle screw may be an acceptable method of stabilization in carefully selected patient populations. PMID:25289157

Xu, Risheng; Bydon, Mohamad; Macki, Mohamad; Belkoff, Stephen M.; Langdale, Evan R.; McGovern, Kelly; Wolinsky, Jean-Paul; Gokalsan, Ziya L.; Bydon, Ali

2014-01-01

112

Free-hand placement of iliac screws for spinopelvic fixation based on anatomical landmarks: technical note  

PubMed Central

Background The placement of iliac screws is a biomechanically sound method for the stabilization of long multi-segment lumbar constructs. Traditional techniques for the placement of iliac screws often involve either substantial iliac muscle dissection for visualization of screw trajectory based on bony landmarks, or alternatively the use of intra-operative imaging to visualize these landmarks and guide screw placement. We describe an alternative free-hand method of iliac screw placement, one that needs neither significant muscle dissection nor intra-operative imaging. Methods We performed this technique in 10 consecutive patients. Patient demographics, spinal pathology, post-operative complications, and screw hardware characteristics are described. Results We have successfully used this technique for the placement 20 iliac screws based on anatomic landmarks in 10 consecutive patients. There were no cortical breeches of the ileum and no penetrations into the acetabulum on post-operative imaging. There were no instances of hardware failure. Two patients developed deep vein thromboses after surgery, 1 had a pulmonary embolism. Conclusions Based on our limited experience to date, free-hand placement of iliac screws is both easy to perform and safe for the patient. Further study and validation using this technique is warranted. PMID:25694933

Fridley, Jared; Fahim, Daniel; Navarro, Jovany; Wolinsky, JP

2014-01-01

113

Examining executive function in the second year of life: Coherence, stability, and relations to joint attention and language.  

PubMed

Several theories of executive function (EF) propose that EF development corresponds to children's ability to form representations and reflect on represented stimuli in the environment. However, research on early EF is primarily conducted with preschoolers, despite the fact that important developments in representation (e.g., language, gesture, shared joint attention) occur within the 1st years of life. In the present study, EF performance and the relationship between EF and early representation (i.e., joint attention, language) were longitudinally examined in 47 children at 14 and 18 months of age. Results suggest that the 2nd year of life is a distinct period of EF development in which children exhibit very little coherence or stability across a battery of EF tasks. However, by 18 months, a subset of child participants consistently passed the majority of EF tasks, and superior EF performance was predicted by 14-month representational abilities (i.e., language comprehension and some episodes of initiating joint attention). This research suggests that the transition from foundational behavioral control in infancy to the more complex EF observed in preschool is supported by representational abilities in the 2nd year of life. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:25546598

Miller, Stephanie E; Marcovitch, Stuart

2015-01-01

114

An Articulating Tool for Endoscopic Screw Delivery  

E-print Network

This paper describes the development of an articulating endoscopic screw driver that can be used to place screws in osteosynthetic plates during thoracoscopic surgery. The device is small enough to be used with a 12 mm ...

Petrzelka, Joseph Edward

115

Precision Stabilization Simulation of a Ball Joint Gimbaled Mirror Using Advanced MATLAB  

E-print Network

to provide precise line of sight stabilization for the seeker (mirror). The mirror is attached to four Kevlar or unwind to change the length of each Kevlar line to position the mirror appropriately. The ball is mounted to a support structure, made up of a fixed body. To maintain stability and position of the seeker, the Kevlar

Hernandez, Orlando

116

Preventing loosening of implant abutment screws.  

PubMed

A procedure for using dimples inside the abutment screw cylinder above the screws and filling the holes with elastomeric impression material will prevent the screw-retained prosthesis from loosening. A modification of the procedure can also be used for angled abutments. PMID:8709025

Cavazos, E; Bell, F A

1996-05-01

117

Preventing loosening of implant abutment screws  

Microsoft Academic Search

A procedure for using dimples inside the abutment screw cylinder above the screws and filling the holes with elastomeric impression material will prevent the screw-retained prosthesis from loosening. A modification of the procedure can also be used for angled abutments.

Edmund Cavazos; Fred A Bell

1996-01-01

118

Influence of abutment screw design and surface coating on the bending flexural strength of the implant set.  

PubMed

The purpose of this study was to analyze the influence of the setting and the presence of solid lubricant on the abutment screw surface on the flexural strength of the joint implant/abutment/screw. Forty abutments were connected to external hex implants, divided into 4 groups (n = 10): FE (titanium alloy screw threaded in the extremity), LE (titanium alloy screw with solid lubricant and thread in the extremity), FT (titanium alloy screw with threaded in all its length), and LT (titanium alloy screw with solid lubricant and thread in all its length). Through the mechanical flexural test, the implant/abutment resistance was evaluated with load applied perpendicular to the long axis in a mechanical testing machine (EMIC) under a speed of 0.5 mm/min. Data were submitted to a statistics test, and results showed statistically significant differences between the FE group and the other groups, and the FE group showed the lowest values. The LE group showed greater values than the LT group, and the values were statistically significant. According to the methodology used, it can be concluded that within noncoated titanium screws, a screw threaded along its entire length provided greater rigidity to the implant set, while with the screw containing solid lubricant, the screw threaded in all its length provided less rigidity of the implant set than screws with the thread only on the end. Among screws with the same geometry, those with the solid lubricant are statistically higher than those which do not have threads just at the end, but those with threads along their entire length do not show statistically significant differences. PMID:22251283

Prado, Célio Jesus do; Neves, Flávio Domingues das; Soares, Carlos José; Dantas, Kelly Abadia; Dantas, Talita Souza; Naves, Lucas Zago

2014-04-01

119

Biomechanical comparison of inside–outside screws, cables, and regular screws, using a sawbone model  

Microsoft Academic Search

Our aim was to conduct a biomechanical comparison of the pull-out strengths of inside–outside (I\\/O) screws, cables, and bone screws to determine whether I\\/O screws provide greater pull-out resistance than cables or bone screws, and their effectiveness with the screw diameter. There is no remarkable biomechanical experimental study comparing the I\\/O technique with conventional spinal techniques. The diameter of the

Yusuf Sukru Caglar; Fuat Torun; Thomas Glenn Pait; William Hogue; Melih Bozkurt; Serdar Özgen

2005-01-01

120

Restoration of horizontal stability in complete acromioclavicular joint separations: surgical technique and preliminary results  

PubMed Central

Background Our purpose was to investigate the clinical efficacy of arthroscope-assisted acromioclavicular ligament reconstruction in combination with double endobutton coracoclavicular ligament reconstruction for the treatment of complete acromioclavicular joint dislocation. Methods During the period from February 2010 to October 2012, ten patients with Rockwood types IV and V acromioclavicular joint dislocation were hospitalized and nine were treated with acromioclavicular ligament reconstruction combined with double endobutton of coracoclavicular ligament reconstruction. The improvement in shoulder functions was assessed using a Constant score and visual analog scale (VAS) system. Results The mean follow-up period was 33.6?±?5.4 months. The mean Constant scores improved from 25.2?±?6.6 preoperatively to 92.4?±?6.5 postoperatively, while the mean VAS score decreased from 5.9?±?1.4 to 1.2?±?0.9; significant differences were observed. The final follow-up revealed that excellent outcomes were achieved in eight patients and good outcome in two patients. Conclusion Arthroscope-assisted acromioclavicular ligament reconstruction in combination with double endobutton of coracoclavicular ligament reconstruction is an effective approach for treatment of acute complete acromioclavicular joint dislocation. PMID:24225119

2013-01-01

121

A screw propelling capsule robot  

Microsoft Academic Search

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

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

2011-01-01

122

Slope Stability Problems and Back Analysis in Heavily Jointed Rock Mass: A Case Study from Manisa, Turkey  

NASA Astrophysics Data System (ADS)

This paper presents a case study regarding slope stability problems and the remedial slope stabilization work executed during the construction of two reinforced concrete water storage tanks on a steep hill in Manisa, Turkey. Water storage tanks of different capacities were planned to be constructed, one under the other, on closely jointed and deformed shale and sandstone units. The tank on the upper elevation was constructed first and an approximately 20-m cut slope with two benches was excavated in front of this upper tank before the construction of the lower tank. The cut slope failed after a week and the failure threatened the stability of the upper water tank. In addition to re-sloping, a 15.6-m deep contiguous retaining pile wall without anchoring was built to support both the cut slope and the upper tank. Despite the construction of a retaining pile wall, a maximum of 10 mm of displacement was observed by inclinometer measurements due to the re-failure of the slope on the existing slip surface. Permanent stability was achieved after the placement of a granular fill buttress on the slope. Back analysis based on the non-linear (Hoek-Brown) failure criterion indicated that the geological strength index (GSI) value of the slope-forming material is around 21 and is compatible with the in situ-determined GSI value (24). The calculated normal-shear stress plots are also consistent with the Hoek-Brown failure envelope of the rock mass, indicating that the location of the sliding surface, GSI value estimated by back analysis, and the rock mass parameters are well defined. The long-term stability analysis illustrates a safe slope design after the placement of a permanent toe buttress.

Akin, Mutluhan

2013-03-01

123

Arthroscopic treatment of slipped capital femoral epiphysis screw impingement and concomitant hip pathology.  

PubMed

Impingement caused by screws used for stabilization of slipped capital femoral epiphysis can be treated arthroscopically. Although troublesome screws have traditionally been removed by open techniques, arthroscopic removal can successfully be achieved. In addition to affording the patient the benefits of minimally invasive surgery, surgeons also have the ability to arthroscopically address any concomitant hip pathology responsible for pain, including femoroacetabular impingement and labral tears. PMID:25264513

Howse, Elizabeth A; Wooster, Benjamin M; Mannava, Sandeep; Perry, Brad; Stubbs, Allston J

2014-08-01

124

Arthroscopic Treatment of Slipped Capital Femoral Epiphysis Screw Impingement and Concomitant Hip Pathology  

PubMed Central

Impingement caused by screws used for stabilization of slipped capital femoral epiphysis can be treated arthroscopically. Although troublesome screws have traditionally been removed by open techniques, arthroscopic removal can successfully be achieved. In addition to affording the patient the benefits of minimally invasive surgery, surgeons also have the ability to arthroscopically address any concomitant hip pathology responsible for pain, including femoroacetabular impingement and labral tears. PMID:25264513

Howse, Elizabeth A.; Wooster, Benjamin M.; Mannava, Sandeep; Perry, Brad; Stubbs, Allston J.

2014-01-01

125

Surgical treatment of Rockwood grade-V acromioclavicular joint dislocations  

PubMed Central

Background and purpose Long-term outcome after surgery for grade-V acromioclavicular joint dislocation has not been reported. We performed a retrospective analysis of functional and radiographic outcome 15–22 years after surgery. Patients and methods We examined 50 patients who were treated at our hospital between April 1985 and December 1993. Various methods of stabilization were used: K-wires (n = 36), 4.5-mm screw (n = 12), or biodegradable screw (n = 2). Osteosynthesis material was removed after 6–8 weeks. Mean follow-up time was 18 (15–22) years. Outcomes were assessed with the Constant shoulder (CS) score, Disabilities of the Arm, Shoulder, and Hand (DASH) score, the simple shoulder test (SST), the Copeland shoulder impingement test, the cross-arm test, pain, stability of the AC joint, and complications. From radiographs, we evaluated AC and glenohumeral (GH) arthrosis, osteolysis of the lateral clavicle, and alignment of the clavicle with the acromion. Results Mean values were 90 (75–100) in CS score, 5.1 (0–41) in DASH score, and 11 (2–12) in SST. There was no statistically significant difference in CS score between the injured shoulder and the uninjured shoulder. The AC joint was clinically stable in 42 patients. In 38 patients, the clavicle alignment with the acromion was normal in radiographs. Lateral clavicle osteolysis (10 patients) appeared to be associated with permanent AC joint dislocation. Interpretation Surgery with a temporary fixation for acute grade-V AC joint dislocation leads to successful long-term functional results. Only minor disability occurred in some patients. PMID:23409813

2013-01-01

126

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

PubMed

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

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

2014-07-01

127

Stability of Boolean networks: the joint effects of topology and update rules.  

PubMed

We study the stability of orbits in large Boolean networks. We treat the case in which the network has a given complex topology, and we do not assume a specific form for the update rules, which may be correlated with local topological properties of the network. While recent past work has addressed the separate effects of complex network topology and certain classes of update rules on stability, only crude results exist about how these effects interact. We present a widely applicable solution to this problem. Numerical simulations confirm our theory and show that local correlations between topology and update rules can have profound effects on the qualitative behavior of these systems. PMID:25215788

Squires, Shane; Pomerance, Andrew; Girvan, Michelle; Ott, Edward

2014-08-01

128

Stability of Boolean networks: The joint effects of topology and update rules  

NASA Astrophysics Data System (ADS)

We study the stability of orbits in large Boolean networks. We treat the case in which the network has a given complex topology, and we do not assume a specific form for the update rules, which may be correlated with local topological properties of the network. While recent past work has addressed the separate effects of complex network topology and certain classes of update rules on stability, only crude results exist about how these effects interact. We present a widely applicable solution to this problem. Numerical simulations confirm our theory and show that local correlations between topology and update rules can have profound effects on the qualitative behavior of these systems.

Squires, Shane; Pomerance, Andrew; Girvan, Michelle; Ott, Edward

2014-08-01

129

The unpredictable material properties of bioabsorbable PLC interference screws and their adverse effects in ACL reconstruction surgery.  

PubMed

The aim of this study was to look at the clinical outcome of polylactide carbonate (PLC) interference screws in knee ligament reconstruction surgery. We prospectively followed up 59 patients who underwent primary hamstring anterior cruciate ligament (ACL) reconstructions using PLC (Calaxo screw; Smith and Nephew, Andover, MA) screws to secure the graft in the tibial tunnel. The average age was 34 years (range 17-55 years, SD 8.93). Twenty-three (39%) patients presented with complications [synovitis in 15% (nine) patients, prominent tibial swelling in 34% (20) patients and both in seven patients]. In comparison, similar complications were not seen in two groups of 59 age and sex matched patients in whom PLLA (Bio RCI; Smith and Nephew, Andover, MA) screws or Titanium (RCI; Smith and Nephew, Andover, MA) screws were used by the same surgeon. The problems encountered in the PLC screw group did not adversely affect knee stability. Six patients underwent exploration of the tibial tunnel site. A sterile white cheesy substance was removed, leaving an empty tibial tunnel. The ACL graft was found to be well attached to tibial tunnel in all cases. The PLC screw diameter, surface area or tibial tunnel diameter did not have any correlation to the occurrence of complications. Two patients required multiple washouts, one of whom developed a deep infection. The degradation of PLC screws does not follow the gradual and controlled pattern demonstrated in the ovine model. The unpredictable screw degradation, and the reaction to it can lead to serious clinical consequences. PMID:19083204

Konan, Sujith; Haddad, Fares Sami

2009-03-01

130

Foreign body reaction to a bioabsorbable interference screw after anterior cruciate ligament reconstruction  

PubMed Central

Bioabsorbable interference screws have been effective for graft fixation in anterior cruciate ligament (ACL) reconstruction. The overall complication rate associated with the use of these screws is low but some unique problems have been reported in the literature. We present a case of unusual tissue reaction to a bioabsorbable interference screw following ACL reconstruction. A young male underwent ACL reconstruction, during which a bioabsorbable interference screw was used for graft fixation at the tibial end. The patient presented with a pretibial swelling at 30 months after the operation. Exploration revealed chalky white remnants of the bioabsorbable screw with no evidence of infection. Histological studies confirmed a foreign body reaction against screw remnants with the presence of multinucleated giant cells. The patient had a full recovery with no compromise to graft stability. Bioabsorbable interference screws are usually inert but can initiate a tissue reaction. The presentation can be as late as 2–3 years postoperatively and may mimic an infection. Satisfactory results can be achieved by proper exploration and debridement. PMID:21686509

Umar, Muhammad; Baqai, Nadeem; Peck, Christopher

2009-01-01

131

Distal tibial physeal bridge: a complication from a tension band plate and screw construct. Report of a case.  

PubMed

We report on a case of a tension band plate and screw construct (Eight Plate) used over the anterior distal tibia in an 9-year-old girl in an attempt to induce recurvatum of the ankle joint to correct a recalcitrant equinus deformity. With growth of the distal tibial physis, the epiphyseal screw was drawn through the physis into the distal tibial metaphysis, resulting in the creation of a transphyseal bony bar. Caution should be exercised when attempting temporary hemiepiphyseodesis using a plate and screw construct in small epiphyses or in an osteopenic bone. PMID:22158054

Oda, Jon E; Thacker, Mihir M

2013-05-01

132

Tibial and Pretibial Cyst Formation After Anterior Cruciate Ligament Reconstruction With Bioabsorbable Interference Screw Fixation  

Microsoft Academic Search

Summary: We report a case of an osteolytic tibial enlargement in association with a pretibial cyst formation 8 months after successful anterior cruciate ligament reconstruction with autologous bone–patellar tendon–bone graft and tibial graft fixation with a bioabsorbable interference screw. No joint inflammatory reaction or graft insufficiency was detected. The patient underwent cyst excision and curettage of the tibial tunnel with

Vladimir Martinek; Niklaus F. Friederich

1999-01-01

133

Screw-fed pump system  

DOEpatents

A pump system includes a pump that includes a first belt and a second belt that are spaced apart from each other to provide generally straight sides of a passage there between. There is an inlet at one end of the passage and an outlet at an opposite end of the passage, with a passage length that extends between the inlet and the outlet. The passage defines a gap distance in a width direction between the straight sides at the passage inlet. A hopper includes an interior space that terminates at a mouth at the passage inlet. At least one screw is located within the interior space of the hopper and includes a screw diameter in the width direction that is less than or equal to the gap distance.

Sprouse, Kenneth M

2014-11-25

134

Helical screw expander evaluation project  

NASA Technical Reports Server (NTRS)

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.

Mckay, R.

1982-01-01

135

Effect of boot shaft stiffness on stability joint energy and muscular co-contraction during walking on uneven surface  

Microsoft Academic Search

Increased boot shaft stiffness may have a noticeable impact on the range of motion of the ankle joint. Therefore, the ability of the ankle joint to generate power for propulsion might be impaired. This might result in compensatory changes at the knee and hip joint. Besides, adaptability of the subtalar joint to uneven surface might be reduced, which could in

Harald Böhm; Matthias Hösl

2010-01-01

136

Outcome comparison of Lisfranc injuries treated through dorsal plate fixation versus screw fixation  

PubMed Central

OBJECTIVE: The objective of this prospective study was to test whether the treatment of Lisfranc injuries with open reduction and dorsal plate fixation would have the same or better functional outcomes as treatment with standard trans-articular screw fixation. METHODS: Sixty patients with primarily isolated Lisfranc joint injury were treated by open reduction and dorsal plate fixation or standard screw fixation. The patients were followed on average for 31 months. Evaluation was performed with patients' chief complaint, clinical examination, radiography, and AOFAS Midfoot Scale. RESULTS: Thirty two patients were treated with open reduction and dorsal plate fixation, and twenty eight patients were treated with open reduction and screw fixation. After two years follow-up, the mean AOFAS Midfoot score was 83.1 points in the dorsal plate fixation group and 78.5 points in the screw fixation group (p<0.01). Of the dorsal plate fixation group, radiographic analysis revealed anatomic reduction in twenty-nine patients (90.6%, 29/32) and nonanatomic reduction in three patients. Of the screw fixation group, radiographic analysis revealed anatomic reduction in twenty-three patients and nonanatomic reduction in five patients (82.1%, 23/28). CONCLUSIONS: Open reduction and dorsal plate fixation for a dislocated Lisfranc injury do have better short and median term outcome and a lower reoperation rate than standard screw ORIF. In our experience, we recommend using dorsal plate in ORIF on dislocated Lisfranc injuries. Level of Evidence II, Prospective Comparative Study.

Hu, Sun-jun; Chang, Shi-min; Li, Xiao-hua; Yu, Guang-rong

2014-01-01

137

Axial cyclic behavior of the bone–screw interface  

Microsoft Academic Search

Screw fixation strength is investigated by using a pullout test. Despite many screw pullout studies, the effects of loading rate on the pullout behavior of pedicle screws are not known. The objective of this study was to assess the effects of loading rate on the pullout stiffness and strength of pedicle screws. Sixty pedicle screws were inserted in foam blocks

Serkan ?nceo?lu; Mike Ehlert; Atilla Akbay; Robert F. McLain

2006-01-01

138

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

PubMed

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

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

2008-11-01

139

Arthrodesis of the Trapeziometacarpal Joint  

Microsoft Academic Search

Over a 10-year period, 32 trapeziometacarpal (TM) joint fusions were performed in 29 patients, and reviewed. Pin fixation with tension band wiring was used in 14 cases, screws in eight cases, a plate in six cases, K-wires in three cases and staple fixation in one case. None was bone grafted. Splinting was applied for 4 to 5 weeks. There were

A. CHAMAY; F. PIAGET-MOREROD

1994-01-01

140

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

Microsoft Academic Search

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

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

1998-01-01

141

21 CFR 872.4880 - Intraosseous fixation screw or wire.  

Code of Federal Regulations, 2011 CFR

...false Intraosseous fixation screw or wire. 872.4880 Section...4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...be inserted into fractured jaw bone segments to prevent their...

2011-04-01

142

21 CFR 872.4880 - Intraosseous fixation screw or wire.  

Code of Federal Regulations, 2013 CFR

...false Intraosseous fixation screw or wire. 872.4880 Section...4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...be inserted into fractured jaw bone segments to prevent their...

2013-04-01

143

21 CFR 872.4880 - Intraosseous fixation screw or wire.  

...false Intraosseous fixation screw or wire. 872.4880 Section...4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...be inserted into fractured jaw bone segments to prevent their...

2014-04-01

144

21 CFR 872.4880 - Intraosseous fixation screw or wire.  

Code of Federal Regulations, 2010 CFR

...false Intraosseous fixation screw or wire. 872.4880 Section...4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...be inserted into fractured jaw bone segments to prevent their...

2010-04-01

145

21 CFR 872.4880 - Intraosseous fixation screw or wire.  

Code of Federal Regulations, 2012 CFR

...false Intraosseous fixation screw or wire. 872.4880 Section...4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...be inserted into fractured jaw bone segments to prevent their...

2012-04-01

146

Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling  

Microsoft Academic Search

BACKGROUND: Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between

Lih-Huei Chen; Ching-Lung Tai; De-Mei Lee; Po-Liang Lai; Yen-Chen Lee; Chi-Chien Niu; Wen-Jer Chen

2011-01-01

147

The Mast Cell Stabilizer Ketotifen Fumarate Lessens Contracture Severity and Myofibroblast Hyperplasia: A Study of a Rabbit Model of Posttraumatic Joint Contractures  

PubMed Central

Background The propensity of the elbow to become stiff after trauma is widely appreciated and in this setting, the joint capsule is commonly recognized as the major motion-limiting anatomical structure. Affected joint capsules become fibrotic, characterized by myofibroblast hyperplasia and excessive collagen deposition. Mast cell hyperplasia is common within fibrotic tissue and mast cells are known to synthesize many profibrotic mediators. We have hypothesized that mast cell inhibition after skeletal injury will lessen the degree of contracture severity and will reduce myofibroblast hyperplasia within the joint capsule. Methods Posttraumatic contractures of the knee were created using a combination of intra-articular injury coupled to internal immobilization in skeletally mature, New Zealand white rabbits. Four groups of animals were studied: a non-operative control group (CON), an operative contracture group (ORC) and two-operative groups treated with a mast cell stabilizer, Ketotifen fumarate at doses of 0.5mg/kg (KF0.5) and 1.0mg/kg (KF1.0) twice daily, respectively. After 8 weeks of immobilization, flexion contractures were measured biomechanically and the posterior joint capsule was harvested for quantification of myofibroblast and mast cell numbers. Results Flexion contractures developed in the ORC group (58 ± 14°) and the severity of contracture was significantly reduced in both groups treated with Ketotifen (KF0.5: 42 ± 17° and KF1.0: 45 ± 10°, p<0.02). Joint capsule myofibroblast and mast cell numbers were significantly increased within the operative contracture group (p<0.001). In both surgical groups treated with Ketotifen, myofibroblast and mast cell numbers were significantly reduced (p<0.001). Conclusions The use of a mast cell stabilizer, Ketotifen was effective in reducing the biomechanical and cellular manifestations of joint capsule fibrosis in a rabbit model of posttraumatic joint contracture. This is suggestive that an inflammatory pathway, mediated by mast cell activation is involved in the induction of joint capsule fibrosis after traumatic injury. Clinical Relevance These results suggest mast cell activation is an important event in the genesis of posttraumatic joint contractures. Further work is needed to determine if mast cell inhibition has a role in the prevention of posttraumatic joint contractures in humans. PMID:20516323

Monument, Michael J.; Hart, David A.; Befus, A. Dean; Salo, Paul T.; Zhang, Mei; Hildebrand, Kevin A.

2010-01-01

148

A novel radiographic targeting guide for percutaneous placement of transfacet screws in the cervical spine with limited fluoroscopy: A cadaveric feasibility study  

PubMed Central

Background We describe a technique for percutaneous transfacet screw placement in the cervical spine without the need for lateral-view fluoroscopy. Methods Previously established articular pillar morphometry was used to define the ideal trajectory for transfacet screw placement in the subaxial cervical spine. A unique targeting guide was developed to allow placement of Kirschner wires across the facet joint at 90° without the guidance of lateral-view fluoroscopy. Kirschner wires and cannulated screws were placed percutaneously in 7 cadaveric specimens. Placement of instrumentation was performed entirely under modified anteroposterior-view fluoroscopy. All specimens were assessed for acceptable screw placement by 2 fellowship-trained orthopaedic spine surgeons using computed tomography. Open dissection was used to confirm radiographic interpretation. Acceptable placement was defined as a screw crossing the facet joint, achieving purchase in the inferior and superior articular processes, and not violating critical structures. Malposition was defined as a violation of the transverse foramen, spinal canal, or nerve root or inadequate fixation. Results A total of 48 screws were placed. Placement of 45 screws was acceptable. The 3 instances of screw malposition included a facet fracture, a facet distraction, and a C6-7 screw contacting the C7 nerve root in a specimen with a small C7 superior articular process. Conclusions Our data show that with the appropriate radiographic technique and a targeting guide, percutaneous transfacet screws can be safely placed at C3-7 without the need for lateral-view fluoroscopy during the targeting phase. Because of the variable morphometry of the C7 lateral mass, however, care must be taken when placing a transfacet screw at C6-7. Clinical Relevance This study describes a technique that has the potential to provide a less invasive strategy for posterior instrumentation of the cervical spine. Further investigation is needed before this technique can be applied clinically.

Jackson, David M.; Karp, Jacqueline E.; O'Brien, Joseph R.; Anderson, D. Greg; Gelb, Daniel E.; Ludwig, Steven C.

2012-01-01

149

Unifying Screw Geometry and Matrix Transformations  

Microsoft Academic Search

Transformation matrices are widely used in robotics for kinematic analysis and trajectory planning. Screw geome try offers better geometric insight into such analyses. In this article we unify the two approaches through the use of invariant properties of orthogonal matrices under simi larity transformations. We give a complete expression for the finite screw motion in terms of the entires of

A. E. Samuel; P. R. McAree; K. H. Hunt

1991-01-01

150

Antegrade-retrograde opposing lag screws for internal fixation of simple displaced talar neck fractures.  

PubMed

The talar neck is deviated medially with reference to the long axis of the body of the talus. In addition, it deviates plantarward. The talar neck fracture line is sometimes observed to be oriented obliquely (not perpendicular to the long axis of the talar neck). This occurs when the medially deviated talar neck strikes the horizontally oriented anterior lower tibial edge. Internal fixation of a simple displaced talar neck fracture usually requires 2 lag screws. Because the fracture line is obliquely oriented, a better method for positioning the screws perpendicular to the fracture line is to place them in a reversed direction to provide maximum interfragmentary compression at the fracture site, which could increase the likelihood of absolute stability with subsequent improvement in the incidence of fracture union and a reduction of complications, such as avascular necrosis of the body of the talus. Two lag screws are used, with the first inserted from posteriorly to anteriorly (perpendicular to the fracture line) using a medial approach after medial malleolar chevron osteotomy. The second screw is inserted from anteriorly to posteriorly (perpendicular to the fracture line) using an anterolateral approach. Both screw heads should be countersunk. A series of 8 patients underwent this form of internal fixation for talar neck fracture repair, with satisfactory functional outcomes. In conclusion, the use of antegrade-retrograde opposing lag screws is a reasonable method of internal fixation for simple displaced talar neck fractures. PMID:25459087

Abdelkafy, Ashraf; Imam, Mohamed Abdelnabi; Sokkar, Sherif; Hirschmann, Michael

2015-01-01

151

The use of self-reinforced biodegradable bone plates and screws in orthognathic surgery  

Microsoft Academic Search

Purpose: This report describes the authors' experience with self-reinforced biodegradable bone plates and screws to stabilize maxillary and mandibular osteotomies. Patient acceptance, demographics, types of osteotomy, means of stabilization, etiology of the deformity, complications, and patient disposition are reviewed. Patients and Methods: Seventy patients underwent 194 osteotomies of the maxilla and\\/or mandible. Stabilization of each osteotomy was achieved using self-reinforced

Timothy A. Turvey; R. Bryan Bell; Tinerfe J. Tejera; William R. Proffit

2002-01-01

152

Twin screw granulation: steps in granule growth.  

PubMed

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

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

2012-11-15

153

Effectiveness of Glenohumeral-Joint Stability Braces in Limiting Active and Passive Shoulder Range of Motion in Collegiate Football Players  

PubMed Central

Objective: To determine the effectiveness of glenohumeral-joint stability braces in limiting active and passive shoulder abduction and external rotation in collegiate football players. Design and Setting: A 2-factor, repeated-measures design was used. The independent variables were brace condition (Denison and Duke Wyre harness, Sawa shoulder brace) and force application (active, passive). The dependent variables were shoulder abduction (45° braced limit) and external-rotation angular displacements. Subjects: Fifteen National Collegiate Athletic Association Division I male college football players (age = 19.9 ± 1.37 years, height = 183.2 ± 7.85 cm, mass = 89.9 ± 14.79 kg) participated in the study. Measurements: We used the PEAK Motus motion analysis system to measure angular displacements. Results: Neither brace maintained the arm position at the 45° braced limit during active or passive shoulder abduction (motion ranged from 56.8° to 73.0°). Although we did not use a priori external-rotation limits in this study, motion ranged from 71.6° to 93.9° with the braces. A repeated-measures multivariate analysis of variance indicated no significant interaction effect (P = .41), but main effects were significant for brace condition and force application (P < .001). Reported differences are statistically significant. For abduction, the Denison and Duke Wyre harness resulted in 12.3° (21%) greater angular displacement than the Sawa shoulder brace, and passive abduction resulted in 3.9° (6%) more angular displacement than active abduction. For external rotation, the Denison and Duke Wyre harness resulted in 6.7° (9%) more angular displacement than the Sawa shoulder brace, and passive external rotation resulted in 15.6° (21%) more angular displacement than active external rotation. Conclusions: Preset, braced abduction motion limits were not realized during active and passive physiologic loading of the glenohumeral joint. However, protection against the vulnerable position of 90° of abduction and external rotation was attained at a preset braced limit of 45° of abduction (the exception was the Denison and Duke Wyre harness during passive external rotation). The Sawa shoulder brace was most effective for this purpose. PMID:15173866

Weise, Keon; Tierney, Ryan; Swanik, Kathleen A.

2004-01-01

154

Effectiveness of Glenohumeral-Joint Stability Braces in Limiting Active and Passive Shoulder Range of Motion in Collegiate Football Players.  

PubMed

OBJECTIVE: To determine the effectiveness of glenohumeral-joint stability braces in limiting active and passive shoulder abduction and external rotation in collegiate football players. DESIGN AND SETTING: A 2-factor, repeated-measures design was used. The independent variables were brace condition (Denison and Duke Wyre harness, Sawa shoulder brace) and force application (active, passive). The dependent variables were shoulder abduction (45 degrees braced limit) and external-rotation angular displacements. SUBJECTS: Fifteen National Collegiate Athletic Association Division I male college football players (age = 19.9 +/- 1.37 years, height = 183.2 +/- 7.85 cm, mass = 89.9 +/- 14.79 kg) participated in the study. MEASUREMENTS: We used the PEAK Motus motion analysis system to measure angular displacements. RESULTS: Neither brace maintained the arm position at the 45 degrees braced limit during active or passive shoulder abduction (motion ranged from 56.8 degrees to 73.0 degrees ). Although we did not use a priori external-rotation limits in this study, motion ranged from 71.6 degrees to 93.9 degrees with the braces. A repeated-measures multivariate analysis of variance indicated no significant interaction effect (P =.41), but main effects were significant for brace condition and force application (P <.001). Reported differences are statistically significant. For abduction, the Denison and Duke Wyre harness resulted in 12.3 degrees (21%) greater angular displacement than the Sawa shoulder brace, and passive abduction resulted in 3.9 degrees (6%) more angular displacement than active abduction. For external rotation, the Denison and Duke Wyre harness resulted in 6.7 degrees (9%) more angular displacement than the Sawa shoulder brace, and passive external rotation resulted in 15.6 degrees (21%) more angular displacement than active external rotation. CONCLUSIONS: Preset, braced abduction motion limits were not realized during active and passive physiologic loading of the glenohumeral joint. However, protection against the vulnerable position of 90 degrees of abduction and external rotation was attained at a preset braced limit of 45 degrees of abduction (the exception was the Denison and Duke Wyre harness during passive external rotation). The Sawa shoulder brace was most effective for this purpose. PMID:15173866

Weise, Keon; Sitler, Michael R.; Tierney, Ryan; Swanik, Kathleen A.

2004-06-01

155

Biomechanical Comparison of Osteoporotic Distal Radius Fractures Fixed by Distal Locking Screws with Different Length  

PubMed Central

Objectives To evaluate the postoperative stability of osteoporotic distal radius fractures fixed with distal locking screws with different length. Methods A comminuted extra-articular dorsally unstable distal radius fracture, treated with volar locking plate system, was created. The 18 specimens were randomized into 3 groups based on distal locked screws with different length: Group A had unicortical screws with 50% length to the dorsal cortex. Group B had unicortical screws with 75% length to the dorsal cortex. Group C had bicortical screws. Axial compression and bending loads were imposed on the models before and after cycling testing as well as load to clinical and catastrophic failure. Results Minimum change in stiffness was observed before and after fatigue for all groups. The final stiffness to bending forces was statistically similar in all groups, but stiffness to axial compression was statistically significant different: Group A approached significance with respect to groups B and C (P?=?0.017, 0.009), whereas stiffness in group B and C was statistically similar (P?=?0.93). Load to clinical failure was significantly less for group A (456.54±78.59 N) compared with groups B (580.24±73.85 N) and C (591.07±38.40 N). Load to catastrophic failure was statistically similar between groups, but mean values for Group A were 18% less than means for Group C. Conclusions The volar locking plate system fixed with unicortical locking screws with at least 75% length not only produced early stability for osteoporotic distal radius fractures, but also avoided extensor tendon complications due to dorsal screw protrusion. PMID:25080094

Liu, Xiong; Wu, Wei-dong; Fang, Ya-feng; Zhang, Mei-chao; Huang, Wen-hua

2014-01-01

156

The biomechanics of guided growth: does screw size, plate size, or screw configuration matter?  

PubMed

Guided growth with the eight-plate is a commonly used technique to correct angular limb deformities in children. However, the optimal combination of plate size, screw size, and screw configuration has not been determined. Using osteotomized femoral sawbones and a rail frame, we developed a growth model to examine the effect of these variables at 6-month, 12-month, and 18-month growth increments. The mean annual coronal plane change was 11.3°. Screw size and plate size were not associated with the rate of angular correction. Screw configuration was important, with parallel screws resulting in optimal correction at all time points compared with divergent screws (P<0.05). PMID:24322536

Schoenleber, Scott J; Iobst, Christopher A; Baitner, Avi; Standard, Shawn C

2014-03-01

157

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

PubMed Central

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

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

2014-01-01

158

The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature.  

PubMed

Mandibulo-maxillary fixation (MMF) screws are inserted into the bony base of both jaws in the process of fracture realignment and immobilisation. The screw heads act as anchor points to fasten wire loops or rubber bands connecting the mandible to the maxilla. Traditional interdental chain-linked wiring or arch bar techniques provide the anchorage by attached cleats, hooks, or eyelets. In comparison to these tooth-borne appliances MMF screws facilitate and shorten the way to achieve intermaxillary fixation considerably. In addition, MMF screws help to reduce the hazards of glove perforation and wire stick injuries. On the downside, MMF screws are attributed with the risk of tooth root damage and a lack of versatility beyond the pure maintenance of occlusion such as stabilizing loose teeth or splinting fragments of the alveolar process. The surgical technique of MMF screws as well as the pros and cons of the clinical application are reviewed. The adequate screw placement to prevent serious tooth root injuries is still an issue to rethink and modify conceptual guidelines. PMID:22110819

Cornelius, Carl-Peter; Ehrenfeld, Michael

2010-06-01

159

The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature  

PubMed Central

Mandibulo-maxillary fixation (MMF) screws are inserted into the bony base of both jaws in the process of fracture realignment and immobilisation. The screw heads act as anchor points to fasten wire loops or rubber bands connecting the mandible to the maxilla. Traditional interdental chain-linked wiring or arch bar techniques provide the anchorage by attached cleats, hooks, or eyelets. In comparison to these tooth-borne appliances MMF screws facilitate and shorten the way to achieve intermaxillary fixation considerably. In addition, MMF screws help to reduce the hazards of glove perforation and wire stick injuries. On the downside, MMF screws are attributed with the risk of tooth root damage and a lack of versatility beyond the pure maintenance of occlusion such as stabilizing loose teeth or splinting fragments of the alveolar process. The surgical technique of MMF screws as well as the pros and cons of the clinical application are reviewed. The adequate screw placement to prevent serious tooth root injuries is still an issue to rethink and modify conceptual guidelines. PMID:22110819

Cornelius, Carl-Peter; Ehrenfeld, Michael

2010-01-01

160

Semi-Empirical Screw Compressor Chiller Model  

E-print Network

A screw chiller model which is based on a first principles, semi-empirical analysis that describes the system performance based on observations of the thermodynamic processes is developed. This model is a modified method to empirically derive...

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

161

Rotordynamics of Twin-Screw Pumps  

E-print Network

rotordynamic behavior. The work in this dissertation presents: (1) the axisymmetric structural model of the rotors (2) the proposed dynamic pressure model, (3) the screw pump rotor response, (4) the experimental validation of the dynamic pressure model...

Aboel Hassan Muhammed, Ameen

2013-02-26

162

Morphological character of cervical spine for anterior transpedicular screw fixation  

PubMed Central

Background: Anterior cervical interbody grafts/cages combined with a plate were frequently used in multilevel discectomies/corpectomies. In order to avoid additional posterior stabilization in patients who undergo anterior reconstructive surgery, an anterior cervical transpedicular screw fixation, which offers higher stability is desirable. We investigated in this study the anatomical (morphologic) characters for cervical anterior transpedicular screw fixation. Materials and Methods: Left pedicle parameters were measured on computed tomography (CT) images based on 36 cervical spine CT scans from healthy subjects. The parameters included outer pedicle width (Distance from lateral to medial pedicle surface in the coronal plane), outer pedicle height (OPH) (Distance from upper to lower pedicle surface in the sagittal plane), maximal pedicle axis length (MPAL), distance transverse insertion point (DIP), distance of the insertion point to the upper end plate (DIUP), pedicle sagittal transverse angle (PSTA) and pedicle transverse angle (PTA) at C3 to C7. Results: The values of outer pedicle width and MPAL in males were larger than in females from C3 to C7. The OPH in males was larger than in females at C3 to C6, but there was no difference at C7. The DIP and PTA were significantly greater in males than in females at C3, but there was no difference in the angle at C4-7. The PSTA was not statistically different between genders at C3, 4, 7, but this value in males was larger than females at C5, 6. The DIUP was significantly greater in males at C3, 4, 6, 7 but was non significant at C5. Conclusions: The placement of cervical anterior transpedicular screws should be individualized for each patient and based on a detailed preoperative planning. PMID:24379459

Zhou, Rong-Ping; Jiang, Jian; Zhan, Zi-Chun; Zhou, Yang; Liu, Zhi-Li; Yin, Qing-Shui

2013-01-01

163

Additional Drive Circuitry for Piezoelectric Screw Motors  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

164

Percutaneous Computer Assisted Iliosacral Screwing: Clinical Validation  

Microsoft Academic Search

\\u000a This paper describes the clinical validation of an image-guided system for the percutaneous placement of iliosacral screws.\\u000a The goals of the approach are to decrease surgical complications, with a percutaneous technique, and to increase the accuracy\\u000a and security of screw positioning thanks to a computer assisted system. Pre-operative planning is performed on CT-scan images\\u000a and a 3D model is built.

Lionel Carrat; Jerome Tonetti; Philippe Merloz; Jocelyne Troccaza

2000-01-01

165

Intraarticular migration of a broken biodegradable interference screw after anterior cruciate ligament reconstruction  

Microsoft Academic Search

Poly-l-lactic acid biodegradable screws have been used effectively for graft fixation in anterior cruciate ligament (ACL) reconstruction. The overall complication rate associated with the use of this implant is low, although some authors reported complications, such as osteolysis and aseptic effusion of the knee joint. We report a case of a 29-year-old female patient with a failure of a biodegradable

M. H. Baums; B. A. Zelle; W. Schultz; T. Ernstberger; H.-M. Klinger

2006-01-01

166

Kinematics of a five-degrees-of-freedom parallel manipulator using screw theory  

Microsoft Academic Search

In this work, the kinematic analysis of a five-degrees-of-freedom decoupled parallel manipulator is approached by means of\\u000a the theory of screws. The architecture of the parallel manipulator under study is such that the translational motion of the\\u000a moving platform, with respect to the fixed platform, is controlled by means of a central limb provided with two active prismatic\\u000a joints while

Jaime Gallardo-Alvarado; Benjamín Arroyo-Ramírez; Héctor Rojas-Garduño

2009-01-01

167

The use of the Herbert bone screw by the freehand-method for osteosynthesis scaphoid fracture  

Microsoft Academic Search

Summary  \\u000a Scaphoid fracture is, in most cases, usually still treated conservatively. The disadvantages of long-term immobilization are\\u000a stiffness of the wrist joint, loss of strength and higher costs. The osteosynthesis of the scaphoid fracture with the Herbert\\u000a bone screw restores the exact form and length and the normal position of the scaphoid to the other carpal bones. It prevents\\u000a non-unions,

R. B. Brauer; M. Dierking; K. D. Werber

1997-01-01

168

Delayed subarachnoid hemorrhage following failed odontoid screw fixation.  

PubMed

Iatrogenic vascular injury is a rare but potentially devastating complication of cervical spine instrumentation. The authors report on a patient who developed an anterior spinal artery pseudoaneurysm associated with delayed subarachnoid hemorrhage after undergoing odontoid screw placement 14 months earlier. This 86-year-old man presented with spontaneous subarachnoid hemorrhage (Fisher Grade 4) and full motor strength on neurological examination. Imaging demonstrated pseudarthrosis of the odontoid process, extension of the odontoid screw beyond the posterior cortex of the dens, and a pseudoaneurysm arising from an adjacent branch of the anterior spinal artery. Due to the aneurysm's location and lack of active extravasation, endovascular treatment was not attempted. Posterior C1-2 fusion was performed to treat radiographic and clinical instability of the C1-2 joint. Postoperatively, the patient's motor function remained intact. Almost all cases of vascular injury related to cervical spine instrumentation are recognized at surgery. To the authors' knowledge, this is the first report of delayed vascular injury following an uncomplicated cervical fixation. This case further suggests that the risk of this phenomenon may be elevated in cases of failed fusion. PMID:21395399

Wilson, David A; Fusco, David J; Theodore, Nicholas

2011-06-01

169

Plan to procedure: combining 3D templating with rapid prototyping to enhance pedicle screw placement  

NASA Astrophysics Data System (ADS)

Spinal fusion procedures involving the implantation of pedicle screws have steadily increased over the past decade because of demonstrated improvement in biomechanical stability of the spine. However, current methods of spinal fusion carries a risk of serious vascular, visceral, and neurological injury caused by inaccurate placement or inappropriately sized instrumentation, which may lead to patient paralysis or even fatality. 3D spine templating software developed by the Biomedical Imaging Resource (BIR) at Mayo Clinic allows the surgeon to virtually place pedicle screws using pre-operative 3D CT image data. With the template plan incorporated, a patient-specific 3D anatomic model is produced using a commercial rapid prototyping system. The pre-surgical plan and the patient-specific model then are used in the procedure room to provide real-time visualization and quantitative guidance for accurate placement of each pedicle screw, significantly reducing risk of injury. A pilot study was conducted at Mayo Clinic by the Department of Radiology, the Department of Orthopedics, and the BIR, involving seven complicated pediatric spine cases. In each case, pre-operative 3D templating was carried out and patient specific models were generated. The plans and the models were used intra-operatively, providing precise pedicle screw starting points and trajectories. Postoperative assessment by the surgeon confirmed all seven operations were successful. Results from the study suggest that patient-specific, 3D anatomic models successfully acquired from 3D templating tools are valuable for planning and conducting pedicle screw insertion procedures.

Augustine, Kurt E.; Stans, Anthony A.; Morris, Jonathan M.; Huddleston, Paul M.; Matsumoto, Jane M.; Holmes, David R., III; Robb, Richard A.

2010-02-01

170

Comparison of screw and screwless fixation in cementless total knee arthroplasty.  

PubMed

This study compared two groups of consecutive patients undergoing total knee arthroplasty (TKA) with an identical cementless tibial baseplate supplementally fixated with and without screws. In 58 TKAs, two 6.5-mm cancellous screws were used for fixation, and in 58 TKAs, screwless fixation was used. Clinical evaluation was performed using the Hospital for Special Surgery knee score, and fluoroscopically guided radiographs were evaluated for radiolucencies. In the screw fixation group, average follow-up was 82+/-6 months (range, 59-89 months) and average patient age at surgery was 63 years. For the screwless fixation group, average follow-up was 67+/-5 months (range, 48-76 months) and average patient age at surgery was 62 years. Average knee score was 97 for the screw fixation group and 98 for the screwless fixation group. This study demonstrated stability in cementless TKA both with and without screw fixation in the mid-term using the Natural-Knee II tibial component. PMID:19292215

Ferguson, Ryan P; Friederichs, Matthew G; Hofmann, Aaron A

2008-02-01

171

Effect of bone material properties on effective region in screw-bone model: an experimental and finite element study  

PubMed Central

Background There have been numerous studies conducted to investigate the pullout force of pedicle screws in bone with different material properties. However, fewer studies have investigated the region of effect (RoE), stress distribution and contour pattern of the cancellous bone surrounding the pedicle screw. Methods Screw pullout experiments were performed from two different foams and the corresponding reaction force was documented for the validation of a computational pedicle screw-foam model based on finite element (FE) methods. After validation, pullout simulations were performed on screw-bone models, with different bone material properties to model three different age groups (<50, 50–75 and >75 years old). At maximum pullout force, the stress distribution and average magnitude of Von Mises stress were documented in the cancellous bone along the distance beyond the outer perimeter pedicle screw. The radius and volume of the RoE were predicted based on the stress distribution. Results The screw pullout strengths and the load–displacement curves were comparable between the numerical simulation and experimental tests. The stress distribution of the simulated screw-bone vertebral unit showed that the radius and volume of the RoE varied with the bone material properties. The radii were 4.73 mm, 5.06 mm and 5.4 mm for bone properties of ages >75, 75?>?ages >50 and ages <50 years old, respectively, and the corresponding volumes of the RoE were 6.67 mm3, 7.35 mm3 and 8.07 mm3, respectively. Conclusions This study demonstrated that there existed a circular effective region surrounding the pedicle screw for stabilization and that this region was sensitive to the bone material characteristics of cancellous bone. The proper amount of injection cement for augmentation could be estimated based on the RoE in the treatment of osteoporosis patients to avoid leakage in spine surgery. PMID:24952724

2014-01-01

172

Design and testing of external fixator bone screws.  

PubMed

In external fixation, bone screw loosening still presents a major clinical problem. For this study, the design factors influencing the mechanics of the bone-screw interface were analysed and various experimental screws designed with the intention of maximizing the strength and stiffness of the inserted screw. Push-in, pull-out and bending tests were then carried out on the three experimental screws, and on two commercially available screws in both a synthetic material and in cadaveric bone; photoelastic tests on different screw threadforms were also performed. The results of the push-in and pull-out tests indicate that both the screw threadform and cutting head have a significant effect on the holding strength of the screw. The photoelastic tests show that most of the applied load is distributed over the first few threads closest to the load, and that the area between the thread crests is subjected to high shear stresses. PMID:2266740

Evans, M; Spencer, M; Wang, Q; White, S H; Cunningham, J L

1990-11-01

173

Effect of Screw Length on Bioabsorbable Interference Screw Fixation in a Tibial Bone Tunnel  

Microsoft Academic Search

Initial tibial fixation strength is the weak link after anterior cruciate ligament reconstruction with a quadrupled hamstring tendon graft fixed with bioabsorbable interference screws. The purpose of this study was to determine the biomechanical differences between 28-mm and tapered 35-mm interference screws for tibial fixation of a soft tissue graft in 16 young cadaveric tibias. Failure mode, displacement before failure,

Jeffrey B. Selby; Darren L. Johnson; Peter Hester; David N. M. Caborn

2001-01-01

174

The Turn of the Screw: Optimal Design of an Archimedes Screw  

Microsoft Academic Search

The geometry of an Archimedes screw is governed by certain external parameters (its outer radius, length, and slope) and certain internal parameters (its inner radius, number of blades, and the pitch of the blades). The external parameters are usually determined by the location of the screw and how much water is to be lifted. The internal parameters, however, are free

Chris Rorres

2000-01-01

175

Assessment of a percutaneous iliosacral screw insertion simulator  

E-print Network

BACKGROUND: Navigational simulator use for specialized training purposes is rather uncommon in orthopaedic and trauma surgery. However, it reveals providing a valuable tool to train orthopaedic surgeons and help them to plan complex surgical procedures. PURPOSE: This work's objective was to assess educational efficiency of a path simulator under fluoroscopic guidance applied to sacroiliac joint percutaneous screw fixation. MATERIALS AND METHODS: We evaluated 23 surgeons' accuracy inserting a guide-wire in a human cadaver experiment, following a pre-established procedure. These medical trainees were defined in three prospective respects: novice or skilled; with or without theoretical knowledge; with or without surgical procedure familiarity. Analysed criteria for each tested surgeon included the number of intraoperative X-rays taken in order to achieve the surgical procedure as well as an iatrogenic index reflecting the surgeon's ability to detect any hazardous trajectory at the time of performing said procedu...

Tonetti, J; Girard, P; Dubois, M; Merloz, P; Troccaz, Jocelyne; 10.1016/j.otsr.2009.07.005

2009-01-01

176

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

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

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

177

The use of CT in the development and implementation of a preoperative protocol to aid in pedicle screw placement during scoliosis surgery.  

PubMed

Scoliosis surgical constructs, using pedicle screws, provide increased fixed penetrable points for rod attachment. This allows improved curve correction and increases hardware stability. We have implemented a multidetector CT evaluation of the spine with post-process image manipulation to aid pedicle screw placement for deformity correction. Preoperative scanning was done with a Philips Brilliance 16 multislice CT scanner. The created image dataset provided valuable preoperative information regarding pedicle morphology, suitability for screw placement and preoperative screw planning. Projected intraoperatively, the images increased the surgeon's confidence during screw placement, especially in large deformities with severe rotation. Improving pre- and intraoperative pedicle information is a valuable tool in operative management of children with spinal deformity. PMID:18265967

Jamieson, Douglas; Perdios, Angeliki; Varghese, Renjit; Reilly, Christopher W

2008-04-01

178

Effect of Filler Metal Composition on the Strength of Yttria Stabilized Zirconia Joints Brazed with Pd-Ag-CuO x  

NASA Astrophysics Data System (ADS)

Various compositions in the Ag-CuO x system are being investigated as potential filler metals for use in air brazing high-temperature electrochemical devices such as solid oxide fuel cells and gas concentrators. Prior work has shown that the melting temperature, and therefore the potential operational temperature, of these materials can be increased by alloying with palladium. The current study examines the effects of palladium addition on the joint strength of specimens prepared from yttria stabilized zirconia (YSZ) bars brazed with three different families of filler metals: Ag-CuO, 5Pd-Ag-CuO, and 15Pd-Ag-CuO. In general, it was found that palladium leads to a small-to-moderate decrease in joint strength, particularly in low copper oxide containing filler metals. However, the declination in strength is likely an acceptable trade-off for increased use temperature. In addition, a critical composition was observed for each filler metal series at which the mechanism for joint failure underwent a transition, typically from ductile to brittle failure. In each case, this composition corresponds approximately to the silver-rich boundary composition of the liquid miscibility gap in each system at the temperature of brazing.

Darsell, Jens T.; Weil, K. Scott

2008-09-01

179

Impact of screw configuration on the particle size distribution of granules produced by twin screw granulation.  

PubMed

Twin screw granulation (TSG) has been reported by different research groups as an attractive technology for continuous wet granulation. However, in contrast to fluidized bed granulation, granules produced via this technique typically have a wide and multimodal particle size distribution (PSD), resulting in suboptimal flow properties. The aim of the current study was to evaluate the impact of granulator screw configuration on the PSD of granules produced by TSG. Experiments were performed using a 25mm co-rotating twin screw granulator, being part of the ConsiGma™-25 system (a fully continuous from-powder-to-tablet manufacturing line from GEA Pharma Systems). Besides the screw elements conventionally used for TSG (conveying and kneading elements), alternative designs of screw elements (tooth-mixing-elements (TME), screw mixing elements (SME) and cutters) were investigated using an ?-lactose monohydrate formulation granulated with distilled water. Granulation with only conveying elements resulted in wide and multimodal PSD. Using kneading elements, the width of the PSD could be partially narrowed and the liquid distribution was more homogeneous. However, still a significant fraction of oversized agglomerates was obtained. Implementing additional kneading elements or cutters in the final section of the screw configuration was not beneficial. Furthermore, granulation with only TME or SME had limited impact on the width of the PSD. Promising results were obtained by combining kneading elements with SME, as for these configurations the PSD was narrower and shifted to the size fractions suitable for tableting. PMID:25562758

Vercruysse, J; Burggraeve, A; Fonteyne, M; Cappuyns, P; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

2015-02-01

180

Rotary screw compressors in the gas patch  

SciTech Connect

In 1959, Howden introduced the oil-injected rotary screw (OIS) compressor, which has, since then, methodically replaced the reciprocating (piston) compressor in applications such as air, refrigeration and fuel gas. Rotary screw compressors have been making inroads in gas recovery, a field once dominated by reciprocating compressors. Rotary screws do not require extensive maintenance, thus downtime is minimized throughout an operating year. Preventive maintenance is simple, since it consists of regular oil sample analysis which does not require system shut-down. As a result of the slide valve, OIS compressors can tune to field conditions with the greatest of ease, and without complicated process control. In addition, this method of capacity control is more efficient than unloading or use of a bypass-recirculation line. Both engineers and operators alike have found this flexibility to be a most redeeming feature. Finally, OIS compressors are capable of much larger flows then recips. 2 figs.

Jandjel, D.G.

1996-01-01

181

Screw expander for light duty diesel engines  

NASA Technical Reports Server (NTRS)

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.

1983-01-01

182

Biomechanical study of expandable pedicle screw fixation in severe osteoporotic bone comparing with conventional and cement-augmented pedicle screws.  

PubMed

Pedicle screws are widely utilized to treat the unstable thoracolumbar spine. The superior biomechanical strength of pedicle screws could increase fusion rates and provide accurate corrections of complex deformities. However, osteoporosis and revision cases of pedicle screw substantially reduce screw holding strength and cause loosening. Pedicle screw fixation becomes a challenge for spine surgeons in those scenarios. The purpose of this study was to determine if an expandable pedicle screw design could be used to improve biomechanical fixation in osteoporotic bone. Axial mechanical pull-out test was performed on the expandable, conventional and augmented pedicle screws placed in a commercial synthetic bone block which mimicked a human bone with severe osteoporosis. Results revealed that the pull-out strength and failure energy of expandable pedicle screws were similar with conventional pedicle screws augmented with bone cement by 2 ml. The pull-out strength was 5-fold greater than conventional pedicle screws and the failure energy was about 2-fold greater. Besides, the pull-out strength of expandable screw was reinforced by the expandable mechanism without cement augmentation, indicated that the risks of cement leakage from vertebral body would potentially be avoided. Comparing with the biomechanical performances of conventional screw with or without cement augmentation, the expandable screws are recommended to be applied for the osteoporotic vertebrae. PMID:24907127

Chen, Yi-Long; Chen, Wen-Chuan; Chou, Chi-Wei; Chen, Jou-Wen; Chang, Chia-Ming; Lai, Yu-Shu; Cheng, Cheng-Kung; Wang, Shih-Tien

2014-11-01

183

Prosthesis loading after temporomandibular joint replacement surgery: a musculoskeletal modeling study.  

PubMed

One of the most widely reported complications associated with temporomandibular joint (TMJ) prosthetic total joint replacement (TJR) surgery is condylar component screw loosening and instability. The objective of this study was to develop a musculoskeletal model of the human jaw to assess the influence of prosthetic condylar component orientation and screw placement on condylar component loading during mastication. A three-dimensional model of the jaw comprising the maxilla, mandible, masticatory muscles, articular cartilage, and articular disks was developed. Simulations of mastication and a maximum force bite were performed for the natural TMJ and the TMJ after prosthetic TJR surgery, including cases for mastication where the condylar component was rotated anteriorly by 0 deg, 5 deg, 10 deg, and 15 deg. Three clinically significant screw configurations were investigated: a complete, posterior, and minimal-posterior screw (MPS) configuration. Increases in condylar anterior rotation led to an increase in prosthetic condylar component contact stresses and substantial increases in condylar component screw stresses. The use of more screws in condylar fixation reduced screw stress magnitudes and maximum condylar component stresses. Screws placed superiorly experienced higher stresses than those of all other condylar fixation screws. The results of the present study have important implication for the way in which prosthetic components are placed during TMJ prosthetic TJR surgery. PMID:25565306

Ackland, David C; Moskaljuk, Adrian; Hart, Chris; Vee Sin Lee, Peter; Dimitroulis, George

2015-04-01

184

Pedicle screw-based posterior dynamic stabilisation of the lumbar spine: in vitro cadaver investigation and a finite element study.  

PubMed

Pedicle screw-based dynamic constructs either benefit from a dynamic (flexible) interconnecting rod or a dynamic (hinged) screw. Both types of systems have been reported in the literature. However, reports where the dynamic system is composed of two dynamic components, i.e. a dynamic (hinged) screw and a dynamic rod, are sparse. In this study, the biomechanical characteristics of a novel pedicle screw-based dynamic stabilisation system were investigated and compared with equivalent rigid and semi-rigid systems using in vitro testing and finite element modelling analysis. All stabilisation systems restored stability after decompression. A significant decrease in the range of motion was observed for the rigid system in all loadings. In the semi-rigid construct the range of motion was significantly less than the intact in extension, lateral bending and axial rotation loadings. There were no significant differences in motion between the intact spine and the spine treated with the dynamic system (P>0.05). The peak stress in screws was decreased when the stabilisation construct was equipped with dynamic rod and/or dynamic screws. PMID:24708377

Oktenoglu, T; Erbulut, D U; Kiapour, A; Ozer, A F; Lazoglu, I; Kaner, T; Sasani, M; Goel, V K

2015-08-01

185

Mechanical behavior of screws in normal and osteoporotic bone  

Microsoft Academic Search

Fracture fixation in severe osteoporotic bone by means of implants that rely on screw anchorage is still a clinical problem. So far, a sufficiently accurate prediction of the holding capacity of screws as a function of local bone morphology has not been obtained. In this study the ultimate pullout loads of screws in the epi-, meta-, and diaphyseal regions of

J. Seebeck; J. Goldhahn; M. M. Morlock; E. Schneider

2005-01-01

186

Joint swelling  

MedlinePLUS

Swelling of a joint ... Joint swelling may occur along with joint pain . The swelling may cause the joint to appear larger or abnormally shaped. Joint swelling can cause pain or stiffness. After an ...

187

Nylon screws make inexpensive coil forms  

NASA Technical Reports Server (NTRS)

Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

Aucoin, G.; Rosenthal, C.

1978-01-01

188

Analysis of Rotor Contact for Screw Compressor  

Microsoft Academic Search

A reliability evaluation of meshing rotor surfaces needs contact theory on a micro size area. We propose a method to evaluate whether a screw compressor rotor has enough contact fatigue strength. The method is based on analyses of three dimensional curvatures and the Hertz contact pressure. At a contact point one of the principal curvatures directs the rotor's sealing line

Hirotaka Kameya; Masakazu Aoki; Shigekazu Nozawa

2004-01-01

189

HERBERT SCREW FIXATION OF SCAPHOID FRACTURES  

Microsoft Academic Search

er eviewed the records of 431 patients who had open reduction and internal fixation of the scaphoid performed by one surgeon (TJH) over a 13-year period. The Herbert bone screw provided adequate internal fixation without the use of plaster immobilisation, promoting a rapid functional recovery. On average, patients returned to work 4.7 weeks after surgery and wrist function was significantly

S. L. FILAN; T. J. HERBERT

190

Pedicle screw placement with O-arm and stealth navigation.  

PubMed

Various navigation systems are available to aid pedicle screw placement. The O-arm replaces the need for fluoroscopy and generates a 3-dimensional volumetric dataset that can be viewed as transverse, coronal, and sagittal images of the spine, similar to computed tomography (CT) scanning. The dataset can be downloaded to the Stealth system (Medtronic Navigation, Louisville, Colorado) for real-time intraoperative navigation.The main objectives of the current study were to assess (1) accuracy of pedicle screw placement using the O-arm/Stealth system, and (2) time for draping, positioning of the O-arm, and screw placement. Of 188 screws (25 patients), 116 had adequate images for analysis. The average time for O-arm draping was 3.5 minutes. Initial O-arm positioning was 6.1 minutes, and final positioning was 4.9 minutes. Mean time for screw placement, including O-arm draping and positioning and array attachment, was 8.1 minutes per screw. Mean time for screw placement alone was 5.9 minutes per screw. Screw placements on final O-arm images were on average 3.14 mm deeper than on the snapshot navigation images. Three screws (2.6%) breached the medial cortex, and 3 screws (2.6%) were misaligned and did not follow the pilot hole trajectory.The use of the O-arm/Stealth system was associated with a low rate of pedicle screw misalignment. The time to place screws was less than previously reported with CT navigation, but longer than conventional techniques. It is important to be aware of the potential discrepancy between snapshot navigation images and actual screw placement on final O-arm images. Our findings suggest that final screw positions may be deeper than awl positions appear on navigation images. PMID:22229616

Patil, Suresh; Lindley, Emily M; Burger, Evalina L; Yoshihara, Hiroyuki; Patel, Vikas V

2012-01-01

191

Fatigue strength of common tibial intramedullary nail distal locking screws  

PubMed Central

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 surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Methods Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. Results The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of withstanding more than a week of weight bearing. If two small diameter screws are used, our tests showed that the probability of withstanding a week of weight bearing increases from zero to about 20 percent, which is similar to having a single 4.5 mm diameter screw providing fixation. Conclusion Our results show that selecting the system that uses the largest distal locking screws would offer the best fatigue resistance for an unstable fracture pattern subjected to full weight bearing. Furthermore, using multiple screws will substantially reduce the risk of premature hardware failure. PMID:19371438

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

2009-01-01

192

COPYRIGHT 2005 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED Early Tension Loss in an Anterior  

E-print Network

COPYRIGHT © 2005 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED 381 Early Tension Loss washer, double staples, a bioabsorbable interference screw, and a WasherLoc). Three cyclic loading.0001), 64% for the interference screw (p = 0.0001), and 56% for the WasherLoc (p

Hull, Maury

193

Influence of the implant abutment types and the dynamic loading on initial screw loosening  

PubMed Central

PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at 30° to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for 105 cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (?=0.05). RESULTS Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION The abutment types did not have a significant influence on short term screw loosening. On the other hand, after 105 cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not. PMID:23509006

Kim, Eun-Sook

2013-01-01

194

The role of computed tomography for postoperative evaluation of percutaneous sacroiliac screw fixation and description of a "safe zone".  

PubMed

We sought to determine whether computed tomography (CT) is an accurate tool for evaluation of reduction, prediction of neurologic deficit, and evaluation of need for revision surgery in unstable pelvic ring injuries treated with percutaneous sacroiliac (SI) screw fixation and whether any neural foramen penetration violation is safe. Using medical records and radiographic data, we retrospectively evaluated 46 patients with 51 fractures or widenings of the SI joint that were surgically treated with percutaneous SI screw fixation, either alone or associated with anterior fixation. Using the Young and Burgess classification, there were 3 vertical shear injuries, 13 lateral compression injuries, 17 anterior-posterior injuries, 7 sacral fractures, and 6 combination or unclassifiable pelvic injuries. Satisfactory reduction was obtained in all cases. All patients had postoperative CT scans, and 23 of 51 screws had some foramen penetration with an average of 3.3 mm (range, 1.4-7.0 mm). After percutaneous screw fixation, 10 of 46 patients had postoperative neurologic deficit, 4 of which were unchanged from preoperative evaluation. Of the 6 patients with new or worsened neurologic deficit, CT showed neural foramen penetration of 2.1 and 7.0 mm in 2 patients. Both patients underwent screw revision, resulting in improved neurologic deficit. The remaining 4 patients did not have foramen penetration; their neurologic function improved, with full return at 6 weeks without screw removal. Neural foramen penetration documented with CT did not correlate with neurologic deficit unless the penetration was greater than 2.7 mm. Postoperative CT showing neural foramen penetration was the cause of revision surgery in 2 of 10 patients with postoperative neurologic deficit after percutaneous SI screw fixation. Based on these findings, we recommend postoperative CT only in those cases where there is new neurologic deficit and screw removal if foramen penetration is greater than 2.1 mm. We also describe a new "safe zone" for screw insertion encompassing the superior 2 mm of the sacral foramen with adequate pelvic reduction. PMID:25379748

Tejwani, Nirmal C; Raskolnikov, Dima; McLaurin, Toni; Takemoto, Richelle

2014-11-01

195

CFD ANALYSIS OF SCREW COMPRESSOR PERFORMANCE  

Microsoft Academic Search

Modern manufacturing methods enable screw compressors to be constructed to such close tolerances that full 3-D numerical calculation of the heat and fluid flow through them is required to obtain the maximum possible improvements in their design. An independent stand-alone CAD-CFD interface program has therefore been developed by the authors in order to generate a numerical grid for this purpose.

Ahmed Kovacevic; Nikola Stosic; Ian K. Smith

196

Intraoperative 3-dimensional imaging (O-arm) for assessment of pedicle screw position: Does it prevent unacceptable screw placement?  

PubMed Central

Background Pedicle screws are biomechanically superior over other spinal fixation devices. When improperly positioned, they lose this advantage and put adjacent structures at risk. Accurate placement is therefore critical. Postoperative computed tomography (CT) scans are the imaging gold standard and have shown malposition rates ranging from 2% to 41%. The O-arm (Medtronic Navigation, Louisville, Colorado) is an intraoperative CT scanner that may allow intervention for malpositioned screws while patients are still in the operating room. However, this has not yet been shown in clinical studies. The primary objective of this study was to assess the usefulness of the O-arm for evaluating pedicle screw position by answering the following question: What is the rate of intraoperative pedicle screw revision brought about by O-arm imaging information? A secondary question was also addressed: What is the rate of unacceptable thoracic and lumbar pedicle screw placement as assessed by intraoperative O-arm imaging? Methods This is a case series of consecutive patients who have undergone spine surgery for which an intraoperative 3-dimensional (3D) CT scan was used to assess pedicle screw position. The study comprised 602 pedicle screws (235 thoracic and 367 lumbar/sacral) placed in 76 patients, and intraoperative 3D (O-arm) imaging was obtained to assess screw position. Action taken at the time of surgery based on imaging information was noted. An independent review of all scans was also conducted, and all screws were graded as either optimal (no breach), acceptable (breach ?2 mm), or unacceptable (breach >2 mm). The rate of pedicle screw revision, as detected by intraoperative 3D CT scan, was determined. Results On the basis of 3D imaging information, 17 of 602 screws (2.8%) in 14 of 76 cases (18.4%) were revised at the time of surgery. On independent review of multiplanar images, 11 screws (1.8%) were found to be unacceptable, 32 (5.3%) were acceptable, and 559 (92.9%) were optimal. All unacceptable screws were revised to an optimal or acceptable position, and an additional 6 acceptable screws were revised to an optimal position. Thus, by the end of the cases, none of the 602 pedicle screws in the 76 surgical procedures was in an unacceptable position. Conclusion The new-generation intraoperative 3D imaging system (O-arm) is a useful tool that allows more accurate assessment of pedicle screw position than plain radiographs or fluoroscopy alone. It prompted intraoperative repositioning of 2.8% of pedicle screws in our series. Most importantly, it allowed identification and revision of all unacceptably placed pedicle screws without the need for reoperation.

Sembrano, Jonathan N.; Polly, David W.; Ledonio, Charles Gerald T.; Santos, Edward Rainier G.

2012-01-01

197

Examination of the suitability of alpha-tocopherol as a stabilizer for ultra-high molecular weight polyethylene used for articulating surfaces in joint endoprostheses.  

PubMed

The lifetime of articulating surfaces in joint endoprostheses made of ultra-high molecular weight polyethylene (UHMW-PE), especially of UHMW-PE-cups of hip-endoprostheses, is usually limited to 10-15 years due to material failure as a result of oxidation of the UHMW-PE in vivo. In this study the suitability of the natural antioxidant alpha-tocopherol (vitamin E) as a stabilizer for UHMW-PE in these applications was investigated. Specimens with 0.1%, 0.2%, 0.4% and 0.8% w/w alpha-tocopherol as well as unstabilized samples were sintered and sterilized with gamma-rays at 25 kGy in accordance with standard processing methods of cups for total hip-endoprostheses. These specimens were aged in pure oxygen at 70 degrees C and 5 bar as well as in aqueous H2O2 at 50 degrees C. The degree of oxidation was observed by means of FTIR-spectroscopy, DSC analysis and mechanical testing. The FTIR-measurements showed that alpha-tocopherol can prolong the lifetime of UHMW-PE in an oxidative environment by a factor of more than 2.5. In the mechanical tests no embrittlement could be observed with the stabilized samples. A comparison with the standard antioxidant system Irganox 1010/Irgafos 168 (Ciba-Geigy, Switzerland) was carried out and revealed that alpha-tocopherol can even exceed the stabilization effect of this widely-used antioxidant system. PMID:15348641

Wolf, C; Krivec, T; Blassnig, J; Lederer, K; Schneider, W

2002-02-01

198

Comparison of Torsional Strengths of Bioabsorbable Screws for Anterior Cruciate Ligament Reconstruction  

Microsoft Academic Search

The goals of this study were to evaluate torsional strength and modes of failure in commercially available bioabsorbable interference screws and to test the effect of screw diameter on torsional strength when screws become jammed during insertion. We tested the Arthrex, BioScrew, Endo-Fix, Phantom, and Sysorb screws, all 20 mm in length. Four major modes of failure were encountered. Analysis

John J. Costi; Andrew J. Kelly; Trevor C. Hearn; David K. Martin

2001-01-01

199

Using resorbable screws for fixation of cortical onlay bone grafts: An in vivo study in rabbits  

Microsoft Academic Search

Purpose: The purpose of this study is to test bioresorbable screws as an alternative to titanium screw graft fixation. When cortical onlay grafts are used, it is necessary to rigidly immobilize them with titanium screws into the recipient site. The screws must be removed before placing implants into this site. Bioresorbable screws may be an alternative to titanium fixation, eliminating

Guillermo E. Chacon; James P. Ellis; John R. Kalmar; Edwin A. McGlumphy

2004-01-01

200

Modeling the Parker instability in a rotating plasma screw pinch  

NASA Astrophysics Data System (ADS)

We analytically and numerically study the analogue of the Parker (magnetic buoyancy) instability in a uniformly rotating plasma screw pinch confined in a cylinder. Uniform plasma rotation is imposed to create a centrifugal acceleration, which mimics the gravity required for the classical Parker instability. The goal of this study is to determine how the Parker instability could be unambiguously identified in a weakly magnetized, rapidly rotating screw pinch, in which the rotation provides an effective gravity and a radially varying azimuthal field is controlled to give conditions for which the plasma is magnetically buoyant to inward motion. We show that an axial magnetic field is also required to circumvent conventional current driven magnetohydrodynamic (MHD) instabilities such as the sausage and kink modes that would obscure the Parker instability. These conditions can be realized in the Madison plasma Couette experiment (MPCX). Simulations are performed using the extended MHD code NIMROD for an isothermal compressible plasma model. Both linear and nonlinear regimes of the instability are studied, and the results obtained for the linear regime are compared with analytical results from a slab geometry. Based on this comparison, it is found that in a cylindrical pinch, the magnetic buoyancy mechanism dominates at relatively large Mach numbers (M > 5), while at low Mach numbers (M < 1), the instability is due to the curvature of magnetic field lines. At intermediate values of Mach number (1 < M < 5), the Coriolis force has a strong stabilizing effect on the plasma. A possible scenario for experimental demonstration of the Parker instability in MPCX is discussed.

Khalzov, I. V.; Brown, B. P.; Katz, N.; Forest, C. B.

2012-02-01

201

Test of an improved oil injected helium screw compressor at Fermilab  

SciTech Connect

Fermilab has tested a modified helium oil injected two-stage Mycom screwcompressor for possible use in the Tevatron. The tests are part of a joint venture with Mycom. Modifications to the compressor include a new modified rotor profile and new generation lubricant which resulted in increased performance and efficiency. The effects of the modifications on shaft-power and isothermal efficiency are included. The results of these tests will determine the practicality of incorporating these modifications to the thirty-four existing screw compressors of the Tevatron.

Martinez, A.; Pallaver, C.B. [Fermi National Accelerator Lab., Batavia, IL (United States)

1994-12-31

202

Intrapelvic Migration of the Lag Screw in Intramedullary Nailing  

PubMed Central

Internal fixation with intramedullary devices has gained popularity for the treatment of intertrochanteric femoral fractures, which are common injuries in the elderly. The most common complications are lag screw cut out from the femoral head and femoral fracture at the distal tip of the nail. We report here a rare complication of postoperative lag screw migration into the pelvis with no trauma. The patient was subsequently treated with lag screw removal and revision surgery with total hip arthroplasty. This case demonstrated that optimal fracture reduction and positioning of the lag screw are the most important surgical steps for decreasing the risk of medial migration of the lag screw. Furthermore, to prevent complications, careful attention should be paid to subsequent steps such as precise insertion of the set screw. PMID:25610680

Toki, Shunichi; Hamada, Daisuke; Yoshioka, Shinji; Tsutsui, Takahiko; Tamaki, Yasuaki; Sairyo, Koichi

2014-01-01

203

Fracture fixation with two locking screws versus three non-locking screws  

PubMed Central

Objectives We aimed to further evaluate the biomechanical characteristics of two locking screws versus three standard bicortical screws in synthetic models of normal and osteoporotic bone. Methods Synthetic tubular bone models representing normal bone density and osteoporotic bone density were used. Artificial fracture gaps of 1 cm were created in each specimen before fixation with one of two constructs: 1) two locking screws using a five-hole locking compression plate (LCP) plate; or 2) three non-locking screws with a seven-hole LCP plate across each side of the fracture gap. The stiffness, maximum displacement, mode of failure and number of cycles to failure were recorded under progressive cyclic torsional and eccentric axial loading. Results Locking plates in normal bone survived 10% fewer cycles to failure during cyclic axial loading, but there was no significant difference in maximum displacement or failure load. Locking plates in osteoporotic bone showed less displacement (p = 0.02), but no significant difference in number of cycles to failure or failure load during cyclic axial loading (p = 0.46 and p = 0.25, respectively). Locking plates in normal bone had lower stiffness and torque during torsion testing (both p = 0.03), but there was no significant difference in rotation (angular displacement) (p = 0.84). Locking plates in osteoporotic bone showed lower torque and rotation (p = 0.008), but there was no significant difference in stiffness during torsion testing (p = 0.69). Conclusions The mechanical performance of locking plate constructs, using only two screws, is comparable to three non-locking screw constructs in osteoporotic bone. Normal bone loaded with either an axial or torsional moment showed slightly better performance with the non-locking construct. PMID:23610681

Grawe, B.; Le, T.; Williamson, S.; Archdeacon, A.; Zardiackas, L.

2012-01-01

204

Internal fixation of a capitate fracture with Herbert screws.  

PubMed

A case of an isolated, displaced fracture of the capitate is described. This rare carpal injury was treated by internal fixation with two Herbert screws. The fracture united and the patient achieved an excellent range of wrist motion. The Herbert screw is useful in the treatment of displaced fractures of the capitate since the screw maintains reduction, compresses the fracture site, and allows early wrist motion. PMID:2269778

Richards, R R; Paitich, C B; Bell, R S

1990-11-01

205

On Interlayer Stability and High-Cycle Simulator Performance of Diamond-Like Carbon Layers for Articulating Joint Replacements  

PubMed Central

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and ?3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the ?-? tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic. PMID:24921709

Thorwarth, Kerstin; Thorwarth, Götz; Figi, Renato; Weisse, Bernhard; Stiefel, Michael; Hauert, Roland

2014-01-01

206

On interlayer stability and high-cycle simulator performance of diamond-like carbon layers for articulating joint replacements.  

PubMed

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and -3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the ?-? tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic. PMID:24921709

Thorwarth, Kerstin; Thorwarth, Götz; Figi, Renato; Weisse, Bernhard; Stiefel, Michael; Hauert, Roland

2014-01-01

207

Controversies relating to the management of acromioclavicular joint dislocations.  

PubMed

The aim of this review is to address controversies in the management of dislocations of the acromioclavicular joint. Current evidence suggests that operative rather than non-operative treatment of Rockwood grade III dislocations results in better cosmetic and radiological results, similar functional outcomes and longer time off work. Early surgery results in better functional and radiological outcomes with a reduced risk of infection and loss of reduction compared with delayed surgery. Surgical options include acromioclavicular fixation, coracoclavicular fixation and coracoclavicular ligament reconstruction. Although non-controlled studies report promising results for arthroscopic coracoclavicular fixation, there are no comparative studies with open techniques to draw conclusions about the best surgical approach. Non-rigid coracoclavicular fixation with tendon graft or synthetic materials, or rigid acromioclavicular fixation with a hook plate, is preferable to fixation with coracoclavicular screws owing to significant risks of loosening and breakage. The evidence, although limited, also suggests that anatomical ligament reconstruction with autograft or certain synthetic grafts may have better outcomes than non-anatomical transfer of the coracoacromial ligament. It has been suggested that this is due to better restoration horizontal and vertical stability of the joint. Despite the large number of recently published studies, there remains a lack of high-quality evidence, making it difficult to draw firm conclusions regarding these controversial issues. PMID:24293587

Modi, C S; Beazley, J; Zywiel, M G; Lawrence, T M; Veillette, C J H

2013-12-01

208

Posterolateral corner reconstruction using a hamstring allograft and a bioabsorbable tenodesis screw: description of a new surgical technique.  

PubMed

Capsuloligamentous posterolateral corner knee joint deficiencies cause increased anterior cruciate ligament forces during internal knee rotation and increased posterior cruciate ligament forces during external knee rotation. Undiagnosed posterolateral corner knee joint injury in combination with anterior cruciate ligament or posterior cruciate ligament injury can lead to failure of anterior cruciate ligament or posterior cruciate ligament reconstruction. The purpose of this technical note is to present a new posterolateral corner reconstruction technique for treating patients with chronic capsuloligamentous posterolateral corner deficiency. The technique uses a bioabsorbable tenodesis screw and a hamstring allograft to reconstruct the popliteofibular and lateral collateral ligaments. PMID:15243452

Kocabey, Yavuz; Nawab, Akbar; Caborn, David N M; Nyland, John

2004-07-01

209

Biomechanical and histomorphometric study on the bone–screw interface of bioactive ceramic-coated titanium screws  

Microsoft Academic Search

The purpose of this study was to compare the osseointegration of 4 different kinds of bioactive ceramic-coated screws with uncoated screws by biomechanical and histomorphometric analysis.Calcium pyrophosphate (CPP), apatite-wollastonite 1:3 glass ceramic (W3G), apatite-wollastonite 1:1 glass ceramic (WAG) and bioactive CaO–SiO2–B2O3 glass ceramic (CSG) coatings were prepared and coated by the dipping method. Coated and uncoated titanium screws were inserted

Jae Hyup Lee; Hyun-Seung Ryu; Dong-Soo Lee; Kug Sun Hong; Bong-Soon Chang; Choon-Ki Lee

2005-01-01

210

Arthroscopic meniscal repair with an absorbable screw: results and surgical technique  

Microsoft Academic Search

The results of a new method for arthroscopic all-inside meniscus repair using a biodegradable cannulated screw (Clearfix meniscal screw) were assessed in a medium-term follow-up prospective study. The Clearfix meniscal screw system consists of delivery cannulae, screw driver, and screw implants. After tear debridement, a screw is located on the driver and passed through the cannula to the insertion site,

Michael E. Hantes; Elias S. Kotsovolos; Dimitrios S. Mastrokalos; Joerg Ammenwerth; Hans H. Paessler

2005-01-01

211

Rotary screw compressor lubricants. [synthetic lubricant  

SciTech Connect

A method is claimed for synthetic lubricants comprising 15 to 45 weight percent of an ester of a hindered polyhydric alcohol having 3 to 8 hydroxy groups and 5 to 10 carbon atoms with one or more alkanoic acids having 4 to 18 carbon atoms blended with 85 to 55 weight percent of one or more polyether polyol having an number average molecular weight from about 400 to 5000. The blends are compounded with antioxidants, corrosion inhibitors, and metal deactivators to produce a superior lubricant for rotary screw compressors that has a long life.

Carswell, R.; Mcgraw, P.W.

1981-11-24

212

Arthrodesis of the first metatarsophalangeal joint.  

PubMed

Arthrodesis of the first metatarsophalangeal joint is indicated in patients with symptomatic arthrodesis or advanced hallux valgus deformities that are unresponsive to nonsurgical treatment. Several fixation techniques have been described, including intefragmentary compression screws and/or dorsal plate fixation. Using these modern fixation techniques, the rate of fusion is between 94% to 98%, with high patient satisfaction. Appropriate positioning of the fusion is important for satisfactory outcome. PMID:15948454

Marks, Richard M

2005-01-01

213

Tibial Fixation of Bone-Patellar Tendon-Bone Grafts in Anterior Cruciate Ligament ReconstructionA Cadaveric Study of Bovine Bone Screw and Biodegradable Interference Screw  

Microsoft Academic Search

Background: The use of interference screw fixation for bone-patellar tendon-bone grafts in anterior cruciate ligament fixation is well established. No previous study has compared bovine bone screws and biodegradable interference screws or demonstrated their efficacy for requirements associated with early rehabilitation.Hypothesis: There is no difference in tension loss and pull-out strength between bovine bone screws and biodegradable interference screws.Study Design:

Naiquan Zheng; Chad T. Price; Peter A. Indelicato; Bo Gao

2008-01-01

214

Assembly means for standardized mechanical joint for pipeline appurtenances  

Microsoft Academic Search

This patent describes an improvement in the standardized mechanical joint connection for use on waterworks or gas pipeline appurtenances wherein the shape or dimensions of the body of the appurtenances preclude the insertion and tightening of the standardized T-bolts. The improvement comprises: a. a screw having an externally threaded cylindrical portion, an hexagonally shaped head on one end of the

H. Jr

1987-01-01

215

Periodic Stresses in Gyroscopic Bodies, with Applications to Air Screws  

NASA Technical Reports Server (NTRS)

Report discusses periodic stresses in gyroscopic bodies with applications to air screws caused by particle mass. Report concludes that all modern air screws obey the laws found for plane groups of particles. In particular the two-bladers exert on the shaft a rhythmic gyroscopic torque; the multibladers a steady one; both easily calculable for any given conditions of motion and mass distribution.

Zahm, A F

1918-01-01

216

An integrated model for the performance calculation of Screw Machines  

Microsoft Academic Search

There is a need to develop improved analytical procedures in order to improve performance, reduce noise emission and reduce the manufacturing costs of screw compressors. Most mathematical models, used by industry for screw compressor performance estimation and optimisation, are based on quasi one dimensional calculation of the governing flow equations in a control volume. Despite being fast and accurate for

Ahmed Kovacevic; Elvedin Mujic; Nikola Stosic; Ian K. Smith

217

Performance Analysis of Oil Injected Twin Screw Compressor  

Microsoft Academic Search

Oil injected twin-screw air compressors are widely used for medium pressure applications in cryogenic industries. Conversion of these compressors for helium applications is in great demand due to their inherent advantages. A mathematical model of an oil injected twin-screw compressor has been constructed basing on the laws of perfect gas and standard thermodynamic relations to evaluate compressor efficiencies. The complete

N. Seshaiah; Subrata Kr; Ranjit Kr; Sunil Kr

2006-01-01

218

Fatigue strength of common tibial intramedullary nail distal locking screws  

Microsoft Academic Search

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

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

2009-01-01

219

Fracture mechanisms of retrieved titanium screw thread in dental implant  

Microsoft Academic Search

Titanium and its alloy are increasingly attracting attention for use as biomaterials. However, delayed fracture of titanium dental implants has been reported, and factors affecting the acceleration of corrosion and fatigue have to be determined. The fractured surface of a retrieved titanium screw and metallurgical structures of a dental implant system were analyzed. The outer surface of the retrieved screw

Ken’ichi Yokoyama; Tetsuo Ichikawa; Hiroki Murakami; Youji Miyamoto; Kenzo Asaoka

2002-01-01

220

Scaphoid Osteosynthesis: Early Experience with the Herbert Bone Screw  

Microsoft Academic Search

The results of our first fourteen patients with fractured scaphoids treated with the Herbert bone screw have been disappointing. Six have failed to unite. The operation is technically demanding and there is a high incidence of malpositioning of the screw which correlates with failure to achieve union. This is predictable from initial radiographs and peroperative radiology is advised. The osteosynthesis

D. J. PRING; E. B. HARTLEY; D. J. WILLIAMS

1987-01-01

221

The Herbert Bone Screw: A Ten Year Perspective  

Microsoft Academic Search

It is now over ten years since the Herbert bone screw was first released in Australia. In 1984, Herbert and Fisher first published their experience with the use of this new bone screw in the management of scaphoid fractures. Since that time, there has been a growing interest in the technique and over 60 articles have appeared in the English

T. J. HERBERT; W. E. FISHER; A. W. LEICESTER

1992-01-01

222

Screw dislocations in GaN  

SciTech Connect

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.

Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack; O'Keefe, Michael A.

2002-02-15

223

Performance of Screw Compressor for Small-Capacity Helium Refrigerators  

NASA Astrophysics Data System (ADS)

A helium compressor is one of the important components comprising a cryogenic refrigerator. The purpous of this investigation is to develop a new small-capacity helium screw compressor. The performance of a single-stage compressor at high compression ratio and the cooling performance of the compressor are investigated. A semi-hermetic screw compressor with new profile screw rotors, with which high performance can be obtained, is utilized in this investigation. Lubricating oil is applied to cool the compressor motor and the compressed gas. As a result, an overall isentropic efficiency of 80% is obtained when helium is compressed to a compression ratio of 19.8 with a single-stage screw compressor. At the same time, the temperature of a compressor motor and discharge gas can be maintained at low levels. Therefore, it is found that a single-stage screw compressor can compress helium to high compression ratio.

Urashin, Masayuki; Matsubara, Katsumi; Izunaga, Yasushi

224

Intraosseous screw fixation of anterior cervical graft construct after diskectomy.  

PubMed

This article describes a new technique of intraosseous screw fixation of the cervical spine, as well as a retrospective review of 27 patients who had anterior cervical interbody fusion after diskectomy and fixation with one intraosseous Herbert screw, with a minimum follow-up of 1 year. The study included 19 men and eight women. There were no neurologic complications at final follow-up evaluation. All patients had radiographic evidence of fusion. No screw breakage, back-out, or dislodgement occurred. Optimal intraoperative radiographic evaluation for accurate intraosseous screw placement is recommended. The use of intraosseous screw fixation is a useful addition to the armamentarium of the spine surgeon when fixation of anterior cervical graft after diskectomy is required. One hundred percent rate of union and prevention of complications related to the currently used anterior fixation systems are the major advantages of this method. PMID:8003829

Chang, K W; Lin, G Z; Liu, Y W; Suen, K L; Liang, P L

1994-04-01

225

Olecranon anatomy: Use of a novel proximal interlocking screw for intramedullary nailing, a cadaver study  

PubMed Central

AIM: To define the optimum safe angle of use for an eccentrically aligned proximal interlocking screw (PIS) for intramedullary nailing (IMN). METHODS: Thirty-six dry cadaver ulnas were split into two equal pieces sagitally. The following points were identified for each ulna: the deepest point of the incisura olecrani (A), the point where perpendicular lines from A and the ideal IMN entry point (D) are intersected (C) and a point at 3.5 mm (2 mm safety distance from articular surface + 1.5 mm radius of PIS) posterior from point A (B). We calculated the angle of screws inserted from point D through to point B in relation to D-C and B-C. In addition, an eccentrically aligned screw was inserted at a standard 20° through the anterior cortex of the ulna in each bone and the articular surface was observed macroscopically for any damage. RESULTS: The mean A-C distance was 9.6 mm (mean ± SD, 9.600 ± 0.763 mm), A-B distance was 3.5 mm, C-D distance was 12.500 mm (12.500 ± 1.371 mm) and the mean angle was 25.9° (25.9° ± 2.0°). Lack of articular damage was confirmed macroscopically in all bones after the 20.0° eccentrically aligned screws were inserted. Intramedullary nail fixation systems have well known biological and biomechanical advantages for osteosynthesis. However, as well as these well-known advantages, IMN fixation of the ulna has some limitations. Some important limitations are related to the proximal interlocking of the ulna nail. The location of the PIS itself limits the indications for which intramedullary systems can be selected as an implant for the ulna. The new PIS design, where the PIS is aligned 20°eccentrically to the nail body, allows fixing of fractures even at the level of the olecranon without disturbing the joint. It also allows the eccentrically aligned screw to be inserted in any direction except through the proximal radio-ulnar joint. Taking into consideration our results, we now use a 20° eccentrically aligned PIS for all ulnas. In our results, the angle required to insert the PIS was less than 20° for only one bone. However, 0.7° difference corresponds to placement of the screw only 0.2 mm closer to the articular surface. As we assume 2.0 mm to be a safe distance, a placement of the screw 0.2 mm closer to the articular surface may not produce any clinical symptoms. CONCLUSION: The new PIS may give us the opportunity to interlock IMN without articular damage and confirmation by fluoroscopy if the nail is manufactured with a PIS aligned at a 20.0° fixed angle in relation to the IMN. PMID:23878781

Küçükdurmaz, Fatih; Saglam, Necdet; A??r, ?smail; Sen, Cengiz; Akp?nar, Fuat

2013-01-01

226

C2 Pars/Pedicle Screws in Management of Craniocervical and Upper Cervical Instability  

PubMed Central

Study Design A retrospective study. Purpose To evaluate the efficacy and the safety of craniocervical and upper cervical stabilization by using C2 pars/pedicle screw fixations. Overview of Literature The management of craniocervical and upper cervical instability has progressed over the past two decades due to good achievements in the instrumentation and the increased awareness on spinal anatomy and biomechanics. However, there is insufficient studies or solid conclusions on this topic, thus, we tried to investigate and present our findings. Methods Twenty-two patients were operated upon and were followed up from March 2008 to October 2010. One patient had craniocervical instability (post-surgical), 15 patients had atlantoaxial instability of different etiologies (trauma, tumors, inflammatory and degenerative) and 6 patients had hangman fractures. Patients' ages ranged from 18 to 52 years old. with 5 female patients and 17 male patients. Results Radiological follow ups performed immediately post-operation showed good screw positioning and complete reductions in nearly all the cases. All patients were followed up for more than one year. Sound fusions were observed among all patients. Conclusions The use of pars/pedicle screws is a very effective, sound, safe and easy surgical modality for treating craniocervical, atlantoaxial and upper cervical instabilities. Increasing studies for the biomechanics of this important region and longer periods of follow-ups are necessary to document the usefulness of this modality when treating such patients. PMID:24761197

2014-01-01

227

Effects of edge and screw dislocations on optical properties of Wurtzite GaN  

NASA Astrophysics Data System (ADS)

The wide bandgap and high temperature stability of GaN makes it a desirable material for applications such as blue light-emitting diodes, blue lasers, and high-power transistors. Despite these advantages, the large lattice mismatch in most epitaxial GaN leads to a high density of dislocations, on the order of 10^9cm-2 for edge dislocations and 10^8cm-2 for screw dislocations in WZ GaN. Edge dislocations are electron acceptors and take on a negative charge. Open-core screw dislocations are essentially voids, or nanopipes, in the material. The presence of these defects, plus the strain field associated with each dislocation type, change the density of states and reduce the PL intensity in typical epitaxial GaN device layers. In the present work, the effects of edge and screw dislocations in WZ GaN have been studied computationally as a function of dislocation density. Spectral properties are determined by solving a 6x6 multiband kp Hamiltonian in three-dimensions using a real-space finite element method. Results compare favorably to available experimental data.

You, Jeong Ho; Johnson, H. T.

2006-03-01

228

Effect of occipitocervical fusion with screw-rod system for upper cervical spine tumor  

PubMed Central

Background Craniospinal junction tumors are rare but severe lesions. Surgical stabilization has been established to be an ideal treatment for upper cervical tumor pathology. The purpose of this study was to evaluate the effect of a screw-rod system for occipitocervical fusion. Methods A total of 24 cases with C1 and C2 cervical tumor underwent occipitocervical fusion with Vertex screw-rod internal fixation from January 2005 to December 2012. Preoperative X-ray and MRI examinations were performed on all patients before the operation, after the operation, and during last follow-up. The JOA score was used to assess neurological function pre and postoperatively. Results All the patients were followed up for 6 to 42 months with an average of 24 months. The result of X-ray showed that bony fusion was successful in 18 patients at 3 months and 6 patients at 6 months of follow-ups. There was no deterioration of spinal cord injury. The JOA Scores of neurological function increased significantly. Conclusion The screw-rod system offers strong fixation and good fusion for occipitocervical fusion. It is an effective and reliable method for reconstruction of upper cervical spine tumor. PMID:24884456

2014-01-01

229

Cannulated Screw Fixation of Jones Fifth Metatarsal Fractures: A Comparison of Titanium and Stainless Steel Screw Fixation  

Microsoft Academic Search

The classic Jones fracture involves the fifth metatarsal at the level of the proximal diaphyseal-metaphyseal junction. The mainstay of surgical treatment for the Jones fracture is intramedullary screw fixation. There is no consensus of the type or material of screw that should be used. The purpose of this retrospective cohort study was to test the hypothesis that there is no

J. George DeVries; Daniel J. Cuttica; Christopher F. Hyer

2011-01-01

230

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)

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.

Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

2004-01-01

231

Effect of DDGS, Moisture Content, and Screw Speed on the Physical Properties of Extrudates in Single Screw Extrusion  

Technology Transfer Automated Retrieval System (TEKTRAN)

Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% (wb) DDGS along with soy flour, corn flour, fish meal, mineral and vitamin mix, with the net protein adjusted to 28% (wb) for all blends, were extruded in a single screw laboratory-scale extruder at screw speeds of 100, 130, ...

232

A computational biomechanical investigation of posterior dynamic instrumentation: combination of dynamic rod and hinged (dynamic) screw.  

PubMed

Currently, rigid fixation systems are the gold standard for degenerative disk disease treatment. Dynamic fixation systems have been proposed as alternatives for the treatment of a variety of spinal disorders. These systems address the main drawbacks of traditional rigid fixation systems, such as adjacent segment degeneration and instrumentation failure. Pedicle-screw-based dynamic stabilization (PDS) is one type of these alternative systems. The aim of this study was to simulate the biomechanical effect of a novel posterior dynamic stabilization system, which is comprised of dynamic (hinged) screws interconnected with a coiled, spring-based dynamic rod (DSDR), and compare it to semirigid (DSRR and RSRR) and rigid stabilization (RSRR) systems. A validated finite element (FE) model of L1-S1 was used to quantify the biomechanical parameters of the spine, such as range of motion, intradiskal pressure, stresses and facet loads after single-level instrumentation with different posterior stabilization systems. The results obtained from in vitro experimental intact and instrumented spines were used to validate the FE model, and the validated model was then used to compare the biomechanical effects of different fixation and stabilization constructs with intact under a hybrid loading protocol. The segmental motion at L4-L5 increased by 9.5% and 16.3% in flexion and left rotation, respectively, in DSDR with respect to the intact spine, whereas it was reduced by 6.4% and 10.9% in extension and left-bending loads, respectively. After instrumentation-induced intradiskal pressure at adjacent segments, L3-L4 and L5-S1 became less than the intact in dynamic rod constructs (DSDR and RSDR) except in the RSDR model in extension where the motion was higher than intact by 9.7% at L3-L4 and 11.3% at L5-S1. The facet loads were insignificant, not exceeding 12N in any of the instrumented cases in flexion. In extension, the facet load in DSDR case was similar to that in intact spine. The dynamic rod constructions (DSDR and RSDR) led to a lesser peak stress at screws compared with rigid rod constructions (DSRR and RSRR) in all loading cases. A dynamic construct consisting of a dynamic rod and a dynamic screw did protect the adjacent level from excessive motion. PMID:24599026

Erbulut, Deniz U; Kiapour, Ali; Oktenoglu, Tunc; Ozer, Ali F; Goel, Vijay K

2014-05-01

233

Metal artifacts from titanium and steel screws in CT, 1.5T and 3T MR images of the tibial Pilon: a quantitative assessment in 3D.  

PubMed

Radiographs are commonly used to assess articular reduction of the distal tibia (pilon) fractures postoperatively, but may reveal malreductions inaccurately. While magnetic resonance imaging (MRI) and computed tomography (CT) are potential three-dimensional (3D) alternatives they generate metal-related artifacts. This study aims to quantify the artifact size from orthopaedic screws using CT, 1.5T and 3T MRI data. Three screws were inserted into one intact human cadaver ankle specimen proximal to and along the distal articular surface, then CT, 1.5T and 3T MRI scanned. Four types of screws were investigated: titanium alloy (TA), stainless steel (SS) (Ø =3.5 mm), cannulated TA (CTA) and cannulated SS (CSS) (Ø =4.0 mm, Ø empty core =2.6 mm). 3D artifact models were reconstructed using adaptive thresholding. The artifact size was measured by calculating the perpendicular distance from the central screw axis to the boundary of the artifact in four anatomical directions with respect to the distal tibia. The artifact sizes (in the order of TA, SS, CTA and CSS) from CT were 2.0, 2.6, 1.6 and 2.0 mm; from 1.5T MRI they were 3.7, 10.9, 2.9, and 9 mm; and 3T MRI they were 4.4, 15.3, 3.8, and 11.6 mm respectively. Therefore, CT can be used as long as the screws are at a safe distance of about 2 mm from the articular surface. MRI can be used if the screws are at least 3 mm away from the articular surface except for SS and CSS. Artifacts from steel screws were too large thus obstructed the pilon from being visualised in MRI. Significant differences (P<0.05) were found in the size of artifacts between all imaging modalities, screw types and material types, except 1.5T versus 3T MRI for the SS screws (P=0.063). CTA screws near the joint surface can improve postoperative assessment in CT and MRI. MRI presents a favourable non-ionising alternative when using titanium hardware. Since these factors may influence the quality of postoperative assessment, potential improvements in operative techniques should be considered. PMID:24914417

Radzi, Shairah; Cowin, Gary; Robinson, Mark; Pratap, Jit; Volp, Andrew; Schuetz, Michael A; Schmutz, Beat

2014-06-01

234

Hip joints  

NSDL National Science Digital Library

The human hips are an example of a ball-and-socket joint. Ball-and-socket joints have the ability to rotate in a circular motion. The joint where the arm connects to the shoulder is also a type of ball-and-socket joint.

Connie Raab (National Institutes of Health;)

2006-05-17

235

Salvaging the Pullout Strength of Stripped Screws in Osteoporotic Bone  

PubMed Central

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

Pechon, Pierre H. M.; Mears, Simon C.; Langdale, Evan R.; Belkoff, Stephen M.

2013-01-01

236

Salvaging the pullout strength of stripped screws in osteoporotic bone.  

PubMed

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

Pechon, Pierre H M; Mears, Simon C; Langdale, Evan R; Belkoff, Stephen M

2013-06-01

237

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

PubMed Central

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

2014-01-01

238

SCREW COMPRESSOR CHARACTERISTICS FOR HELIUM REFRIGERATION SYSTEMS  

SciTech Connect

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. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss

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

2008-03-01

239

Screw Compressor Characteristics for Helium Refrigeration Systems  

NASA Astrophysics Data System (ADS)

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. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss mechanisms, as well as to implement practical solutions.

Ganni, V.; Knudsen, P.; Creel, J.; Arenius, D.; Casagrande, F.; Howell, M.

2008-03-01

240

Joints in a Cornstarch Analog  

NSDL National Science Digital Library

Joints are very important to problems in applied geology (fluid flow, slope stability), but three-dimensional exposures of simple joint sets are not readily accessible from my campus. I developed this exercise based on the experiments of Miller (2001) to give students hands-on practice describing and interpreting joints. For the exercise, I prepare a cornstarch-water mixture a few days in advance and pour it into plastic petri dishes. I add a "flaw" to each dish (typically a small pebble). As the cornstarch dries, vertical joints develop. In class, each group of 3-4 students is provided a petri dish of desiccated cornstarch. Students are asked to draw a map of the joints, paying particular attention to intersection angles. (The joints curve to intersect at 90 degrees.) They determine relative ages of the joints using abutting relationships. (Typically 3-6 generations of joints.) Students next dissect the sample and describe the surface textures of the larger joints and the location of the flaw. The cornstarch produces beautiful plumose structure (hackles). Students then interpret the joint propagation direction from the surface textures, and note the origin of the joint. (Typically, a first- or second-generation joint initiates at the flaw.) Students discuss the role of flaws in the initiation of joints in their groups.

Crider, Juliet

241

Interference screw position and hamstring graft location for anterior cruciate ligament reconstruction  

Microsoft Academic Search

Anterior cruciate ligament reconstruction with hamstring tendon graft and interference screw fixation has recently been considered. Concerns for the use of interference screws with soft tissue grafts include damage to the graft during screw insertion, decreased fixation strength, and a decrease in the bone-tendon contact area for healing within the tunnel when the screw is placed in an eccentric position.

PT Simonian; PS Sussmann; TH Baldini; HC Crockett; TL Wickiewicz

1998-01-01

242

Manufacture of composite screw rotors for air compressors by RTM process  

Microsoft Academic Search

Screw rotors, the key parts of screw compressors, are widely used in compressing air and refrigerant due to their high productivity, compact size, low noise and easy maintenance. In general, a screw compressor unit is composed of female and male rotors of complex geometric shape. The manufacturing cost and time of the screw rotors are high because the complicated helical

Jung Do Suh; Dai Gil Lee

2001-01-01

243

2D-fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries - a case series  

Microsoft Academic Search

BACKGROUND: Screw fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system. METHODS: Between August 2004 and December

Florian Gras; Ivan Marintschev; Arne Wilharm; Kajetan Klos; Thomas Mückley; Gunther O Hofmann

2010-01-01

244

Computer assisted screw insertion into real 3D rapid prototyping pelvis models  

Microsoft Academic Search

Objective. Show the use of computer navigation in exact screw positioning in the different pelvic bones.Background. Computer assisted pedicle screw insertion in the spine is an established procedure. Screw fixation is also used in highly difficult pelvic and hip surgery (arthroplasty revision surgery and tumor surgery).Design. Insert as long screws as possible with computer navigation into the different bones of

P Peters; F Langlotz; L.-P Nolte

2002-01-01

245

A novel technique for accurate Poller (blocking) screw placement.  

PubMed

Achieving good results with intramedullary nailing of oblique long bone fractures at the metaphyseal-diaphyseal junction can be difficult. There is a strong tendency for axial displacement and an association with characteristic malalignment of the short fragment. Poller or blocking screws have been shown to be effective in aiding fracture reduction. While several papers describe methods for screw placement, these are confusing to understand, difficult to follow in clinical practice and not always applicable. Here we describe a new, simple, reproducible and easy to use method for ensuring accurate Poller screw placement, in order to maximise the benefits of their use and achieve good overall results. PMID:24629702

Hannah, Andrew; Aboelmagd, Tariq; Yip, Grace; Hull, Peter

2014-06-01

246

Intersection of screw dislocations in fcc crystals during torsional deformation  

NASA Astrophysics Data System (ADS)

Dislocation reactions, including dislocation intersections during various processes in crystals, play an important and often crucial role. This is most pronounced during plastic deformation of crystalline solids, which attracts particular interest from researchers. Intersection of screw dislocations in fcc crystals during their deformation by uniaxial tension and compression was studied by A. Cottrell [1]. It was shown that the intersection of similar screw dislocations moving toward each other results in the formation of interstitial thresholds on them; in the case of intersection of opposite screw dislocations, vacancy thresholds are formed on them.

Myshlyaev, M. M.

2012-03-01

247

[Shape-memory osteosynthesis for trapeziometacarpal joint arthrodesis].  

PubMed

PURPOSE OF THE STUDY Arthrodesis of the trapeziometacarpal joint is the method of choice in the treatment of degenerative arthritis of this joint. This procedure was indicated most frequently in middle-age patients doing hard manual labor. Methods for achieving a solid fusion of the trapeziometacarpal joint are known and often reported in the literature. Frequently, they are associated with some failure rate, particularly as concerns bone union. Our study presents a simple and effective method verifid in cadaver specimens and then currently used at our department. MATERIAL AnD METHODS The procedure for arthrodesis of the trapeziometacarpal joint was verifid fist in fied wrist and hand specimens at the Institute of Anatomy, 1 st Faculty of Medicine, Charles University in Prague. If the original shape of the basal thumb joint between the trapezium and the metacarpal is maintained, it allows for correct reduction and subsequent arthrodesis in a required position. In patients, surgical treatment included the use of implants, two DePuy shape-memory staples, which facilitate suffiient fragment compression and provide stable fiation. The staples were inserted in pre-drilled and gauged tunnels in the body of the trapezium and in the proximal metaphysis of the fist metacarpal. RESULTS Between 2011 and 2014, the procedure was used in 14 patients diagnosed with primary arthritis of the trapeziometacarpal joint. The group comprised nine women and fie men, the average age was 52 years and the range was 44 to 69 years. Surgery was most frequently carried out on the dominant upper extremity (85%); there was no bilateral surgery. The average follow-up was 18.3 months (range, 5 to 39 months). Solid fusion was recorded at 7 weeks after surgery in all patients except for the one still treated at the time of this paper submission. All patients were free of pain, ten reported satisfaction with grip strength and hand function, the rest would have preferred improvement in fie motor skills of the thumb. All of them found the cosmetic appearance of the hand satisfactory.. DISCUSSIOn The methods generally used for trapeziometacarpal joint arthrodesis are reported to carry some risk of pseudarthrosis development. A lot of modifiations have been described, from conventional procedures using AO lag screws or Kirschner wires to up-to-date plate systems involving angle-stable fiation. Total fusion of the trapeziometacarpal joint is disputable in patients with rheumatoid arthritis from the technical point of view as well as the relevance of indication criteria. Some authors consider this procedure a contraindication for patients with rheumatoid arthritis. The use of joint replacement in treating trapeziometacarpal joint arthritis is another complex issue. COnCLUSIOnS An arthrodesis of the trapeziometacarpal joint based on careful assessment of indication criteria proved to be a simple, effective and low-cost method of stable osteosynthesis that provided good conditions for solid fusion of the trapezium with the base of the fist metacarpal. It allowed for suffiient abduction and opposition of the thumb, thus permitting satisfactory hand grip strength and full involvement in everyday life activities and occupations. It provided stability of the thumb, its painless movement and good cosmetic looks. key words: rhizarthrosis, osteoarthritis, arthrodesis, shape-memory staple, trapeziometacarpal joint. PMID:25514342

Pech, J; Veigl, D; Hromádka, R; Dobiáš, J; Zatrapa, T

2014-01-01

248

Exercise and the Knee Joint.  

ERIC Educational Resources Information Center

This report by the President's Council on Physical Fitness and Sports examines the effects of various forms of physical exercise on the knee joint which, because of its vulnerability, is especially subject to injury. Discussion centers around the physical characteristics of the joint, commonly used measurements for determining knee stability,…

Clarke, H. Harrison, Ed.

1976-01-01

249

Biocompatibility studies of titanium-based alloy pedicle screw and rod system  

Microsoft Academic Search

Background context: Few histological studies of pedicle screw and rod systems have been done, and spinal surgery with pedicle screw and rod system is increasing.Purpose: To know the biocompatibility of pedicle screw and rod systems histologically. Study design\\/setting: Titanium-based alloy pedicle screws were removed from 20 patients. Histological studies of the tissue response to the screws were performed by light

Kazuhiro Yamaguchi; Hiroaki Konishi; Shinichiro Hara; Yoshinori Motomura

2001-01-01

250

Wet-gas compression in twin-screw multiphase pumps  

E-print Network

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...

Chan, Evan

2009-05-15

251

Probabilistic model and experimental identification of screw-attachment in  

E-print Network

[cardboard-plaster-cardboard (CPC) multilayer] screwed with a metal frame on both sides, and are made of a body of plaster stickled with two sheets of cardboard on both sides. They are linked with the metal

Paris-Sud XI, Université de

252

Outcome of Pedicle Screw Fixation and Monosegmental Fusion in Patients with Fresh Thoracolumbar Fractures  

PubMed Central

Study Design Prospective clinical study. Purpose The present prospective study aims to evaluate the clinical, radiological, and functional and quality of life outcomes in patients with fresh thoracolumbar fractures managed by posterior instrumentation of the spine, using pedicle screw fixation and monosegmental fusion. Overview of Literature The goals of treatment in thoracolumbar fractures are restoring vertebral column stability and obtaining spinal canal decompression, leading to early mobilization of the patient. Methods Sixty-six patients (46 males and 20 females) of thoracolumbar fractures with neurological deficit were stabilized with pedicle screw fixation and monosegmental fusion. Clinical, radiological and functional outcomes were evaluated. Results The mean preoperative values of Sagittal index, and compression percentage of the height of the fractured vertebra were 22.75° and 46.73, respectively, improved (statistically significant) to 12.39°, and 24.91, postoperatively. The loss of correction of these values at one year follow-up was not statistically significant. The mean preoperative canal compromise (%) improved from 65.22±17.61 to 10.06±5.31 at one year follow-up. There was a mean improvement in the grade of 1.03 in neurological status from the preoperative to final follow-up at one year. Average Denis work scale index was 4.1. Average Denis pain scale index was 2.5. Average WHOQOL-BREF showed reduced quality of life in these patients. Patients of early surgery group (operated within 7 days of injury) had a greater mean improvement of neurological grade, radiological and functional outcomes than those in the late surgery group, but it was not statistically significant. Conclusions Posterior surgical instrumentation using pedicle screws with posterolateral fusion is safe, reliable and effective method in the management of fresh thoracolumbar fractures. Fusion helps to decrease the postoperative correction loss of radiological parameters. There is no correlation between radiographic corrections achieved for deformities and functional outcome and quality of life post spinal cord injury. PMID:24967043

Rohilla, Rajesh Kumar; Kamboj, Kulbhushan; Magu, Narender Kumar; Kaur, Kiranpreet

2014-01-01

253

Causes and treatments of lag screw's cut out after intramedullary nailing osteosinthesis for trochanteric fractures.  

PubMed

Background. Superior cut-out of a lag screw remains a serious complication in the treatment of trochanteric or subtrochanteric fractures and it is related to many factors: the type of fracture, osteoporosis and the stability of fracture reduction. Little is known about the outcome after revision surgery for complications of the gamma nail. We assessed the outcome in patients who had revision surgery because of lag screw's cut out after gamma nailing for a trochanteric fracture.Material and Method. We present a study of 20 consecutive patients who underwent treatment after 20 cut-out of the lag screw ?xation of a trochanteric fracture with Gamma Locking Nail from September 2004 to November 2010. In 16 patients hip prothesis was performed, in 1 the removal of the implant and in 3 the reosteosynthesis. We reviewed 13 patients: 10 total hip arthroplasty, 2 endoprothesis and 1 reosteosynthesis of nail and lag screw (mean follow up: 26 months, mean age: 73 years old), 7 patients died. Patients were reviewed retrospectively by an independent observer. Clinical evaluation was performed, Oxford score and Harris Hip score were measured. X-Ray examination was performed after a minimum of 12 months of follow up.Results. Mean Harris Hip Score mean was 67 and mean Oxford score was 32 in hip prothesis group (12 patients). We had several complications, Implant-related complications were: 2 ipometria > 2cm, 2 recurrent hip arthroplasty dislocations (1 reoperated), 4 persistent thigh pain. In only 4 patients none complications were observed. Another patient,  who had been subjected to reosteosinthesis, obtained better results (HHS:95, Oxford score:45) but with a 2 cm ipometria and occasional pain in the thigh.Conclusion. Cut out after gamma nail is consequent to biological or mechanical causes. Treatment of this complication is hip prosthesis (parzial or total hip arthroplasty), reosteosynthesis of the lag screw and/or the nail and the removal of the implant. Conversion to total/parzial hip arthroplasty may be a demanding operation with a higher complication rate respect to the standard, while reosteosynthesis is possible in selected patients and early cutting out. PMID:25245649

Gazzotti, Gabriele; Matino, Giovanni; Tsatsis, Christos; Sacchetti, GianLuigi; Baudi, Paolo; Catani, Fabio

2014-01-01

254

Volar Percutaneous Screw Fixation for Scaphoid Waist Delayed Union  

Microsoft Academic Search

Volar percutaneous cannulated screw fixation of acute scaphoid waist fractures reportedly produces high rates of healing and\\u000a early return to work, but the method has not been reported for treating scaphoid waist delayed unions. We therefore report\\u000a the surgical results of percutaneous screw fixation in scaphoid waist delayed union in 12 patients. All patients were male\\u000a with an average age

Jae Kwang Kim; Jong Oh Kim; Seung Yup Lee

2010-01-01

255

Minimal Surfaces, Screw Dislocations, and Twist Grain Boundaries  

Microsoft Academic Search

Large twist-angle grain boundaries in layered structures are often described\\u000aby Scherk's first surface whereas small twist-angle grain boundaries are\\u000ausually described in terms of an array of screw dislocations. We show that\\u000athere is no essential distinction between these two descriptions and that, in\\u000aparticular, their comparative energetics depends crucially on the core\\u000astructure of their screw-dislocation topological defects.

Randall D. Kamien; T. C. Lubensky

1999-01-01

256

Screw dislocation driven growth of nanomaterials.  

PubMed

Nanoscience and nanotechnology impact our lives in many ways, from electronic and photonic devices to biosensors. They also hold the promise of tackling the renewable energy challenges facing us. However, one limiting scientific challenge is the effective and efficient bottom-up synthesis of nanomaterials. We can approach this core challenge in nanoscience and nanotechnology from two perspectives: (a) how to controllably grow high-quality nanomaterials with desired dimensions, morphologies, and material compositions and (b) how to produce them in a large quantity at reasonable cost. Because many chemical and physical properties of nanomaterials are size- and shape-dependent, rational syntheses of nanomaterials to achieve desirable dimensionalities and morphologies are essential to exploit their utilities. In this Account, we show that the dislocation-driven growth mechanism, where screw dislocation defects provide self-perpetuating growth steps to enable the anisotropic growth of various nanomaterials at low supersaturation, can be a powerful and versatile synthetic method for a wide variety of nanomaterials. Despite significant progress in the last two decades, nanomaterial synthesis has often remained an "art", and except for a few well-studied model systems, the growth mechanisms of many anisotropic nanostructures remain poorly understood. We strive to go beyond the empirical science ("cook-and-look") and adopt a fundamental and mechanistic perspective to the anisotropic growth of nanomaterials by first understanding the kinetics of the crystal growth process. Since most functional nanomaterials are in single-crystal form, insights from the classical crystal growth theories are crucial. We pay attention to how screw dislocations impact the growth kinetics along different crystallographic directions and how the strain energy of defected crystals influences their equilibrium shapes. Furthermore, such inquiries are supported by detailed structural investigation to identify the evidence of dislocations. The dislocation-driven growth mechanism not only can unify the various explanations behind a wide variety of exotic nanoscale morphologies but also allows the rational design of catalyst-free solution-phase syntheses that could enable the scalable and low cost production of nanomaterials necessary for large scale applications, such as solar and thermoelectric energy conversions, energy storage, and nanocomposites. In this Account, we discuss the fundamental theories of the screw dislocation driven growth of various nanostructures including one-dimensional nanowires and nanotubes, two-dimensional nanoplates, and three-dimensional hierarchical tree-like nanostructures. We then introduce the transmission electron microscopy (TEM) techniques to structurally characterize the dislocation-driven nanomaterials for future searching and identifying purposes. We summarize the guidelines for rationally designing the dislocation-driven growth and discuss specific examples to illustrate how to implement the guidelines. By highlighting our recent discoveries in the last five years, we show that dislocation growth is a general and versatile mechanism that can be used to grow a variety of nanomaterials via distinct reaction chemistry and synthetic methods. These discoveries are complemented by selected examples of anisotropic crystal growth from other researchers. The fundamental investigation and development of dislocation-driven growth of nanomaterials will create a new dimension to the rational design and synthesis of increasingly complex nanomaterials. PMID:23738750

Meng, Fei; Morin, Stephen A; Forticaux, Audrey; Jin, Song

2013-07-16

257

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

PubMed

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

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

2009-10-01

258

Percutaneous iliosacral screw placement using image guided techniques.  

PubMed

A computer assisted technique of iliosacral screw placement that is applicable to unstable pelvic ring fractures is proposed. The goals are to operate noninvasively with a percutaneous procedure to decrease the complications of surgical exposure and to provide greater accuracy in locating the close neurovascular structures. Preoperative computed tomographic images of the pelvis are provided and a computed tomography three-dimensional model is built. In this model, the optimal trajectories for the drilling are planned. An ultrasound based registration is performed intraoperatively. This registration is the most original part of this work. After performing the passive drilling guidance step, the surgeon places the screws. The accuracy of the ultrasound based registration is checked by comparison with a standard surface based registration at the end of the test experiment. Each screw position is verified by a computed tomographic examination. Four human anatomic specimen pelves were tested with three screw insertions for each pelvis (12 screws). All of the screws were considered to be placed correctly. The method is safe and encourages the start of clinical application. PMID:9755769

Tonetti, J; Carrat, L; Lavalleé, S; Pittet, L; Merloz, P; Chirossel, J P

1998-09-01

259

Role of Dynesys as Pedicle-Based Nonfusion Stabilization for Degenerative Disc Disorders  

PubMed Central

Posterior nonfusion pedicle-screw-based stabilization remains a controversial area of spine surgery. To date, the Dynesys system remains the most widely implanted posterior nonfusion pedicle screw system. We review the history of Dynesys and discuss clinical outcome studies and biomechanical evaluations regarding the Dynesys system. Indications for surgery and controversies are discussed. Recommendations are made regarding technical implantation. PMID:23326673

Anand, Neel; Baron, Eli M.

2012-01-01

260

Joint Disorders  

MedlinePLUS

A joint is where two or more bones come together, like the knee, hip, elbow, or shoulder. Joints can be damaged by many types of injuries or diseases, including Arthritis - inflammation of a joint. It causes pain, stiffness, and swelling. Over time, ...

261

Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study  

PubMed Central

Background: The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD), diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws. Materials and Methods: Sixty fresh human cadaveric vertebrae (D10–L2) were harvested. Dual-energy X-ray absorptiometry (DEXA) scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm) were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a) standard pedicle screw (no cortical perforation); b) screw with medial cortical perforation; and c) screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine. Results: Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra (P = 0.105), but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD (P = 0.901). Conclusion: The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different. PMID:23798753

Saraf, Shyam K; Singh, Ravindra P; Singh, Vakil; Varma, Ashish

2013-01-01

262

Solid and hollow pedicle screws affect the electrical resistance: A potential source of error with stimulus-evoked electromyography  

PubMed Central

Background: Although stimulus evoked electromyography (EMG) is commonly used to confirm the accuracy of pedicle screw placement. There are no studies to differentiate between solid screws and hollow screws to the electrical resistance of pedicle screws. We speculate that the electrical resistance of the solid and hollow pedicle screws may be different and then a potential source of error with stimulus-evoked EMG may happen. Materials and Methods: Resistance measurements were obtained from 12 pedicle screw varieties (6 screws of each manufacturer) across the screw shank based on known constant current and measured voltage. The voltage was measured 5 times at each site. Results: Resistance of all solid screws ranged from 0.084 ? to 0.151 ? (mean =0.118 ± 0.024 ?) and hollow screws ranged from 0.148 ? to 0.402 ? (mean = 0.285 ± 0.081 ?). There was a significant difference of resistance between the solid screws and hollow screws (P < 0.05). The screw with the largest diameter no matter solid screws or hollow screws had lower resistance than screws with other diameters. No matter in solid screws group or hollow screws group, there were significant differences (P < 0.05) between the 5.0 mm screws and 6.0 mm screws, 6.0 mm screws and 7.0 mm screws, 5.0 mm screws and 7.0 mm screws, 4.5 mm screws and 5.5 mm screws, 5.5 mm screws and 6.5 mm screws, 4.5 mm screws and 6.5 mm screws. The resistance of hollow screws was much larger than the solid screws in the same diameter group (P < 0.05). Conclusions: Hollow pedicle screws have the potential for high electrical resistance compared to the solid pedicle screws and therefore may affect the EMG response during stimulus-evoked EMG testing in pedicle screw fixation especially in minimally invasive percutaneous pedical screw fixation surgery. PMID:23960278

Wang, Hongwei; Liao, Xinhua; Ma, Xianguang; Li, Changqing; Han, Jianda; Zhou, Yue

2013-01-01

263

Ideal Kink Modes In a Line-Tied Screw Pinch With Finite Plasma Pressure*  

NASA Astrophysics Data System (ADS)

A new method for computing ideal magnetohydrodynamic linear eigenmodes in a cylindrical screw pinch with line-tying boundary conditions is presented. In this method, plasma volume is reflected over one of the end plates, and equations and field components are continued on 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 yielding growth rates and eigenmodes for the system. Example of an m=1 (m is poloidal mode number) internal kink instability in force-free plasma equilibrium with uniform pressure is considered. In contrast to a periodic screw pinch, marginally stable perturbations are essentially compressible in line-tied geometry. Finite compressibility makes the mode more stable in addition to usual line-tying stabilization in zero pressure plasma. The critical length corresponding to marginal stability increases with the increase of plasma beta. A universal axial dependence for marginally stable density perturbations ?(r, z) = ?(r) exp(- i z / q(r)) is predicted analytically and confirmed numerically (q = r Bz/B? ). The work was supported by the U.S. D.O.E. and N.S.F.

Mirnov, V. V.; Svidzinski, V. A.; Li, H.

2008-11-01

264

m =1 ideal kink modes in a line-tied screw pinch with finite plasma pressure  

NASA Astrophysics Data System (ADS)

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 ?(r ,z)=?(r)exp[-iz?(r)] is predicted analytically and confirmed numerically, where ?(r ) depends on the equilibrium magnetic field components as ?(r )=B¯?/rB¯z.

Svidzinski, V. A.; Mirnov, V. V.; Li, H.

2008-09-01

265

Reconstruction of the anterior cruciate ligament using poly- l-lactide interference screws or titanium screws: a comparative study  

Microsoft Academic Search

In the present clinical trial, interference screws, made of poly-l-lactic acid and applied in 46 knees, were compared to titanium screws employed in 45 knees for reconstructing the anterior cruciate ligament using bone–patellar tendon–bone. An identical surgical technique was applied to both groups; and neither group disclosed apparent side effects such as synovitis caused by hydrolysis of the PLLA or

Akihiro Kotani; Yoshiaki Ishii

2001-01-01

266

An analytical investigation of high-temperature heat pump system with screw compressor and screw expander for power recovery  

Microsoft Academic Search

An analytical investigation of a high-temperature heat pump system was developed to estimate the thermal cycle and to assess the thermal fluids for their high-temperature delivery (up to 180°C) capacities without decomposition or the use of lubricant mechanisms. Then, a screw-type compressor was applied in the above conditions. Furthermore, a screw expander was also used as a replacement for the

I. Tamura; H. Taniguchi; H. Sasaki; R. Yoshida; I. Sekiguchi; M. Yokogawa

1997-01-01

267

Fixation strength of the interference screw in the femoral tunnel: The effect of screw divergence on the coronal plane.  

PubMed

Clinical studies to examine the effect of screw divergence have not been applied to the fixation of hamstring grafts. A few previous reports have addressed the correlations between the loss of pullout strength and divergence on hamstring tendon fixation in biomechanical tests. The purpose of this study was to examine the effect of interference screw divergence on the coronal plane when digital flexor tendons were fixed with an interference screw. Twenty fresh porcine hindlimb specimens were chosen. The grafts were fixed using titanium soft tissue interference screws. The hindlimbs were divided into two groups according to the insertion method of the screw. The screw was placed along the graft parallel to the long axis of the femoral tunnel in 10 specimens (parallel placement group), and the others were placed laterally at a 15° divergent angle from the bone tunnel on the coronal plane (divergence group). The cyclic-loading test was loaded for 1500cycles. Five specimens failed because of a pull-out of the tendon in divergence group. The number of specimens that failed before the completion of cycles in the divergence group was significantly greater than that in the parallel placement group. Although the residual displacement after 1500cycles for the divergence group was greater than that for the parallel placement group, no statistically significant difference was found between the groups. This study suggests that the screw placed laterally at a 15° divergent angle on the coronal plane decreases the fixation strength of the digital flexor tendons fixed with an interference screw. PMID:20199864

Ninomiya, Tadaaki; Tachibana, Yomei; Miyajima, Tsuyoshi; Yamazaki, Katsuhiko; Oda, Hiromi

2011-03-01

268

Helical Screw Expander Evaluation Project. Final report  

SciTech Connect

A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 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. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. 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.

McKay, R.

1982-03-01

269

The Structural Engineer 88 (1) 5 January 2010 25 This paper presents a model for the strength of inclined screws  

E-print Network

, in tension or shear, and four modes which combine bending of the screw and timber. The four combined modes displacement of screw tip. Angle of inclination of the screw axis with the vertical. ax Axial displacement of screw. f h W tT RXRX lat Lateral displacement of screw at the material interface. Ratio of withdrawal

Crilly, Nathan

270

Simultaneous middle third clavicle fracture and type 3 acromioclavicular joint dislocation; a case report.  

PubMed

Simultaneous middle third clavicle fracture and acromioclavicular joint dislocation is a rare combination injury, as a result of high-energy trauma. We report a patient with a middle third clavicle fracture and ipsilateral grade three-acromioclavicular joint dislocation, which is a rare combination. The patient wanted to get back to work as soon as possible, so the fracture was fixed with reconstruction plate after open reduction and plate contouring; and acromioclavicular joint dislocation was reduced and fixed with two full threaded cancellous screws. One screw was inserted through the plate to the coracoid process. Clinical and radiographic finding revealed complete union of clavicle fracture and anatomical reduction of acromioclavicular joint with pain free full joint range of motion one year after operation. PMID:25207318

Solooki, Saeed; Azad, Ali

2014-03-01

271

Simultaneous Middle Third Clavicle Fracture and Type 3 Acromioclavicular Joint Dislocation; A Case Report  

PubMed Central

Simultaneous middle third clavicle fracture and acromioclavicular joint dislocation is a rare combination injury, as a result of high-energy trauma. We report a patient with a middle third clavicle fracture and ipsilateral grade three-acromioclavicular joint dislocation, which is a rare combination. The patient wanted to get back to work as soon as possible, so the fracture was fixed with reconstruction plate after open reduction and plate contouring; and acromioclavicular joint dislocation was reduced and fixed with two full threaded cancellous screws. One screw was inserted through the plate to the coracoid process. Clinical and radiographic finding revealed complete union of clavicle fracture and anatomical reduction of acromioclavicular joint with pain free full joint range of motion one year after operation. PMID:25207318

Solooki, Saeed; Azad, Ali

2014-01-01

272

Prediction of Deformity Correction by Pedicle Screw Instrumentation in Thoracolumbar Scoliosis Surgery  

NASA Astrophysics Data System (ADS)

In segmental pedicle screw instrumentation, the relationship between the combinations of pedicle screw placements and the degree of deformity correction was investigated with a three-dimensional rigid body and spring model. The virtual thoracolumbar scoliosis (Cobb’s angle of 47 deg.) was corrected using six different combinations of pedicle-screw placements. As a result, better correction in the axial rotation was obtained with the pedicle screws placed at or close to the apical vertebra than with the screws placed close to the end vertebrae, while the correction in the frontal plane was better with the screws close to the end vertebrae than with those close to the apical vertebra. Additionally, two screws placed in the convex side above and below the apical vertebra provided better correction than two screws placed in the concave side. Effective deformity corrections of scoliosis were obtained with the proper combinations of pedicle screw placements.

Kiriyama, Yoshimori; Yamazaki, Nobutoshi; Nagura, Takeo; Matsumoto, Morio; Chiba, Kazuhiro; Toyama, Yoshiaki

273

[Evaluation of AO kit screw fixation of medial condyle and epicondyle distal humeral epiphyseal fractures in children].  

PubMed

In the Pediatric Surgery Department of the Voivodeship Hospital in Koszalin the use of screw fixation claims to be the method od choice for treating the fractures of medial epicondyle and condyles of the distal humeral bone epiphysis in children, thus challenging Kirschner's wire fixation being commonly applied in these traumas, and in consequence making it necessary to compare the results obtained after resorting to each of these methods. The accomplished comparative study covered the total of 101 persons, aged from 5 to 28 years, over the period from 1 to 15 years (mean 6 years) after trauma, treated due to the above-mentioned injuries in the years 1976-1990, at this Department (86 persons), and in the years 1980-1990 at the Pediatric Surgery Clinic of the Pomeranian Medical Academy in Szczecin (15 persons) exclusively by means of Kirschner's wire fixation. In 64 patients screw fixation was implanted, and in 37-Kirschner's wire. The studied material was divided into 4 subgroups (Tab. 1) comprising respectively: 41 persons (subgroup A) after past fracture of medial epicondyle treated by screw fixation; 26 persons (subgroup A1) with past medial epicondyle fracture treated by Kirschner's wire fixation: 23 persons with past condyle fracture treated by screw fixation (subgroup B) and 11 persons after condyle fracture treated by Kirschner's wire fixation (subgroup B1). Three control groups were set up: control group I, showed normal reference values, represented the assessments of healthy ulnar joints contrasting with the previously inflicted injury in 101 persons of the studied group. The control group II, concerning the physical examinations, incorporated 43 persons burdened neither by past trauma, nor by any other lesions of the ulnar joints, randomly selected: 23 children, 12 under the care of their parents, and 11 persons of juvenile age, registered with the pediatric surgery or rehabilitation consulting centres in Koszalin. Control group III, concerned with correct radiologic measurements included 45 persons randomly selected, aged from 5 to 27 years in whom radiograms of their ulnar joints were made on indications not involving the trauma of the joint. The clinical evaluation took into account the anamnesis data, assessment of the ulnar joint shape, appearance of the postoperative scar, innervation status within the ulnar nerve range, measurements of the length of arm, its circumference, flexion and extension movement (with analysis of the range of movement) value of the angle of the arm axis deviation in relation to forearm axis, as well as muscle power. The radiographic evaluation encompassed the measurements of angles: humeral, ulnar, physiological valgity as well as diaphysio-epiphysial one, and moreover, the evaluation of the symphysis quality, outlines of distal epiphysis of the humeral bone and its bony structure. The mentioned parameters of the clinical evaluation, two of the parameters of the radiological evaluation, and also the final point estimation of the treatment results were subjected to statistical analysis by applying the analysis of variance, with the level of significance being accepted as p = 0.05. The noted results have shown that significant findings in the clinical evaluation were primarily the measurements of both the range of movements and the angle of the arm axis deviation, in relation to the forearm axis, while in the radiological evaluation-the symphysis quality estimation and occasionally occurring absence of correlation between the result of clinical evaluation and the radiological one (Fig. 1). Moreover, the recorded results pointed to the screw fixation as being more favourable, than Kirschner's wire fixation, method of treating the mentioned injuries in children (clinical and radiological data were favouring the screw fixation in fractures of medial epicondyle-whereas in condyle fractures-first of all the clinical data). (ABSTRACT TRUNCATED) PMID:9471919

Szyma?ska, E

1997-01-01

274

Experimental study of the subtalar joint axis: preliminary investigation.  

PubMed

An experimental study of the subtalar joint has been conducted with the aim of establishing its axis of movement as well as analysing the associated movement. For description of the axis, CT data for five positions of a single foot were reconstructed using a 3D programme, the 3D data was processed by Patran software. Measures of angular displacements were made from three amputated feet placed in a specially constructed foot frame. Four instantaneous axes of movement could be defined. Calculation of displacements showed an important rolling of the calcaneus (45 degrees). Tacking was evident in inversion, with an opposite displacement between the front and rear part of the calcaneus, whereas during eversion tacking affected only the rear part of the bone: these results were confirmed by 3D reconstructions. Henke's axis was described as that for the talonavicular joint, but acceptable for the subtalar joint. Several authors investigating the coordinates of this axis have reported large differences and described screw-like movements, the latter being incompatible with a fixed axis: instantaneous axes, however are compatible with a screw-like movement. The subtalar joint appears to work as a pivot joint during inversion and as a plane joint during eversion. Although Henke's axis has pedagogical value the subtalar joint has a series of instantaneous axes. PMID:11236321

Zographos, S; Chaminade, B; Hobatho, M C; Utheza, G

2000-01-01

275

Biomechanical analysis of screw constructs for atlantoaxial fixation in cadavers: a systematic review and meta-analysis.  

PubMed

OBJECT The unique and complex biomechanics of the atlantoaxial junction make the treatment of C1-2 instability a challenge. Several screw-based constructs have been developed for atlantoaxial fixation. The biomechanical properties of these constructs have been assessed in numerous cadaver studies. The purpose of this study was to systematically review the literature on the biomechanical stability achieved using various C1-2 screw constructs and to perform a meta-analysis of the available data. METHODS A systematic search of PubMed through July 1, 2013, was conducted using the following key words and Boolean operators: "atlanto [all fields]" AND "axial [all fields]" OR "C1-C2" AND "biomechanic." Cadaveric studies on atlantoaxial fixation using screw constructs were included. Data were collected on instability models, fixation techniques, and range of motion (ROM). Forest plots were constructed to summarize the data and compare the biomechanical stability achieved. RESULTS Fifteen articles met the inclusion criteria. An average (± SD) of 7.4 ± 1.8 cadaveric specimens were used in each study (range 5-12). The most common injury models were odontoidectomy (53.3%) and cervical ligament transection (26.7%). The most common spinal motion segments potted for motion analysis were occiput-C4 (46.7%) and occiput-C3 (33.3%). Four screw constructs (C1 lateral mass-C2 pedicle screw [C1LM-C2PS], C1-2 transarticular screw [C1-C2TA], C1 lateral mass-C2 translaminar screw [C1LM-C2TL], and C1 lateral mass-C2 pars screw [C1LM-C2 pars]) were assessed for biomechanical stability in axial rotation, flexion/extension, and lateral bending, for a total of 12 analyses. The C1LM-C2TL construct did not achieve significant lateral bending stabilization (p = 0.70). All the other analyses showed significant stabilization (p < 0.001 for each analysis). Significant heterogeneity was found among the reported stabilities achieved in the analyses (p < 0.001; I(2) > 80% for all significant analyses). The C1LM-C2 pars construct achieved significantly less axial rotation stability (average ROM 36.27° [95% CI 34.22°-38.33°]) than the 3 other constructs (p < 0.001; C1LM-C2PS average ROM 49.26° [95% CI 47.66°-50.87°], C1-C2TA average ROM 47.63° [95% CI 45.22°-50.04°], and C1LM-C2TL average ROM 53.26° [95% CI 49.91°-56.61°]) and significantly more flexion/extension stability (average ROM 13.45° [95% CI 10.53°-16.37°]) than the 3 other constructs (p < 0.001; C1LM-C2PS average ROM 9.02° [95% CI 8.25°-9.80°], C1-C2TA average ROM 7.39° [95% CI 5.60°-9.17°], and C1LM-C2TL average ROM 7.81° [95% CI 6.93°-8.69°]). The C1-C2TA (average ROM 5.49° [95% CI 3.89°-7.09°]) and C1LM-C2 pars (average ROM 4.21° [95% CI 2.19°-6.24°]) constructs achieved significantly more lateral bending stability than the other constructs (p < 0.001; C1LM-C2PS average ROM 1.51° [95% CI 1.23°-1.78°]; C1LM-C2TL average ROM -0.07° [95% CI -0.44° to 0.29°]). CONCLUSIONS Meta-analysis of the existing literature showed that all constructs provided significant stabilization in all axes of rotation, except for the C1LM-C2TL construct in lateral bending. There were significant differences in stabilization achieved in each axis of motion by the various screw constructs. These results underline the various strengths and weaknesses in biomechanical stabilization of different screw constructs. There was significant heterogeneity in the data reported across the studies. Standardized spinal motion segment configuration and injury models may provide more consistent and reliable results. PMID:25478824

Du, Jerry Y; Aichmair, Alexander; Kueper, Janina; Wright, Timothy; Lebl, Darren R

2014-12-01

276

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

PubMed Central

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.

Haque, Mohammod Raziul

2014-01-01

277

Endovascular aortic injury repair after thoracic pedicle screw placement.  

PubMed

Our objective was to describe the management and prevention of thoracic aortic injuries caused by a malposition of pedicle screws in corrective surgery of major spine deformities. Positioning pedicle screws in thoracic vertebras by posterior approach exposes to the risk of injury of the elements placed ahead of the thoracic spine, as the descending thoracic aorta. This complication can result in a cataclysmic bleeding, needing urgent vascular care, but it can also be totally asymptomatic, resulting in the long run in a pseudoaneurysm, justifying the systematic removal of the hardware. We report the case of a 76-year-old woman who underwent spinal correction surgery for thoraco-lumbar degenerative kypho-scoliosis. Immediately after the surgery, a thoracic aortic injury caused by the left T7 pedicle screw was diagnosed. The patient underwent a two-step surgery. The first step was realized by vascular surgeons and aimed to secure the aortic wall by short endovascular aortic grafting. During the second step, spine surgeons removed the responsible screw by posterior approach. The patient was discharged in a rehabilitation center 7 days after the second surgery. When such a complication occurs, a co-management by vascular and spine surgeons is necessary to avoid major complications. Endovascular management of this kind of vascular injuries permits to avoid an open surgery that have a great rate of morbi-mortality in frail patients. Nowadays, technologies exist to prevent this kind of event and may improve the security when positioning pedicle screws. PMID:25023930

Pesenti, S; Bartoli, M A; Blondel, B; Peltier, E; Adetchessi, T; Fuentes, S

2014-09-01

278

Modern posterior screw techniques in the pediatric cervical spine  

PubMed Central

Treatment of children with cervical spine disorders requiring fusion is a challenging endeavor for a variety of reasons. The size of the patients, the corresponding abnormal bony anatomy, the inherent ligamentous laxity of children, and the relative rarity of the disorders all play a part in difficulty of treatment. The benefits of modern posterior cervical instrumentation in children, defined as rigid screw-rod systems, have been shown to be many including: improved arthrodesis rates, diminished times in halo-vest immobilization, and improved reduction of deformities. The anatomy of children and the corresponding pathology seen frequently is at the upper cervical spine and craniocervical junction given the relatively large head size of children and the horizontal facets at these regions predisposing them to instability or deformity. Posterior screw fixation, while challenging, allows for a rigid base to allow for fusion in these upper cervical areas which are predisposed to pseudarthrosis with non-rigid fixation. A thorough understanding of the anatomy of the cervical spine, the morphology of the cervical spine, and the available screw options is paramount for placing posterior cervical screws in children. The purpose of this review is to discuss both the anatomical and clinical descriptions related to posterior screw placement in the cervical spine in children. PMID:24829871

Hedequist, Daniel J

2014-01-01

279

Screw dislocations in GaN grown by different methods  

SciTech Connect

A study of screw dislocations in Hydride-Vapor-Phase-Epitaxy (HVPE) template and Molecular-Beam-Epitaxy (MBE) over-layers was performed using Transmission Electron Microscopy (TEM) in plan-view and in cross-section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

Liliental-Weber, Z.; Zakharov, D.; Jasinski, J.; O'Keefe, M.A.; Morkoc, H.

2003-05-27

280

Ball screw preload loss detection using ball pass frequency  

NASA Astrophysics Data System (ADS)

A technique of determining the onset of preload loss in a ball screw feed drive system via monitoring the change of ball pass frequency is proposed. The ball pass frequency of a ball screw with preload is smaller than that of ball screw without preload due to friction caused by the preload. Results from both simulations and experiments show that the ball pass frequency can be detected using the method of Angular Velocity Vold-Kalman Filtering Order Tracking (AV VKF-OT). And AV VKF-OT provides a much better performance as compared to the traditional order tracking in terms of resolution and accuracy. Tests were conducted on ball screw feed drive systems with different preloads for the performance assessment of the ball pass frequency detection. Results show that the preload loss increases the ball pass frequency and also induces the side band around the ball pass frequency, which provides promising criteria in detecting the onset of preload loss of ball screws.

Tsai, P. C.; Cheng, C. C.; Hwang, Y. C.

2014-10-01

281

Transsacral screw safe zone size by sacral segmentation variations.  

PubMed

Variations in sacral segmentation may preclude safe placement of transsacral screws for posterior pelvis fixation. We developed a novel automated 3D technique to determine the safe zone size for transsacral screws in the upper two sacral segments in 526 adult pelvis computed tomography scans. Safe zone sizes were then compared by gender and sacral segmentation variations (number of neuroforamen and the presence/absence of lumbosacral transitional vertebrae, ±LSTV). Ten millimeters was used as the safety threshold for a large screw. 3 (0.6%), 366 (70%), and 157 (30%) sacra had 3, 4, or 5 neuroforamen, respectively. Eighty-eight (17%) were +LSTV. Safe zone size depended on gender, number of neuroforamen in -LSTV sacra and presence of LSTV (p?screw safely, 77% can do so in S2, leaving only 4% of sacra that cannot accommodate a screw safely in either upper segment. The results demonstrate a predictable pattern of safe zone size based on gender and sacral segmentation variations. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:277-282, 2015. PMID:25231682

Lee, John J; Rosenbaum, Samuel L; Martusiewicz, Alex; Holcombe, Sven A; Wang, Stewart C; Goulet, James A

2015-02-01

282

Outcome Assessment after Aptis Distal Radioulnar Joint (DRUJ) Implant Arthroplasty  

PubMed Central

Background: Conventional treatments after complicated injuries of the distal radioulnar joint (DRUJ) such as Darrach and Kapandji-Sauvé procedures have many drawbacks, which may eventually lead to a painful unstable distal ulna. The development of DRUJ prosthesis has significantly evolved over the past years. In this study, we assessed the outcome results of patients after DRUJ implant arthroplasty using the Aptis (Scheker) prosthesis. Methods: We identified 13 patients with 14 prosthesis during the past 10 years. Patients underwent DRUJ arthroplasty due to persistent symptoms of instability, chronic pain, and stiffness. Records and follow-up visits were reviewed to find the final post-operative symptoms, pain, range of motion, and grip strength with a mean follow-up of 12 months (range: 2-25 months). Also, patients were contacted prospectively by phone in order to administer the disabilities of the arm shoulder and hand (DASH), patient rated wrist evaluation (PRWE), and visual analogue scale (VAS), and to interview regarding satisfaction and progress in daily activities. Eleven patients out of 13 could be reached with a median follow-up time of 60 months (range: 2 to 102 months). Results: No patient required removal of the prosthesis. Only two patients underwent secondary surgeries in which both required debridement of the screw tip over the radius. The median DASH score, PRWE score, VAS, and satisfaction were 1.3, 2.5, 0, and 10, respectively. The mean range of flexion, extension, supination, and pronation was 62, 54, 51, and 64, respectively. Conclusions: Distal radioulnar joint injuries are disabling and patients usually undergo one or more salvage surgeries prior to receiving an arthroplasty. The Scheker prosthesis has shown satisfactory results with 100% survival rate in all reports. The constrained design of this prosthesis gives enough stability to prevent painful subluxation. PMID:25386579

Kachooei, Amir Reza; Chase, Samantha M; Jupiter, Jesse B

2014-01-01

283

2D-fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries - a case series  

PubMed Central

Background Screw fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system. Methods Between August 2004 and December 2007, 44 of 442 patients with pelvic injuries were included for closed reduction and percutaneous screw fixation of disrupted pelvic ring lesions using an optoelectronic 2D-fluoroscopic based navigation system. Operating and fluoroscopy time were measured, as well as peri- and postoperative complications documented. Screw position was assessed by postoperative CT scans. Quality of live was evaluated by SF 36-questionnaire in 40 of 44 patients at mean follow up 15.5 ± 1.2 month. Results 56 iliosacral- and 29 ramus pubic-screws were inserted (mean operation time per screw 62 ± 4 minutes, mean fluoroscopy time per screw 123 ± 12 seconds). In post-operative CT-scans the screw position was assessed and graded as follows: I. secure positioning, completely in the cancellous bone (80%); II. secure positioning, but contacting cortical bone structures (14%); III. malplaced positioning, penetrating the cortical bone (6%). The malplacements predominantly occurred in bilateral overlapping screw fixation. No wound infection or iatrogenic neurovascular damage were observed. Four re-operations were performed, two of them due to implant-misplacement and two of them due to implant-failure. Conclusion 2D-fluoroscopic navigation is a safe tool providing high accuracy of percutaneous screw placement for pelvic ring fractures, but in cases of a bilateral iliosacral screw fixation an increased risk for screw misplacement was observed. If additional ramus pubic screw fixations are performed, the retrograde inserted screws have to pass the iliopubic eminence to prevent an axial screw loosening. PMID:20609243

2010-01-01

284

Magnetic field rotation in the screw gallium flow  

NASA Astrophysics Data System (ADS)

The magnetic field induced by the nonstationary screw flow of gallium in a toroidal channel has been investigated experimentally using a gallium prototype of the sodium apparatus developed in the frame of the experimental dynamo program at the Institute of Continuous Media Mechanics, Perm, Russia. The experimental set-up is a rapidly rotating toroidal channel subjected to abrupt braking. The screw flow is initiated by inertial forces pushing liquid gallium through diverters. The regular structure of the induced magnetic field is generated about 0.1 s after the stop of the channel and persists up to 1 s. The induced field is measured by sensors placed outside the channel. The inductive effects observed are attributed to the mean screw flow. The decay laws of the induced regular magnetic field and turbulent magnetic fluctuations are studied.

Noskov, V.; Denisov, S.; Frick, P.; Khripchenko, S.; Sokoloff, D.; Stepanov, R.

2004-10-01

285

Mechanical Properties of Nanotextured Titanium Orthopedic Screws for Clinical Applications.  

PubMed

In this work, we modified the topography of commercial titanium orthopedic screws using electrochemical anodization in a 0.4?wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterized using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and [Formula: see text]. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results showed that the fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations. PMID:23904907

Descamps, Stephane; Awitor, Komla O; Raspal, Vincent; Johnson, Matthew B; Bokalawela, Roshan S P; Larson, Preston R; Doiron, Curtis F

2013-06-01

286

Efficiency study of oil cooling of a screw compressor  

SciTech Connect

One of the major goals of all compressor manufacturers is to build as efficient a compressor as possible. Over the last several years improvements to the design of screw compressors has made them efficiently competitive with other types of compressors, especially at large loads. The primary purpose of this research is to investigate four different methods of cooling a 250 horsepower compressor and determine their effects on the efficiency of the compressor. Two conventional methods, liquid injection and thermosyphon cooling, and two new methods, V-PLUS and Fresco oil injection, are investigated. The screw compressor used in the tests was a VRS-500 screw compressor made by the Vilter Manufacturing Corporation. 6 figs.

Tree, D.R.; McKellar, M.G.

1989-04-01

287

Mild coal gasification screw pyrolyzer development and design  

SciTech Connect

Our objective is to produce information and design recommendations needed for the development of an efficient continuous process for the mild gasification of caking bituminous coals. We have focused on the development of an externally heated pyrolyzer in which the sticky, reacting coal is conveyed by one or more screws. We have taken a multifaceted approach to forwarding the development of the externally-heated screw pyrolyzer. Small scale process experiments on a 38-mm single screw pyrolyzer have been a major part of our effort. Engineering analyses aimed at producing design and scaleup equations have also been important. Process design recommendations follow from these. We critically review our experimental data and experience, and information from the literature and equipment manufactures for the purpose of making qualitative recommendations for improving practical pyrolyzer design and operation. Benchscale experiments are used to supply needed data and test some preliminary concepts. 6 refs., 4 figs., 1 tab.

Camp, D.W.

1990-08-01

288

Use of the electro-mechanical impedance method for the assessment of dental implant stability  

NASA Astrophysics Data System (ADS)

The robustness and reliability of the Electro-Mechanical Impedance (EMI) method to assess dental prostheses stability is presented. The study aim at addressing an increasing need in the biomedical area where robust, reliable, and non-invasive methods to assess the bone-interface of dental and orthopedic implants are increasingly demanded for clinical diagnosis and direct prognosis. In this study two different dental screws were entrenched in polyurethane foams and immersed in a solution of nitric acid to allow material degradation, inversely simulating a bone-healing process. This process was monitored by bonding a Piezoceramic Transducer (PZT) to the implant and measuring the admittance of the PZT over time. To simulate healing, a second set of experiments was conducted. It consisted of placing four dental screws inside a joint compound specimen and observing the setting of the fresh compound allocated in the alveolus containing each implant. In all cases it was found that the PZT's conductance and the statistical features associated with the analysis of the admittance signatures were sensitive to the degradation or the setting process.

Rizzo, Piervincenzo; Boemio, Giovanni; de Nardo, Luigi

2011-04-01

289

Hamstring anterior cruciate ligament reconstruction: a comparison of bioabsorbable interference screw and endobutton-post fixation  

Microsoft Academic Search

PurposeThe purpose of this study was to evaluate hamstring anterior cruciate ligament (ACL) reconstruction using aperture fixation with bioabsorbable interference screw (BIS) and distant fixation using EndoButton (Smith & Nephew, Andover, MA) and screw-post (ENDO).

C. Benjamin Ma; Kimberly Francis; Jeffrey Towers; Jay Irrgang; Freddie H Fu; Christopher H Harner

2004-01-01

290

Efficiency and Leakage Analysis of a Twin-Screw Multiphase Pump  

E-print Network

Multiphase twin-screw pumps have become an important alternative to produce the oil and natural gas from wells. In comparison to a conventional multiphase oil production systems, a multiphase twin screw pump provides larger boost with smaller...

Turhan, Yusuf

2014-04-01

291

Tightening force and torque of nonlocking screws in a reverse shoulder prosthesis A. Terrier a,  

E-print Network

of bone volume around each screw was measured with a micro-CT. Measurements were performed on 6 human of the screw position has been recently investigated using micro-CT reconstructions of cadaveric scapulas

Guerraoui, Rachid

292

29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.  

Code of Federal Regulations, 2010 CFR

...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...

2010-07-01

293

Finger Joint Injuries.  

PubMed

Finger joint dislocations and collateral ligament tears are common athletic hand injuries. Treatment of the athlete requires a focus on safe return to play and maximizing function. Certain dislocations, such as proximal interphalangeal and distal interphalangeal volar dislocations, may be associated with tendon injuries and must be treated accordingly. Treatment of other dislocations is ultimately determined by postreduction stability, with many dislocations amenable to nonoperative treatment (ie, immobilization followed by rehabilitation). Protective splinting does not necessarily preclude athletic participation. Minor bone involvement typically does not affect the treatment plan, but significant articular surface involvement may necessitate surgical repair or stabilization. Percutaneous and internal fixation are the mainstays of surgical treatment. Treatment options that do not minimize recovery or allow the patient to return to protected play, such as external fixation, are generally avoided during the season of play. Undertreated joint injuries and unrecognized ligament injuries can result in long term disability. PMID:25455398

Prucz, Roni B; Friedrich, Jeffrey B

2015-01-01

294

Interface effects on elastic behavior of a screw dislocation around double nanowires  

NASA Astrophysics Data System (ADS)

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.

Li, Jia; Fang, Qihong; Liu, Youwen

2014-06-01

295

Management of Unstable Thoraco-Lumbar Fractures with Pedicular Screw Instrumentation: A Series of 30 cases  

PubMed Central

Introduction: Trauma to spine is one of the grave injuries. They cause infinite morbidity and disability to the patient. Lately consensus is evolving across the world for stabilization of unstable spines with fusion and instrumentation even though most authors agree that neurological recovery is independent of treatment modality. Objectives of this study are to evaluate effectiveness of spinal stabilization with pedicular instrumentation in the management of thoraco-lumbar fractures to restore structural stability, early ambulation and improving neurological status of the patient Material and Methods: During the period from October 2009 to September 2010, 33 cases of thoraco-lumbar spine fractures were treated operatively with posterior decompression and pedicular screw instrumentation. Of these, 3 cases were lost to follow up. Hence the results of 30 cases were evaluated. All patients were treated by posterior decompression and pedicular screw instrumentation. Neurological and radiological parameters were assessed during serial follow-ups. Observation and Results: The mean duration of follow-up was 11 months. Of the 30 patients 24 showed neurological improvement by at least 1 grade and average grade of improvement was 1.5 grades. Mean pre-operative sagittal angle (SA) was 19.9 degrees and sagittal index (SI) was 0.54. Mean post-operative SA was 9.3 degrees and SI was 0.72. Mean SA and SI during the final follow-up were 10.9 degrees and 0.69 respectively. Discussion and Conclusion: Neurological recovery and maintenance of radiological correction in our study were comparable to other studies. The results in our short series of 30 cases have been encouraging. But there is need for more cases and longer follow-ups to come to categorical conclusion. PMID:24392401

Hegde, Atmananda; Babu, Rajan; Shetty, Abhishek

2013-01-01

296

Ballasted, screw-in lamps seen cutting costs in retrofits  

SciTech Connect

Affordable screw-in fluorescent and high-pressure sodium fixtures with built-in ballasts are now an efficient and practical retrofit that can save users up to 75% on electricity costs. Payback can be less than one year despite the high cost of the fixtures compared to incandescents. Users will also realize ongoing maintenance savings because the service life is 10 to 20 times longer. The development of miniature ballasts and electronic ballasts with solid-state technology and transistors that can be confined to a small space make the screw-in lighting devices possible. A directory lists 83 major manufacturers of lighting equipment.

Ingraham, R.

1984-09-03

297

A screw-actuated pneumatic valve for portable, disposable microfluidics.  

PubMed

This work describes a simple and inexpensive approach for controlling the pneumatic valves that were invented in Quake's group to miniaturize the whole system for portable and disposable microfluidic devices. The valves are assembled from two parts. One is the polydimethylsiloxane (PDMS) channels formed by multilayer soft lithography. The other is a polymethylmethacrylate (PMMA) frame with machine screws for pressure control. Turning the screws into the control channel inlet (filled with water and covered with a thin PDMS membrane) actuates the valve by creating pressure in the control channel. This method avoids the bulky and expensive external pressure-control facilities and can be easily integrated into portable and disposable devices. PMID:19156298

Zheng, Yizhe; Dai, Wen; Wu, Hongkai

2009-02-01

298

Virtual estimates of fastening strength for pedicle screw implantation procedures  

NASA Astrophysics Data System (ADS)

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.

Linte, Cristian A.; Camp, Jon J.; Augustine, Kurt E.; Huddleston, Paul M.; Robb, Richard A.; Holmes, David R.

2014-03-01

299

Ceramic joints  

DOEpatents

Butt joints between materials having different coefficients of thermal expansion are prepared having a reduced probability of failure of stress facture. This is accomplished by narrowing/tapering the material having the lower coefficient of thermal expansion in a direction away from the joint interface and not joining the narrow-tapered surface to the material having the higher coefficient of thermal expansion.

Miller, Bradley J. (Worcester, MA); Patten, Jr., Donald O. (Sterling, MA)

1991-01-01

300

Bioabsorbable Interference Screws for Graft Fixation in Anterior Cruciate Ligament Reconstruction  

Microsoft Academic Search

Summary: The central one third of the patellar tendon autograft is popular because the bone-tendon-bone (BTB) construct provides several graft fixation options, robust graft incorporation, and a mechanically sufficient substitute. Interference screw fixation is one method used to secure the graft. Bioabsorbable interference screws may offer advantages over metal interference screws. Bioabsorbable screws are made from poly L-lactic acid (PLLA)

David A. McGuire; F. Alan Barber; Burton F. Elrod; Lonnie E. Paulos

1999-01-01

301

The treatment of trochanteric fractures using a sliding screw-plate  

Microsoft Academic Search

Summary The authors report a retrospective study of 307 trochanteric fractures treated with a sliding screw-plate (trochanteric hip screw, THS) between January 1989 and December 1994. Mechanical failure was uncommon (3.6%); cutting-out of the screw was the main complication. The revision rate was also low (4%); the 12 cases included 5 total hip replacememts and 2 sliding-screw replacements. Whatever the

D. Jobard; P. Simon; S. R. Babin

1998-01-01

302

PROCESS GAS APPLICATIONS WHERE API 619 SCREW COMPRESSORS REPLACED RECIPROCATING AND CENTRIFUGAL COMPRESSORS  

Microsoft Academic Search

Oil-free screw compressors have been used for process gas application since the 1970s. Oil-flooded screw compressors have been used in many process related applications since the 1980s. Oil-flooded screw compressors are covered in the latest edition of API Standard 619 issued in 2004. Both oil-free and oil-flooded screw compressors have been expanding into process gas com- pression applications. It is

Takao Ohama; Yoshinori Kurioka; Takao Koga

303

Profile generation and analysis for a pp-type single-screw compressor  

Microsoft Academic Search

The precision design of the screw rotor and the gate rotor is the foundation to promoting the operational reliability of a pp-type single-screw compressor. The purpose of the present paper is to determine the mathematical model of a single-screw rotor with conical gate rotors. A simple method by gear theory to determine the profiles of a screw rotor and a

Shyue-Cheng Yang

2006-01-01

304

Compression forces generated by Mini bone screws—a comparative study done on bone model  

Microsoft Academic Search

The compressive forces generated by the AO\\/ASIF 3.0mm cannulated cancellous and 2.0mm cortical screws, Mini-Acutrak and Herbert\\/Whipple small bone cannulated screws were measured in the laboratory with the use of simulated cancellous bone and a load cell washer as a means of quantifying their fixation capabilities. The Herbert\\/Whipple screw and the Mini-Acutrak screw were found to have nearly identical compression

Deepthi Nandan Adla; C. Kitsis; A. W. Miles

2005-01-01

305

The effect of implant shape and bone preparation on primary stability  

PubMed Central

Purpose The purpose of this study was to evaluate the effects of implant shape and bone preparation on the primary stability of the implants using resonance frequency analysis. Methods Sixty bovine rib blocks were used for soft and hard bone models. Each rib block received two types of dental implant fixtures; a straight-screw type and tapered-screw type. Final drilling was done at three different depths for each implant type; 1 mm under-preparation, standard preparation, and 1 mm over-preparation. Immediately after fixture insertion, the implant stability quotient (ISQ) was measured for each implant. Results Regardless of the bone type, the ISQ values of the straight-screw type and tapered-screw type implants were not significantly different (P > 0.05). Depth of bone preparation had no significant effect on the ISQ value of straight-screw type implants (P > 0.05). For the tapered-screw type implants, under-preparation significantly increased the ISQ value (P < 0.05), whereas overpreparation significantly decreased the ISQ value (P < 0.05). Conclusions Within the limitations of this study, it is concluded that bone density seemed to have a prevailing effect over implant shape on primary stability. The primary stability of the tapered-screw type implants might be enhanced by delicate surgical techniques. PMID:21072221

Moon, Sang-Hyun; Lee, Jae-Kwan; Chang, Beom-Seok; Lee, Min-Ku

2010-01-01

306

Fracture of bilok interference screws on insertion during anterior cruciate ligament reconstruction  

Microsoft Academic Search

New femoral and tibial interference screws for use during anterior cruciate ligament (ACL) reconstruction have been developed using a composite of poly-L-lactic acid (PLLA) and tricalcium phosphate (TCP). The combination is described as having better incorporation than standard bioabsorbable screws with no loss of mass during incorporation and without the brittle nature associated with conventional TCP implants. However, the screw

Chadwick A Smith; T. Duncan Tennent; Sara E Pearson; William R Beach

2003-01-01

307

The roller screw, an efficient and reliable mechanical component of electro-mechanical actuators  

Microsoft Academic Search

The roller screw exists in three different designs which may be used in very different applications: the three designs are respectively known as planetary, differential planetary and recirculating roller screws. Most EMAs which are using roller screws use the planetary design because of its inherent capacity to withstand very high accelerations and speeds and its ability to handle heavy to

P. C. Lemor

1996-01-01

308

Anatomic considerations for standard and modified techniques of cervical lateral mass screw placement  

Microsoft Academic Search

Background context: Posterior screw placement techniques have been previously described. Each technique differs with respect to starting point, lateral angulation and sagittal orientation.Purpose: To examine the potential for injury to critical anatomic structures, such as nerve roots and vertebral arteries, during posterior cervical screw placement and to determine safe screw placement. Study design\\/setting: An anatomic study was conducted to determine

Andrew A Merola; B. Andrew Castro; Paul R Alongi; Sameer Mathur; Mario Brkaric; Franco Vigna; Joseph P Riina; John Gorup; Thomas R Haher

2002-01-01

309

Experimental determination of instantaneous screw axis in human motions. Error analysis  

Microsoft Academic Search

The location of the instantaneous screw axis (ISA) is essential in order to obtain useful kinematic models of the human body for applications such as prosthesis and orthoses design or even to help in disease diagnosis techniques. In this paper, dual vectors will be used to represent and operate with kinematic screws with the purpose of locating the instantaneous screw

Álvaro Page; Vicente Mata; Juan Víctor Hoyos; Rosa Porcar

2007-01-01

310

An approach to the functional anatomy of the sacroiliac joints in vivo  

Microsoft Academic Search

Summary This first part of this paper is a review of the literature on the functional anatomy of the sacroiliac joint followed by a preliminary biomechanical study of the fresh post mortem pelvis. The latter was done in order to determine the coefficients of the screw matrix and the position of the instantaneous centers of rotation during the symmetrical movements

B. Lavignolle; J. M. Vital; J. Senegas; J. Destandau; B. Toson; P. Bouyx; P. Morlier; G. Delorme; A. Calabet

1983-01-01

311

Cellulose and the twofold screw axis: Modeling and experimental arguments  

Technology Transfer Automated Retrieval System (TEKTRAN)

Crystallography indicates that molecules in crystalline cellulose either have 2-fold screw-axis (21) symmetry or closely approximate it, leading to short distances between H4 and H1' across the glycosidic linkage. Therefore, modeling studies of cellobiose often show elevated energies for 21 structur...

312

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

313

The Use of Small Titanium Screws for Orthodontic Anchorage  

Microsoft Academic Search

The use of conventional dental implants for orthodontic anchorage is limited by their large size. The purpose of this study was to quantify the histomorphometric properties of the bone-implant interface to analyze the use of small titanium screws as an orthodontic anchorage and to establish an adequate healing period. Overall, successful rigid osseous fixation was achieved by 97% of the

T. Deguchi; T. Takano-Yamamoto; R. Kanomi; J. K. Hartsfield; W. E. Roberts; L. P. Garetto

2003-01-01

314

The Influence of Rotor Deflection upon Screw Compressor Performance  

Microsoft Academic Search

SUMMARY The compression process within screw compressors induces large pressure and temperature changes that cause the rotors to deform. To determine this effect, a 3-D numerical method has been developed to calculate flow and deformation simultaneously. This comprises a mathematical procedure to generate a numerical grid for both the solid and fluid domains, in the form of a computer program

Ahmed Kovacevic; Ian K. Smith

315

Cooling of oil injected screw compressors by oil atomisation  

Microsoft Academic Search

This paper addresses the effect of oil atomisation in an oil-injected screw compressor. A test rig was built to assess the performance of different types of atomisers. Atomisers varying from fine atomisation to coarse atomisation were tested. Experiments on the test rig show that lowering the oil droplet diameter results in a considerably higher heat transfer. Growing oil flow rate,

M. De Paepe; W. Bogaert; D. Mertens

2005-01-01

316

Retrofit 'N' Rotors for Efficient Oil-Flooded Screw Compressors  

Microsoft Academic Search

The market for twin screw compressors is highly competitive, especially in compressed air and refrigeration systems, and new designs are continually being introduced which are more efficient and cost effective than their predecessors. However, because of the high cost of development of new machines, manufacturers seek to maintain their existing designs for as long as possible. Closer study of many

N. Stosic; I. K. Smith; A. Kovacevic; K. Venumadhav

2000-01-01

317

The CFD Analysis of a Screw Compressor Suction Flow  

Microsoft Academic Search

Dynamic flow losses in the suction chamber play a very important if not the main role in the efficiency decrease in screw compressors. The design of these machines, together with the accounting of flow losses and how to reduce them, is still based only on the simple analysis. Since Computational Fluid Mechanics offers today a more accurate estimation of the

N. Stosic; A. Kovacevic; I. K. Smith

2000-01-01

318

levelling screws; the disk is then raised until the small  

E-print Network

and the operation is repeated until the zero does coin- cide with .... It is then washed several times in pure water and cried .... ing hole and thread into which the handle 5 is not screwed. .... same way as shot, except the test of strength by drop-.

319

Twin-screw extrusion of ‘Pesta’-encapsulated biocontrol agents  

Microsoft Academic Search

‘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),

D. J. Daigle; W. J. Connick; C. D. Boyette; M. P. Lovisa; K. S. Williams; M. Watson

1997-01-01

320

Cervical stability with lateral mass plating  

Microsoft Academic Search

Purpose of study: The purpose of this study was to determine if there is a significant difference in stability between cervical spines instrumented with lateral mass plates affixed with unicortical versus bicortical Magerl screws.Methods used: Eleven human, cadaveric, cervical spines were harvested and radiographed, and all soft tissues except for supporting ligamentous structures were removed. Segments C3 through C5 were

Anthony Muffoletto; Walt Simmons; Jinping Yang; Kim Garges; Mukta Vadhva; Alexander Hadjipavlou

2002-01-01

321

Maxillo Mandibular Fixation in Edentulous Scenarios: Combined MMF Screws and Gunning Splints.  

PubMed

A fracture of the maxillary or mandibular bone requires the afflicted to undergo a maxillo mandibular fixation for the establishment of pre traumatic occlusion. This process is quiet tedious and consumes a considerable period of time before any surgical procedure can commence. Such a situation can be complicated in case the individual with maxillomandibular fracture has sparse or absent dentition; for such cases a splint is fabricated or an erstwhile existing denture is used for maintaining a vertical jaw proportion. Stabilizing such splints to the jaw requires various invasive approaches that can bring into harm's way, adjacent soft tissue vital structures. We describe here an innovative technique combining the time tested method of the "gunning splint" and the advanced minimally invasive MMF screws for obtaining closed reduction in edentulous jaw fractures. PMID:24822016

Chaudhary, Zainab; Sharma, Rakesh; Krishnan, Sriram

2014-06-01

322

Analysis of load redistribution in diaphyseal bone following staged screw removal from bone plates  

E-print Network

, overall imply on average that there is a trend towards reduced bone loading as screws are removed from 30 the plate. Similarly inconclusive results occur at lower loads. Oddly, the greatest strain in all instances appears in the most anterior gages... screws when screws 1 and 6 are removed and anterior to the first screw when screws 2, 3, and 4 are removed. The loading of the bone in the anterior regions is probably due to the complex geometry of the bone. The femoral head and anterior bend...

Nixon, Joseph Craig

1987-01-01

323

The improvement of screw compressor performance using a newly developed rotor profile  

SciTech Connect

An oil-compression phenomenon occurs at two portions of a conventional oil injected screw compressor that degrades the isothermal efficiency of the screw compressor. Hence a new screw rotor profile and lubricant have been developed in order to avoid the above oil-compression phenomena. Mycom and Fermi National Accelerator Laboratory have measured the performance of a new Mycom compound type screw compressor 2016C using the new profile rotors and the new lubricant. In the experiments, a 33% enhancement rate in the isothermal efficiency of the new screw compressor installed in Fermilab was achieved.

Kishi, Takayuki; Nishio, Toshio; Matsui, Akira; Ino, Nobumi [Mayekawa Mfg. Co. Ltd., Ibaraki (Japan)

1994-12-31

324

Covering the Screw-Access Holes of Implant Restorations in the Esthetic Zone: A Clinical Report  

PubMed Central

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

Saboury, Abolfazl; Gooya, Ali

2014-01-01

325

Maxillary expansion with the memory screw: a preliminary investigation  

PubMed Central

Objective The purpose of this study was to investigate the effects of a newly developed rapid maxillary expansion screw-the memory screw-over 6 months. Methods Five subjects, aged between 11.7 and 13.75 years, were enrolled in this study. All subjects underwent placement of a maxillary expansion appliance containing superelastic nickel-titanium open-coil springs in its screw bed. The parents of the patients and/or the patients themselves were instructed to activate the expansion screw by 2 quarter-turns 3 times a day (morning, midday, and evening; 6 quarter-turns a day). The mean expansion period was 7.52 ± 1.04 days. Dentoskeletal effects of the procedure, including dentoalveolar inclination, were evaluated. Measurements of all the parameters were repeated after 6 months of retention in order to check for relapse. Results Sella-Nasion-A point (SNA) and Sella-Nasion/Gonion-Menton angles increased, and Sella-Nasion-B point (SNB) angle decreased in all the subjects during the expansion phase. However, they approximated to the initial values at the end of 6 months. On the other hand, the increments in maxillary apical base (Mxr-Mxl) and intermolar widths was quite stable. As expected, some amount of dentoalveolar tipping was observed. Conclusions The newly developed memory expansion screw offers advantages of both rapid and slow expansion procedures. It widens the midpalatal suture and expands the maxilla with relatively lighter forces and within a short time. In addition, the resultant increments in the maxillary apical base and intermolar width remained quite stable even after 6 months of retention. PMID:23112935

Halicio?lu, Koray; Kiki, Ali

2012-01-01

326

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)

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)

De Bothezat, George

1920-01-01

327

Finite element analysis of Stryker Xia pedicle screw in artificial bone samples with and without supplemental cement augmentation.  

PubMed

A validated, using in vitro biomechanical testing, finite element model was used to evaluate the affects of (1) cement augmentation and (2) an intact posterior cortex in osteoporotic bone. The presence of augmentation and/or a posterior cortical cortex increased the stabilization of the pedicle screw 2-5 fold. Placement of cement influenced failure load and toggle; with distal placement having the largest increase in failure load and decrease in cephalad-caudad toggle. The presence of posterior cortex caused a decrease in the amount of toggle, a proximal shift of the center of rotation and an increase in the maximum failure force. PMID:24980259

Pfeiffer, Ferris M; Choma, Theodore J; Kueny, Rebecca

2015-10-01

328

Superior fixation of pegged trabecular metal over screw-fixed pegged porous titanium fiber mesh  

PubMed Central

Background and purpose Lasting stability of cementless implants depends on osseointegration into the implant surface, and long-term implant fixation can be predicted using radiostereometric analysis (RSA) with short-term follow-up. We hypothesized that there would be improved fixation of high-porosity trabecular metal (TM) tibial components compared to low-porosity titanium pegged porous fiber-metal (Ti) polyethylene metal backings. Methods In a prospective, parallel-group, randomized unblinded clinical trial, we compared cementless tibial components in patients aged 70 years and younger with osteoarthritis. The pre-study sample size calculation was 22 patients per group. 25 TM tibial components were fixed press-fit by 2 hexagonal pegs (TM group) and 25 Ti tibial components were fixed press-fit and by 4 supplemental screws (Ti group). Stereo radiographs for evaluation of absolute component migration (primary effect size) and single-direction absolute component migration (secondary effect size) were obtained within the first postoperative week and at 6 weeks, 6 months, 1 year, and 2 years. American Knee Society score was used for clinical assessment preoperatively, and at 1 and 2 years. Results There were no intraoperative complications, and no postoperative infections or revisions. All patients had improved function and regained full extension. All tibial components migrated initially. Most migration of the TM components (n = 24) occurred within the first 3 months after surgery whereas migration of the Ti components (n = 22) appeared to stabilize first after 1 year. The TM components migrated less than the Ti components at 1 year (p = 0.01) and 2 years (p = 0.004). Interpretation We conclude that the mechanical fixation of TM tibial components is superior to that of screw-fixed Ti tibial components. We expect long-term implant survival to be better with the TM tibial component. PMID:21434781

2011-01-01

329

Evaluation of different screw fixation techniques and screw diameters in sagittal split ramus osteotomy: finite element analysis method.  

PubMed

Sagittal split ramus osteotomy (SSRO) is used for correction of numerous congenital or acquired deformities in facial region. Several techniques have been developed and used to maintain fixation and stabilisation following SSRO application. In this study, the effects of the insertion formations of the bicortical different sized screws to the stresses generated by forces were studied. Three-dimensional finite elements analysis (FEA) and static linear analysis methods were used to investigate difference which would occur in terms of forces effecting onto the screws and transmitted to bone between different application areas. No significant difference was found between 1·5- and 2-mm screws used in SSRO fixation. Besides, it was found that 'inverted L' application was more successful compared to the others and that was followed by 'L' and 'linear' formations which showed close rates to each other. Few studies have investigated the effect of thickness and application areas of bicortical screws. This study was performed on both advanced and regressed jaws positions. PMID:24889187

Sindel, A; Demiralp, S; Colok, G

2014-09-01

330

Is a single anterolateral screw-plate fixation sufficient for the treatment of spinal fractures in the thoracolumbar junction? A Biomechanical in vitro Investigation  

Microsoft Academic Search

Controversy exists about the indications, advantages and disadvantages of various surgical techniques used for anterior interbody fusion of spinal fractures in the thoracolumbar junction. The purpose of this study was to evaluate the stabilizing effect of an anterolateral and thoracoscopically implantable screw-plate system. Six human bisegmental spinal units (T12–L2) were used for the biomechanical in vitro testing procedure. Each specimen

Ulrich Schreiber; Tibor Bence; Thomas Grupp; Erwin Steinhauser; Thomas Mückley; Wolfram Mittelmeier; Rudolf Beisse

2005-01-01

331

Impact of posterior tibial nail malpositioning on iatrogenic injuries by distal medio-lateral interlocking screws. A cadaveric study on plastinated specimens.  

PubMed

In intramedullary tibial nailing, multi-planar locking makes stabilization of proximal and distal metaphyseal fractures possible. A known complication in intramedullary nailing of the tibia is iatrogenic injury to neuro-vascular structures caused by the insertion of locking screws. As shown in previous studies, the distal positioning of the nail is important, as it determines the course of the locking bolts. The goal of the present study was to display the consequences of posterior nail malpositioning with respect to the safety of the distal medio-lateral locking screws and the available options. Human cadaveric legs were plastinated according to the sequential plastination technique after intramedullary nailing of the tibia and were then cut transversely. The tibial nails were placed centrally or posteriorly. Macroscopic analysis showed a distinct drawback of posterior nail positioning, with diminished options for the placement of the locking screws and thereby a risk of damaging the anterior and posterior neuro-vascular bundles by distal medio-lateral locking screws. PMID:23409576

Wegmann, Kilian; Burkhart, Klaus Josef; Buhl, Jörg; Gausepohl, Thomas; Koebke, Jürgen; Müller, Lars Peter

2012-12-01

332

Cannulated screw fixation of Jones fifth metatarsal fractures: a comparison of titanium and stainless steel screw fixation.  

PubMed

The classic Jones fracture involves the fifth metatarsal at the level of the proximal diaphyseal-metaphyseal junction. The mainstay of surgical treatment for the Jones fracture is intramedullary screw fixation. There is no consensus of the type or material of screw that should be used. The purpose of this retrospective cohort study was to test the hypothesis that there is no clinical difference in the incidence of healing, or complications, when comparing stainless steel to titanium cannulated screws used in Jones fracture open-reduction internal fixation (ORIF). Data were collected on a total of 53 patients (fractures) that were fixed with either cannulated titanium screws (Ti group) or cannulated stainless steel screws (SS group). The postoperative protocol was standardized. The mean time to radiographic union was 11.7 ± 5.1 weeks in the Ti group and 13.4 ± 5.7 weeks in the SS group (P = .333). The overall union rate for the Ti group was 36/37 (97%) and 14/16 (88%) in the SS group (P = .213). Complications were rare in both groups, and the prevalence was not statistically significantly different (P > .05). There was 1 patient with an asymptomatic radiographic nonunion in the Ti group, and this patient elected not to undergo revision. There were 2 nonunions in the SS group. One was revised and went on to heal and the other is awaiting revision. Our study has demonstrated the decision to use stainless steel or titanium can be left to patient constraints, such as allergies, or physician preference without compromising the clinical result. PMID:21354005

DeVries, J George; Cuttica, Daniel J; Hyer, Christopher F

2011-01-01

333

Handbook on dynamics of jointed structures.  

SciTech Connect

The problem of understanding and modeling the complicated physics underlying the action and response of the interfaces in typical structures under dynamic loading conditions has occupied researchers for many decades. This handbook presents an integrated approach to the goal of dynamic modeling of typical jointed structures, beginning with a mathematical assessment of experimental or simulation data, development of constitutive models to account for load histories to deformation, establishment of kinematic models coupling to the continuum models, and application of finite element analysis leading to dynamic structural simulation. In addition, formulations are discussed to mitigate the very short simulation time steps that appear to be required in numerical simulation for problems such as this. This handbook satisfies the commitment to DOE that Sandia will develop the technical content and write a Joints Handbook. The content will include: (1) Methods for characterizing the nonlinear stiffness and energy dissipation for typical joints used in mechanical systems and components. (2) The methodology will include practical guidance on experiments, and reduced order models that can be used to characterize joint behavior. (3) Examples for typical bolted and screw joints will be provided.

Ames, Nicoli M.; Lauffer, James P.; Jew, Michael D.; Segalman, Daniel Joseph; Gregory, Danny Lynn; Starr, Michael James; Resor, Brian Ray

2009-07-01

334

Double-sided fiber laser beam welding process of T-joints for aluminum aircraft fuselage panels: Filler wire melting behavior, process stability, and their effects on porosity defects  

NASA Astrophysics Data System (ADS)

Aluminum alloy T-joints for aircraft fuselage panels were fabricated by double-sided fiber laser beam welding with filler wire, and the influence of the wire feeding posture on the welding process stability was investigated. A CMOS high speed video system was used to observe the wire melting behavior and the weld pool dynamics in real time during the welding process by using a bandpass red laser with an emission wavelength of 808 nm as backlight source to illuminate the welding zone. The weld porosity defects were analyzed by X-ray radiography. The effects of wire feeding posture on the wire melting behavior, process stability, and porosity defects were investigated. The experimental results indicated that three distinct filler material transfer modes were identified under different wire feeding positions: liquid bridge transfer mode, droplet transfer mode, and spreading transfer mode. The liquid bridge transfer mode could guarantee a stable welding process, and result in the lowest porosity. Compared with wire feeding in the leading direction, the process was not stable and porosity increased when wire feeding in the trailing direction. Increased in the wire feeding angle was disadvantage for pores to escape from the weld molten pool, meanwhile, it made the welding process window smaller due to increasing the centering precision requirement for adjusting the filler wire.

Tao, Wang; Yang, Zhibin; Chen, Yanbin; Li, Liqun; Jiang, Zhenguo; Zhang, Yunlong

2013-11-01

335

Structure of screw dislocation core in Ta at high pressure  

SciTech Connect

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.

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

336

Screw pumps provide high efficiency in transport of Orinoco bitumen  

SciTech Connect

One of the world`s largest known deposits of extra natural bitumen is located in the Orinoco River basin of eastern Venezuela. Production and transportation of an emulsion of bitumen and water is one of the major projects being directed by Petroleos de Venezuela S.A. This paper reviews the pump selection options considered in transporting this bitumen to a viable processing facility. The three pump types evaluated were centrifugal, reciprocating, or rotary screw. Performance and cost parameters are evaluated and the screw pump was determined to be the most economical, high performance choice. The paper goes on to describe the installation of the main transport lines and efficiency of these new pumps.

Brennan, J.R. [IMO Industries, Inc., Monroe, NC (United States)

1995-03-01

337

Detecting thrust bearing failure within a screw compressor  

SciTech Connect

A 3 1/2 mile ring of over 1000 superconducting magnets are needed to focus and drive the world`s highest energy particle smasher. 24 Refrigerators supply liquid helium to the magnets; 34 high pressure oil flooded screw compressors supply 285 psig helium gas to the refrigerators. The 400 h.p. screws are reliable machines that use 45 gallons of oil per minute to seal and lubricate the rotors, lubricate the bearings, and remove the heat of compression. These machines are spaced out in seven buildings over four miles. A minimum of 28 machines must be operating at all times. A contingent of operators start, stop, and monitor any machine from a distant control room. The 34 compressors have an average of 32,000 hours; 9 machines have over 40,000 hours; the highest is 55,000 hours.

Pallaver, C.

1994-05-01

338

Efficiency study of oil cooling of a screw compressor  

SciTech Connect

One of the major goals of all compressor manufacturers is to design and build as efficient a compressor as possible. In a screw compressor it appears that the way the compressor is cooled can have an effect on the compressor's efficiency. This paper presents experimental data on three different screw compressor cooling methods: Liquid Refrigerant Injection Cooling System; Thermosyphon Cooling System; and Oil Injection System. All tests were conducted on a hot gas bypass system using refrigerant R-22. The data taken shows that the Oil Injection System is slightly better than the other two. These tests should be repeated with a higher oil flow rate and ammonia as the working fluid. 10 figs.

Tree, D.R.; McKellar, M.G. (Purdue Univ., Lafayette, IN (USA). Ray W. Herrick Labs.); Fresco, A. (Brookhaven National Lab., Upton, NY (USA))

1990-01-01

339

Analysis of Eyring-Powell Fluid in Helical Screw Rheometer  

PubMed Central

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

Siddiqui, A. M.; Haroon, T.; Zeb, M.

2014-01-01

340

Joint Projects / Joint Seminars October 2013  

E-print Network

Joint Projects / Joint Seminars October 2013 Information Sheet Bilateral Programs (MoU) ­ Joint Projects (JP) / Joint Seminars (JS) FWF has signed bilateral agreements ­ so called "Memorandums of Understanding" (MoU) ­ with several international partner organisations. These agreements usually aim at jointly

Fuchs, Clemens

341

Screw compressor bearing failure at CO No. 4  

SciTech Connect

This report is a record of a bearing failure observed on a screw compressor which is a mechanical component run continuously in an unattended mode at Fermi National Accelerator Laboratory. It records how this fault was noticed, monitored, and progressed to ultimate machine trip, within the span of one day, and how the protection systems attached to the compressor performed in monitoring the development of this equipment failure.

Pallaver, C.; Cross, T.

1995-04-01

342

Flow and pressure characteristics within a screw compressor  

Microsoft Academic Search

The angle-resolved mean and turbulence characteristics of the axial air flow inside a screw compressor with both male and female rotors have been measured, using a laser Doppler velocimeter (LDV) with high spatial and temporal resolution at different radial and axial locations for speeds of 800-1600 rpm, discharge pressures of 1-1.6 bar and discharge temperatures of 33-90°C. The velocity measurements

D. Guerrato; J. M. Nouri; N. Stosic; C. Arcoumanis

2007-01-01

343

Gear-Cutting Tool for Screw-Compressor Rotors  

Microsoft Academic Search

A built-up hob for a screw-compressor rotor is proposed. The hob is composed of cutter blades and a hob head. The blade is cut out from a tempered planar plate of high speed tool steel by wire-cut electrodischarge machining (EDM). During the wire cutting process, the wire electrode has a fixed angle to ensure both the side and the end

Katsumi Kaneko; Kazumasa Kawasaki; Hisashi Tamura

2001-01-01

344

Investigation of seals with floating rings in a screw compressor  

Microsoft Academic Search

A number of screw compressors (SC) produced in the Soviet Union for air compression to a pressure of 1.5-2.5 kg\\/cm 2 use metallic labyrinth seals. The efficiency of these seals decreases rapidly as discharge pressure increases. Replacing these labyrinth seals by better designs can substantially reduce air leakage through the end seals of the SC and can improve their efficiency.

F. L. Yuditskii; B. L. Grinpress; Yu. L. Semenov

1972-01-01

345

Tibial Lengthening: Extraarticular Calcaneotibial Screw to Prevent Ankle Equinus  

Microsoft Academic Search

Between 2003 and 2006, we used an extraarticular, cannulated, fully threaded posterior calcaneotibial screw to prevent equinus\\u000a contracture in 10 patients (four male and six female patients, 14 limbs) undergoing tibial lengthening with the intramedullary\\u000a skeletal kinetic distractor. Diagnoses were fibular hemimelia (two), mesomelic dwarfism (two), posteromedial bow (one), hemihypertrophy\\u000a (one), poliomyelitis (one), achondroplasia (one), posttraumatic limb-length discrepancy (one), and

Mohan V. Belthur; Dror Paley; Gaurav Jindal; Rolf D. Burghardt; Stacy C. Specht; John E. Herzenberg

2008-01-01

346

Steady-state simulation of screw liquid chillers  

Microsoft Academic Search

In order to predict the performance of screw liquid chillers in a wide range of configuration parameters and operating conditions, a steady-state simulation model is presented, which is suitable for non-economized and economized chillers. The model includes sub-models for key components, such as non-economized compressor, economized compressor, shell-and-tube condenser, expansion valve, and flooded evaporator. Sequential modular method and successive substitution

Long Fu; Guoliang Ding; Zujian Su; Guoquan Zhao

2002-01-01

347

Assembly means for standardized mechanical joint for pipeline appurtenances  

SciTech Connect

This patent describes an improvement in the standardized mechanical joint connection for use on waterworks or gas pipeline appurtenances wherein the shape or dimensions of the body of the appurtenances preclude the insertion and tightening of the standardized T-bolts. The improvement comprises: a. a screw having an externally threaded cylindrical portion, an hexagonally shaped head on one end of the externally threaded cylindrical portion. The hexagonally shaped head has the same dimensions across flats as the standardized nuts. The externally threaded cylindrical portion has length of such dimension that engagement of the externally threaded cylindrical portion with the internal threads of nut means is provided when a gland, gasket, socket, and spigot are contiguous prior to compression of the gasket, and interference with the externally threaded cylindrical portion is prevented when the screw is tightened and the gasket is compressed, and b. the nut means having an internally threaded elongated shape so as to prevent turning during tightening, means to provide linear contact with a standardized mechanical joint bell flange surface. The nut means has adjacent surfaces sloping away from the linear contact so as to provide for axial misalignment of the screw.

Kennedy, H. Jr.

1987-01-20

348

Modelling of the Heating Process in a Thermal Screw  

NASA Astrophysics Data System (ADS)

The procedure of separating efficiently dry-stuff (proteins), fat, and water is an important process in the handling of waste products from industrial and commercial meat manufactures. One of the sub-processes in a separation facility is a thermal screw where the raw material (after proper mincing) is heated in order to melt fat, coagulate protein, and free water. This process is very energy consuming and the efficiency of the product is highly dependent on accurate temperature control of the process. A key quality parameter is the time that the product is maintained at temperatures within a certain threshold. A detailed mathematical model for the heating process in the thermal screw is developed and analysed. The model is formulated as a set of partial differential equations including the latent heat for the melting process of the fat and the boiling of water, respectively. The product is modelled by three components; water, fat and dry-stuff (bones and proteins). The melting of the fat component is captured as a plateau in the product temperature. The model effectively captures the product outlet temperature and the energy consumed. Depending on raw material composition, "soft" or "dry", the model outlines the heat injection and screw speeds necessary to obtain optimal output quality.

Zhang, Xuan; Veje, Christian T.; Lassen, Benny; Willatzen, Morten

2012-11-01

349

Posterior occipito-axial fixation applied C2 laminar screws for pediatric atlantoaxial instability caused by Down syndrome: Report of 2 cases  

PubMed Central

Background Upper cervical spine instability is one of the most critical orthopedic problems in patients with Down syndrome. However, arthrodesis of the upper cervical spine in these patients can be very difficult to achieve and has a high complication rate because of mental retardation and accompanying various medical conditions of the vital organs. Even now, surgeries in such patients, especially pediatric cases, are challenging and the optimal operative procedure remains unsettled. The purpose of this study was to report 2 cases of pediatric atlantoaxial instability due to Down syndrome in which posterior occipito-axial fixation with C2 laminar screws was performed. Methods Case 1 was a girl aged 6 years 10 months who had atlantoaxial rotatory fixation with os odontoideum. Atlantoaxial rotatory fixation was incompletely reduced by halo traction, and it was not maintained without halo-ring and -vest fixation. Posterior occipito-axial fixation with bilateral C2 laminar screws was then performed. Case 2 was a boy aged 10 years 7 months who had atlantoaxial subluxation with os odontoideum. He also had incomplete quadriplegia, so he could neither walk nor have a meal by himself. Posterior occipito-axial fixation with right C2 pedicle and left C2 laminar screws was then carried out. Results In case 1 bone union was obtained at 3 months after surgery and the patient's symptoms were resolved. In case 2 bone union was obtained at 3 months after surgery and the paralysis was improved. Conclusions/level of evidence In cases of atlantoaxial instability due to Down syndrome, symptomatic patients often present between ages 5 and 15 years and mental retardation interferes with postoperative cervical immobilization. C2 laminar screws can be safely applied for the pediatric axis and biomechanically accomplished rigid fixation. The C2 laminar screw is one of the most useful options to achieve stability of the pediatric atlantoaxial complex without the risk of vertebral artery injuries (level IV case series).

Kuroki, Hiroshi; Kubo, Shinichiro; Hamanaka, Hideaki; Chosa, Etsuo

2012-01-01

350

Joint Problems  

MedlinePLUS

... shoulder joint. About 30% of older people have tears in their rotator cuff muscles and tendons, but many have no symptoms. Carpal tunnel syndrome is pressure on a nerve in the wrist and may cause tingling, numbness and pain in the hand. It ... Updated: March 2012 Posted: March 2012

351

The effect of stem material and surface treatment on the torsional stability at the metal-cement interface of upper limb joint replacement systems.  

PubMed

Stem surface treatment and material are two design factors that may affect the onset of implant loosening. For upper limb applications, no known in vitro studies have addressed the role of these two factors on cemented implant stability. Therefore, the purpose of this study was to compare the torsional stability of cemented titanium and cobalt chrome stems with varying surface treatments in vitro. Thirty implant stems of circular cross-section (Ø = 8mm) were machined from cobalt chrome (n = 15) and titanium (n = 15). For each type, stems were subdivided into three groups for application of clinically relevant surface treatments: smooth, sintered beads, or plasma spray. Stems were potted in bone cement, allowed 24 h to cure, and placed in a materials testing machine. Stems were tested under cyclic torsion (1-30 Nm), using a staircase loading protocol. Failure was defined as either the first rapid increase in stem rotation without resistance, or attaining a maximum torque of 30 Nm. Implant stems with non-smooth surfaces offered greater resistance to torsion (p < 0.05), with the plasma spray treatment outlasting the beaded and smooth stems (p < 0.05). Titanium offered superior interface strength (p < 0.05) but reduced resistance to motion (p < 0.05) when compared to cobalt chrome. Therefore, these design features should be considered during upper limb implant design. PMID:24644238

Hosein, Yara K; King, Graham J W; Dunning, Cynthia E

2014-08-01

352

Field simulation of axisymmetric plasma screw pinches by alternating-direction-implicit methods  

SciTech Connect

An axisymmetric plasma screw pinch is an axisymmetric column of ionized gaseous plasma radially confined by forces from axial and azimuthal currents driven in the plasma and its surroundings. This dissertation is a contribution to detailed, high resolution computer simulation of dynamic plasma screw pinches in 2-d {ital rz}-coordinates. The simulation algorithm combines electron fluid and particle-in-cell (PIC) ion models to represent the plasma in a hybrid fashion. The plasma is assumed to be quasineutral; along with the Darwin approximation to the Maxwell equations, this implies application of Ampere`s law without displacement current. Electron inertia is assumed negligible so that advective terms in the electron momentum equation are ignored. Electrons and ions have separate scalar temperatures, and a scalar plasma electrical resistivity is assumed. Altemating-direction-implicit (ADI) methods are used to advance the electron fluid drift velocity and the magnetic fields in the simulation. The ADI methods allow time steps larger than allowed by explicit methods. Spatial regions where vacuum field equations have validity are determined by a cutoff density that invokes the quasineutral vacuum Maxwell equations (Darwin approximation). In this dissertation, the algorithm was first checked against ideal MM stability theory, and agreement was nicely demonstrated. However, such agreement is not a new contribution to the research field. Contributions to the research field include new treatments of the fields in vacuum regions of the pinch simulation. The new treatments predict a level of magnetohydrodynamic turbulence near the bulk plasma surface that is higher than predicted by other methods.

Lambert, M.A.

1996-06-01

353

Acromioclavicular joint dislocation: a comparative biomechanical study of the palmaris-longus tendon graft reconstruction with other augmentative methods in cadaveric models  

PubMed Central

Background Acromioclavicular injuries are common in sports medicine. Surgical intervention is generally advocated for chronic instability of Rockwood grade III and more severe injuries. Various methods of coracoclavicular ligament reconstruction and augmentation have been described. The objective of this study is to compare the biomechanical properties of a novel palmaris-longus tendon reconstruction with those of the native AC+CC ligaments, the modified Weaver-Dunn reconstruction, the ACJ capsuloligamentous complex repair, screw and clavicle hook plate augmentation. Hypothesis There is no difference, biomechanically, amongst the various reconstruction and augmentative methods. Study Design Controlled laboratory cadaveric study. Methods 54 cadaveric native (acromioclavicular and coracoclavicular) ligaments were tested using the Instron machine. Superior loading was performed in the 6 groups: 1) in the intact states, 2) after modified Weaver-Dunn reconstruction (WD), 3) after modified Weaver-Dunn reconstruction with acromioclavicular joint capsuloligamentous repair (WD.ACJ), 4) after modified Weaver-Dunn reconstruction with clavicular hook plate augmentation (WD.CP) or 5) after modified Weaver-Dunn reconstruction with coracoclavicular screw augmentation (WD.BS) and 6) after modified Weaver-Dunn reconstruction with mersilene tape-palmaris-longus tendon graft reconstruction (WD. PLmt). Posterior-anterior (horizontal) loading was similarly performed in all groups, except groups 4 and 5. The respective failure loads, stiffnesses, displacements at failure and modes of failure were recorded. Data analysis was carried out using a one-way ANOVA, with Student's unpaired t-test for unpaired data (S-PLUS statistical package 2005). Results Native ligaments were the strongest and stiffest when compared to other modes of reconstruction and augmentation except coracoclavicular screw, in both posterior-anterior and superior directions (p < 0.005). WD.ACJ provided additional posterior-anterior (P = 0. 039) but not superior (p = 0.250) stability when compared to WD alone. WD+PLmt, in loads and stiffness at failure superiorly, was similar to WD+CP (p = 0.066). WD+PLmt, in loads and stiffness at failure postero-anteriorly, was similar to WD+ACJ (p = 0.084). Superiorly, WD+CP had similar strength as WD+BS (p = 0.057), but it was less stiff (p < 0.005). Conclusions and Clinical Relevance Modified Weaver-Dunn procedure must always be supplemented with acromioclavicular capsuloligamentous repair to increase posterior-anterior stability. Palmaris-Longus tendon graft provides both additional superior and posterior-anterior stability when used for acromioclavicular capsuloligamentous reconstruction. It is a good alternative to clavicle hook plate in acromioclavicular dislocation. PMID:18042292

Luis, Guntur E; Yong, Chee-Khuen; Singh, Deepak A; Sengupta, S; Choon, David SK

2007-01-01

354

Investigation of melting in a modular intermeshing co-rotating twin screw extruder  

Microsoft Academic Search

Since the first patent regarding the co-rotating twin screw extruder was published in 1869, the co-rotating twin screw extruder has evolved into a high performance extruder, having self wiping capability, modular screw configuration, starved feed zone, kneading disc block elements, and special mixing devices. For this device, flow studies began in the mid 1960's but melting studies started in the

Ho-Chul Jung

2004-01-01

355

The effect of dynamic behavior on surface roughness of ball screw under the grinding force  

Microsoft Academic Search

The dynamic behavior of a ball screw under a moving grinding force and the resulting ball screw surface roughness are investigated.\\u000a The system includes a ball screw, a headstock, a tailstock, a steady rest, a grinding wheel, and a wheel head. Equations of\\u000a motion of the system are derived through Lagrangian approach combined with global assumed mode method in this

Ting-Nung Shiau; Kuan-Hung Chen; Fu-Ching Wang; Chui-Te Chio; Wei-Chun Hsu

2011-01-01

356

Clinical degradation and biocompatibility of different bioabsorbable interference screws: A report of six cases  

Microsoft Academic Search

The clinical biocompatibility and degradation of bioabsorbable interference screws of different polymer composition is described in this report for six patients who underwent repeat arthroscopy after anterior cruciate ligament (ACL) reconstruction. Bioabsorbable interference screws were used for bone plug fixation of bone—patellar tendon—bone (BPTB) autografts. Poly (L-lactide) (PLLA) interference screws were used in one case, poly (D,L-lactide-co-glycolide) (PDLLA-co-PGA) in two

Andreas C. Stähelin; Andreas Weiler; Hansjörg Rüfenacht; Reinhard Hoffmann; Alfred Geissmann; Richard Feinstein

1997-01-01

357

Magnetic resonance imaging appearance of anterior cruciate ligament reconstruction using Calaxo screws  

Microsoft Academic Search

Bioabsorbable interference screws are commonly used to secure the graft during anterior cruciate ligament (ACL) reconstruction,\\u000a in part because they result in less image degradation on subsequent magnetic resonance imaging (MRI). However, some bioabsorbable\\u000a screws are associated with abnormalities on MRI examination not reported with metallic interference screws. We describe a\\u000a finding on knee MRI examination after ACL reconstruction using

Troy F. Storey; William J. Montgomery; Charles H. Bush; Michael Moser

2011-01-01

358

Hollow Mill for Extraction of Stripped Titanium Screws: An Easy, Quick, and Safe Technique  

PubMed Central

Removal of jammed titanium screws can be difficult due to the problem of stripping of the hexagonal heads of the screws. We present a technique of extraction of stripped screws with the use of a standard 4.5 mm stainless steel hollow mill in a patient of peri-implant fracture of the radius fixed with a titanium locking plate 2 years back. The technique is quick, safe, and cost effective. PMID:25013544

Gupta, Ravi; Singh, Harpreet; Singh, Amit; Garg, Sudhir

2014-01-01

359

Thoracic Aortic Stent-Graft Placement for Safe Removal of a Malpositioned Pedicle Screw  

SciTech Connect

We describe a case of percutaneous placement of a thoracic aortic stent-graft for safe removal of a malpositioned pedicle screw in a 52-year-old man. The patient had undergone posterior thoracic spinal instrumentation for pyogenic spondylitis and spinal deformity 8 months previously. Follow-up CT images showed a malpositioned pedicle screw which was abutting the thoracic aorta at the T5 level. After percutaneous stent-graft placement, the malpositioned pedicle screw was safely and successfully removed.

Hu Hongtao [Henan Tumor Hospital, Department of Radiology (China); Shin, Ji Hoon, E-mail: jhshin@amc.seoul.kr; Hwang, Jae-Yeon; Cho, Young Jun; Ko, Gi-Young; Yoon, Hyun-Ki [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology and Research Institute of Radiology (Korea, Republic of)

2010-10-15

360

Semisolid processing of engineering alloys by a twin-screw rheomoulding process  

Microsoft Academic Search

Based on the extensive experience in injection moulding of polymeric materials, a twin-screw rheomoulding process has been developed in our laboratory for near net-shape production of engineering components. The rheomoulding equipment consists of a liquid metal feeder, a twin-screw extruder with closely intermeshing, self-wiping and co-rotating screws, a shot assembly and a central control unit. The fluid flow in the

S Ji; Z Fan; Mike J Bevis

2001-01-01

361

Effect of bone mineral density and amorphous diamond coatings on insertion torque of bone screws  

Microsoft Academic Search

In this study, the potential of high-quality amorphous diamond (AD) coatings in reducing the torque and failures of bone screws was studied. Torque values were recorded for 32 stainless steel screws, 2.7 or 3.5mm in diameter and 60mm in length. Half of the screw sets were coated with the AD coating before installing in predrilled holes of human cadaveric femoral

Arto Koistinen; Seppo S. Santavirta; Heikki Kröger; Reijo Lappalainen

2005-01-01

362

Use of a locking reconstruction bone plate\\/screw system for mandibular surgery  

Microsoft Academic Search

Purpose: This study examined the use of a locking reconstruction bone plate\\/screw system for use in mandibular surgery.Patients and Methods: All patients treated with a locking reconstruction bone plate\\/screw system for fractures of the mandible or continuity defects in an 18-month period were prospectively studied. Ease of use of the locking plate\\/screw system, characteristics of the fractures\\/defects, and complications were

Alan S Herford; Edward Ellis

1998-01-01

363

CALAXO® Osteoconductive Interference Screw: The Value of Post-Market Surveillance  

PubMed Central

The CALAXO® osteoconductive interference screw was recalled in August 2007 due to reports of increased numbers of postoperative complications associated with screw swelling and prominence leading to the need for surgical debridement. This study reviews complications associated with CALAXO® screw use in a consecutive cohort of patients undergoing anterior cruciate ligament reconstruction surgery by the senior author at our institution. Over a 12 month period, 226 CALAXO® interference screws, either of 20mm length or 25mm length, were implanted in 112 patients, and postoperative complications were noted. The 25mm tibial screw was over 5 times (RR 5.2, 95% CI 1.8 to 15.3) more likely to be prominent than the 20mm screw (p-value = 0.002). Four surgical debridements were required in the 25mm tibial screw group; none were required in the 20mm group. We hypothesize that the inability to bury the longer screw length into the bone tunnel is associated with postoperative complications associated with the CALAXO® screw. PMID:20727309

Cox, Charles L.; Homlar, Kelly C.; Carey, James L.; Spindler, Kurt P.

2013-01-01

364

Development and Testing of a Screw Compressor Supermarket Refrigeration System: Phase II, Final Report.  

SciTech Connect

A laboratory prototype screw compressor refrigeration system was designed, fabricated and tested under various evaporator and ambient conditions. The design is based on a Dunham-Bush vertical hermetic screw compressor and other standard refrigeration components. Results indicate that a screw compressor rack with vapor injection can increase the thermodynamic efficiency of low temperature refrigeration in supermarkets by 20 to 28% compared to multiple reciprocating compressor racks. The payback period of the screw compressor refrigeration system relative to multiple reciprocating compressor systems is 1.1 to 1.5 years and the net present value savings range from 15 to 22 thousand dollars.

Borhanian, H. Hamed; Toscano, William M.; Lee, Kang P.

1987-02-01

365

A mechanical evaluation of pre-tapped and self-tapped screws in small bones.  

PubMed

The purpose of this study was to compare the holding powers of 2.7 mm pre-tapped and self-tapped screws placed closely together and tightened in small bones. Pairs of metatarsals were collected from healthy, skeletally mature Greyhounds and part of a 2.7 mm dynamic compression plate was fixed to the dorsal surface of each bone using three 2.7 mm screws. Identical screws were used throughout but only one of each pair of bones had threads pre-cut using a tap prior to insertion. All of the screws were tightened before the constructs were mounted in a materials testing machine and the centrally placed screw was loaded incrementally until failure. Load-deformation curves were plotted and yield point, ultimate load to failure, stiffness and energy prior to yield point were measured. Mean values were recorded for each parameter and Student's T-test was used to test the null hypothesis that there is no difference in holding power between pre-tapped and self-tapped screws. Significant mechanical differences were not found between pre-tapped and self-tapped screws placed closely together and tightened into small bones. Self-tapped screws can be considered for use in small animal surgery even when multiple screws are to be placed closely together in relatively small pieces of bone. PMID:18038003

Bell, J C; Ness, M G

2007-01-01

366

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

PubMed

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

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

2011-11-01

367

Accuracy of Free Hand Pedicle Screw Installation in the Thoracic and Lumbar Spine by a Young Surgeon: An Analysis of the First Consecutive 306 Screws Using Computed Tomography  

PubMed Central

Study Design A retrospective cross-sectional study. Purpose The purpose of this study is to evaluate the accuracy and safety of free-hand pedicle screw insertion performed by a young surgeon. Overview of Literature Few articles exist regarding the safety of the free-hand technique without inspection by an experienced spine surgeon. Methods The index surgeon has performed spinal surgery for 2 years by himself. He performed fluoroscopy-assisted pedicle screw installation for his first year. Since then, he has used the free-hand technique. We retrospectively reviewed the records of all consecutive patients undergoing pedicle screw installation using the free-hand technique without fluoroscopy in the thoracic or lumbar spine by the index surgeon. Incidence and extent of cortical breach by misplaced pedicle screw was determined by a review of postoperative computed tomography (CT) images. Results A total of 36 patients received 306 free-hand placed pedicle screws in the thoracic or lumbar spine. A total of 12 screws (3.9%) were identified as breaching the pedicle in 9 patients. Upper thoracic spine was the most frequent location of screw breach (10.8%). Lateral breach (2.3%) was more frequent than any other direction. Screw breach on the right side (9 patients) was more common than that on the left side (3 patients) (p<0.01). Conclusions An analysis by CT scan shows that young spine surgeons who have trained under the supervision of an experienced surgeon can safely place free-hand pedicle screws with an acceptable breach rate through repetitive confirmatory steps. PMID:24967036

Lee, Chang-Hyun; Kim, Yongjung J; Kim, Ki-Jeong; Jahng, Tae-Ahn; Kim, Hyun-Jib

2014-01-01

368

Management of acromioclavicular joint injuries.  

PubMed

Acromioclavicular joint injuries are among the most common shoulder girdle injuries in athletes and most commonly result from a direct force to the acromion with the arm in an adducted position. Acromioclavicular joint injuries often present with associated injuries to the glenohumeral joint, including an increased incidence of superior labrum anterior posterior (SLAP) tears that may warrant further evaluation and treatment. Anteroposterior stability of the acromioclavicular joint is conferred by the capsule and acromioclavicular ligaments, of which the posterior and superior ligaments are the strongest. Superior-inferior stability is maintained by the coracoclavicular (conoid and trapezoid) ligaments. Type-I or type-II acromioclavicular joint injuries have been treated with sling immobilization, early shoulder motion, and physical therapy, with favorable outcomes. Return to activity can occur when normal shoulder motion and strength are obtained and the shoulder is asymptomatic as compared with the contralateral normal extremity. The management of type-III injuries remains controversial and is individualized. While a return to the previous level of functional activity with nonsurgical treatment has been documented in a number of case series, surgical reduction and coracoclavicular ligament reconstruction has been associated with a favorable outcome and can be considered in patients who place high functional demands on their shoulders or in athletes who participate in overhead sports. Surgical management is indicated for high-grade (?type IV) acromioclavicular joint injuries to achieve anatomic reduction of the acromioclavicular joint, reconstruction of the coracoclavicular ligaments, and repair of the deltotrapezial fascia. Outcomes after surgical reconstruction of the coracoclavicular ligaments have been satisfactory with regard to achieving pain relief and return to functional activities, but further improvements in the biomechanical strength of these constructs are necessary to avoid loss of reduction and creep with cyclic loading. PMID:24382728

Li, Xinning; Ma, Richard; Bedi, Asheesh; Dines, David M; Altchek, David W; Dines, Joshua S

2014-01-01

369

Biocompatibility of ultra-high molecular weight polyethylene (UHMW-PE) stabilized with alpha-tocopherol used for joint endoprostheses assessed in vitro.  

PubMed

Adding the natural antioxidant alpha-tocopherol to ultra-high molecular weight polyethylene (UHMW-PE) can remarkably delay the oxidation of hip cups made thereof. However, alpha-tocopherol is likely to undergo different chemical transformations during manufacturing and sterilization of hip cups than in human metabolism. Therefore, the biocompatibility of the putative transformation products has to be investigated. In-vitro tests with L929 mice fibroblast-cells gave no evidence for cytotoxicity. To further ensure the biocompatibility, in-vitro tests with human cells were carried out in this study. Two different human cell lines, one adherent cell line, HF-SAR, and one suspension culture, GSJO, were tested on UHMW-PE-tablets (diameter: 15 mm; thickness: 2 mm; processed according to standard procedures for artificial hip-cups) with and without alpha-tocopherol with respect to cell viability, proliferation and morphology by means of cell counting, WSt-1 proliferation assay and scanning electron microscopy. Similar proliferation rates were found with both polyethylene samples. Further, we found intact morphology in light and electron microscopy on each substrate. The morphologic characteristics of skin fibroblasts were not changed by any material. Normal adherence and spreading of the fibroblasts was found on controls of glass, as well as on polystyrene and on stabilized and unstabilized polyethylene. The characteristic behaviour as suspension of the GSJO cells remained unchanged. The mitochondrial activity, as studied by WST-1 cell proliferation reagent, was identical on each substrate during the whole observation period of 7 days. PMID:17277986

Wolf, Christian; Lederer, Klaus; Pfragner, Roswitha; Schauenstein, Konrad; Ingolic, Elisabeth; Siegl, Veronika

2007-06-01

370

Interference screw fixation of cervical grafts. A combined in vitro biomechanical and in vivo animal study.  

PubMed

The dislodgement of an anterior bone graft in the cervical spine is a frequent complication of attempted fusion following discectomy or corpectomy. It has been hypothesized that fixation augmented with interference screws may increase the pullout strength of the construct and decrease the rate of these complications. In vitro mechanical tests and in vivo sheep studies were conducted to compare interference screw fixation methods for enhancing the fixation between the bone graft and the adjacent vertebra. Using human cadaver cervical spines, the anterior pullout strengths of cervical bone grafts were compared using fixation with and without the addition of interference screws for the in vitro mechanical testing. The mean pullout forces for a Smith-Robinson type bone graft alone was 58.1 N (SD 11.4 N); for the graft augmented with two 3.5 mm cancellous bone screws, 153.9 N (58.9 N); and for the graft with four 3.5 mm screws, 217.1 N (SD 69.9 N). The pullout strengths of the two- and four-3.5 mm screw constructs were significantly greater than the strength of the graft alone (P < 0.05). Similarly placed 2.7 mm cortical screws of the same length provided increased pullout strength (123.7 N 38.6 N and 142.5 N 38.2 N for two- and four-screw constructs, respectively); however, in comparison to the graft alone, these differences were not statistically significant. For both screw types, the four-screw fixations were stronger than the two-screw fixations, although these differences were not statistically significant. For the in vivo portion of the study, a single-level anterior cervical discectomy and fusion were performed on 20 sheep.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8367782

Vazquez-Seoane, P; Yoo, J; Zou, D; Fay, L A; Fredrickson, B E; Handal, J C; Yuan, H A; Edwards, W T

1993-06-15

371

Evaluation of mechanical properties of three different screws for rapid maxillary expansion  

PubMed Central

Background The aim of this in vitro study was the evaluation of the mechanical properties the screws for rapid maxillary expansion (RME). Methods Three commercially available screws for RME were tested: Leone A2620; Dentaurum Hyrax; Forestadent Palatal Split Screw. All expansion screws were 10 mm in size. For the evaluation of mechanical properties, the screws for RME were adjusted using the same maxillary dental model. An Instron 3365 testing machine with a load cell of 5 kN recorded the forces released by the screws at different amounts of activation (1, 5, 10, 15 and 20 quarters of a turn). Each type of screw was tested 10 times. Comparisons between the forces released by the different types of screws at different amounts of activation were carried out by means of analysis of Kruskal-Wallis test with post-hoc test di Tukey (P?screws about 16 kg. Both the A2620 and Hyrax expanders showed significantly greater amounts of forces at all the different amounts of activations with respect to the Palatal Split screw. Conclusions All tested devices showed the capability of developing expansion forces (16-20 kg) adequate for RME. The A2620 and Hyrax expanders showed a greater level of rigidity than the Palatal Split screw. PMID:24330632

2013-01-01

372

Load transfer in Christensen(®) TMJ in alloplastic total joint replacement for two different mouth apertures.  

PubMed

This study analyses load transfer in the fossa component based on two numerical models of total temporomandibular joint (TMJ) implants for two mouth openings. The TMJ articulation is a very complex system with muscles, ligaments and cartilage. Until now, studies of TMJ implants have analysed only condylar behaviour. The finite element models were constructed based on CT scans of a cadaveric mandible and cranium, considering the bone geometry and position. The influence of five principal muscle actions was simulated for two mouth positions, 5 mm and 15 mm openings at the incisive tooth support. Strain distributions into the surrounding bone tissue were analysed in both models in the condyle and fossa components. The results demonstrate that in Christensen(®) TJR of the temporomandibular joint the fossa component is the more critical part, presenting more stress near the screw holes and contact regions with the cranium. The most critical region is around the first two screws and the least critical is in the condyle component. For the mandible condyle reconstructed with a Christensen(®) prosthesis, the 15 mm mouth opening was more critical, as compression was increased, but for the fossa component the most critical situation occurred with the 5 mm opening. The micromovements observed suggest that the number of screws could be reduced to increase osteointegration of screws in the mandible condyle. PMID:24954763

Ramos, António; Mesnard, Michel

2014-10-01

373

Modeling and control of a twin-screw extruder  

E-print Network

-rotating and co-rotating twin screws (Martelli, 1983). 10 2 A convex function of one variable (Reklaitis et al. , 1983). 19 3 Contour plot for a single quality attribute. 29 4 Contour plot for two quality attributes. 30 5 Contour plot i'or three quality... solution results using difi'erent starting points. If multiple solutions occur, it implies that there are local optima; however, if f(x, I I I )tf(x&)+0-X)f( f(xJ I I I I I fD x, s(I-)t)xj I X, Xx, +(I-X)x Figure 2. A convex function of one...

Richburg, Leslie Leitzy

2012-06-07

374

New Tools for Computational Geometry and Rejuvenation of Screw Theory  

NASA Astrophysics Data System (ADS)

Conformal Geometric Algebraic (CGA) provides ideal mathematical tools for construction, analysis, and integration of classical Euclidean, Inversive & Projective Geometries, with practical applications to computer science, engineering, and physics. This paper is a comprehensive introduction to a CGA tool kit. Synthetic statements in classical geometry translate directly to coordinate-free algebraic forms. Invariant and covariant methods are coordinated by conformal splits, which are readily related to the literature using methods of matrix algebra, biquaternions, and screw theory. Designs for a complete system of powerful tools for the mechanics of linked rigid bodies are presented.

Hestenes, David

375

Arthroscopic-assisted arthrodesis of the trapeziometacarpal joint.  

PubMed

Arthroscopic-assisted surgery of the trapeziometacarpal (TMC) joint has been described before for the treatment of TMC joint arthritis including, debridement, partial or total trapezectomy, and interpositional arthroplasty, but its use for fusion is not reported. TMC joint arthroscopy is a novel technique for arthrodesis which aims to maintain joint stability and strength. We have successfully used this technique to perform fusion of the TMC joint. We think that this would offer the possibility of expanding the indications for TMC joint arthroscopy. PMID:23689861

Yousef, Mohamed A A; Pegoli, Loris

2013-06-01

376

Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws  

Microsoft Academic Search

Internal fixators are a new class of implants designed to preserve the periosteal blood supply of the bone. In contrast to conventional plate fixation in which the screws have spherical heads and are loaded mainly by axial pullout forces, screws in internal fixators are “locked” within the plate and therefore subjected to axial as well as bending loads. In this

J. Seebeck; J. Goldhahn; H. Städele; P. Messmer; M. M. Morlock; E. Schneider

2004-01-01

377

Interference screw divergence in femoral tunnel fixation during endoscopic anterior cruciate ligament reconstruction using hamstring grafts  

Microsoft Academic Search

Purpose:To compare the divergence angles between bioabsorbable interference screws inserted into the femoral tunnel with the screwdriver placed through the anteromedial portal to those inserted with the screwdriver placed through the tibial tunnel and to examine the effect of the femoral tunnel interference screws’ divergence angles on fixation strength of hamstring grafts after anterior cruciate ligament (ACL) reconstruction using hamstring

Christopher M. Miller; James E. Tibone; Michael Hewitt; F. Daniel Kharrazi; Neal S. ElAttrache

2002-01-01

378

A new bioabsorbable interference screw: Preliminary results of a prospective, multicenter, randomized clinical trial  

Microsoft Academic Search

A randomized clinical trial was conducted to compare a bioabsorbable polyglyconate screw (Endo-Fix; Smith & Nephew, Andover, MA) to a metal screw in anterior cruciate ligament reconstruction. A total of 124 patients were operated on and 113 assessed up to 1 year postoperatively. Assessments included a history and physical examination, the IKDC evaluation, and knee arthrometry measurements. No significant differences

Karl-Peter Benedetto; Michael Fellinger; T. E. Lim; Jörg M. Passler; Jaap L. Schoen; W. Jaap Willems

2000-01-01

379

Investigation of a Multiphase Twin-screw Pump Operating at High Gas Volume Fractions  

E-print Network

The use of twin-screw pumps for moving fluids is not new technology but its application to wet gas compression (high gas volume fraction [GVF]) is still considered relatively new. There are many advantages for using twin-screw pumps for oil field...

Kroupa, Ryan Daniel

2012-07-16

380

Calcium phosphate cement augmentation of cancellous bone screws can compensate for the absence of cortical fixation  

E-print Network

Calcium phosphate cement augmentation of cancellous bone screws can compensate for the absence Keywords: Screw fixation Pullout force Calcium phosphate cement Osteoporotic bone a b s t r a c with cement. Previous studies have shown that bone augmentation with Calcium Phosphate (CaP) cement

Guerraoui, Rachid

381

Theoretical and experimental research on the working process of screw refrigeration compressor under superfeed condition  

Microsoft Academic Search

In order to increase the refrigeration capacity and improve the coefficient of performance (COP), an economizer arrangement is used in the refrigeration system with screw refrigeration compressor. In this system, the mid-pressure refrigerant gas from the economizer is injected in the screw refrigeration compressor. So it affects the performance of the compressor. In this paper, the working process of a

Huagen Wu; Jianfeng Li; Ziwen Xing

2007-01-01

382

Mathematical modeling of the working cycle of oil injected rotary twin screw compressor  

Microsoft Academic Search

Oil injected twin-screw air and gas compressors are widely used for medium pressure applications in many industries. Low cost air compressors can be adopted for compression of helium and special gases, leading to significant cost saving. Mathematical analysis of oil injected twin-screw compressor is carried out on the basis of the laws of perfect gas and standard thermodynamic relations. Heat

N. Seshaiah; Subrata Kr. Ghosh; R. K. Sahoo; Sunil Kr. Sarangi

2007-01-01

383

Overall Energy Efficiency of Lubricant-Injected Rotary Screw Compressors and Aftercoolers  

Microsoft Academic Search

This paper shows how to analyze the overall energy efficiency of two typical equipments of compressed air system: lubricant-injected rotary screw compressors and aftercooler. Firstly, air power, a proposed effective tool of weighing energy, is introduced as the quantitative standard of energy in compressed air. Then, compression process of lubricant-injected rotary screw compressors for air production is analyzed deeply and

Yeming Zhang; Maolin Cai; Dewen Kong

2009-01-01

384

Numerical simulation of the extrusion process for food materials in a single-screw extruder  

Microsoft Academic Search

A numerical study of extrusion cooking of starch based materials in a single-screw extruder is carried out. The low moisture levels and high temperatures typically encountered in practical circumstances are considered. The starch conversion process is studied in the rheological region of the extruder which is often the last few turns of the screw, where the material is treated as

Raman V. Chiruvella; Y. Jaluria; Mukund V. Karwe

1996-01-01

385

Experimental analysis of mass transport and mixing in a single screw extruder for semolina dough  

Microsoft Academic Search

In this paper a fluid dynamics analysis of a single screw extruder for semolina dough is reported. Experimental evidence is provided of the absence of a backflow velocity component and that the screw effect on hydrated semolina consists mainly in transporting and compacting the feed semolina particles. The absence of the supposed backflow component is due to the particulate of

Fabrizio Sarghini; Silvana Cavella; Elena Torrieri; Paolo Masi

2005-01-01

386

Cervical Pedicle Screw Fixation: Anatomic Feasibility of Pedicle Morphology and Radiologic Evaluation of the Anatomical Measurements  

PubMed Central

Study Design All parameters were measured manually and with a computed tomography (CT) scanner. For the manual measurements, a Vernier scale instrument was used. Purpose This study evaluates quantitatively pedicles of middle and lower cervical spine (C3 to C7) and to evaluate the possibilities of using these structures as anchors in posterior cervical fusion. Overview of Literature Pedicle screws may be an alternative fixation technique for posterior cervical instrumentation. Methods Twenty-two bony sets of adult cervical spines were studied (110 vertebrae, 220 pedicles) from C3 down to C7. Results CT measurement of cervical pedicles appeared to be accurate and valuable for preoperative planning of cervical pedicle screw instrumentation. The study showed a high correlation between the values obtained by manual and CT measurements of pedicle dimensions. The technical challenge of insertion is the obvious theoretical drawback of the use of cervical pedicle screws. Many technical factors are important to consider, namely, the point of screw entry, the pedicle dimensions, the screw direction according to the pedicle angle and orientation, the screw diameter and length, and the method of screw introduction. Conclusions Transpedicular screw fixation of the cervical spine appears to be promising. Anatomic limitations should be clear to the surgeon. Further clinical and biomechanical studies are needed to settle this technique. PMID:24967041

2014-01-01

387

Foreign Body Reaction After PLC Reconstruction Caused by a Broken PLLA Screw.  

PubMed

Foreign body reactions may occur in patients who receive bioabsorbable implants during orthopedic surgery for fractures and ligament repair. The authors describe a 34-year-old man who presented with a palpable tender mass on the lateral aspect of the left knee of 1 month's duration. He underwent posterior cruciate ligament and posterolateral corner reconstruction 3 years earlier. Physical examination showed a 1×1-cm soft, nontender mass without localized warmth on the lateral epicondyle of the distal femur. Magnetic resonance imaging showed a broken screw fragment surrounded by a cyst-like mass. Under general anesthesia, the surgeon excised the screw fragment and the fibrotic mass, enclosing it in the subcutaneous tissue at the lateral epicondyle, the site at which a poly-L-lactic acid bioabsorbable screw had been inserted to fix the graft for posterolateral corner reconstruction. Histologic evaluation showed a foreign body reaction to the degraded screw particles. To the authors' knowledge, this report is the first description of a patient presenting with a delayed foreign body reaction to a broken poly-L-lactic acid bioabsorbable screw at the lateral femoral epicondyle after posterolateral corner reconstruction. Because delayed foreign body reactions can occur at any site of poly-L-lactic acid bioabsorbable screw insertion, care should be taken to avoid screw protrusion during ligament reconstruction because it can lead to screw breakage and delayed foreign body reaction. [Orthopedics. 2014; 37(12):e1129-e1132.]. PMID:25437089

Kim, Tae-Kwon; Jeong, Tae-Wan; Lee, Dae-Hee

2014-12-01

388

Fixation of dicapitular fractures of the mandibular condyle with a headless bone screw  

Microsoft Academic Search

The fixation of diacapitular fractures of the mandibular condyle utilising a headless cannulated bone screw (Martin HBS®) is described. An open approach was used with primary fixation of the fracture with a K-wire, over which the cannulated screw was inserted. The method and results are described.

R. A. Loukota

2007-01-01

389

The torsional strength of bones with residual screw holes from plates with unicortical and bicortical purchase  

Microsoft Academic Search

Objective. To evaluate the effect of unicortical and bicortical screw holes on residual bone strength by comparing the in vitro torsional strength of cadaveric sheep tibiae with screw holes from plates with unicortical and bicortical purchase relative to each other and to intact bone.Design. The paired tibiae were grouped randomly and torsion tested to failure as follows: Group I —

AR Remiger; T Miclau; RW Lindsey

1997-01-01

390

Histologic study of the bone adjacent to titanium bone screws used for mandibular fracture treatment  

Microsoft Academic Search

Purpose: Titanium miniplates have been widely used in mandibular fracture fixation because of their strength and excellent biocompatibility. However, the condition of the bone adjacent to titanium bone screws has not been clarified. This study histologically examined the bone-screw interface in patients treated for mandibular fractures. Patients and Materials: Specimens were obtained from 14 patients, and the undecalcified sections were

Hisanori Hirai; Akira Okumura; Masaaki Goto; Takeshi Katsuki

2001-01-01

391

Biomechanical comparison between BioScrew and titanium alloy interference screws for bone—patellar tendon—bone graft fixation in anterior cruciate ligament reconstruction  

Microsoft Academic Search

This investigation compared the maximum load at failure of BioScrew (Linvatec Corp, Largo, FL) and titanium alloy interference screw femoral fixation using a human cadaveric model that approximated the anatomical orientation and physiological strain rate of in vivo bone—patellar tendon—bone (BPTB) graft loading following anterior cruciate ligament reconstruction. Eighteen fresh-frozen human BPTB allografts (10-mm wide, 10-mm thick, 25-mm long bone

David N. M. Caborn; William P. Urban; Darren L. Johnson; John Nyland; David Pienkowski

1997-01-01

392

Magnetic resonance imaging analysis of the bioabsorbable Milagro™ interference screw for graft fixation in anterior cruciate ligament reconstruction  

Microsoft Academic Search

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous\\u000a screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years.\\u000a The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek,\\u000a Norderstedt, Germany). The Milagro™ interference screw

K.-H. Frosch; T. Sawallich; G. Schütze; A. Losch; T. Walde; P. Balcarek; F. Konietschke; K. M. Stürmer

2009-01-01

393

Tibial plateau fracture after anterior cruciate ligament reconstruction: Role of the interference screw resorption in the stress riser effect  

Microsoft Academic Search

We report a case of tibial plateau fracture after previous anterior cruciate ligament (ACL) reconstruction using patellar tendon autograft and bioabsorbable screws 4years previously. The fracture occurred through the tibial tunnel. The interference screw had undergone complete resorption and the tunnel widening had increased. The resorption of the interference screw did not simultaneously promote and foster the growth of surrounding

Mathieu Thaunat; Geoffroy Nourissat; Pascal Gaudin; Philippe Beaufils

2006-01-01

394

Comparative endurance testing of the Biomet Matthews Nail and the Dynamic Compression Screw, in simulated condylar and supracondylar femoral fractures  

Microsoft Academic Search

BACKGROUND: The dynamic compression screw is a plate and screws implant used to treat fractures of the distal femur. The Biomet Matthews Nail is a new retrograde intramedullary nail designed as an alternative surgical option to treat these fractures. The objective of this study was to assess the comparative endurance of both devices. METHOD: The dynamic compression screw (DCS) and

Laurence M O'Connor-Read; Jerome A Davidson; Benjamin M Davies; Michael G Matthews; Paul Smirthwaite

2008-01-01

395

Bovine Bone Screws: Metrology and Effects of Chemical Processing and Ethylene Oxide Sterilization on Bone Surface and Mechanical Properties  

Microsoft Academic Search

We assess the effects of chemical processing, ethylene oxide sterilization, and threading on bone surface and mechanical properties of bovine undecalcified bone screws. In addition, we evaluate the possibility of manufacturing bone screws with predefined dimensions. Scanning electronic microscopic images show that chemical processing and ethylene oxide treatment causes collagen fiber amalgamation on the bone surface. Processed screws hold higher

D. P. Haje; J. B. Volpon; C. A. Moro

2009-01-01

396

Knee joint replacement  

MedlinePLUS

Knee joint replacement is surgery to replace a knee joint with a man-made joint. The artificial joint is called a prosthesis . ... cartilage and bone are removed from the knee joint. Man-made pieces are then placed in the ...

397

Accuracy of Intraoperative Computed Tomography–Based Navigation for Placement of Percutaneous Pedicle Screws  

PubMed Central

MISS techniques have gained recent popularity. The proposed benefits of these techniques include reduced tissue trauma, reduced blood loss, less perioperative pain, and a quicker recovery and return to normal activities. The purpose of this study was to evaluate the accuracy of intraoperative computed tomography (CT)-based navigation for placement of percutaneous pedicle screws in a cadaveric model. Outcome measures included accuracy of screw placement. Two cadaveric specimens were utilized. CT images were obtained using an O-Arm (Medtronic, Memphis, Tennessee, United States) and were coupled to the Stealth navigation system (Medtronic). Computer navigation was used for placement of percutaneous pedicle screws. Screws were placed bilaterally from T5 to S1. Postinsertion CT scans were obtained. Pedicle breach was assessed and classified (I: none, II:??4 mm) with direction of breach. Thirty thoracic screws were placed with 3 (10%) medial breaches and 17 (56.7%) lateral breaches (grade III). Of 20 lumbar screws there were 0 medial breaches and 2 (10%) lateral breaches (1 grade III, 1 grade IV). Four sacral screws were placed without breaches. The real-time computer-aided navigation tool (“simulated screw”) was limited in identifying a breach. Manipulation of the surgeon's hand or driver could change the orientation of the navigation tool without changing the screw trajectory. CT-based navigation for percutaneous pedicle screw placement appears safe for the lumbar spine. Lateral thoracic breaches appeared commonly but were not felt to be clinically significant. The 10% rate of medial thoracic breach was concerning, but definitive conclusions could not be made due to the small sample size. PMID:24436858

Eck, Jason C.; Lange, Jeffrey; Street, John; Lapinsky, Anthony; DiPaola, Christian P.

2013-01-01

398

Hydroxyapatite and fluorapatite coatings on dental screws: effects of blast coating process and biological response.  

PubMed

This paper describes the deposition of hydroxyapatite (HA) and fluorapatite (FA) onto titanium dental screws using a novel ambient temperature coating technique named CoBlast. The process utilises a coating medium and a blast medium sprayed simultaneously at the substrate surface. The blast medium was a sintered apatite (sHA) and two particles sizes (<106 and <180 µm) were used to assess their influence on the coating process. The influence of the coating process on the coating composition, coating adhesion, screw morphology and screw microstructure was examined. XRD analysis revealed the coating crystallinity was the same as the original HA and FA feedstock powders. Examining the screw's morphology, the threads of the CoBlasted screws exhibited rounding compared to the unmodified screw. This is due to the abrasive nature of the CoBlast process. The degree of rounding was more significant for the screws blasted with the 180 µm sHA than the 106 µm sHA. The blast media particle size significantly influences the surface roughness of both the substrate and coating and the microstructure of the substrate. The screws did not exhibit any loss of coating after insertion into a model bone material, indicating that the coating was strongly adhered to the substrate. There was no statistically significant difference in cell attachment and cell morphology on the unmodified substrates compared to the coated substrates. In conclusion, the CoBlast process can be used to deposit HA and FA onto complex geometries such as dental screws. The choice of blast medium particle size influences the screws morphology. The coating process does not negatively impact on the cell attachment and morphology in vitro. PMID:25578701

Dunne, Conor F; Twomey, Barry; Kelly, Ciara; Simpson, Jeremy C; Stanton, Kenneth T

2015-01-01

399

Joint x-ray  

MedlinePLUS

X-ray - joint; Arthrography; Arthrogram ... x-ray technologist will help you position the joint to be x-rayed on the table. Once in place, pictures are taken. The joint may be moved into other positions for more ...

400

JOINT SEMINAR FINAL REPORT  

E-print Network

JOINT SEMINAR FINAL REPORT Project number Name of applicant at FWF: __________________________________ Title of the Joint Seminar: ____________________________________________________ Name of the partner): ____________________________________________________ Name of applicant at partner organisation: _______________________ Date and place of Joint Seminar

Fuchs, Clemens

401

Temporomandibular Joint Disorder  

MedlinePLUS

... news feeds delivered directly to your desktop! more... Temporomandibular Joint Disorder Article Chapters Temporomandibular Joint Disorder What ... men. Updated: November 2008 Previous Next Related Articles: Temporomandibular Joint Disorder (TMD) Are You Biting Off More ...

402

Divertor Stabilization in Mirrors  

SciTech Connect

Divertor stabilization is considered as an alternative MHD stability concept for mirror-based plasma confinement systems. The discussed concept is based on thermodynamics and self-organization of magnetized plasmas, contrary to the conventional MHD stabilization, based on the presence of averaged 'magnetic well'. We show that self-organized plasma maintenance near a relaxed marginally-stable state with decreasing pressure profile can be realized in essentially non-paraxial longitudinally linked mirror cells restricted by a joint divertorlike magnetic separatrix with one or several magnetic field nulls at the plasma edge. Brief history, basic principles, and main advantages of the divertor stabilization concept are discussed.

Pastukhov, V.P. [RRC 'Kurchatov Institute' (Russian Federation)

2005-01-15

403

Self-Assembly of Left and Right-Handed Molecular Screws  

PubMed Central

Stereoselectivity is a hallmark of biomolecular processes from catalysis to self-assembly, which predominantly occur between homochiral species. However, both homochiral and heterochiral complexes of synthetic polypeptides have been observed where stereoselectivity hinges on details of intermolecular interactions. This raises the question whether general rules governing stereoselectivity exist. A geometric ridges-in-grooves model of interacting helices indicates that heterochiral associations should generally be favored in this class of structures. We tested this principle using a simplified molecular screw – a collagen peptide triple- helix composed of either L- or D-proline with a cyclic aliphatic side chain. Calculated stabilities of like- and opposite- handed triple-helical pairings indicated a preference for heterospecific associations. Mixing left and right-handed helices drastically lowered solubility, resulting in micron-scale sheet-like assemblies that are one peptide-length thick as characterized with atomic force microscopy. X-ray scattering measurements of inter-helical spacing in these sheets support a tight ridges-in-grooves packing of left and right-handed triple helices. PMID:24283407

Xu, Fei; Khan, I. John; McGuinness, Kenneth; Parmar, Avanish S.; Silva, Teresita; Murthy, Sanjeeva; Nanda, Vikas

2014-01-01

404

Chondrocyte response to in vitro mechanical injury and co-culture with joint capsule tissue  

E-print Network

Acute traumatic joint injury in young adults leads to an increased risk for the development of osteoarthritis (OA) later in life irrespective of surgical intervention to stabilize the injured joint. Although the mechanism ...

Lee, Jennifer H. (Jennifer Henrica)

2005-01-01

405

Computer-assisted periacetabular screw placement: Comparison of different fluoroscopy-based navigation procedures with conventional technique.  

PubMed

The current gold standard for operatively treated acetabular fractures is open reduction and internal fixation. Fractures with minimal displacement may be stabilised by minimally invasive methods such as percutaneous periacetabular screws. However, their placement is a demanding procedure due to the complex pelvic anatomy. The aim of this study was to evaluate the accuracy of periacetabular screw placement assessing pre-defined placement corridors and comparing different fluoroscopy-based navigation procedures and the conventional technique. For each screw an individual periacetabular placement corridor was preoperatively planned using the planning software iPlan CMF(©) 3.0 (BrainLAB). 210 screws (retrograde anterior column screws, retrograde posterior column screws, supraacetabular ilium screws) were placed in an artificial Synbone pelvis model (30 hemipelves) and in human cadaver specimen (30 hemipelves). 2D- and 3D-fluoroscopy-based navigation procedures were compared to the conventional technique. Insertion time and radiation exposure to specimen were also recorded. The achieved screw position was postoperatively assessed by an Iso-C(3D) scan. Perforations of bony cortices or articular surfaces were analysed and the screw deviation severity (difference of the operatively achieved screw position and the preoperatively planned screw position in reference to the pre-defined corridors) was determined using image fusion. Using 3D-fluoroscopy-based navigation, the screw perforation rate (7%) was significantly lower compared to 2D-fluoroscopy-based navigation (20%). For all screws, the deviation severity was significantly lower using a 3D- compared to a 2D-fluoroscopy-based navigation and the conventional technique. Analysing the posterior column screws, the screw deviation severity was significantly lower using 3D- compared to 2D-fluoroscopy-based navigation. However, for the anterior column screw, the screw deviation severity was similar regardless of the imaging method. Despite the advantages of the 3D-fluoroscopy-based navigation, this method led to significantly longer total procedure and fluoroscopic times, and the applied radiation dose was significantly higher. Percutaneous periacetabular screw placement is demanding. Especially for posterior column screws, due to a lower perforation rate and a higher accuracy in periacetabular screw placement, 3D-fluoroscopy-based navigation procedure appears to be the method of choice for image guidance in acetabular surgery. PMID:20728881

Ochs, Björn Gunnar; Gonser, Christoph; Shiozawa, Thomas; Badke, Andreas; Weise, Kuno; Rolauffs, Bernd; Stuby, Fabian Maria

2010-12-01

406

Spacesuit mobility joints  

NASA Technical Reports Server (NTRS)

Joints for use in interconnecting adjacent segments of an hermetically sealed spacesuit which have low torques, low leakage and a high degree of reliability are described. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics. Linkages which restrain the joint from longitudinal distension and a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli are featured. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

Vykukal, H. C. (inventor)

1978-01-01

407

The effect of the combination of locking screws and non-locking screws on the torsional properties of a locking-plate construct.  

PubMed

Little is known about the torsional properties of bone-plate constructs when a combination of locking and non-locking screws have been used. Sixty cadaveric canine femurs were divided into three groups. In the first group, the plate was affixed using three non-locking screws. In the second group, only locking screws were used while a combination of one locking and two non-locking screws were used in the third group. All constructs were subjected to torsion until failure. Torque, angle of torsion, and work were all calculated at the maximum failure point, as well as at five degrees of plastic deformation, which was thought to be more representative of clinical failure. At the maximum failure point, the locking group had significantly higher torque, angle, and work values than the non-locking group. The combination group was intermediate to the two other groups, and significantly differed from the non-locking group in torque, and from the locking group in work. At five degrees of plastic deformation, the locking group required significantly higher torque and work than the non-locking group. The combination group required a significantly higher torque than the non-locking group. This study suggests that a construct composed of all locking screws will fail at a greater torque value, and sustain greater work to failure in torsion compared to a construct composed of all non-locking screws. The addition of a single locking screw to an otherwise non-locking construct will increase the torque at the offset failure point and may be of clinical value in constructs subjected to high torsional loads. PMID:19997676

Gordon, S; Moens, N M M; Runciman, J; Monteith, G

2010-01-01

408

Experimental investigation of granule size and shape dynamics in twin-screw granulation.  

PubMed

A twin-screw granulator (TSG), a promising equipment for continuous high shear wet granulation (HSWG), achieves the desired level of mixing by a combination of the appropriate screw configuration and a suitable set of process settings (e.g. feed rate, screw speed, etc.), thus producing a certain granule size and shape distribution (GSSD). However, the primary sizing and shaping mechanism behind the resulting distribution is not well understood due to the opacity of the multiphase system in the granulator. This study experimentally characterised the GSSD dynamics along the TSG barrel length in order to understand the function of individual screw modules and process settings, as well as their interaction. Particle size analysis of granules collected at the outlet of the TSG suggested significant interaction between the process and screw configuration parameters influencing the heterogeneity in the GSSD. By characterising the samples collected along the screw length, a variable influence of the screw modules at different process conditions was observed. At low liquid-to-solid ratio (L/S), the first kneading module seemed to play a significant role in mixing, whereas the second kneading module was found to be more involved in reshaping the granules. At high L/S and high throughput, aggregation mainly took place in the second kneading module changing the GSSD. The results obtained from this study will be further used for the calibration and validation of a mechanistic model and, hence, support future development of a more detailed understanding of the HSWG process in a TSG. PMID:25234863

Kumar, Ashish; Vercruysse, Jurgen; Bellandi, Giacomo; Gernaey, Krist V; Vervaet, Chris; Remon, Jean Paul; De Beer, Thomas; Nopens, Ingmar

2014-11-20

409

Experimental results of single screw mechanical tests: a follow-up to SAND2005-6036.  

SciTech Connect

The work reported here was conducted to address issues raised regarding mechanical testing of attachment screws described in SAND2005-6036, as well as to increase the understanding of screw behavior through additional testing. Efforts were made to evaluate fixture modifications and address issues of interest, including: fabrication of 45{sup o} test fixtures, measurement of the frictional load from the angled fixture guide, employment of electromechanical displacement transducers, development of a single-shear test, and study the affect of thread start orientation on single-shear behavior. A286 and 302HQ, No.10-32 socket-head cap screws were tested having orientations with respect to the primary loading axis of 0{sup 0}, 45{sup o}, 60{sup o}, 75{sup o} and 90{sup o} at stroke speeds 0,001 and 10 in/sec. The frictional load resulting from the angled screw fixture guide was insignificant. Load-displacement curves of A286 screws did not show a minimum value in displacement to failure (DTF) for 60{sup o} shear tests. Tests of 302HQ screws did not produce a consistent trend in DTF with load angle. The effect of displacement rate on DTF became larger as shear angle increased for both A286 and 302HQ screws.

Lee, Sandwook; Lee, Kenneth L.; Korellis, John S.; McFadden, Sam X.

2006-08-01

410

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

PubMed Central

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

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

2014-01-01

411

The use of bovine screws to promote bone formation using a tibia model in dogs  

PubMed Central

The objective of this study was to evaluate the use of a unique resorbable bovine bone screw, to stimulate bone formation. Bovine bone screws were inserted in the tibia beagle dogs. Each animal received 8 screws, divided into Groups A (screws + no membranes), B (screws + titanium reinforced membranes) and C (bone defects treated with autogenous bone grafts). Animals were sacrificed at 2, 4 and 6 months. New bone was measured with a periodontal probe and reported an average of 7.4 mm in vertical bone gain for Group B, 3.6 mm for Group A and 1.7 mm for Group C. Submission to Kruskal-Wallis test showed statistical differences between groups (p<0,05). Histological examination revealed an intimate contact between the newly formed bone and the resorbing bone screws. Conclusion: Bovine bone screws provide environment for new bone formation and thus may provide an alternative therapy for enhancing bone formation vertically, including for regenerative procedures as well as prior to implant therapy. PMID:23058228

Bianchini, Marco Aurélio; Pontual, Marco Antônio B; Bez, Leonardo; Benfatti, César Augusto M; Boabaid, Fernanda; Somerman, Martha J; Magini, Ricardo S

2013-01-01

412

Biomechanical effects of plate area and locking screw on medial open tibial osteotomy.  

PubMed

Medial open high tibial osteotomy (HTO) has been used to treat osteoarthritis of the medial compartment of the knee. However, weaker plate strength, unstable plate/screw junction and improper surgery technique are highly related to the HTO outcomes. Two ?-shape plates were designed and eight variations (two supporting area ×  four locking stiffness) were compared by finite-element method. The computed tomography-based tibia was reconstructed and both wedge micromotion and implant stresses were chosen as the comparison indices. The construct was subjected to surgical and physiological loads. The medial-posterior region is the most loaded region and the load through the posterior leg is about four times that through the anterior leg. This indicates that the two-leg design can form a force-couple mechanism to effectively reduce the implant stresses. The use of locking screws significantly decrease the screw and hole stresses. However, the extending plate reduces the stresses of screws and holes above the wedge but makes the distal screws and holes much stressed. Wedge micromotion is affected by extending plate rather than locking screw. Three factors contribute to effective stabilisation of unstable HTO wedge: (1) intimate tibia-plate contact at medial-posterior regions, (2) sufficient rigidity at plate-screw junctions and (3) effective moment-balancing design at distal tibia-plate interfaces. PMID:24617553

Luo, Chu-An; Lin, Shang-Chih; Hwa, Su-Yang; Chen, Chun-Ming; Tseng, Ching-Shiow

2015-09-01

413

Design and performance of spinal fixation pedicle screw system.  

PubMed

Pedicle screw-rod bilateral constructions are extensively used in spinal fixation. In this study, the common cause for failure of bilateral constructions has been determined to be the high stress concentration at the rod-setscrew interface. In order to overcome this problem, a design modification has been made by using a supplementary part (shoe) between rod and setscrew. Performance comparison of the conventional design and modified design has been done by conducting static tests. Design modification has resulted in 11%, 27%, 42% and 31% improvements in axial gripping capacity, torsional gripping capacity, flexion/extension resistance and subassembly compression strength, respectively. The most outstanding achievement has been obtained in the fatigue life, which was extended by almost three times. PMID:22888582

Demir, Teyfik; Camu?cuz, Necip

2012-01-01

414

The helical screw expander evaluation project. [for geothermal wells  

NASA Technical Reports Server (NTRS)

A positive-displacement helical-screw expander of the Lysholm type has been adapted for geothermal service and successfully demonstrated in a 50 kW prototype power system. Evaluation of the expander by tests of a new model in a 1 MW power system under wellhead conditions in selected liquid-dominated geothermal fields is proposed. The objectives are to determine the performance characteristics of the expander and power system over a broad range of operating conditions and also to examine the concept of wellhead power plants. Throttling and fractionation of the fluids from the test wells is planned to simulate a wide range of wellhead pressures and steam fractions. Variation in the expander exhaust pressure is also planned. The investigation will include expander efficiency, corrosion, erosion, scale formation and control, and endurance testing. Interaction studies with the wells and an electric grid are also proposed.

Mckay, R. A.

1977-01-01

415

The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching.  

PubMed

Chemical acid etching alone of the titanium implant surface have the potential to greatly enhance osseointegration without adding particulate matter (e.g. TPS or hydroxyapatite) or embedding surface contaminants (e.g. grit particles). The aims of the present study were to evaluate any differences between the machined and dual acid etching implants with the removal torque as well as topographic analysis. A total of 40 custom-made, screw-shaped, commercially pure titanium implants with length of 5 mm and an outer diameter of 3.75 mm were divided into 4 groups, 10 screws in each, and chemical modification of the titanium implant surfaces were achieved using HF and HCl/H(2)SO(4) dual acid etching. The first exposure was to hydrofluoric acid and the second was to a combination of hydrochloric acid and sulfuric acid. The tibia metaphysics was exposed by incisions through the skin, fascia, and periosteum. One implant of each group was inserted in every rabbit, 2 in each proximal tibia metaphysics. Every rabbit received 3 implants with acid etched surfaces and 1 implant with a machined surface. Twelve weeks post-surgically, 7 rabbits were sacrificed, Subsequently, the leg was stabilized and the implant was removed under reverse torque rotation with a digital torque gauge (Mark-10 Corporation, USA) (Fig. 1). Twelve weeks after implant placement, the removal torque mean values were the dual acid etched implants (24%HF+HCl/H(2)SO(4), group C) required a higher average force (34.7 Ncm), than the machined surface implants (group A) (p=0.045) (Mann-Whiteney test). Scanning electron micrographs of acid etching of the titanium surface created an even distribution of very small (1-2 microm) peaks and valleys, while machining of the titanium surface created typical microscopically grooved surface characteristics. Nonetheless, there was no difference in surface topography between each acid etched implant groups. Therefore, chemically acid etching implant surfaces have higher strengths of osseointegration than machined implant surfaces. There is less correlation between removal torque and the difference in HF volume%. PMID:12809791

Cho, Sung-Am; Park, Kyung-Tae

2003-09-01

416

Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel\\/screw ratio. A controlled laboratory study  

Microsoft Academic Search

BACKGROUND: Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces. A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and

Antonio Herrera; Fernando Martínez; Daniel Iglesias; José Cegoñino; Elena Ibarz; Luis Gracia

2010-01-01

417

Alkaline twin-screw extrusion pretreatment for fermentable sugar production  

PubMed Central

Background The inevitable depletion of fossil fuels has resulted in an increasing worldwide interest in exploring alternative and sustainable energy sources. Lignocellulose, which is the most abundant biomass on earth, is widely regarded as a promising raw material to produce fuel ethanol. Pretreatment is an essential step to disrupt the recalcitrance of lignocellulosic matrix for enzymatic saccharification and bioethanol production. This paper established an ATSE (alkaline twin-screw extrusion pretreatment) process using a specially designed twin-screw extruder in the presence of alkaline solution to improve the enzymatic hydrolysis efficiency of corn stover for the production of fermentable sugars. Results The ATSE pretreatment was conducted with a biomass/liquid ratio of 1/2 (w/w) at a temperature of 99°C without heating equipment. The results indicated that ATSE pretreatment is effective in improving the enzymatic digestibility of corn stover. Sodium hydroxide loading is more influential factor affecting both sugar yield and lignin degradation than heat preservation time. After ATSE pretreatment under the proper conditions (NaOH loading of 0.06 g/g biomass during ATSE and 1 hour heat preservation after extrusion), 71% lignin removal was achieved and the conversions of glucan and xylan in the pretreated biomass can reach to 83% and 89% respectively via subsequent enzymatic hydrolysis (cellulase loading of 20 FPU/g-biomass and substrate consistency of 2%). About 78% of the original polysaccharides were converted into fermentable sugars. Conclusions With the physicochemical functions in extrusion, the ATSE method can effectively overcome the recalcitrance of lignocellulose for the production of fermentable sugars from corn stover. This process can be considered as a promising pretreatment method due to its relatively low temperature (99°C), high biomass/liquid ratio (1/2) and satisfied total sugar yield (78%), despite further study is needed for process optimization and cost reduction. PMID:23834726

2013-01-01

418

Flow and pressure characteristics within a screw compressor  

NASA Astrophysics Data System (ADS)

The angle-resolved mean and turbulence characteristics of the axial air flow inside a screw compressor with both male and female rotors have been measured, using a laser Doppler velocimeter (LDV) with high spatial and temporal resolution at different radial and axial locations for speeds of 800-1600 rpm, discharge pressures of 1-1.6 bar and discharge temperatures of 33-90°C. The velocity measurements were performed through a special transparent window fixed near the discharge port. The results confirmed the ability of the LDV technique to characterise the flow inside the compressor working chamber; an angular resolution of 1.5° was able to fully describe the velocity field within the machine. The flow variation between the different working chambers was established as well as the spatial variation of the axial mean velocity and turbulence velocity fluctuation within the working chamber. The effect of discharge port opening on the axial mean and RMS velocities was found to be significant near the leading edge of the rotors causing an increase in the mean and RMS velocities of the order of 4.2Vp in mean (where Vp is the axial pitched velocity) for male rotor and 5.4Vp for, female rotor and this effect is less pronounced on the flow near the root of the rotor. Moreover, to obtain a better understanding of the flow motion, a high sampling rate pressure transducer was used to provide the internal angular static pressure variation. These measurements are used to validate the in-house CFD model of the fluid flow within twin screw compressors which, in turn, allows reliable optimisation of various compressor designs.

Guerrato, D.; Nouri, J. M.; Stosic, N.; Arcoumanis, C.

2007-10-01

419

Use of Screws and Cement in Revision TKA With Primary or Revision Specific Prosthesis With Up to 17Years Followup.  

PubMed

The purpose of this study was to investigate the use for screws and cement, and primary and revision specific prosthesis for revision TKA. Between July 1989 and February 2010, 839 consecutive revision TKAs were performed, with 609 knees meeting inclusion criteria. At 17years followup, Kaplan-Meier survivorship was 0.9859 for revision specific prosthesis with screws and cement, 0.9848 for revision prosthesis with no screws, 0.9118 for primary prosthesis with screws, and 0.9424 for primary prosthesis with no screws. Revision TKAs using screws had greater defects (P<.0001). Use of revision prosthesis along with screws and cement to correct largely defective revision TKAs is highly recommended. PMID:25151092

Berend, Michael E; Ritter, Merrill A; Keating, E Michael; Jackson, Michael D; Davis, Kenneth E; Malinzak, Robert A

2015-01-01

420

Sapphire screws and strength test on them at liquid nitrogen temperature  

NASA Astrophysics Data System (ADS)

We fabricated several sapphire screw threads and performed a strength test on them at the liquid nitrogen temperature of 77 K. The screw threads were subjected to and withstood a 3000 N load. To the best of our knowledge, this is the first strength test of sapphire screw threads at a cryogenic temperature. The result suggests a new way of connecting sapphire components. Although sapphire is already used in many applications, the result may provide a new way to use the material as a structural element in even more applications.

Hirose, Eiichi; Sakakibara, Yusuke; Igarashi, Yukihiko; Ishii, Takashi

2014-10-01

421

Plastification of polymers in twin-screw-extruders: New visualization technic using high-speed imaging  

SciTech Connect

The initial melting of the first granules through plastic energy dissipation (PED) at the beginning of the melting zone, in the co-rotating twin-screw extruder is visualized in this work. The visualization was created through the use of a high speed camera in the cross section of the melting zone. The parameters screw speed, granule-temperature, temperature-profile, type of polymer and back pressure were examined. It was shown that the screw speed and the temperature-profile have significant influence on the rate of initial melting.

Knieper, A., E-mail: Alexander.Knieper@lbf.fraunhofer.de, E-mail: Christian.Beinert@lbf.fraunhofer.de; Beinert, C., E-mail: Alexander.Knieper@lbf.fraunhofer.de, E-mail: Christian.Beinert@lbf.fraunhofer.de [Group Polymer Processing, Division Plastics, Fraunhofer-Institute LBF (Germany)

2014-05-15

422

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

Microsoft Academic Search

Purpose  To assess the midterm results of closed reduction and percutaneous fixation (CRPF) with computed tomography (CT)-guided sacroiliac\\u000a screw fixation in longitudinal posterior pelvic ring fractures.\\u000a \\u000a \\u000a \\u000a Methods  Thirteen patients with 15 fractures were treated. Eleven patients received a unilateral, two a bilateral, screw fixation.\\u000a Twenty-seven screws were implanted. Continuous on-table traction was used in six cases. Mean radiological follow-up was 13\\u000a months.

Augustinus Ludwig Jacob; Peter Messmer; Klaus-Wilhelm Stock; Norbert Suhm; Bernard Baumann; Pietro Regazzoni; Wolfgang Steinbrich

1997-01-01

423

Screw-rotation twinning through helical movement of triple-partials  

NASA Astrophysics Data System (ADS)

By in situ uniaxial-tensile tests with dynamic and atomic scale observation, we report the quantitative investigation of strain-induced deformation-twinning process through incoherent twin boundary propagation in nanocrystalline Au. The consecutive and quantitative strain maps revealed that a strong compressive strain, up to 5.8%, was formed. A screw-rotation twinning mechanism by consecutive and collective screw-rotations of triple-partials along a [111] screw-axis is proposed. This twin generates a macro-strain of 0.707, same as the conventional shear twins, but in a helical manner.

Liu, Pan; Du, Kui; Zhang, Jianxin; Wang, Lihua; Yue, Yonghai; Ma, Evan; Zhang, Yuefei; Zhang, Ze; Chen, Mingwei; Han, Xiaodong

2012-09-01

424

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

PubMed

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

Song, Kwang Soon; Lee, Si Wook

2015-01-01

425

Is polymethyl methacrylate a viable option for salvaging lateral mass screw failure in the subaxial cervical spine?  

PubMed

Study Design?Biomechanical analysis of lateral mass screw pullout strength. Objective?We compare the pullout strength of our bone cement-revised lateral mass screw with the standard lateral mass screw. Methods?In cadaveric cervical spines, we simulated lateral mass screw "cutouts" unilaterally from C3 to C7. We salvaged fixation in the cutout side with polymethyl methacrylate (PMMA) or Cortoss cement (Orthovita, Malvern, Pennsylvania, United States), allowed the cement to harden, and then drilled and placed lateral mass screws back into the cement-augmented lateral masses. On the contralateral side, we placed standard lateral mass screws into the native, or normal lateral, masses and then compared pullout strength of the cement-augmented side to the standard lateral mass screw. For pullout testing, each augmentation group was fixed to a servohydraulic load frame and a specially designed pullout fixture was attached to each lateral mass screw head. Results?Quick-mix PMMA-salvaged lateral mass screws required greater force to fail when compared with native lateral mass screws. Cortoss cement and PMMA standard-mix cement-augmented screws demonstrated less strength of fixation when compared with control-side lateral mass screws. Attempts at a second round of cement salvage of the same lateral masses led to more variations in load to failure, but quick-mix PMMA again demonstrated greater load to failure when compared with the nonaugmented control lateral mass screws. Conclusion?Quick-mix PMMA cement revision equips the spinal surgeon with a much needed salvage option for a failed lateral mass screw in the subaxial cervical spine. PMID:25649421

Gallizzi, Michael A; Kuhns, Craig A; Jenkins, Tyler J; Pfeiffer, Ferris M

2015-02-01

426

Do Newer-Generation Bioabsorbable Screws Become Incorporated into Bone at Two Years After ACL Reconstruction with Patellar Tendon Graft?  

PubMed Central

Background: Bioabsorbable interference screws are used frequently for graft fixation in ACL (anterior cruciate ligament) reconstruction. The resorption properties of many available screws that are marketed as bioabsorbable are not well defined. The CALAXO (Smith & Nephew Endoscopy) and MILAGRO (DePuy Synthes) bioabsorbable screws contain polymers of poly(lactic-co-glycolic acid) (PLGA) plus additives to encourage osseointegration over time. The purpose of this study was to evaluate radiographic and magnetic resonance imaging (MRI) properties and compare patient-reported outcomes at a minimum of two years of follow-up after ACL reconstruction using CALAXO or MILAGRO bioabsorbable interference screws. Methods: A cohort of patients who underwent ACL reconstruction in which the fixation used was either CALAXO or MILAGRO screws returned for repeat radiographs for evaluation of tunnel widening, repeat MRI for evaluation of graft integrity and screw breakdown, and completion of the pain and symptom items of the KOOS (Knee injury and Osteoarthritis Outcome Score) questionnaire. Results: At a mean of three years (range, 2.5 to 4.0 years) after surgery, thirty-one patients with sixty-two CALAXO screws and thirty-six patients with seventy-two MILAGRO screws returned for repeat evaluation. Two blinded, independent reviewers found no significant differences between the two screw types when comparing radiographs for tibial or femoral tunnel widening or MRIs for graft integrity, tibial and femoral foreign body reactions, or femoral screw degradation. Both reviewers found a significant difference between the two screw types when comparing tibial screw degradation properties (p < 0.01). All analyzed CALAXO screws were rated as partially intact or degraded; the MILAGRO screws were more likely to be rated as intact. No significant differences were noted between the two screw types when comparing the two KOOS subscales. Conclusions: CALAXO screws in the tibial tunnel were more likely to be rated as degraded or partially degraded compared with MILAGRO screws at a mean of three years after implantation for ACL reconstruction. Although these newer-generation bioabsorbable screws were designed to promote osseointegration, no tunnel narrowing was noted, and in the majority of cases the remains of the screws were present at approximately three years. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence. Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors. PMID:24500587

Cox, Charles L.; Spindler, Kurt P.; Leonard, James P.; Morris, Brent J.; Dunn, Warren R.; Reinke, Emily K.

2014-01-01

427

Monoaxial Pedicle Screws Are Superior to Polyaxial Pedicle Screws and the Two Pin External Fixator for Subcutaneous Anterior Pelvic Fixation in a Biomechanical Analysis  

PubMed Central

Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 ± 0.113?Nmm monoaxial, 3.638 ± 0.108?Nmm Click-x; 3.634 ± 0.147?Nmm Pangea) than the exfix system (2.882 ± 0.054?Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360?N) than exfixes (160?N) and polyaxial devices which failed if distracted greater than 4?cm (157?N Click-x or 138?N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360?N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems. PMID:24368943

Vaidya, Rahul; Onwudiwe, Ndidi; Roth, Matthew; Sethi, Anil

2013-01-01

428

[Epidemiology, anatomy, biomechanics and imaging of acromioclavicular joint injuries].  

PubMed

Current techniques of acromioclavicular (AC) joint repair primarily focus on the reconstruction of the coracoclavicular (CC) ligaments. However, it is not clear if this approach is sufficient to restore vertical as well as horizontal AC joint stability and kinematics. This review focuses on the epidemiology of AC joint injuries and the coincidence of intra-articular pathologies. Furthermore, the clinically relevant anatomy and the pathomechanism of AC joint instability are described. The biomechanical characteristics of current procedures as they have been revealed by in vitro investigations are summarized. As a basic result, neither selective repair of the CC ligaments nor selective repair of the AC ligaments could be shown to restore both vertical and horizontal joint stability. Similar to the intact ligaments CC repair primarily provides vertical joint stability while AC repair is able to restore horizontal stability. In conclusion a biomechanically effective treatment of AC joint separation should analyze the individual instability pattern in the first step. Therefore, the radiological standard according to Rockwood should be supplemented by specific stress x-rays for quantification of dynamic horizontal AC joint instability. In the second step an adequate surgical treatment considering CC and AC stabilization should be performed meeting the individual patient requirements. PMID:23011261

Wellmann, M; Smith, T

2012-10-01

429

Joint ownership and alienability  

Microsoft Academic Search

Most legal traditions view individual ownership as paradigmatic. Yet most property is jointly owned. This paper analyzes how joint ownership affects alienability by focusing on two fundamental issues raised by joint ownership—the nature of the class of those who may benefit from a joint asset and the nature of the process for making decisions about such an asset. I identify

Clifford G. Holderness

2003-01-01

430

Seismic response of rock joints and jointed rock mass  

SciTech Connect

Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs.

Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

1996-06-01

431

Experimental evaluation of the holding power\\/stiffness of the self-tapping bone screws in normal and osteoporotic bone material  

Microsoft Academic Search

Objective. The goal of this study is to compare the holding power of the self-tapping bone screws in normal and osteoporotic bone materials.Background. Self-tapping screws are increasingly being used in orthopaedic surgery due to their advantages over the other bone screws.Methods. Screws were divided into five groups (six screws per group) based on the depth of insertion in the bone

Suneel Battula; Andrew Schoenfeld; Gregory Vrabec; Glen O Njus

2006-01-01

432

Mechanically working fully-automatic plant for the regeneration of used aluminum cap screws for bottles  

NASA Astrophysics Data System (ADS)

A mechanical separation process for used aluminum cap screws for bottles is described. A prototype separation plant was developed and constructed. Test results indicate low energy consumption, no water pollution, and no emission of noxious vapors.

Schach, V.; Schach, H.

1983-10-01

433

Design and Construction of a High Pressure System for Evaluating Multiphase Twin-Screw Pumps  

E-print Network

Twin-screw pumps are currently sold by manufacturers without adequate data predicting the pump behavior when pumping multiphase mixtures. In light of the fact that pump behavior is known to change significantly under these conditions, a new closed...

Hatch, Theodore Isaac

2013-08-26

434

Three point lead screw positioning apparatus for a cavity tuning plate  

NASA Technical Reports Server (NTRS)

Three lead screws are provided for adjusting the position of a traversing plate. Each of the three lead screws is threaded through a collar that is press fitted through the center of one of three pinion gears. A sun gear meshes with all three pinion gears and transversely moves the three lead screws upon actuation of a drive gear. The drive gear meshes with the sun gear and is driven by a handle or servomotor. When the handle or servomotor rotates the drive gear, the sun gear rotates causing the three pinion gears to rotate, thus, causing transverse movement of the three lead screws and, accordingly, transverse movement of the transversing plate. When the drive gear rotates, the traversing plate is driven in and out of a microwave cavity. Thus, the length or size of the cavity can be tuned while maintaining the traversing plate in an exact parallel relationship with an opposing plate on another end of t