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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.

Spazzin, Aloisio Oro; Henriques, Guilherme Elias Pessanha; de Arruda Nobilo, Mauro Antonio; Consani, Rafael Leonardo Xediek; Correr-Sobrinho, Lourenco; Mesquita, Marcelo Ferraz



Translaminar screw fixation of the lumbar facet joints  

Microsoft Academic Search

Surgical Principle\\u000a \\u000a Posterior fusion of one or two levels of the lumbar spine with arthrodesis of the facet joints using screws. The technique\\u000a has been developed by one of us (Magerl [10–13]). It constitutes an improvement of a technique of transarticular screw fixation\\u000a first described by King in 1944 [7, 8] and modified by Boucher [3] (Figures 1a to 1c).

Bernard Jeanneret; Frank Kleinstiick; Friedrich Magerl



A 2-screw fixation technique for subtalar joint fusion: a retrospective case series introducing a novel 2-screw fixation construct with operative pearls.  


A variety of fixation methods are used in fusion of the subtalar joint (STJ) including 1 screw and 2 screw constructs. The rate of union is generally high for STJ fusion, regardless of the fixation method, provided the joint surfaces have been properly prepared and compressed and the patient avoids premature stress on the fusion site. Certain populations are known to have an increased risk of nonunion or delayed union including diabetics, smokers, and those undergoing revision of failed fusion. In this high-risk patient population, we propose that our novel 2-screw construct might have advantages over traditional fixation constructs without identified disadvantages. The technique is simple enough to be used in all primary and revision STJ fusion procedures, and this has become our practice. In the present study, 15 feet in 15 consecutive patients who underwent STJ fusion using a novel 2-screw fixation construct were retrospectively reviewed to assess the fusion outcome and complications. Specifically, we offer a novel 2-screw construct that offers the stability of the traditional parallel 2-screw construct while maintaining a maximum raw bone surface area at the posterior facet achieved by single-screw fixation. A retrospective review of radiographs taken 10 weeks postoperatively indentified a 100% fusion rate (15 of 15). All patients in our series achieved fusion, including several high-risk cases, and no significant complications were identified. PMID:22831782

Boffeli, Troy J; Reinking, Ryan R



Arthrodesis of the toe joints with an intramedullary cannulated screw for correction of hammertoe deformity.  


Twenty-four patients (37 feet, 51 toes) affected by hammertoe deformity of the lesser toes and treated surgically by arthrodesis of the proximal interphalangeal joint, stabilized with an intramedullary titanium cannulated screw, were reviewed 1-4 years after the operation. At follow-up, the arthrodesis was fused in 48 toes; three toes showed an asymptomatic radiographic nonunion, and in one of them the screw was broken. In seven toes, the cannulated screw was removed because of persistent pain at the tip of the toe where the head of the screw was located. In one case only, there was a late infection, with toe malalignment. All the patients were able to use street shoes 2 weeks after surgery. The average AOFAS score at follow-up was 86.54 points. Compared to the conventional temporary stabilization with an intramedullary Kirschner wire, the stabilization with a cannulated screw decreases the risk of infection, of radiographic nonunion, and of mallet toe deformity. PMID:15132935

Caterini, R; Farsetti, P; Tarantino, U; Potenza, V; Ippolito, E



Transiliac-transsacral screws for posterior pelvic stabilization.  


Typical posterior pelvic fixation constructs use one or more large screws inserted from the lateral iliac cortex into the safe upper sacral ala or body. As a result of the deforming forces acting perpendicular to the implant axis, routine iliosacral screw fixation may not provide adequate stabilization, especially in certain unstable injuries. Longer iliosacral screws that traverse the entire upper sacrum and exit the contralateral iliac cortex may improve holding power and also stabilize concomitant contralateral posterior pelvic injuries. These transiliac-transsacral screws are reliably safe to insert using routine intraoperative fluoroscopy, and they provide durable fixation. These screws require careful preoperative planning and more precise technical attention during insertion because they pass through both sacral alar zones. Transiliac-transsacral screws may be particularly useful in the presence of osteoporosis, significant posterior pelvic instability including spinopelvic dissociation, patient obesity, anticipated noncompliant behavior, bilateral posterior pelvic injuries, and nonunion procedures. PMID:21577075

Gardner, Michael J; Routt, M L Chip



Torque stability of different abutment screws submitted to mechanical cycling.  


Purpose: To evaluate the torque stability of different UCLA retention screws of single implant-supported crowns submitted to mechanical cycling. Materials and Methods: Crowns fabricated from nickel-chromium-molybdenum alloy were attached to external-hexagon implants and grouped by the different retention screws used (n = 10): Ti, titanium screws (BRUNIHT, Biomet 3i); Au, gold-palladium screws with 24-carat gold coating (Gold-Tite, Biomet 3i); TiC, titanium alloy (Ti-6Al-4V) screw with diamondlike carbon coating (Neotorque, Neodent); and TiN, Ti-6Al-4V screw with aluminum-titanium-nitride coating (Ti-Tite, Conexão). Three initial removal torque (RT) values were obtained for each screw after torque insertion using an analog torque gauge. The final RT was measured after mechanical cycling (1 × 106 cycles at 2 Hz under 130 N). Data were submitted to analysis of variance and the Fischer test. Results: Statistically significant differences were observed between the initial RT in groups Ti and TiN, and between TiC and TiN. No statistically significant difference was seen between mean RT obtained before and after mechanical cycling, except for the Ti screws. All groups exhibited similar torque maintenance after mechanical cycling. Conclusion: Although no significant difference was observed among groups for the final percentage of torque maintenance, the final RT values of the coated screws were higher than those of the noncoated screws. PMID:24066337

Vianna, Camila de Assis; Delben, Juliana Aparecida; Barão, Valentim A R; Ferreira, Mayara Barbosa; Dos Santos, Paulo Henrique; Assunçao, Wirley Gonçalves


Dynamic glenohumeral joint stability.  


Stability of the glenohumeral joint with an anterior, posterior, and inferior displacement force of 50 N was measured in a dynamic shoulder model. Controlled hydrodynamic actuator forces were applied to the deltoid muscle and to the rotator cuff in seven anatomic specimens. During elevation of the arm the position of the humerus was measured with a six-degree-of-freedom ultrasonic sensor device. The rotational center of the humeral head was used as a reference point for translation. A displacement force of 50 N led to significant humeral head displacement anteriorly and posteriorly but not inferiorly. A 50% reduction of rotator cuff forces increased anterior displacement by 46% and posterior displacement by 31%. Venting of the glenohumeral joint space and of the subacromial bursa resulted in a 50% increase of anterior displacement, a 19% increase of posterior displacement, and significant inferior displacement. This study demonstrates that in addition to passive stabilizers and negative intraarticular pressure, rotator cuff force significantly contributes to stabilization of the glenohumeral joint during arm motion. Muscle strength and coordination should gain more emphasis in the diagnosis and treatment of shoulder instability. PMID:9524340

Wuelker, N; Korell, M; Thren, K


Distal interphalangeal joint arthrodesis of the lesser toes using the Barouk screw  

Microsoft Academic Search

A new method of fixation for distal interphalangeal (DIP) joint arthrodesis of the lesser toes using the Barouk screw has been used in five toes in five patients. The techniques as well as the advantages are discussed in this article. Deep infection, loss of fixation and failure of fusion were not evident in any of the cases.The Barouk screw fixation

S Jones; F Ali; A Genever; M. J Flowers; S. H Bostock



Interphalangeal joint arthrodesis with oblique placement of an AO lag screw.  


A damaged interphalangeal (IP) joint may be treated by fusion. Arthrodesis should leave the joint at the most functional angle and give sound bony union in the shortest possible time, maintaining maximum proximal and distal joint motion. The lateral oblique placement of a single AO lag screw, proximal to distal, achieves these aims. This method gives sufficient proximal bone for screw purchase and better control of the desired angle of fusion. This technique has led to fusion in 22 of 23 joints (96%), taking an average of 8.2 weeks. PMID:8014552

Teoh, L C; Yeo, S J; Singh, I



Pedicle Screw-Based Posterior Dynamic Stabilization: Literature Review  

PubMed Central

Posterior dynamic stabilization (PDS) indicates motion preservation devices that are aimed for surgical treatment of activity related mechanical low back pain. A large number of such devices have been introduced during the last 2 decades, without biomechanical design rationale, or clinical evidence of efficacy to address back pain. Implant failure is the commonest complication, which has resulted in withdrawal of some of the PDS devices from the market. In this paper the authors presented the current understanding of clinical instability of lumbar motions segment, proposed a classification, and described the clinical experience of the pedicle screw-based posterior dynamic stabilization devices.

Sengupta, Dilip K.; Herkowitz, Harry N.



Cranial facet joint violations by percutaneously placed pedicle screws adjacent to a minimally invasive lumbar spinal fusion  

Microsoft Academic Search

Background contextProtecting cranial facet joint is a modifiable risk factor that may decrease the incidence of adjacent segment disease after lumbar spinal fusion. Percutaneously instrumented screws may more frequently violate cranial facet joints because of the potential limitation of screw entry site selection. To our knowledge, however, there is no study that has evaluated the cranial facet joint violations adjacent

Yung Park; Joong Won Ha; Yun Tae Lee; Na Young Sung



Screw Placement and Osteoplasty Under Computed Tomographic-Fluoroscopic Guidance in a Case of Advanced Metastatic Destruction of the Iliosacral Joint  

SciTech Connect

We present a case of combined surgical screw placement and osteoplasty guided by computed tomography-fluoroscopy (CTF) in a 68-year-old man with unilateral osteolytic destruction and a pathological fracture of the iliosacral joint due to a metastasis from renal cell carcinoma. The patient experienced intractable lower back pain that was refractory to analgesia. After transarterial particle and coil embolization of the tumor-feeding vessels in the angiography unit, the procedure was performed under general anesthesia by an interdisciplinary team of interventional radiologists and trauma surgeons. Under intermittent single-shot CTF, two K wires were inserted into the left iliosacral joint from a lateral transiliac approach at the S1 level followed by two self-tapping surgical screws. Continuous CTF was used for monitoring of the subsequent polymethylmethacrylate injection through two vertebroplasty cannulas for further stabilization of the screw threads within the osteolytic sacral ala. Both the screw placement and cement injection were successful, with no complications occurring during or after the procedure. With additional nonsteroidal anti-inflammatory and opioid medication, the patient reported a marked decrease in his lower back pain and was able to move independently again at the 3-month follow-up assessment. In our patient with intolerable back pain due to tumor destruction and consequent pathological fracture of the iliosacral joint, CTF-guided iliosacral screw placement combined with osteoplasty was successful with respect to joint stabilization and a reduction in the need for analgesic therapy.

Trumm, Christoph Gregor, E-mail: [University of Munich, Department of Clinical Radiology (Germany); Rubenbauer, Bianca; Piltz, Stefan [University of Munich, Department of Surgery (Germany); Reiser, Maximilian F.; Hoffmann, Ralf-Thorsten [University of Munich, Department of Clinical Radiology (Germany)



Facet joint violation during pedicle screw insertion: a cadaveric study of the adult lumbosacral spine comparing the two pedicle screw insertion techniques  

Microsoft Academic Search

This article analyses the incidence of facet joint violation by pedicle screws inserted via the two most commonly used techniques,\\u000a intersection and mammillary. Pedicle screws were inserted on each side of fresh-frozen human cadevaric specimen lumbosacral\\u000a spines using the two techniques. All facet joints which were violated were found to be on the right side, where the mamillary\\u000a process technique

Kook Jin Chung; Seung Woo Suh; Keny Swapnil; Jae Hyuk Yang; Hae Ryong Song



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



Joint stabilizing projects in defense  

SciTech Connect

Joint defensive projects could increase stability and decrease the alert rates of strategic forces. Areas include the defense of the US, Commonwealth of Independent States (CIS), and their allies against third world threats; protection against each other`s accidental or unauthorized launches; and defense against intentional attacks. The most promising area appears to be defining interfaces for the handover of satellite warning and trajectory information, which applies to most phases of theater defense and mutual protection. 19 refs.

Canavan, G.H.; Browne, J.C.; Joseph, R.J.



Joint stabilizing projects in defense  

SciTech Connect

Joint defensive projects could increase stability and decrease the alert rates of strategic forces. Areas include the defense of the US, Commonwealth of Independent States (CIS), and their allies against third world threats; protection against each other's accidental or unauthorized launches; and defense against intentional attacks. The most promising area appears to be defining interfaces for the handover of satellite warning and trajectory information, which applies to most phases of theater defense and mutual protection. 19 refs.

Canavan, G.H.; Browne, J.C.; Joseph, R.J.



Distal interphalangeal joint arthrodesis in extension using a headless compressive screw.  


The aim of this study was to review the clinical outcome and complications in patients who underwent distal interphalangeal joint (DIPJ) fusion in extension using an axial screw with variable thread pitch (Mini Acutrak screw Acumed, LLC, Hillsboro, OR, USA). Thirty-eight cases of DIPJ or thumb IPJ were performed and assessed through patient satisfaction (hand function and pain) and radiographs. The quickDASH scores were assessed at a mean follow up of 8 months (range : 6 to 12 months). Ninety-three per cent of participants reported good or excellent functional outcome, with Quick DASH scores of less than 30. There were five complications noted (one superficial wound infection; two fractures; two screw cut-outs). All cases progressed to radiographic bony union at six months. PMID:23821966

Konan, Sujith; Das, Aditi; Taylor, Emma; Sorene, Elliot



Early failure of the Moje screw-fit ceramic metatarsophalangeal joint replacement  

Microsoft Academic Search

Introduction: This implant seemed to overcome the failings of previous designs having a ceramic bearing attached to a titanium positional screw in the metaphyseal bone and an apatite-coated ceramic–bone interface to enhance secondary stability. On the basis of encouraging early results reported from Germany, Orthosonics Ltd. marketed the implant in the UK from June 1999. Following problems with the device

D. J. Redfern; S. D. Coleridge; S. P. Bendall



Comparison of stability of mandibular segments following the sagittal split ramus osteotomy with poly- l-lactic acid (PLLA) screws and titanium screws fixation  

Microsoft Academic Search

The purpose of this study was to retrospectively compare the stability of the mandible following the surgical orthodontic treatment by sagittal split ramus osteotomy (SSRO) and orthodontic multi-bracket treatment using fixation methods with poly-l-lactic acid (PLLA) or titanium screws. The sample examined was 23 subjects with PLLA screws (PLLA group) and 22 subjects with titanium screws (Titan group). Lateral cephalometric

Yasuo Oba; Akihiro Yasue; Kazuyuki Kaneko; Ryoko Uchida; Atsushi Shioyasono; Keiji Moriyama



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....


Radiographic criteria for placement of translaminar facet screws  

Microsoft Academic Search

Background contextScrew fixation of the facet joint has been reported to stabilize the lumbar spine and facilitate spinal fusion. Accurate placement of translaminar facet screws (TLFSs) requires identification of the posterior spinal elements, and the facet joints in particular, which may be facilitated by intra-operative fluoroscopy.

Frank M Phillips; Erling Ho; Benjamin W Cunningham



The percutaneous stabilisation of the sacroiliac joint with hollow modular anchorage screws: a prospective outcome study.  


PURPOSE: The use of percutaneous iliosacral screw fixation as a treatment of sacroiliac joint pain has been reported to be successful. This study was a prospective single surgeon series to evaluate the short-term outcomes of patients who underwent percutaneous sacroiliac joint stabilisation. METHODS: Between July 2004 and February 2011, 73 patients underwent percutaneous sacroiliac joint fusion in our unit. All patients completed a short form (SF)-36 questionnaire, visual analogue pain score and Majeed scoring questionnaire prior to treatment and at last follow-up. RESULTS: 55 patients (9 male and 46 female) completed follow-up. The average follow-up period was for 36.18 months (range 12-84). The mean preoperative SF-36 scores were 26.59 for physical health and 40.38 for mental health. The mean postoperative SF-36 scores were 42.93 for physical health and 52.77 for mental health. The mean visual analogue pain scores were 8.1 preoperative and 4.5 postoperative. The mean pelvic specific scoring were 36.9 preoperative and 64.78 postoperative. We noted that patients who had previous instrumented spinal surgery did significantly worse than those who had not. We had two nerve root-related complications. CONCLUSION: We conclude that in selected patient group who respond positively to CT-guided injection, a percutaneous SI joint stabilisation is beneficial in effecting pain relief and functional improvement. PMID:23686478

Mason, Lyndon W; Chopra, Iqroop; Mohanty, Khitish



Cervical spine injuries associated with lateral mass and facet joint fractures: New classification and surgical treatment with pedicle screw fixation  

Microsoft Academic Search

To clarify the injury pattern, initial spinal instability, degree of discoligamentous injuries in cervical lateral mass and facet joint fractures, we retrospectively analyzed radiological parameters and introduced a new classification for these injuries. Surgical treatment was performed with cervical pedicle screw fixation (CPS), and overall neurological and radiological outcome was evaluated with a minimum follow-up period of 2 years. Lateral mass

Yoshihisa Kotani; Kuniyoshi Abumi; Manabu Ito; Akio Minami



[Fixation of periprosthetic femur fractures with the less invasive stabilization system (LISS)--a new minimally invasive treatment with locked fixed-angle screws].  


The Less Invasive Stabilization System (LISS) is a minimally invasive technique indicated for fixation of periprosthetic fractures. This new system allows percutaneous placement of cortical-shaft screws and fixation of the fracture with fixed-angle locked screws with minimal surgical exposure of the mostly osteoporotic bone and without disturbance of the existing total joint replacement. Immediate range-of-motion exercises are begun postoperatively. A retrospective clinical review of 5 patients (2 total hip arthroplasties, 3 total knee arthroplasties) was performed to describe indications, surgical technique, intra- and postoperative complications and patient follow-up. Indications are periprosthetic distal femur fractures, per- and supracondylar fractures. Contraindications are none, except existing medical comorbidities. Extraarticular fractures were treated via stab incisions over the lateral femoral condyle. Fractures with intraarticular displacement were fixed via an anterolateral parapatellar approach to the knee joint. After anatomic reduction of femoral condyles, articular fragments are fixed with Kirschner wires, followed by closed reduction aligning the articular fragments controlling length, axis and rotation. The LISS is introduced proximally under the M. vastus lateralis along the femur. It is fixed with self-drilling cortical shaft screws, locked fixed-angle screws both proximally and distally. Range-of-motion exercises are begun on the second day postoperatively. Time to full weight bearing averaged 6-8 weeks depending on clinical and radiological findings. Benefits of the LISS technique include the minimally invasive approach with increased primary stability using monocortical fixings thus eliminating the need for spongiosaplasty and blood transfusion. Disadvantages of the percutaneous placement of the LISS include malplacement on the femur, proximal screw pull-out and postoperative rotational and axial malalignment. PMID:12594614

Kolb, W; Guhlmann, H; Friedel, R; Nestmann, H



Joint stability after total shoulder arthroplasty in a cadaver model  

Microsoft Academic Search

A cadaver model was used to test the hypothesis that glenohumeral joint stability is independent of articular surface conformity after total shoulder arthroplasty. For the purposes of this study joint stability was defined as the minimum force required for joint dislocation. After arthroplasty components were implanted into fresh-frozen glenohumeral joints, specimens were mounted on a load frame and tested for

Andrew R Karduna; Gerald R Williams; John L Williams; Joseph P Iannotti



Superior segment facet joint violation and cortical violation after minimally invasive pedicle screw placement  

Microsoft Academic Search

Background contextMinimally invasive approaches to the lumbar spine allow for pedicle screw placement through a muscle-splitting paraspinal approach. These techniques are highly dependent on fluoroscopy and do not allow for direct visualization of anatomic landmarks. The effect of this on the accuracy of pedicle screw placement is not well described. The purpose of this study was to evaluate the rate

Jeffrey B. Knox; Joseph M. Dai; Joseph R. Orchowski



Arthrodesis of the first metatarsophalangeal joint: a biomechanical study comparing memory compression staples, cannulated screws, and a dorsal plate.  


Arthrodesis of the first metatarsophalangeal joint of 21 matched pairs of cadaver toes was performed in order to compare the strength of three methods of internal fixation: 1. two crossed cannulated screws, 2. a dorsal plate with an oblique 0.062 K-wire, and 3. two compression staples with an oblique 0.062 K-wire. Biomechanical testing with plantar force was carried out, and gapping across the fusion site was measured. Stiffness, load to 1-mm displacement, and force to failure was determined for each specimen. Both the plate and screw constructs were statistically stronger in force to failure and initial stiffness than the compression construct. Compression staples have an advantage in their ease of insertion and theoretical continuous compressive force across an arthrodesis site, but should be supplemented with a cast or other external immobilization until union is achieved. PMID:11858342

Neufeld, Steven K; Parks, Brent G; Naseef, George S; Melamed, Eyal A; Schon, Lew C



Arthroscopic treatment of acute acromioclavicular joint dislocation  

Microsoft Academic Search

An original technique for the treatment of acute acromioclavicular (AC) joint dislocations is proposed. It consists of a closed reduction and stabilization of the AC joint, positioning a cannulated screw between the clavicle and the coracoid under arthroscopic control, without any exposure to x-rays. The conoid and trapezoid ligaments are not sutured or reconstructed. The screw is finally removed under

Paolo R Rolla; Michele F Surace; Luigi Murena



Transcortical Screw Fixation of the Olecranon Shows Equivalent Strength and Improved Stability Compared to Tension Band Fixation.  


OBJECTIVES:: Currently, the standard for 21-B3.1 olecranon fracture fixation is the tension band wire construct described by the AO foundation. While this technique effectively repairs displaced olecranon fractures and osteotomies, it is associated with a high rate of secondary surgery for implant removal due to hardware "back out," prominence and discomfort. The senior author of this study has used transcortical screw fixation for olecranon fractures and osteotomies to avoid hardware discomfort, but has been unable to find literature documenting the strength of this method. Accordingly, we compared the strength and stability of transcortical screw fixation to tension band fixation of simple transverse olecranon fractures under cyclical loading. METHODS:: Eighteen 4 generation synthetic biomechanical testing ulnas underwent a transverse olecranon osteotomy, and were repaired by tension banding or screw fixation. Two 4.0 mm partially threaded screws inserted across the fracture gap into the anterior cortex of the ulna achieved screw fixation. Ulnas were tested in two ways: (1) cyclic loading that simulated pushing up from a chair and (2) single cycle loading to failure. Fracture displacement was recorded using a transducer that was placed on the posterior surface of the ulna. RESULTS:: Differences between screw fixation and tension banding in the peak displacement during cyclic loading and single cycle load to failure were not significant. Screw fixation did show significantly less "trough" displacement (resting position between cycles) during cyclic loading indicating less plastic deformation. CONCLUSION:: In a synthetic bone model of simple transverse olecranon fractures, screw fixation provided equivalent strength and less plastic deformation as compared to tension banding. PMID:23681413

Jones, Tyler B; Karenz, Andrew; Weinhold, Paul S; Dahners, Laurence E



Editorial: Stabilization of the sacroiliac joint.  


Lower back pain and pain involving the area of the posterior iliac spine are extremely common. Degeneration of the sacroiliac joint (SIJ) is one potential cause for lower back pain and pain radiating into the groin or buttocks. Degenerative changes to the lumbar spine and sacroiliac joints are common. A recent study evaluating SIJ abnormalities in a primary low back pain population demonstrated 31.7% of patients demonstrated SI joint abnormalities. (4) As is the case for the evaluation and management of isolated lower back pain, the evaluation, management, and role for surgical intervention in SIJ pain is very controversial. Many patients have degenerative changes of the disc, facet joints, and SIJs. A recent systematic review performed to determine the diagnostic accuracy of tests available to clinicians to identify the disc, facet joint, or SIJ as the source of low back pain concluded that tests do exist that change the probability of the disc or SIJ (but not the facet joint) as the source of low back pain. (3) It was also concluded that the usefulness of these tests in clinical practice, particularly for guiding treatment selection, remains unclear. (3) Although there is general agreement that SIJ pathological changes are a potential cause of pain, there is far less agreement about the optimal management of these conditions. A variety of conditions can cause SIJ dysfunction including degenerative and inflammatory arthritis, trauma, prior lumbosacral fusion, hip arthritis, limb length inequality, infections, and neoplasia. (8) There is increasing evidence that image intensifier-guided single periarticular injection can correctly localize pain to the SIJ but the optimal management strategy remains controversial. Recent publications have compared surgical versus injection treatments and fusion versus denervation procedures. (1 , 8) A systematic review found improvement regardless of the treatment, with most studies reporting over 40% improvement in pain as measured by VAS or NRS scores. (8) It cautioned that one of the studies reported 17.6% of patients experiencing mild/no pain compared with 82.4% experiencing marked/severe pain at 39 months after SIJ fusion procedures. (6 , 8) This systematic review also noted that despite improvements in reported pain, less than half of patients who had work status reported as returning to work. (8) Because of the functional and socioeconomic consequences of chronic lower back pain, numerous surgical treatments to improve this condition have been attempted by spinal surgeons through the years. Arthrodesis of the SIJ is a surgical procedure with a long history dating to the beginnings of spinal surgery. (7) Poor results, high complication rates and the need for additional surgical procedures have generally diminished the enthusiasm for this procedure until recently. (6) A variety of "minimally invasive" procedures have been recently introduced that have rekindled enthusiasm for the surgical management of SIJ pathology. The technique demonstrated in the "Stabilization of the SIJ with SI-Bone" is one of these new techniques. There has been a recent publication detailing the very short term clinical outcomes with this technique that reported encouraging results. (5) In this series of 50 patients, quality of life questionnaires were available for 49 patients preoperatively, 41 patients at 3 months, 40 at 6 months and only 27 at 12 months, complicating the ability to accurately assess true outcomes. Although the focus of this video by Geisler is on the surgical technique, there should have been more information provided on the expected surgical outcomes and potential complications of SIJ fusion. (2) The video only gives minimal information on how to appropriately select patients with potential SIJ pathology for surgical intervention. There are insufficient recommendations on the clinical and radiographic follow-up needed for this procedure. A concern with this implant is whether the porous plasma spray coating on the implant actually results in bone growth across the SIJ

Shaffrey, Christopher I; Smith, Justin S



Muscle contribution to elbow joint valgus stability.  


Repetitive valgus stress of the elbow can result in excessive strain or rupture of the native medial ulnar collateral ligament (MUCL). The flexor-pronator mass (FPM) may be particularly important for elbow valgus stability in overhead-throwing athletes. The aim of this study was to identify the relative contribution of each muscle of the FPM--that is, the flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), flexor carpi radialis (FCR), and pronator teres (PT)--and of the extensor-supinator mass, including the extensor carpi ulnaris (ECU), extensor digitorum communis (EDC), extensor carpi radialis longus and brevus, and brachioradialis, to elbow valgus stability at 45 degrees and 90 degrees of elbow flexion angles. Eight fresh-frozen elbow specimens (mean age at death, 73.75 +/- 14.07 years) were tested. With the skin and subcutaneous tissue removed but all muscles left intact, each individual muscle of the FPM and extensor-supinator mass was loaded at 3 levels of force. During loading, strain on the MUCL and the kinematics of the elbow were measured simultaneously. Kinematic measurements were later repeated when the MUCL was fully cut. At 45 degrees and 90 degrees of elbow flexion, individual loading of the FCU, FDS, and FCR caused significant relief to the MUCL whereas the PT produced no significant change. Furthermore, of these flexor muscles, the FCU provided the greatest MUCL relief at both 45 degrees and 90 degrees . In contrast, loading of the ECU at 45 degrees of elbow flexion produced a significant increase in MUCL strain. All FPM muscles caused significant elbow varus movement at both 45 degrees and 90 degrees when loaded individually. At 90 degrees , the FCU created more motion than both the FCR and PT but not the FDS, and the FDS created more motion than the PT. The EDC and ECU created significant valgus movement at 45 degrees and 90 degrees , which became insignificant when the MUCL was transected. Our study suggested that the FCU, FDS, and FCR may function as dynamic stabilizers, with the FCU being the primary stabilizer for elbow valgus stability, incorporating with the MUCL for all tested joint configurations. Our findings also suggest that the ECU and EDC increased MUCL strain and elbow valgus movement at both 45 degrees and 90 degrees . PMID:17936028

Lin, Fang; Kohli, Navjot; Perlmutter, Sam; Lim, Dohyung; Nuber, Gordon W; Makhsous, Mohsen



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


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



Percutaneous fusion of the sacroiliac joint with hollow modular anchorage screws: clinical and radiological outcome.  


We reviewed 15 consecutive patients, 11 women and four men, with a mean age of 48.7 years (37.3 to 62.6), who between July 2004 and August 2007 had undergone percutaneous sacroiliac fusion using hollow modular anchorage screws filled with demineralised bone matrix. Each patient was carefully assessed to exclude other conditions and underwent pre-operative CT and MR scans. The diagnosis of symptomatic sacroiliac disease was confirmed by an injection of local anaesthetic and steroid under image intensifier control. The short form-36 questionnaire and Majeed's scoring system were used for pre- and post-operative functional evaluation. Post-operative radiological evaluation was performed using plain radiographs. Intra-operative blood loss was minimal and there were no post-operative clinical or radiological complications. The mean follow-up was for 17 months (9 to 39). The mean short form-36 scores improved from 37 (23 to 51) to 80 (67 to 92) for physical function and from 53 (34 to 73) to 86 (70 to 98) for general health (p = 0.037). The mean Majeed's score improved from 37 (18 to 54) pre-operatively to 79 (63 to 96) post-operatively (p = 0.014). There were 13 good to excellent results. The remaining two patients improved in short form-36 from a mean of 29 (26 to 35) to 48 (44 to 52). Their persistent pain was probably due to concurrent lumbar pathology. We conclude that percutaneous hollow modular anchorage screws are a satisfactory method of achieving sacroiliac fusion. PMID:19407297

Khurana, A; Guha, A R; Mohanty, K; Ahuja, S



One-stage revision surgery to treat hip infected nonunion after stabilization with a sliding compression screw  

Microsoft Academic Search

IntroductionExtracapsular hip infected nonunion after stabilization with a sliding hip screw (SCS) is uncommon and a convincing treatment method has not yet been reported in the literature.Patients and methodsThirteen consecutive patients who sustained such a disability were treated with removal of SCS, local radical debridement, vancomycin powder with or without gentamicin solution application, re-insertion of a new SCS, and autogenous

C. C. Wu; W. J. Chen



Effect of constrained posterior screw and rod systems for primary stability: biomechanical in vitro comparison of various instrumentations in a single-level corpectomy model.  


Cervical corpectomy is a frequently used technique for a wide variety of spinal disorders. The most commonly used approach is anterior, either with or without plating. The results for single-level corpectomy are better than in multilevel procedures. Nevertheless, hardware- or graft-related complications are observed. In the past, constrained implant systems were developed and showed encouraging stability, especially for posterior screw and rod systems in the lumbar spine. In the cervical spine, few reports about the primary stability of constrained systems exist. Therefore, in the present study we evaluated the primary stability of posterior screw and rod systems, constrained and non-constrained, in comparison with anterior plating and circumferential instrumentations in a non-destructive set-up, by loading six human cadaver cervical spines with pure moments in a spine tester. Range of motion and neutral zone were measured for lateral bending, flexion/extension and axial rotation. The testing sequence consisted of: (1) stable testing; (2) testing after destabilization and cage insertion; (3a) additional non-constrained screw and rod system with lateral mass screws, (3b) with pedicle screws instead of lateral mass screws; (4a) constrained screw and rod system with lateral mass screws, (4b) with pedicle screws instead of lateral mass screws; (5) 360 degrees set-up; (6) anterior plate. The stability of the anterior plate was comparable to that of the non-constrained system, except for lateral bending. The primary stability of the non-constrained system could be enhanced by the use of pedicle screws, in contrast to the constrained system, for which a higher primary stability was still found in axial rotation and flexion/extension. For the constrained system, the achievable higher stability could obviate the need to use pedicle screws in low instabilities. Another benefit could be fewer hardware-related complications, higher fusion rate, larger range of instabilities to be treated by one implant system, less restrictive postoperative treatment and possibly better clinical outcome. From a biomechanical standpoint, in regard to primary stability the constrained systems, therefore, seem to be beneficial. Whether this leads to differences in clinical outcome has to be evaluated in clinical trials. PMID:15248055

Schmidt, René; Wilke, Hans-Joachim; Claes, Lutz; Puhl, Wolfhart; Richter, Marcus



Rate of nonunion after first metatarsal-cuneiform arthrodesis using joint curettage and two crossed compression screw fixation: a systematic review.  


First metatarsal-cuneiform joint arthrodesis is a commonly performed procedure to correct first ray pathology. The most widely accepted approach is curettage and 2 crossed compression screw fixation followed by a period of non-weight-bearing. Despite adequate joint preparation and stable internal fixation, nonunion has been cited as a known complication. This can lead to the need for revision surgery, which is undesirable and drives healthcare costs. To further investigate this topic, we conducted a systematic review to determine the rate of nonunion after the first metatarsal-cuneiform joint arthrodesis using curettage and 2 crossed compression screw fixation. Studies were eligible for inclusion only if they involved the following: arthrodesis of the first metatarsal-cuneiform joint with curettage and 2 crossed compression screw fixation, a minimum of 25 feet, with a mean follow-up of at least 6 months, and a period of postoperative non-weight-bearing. After considering all the potentially eligible references, 1 (1.8%) evidence-based medicine level I and 4 (7.3%) evidence-based medicine level IV studies met our inclusion criteria. A total of 537 patients (599 feet), 54 (10%) males and 483 (90%) females, with a weighted mean age of 49.4 years, were included. For those studies that specified the exact follow-up, the weighted mean was 30.9 months. A total of 30 nonunions (5%) were reported, with 17 (56.7%) symptomatic. The results of our systematic review revealed a relatively high rate of nonunion for first metatarsal-cuneiform joint arthrodesis with curettage and 2 crossed compression screw fixation, even when performed by experienced surgeons. Therefore, given the available data, additional prospective investigations are warranted, especially in the evaluation and comparison of fixation constructs and postoperative management. PMID:21908206

Donnenwerth, Michael P; Borkosky, Sara L; Abicht, Bradley P; Plovanich, Elizabeth J; Roukis, Thomas S



Biomechanical Differences of Coflex-F and Pedicle Screw Fixation in Stabilization of TLIF or ALIF Condition - A Finite Element Study  

Microsoft Academic Search

\\u000a Lumbar interbody fusion is a common procedure for treating lower back pain related to degenerative disc diseases. The Coflex-F\\u000a is a recently developed interspinous spacer, the makers of which claim that it can provide stabilization similar to pedicle\\u000a screw fixation. Therefore, this study compares the biomechanical behavior of the Coflex-F device and pedicle screw fixation\\u000a with transforaminal lumbar interbody fusion

C. C. Lo; K. J. Tsai; Z. C. Zhong; C. Hung


A comparison of parallel and diverging screw angles in the stability of locked plate constructs.  


We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20° configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20° divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10° and 20° divergent configurations. In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading. PMID:21911539

Wähnert, D; Windolf, M; Brianza, S; Rothstock, S; Radtke, R; Brighenti, V; Schwieger, K



Anterior stability of the glenohumeral jointA dynamic model  

Microsoft Academic Search

This study defines the interaction of the rotator cuff musculature and the glenohumeral ligaments in provid ing anterior stability to the glenohumeral joint. Eight cadaveric shoulders were studied using a testing frame that individually simulated the forces of the subscapu laris, the supraspinatus, and the infraspinatus\\/teres minor musculature. The application of these forces abducted the humerus to approximately 90°. The

Paul R. Cain; Thomas A. Mutschler; Freddie H. Fu; S. Kwon Lee



Biomechanical evaluation of subtalar fusion: the influence of screw configuration and placement.  


Common surgical procedures for subtalar fusion include joint resection, autologous bone grafting, and osteosynthesis with screws in a parallel screw configuration. Although fusion is a routine procedure, the reported rates of nonunion have been high. The present study assessed different screw configurations in terms of their rotational and bending stability in an artificial bone model and cadaver bone. Arthrodesis was always performed with 2 screws. Three different screw configurations were tested: parallel, counter-parallel, and a delta configuration. Two different screw designs were used: a cannulated, partially threaded screw (6.5-mm and 8.0-mm diameter) and a solid screw with a different thread design. Eight experimental groups were investigated as pilot studies in artificial bones and then 3 groups in cadaver bones. The parameters were the primary stiffness and deflection of the construct for loads simulating the internal-external rotation and supination-pronation. Delta positioning of the screws resulted in the greatest biomechanical stiffness and the lowest degrees of deflection of the arthrodesis in the artificial bones and cadaver bones. Increasing the screw diameter from 6.5 to 8.0 mm resulted in no additional stability of the arthrodesis in the artificial bones. The results of the present study have indicated that the delta configuration for arthrodesis results in the greatest construct stiffness and lower relative deflection between the talus and calcaneus in the positions tested. PMID:23333056

Hungerer, Sven; Eberle, Sebastian; Lochner, Susanne; Maier, Michael; Högel, Florian; Penzkofer, Rainer; Augat, Peter



Stabilization of the interphalangeal joint of the big toe: comparison of three methods.  


Three methods of stabilizing the IP of the big toe were compared. In group A, 10 patients underwent tenodesis of the extensor hallucis longus to the extensor digitorum brevis tendon. All of them developed a toe-drop; two patients had significant symptoms that required IP fusion. In group B, 19 patients underwent IP fusion using smooth or threaded intramedullary Kirschner wire fixation. There were nine nonunions, three requiring refusion. In group C, 32 patients underwent IP fusion using intramedullary screw fixation. There was one nonunion with screw failure that required revision. Although none of our patients considered the toe-drop after extensor hallucis longus tenodesis cosmetically unacceptable, this may not be so in other cultures. All complications following IP fusion with screw fixation were technical and are avoidable. When stabilization of IP is required, we recommend fusion of IP with screw fixation. PMID:1634149

Asirvatham, R; Rooney, R J; Watts, H G



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


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.



Decompressive cervical laminectomy and lateral mass screw-rod arthrodesis. Surgical analysis and outcome  

PubMed Central

Background This study evaluates the outcome and complications of decompressive cervical Laminectomy and lateral mass screw fixation in 110 cases treated for variable cervical spine pathologies that included; degenerative disease, trauma, neoplasms, metabolic-inflammatory disorders and congenital anomalies. Methods A retrospective review of total 785 lateral mass screws were placed in patients ages 16-68 years (40 females and 70 males). All cases were performed with a polyaxial screw-rod construct and screws were placed by using Anderson-Sekhon trajectory. Most patients had 12-14-mm length and 3.5 mm diameter screws placed for subaxial and 28-30 for C1 lateral mass. Screw location was assessed by post operative plain x-ray and computed tomography can (CT), besides that; the facet joint, nerve root foramen and foramen transversarium violation were also appraised. Results No patients experienced neural or vascular injury as a result of screw position. Only one patient needed screw repositioning. Six patients experienced superficial wound infection. Fifteen patients had pain around the shoulder of C5 distribution that subsided over the time. No patients developed screw pullouts or symptomatic adjacent segment disease within the period of follow up. Conclusion decompressive cervical spine laminectomy and Lateral mass screw stabilization is a technique that can be used for a variety of cervical spine pathologies with safety and efficiency.



Posterior stabilization of the cervical spine with hooks and screws. A clinical evaluation of 26 patients with traumatic, degenerative or metastatic lesions, using a new implant system  

Microsoft Academic Search

We operated on 26 patients with cervical spine disorders (13 with traumatic lesions, 3 with spinal stenosis and myelopathy, 1 with osteomyelitis and 9 with metastasis) with posterior stabilization. A new implant system (Cervi-Fix) based on rods, enabling a choice of either screw or laminar hook fixation in a free combination, was used. The system was evaluated for ease of

Christer Hildingsson; Håkan Jonsson



Biomechanical function of surgical procedures for acromioclavicular joint dislocations  

Microsoft Academic Search

PurposeSurgical procedures for treatment of acromioclavicular (AC) joint dislocation replace the coracoclavicular (CC) ligaments to minimize motion, allow scarring, and increase the subsequent stability of the joint. The purpose of this study was to evaluate the biomechanical function of the surgically repaired or reconstructed (CC Sling, Rockwood Screw [DePuy Orthopaedics, Warsaw, IN], and Coracoacromial [CA] Ligament Transfer Construct) AC joint

Rajesh Jari; Ryan S. Costic; Mark W. Rodosky; Richard E. Debski



Translaminar Facet Screw Fixation  

Microsoft Academic Search

significantly longer than that used by both Boucher and King due to an entry point at the base of the contralateral spinous process. This improves the technique by increasing the ef- fective working length of the screw on both sides of the facet joint resulting in increased strength of the fixation. This review focuses on the advantages of translaminar facet

Rick C. Sasso; Natalie M. Best


Metacarpophalangeal joint extensor tendon subluxation: a reconstructive stabilization technique.  


Extensor tendon subluxation can result from a disruption to the extensor retinacular system and/or the sagittal band at the metacarpophalangeal joint. When conservative treatment is insufficient to correct the subluxation, surgical treatment is necessary and various surgical techniques exist. We present a novel stabilization technique to centralize the extensor tendon using a junctura tendinum to lengthen an extensor digitorum communis tendon graft. This technique is simple and effective, creating a strong repair without associated stiffness. To achieve a less morbid, stable repair, we mimicked normal anatomy with minimal disruption to local soft tissue structures. This technique seems to offer biomechanical advantages over previously described techniques and shows successful treatment in the illustrated patient. PMID:23391359

ElMaraghy, Amr W; Pennings, Amanda



Dynamic Lumbar Pedicle Screw-Rod Stabilization: Two-Year Follow-Up and Comparison with Fusion  

PubMed Central

Background: A lumbar pedicular dynamic stabilization system (LPDSS) is an alternative to fusion for treatment of degenerative disc disease (DDD). In this study, clinical and radiological results of one LPDSS (Saphinaz, Medikon AS, Turkey) were compared with results of rigid fixation after two-year follow-up. Methods: All patients had anteroposterior and lateral standing x-rays of the lumbar spine preoperatively and at 3 months, 12 months and 24 months after surgery. Lordosis of the lumbar spine, segmental lordosis and ratio of the height of the intervertebral disc spaces (IVS) measured preoperatively and at 3 months, 12 months and 24 months after surgery. All patients underwent MRI and/or CT preoperatively, 3months, 12 months and 24 months postoperatively. The ratio of intervertebral disc space to vertebral body height (IVS) and segmental and lumbar lordosis were evaluated preoperatively and postoperatively. Pain scores were evaluated via Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) preoperatively and postoperatively. Results: In both groups, the VAS and ODI scores decreased significantly from preoperatively to postoperatively. There was no difference in the scores between groups except that a lower VAS and ODI scores were observed after 3 months in the LPDSS group. In both groups, the IVS ratio remained unchanged between preoperative and postoperative conditions. The lumbar and segmental lordotic angles decreased insignificantly to preoperative levels in the months following surgery. Conclusions: Patients with LPDSS had equivalent relief of pain and maintenance of sagittal balance to patients with standard rigid screw-rod fixation. LPDSS appears to be a good alternative to rigid fixation.

Ozer, Ali Fahir; Crawford, Neil R; Sasani, Mehdi; Oktenoglu, Tunc; Bozkus, Hakan; Kaner, Tuncay; Aydin, Sabri



Inferolateral Entry Point for C2 Pedicle Screw Fixation in High Cervical Lesions  

PubMed Central

Objective The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. Methods Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle 30° to 45° toward the midline in the transverse plane and 40° to 50° cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. Results There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). Conclusion Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

Lee, Kwang Ho; Lee, Chul Hee; Hwang, Soo Hyun; Park, In Sung; Jung, Jin Myung



Stability of osteosynthesis with bicortical screws placed in a triangular shape in mandibular sagittal split 5 mm advancement osteotomy: biomechanical tests.  


Sagittal split ramus osteotomy (SSRO) is common in orthognathic surgery, and osteosynthesis with bicortical titanium screws placed in a triangular shape is used for stabilisation. We biomechanically tested the stability of this configuration in 5 mm advancement SSRO with condylar replacement in the initial position using six fresh frozen human mandibles raised subperiosteally for surgical simulation. Osteotomy was done after marking the initial positions of the condyles and the symphysis on graph paper. The condyle was set in its initial position and the symphysis advanced exactly 5mm; this position was maintained during osteosynthesis using 2.7 mm bicortical screws placed in a triangular shape. The mandible was then placed horizontally on the testing machine and a continuous static force was applied perpendicularly at a displacement speed of 5 mm/min. A stainless steel plate was used to transmit the forces independently of the teeth. A mean force of 129.6 Newtons (N) was applied at the elastic/plastic limit on an effort/displacement curve, which is well beyond the maximal mean (SD) chewing forces of 21 N (14) measured after bilateral sagittal split ramus osteotomy (BSSRO). A linear equation relating force to displacement was worked out from this experiment. Osteosynthesis using three bicortical screws mounted triangularly after advancement SSRO of 5 mm is experimentally stable, and our results could be used experimentally to compare two osteosyntheses using the equation. PMID:20007004

Hadi, Geha; Karine, Bruyere-Garnier; Yves, Caire; Pierre, Lapelerie



Biomechanical comparison of axial load between cannulated locking screws and noncannulated cortical locking screws.  


The goal of this study was to compare the biomechanical stability of cannulated locking screws and noncannulated cortical locking screws in a periarticular locking plate. Twelve fresh-frozen porcine tibias with a 1-cm gap created distal to the tibial plateau were used to simulate an unstable proximal tibial fracture. All specimens were fixed with a periarticular proximal lateral tibial locking plate and divided into 2 groups based on whether the proximal metaphyseal screw holes of the plate were inserted with either cannulated locking screws or noncannulated cortical locking screws. An axial compressive load was applied to cause failure in each specimen using a materials testing instrument. The axial stiffness and maximum failure strength in axial loading were recorded. Axial stiffness of the constructs using noncannulated cortical locking screw was significantly higher than that of the constructs using cannulated locking screws (P=.006). Axial failure strength of the constructs using noncannulated cortical locking screw was significantly higher than that of the constructs using cannulated locking screws (P=.002). The failure mode observed in all specimens was a permanent screw-bending deformity over the head-shaft junction of proximal metaphyseal screws, irrespective of whether they were cannulated or noncannulated cortical locking screws. Fixation with noncannulated cortical locking screws offered more stability than cannulated locking screws with regard to axial stiffness and failure strength in a porcine model with unstable proximal tibial fractures. PMID:24093710

Yang, Shan-Wei; Kuo, Shyh Ming; Chang, Shwu Jen; Su, Tian-Shiang; Chen, Hsiang-Ho; Renn, Jenn-Huei; Lin, Ting-Sheng



Four quadrant parallel peripheral screw fixation for displaced femoral neck fractures in elderly patients  

PubMed Central

Background: The treatment options for displaced femoral neck fracture in elderly are screw fixation, hemiarthroplasty and total hip arthroplasty based primarily on age of the patient. The issues in screw fixation are ideal patient selection, optimal number of screws, optimal screw configuration and positioning inside the head and neck of femur. The problems of screw fixation may be loss of fixation, joint penetration, avascular necrosis of femoral head, nonunion, prolonged rehabilitation period and the need for second surgery in failed cases. We hereby present results of a modified screw fixation technique in femoral neck fractures in patients ?50 years of age. Materials and Methods: Patients ?50 years of age (range 50-73 years) who sustained displaced femoral neck fracture and fulfilled the inclusion criteria were enrolled in this prospective study. They were treated with closed reduction under image intensifier control and cannulated cancellous screw fixation. Accurate anatomical reduction was not aimed and a cross sectional contact area of >75% without varus was accepted as good reduction. Four screws were positioned in four quadrants of femoral head and neck, as parallel and as peripheral as possible. Radiological and functional results were evaluated periodically. Sixty four patients who could complete a minimum followup of two years were analyzed. Results: Radiologically, all fractures healed after mean duration of 10 weeks (range 8-12 weeks). There was no avascular necrosis. Nonanatomical healing was observed in 45 cases (70%). All patients except one had excellent functional outcome and could do cross-legged sitting and squatting. Chondrolysis with progressive head resorption was seen in one case, which was converted to total hip arthroplasty. Conclusion: Closed reduction and cannulated cancellous screw fixation gives satisfactory functional results in large group of elderly patients. The four quadrant parallel peripheral (FQPP) screw fixation technique gives good stability, allows controlled collapse, avoids fixation failure and achieves predictable bone healing in displaced femoral neck fracture in patients ?50 years of age.

Satish, Bhava RJ; Ranganadham, Atmakuri V; Ramalingam, Karruppasamy; Tripathy, Sujit Kumar



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


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



Strategies used to stabilize the elbow joint challenged by inverted pendulum loading  

Microsoft Academic Search

The stiffness of activated muscles may stabilize a loaded joint by preventing perturbations from causing large displacements and injuring the joint. Here the elbow muscle recruitment patterns were compared with the forearm loaded vertically (a potentially unstable inverted pendulum configuration) and with horizontal loading.Eighteen healthy subjects were studied with the forearm vertical and supinated and the elbow flexed approximately 90°.

Ian A. F Stokes; Mack G Gardner-Morse



Strategies used to stabilize the elbow joint challenged by inverted pendulum loading  

Microsoft Academic Search

The sti!ness of activated muscles may stabilize a loaded joint by preventing perturbations from causing large displacements and injuring the joint. Here the elbow muscle recruitment patterns were compared with the forearm loaded vertically (a potentially unstable inverted pendulum con\\

Ian A. F. Stokes; Mack G. Gardner-Morse



Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control  

Microsoft Academic Search

We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to

A. Biewener; M. Daley



Orientation of the "Lisfranc screw".  


The reduction and stabilization of diastases between the medial cuneiform and the base of second metatarsal after a Lisfranc ligament injury is a crucial objective in the open reduction and internal fixation of these injuries. To achieve this objective, a single screw is used. The present practice is to insert the screw directed from the medial cuneiform bone into the base of the second metatarsal. This technique trick describes an easier method of insertion of the screw and one that possibly provides a better fixation. PMID:22549028

Panchbhavi, Vinod K



Surgeon Perception of Cancellous Screw Fixation.  


OBJECTIVES:: The ability of surgeons to optimize screw insertion torque in nonlocking fixation constructs is important for stability, particularly in osteoporotic and cancellous bone. This study evaluated screw torque applied by surgeons during synthetic cancellous fixation. It evaluated the frequency that screws were stripped by the surgeon, factors associated with screw stripping, and the ability of surgeons to recognize it. METHODS:: Ten surgeons assembled screw and plate fixation constructs into three densities of synthetic cancellous bone while screw insertion torque and axial force were measured. For each screw, the surgeon recorded a subjective rating as to whether or not the screw had been stripped. Screws were then advanced past stripping and stripped screws were identified by comparing the insertion torque applied by the surgeon to the measured stripping torque. RESULTS:: Surgeons stripped 109 of 240 screws (45.4%) and did not recognize stripping 90.8% of the time that it occurred. The tendency to strip screws was highly variable among individual surgeons (ranging from 16.7% to 83.3% stripped, p < 0.0001) and did not correlate to synthetic bone density in the range tested (p = 0.186), nor to rank as resident or attending surgeon (p = 0.437). Screws that were correctly recognized as stripped retained a mean 55.0% of maximum torque, less than when stripping was not recognized (79.6%, p = 0.005). CONCLUSIONS:: Surgeon perception is not reliable at preventing and detecting screw stripping at clinical torque levels in synthetic cancellous bone. Less aggressive insertion or standardized methods of insertion may improve the stability of nonlocking screw and plate constructs. PMID:23782959

Stoesz, Michael J; Gustafson, Peter A; Patel, Bipinchandra; Jastifer, James R; Chess, Joseph L



Characterization of the torque limits and clamping force relationships for small stainless steel screws in tensile loaded joints of various metals  

SciTech Connect

This study originated during the design of ChemCam, a Laser Induced Breakdown Spectroscopy (LIBS) and imaging instrument being developed for NASA's Mars Science Lab Rover. The mission needs for miniaturization, reduced weight, high reliability, minimal use of thread locking compounds, and the ability to handle harsh environmental conditions dictated the use of small, high strength screws to be threaded into a variety of metal alloys including Be-S200f, Al-6061-T6, Mg-ZK60A-T5, and Ti-6Al-4V The lack of a credible fastener torque database for small (No.0 through No.8) high strength stainless steel screws in various parent materials, led to the development of an experimental program to characterize the following: (A) The screw torque value versus angular rotation (which indicates yielding in the screw or parent material) as a function of screw diameter, screw head configuration, depth of thread engagement, type of parent material, type of surface treatment on parent material, presence of thread locking compound, repeatable threaded hole use, and degree of screw pedigree. (B) The relationship between fastener torque and clamping force for a subset of the above mentioned variables. The database generated from this study will serve as a design reference for utilizing small stainless steel fasteners and provide trending information for other researchers who may be interested in broadening its range of parameters. This paper reviews the related fastener torque and clamping force information from the literature, describes the experimental screw torque and clamping force monitoring equipment, presents the test matrix and experimental procedures, and discusses the empirical results.

Bernardin, John D [Los Alamos National Laboratory; Flores, Eugene M [Los Alamos National Laboratory



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



Do facet screws provide the required stability in lumbar fixation? A biomechanical comparison of the Boucher technique and pedicular fixation in primary and circumferential fusions  

Microsoft Academic Search

BackgroundTransfacet pedicle screws are scarcely used in primary posterior fixation, and have limited use unilaterally or with existing anterior instrumentation. Nevertheless, the incomplete literature suggests equivalent or better performance of ipsilateral, bilateral, facet screws compared to bilateral pedicle screws.

Amit Agarwala; Brandon Bucklen; Aditya Muzumdar; Mark Moldavsky; Saif Khalil



NSDL National Science Digital Library

Hinge joints move only in one direction, ball-and-socket joints are free to rotate in all directions, and gliding joints are able to move forward, backward, and side to side, but do not rotate freely.

Olivia Worland (Purdue University;Biological Sciences)



Biomechanical effects of screw fixation in second mandibular reconstruction plate.  


The purpose of this study was to investigate biomechanical effects of second reconstruction plate with different combinations of fixed screws in patient with mandibular tumor resection by three-dimensional finite element analysis (FEA). The FEA models were consisted of defected mandible, reconstruction plate with different screw holes, and bone screws. The results indicated that application of the second reconstruction plate appeared to increase stability and decrease stress magnitude on the plates and screws accompanying with increasing screw number. For clinical cost consideration in usage of the second reconstruction plate, the conclusion showed that the second reconstruction plate could offer a better mechanical efficacy accompanying with increase of screw quantity, but single screw applied for the second plate fixation to defected mandible of tumor resection was enough to stabilize without increase of screw quantities. PMID:24110400

Chang, Ya-Wen; Liu, Pao-Hsin



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



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

PubMed Central

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

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



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


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

Röhl, Klaus; Ullrich, Bernhard; Huber, Gerd; Morlock, Michael M



Axial loading cross screw fixation for the Austin bunionectomy.  


The Austin procedure has become a common method of osteotomy for the correction of hallux abductovalgus when indicated. The V-type configuration is intrinsically stable but not without complications. One complication encountered is rotation and/or displacement of the capital fragment. We present the use of an axial loading screw in conjunction with a dorsally placed compression screw. The benefit to this technique lies in the orientation of the axial loading screw, because it is directed to resist the ground reactive forces while also providing a second point of fixation in a crossing screw design. In a head-to-head biomechanical comparison, we tested single dorsal screw fixation versus double screw fixation, including both the dorsal and the axial loading screws in 10 metatarsal Sawbones(®) (Pacific Research Laboratories Inc, Vashon, WA). Five metatarsals received single dorsal screw fixation and five received the dorsal screw and the additional axial loading screw. The metatarsals were analyzed on an Instron compression device for comparison; 100% of the single screw fixation osteotomies failed with compression at an average peak load of 205 N. Four of five axial loading double screw fixation osteotomies did not fail. This finding suggests that the addition of an axial loading screw providing cross screw orientation significantly increases the stability of the Austin osteotomy, ultimately decreasing the likelihood of displacement encountered in the surgical repair of hallux abductovalgus. PMID:21621434

Rigby, Ryan B; Fallat, Lawrence M; Kish, John P



Effects of lateral ligament sectioning on the stability of the ankle and subtalar joint.  


Patients with subtalar joint instability are often diagnosed with ankle instability. Only after a prolonged period of time in which a patient does not improve after treatment for ankle instability is subtalar joint instability considered. To develop a clinically relevant method to diagnose subtalar joint instability, the kinematics of the simulated unstable subtalar joint were examined. A 6 degree-of-freedom positioning and loading device was developed. Plantarflexion/dorsiflexion, inversion/eversion, and internal/external rotation were applied individually or as coupled motions along with an anterior/posterior drawer. Kinematic data were collected from sensors attached to the calcaneus, talus, and tibia by keeping all the ligaments intact, and by serially sectioning anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), cervical ligament, and talocalceneal interosseous ligament. Kinematic results were reported using Euler angles. The ATFL and CFL contributed talocrural instability, similar to previous studies. The interosseous ligament was the greatest contributor to subtalar joint stability. The hindfoot motion (calcaneus relative to tibia) showed significant increases in motion when the ankle and/or subtalar joint was made to be unstable. Therefore, it is difficult to diagnose subtalar joint instability on physical examination alone. PMID:21445995

Ringleb, Stacie I; Dhakal, Ajaya; Anderson, Claude D; Bawab, Sebastain; Paranjape, Rajesh



Changes in joint stability with muscle contraction measured from transmission of mechanical vibration.  


A non-invasive in vivo technique was developed to evaluate changes in wrist joint stability properties induced by increased co-activation of the forearm muscles in a gripping task. Mechanical vibration at 45, 50 and 55 Hz was applied to the radial head in ten healthy volunteers. Vibrations of the styloid process of the radius and the distal end of the metacarpal bone of the index finger were measured with triaxial accelerometers. Joint stability properties were quantified by the transfer function gain between accelerations on either side of the wrist-joint. Gain was calculated with the muscles at rest and at five force levels ranging from 5% to 25% of maximum grip force (%MF). During contraction the gain was significantly greater than in control trial (0%MF) for all contractions levels at 45 and 50 Hz and a trend for 15%MF and higher at 55 Hz. Group means of contraction force and gain were significantly correlated at 45 (R(2)=0.98) and 50 Hz (R(2)=0.72), but not at 55 Hz (R(2)=0.10). In conclusion, vibration transmission gain may provide a method to evaluate changes in joint stability properties. PMID:16263128

Feltham, M G; van Dieën, J H; Coppieters, M W; Hodges, P W



Role of individual lower limb joints in reactive stability control following a novel slip in gait  

PubMed Central

Instability after slip onset is a key precursor leading to subsequent falls during gait. The purpose of this study was to determine the impact of reactive muscular response from individual lower limb joints on regaining stability control and impeding a novel, unannounced slip during the ensuing single-stance phase. Ten young adults’ resultant moments at three lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, were optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamics model. Systematic alteration of the moments of each joint caused corresponding changes in the displacement and velocity of the center of mass (COM) and base of support (BOS) (i.e., their state variables, xCOM, ?COM, xBOS, ?BOS), and in the COM stability. The model simulation revealed that these joints had little influence on ?COM, but had substantial impact on ?BOS reduction, leading to improving the COM stability, mostly from knee flexors, followed by hip extensors, of the slipping limb. Per unit reactive increase in normalized knee flexor or hip extensor moments and per unit reactive reduction in commonly observed plantar-flexor moments could lead to as much as 57.72 ± 10.46 or 22.33 ± 5.55 and 13.09 ± 2.27 units of reduction in normalized ?BOS, respectively. In contrast, such influence was negligible from the swing limb during this period, irrespective of individual variability.

Yang, Feng; Pai, Yi-Chung



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.

Riemann, Bryan L.; Lephart, Scott M.



Posterior Cervical Bone Screws  

Center for Biologics Evaluation and Research (CBER)

Text Version... Smith MD et al, Spine 1993: 18, 1984. Page 3. POSTERIOR CERVICAL BONE SCREWS ... Page 4. POSTERIOR CERVICAL BONE SCREWS ... More results from


U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Volume 2. Glossary: Plastic Films and Soil Stabilizers.  

National Technical Information Service (NTIS)

This report covers many joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydrotechnical Construction. Vol. II is the Russian/English, English/Russian Glossa...

L. O. Timblin F. V. Reckner



U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Volume 4. Laboratory and Field Studies in Soil Stabilizers.  

National Technical Information Service (NTIS)

This report covers many joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydrotechnical Construction. Vol. IV reports on the major Laboratory and Field Stud...

T. G. Zhordania W. R. Morrison W. T. Plass C. R. Styron



Complications of transpedicular screw fixation in the cervical spine  

Microsoft Academic Search

Today, posterior stabilization of the cervical spine is most frequently performed by lateral mass screws or spinous process wiring. These techniques do not always provide sufficient stability, and anterior fusion procedures are added secondarily. Recently, transpedicular screw fixation of the cervical spine has been introduced to provide a one-stage stable posterior fixation. The aim of the present prospective study is

E. Kast; K. Mohr; H.-P. Richter; W. Börm



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


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



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



U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Volume 1. Executive Summary.  

National Technical Information Service (NTIS)

This report covers many joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydrotechnical Construction. Vol. I Executive Summary - gives a brief overview of t...

F. V. Reckner L. O. Timblin J. P. McGarvey W. J. Ochs J. G. Starbuck



The Joint Effect of Network Topology and Update Functions on the Stability of Boolean Networks  

NASA Astrophysics Data System (ADS)

Boolean networks are dynamical systems commonly used to model biological systems such as gene regulatory networks and neural networks. In a Boolean network, the state of each node can take one of two values, which is updated at discrete time steps using an update function that depends only on the states of its inputs on the previous time step. We study the stability of attractors in a Boolean network with respect to small perturbations. While recent past work has addressed the separate effects on stability of nontrivial network topology and update functions, only very crude information exists on how these effects interact. We present a general solution for finding the stability of Boolean networks, considering the joint effects of network topology and update functions. In particular, we show that the predictions of our approach agree with simulations of Boolean networks with threshold update functions.

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



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


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



Cancellous Screw with Tension Band Wiring for Fractures of the Olecranon  

PubMed Central

Background: Olecranon fractures are one of the most commonly seen orthopaedic injuries in the emergency room. The K-wire which is used in the AO Tension Band Wiring (TBW) technique resists the shear better than the figure of eight wire alone, but, it does not add compression to the fixation strength. But, the cancellous screw plus the tension band wire, in combination, provides the strength of fixation i.e., by converting the tensile force to a compressive force at the fracture site, with additional resistance to the displacement due to the lag screw compression. Objective: To clinically evaluate the result of the cancellous screw with tension band wiring for fractures of the olecranon.To assess the elbow joint motion and stability after the procedure. Material and Methods: Tweenty five cases of fractures of the olecranon which were treated by using 6.5mm AO cancellous screws with a screw length of 80-105mm with a 16 gauge TBW, were evaluated . All the cases were followed up and the results were analyzed by using a 19 point scale. Results: The results which were obtained in our series were excellent in 15(60%) patients, good in 3(12%) patients and fair in 7(28%) patients and there were no poor results. Conclusion: The technique of open reduction and internal fixation with a 6.5mm AO cancellous screw and TBW, is a simple and effective means of treating fractures of the olecranon and it is based on the biomechanical principle of sound.

S M, Raju; Gaddagi, Rashmi A



The Effects of a Functional Elbow Brace on Medial Joint Stability: A Case Study  

PubMed Central

Medical elbow ligament sprains in athletics can be traumatic and disabling. In this case report, we outline the effect of a prototype functional elbow brace on joint stability in a female collegiate javelin thrower with an ulnar collateral ligament sprain. A valgus force to both elbows was applied using graded stress radiography (Telos GA-II/E stress device) at 0, 5, 10, and 15 kiloPascals (kPa) of pressure. The increase in gap width between the coronoid process and the medial epicondyle was measured from anteroposterior radiographs to determine medial displacement. The brace resulted in less displacement in both injured and noninjured ulnar collateral ligament; injured ulnar collateral ligament demonstrated greater displacement regardless of condition. The brace restored medial stability to the elbow joint by 49%, 38%, and 35% at 5, 10, and 15 kPa of pressure, respectively. The application of the brace may be useful in athletes with ulnar collateral ligament injuries. ImagesFig 1Fig 2

Pincivero, Danny M.; Rijke, Arie M.; Heinrichs, Kristinn; Perrin, David H.



Stabilization of the sacroiliac joint with the SI-Bone surgical technique.  


Although the motion of the sacroiliac joints (SIJ) is minimal, pain can originate from the SIJ on mechanical loading and affect walking, sitting and sleep patterns. The SIJ refers to the pair of joints inferior to the L5-S1 joint, and functions as the inferior adjacent level after a L5-S1 fusion. SIJ pain has a clinical overlay of symptoms often similar to low back pain (LBP) generated by the lumbar spine. The differential diagnosis in any patient with LBP should include the triad of low back, SIJ, and hip. SIJ pain is also a known cause of residual LBP after successful lumbar fusion. Relief of the patient's pain with a diagnostic SIJ block verifies the SIJ as the site of the pain generator. The SI-bone technique of stabilization of the SIJ is a true minimally invasive surgical technique performed through an initial small skin incision and then over pins, with the aid of fluoroscopy in three orthogonal axes with one axis parallel to the posterior sacral cortical line at the S1 to S2 region. The fluoroscopy procedure includes the following steps: 1) pre-op plan of the desired 3 implant trajectories to account for the anatomic variations; 2) placement of 3 Steinman pins at these trajectories across the SIJ starting in a small skin incision; 3) drill, broach and then implant placement as a cannulated system. All these steps are performed with the assistance of fluoroscopy in all three imaging planes - lateral, inlet and outlet views. The SI-Bone implants are triangular shaped titanium and have a rough surface for immediate stability. This rough surface is believed to aid in the osteo-fixation of the implants to the ilium and sacrum, as well as to long term fusion of the SIJ after its prolonged immobilization. The video can be found here: PMID:23829857

Geisler, Fred



Simplified and strong: abductor pollicus longus suspension arthroplasty with biotenodesis screw fixation in the base of the index metacarpal.  


Surgical treatment of thumb basal joint arthritis is aimed at pain relief, restoration of pinch strength, and stability. We describe a variation of the abductor pollicus longus (APL) suspension arthroplasty originally described by Thompson, which maximizes strength of repair and is technically simple to perform. The technique consists of a trapeziectomy followed by resection of a slip of the APL and secure docking of the tendon into the base of the index metacarpal base. Stability is enhanced with a 3.0 mm biotenodesis screw. From March 2009 to September 2011, 50 patients were treated at our institution. Early results showed consistent pain relief, functional improvement, and minimal complications. The data support APL suspension arthroplasty with tenodesis screw fixation as a safe and effective treatment for CMC arthritis. PMID:23423237

Julien, Terrill P; Earp, Brandon E; Blazar, Philip E



CT- and fluoroscopy-guided percutaneous screw fixation of a "carrot-stick" spinal fracture in an elderly man with ankylosing spondylitis.  


We present a case of percutaneous fixation of a "carrot-stick" spinal fracture in an elderly patient with ankylosing spondylitis (AS). A surgical stabilization was not possible in this 83-year-old man with comorbidities. Under local anesthesia, percutaneous screw fixation of a transdiscal shear fracture at the level T10-T11 was performed using computed tomography (CT) and fluoroscopy guidance. Two 4.0-mm Asnis III cannulated screws were placed to fix facet joints using transfacet pedicle pathway. The procedure time was 30 min. Using the visual analog scale (VAS), pain decreased from 10, preoperatively, to 1 after the procedure. Radiographic fusion was observed at a 3-month post-procedural CT scan. CT- and fluoroscopy-guided percutaneous screw fixation of spinal fractures could potentially be an alternative to surgery in elderly AS patients with poor performance status. PMID:23842576

Huwart, Laurent; Amoretti, Nicolas



Acceleration-based joint stability parameters for total knee arthroplasty that correspond with patient-reported instability.  


There is no universally accepted definition of human joint stability, particularly in nonperiodic general activities of daily living. Instability has proven to be a difficult parameter to define and quantify, since both spatial and temporal measures need to be considered to fully characterize joint stability. In this preliminary study, acceleration-based parameters were proposed to characterize the joint stability. Several time-statistical parameters of acceleration and jerk were defined as potential stability measures, since anomalous acceleration or jerk could be a symptom of poor control or stability. An inertial measurement unit attached at the level of the tibial tubercle of controls and patients following total knee arthroplasty was used to determine linear acceleration of the knee joint during several activities of daily living. The resulting accelerations and jerks were compared with patient-reported instability as determined through a standard questionnaire. Several parameters based on accelerations and jerks in the anterior/posterior direction during the step-up/step-down activity were significantly different between patients and controls and correlated with patient reports of instability in that activity. The range of the positive to negative peak acceleration and infinity norm of acceleration, in the anterior/posterior direction during the step-up/step-down activity, proved to be the best indicators of instability. As time derivatives of displacement, these acceleration-based parameters represent spatial and temporal information and are an important step forward in developing a definition and objective quantification of human joint stability that can complement the subjective patient report. PMID:23886970

Roberts, Dustyn; Khan, Humera; Kim, Joo H; Slover, James; Walker, Peter S



Treatment of Symptomatic Distal Interphalangeal Joint Arthritis with Percutaneous Arthrodesis: a Novel Technique in Select Patients  

PubMed Central

Arthrodesis of the distal interphalangeal (DIP) joint is a reliable means of achieving pain relief in a symptomatic DIP joint afflicted by a variety of degenerative, inflammatory, or posttraumatic conditions. Successful arthrodesis is more reproducible when rigid compression of the joint is achieved. The emergence of an increasing number of commercially available headless or variable pitch compression screws reflects the growing trend among hand surgeons to utilize rigid stabilization of the DIP joint so that motion at more proximal levels can be initiated immediately without affecting arthrodesis rates. Successful closed percutaneous DIP arthrodesis can be achieved in a patient with hypertrophic osteoarthropathy, passively correctable deformity, and patients at increased risk for perioperative soft tissue complications associated with open arthrodesis. We present a novel percutaneous DIP fusion technique utilizing a cannulated headless compression screw in a select group of patients. The sagittal plane diameters of the distal and middle phalanges are templated. Cannulated headless compression screws, 2.4 and 3.0 mm, with short or long terminal threads at the leading end of the screw are selected based upon patient-specific anatomic considerations. Pain-free status and radiographic fusion were achieved in both patients (gout arthropathy, n?=?1; posttraumatic arthritis, n?=?1) at an average of 6 weeks postoperatively. Our current indications, along with pearls and pitfalls with this technique, are reviewed. In select patients, this percutaneous DIP joint arthrodesis is advantageous in comparison with open fusion techniques.

Ruchelsman, David E.; Hazel, Antony



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



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



Effects of EMG processing on biomechanical models of muscle joint systems: Sensitivity of trunk muscle moments, spinal forces, and stability  

Microsoft Academic Search

Biomechanical models are in use to estimate parameters such as contact forces and stability at various joints. In one class of these models, surface electromyography (EMG) is used to address the problem of mechanical indeterminacy such that individual muscle activation patterns are accounted for. Unfortunately, because of the stochastical properties of EMG signals, EMG based estimates of muscle force suffer

Didier Staudenmann; Jim R. Potvin; Idsart Kingma; Dick F. Stegeman; Jaap H. van Dieën



ACROMIOCLAVICULAR DISLOCATIONS--Open Reduction with Screw Fixation  

PubMed Central

Athletes with complete separation of the acromioclavicular joint were uniformly restored to full athletic competence by an operation consisting of direct repair of the involved ligamentous structures with temporary fixation by a metallic lag screw approximating the clavicle to the coracoid. The metallic fixation was left in place an average of eight weeks and the screw was then removed under local anesthesia. A number of professional and collegiate football players returned to the rigors of football with no discomfort or disability.

Meier, A. W.; Grannis, W. R.; Tanner, J. B.



The intramedullary hip screw.  


The intramedullary hip screw is a short intramedullary nail with interlocking screws that can be used to treat subtrochanteric and intertrochanteric femur fractures. This nail, which has the biomechanical advantage of being an intramedullary appliance but can be placed percutaneously, is inserted under fluoroscopic control with the patient on a fracture table. Reaming is not usually necessary. In an initial limited series, complication rates are comparable with existing techniques. Possible future concepts and developments are discussed. PMID:10148378

King, D H; Seligson, D



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.

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



Helical screw viscometer  


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.



Innovation: the induction heated screw.  

National Technical Information Service (NTIS)

The Research and Development Division at EDF has developed an original technique for heating, drying or baking powder products: the induction heated Archimedes screw. Its main characteristic is simultaneous heating of the screw and the sleeve. (author). 4...

B. Paya



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


Factors affecting the accurate placement of percutaneous pedicle screws during minimally invasive transforaminal lumbar interbody fusion.  


We retrospectively evaluated 488 percutaneous pedicle screws in 110 consecutive patients that had undergone minimally invasive transforaminal lumbar interbody fusion (MITLIF) to determine the incidence of pedicle screw misplacement and its relevant risk factors. Screw placements were classified based on postoperative computed tomographic findings as "correct", "cortical encroachment" or as "frank penetration". Age, gender, body mass index, bone mineral density, diagnosis, operation time, estimated blood loss (EBL), level of fusion, surgeon's position, spinal alignment, quality/quantity of multifidus muscle, and depth to screw entry point were considered to be demographic and anatomical variables capable of affecting pedicle screw placement. Pedicle dimensions, facet joint arthritis, screw location (ipsilateral or contralateral), screw length, screw diameter, and screw trajectory angle were regarded as screw-related variables. Logistic regression analysis was conducted to examine relations between these variables and the correctness of screw placement. The incidence of cortical encroachment was 12.5% (61 screws), and frank penetration was found for 54 (11.1%) screws. Two patients (0.4%) with medial penetration underwent revision for unbearable radicular pain and foot drop, respectively. The odds ratios of significant risk factors for pedicle screw misplacement were 3.373 (95% CI 1.095-10.391) for obesity, 1.141 (95% CI 1.024-1.271) for pedicle convergent angle, 1.013 (95% CI 1.006-1.065) for EBL >400 cc, and 1.003 (95% CI 1.000-1.006) for cross-sectional area of multifidus muscle. Although percutaneous insertion of pedicle screws was performed safely during MITLIF, several risk factors should be considered to improve placement accuracy. PMID:21720727

Kim, Moon-Chan; Chung, Hung-Tae; Cho, Jae-Lim; Kim, Dong-Jun; Chung, Nam-Su



U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Volume 3. Laboratory and Field Studies in Plastic Films.  

National Technical Information Service (NTIS)

This report covers many joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydrotechnical Construction. Vol. III reports on the major Laboratory and Field Stu...

V. A. Krupin P. A. Suhorukov W. R. Morrison J. G. Starbuck



U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Flexible Structures: Reference Manual on Design.  

National Technical Information Service (NTIS)

The report covers one of several joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydro technical Construction (U.S. Project No. 01.120401-U.S.S.R. Project ...



Intertrochanteric fractures in elderly high risk patients treated with Ender nails and compression screw  

PubMed Central

Background: Ender and Simon Weidner popularized the concept of closed condylocephlic nailing for intertrochanteric fractures in 1970. The clinical experience of authors revealed that Ender nailing alone cannot provide secure fixation in elderly patients with osteoporosis. Hence we conducted a study to evaluate the efficacy of a combined fixation procedure using Ender nails and a cannulated compression screw for intertrochanteric fractures. Materials and Methods: 76 patients with intertrochanteric fractures were treated using intramedullary Ender nails and cannulated compression screw from January 2004 to December 2007. The mean age of the patients was 80 years (range 70-105 years).Using the Evan’s system of classification 49 were stable and 27 unstable fractures. Inclusion criteria was high risk elderly patients (age > 70 years) with intertrochanteric fracture. The exclusion criteria included patients with pressure sores over the trochanteric region. Many patients had pre-existing co-morbidities like diabetes mellitus, hypertension, COPD, ischemic heart disease, CVA and coronary artery bypass surgery. The two Ender nails of 4.5mm each were passed across the fracture site into the proximal neck. This was reinforced with a 6.5 mm cannulated compression screw passed from the sub trochanteric region, across the fracture into the head. Results: The mean follow-up was 14 months (range 9-19 months) Average time to fracture union was 10 weeks (range 6-16 weeks). The mean knee ROM was 130° (± 5°). There was no case of nail penetration into hip joint. In five cases with advanced osteoporosis there was minimal migration of Ender nails distally. Conclusions: The Ender nailing combined with compression screw fixation in cases of intertrochanteric fractures in high risk elderly patients could achieve reliable fracture stability with minimal complications.

Gangadharan, Sidhartha; Nambiar, MR



Interference screw fixation using bioabsorbable screw as void filler.  


We evaluated interference screw fixation in a plug-tunnel construct using bioabsorbable screws as void fillers with different percentages of the screw removed. Nine-millimeter tunnels in a closed-cell foam block were filled with a 10-mm bioabsorbable screw, and 10-mm revision tunnels were placed in parallel with tunnel overlap resulting in removal of 10%, 25%, or 50% of the screw diameter. Synthetic bone plugs were fashioned to fit 10-mm tunnels. In all groups, the plugs were secured in standard interference fixation with a 9-mm metal screw between the void-filling bioabsorbable screw and plug. Failure loads for the control group (no revision tunnel) averaged 926 +/- 44 N, 10% (1024 +/- 129 N) and 25% (932 +/- 129 N) groups were not significantly different; failure load in the 50% diameter group (780 +/- 72 N) was significantly lower than all other groups (p < 0.001). Using a bioabsorbable screw as void filler provided mean load to failure not different from that of standard reconstruction when 10 and 25% of the diameter of the void-filling screw was removed. Load to failure was significantly lower when 50% of the void-filling screw diameter group was removed. This may be applicable in anterior cruciate ligament reconstruction where a previous tunnel void has to be addressed. PMID:22303758

Fullick, Robert; Parks, Brent; Hinton, Richard



Benchtop comparison of a novel dynamic compression screw to a standard cortical screw: compression integrity and gap size over time during simulated resorption.  


Literature reports the incidence of failed isolated foot and ankle fusions as up to 23%. A contributing factor is the natural bone resorption, which occurs resulting in loss of compression and gapping at the fusion site when standard static compression plates and screws are used. However, an innovative dynamic compression screw may provide lasting compression despite resorption. This benchtop study shows that the FxDEVICES spring-loaded dynamic POGO screw maintains more compression and more consistent compression rate during simulated resorption, as compared with a standard compression screw. The novel screw maintained much greater compression strength within the first millimeter of simulated resorption (13.57 vs 4.38 lb) and maintained greater compression strength at the test completion (1.14 vs 0 lb). The novel screw revealed a more consistent resorption rate over the duration of the simulation. Clinically, this may result in more stability and improved fusion rates. PMID:23548586

Kinmon, Kyle; Garzon, Desiree; Tacktill, Jordan; Vassello, Wayne



Definition and classification of power system stability IEEE\\/CIGRE joint task force on stability terms and definitions  

Microsoft Academic Search

The problem of defining and classifying power system stability has been addressed by several previous CIGRE and IEEE Task Force reports. These earlier efforts, however, do not completely reflect current industry needs, experiences and understanding. In particular, the definitions are not precise and the classifications do not encompass all practical instability scenarios. This report developed by a Task Force, set

P. Kundur; J. Paserba; V. Ajjarapu; G. Andersson; A. Bose; C. Canizares; N. Hatziargyriou; D. Hill; A. Stankovic; C. Taylor; T. Van Cutsem; V. Vittal



Strength comparison of allogenic bone screws, bioabsorbable screws, and stainless steel screw fixation.  


Allogenic bone screws are new to the fixation market and have yet to be tested against current fixation materials. An in vitro comparison of the same sizes of stainless steel, bioabsorbable, and allogenic bone screws was undertaken to assess screw resistance to the forces of bending, pullout, and shear. Using aluminum plates to support the screws, forces up to 1000 Newtons were applied to six to eight samples of each type of screw. During each test, stainless steel screws withstood the maximum force that could be exerted by the testing apparatus without failing (bending, 113.9 +/- 11.8 N mean +/- SE; pullout 999.1 +/- 33.7 N; and shear, 997.5 +/- 108.8 N). In each test, compared to bioabsorbable screws, allogenic bone screws failed faster (pullout, allogenic: 12.4 +/- 1.1 seconds vs. bioabsorbable, 120.6 +/- 13.8 seconds; p = .001; bending, allogenic: 53.4 +/- 4.8 seconds vs. bioabsorbable, 201.9 +/- 11.1 seconds; p = .001; shear, allogenic 13.5 +/- 1.4 seconds vs. bioabsorbable, 43.8 +/- 0.9 seconds; p = .001) under equivalent (pullout: bioabsorbable, 385.0 +/- 18.4 N vs. allogenic, 401.0 +/- 35.9 N; p = .001) or lower (bending, allogenic: 4.7 +/- 0.2 N vs. bioabsorbable, 11.0 +/- 0.9 N; p = .675; shear, allogenic: 312.1 +/- 15.5 N vs. bioabsorbable 680.9 +/- 8.5 N; p = .001) loads, and in a highly variable fashion. Overall, the bioabsorbable screws withstood the forces of bending, pullout, and shear better than the allogenic screws, and stainless steel screws outperformed both bioabsorbable and allogenic screws. Despite these results, allogenic screws could still be useful in compliant patients who would benefit from their osteoconductive properties. PMID:11858609

Rano, James A; Savoy-Moore, Ruth T; Fallat, Lawrence M


Stabilization of the Dislocated Acromioclavicular Joint with Ligament Suture and Balser Hook Plate  

Microsoft Academic Search

Objective Reduction of dislocation and reconstruction of acromioclavicular joint by suturing the torn capsuloligamentous structures, temporary fixation with a Balser plate. Goal: restitution of form and function of shoulder girdle. Indications Primary acromioclavicular dislocation of Tossy type III or Rockwood type III in physically active patients. Acromioclavicular dislocations with additional muscle injuries of Rockwood type IV-VI. Remote painful dislocations without

Ewa Klara Folwaczny; Klaus Michael Stürmer



Stability analysis of a joint space control law for a two-manipulator system  

Microsoft Academic Search

The control problem for a truly cooperative manipulator system cannot be regarded as a simple extension of single manipulator control since additional complexity arises from the need for ensuring coordinated motion of the system. Recently, we have proposed a control strategy based on two stages, namely, kinematic inversion of a set of cooperative task variables and a joint space control

Fabrizio Caccavale; Pasquale Chiacchio; Stefano Chiaverini



Stability analysis of a joint space control law for a two-manipulator system  

Microsoft Academic Search

The control problem for a truly cooperative manipulator system cannot be regarded as a simple extension of single manipulator control since additional complexity arises from the need of ensuring coordinated motion of the system. Previously, we have proposed a control strategy based on two stages; namely, kinematic inversion of a set of cooperative task variables, and a joint space control

F. Caccavale; P. Chiacchio; S. Chiaverini



Pull-out strength of screws from cortical bone in the maxillo-facial region  

Microsoft Academic Search

The fixation of maxillofacial fractures is an important clinical procedure, which may be achieved by the attachment of plates across the fracture. The stability of the fracture will depend on the stiffness of the fracture fixation plates and the security of the fixation screws to the thin maxillofacial cortical bone. The design of screws, manufactured by Champy and AO were

J. C. Shelton; R. A. Loukota



The biomechanical influence of tibio-talar containment on stability of the ankle joint  

Microsoft Academic Search

Chronic ankle instability (CAI) is a frequent sport orthopaedic entity. Although many risk factors have been studied extensively,\\u000a little is known how it is influenced by the osseous joint configuration. Based on lateral X-rays, the radius of the talar\\u000a surface and the tibial coverage of the talus (sector ?) were measured on a DICOM\\/PACS system in 52 patients with CAI

Arno Frigg; Roman Frigg; Beat Hintermann; Alexey Barg; Victor Valderrabano



Role of rod diameter in comparison between only screws versus hooks and screws in posterior instrumentation of thoracic curve in idiopathic scoliosis.  


Since the introduction of Cotrel-Dubousset instrumentation in 1984, the correction techniques in scoliosis surgery have changed from Harrington principles of concave distraction to segmental realignment to a variety of possibilities including the rod rotation manoeuvres, and to segmental approximation via cantilever methods. Additionally, pedicle screw utilization in lumbar curves enhanced correction and stabilization of various deformities, and various studies have strongly supported the clinical advantages of lumbar pedicle screws versus conventional hook instrumentation. Pedicle screw constructs have become increasingly popular in the treatment of patients with spinal deformity. When applied to adolescent idiopathic scoliosis patients, pedicle screw fixation has demonstrated increased corrective ability compared with traditional hook/hybrid instrumentation. In our study, we do a retrospective review of idiopathic scoliosis patients (King 2-Lenke 1 B/C) treated with a selective thoracic posterior fusion using an all-screw construct versus a hybrid (pedicle screws and hooks) construct and, compare the percentage of correction of the scoliotic curves obtained with screws alone and screws and hooks. Special attention was given to the rod diameter and correction technique. Our results show that the percentage of correction of idiopathic thoracic scoliosis is similar when treating the scoliosis with rods and screws alone or with rods, screws and hooks; therefore, we and the majority of authors in the literature do not consider the rod section. This can be an important parameter in the evaluation of the superiority of treatment with screws only or screws and hooks. In our study, even if not of statistical significance, the better thoracic curve correction obtained with the hybrid group should be ascribed to the fact that in this group mostly 6 mm rods were used. PMID:21416281

Lamartina, Claudio; Petruzzi, Maria; Macchia, Marcello; Stradiotti, Paola; Zerbi, Alberto



Intramedullary screw fixation of proximal fifth metatarsal fractures: a biomechanical study.  


Intramedullary screw fixation is a popular technique for treatment of proximal fifth metatarsal fractures. The purpose of this study was to compare the fixation rigidity of a 5.5 mm partially threaded cannulated titanium screw, with presumed superior endosteal purchase, to a similar 4.5 mm screw. Acute fifth metatarsal fractures were simulated in cadavers, stabilized with intramedullary screws, and loaded to failure in three-point bending. The initial failure loads for the metatarsals fixed with 4.5 mm and 5.5 mm screws were not significantly different (332.4 N vs. 335.2 N, respectively), nor were the ultimate failure loads (849.8 N vs. 702.2 N, respectively). Based upon our results, maximizing screw diameter does not appear to be critical for fixation rigidity and may increase the risk of intraoperative or postoperative fracture. PMID:11503984

Shah, S N; Knoblich, G O; Lindsey, D P; Kreshak, J; Yerby, S A; Chou, L B



Scoliosis correction with pedicle screws in Duchenne muscular dystrophy  

PubMed Central

This report describes the spinal fixation with pedicle-screw-alone constructs for the posterior correction of scoliosis in patients suffering from Duchene muscular dystrophy (DMD). Twenty consecutive patients were prospectively followed up for an average of 5.2 years (min 2 years). All patients were instrumented from T3/T4 to the pelvis. Pelvic fixation was done with iliac screws similar to Galveston technique. The combination of L5 pedicle screws and iliac screws provided a stable caudal foundation. An average of 16 pedicle screws was used per patient. The mean total blood loss was 3.7 l, stay at the intensive care unit was 77 h and hospital stay was 19 days. Rigid stabilisation allowed immediate mobilisation of the patient in the wheel chair. Cobb angle improved 77% from 44° to 10°, pelvic tilt improved 65% from 14° to 3°. Lumbar lordosis improved significantly from 20° to 49°, thoracic kyphosis remained unchanged. No problems related to iliac fixation, no pseudarthrosis or implant failures were observed. The average percentage of predicted forced vital capacity (%FVC) of the patients was 55% (22–94%) preoperatively and decreased to 44% at the last follow-up. There were no pulmonary complications. One patient with a known cardiomyopathy died intraoperatively due to a sudden cardiac arrest. The rigid primary stability with pedicle screws allowed early mobilisation of the patients, which helped to avoid pulmonary complications.

Hahn, Frederik; Hauser, Dominik; Espinosa, Norman; Blumenthal, Stefan



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



Minimal access direct spondylolysis repair using a pedicle screw-rod system: a case series  

PubMed Central

Introduction Symptomatic spondylolysis is always challenging to treat because the pars defect causing the instability needs to be stabilized while segmental fusion needs to be avoided. Direct repair of the pars defect is ideal in cases of spondylolysis in which posterior decompression is not necessary. We report clinical results using segmental pedicle-screw-rod fixation with bone grafting in patients with symptomatic spondylolysis, a modification of a technique first reported by Tokuhashi and Matsuzaki in 1996. We also describe the surgical technique, assess the fusion and analyze the outcomes of patients. Case presentation At Cairo University Hospital, eight out of twelve Egyptian patients’ acute pars fractures healed after conservative management. Of those, two young male patients underwent an operative procedure for chronic low back pain secondary to pars defect. Case one was a 25-year-old Egyptian man who presented with a one-year history of axial low back pain, not radiating to the lower limbs, after falling from height. Case two was a 29-year-old Egyptian man who presented with a one-year history of axial low back pain and a one-year history of mild claudication and infrequent radiation to the leg, never below the knee. Utilizing a standardized mini-access fluoroscopically-guided surgical protocol, fixation was established with two titanium pedicle screws place into both pedicles, at the same level as the pars defect, without violating the facet joint. The cleaned pars defect was grafted; a curved titanium rod was then passed under the base of the spinous process of the affected vertebra, bridging the loose fragment, and attached to the pedicle screw heads, to uplift the spinal process, followed by compression of the defect. The patients were discharged three days after the procedure, with successful fusion at one-year follow-up. No rod breakage or implant-related complications were reported. Conclusions Where there is no evidence of frank spondylolisthesis or displacement and pain does not radiate below the knee, we recommend direct repair of the pars interarticularis fracture, especially in young active adults. We describe a modified form of the Buck screw procedure with a minimally invasive, image-guided method of pars interarticularis fixation. The use of image guidance simplifies the otherwise difficult visualization required for pars interarticularis screw placement and allows minimal skin and muscle dissection, which may translate into a more rapid postoperative recovery.



Stability of the ankle joint. Analysis of the function and traumatology of the ankle ligaments.  


The purpose of this study was to elucidate the function of the ligamentous structures of the ankle joint, the traumas in which they may rupture, and the types of instability caused by such ruptures. Most previous experimental investigations on the function of ankle ligaments have been performed on osteoligamentous preparations either by forcing a movement in the joint into more or less well-defined directions and observing the resulting injuries or else by cutting ligaments in various combinations and describing the resulting instability. As a rule, this has been done without inducing the increased mobility by a defined torque and without being able to demonstrate the instability continuously in all degrees of dorsi- or plantar flexion. On the basis of these previous studies, the anterior talofibular ligament appears to limit internal rotation, while its role in adduction of the talus has not been clarified. The calcaneofibular ligament per se does not seem to be a factor in adduction. True, there is not complete agreement in this respect, and a few authors have been able to rupture this ligament in isolation by forced adduction. The posterior talofibular ligament seems to restrict dorsiflexion, and perhaps it plays a role, in conjunction with the calcaneofibular ligament, in adduction when the ankle joint is in dorsiflexion. The anterior tibiofibular ligament, and the distal tibiofibular structures on the whole, are assumed to limit external rotation, but it has not been clarified whether they influence adduction and abduction in the ankle joint. Little has been reported about the individual structures which make up the deltoid ligament, as most authors have not distinguished them from each other. However, in combination with the anterior talofibular ligament, the tibiotalar ligament seems to limit the translatory forward gliding of the talus - the so-called anterior drawer sign - and together they presumably inhibit plantar flexion. It has not been possible to find any description of the function of the intermediate tibiotalar ligament, while the posterior tibiotalar ligament has been reported by one author to inhibit internal rotation. Judging by the literature, the function of the tibiocalcaneal ligament seems comprehensive, since it is reported to limit external rotation, dorsiflexion, as well as plantar flexion. The present investigations were divided into three phases: Phase 1 was concerned with elucidating the correlation of injuries to the lateral collateral ligaments to internal rotatory instability, talar tilt, and the anterior drawer sign.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3856377

Rasmussen, O



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.



Split spline screw  

NASA Astrophysics Data System (ADS)

A split spline screw type payload fastener assembly, including three identical male and female type split spline sections, is discussed. The male spline sections are formed on the head of a male type spline driver. Each of the split male type spline sections has an outwardly projecting load baring segment including a convex upper surface which is adapted to engage a complementary concave surface of a female spline receptor in the form of a hollow bolt head. Additionally, the male spline section also includes a horizontal spline releasing segment and a spline tightening segment below each load bearing segment. The spline tightening segment consists of a vertical web of constant thickness. The web has at least one flat vertical wall surface which is designed to contact a generally flat vertically extending wall surface tab of the bolt head. Mutual interlocking and unlocking of the male and female splines results upon clockwise and counter clockwise turning of the driver element.

Vranish, John M.



Arthrodesis of the distal interphalangeal joint: description of a new technique and clinical follow-up at 2 years  

Microsoft Academic Search

Introduction  Arthrodesis of the distal interphalangeal joint (DIPJ) is an accepted operative procedure to treat osteoarthritis, instability\\u000a and joint deformity. There is a wide spectrum of recommended operative techniques including cerclage wires, headless screws,\\u000a bio-resorbable pins and lag screws. Lag screw fixation remains one of the most accepted methods of fixation; however, problems\\u000a can occur in particular subsidence of the screw

L. C. Olivier; F. Gensigk; T. N. Board; D. Kendoff; U. Krehmeier; U. Wolfhard



Removal of an iliosacral screw entrapping the L5 nerve root after failed posterior pelvic ring fixation: a case report.  


We present a case of a pelvic ring fracture that was originally treated with anterior symphyseal plating and a misplaced percutaneous iliosacral screw. The anterior extraosseus portion of the misplaced 7.3-mm cannulated screw irritated the L5 nerve root, resulting in a radiculopathy. Subsequent surgery involved and mandated removing the bent screw after open identification and protection of the L5 nerve root to avoid further nerve damage; the sacroiliac joint was subsequently debrided and fused. This case represents a complication of acute percutaneous iliosacral screw fixation of pelvic ring injuries and the subsequent strategy for successful salvage. PMID:17621002

Weil, Yoram A; Nousiainen, Markku T; Helfet, David L



[Percutaneous cement-augmented screw fixation of bilateral osteoporotic sacral fracture].  


We describe the case of a 71-year-old woman who presented with persisting painful symptoms of the back and pelvis which had begun 4 weeks previously. A preceding trauma was plausibly excluded. Diagnostics showed a slightly dislocated bilateral sacral fracture with underlying osteoporosis also known as an insufficiency fracture. We performed a percutaneous and cement-augmented bilateral iliosacral joint revision using screws and 6 months after surgery, imaging showed a stable fracture with appropriate screw positions. PMID:23756785

Müller, F; Füchtmeier, B



Virtual placement of posterior C1-C2 transarticular screw fixation  

Microsoft Academic Search

We wanted to evaluate how often safe and effective posterior C1-C2 transarticular screw placement is realizable when it is\\u000a performed according to guidelines given in the literature. In 50 adult patients, computerized tomography scan data from C0\\u000a to C3 were transformed into a 3D spine model. Virtually, bilateral screws were placed from the medial third of the C2-C3 facet\\u000a joint

Peter Spangenberg; Volker Coenen; Joachim Michael Gilsbach; Veit Rohde



Helical Screw Expander Evaluation Project.  

National Technical Information Service (NTIS)

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 t...

R. Mckay



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


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


Biomechanical comparison of endplate forces generated by uniaxial screws and monoaxial pedicle screws.  


Current surgical treatment of idiopathic scoliosis involves the use of various segmental instrumentation. Various pedicle screws have allowed for improved correction. Although monoaxial screws have improved rotational control compared with polyaxial screws, their use may increase screw-bone interface or vertebral endplate forces if not inserted in an exactly straight trajectory. Uniaxial screws potentially decrease these forces while retaining the advantages of monoaxial screws with respect to better rotational control. The purpose of this study was to compare the vertebral endplate forces with monoaxial or uniaxial screws when being reduced to a rod. Thirty-two plastic, surrogate T11 vertebrae were prepared with monoaxial (n=16) or uniaxial (n=16) screws. Screw angles relative to inferior vertebral endplates were assessed with lateral radiographs. The vertebrae were fixed to a load cell, and loads were measured as the screw was reduced to a rod. Monoaxial screws demonstrated a linear progression of endplate force with increasing screw angle. Uniaxial screws demonstrated minimal endplate force until approximately 20°, coinciding with screwhead excursion angle. As this maximum excursion angle was passed, uniaxial screws demonstrated a force slope similar to the monoaxial screws.The measured endplate forces should be equivalent to forces at the screw-bone interface. The reduced force with uniaxial screws is expected to have less cranial-caudal plow potential as the screw is coupled to a rod for deformity correction. This could have potential implications for screw failure, especially in less dense bone. PMID:23027492

Essig, David A; Miller, Christopher P; Xiao, Ming; Ivancic, Paul; Jegede, Kola; Badrinath, Raghav; Smith, Brian G; Grauer, Jonathan N



Intramedullary screw fixation for midshaft fractures of the clavicle  

PubMed Central

Open intramedullary fixation of 37 fresh midshaft clavicular fractures in 35 patients was performed using a 6.5 partially threaded cancellous screw. Mean age was 38 years (range 18–65). The screw was inserted from the medial fragment after retrograde drilling of that fragment. Average follow-up period was 21 months (range 9–36). Radiological evidence of union was apparent in all cases within six to eight weeks after surgery (mean 7.8). Two cases had intraoperative failure of fixation, nine complained of subcutaneous prominence of the screw head, five experienced decreased sensation over the site of incision, and three had symptoms of frozen shoulder. In conclusion, the technique is simple, affordable and it does not require special instrumentation or implants. It allows intramedullary compression, stability, stress sharing, minimal periosteal stripping, and early recovery after surgery.



Force synchrony enhances the stability of rhythmic multi-joint arm coordination.  


Although rhythmic coordination has been extensively studied in the literature, questions remain about the correspondence of constraints that have been identified in the related contexts of inter-limb and intra-limb coordination. Here we used a 2-DOF robot arm which allows flexible manipulation of forces to investigate the effect on coordination stability of intra-limb coordination of: (i) the synchrony of force requirements and (ii) the involvement of bi-functional muscles. Ten subjects produced simultaneous rhythmic flexion-extension (FE) and supination-pronation (SP) elbow movements in two coordination patterns: (1) flexion synchronized with supination/extension with pronation (in-phase pattern) and (2) flexion synchronized with pronation/extension with supination (anti-phase pattern). The movements were produced with five different settings of the robot arm: a neutral setting that imposed balanced force requirements, and four other settings that increased the force requirements for one direction in both DOF. When combined with specific coordination patterns, these settings created conditions in which either synchronous or alternate patterns of forcing were necessary to perform the task. Results showed that synchronous tasks were more stable than asynchronous tasks (P < 0.05). Within the synchronous tasks, some robot settings were designed to either increase or decrease the use of bi-functional muscles. Although there was no difference for the bi-functional muscle biceps brachii, the coordination was more stable for the condition in which the greatest force requirements corresponded to the mechanical action of the bi-functional pronator teres (P < 0.05). In conclusion, force synchrony increases the stability of rhythmic intra-limb coordination, but further research is needed to clarify the role of bi-functional muscles in this effect. PMID:21735246

Stosic, Jelena; Carroll, Timothy J; de Rugy, Aymar



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.



Stability analysis of H-mode pedestal and edge localized modes in a Joint European Torus power scan  

NASA Astrophysics Data System (ADS)

Simulations of three Joint European Torus [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] type I ELMy high-confinement discharges in a power scan are carried out using the JETTO integrated modeling code [M. Erba et al., Plasma Phys. Controlled Fusion 39, 261 (1997)] with predictive core and pedestal models, which include the effect of edge localized modes (ELMs). It is found that current-driven peeling modes trigger the ELM crashes in these discharges and, as a result, yield an explanation of the experimentally observed increase in pedestal height with heating power. After each ELM crash, the pressure gradient and the related bootstrap current density at the edge of plasma rapidly increase with increasing heating power, while the total current density rises only slowly because the total current density is impeded by a back electromotive force. Hence, as the heating power is increased, the pedestal pressure can rise to higher values during an ELM cycle before the current density reaches the level required for destabilization of the current-driven peeling modes. In addition, a stability analysis using the HELENA and MISHKA codes [A. B. Mikhailovskii et al., Plasma Phys. Rep. 23, 713 (1997)] is carried out in conjunction with these simulations. The analysis includes infinite-n ideal ballooning, finite-n ballooning, and low-n kink/peeling modes.

Onjun, Thawatchai; Kritz, Arnold H.; Bateman, Glenn; Parail, Vassili; Wilson, Howard; Lönnroth, Johnny; Huysmans, Guido; Dnestrovskij, Alex



Biomechanical effects of polyaxial pedicle screw fixation on the lumbosacral segments with an anterior interbody cage support  

Microsoft Academic Search

BACKGROUND: Lumbosacral fusion is a relatively common procedure that is used in the management of an unstable spine. The anterior interbody cage has been involved to enhance the stability of a pedicle screw construct used at the lumbosacral junction. Biomechanical differences between polyaxial and monoaxial pedicle screws linked with various rod contours were investigated to analyze the respective effects on

Shih-Hao Chen; Ruey Mo Lin; Hsiang-Ho Chen; Kai-Jow Tsai



Comparative study of ankle arthrodesis using cross screw fixation versus anterior contoured plate plus cross screw fixation.  


Arthrodesis of the ankle joint is still the traditional treatment for symptomatic osteoarthritis. This comparative study was done to assess the functional outcome of open ankle fusion using either cross screw fixation (group A) or anterior contoured plate and cross screw fixation (group B) in a consecutive series of 22 patients. All the patients had the same inclusion criteria. All the patients in both groups underwent the same operative technique and were operated by the same surgeon. Mean follow-up was 26.8 months. The mean time to fusion was 18.8 weeks in group A and 16.8 weeks in group B (p = 0.046). The mean American Orthopaedic Foot and Ankle Society (AOFAS) Ankle and Hind foot score at the final follow-up was 79 in group A and 86 in group B (p = 0.23). Two patients in group A that went to non-union required re-arthrodesis using contoured plate and cross screw fixation; both attained eventual union. We conclude that anterior contoured plate plus cross screw fixation is a simple and reproducible technique for ankle arthrodesis that gives stable internal fixation and excellent clinical results. PMID:17260609

Kakarala, Gopikrishna; Rajan, Daniel T



Lumbosacral Fixation Using the Diagonal S2 Screw for Long Fusion in Degenerative Lumbar Deformity: Technical Note Involving 13 Cases  

PubMed Central

Placing instrumentation into the ilium has been shown to increase the biomechanical stability and the fusion rates, but it has some disadvantages. The diagonal S2 screw technique is an attractive surgical procedure for degenerative lumbar deformity. Between 2008 and 2010, we carried out long fusion across the lumbosacral junction in 13 patients with a degenerative lumbar deformity using the diagonal S2 screws. In 12 of these 13 patients, the lumbosacral fusion was graded as solid fusion with obvious bridging bone (92%). One patient had a rod dislodge at one S2 screw and breakage of one S1 screw and underwent revision nine months postoperatively. So, we present alternative method of lumbopelvic fixation for long fusion in degenerative lumbar deformity using diagonal S2 screw instead of iliac screw.

Kim, Hong-Sik; Baek, Seung-Wook; Lee, Sang-Hyun



Lumbosacral fixation using the diagonal s2 screw for long fusion in degenerative lumbar deformity: technical note involving 13 cases.  


Placing instrumentation into the ilium has been shown to increase the biomechanical stability and the fusion rates, but it has some disadvantages. The diagonal S2 screw technique is an attractive surgical procedure for degenerative lumbar deformity. Between 2008 and 2010, we carried out long fusion across the lumbosacral junction in 13 patients with a degenerative lumbar deformity using the diagonal S2 screws. In 12 of these 13 patients, the lumbosacral fusion was graded as solid fusion with obvious bridging bone (92%). One patient had a rod dislodge at one S2 screw and breakage of one S1 screw and underwent revision nine months postoperatively. So, we present alternative method of lumbopelvic fixation for long fusion in degenerative lumbar deformity using diagonal S2 screw instead of iliac screw. PMID:24009909

Park, Ye-Soo; Kim, Hong-Sik; Baek, Seung-Wook; Lee, Sang-Hyun



Fuzzy logic control of automated screw fastening  

Microsoft Academic Search

In this paper, we present an intelligent control strategy for automated screw fastening. In automated assembly processes, there are often found dedicated stations for various types\\/sizes of screw fastening. Problems found in current processes include cross-threading, screw jamming, slippage and the need to apply precise torque. The intelligent controller developed here supervises the integrated process of an electric driver mounted

Nitin Dhayagude; Zhiqiang Gao; Fouad Mrad



Fuzzy logic control of automated screw fastening  

Microsoft Academic Search

In this paper, we present an intelligent control strategy for automated screw fastening. In automated assembly processes, there is a large number of dedicated stations for various types\\/sizes of screw fastening. Problems found in current processes include cross-threading, screw jamming, slippage and the need to apply precise torque. The intelligent controller developed supervises the integrated process of an electric driver

Fouad Mrad; Zhiqiang Gao; Nitin Dhayagude



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




Cervical anterior transpedicular screw fixation. Part I: Study on morphological feasibility, indications, and technical prerequisites  

Microsoft Academic Search

Multilevel cervical spine procedures can challenge the stability of current anterior cervical screw-and-plate systems, particularly\\u000a in cases of severe three-column subaxial cervical spine injuries and multilevel plated reconstructions in osteoporotic bone.\\u000a Supplemental posterior instrumentation is therefore recommended to increase primary construct rigidity and diminish early\\u000a failure rates. The increasing number of successfully performed posterior cervical pedicle screw fixations have enabled

Heiko Koller; Axel Hempfing; Frank Acosta; Michael Fox; Armin Scheiter; Mark Tauber; Ulrich Holz; Herbert Resch; Wolfgang Hitzl



Biomechanical comparison of two headless compression screws for scaphoid fixation.  


This study compared compression generation between two headless compression screws: the Synthes 3.0-mm and the Acutrak standard. Twenty scaphoids were harvested from 10 pairs of fresh cadaveric forearms. A washer-shaped load cell was inserted between the halves of each scaphoid created by a simulated fracture via osteotomy. One scaphoid of each pair was tested with the Synthes and the other with the Acutrak. Parameters of interest were peak screw torque and fracture site compression. Differences in parameters of interest were checked for significance (p < .05) with paired t tests. No significant differences were shown in mean (+/- standard deviation) peak torque (57 +/- 28 Ncm vs. 55 +/- 32 Ncm; p < .84), compression immediately after insertion (119 +/- 54 N vs. 91 +/- 37 N; p < .15), or compression 5 min after insertion (32 +/- 30 N vs. 38 +/- 24 N; p < .61) between the Synthes and Acutrak screw fixations, respectively. The choice between these two screws to stabilize scaphoid waist fractures should be based on parameters other than compression generation, such as size, availability, cost, and ease of use of the implant. PMID:19995497

Pensy, Raymond A; Richards, Andrew M; Belkoff, Stephen M; Mentzer, Kurt; Andrew Eglseder, W



Metallurgical examination of gun barrel screws  

SciTech Connect

The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a live round is accidentally loaded into the chamber, a live round could be fired. Another concern is that if the blunt end of the screw begins to degrade by cracking, pieces could become small projectiles during firing. All screws used in firing 100 rounds or more exhibited some degree degradation, which progressively worsened as the number of rounds fired increased. (SEM, metallography, x-ray analysis, and microhardness were used.) Presence of cracks in these screws after 100 fired rounds is a serious concern that warrants the discontinued use of these screws. The screw could be improved by selecting an alloy more resistant to thermal and chemical degradation.

Bird, E.L.; Clift, T.L.



Ankle fusion using a 2incision, 3-screw technique  

Microsoft Academic Search

Objective  Reliable fusion and optimal correction of the alignment of the ankle joint using a 2-incision, 3-screw technique.\\u000a \\u000a \\u000a \\u000a Indications  Symptomatic osteoarthritis of the ankle joint after insufficient other treatment, severe deformity of the osteoarthritic ankle\\u000a joint, or salvation procedure after failed arthroplasty.\\u000a \\u000a \\u000a \\u000a \\u000a Contraindications  Active osteomyelitis, very poor soft tissues, or severe peripheral arterial occlusive disease.\\u000a \\u000a \\u000a \\u000a Surgical technique  Osteotomy and excision medial malleolus. Osteotomy, dislocation,

R. P. M. Hendrickx; G. M. M. J. Kerkhoffs; S. A. S. Stufkens; C. N. van Dijk; R. K. Marti



A Comparative Biomechanical Analysis of Stand Alone Versus Facet Screw and Pedicle Screw Augmented Lateral Interbody Arthrodesis: An In Vitro Human Cadaveric Model.  


STUDY DESIGN:: Cadaveric biomechanical study. OBJECTIVE:: To investigate the kinematic response of a stand-alone lateral lumbar interbody cage compared with supplemental posterior fixation with either facet or pedicle screws after lateral discectomy. SUMMARY OF BACKGROUND DATA:: Lateral interbody fusion is a promising minimally invasive fixation technique for lumbar interbody arthrodesis. The biomechanical stability of stand-alone cage placement compared with supplemental posterior fixation with either facet or bilateral pedicle screws remains unclear. METHODS:: A 6-degree of freedom spine simulator was used to test flexibility in 7 human cadaveric specimens. Flexion-extension, lateral-bending, and axial-rotation were tested in the intact condition, followed by destabilization through a lateral discectomy at L2-L3 and L4-L5. Specimens were then reconstructed at both operative segments in the following sequence: (1) lateral interbody cage placement; (2) either Discovery facet screws or the Viper F2 system using a transfacet-pedicular trajectory randomized to L2-L3 or L4-L5; and (3) removal of facet screw fixation followed by placement of bilateral pedicle screw instrumentation. Acute range of motion (ROM) was quantified and analyzed. RESULTS:: All 4 reconstruction groups, including stand-alone interbody cage placement, bilateral Discovery facet screws, the Viper F2 system, and bilateral pedicle screw-rod stabilization, resulted in a significant decrease in acute ROM in all loading modes tested (P<0.05). There were no significant differences observed between the 4 instrumentation groups (P>0.05). Although not statistically significant, the Viper F2 system resulted in greatest reduction of acute ROM in both flexion-extension and axial rotation versus all other treatments (P>0.05). CONCLUSIONS:: Stand-alone interbody cage placement results in a significant reduction in acute ROM at the operative segment in the absence of posterior supplemental fixation. If added fixation is desired, facet screw placement, including the Viper F2 facet screw system using an integrated compression washer and transfacet-pedicular trajectory, provides similar acute stability to the spinal segment compared with traditional bilateral pedicle screw fixation in the setting of lateral interbody cage deployment. PMID:23381181

Kretzer, Ryan M; Molina, Camilo; Hu, Nianbin; Umekoji, Hidemasa; Baaj, Ali A; Serhan, Hassan; Cunningham, Bryan W



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.

Umar, Muhammad; Baqai, Nadeem; Peck, Christopher



Helical screw expander evaluation project  

NASA Astrophysics Data System (ADS)

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.



Posterior spinal arthrodesis for adolescent idiopathic scoliosis using pedicle screw instrumentation: does a bilateral or unilateral screw technique affect surgical outcome?  


We reviewed 212 consecutive patients with adolescent idiopathic scoliosis who underwent posterior spinal arthrodesis using all pedicle screw instrumentation in terms of clinical, radiological and Scoliosis Research Society (SRS)-22 outcomes. In Group 1 (51 patients), the correction was performed over two rods using bilateral segmental pedicle screws. In Group 2 (161 patients), the correction was performed over one rod using unilateral segmental pedicle screws with the second() rod providing stability of the construct through two-level screw fixation at proximal and distal ends. The mean age at surgery was 14.8 years in both groups. Comparison between groups showed no significant differences with regard to age and Risser grade at surgery, pre- and post-operative scoliosis angle, coronal Cobb correction, length of hospital stay and SRS scores. Correction of upper thoracic curves was significantly better in Group 1 (p = 0.02). Increased surgical time and intra-operative blood loss was recorded in Group 1 (p < 0.001 and p = 0.04, respectively). The implant cost was reduced by mean 35% in Group 2 due to the lesser number of pedicle screws. Unilateral and bilateral pedicle screw techniques have both achieved excellent deformity correction in adolescent patients with idiopathic scoliosis, which was maintained at two-year follow-up. This has been associated with high patient satisfaction and low complication rates. PMID:23188910

Tsirikos, A I; Subramanian, A S



Minimally invasive dynamic hip screw for fixation of hip fractures  

PubMed Central

We compared a minimally invasive surgical technique to the conventional (open approach) surgical technique used in fixation of hip fractures with the dynamic hip screw (DHS) device. Using a case-control design (44 cases and 44 controls), we tested the null hypothesis that there is no difference between the two techniques in the following outcome measures: duration of surgery, time to mobilisation and weight bearing postoperatively, length of hospital stay, mean difference of pre- and postoperative haemoglobin levels, position of the lag screw of the DHS device in the femoral head, and the tip–apex distance. The minimally invasive DHS technique had significantly shorter duration of surgery and length of hospital stay. There was also less blood loss in the minimally invasive DHS technique. The minimally invasive DHS technique produces better outcome measures in the operating time, length of hospital stay, and blood loss compared to the conventional approach while maintaining equal fixation stability.

Ho, Michael; Garau, Giorgio; Walley, Gayle; Oliva, Francesco; Panni, Alfredo Schiavone; Longo, Umile Giuseppe



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



Treatment of displaced distal clavicle fractures with a single cortical screw.  


The authors retrospectively evaluated the effects of a single cortical screw in the open reduction and internal fixation of displaced distal clavicle fractures. Fifteen patients without associated acromioclavicular joint dislocation were treated by open reduction and internal fixation with a single cortical screw (4.5-mm diameter, 60-mm length) between 2004 and 2011. Mean follow-up was 39.2 months (range, 13-84 months). Reduction with a fracture gap of less than 1 mm and solid union were achieved in all cases. Delayed superficial infection developed in 1 patient. All other patients had good to excellent final Constant-Murley functional results. PMID:23464937

Lin, Hsi-Hsien; Wang, Chien-Shun; Chen, Cheng-Fong; Chiang, Chao-Ching; Huang, Ching-Kuei; Chen, Wei-Ming; Liu, Chien-Lin



21 CFR 872.4880 - Intraosseous fixation screw or wire.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Intraosseous fixation screw or wire. 872.4880 Section 872... § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...



21 CFR 872.4880 - Intraosseous fixation screw or wire.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Intraosseous fixation screw or wire. 872.4880 Section 872... § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended...



Control strategy for stabilizing force with goal-equivalent joint torques is frequency-dependent during human hopping  

Microsoft Academic Search

Normal human locomotion requires the ability to control a complex, redundant neuromechanical system to repetitively cycle the legs in a stable manner. In a reduced paradigm of locomotion, hopping, we investigated the ability of human subjects to exploit motor redundancy in the legs to coordinate joint torques fluctuations to minimize force fluctuations generated against the ground. Although we saw invariant

Jasper T. Yen; Young-Hui Chang



Photoelastic Coating Study of CT-114 Coupon Joint Test Specimen for Horizontal Stabilizer Rear Attachment Fitting to Vertical Stabilizer Rear Spar.  

National Technical Information Service (NTIS)

As part of a program of life extension of Canadian Forces CT-114 Tutor jet trainer aircraft, an experimental investigation was initiated on the durability and damage tolerance of the horizontal stabilizer rear attachment fitting and its attached component...

J. P. Komorowski



Retrospective study to compare the sliding screw-plate and the Medoff-Maes plate in the treatment of unstable intertrochanteric fractures of the femur  

Microsoft Academic Search

Objective: Comparative study between the sliding screw-plate and the Medoff plate used in the treatment of unstable intertrochanteric fractures of the femur, in order to evaluate stabilization of the focus of the fracture and the osteosynthesis complications. Method: 60 patients were analyzed who were divided into two groups of 30 individuals. Group I - osteosynthesis with sliding screw-plate, and group



Poly(D,L-lactide) coating is capable of enhancing osseous integration of Schanz screws in the absence of infection.  


Pin loosening is a major complication in external fixation. Biological and mechanical conditions play an important role in the maintenance and enhancement of the implant-bone interface in fracture fixation. It is thought that biodegradable coatings may be capable of preventing pin track infection and pin loosening. The goal of this study was therefore to analyze the influence of a biodegradeable coating on the osseous integration of Schanz' screws during fracture treatment. Standardized osteotomies (3-mm fracture gap) of the right tibiae were performed on 16 sheep and stabilized by an AO mono-lateral external fixator. Additional, mechanically less loaded Schanz' screws were also mounted. All screws were randomly coated with biodegradable poly(D,L-lactide). The sheep were sacrificed after 9 weeks. All screws were removed and rolled on blood agar plates for microbiological analysis. Histological sections of the pin tracks were histochemically and morphometrically analyzed. Clinically, no signs of severe infection were visible. Microbiological analysis revealed 14.8% colonization by Staphylococcus aureus in the coated and 29% in the uncoated screws. Histomorphometry of the bone surrounding the Schanz' screws revealed that significantly more osseous integration had occurred on poly(D,L-lactide)-coated screws in the absence of bacterial colonization. Significantly more bone remodeling and a higher osteoclastic activity was seen near the screw-bone interface in the uncoated screw group. Up to a threefold increase in new bone formation and more severe remodeling was observed around the screw entry compared to the pin exit in all groups. Loaded screws showed significantly more callus formation around the exit sites than their less loaded counterparts. In the present study, poly(D,L-lactide) coating of Schanz' screws was found to enhance osseous integration in the absence of bacterial colonization in sheep by causing less cortical remodeling and less osteoclastic activity in the cortices compared to uncoated screws. Additionally, the coating appeared to reduce the instances of pin track infections. Mechanical loading showed an adverse effect on bone formation and remodeling. It has been shown that both biological and mechanical factors play an important role in the maintenance of osseous integrity of the pin-bone interface. Poly(D,L-lactide) coating of Schanz' screws does not prevent osseous destruction and severe bacterial colonization along the pin tracts, but can improve osseous integration of Schanz' screws in the absence of infection. PMID:15909297

Partale, K; Klein, P; Schell, H; Schmidmaier, G; Wildemann, B; Bail, H; Schiller, R; Bragulla, H; Duda, G N



Predicting cancellous bone failure during screw insertion.  


Internal fixation of fractures often requires the tightening of bone screws to stabilise fragments. Inadequate application of torque can leave the fracture unstable, while over-tightening results in the stripping of the thread and loss of fixation. The optimal amount of screw torque is specific to each application and in practice is difficult to attain due to the wide variability in bone properties including bone density. The aim of the research presented in this paper is to investigate the relationships between motor torque and screw compression during powered screw insertion, and to evaluate whether the torque during insertion can be used to predict the ultimate failure torque of the bone. A custom test rig was designed and built for bone screw experiments. By inserting cancellous bone screws into synthetic, ovine and human bone specimens, it was established that variations related to bone density could be automatically detected through the effects of the bone on the rotational characteristics of the screw. The torque measured during screw insertion was found to be directly related to bone density and can be used, on its own, as a good predictor of ultimate failure torque of the bone. PMID:23466167

Reynolds, Karen J; Cleek, Tammy M; Mohtar, Aaron A; Hearn, Trevor C



Metallurgical examination of gun barrel screws.  

National Technical Information Service (NTIS)

The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a li...

E. L. Bird T. L. Clift



Cost effectiveness of subaxial fusion--lateral mass screws versus transarticular facet screws.  


As health care reform continues to evolve, demonstrating the cost effectiveness of spinal fusion procedures will be of critical value. Posterior subaxial cervical fusion with lateral mass screw and rod instrumentation is a well-established fixation technique. Subaxial transarticular facet fixation is a lesser known fusion technique that has been shown to be biomechanically equivalent to lateral mass screws for short constructs. Although there has not been a widespread adoption of transarticular facet screws, the screws potentially represent a cost-effective alternative to lateral mass rod and screw constructs. In this review, the authors describe an institutional experience with the use of lateral mass screws and provide a theoretical cost comparison with the use of transarticular facet screws. PMID:22746231

Ray, Wilson Z; Ravindra, Vijay M; Jost, Gregory F; Bisson, Erica F; Schmidt, Meic H



Transarticular screw fixation using neuronavigation: Technique  

PubMed Central

Background: Transarticular screw placement needs highly accurate imaging. We assess the efficacy and accuracy of C1-C2 transarticular screw fixation using neuronavigation and also cast a technical note on the procedure. Materials and Methods: This study included a total of nine patients who underwent transarticular screw fixation using the neuronavigation system. A total of 15 screws were placed. All patients underwent postoperative CT scan with 3-Dimensional (3-D) reconstruction to check for the accuracy of implantation. Results: One patient had encroachment of the transverse foramen but there was no vertebral artery injury. There were no clinical complications or adverse sequelae. Conclusion: Neuronavigation is extremely helpful in C1-C2 transarticular screw fixation and gives excellent accuracy.

Dwarakanath, Srinivas; Suri, Ashish; Sharma, Bhavani Shankar



Effect of solder filler thickness on the mechanical stability of fiber-solder-ferrule joint under temperature cyclic loading  

Microsoft Academic Search

The base materials of package and ferrule are often gold-coated Kovar and Invar, they both have relatively low coefficient\\u000a of thermal expansion (CTE). Solder 63Sn37Pb dissolves Au substantially and forms brittle AuSn4, which may cause catastrophic failure in the fiber-solder-ferrule (FSF) joint in the long-term application. It is well known\\u000a that thermal fatigue creep is one of the crucial factors

C. W. Tan; Y. C. Chan; N. H. Yeung



U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Weathering Tests Conducted on Soil Stabilizers.  

National Technical Information Service (NTIS)

The report is in three parts. The first was prepared in the Soviet Union. It comprises the results for field trials begun on August 28, 1979, and laboratory experiments on soil stabilizer specimens in the form of crusts or films formed as a result of trea...

W. R. Morrison Z. D. Fedotova



Biomechanical comparison of a locking plate with intraplate compression screw versus locking plate with plantar interfragmentary screw for Lapidus arthrodesis: a cadaveric study.  


Lapidus arthrodesis (first metatarsal cuneiform arthrodesis) has become an accepted procedure for hallux abducto valgus. Several variations of fixation have been described. Earlier weightbearing postoperatively has been one reported benefit of using locking plates for fixation. Additionally, studies have demonstrated that fixation placed on the plantar or tension side of the arthrodesis increases the biomechanical advantage. We performed a biomechanical cadaveric study of the Lapidus procedure, comparing a previously reported technique using a low profile locking plate with an intraplate compression screw versus the same locking plate with a plantar interfragmentary screw (PIFS) placed on the tension side of the arthrodesis in 10 fresh, paired, cadaver limbs. The mean ultimate load of the plate with a PIFS was 383.2 ± 211.5 N, and the mean ultimate load of the plate with an intraplate compression screw was 205.5 ± 97.2 N. The mean ultimate load of the LPS Lapidus plate with a PIFS was statistically greater (p = .027) than that with the plate intraplate compression screw. Our results indicated that changing the orientation of the compression screw to a PIFS significantly increased the stability of the Lapidus arthrodesis fixation construct. The modified construct with the PIFS might decrease the incidence of nonunion and, ultimately, allow patients to bear weight faster postoperatively. PMID:23621977

Cottom, James M; Rigby, Ryan B


Cervical anterior transpedicular screw fixation (ATPS)—Part II. Accuracy of manual insertion and pull-out strength of ATPS  

Microsoft Academic Search

Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or\\u000a infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these\\u000a cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular\\u000a screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications

Heiko Koller; Frank Acosta; Mark Tauber; Michael Fox; Hudelmaier Martin; Rosmarie Forstner; Peter Augat; Rainer Penzkofer; Christian Pirich; H. Kässmann; Herbert Resch; Wolfgang Hitzl



Alignment of pedicle screws with pilot holes: can tapping improve screw trajectory in thoracic spines?  

PubMed Central

Pedicle screws are placed using pilot holes. The trajectory of pilot holes can be verified by pedicle sounding or radiographs. However, a pilot hole alone does not insure that the screw will follow the pilot hole. No studies have characterized the risk of misalignment of a pedicle screw with respect to its pilot hole trajectory. The objective of this study was to measure the misalignment angles between pedicle screws and pilot holes with or without tapping. Six human cadaveric thoracic spines were used. One hundred and forty pilot holes were created with a straight probe. Steel wires were temporarily inserted and their positions were recorded with CT scans. The left pedicles were tapped with 4.5 mm fluted tap and the right pedicles remained untapped. Pedicle screws (5.5 mm) were inserted into the tapped and untapped pedicles followed by CT scans. The trajectories of pilot holes and screws were calculated using three-dimensional vector analysis. A total of 133 pilot holes (95%) were inside pedicles. For the untapped side, 14 out of 68 (20%) screws did not follow the pilot holes and were outside the pedicles. For the tapped side, 2 out of 65 (3%) did not follow and breached the pedicles. The average misalignment angles between the screw and pilot hole trajectory were 7.7° ± 6.5° and 5.6° ± 3.2° for the untapped side and tapped side, respectively (P < 0.05). Most pedicle screws had lateral screw breach (13 out of 16) whereas most pilot holes had medial pedicle breach (6 out of 7). Tapping of pilot holes (1 mm undertap) helps align pedicle screws and reduces the risk of screw malposition. Although most pedicle screws had lateral breach, the risk of medial pedicle breach of the pilot holes must be recognized.

Erkan, Serkan; Hsu, Brian; Mehbod, Amir A.; Perl, John; Transfeldt, Ensor E.



Segmental intrusion with mini-screw implant anchorage: A radiographic evaluation  

Microsoft Academic Search

Introduction: The orthodontist's ability to intrude and control supraeruption of multiple teeth is fundamental for effective and efficient treatment outcomes. To better understand segmental intrusion with fixed anchorage, we evaluated the effects of various forces on the amount of intrusion, root resorption, and mini-screw implant (MSI) stability. Methods: The sample included 8 mature beagle dogs, 20 to 24 months old.

Roberto Carrillo; Peter H. Buschang; Lynne A. Opperman; Pedro F. Franco; P. Emile



[The role of the tibiofibular syndesmotic and the deltoid ligaments in stabilizing Weber B type ankle joint fractures--an experimental investigation].  


The purpose of the present biomechanical investigation was to check the functional importance of the syndesmosis ligaments and of the deltoid ligament for ankle fracture type B according to the AO-Weber classification. We constructed a special fixation clamp, with 12 fresh and unembalmed lower legs being tested for lateral shift (mm) and ten for tibiotalar rotation. All specimens were exposed in the same neutral position. Transverse loads (F(y)) varied between 0 and 150 N, axial loads (F(z)) between 0, 300, 600 and 1,000 N and rotational loads (F(r)) between 2.4 and 4.9 Nm. All series were repeated according to supination-eversion (SE) injury patterns of the Lauge-Hansen classification. Syndesmotic ligaments and the fibula were incrementally sectioned from anterior to posterior. Type SE I consisted of an isolated incision of the anterior syndesmosis ligament. Type SE II had an additional oblique fracture of the fibula at the height of the tibiofibular syndesmosis. In type SE III injuries, in addition to the fibular fracture, a complete rupture of the syndesmosis ligaments was present, and for type SE IV lesions the deltoid ligaments were incised. The transverse load-displacement curve was s-shaped in all uninjured joints,with the highest gradient between 10 and 20 N with no axial compression. Without axial compression in cases of F(y)=25 N transverse loads, the mean talus translation was 0.51 mm. Following type II injuries, the average talus translation was 0.68 mm (not significant) and rose to an average of 0.95 mm ( P <0.01) in type III injuries. After additional incision of the deltoid ligaments, the ankle joint subluxed permanently when more than 5-10 N transverse loads were applied. Axial loads of 300 N or more resulted in a considerable reduction in talus translations, indicating increased stability and congruency within the joint complex. In this way, the vertical loading of the ankle joints always contributed to joint stability. The average internal tibiotalar rotation reached with a torque of 2.4 Nm was 3.52 degrees and with 4.9 Nm 5.15 degrees when no axial compression was applied. External rotation measured -6.36 degrees and -8.62 degrees, respectively. Following the experimental protocol, significant increases were noted for external rotation at SE II degrees injuries ( P =0.003) and for internal rotation at SE III degrees ( P =0.03) injuries. Our data support the proposition that the deltoid ligaments and the posterior syndesmosis play a key role in the stability of ankle fractures for supination-eversion injuries. If these structures remain intact, conservative and early functional treatment are recommended in patients with minimal (<2 mm) or no fracture displacement. This concept is confirmed by the literature dealing with clinical mid- and long-term follow-up studies. PMID:12750808

Richter, J; Schulze, W; Clasbrummel, B; Muhr, G



Practical clinical guidelines to prevent screw loosening.  


The use of a screw-retained prosthesis on an osseointegrated implant is a popular treatment modality offering relative case in the removal of the restoration. One of the complications associated with this modality is the loosening of the abutment and coping screws. Loosening of the screws results in patient dissatisfaction, frustration to the dentist and, if left untreated, component fracture. There are several factors which contribute to the loosening of implant components which can be controlled by the restorative dentist and the lab technician. This article addresses the contributory factors and offers solutions which can be easily incorporated in the treatment. PMID:9117862

Hurson, S



Reinforcement of osteosynthesis screws with brushite cement.  


The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Polymethyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being injectable and resorbable. The aim of this study is to assess the reinforcement of osteosynthesis screws with brushite cement. Polyurethane foams, whose density is close to that of cancellous bone, were used as bone model. A hole was tapped in a foam sample, then brushite cement was injected. Trabecular osteosynthesis screws were inserted. After 24 h of aging in water, the stripping force was measured by a pull-out test. Screws (4.0 and 6.5 mm diameter) and two foam densities (0.14 and 0.28 g/cm3) were compared. Cements with varying solid/liquid ratios and xanthan contents were used in order to obtain the best screw reinforcement. During the pull-out test, the stripping force first increases to a maximum, then drops to a steady-state value until complete screw extraction. Both maximum force and plateau value increase drastically in the presence of cement. The highest stripping force is observed for 6.5-mm screws reinforced with cement in low-density foams. In this case, the stripping force is multiplied by 3.3 in the presence of cement. In a second experiment, cements with solid/liquid ratio ranging from 2.0 to 3.5 g/mL were used with 6.5-mm diameter screws. In some compositions, xanthan was added to improve injectability. The best results were obtained with 2.5 g/mL cement containing xanthan and with 3.0 g/mL cements without xanthan. A 0.9-kN maximal stripping force was observed with nonreinforced screws, while 1.9 kN was reached with reinforced screws. These first results are very promising regarding screw reinforcement with brushite cement. However, the polyurethane foam model presents noninterconnected porosity and physiological liquid was not modelized. PMID:10458285

Van Landuyt, P; Peter, B; Beluze, L; Lemaître, J



[Titanium porous-surface screw implant].  


Titanium porous-surfaced screw implant was made by plasma-spray with Ti powder. The pore size was 80-300 microns. Two groups of implants were implanted in the mandibles of 15 dogs. Group A: porous-surfaced screw implant: Group B: smooth surface screw implant. The bone healing was evaluated by L. M. SEM. and shear strength testing. The results show that the osteo integration of two groups were completed after 12 weeks. The bone grew into porous surface. The shear strength of group A was significantly higher than that of group B. PMID:7489655

Zhang, H; Liu, B; Zhnag, X



On the derivation of a tensor to calculate six degree-of-freedom, musculotendon joint stiffness: Implications for stability and impedance analyses.  


Major joints, such as the knee, shoulder, and spine, can buckle along the translational degrees-of-freedom (DoF), causing injury to ligaments and other passive tissues. Despite this, stability and impedance analyses have focused primarily on the rotational DoF. As such, mathematical models quantifying musculotendon translational stiffnesses remain limited and, to our knowledge, there are no published works that explicitly describes the interactions between DoF. Using an energy approach, we derived a six DoF stiffness tensor and provided the necessary equations needed to quantify the musculotendon stiffness of any joint. Using a knee model, we then compared the derived stiffness tensor against two commonly used measures: one that excludes translational DoF and another that excludes interactions between DoF. We found that both of these measures had large over-estimations of stiffness, particularly for the rotational DoF, compared to our derived tensor. These findings indicate that previous analyses may have found rotational DoF to be stable when they were unstable. PMID:24028892

Cashaback, Joshua G A; Potvin, Jim R; Pierrynowski, Michael R



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


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



Reinforcement of osteosynthesis screws with brushite cement  

Microsoft Academic Search

The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Poly-methyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being

P Van Landuyt; B Peter; L Beluze; J LemaÎtre



Biomechanical Evaluation of Graft Fixation Techniques for Acromioclavicular Joint Reconstructions Utilizing Coracoclavicular Tendon Grafts  

Microsoft Academic Search

BackgroundThe purpose of this study was to compare the initial strength of acromioclavicular joint reconstructions using coracoclavicular (CC) tendon grafts utilizing interference screws, a tendon square knot or side-to-side suturing for graft fixation.

Robert Z. Tashjian; Jodi D. Southam; Todd Clevenger; Kent N. Bachus


Biological and biomechanical evaluation of interface reaction at conical screw-type implants  

Microsoft Academic Search

BACKGROUND: Initial stability of the implant is, in effect, one of the fundamental criteria for obtaining long-term osseointegration. Achieving implant stability depends on the implant-bone relation, the surgical technique and on the microscopic and macroscopic morphology of the implant used. A newly designed parabolic screw-type dental implant system was tested in vivo for early stages of interface reaction at the

Andre Büchter; Ulrich Joos; Hans-Peter Wiesmann; László Seper; Ulrich Meyer



Accuracy analysis of a multi-loop linkage with joint clearances  

Microsoft Academic Search

This paper introduces a generalized method for error analysis of multi-loop mechanisms with joint clearance. Joint clearance is treated as a virtual link to simplify the study. Equivalent kinematical pair is used to model the motion freedoms furnished by the joint clearances. The developed methodology uses the properties of reciprocal screws to determine the instantaneous configurations. Six-bar linkages with different

Ming-June Tsai; Tien-Hsing Lai



Oil extraction of oleic sunflower seeds by twin screw extruder: influence of screw configuration and operating conditions  

Microsoft Academic Search

The objective of this study was to investigate the effects of screw configuration, position of screw elements and spacing between them allowing to realize oil extraction of oleic sunflower seeds on a twin-screw extruder. Experiments were conducted using a co-rotating twin-screw extruder (Model Clextral BC 45, France). Twelve screw profiles were examined to define the best performance (oil extraction yield,

I. Amalia Kartika; P. Y. Pontalier; L. Rigal



Vascular injury involving proximal medial-to-lateral oblique locking screw insertion in tibial intramedullary nailing.  


Orthopaedic surgeons have reported increased neurologic complications with the employment of next-generation tibial nail fixation with variable proximal and distal locking options. However, vascular injury due to oblique screw placement has not been documented. We describe a case in which a medial-to-lateral oblique locking screw led to significant vascular injury. The judicious use of these screws and their relative contribution to fracture stability should be carefully considered for individual cases. Additionally, drill penetration through the far tibial cortex may not be obvious and utilizing oscillation or reverse drilling techniques may be of benefit. Lastly, the forward thrust of the popliteal artery with the use of a positioning bump in the popliteal fossa may place the vascular structure at increased risk of injury. Employing means to avoid these injuries and minimize risks in pertinent patients is of utmost importance. PMID:21846016

Hussain, Waqas; Balach, Tessa; Leland, J Martin



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.



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

PubMed Central

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




Orthogonal biplanar fluoroscopy-guided percutaneous fixation of a coracoid base fracture associated with acromioclavicular joint dislocation.  


Coracoid process fractures that involve the coracoid base (inferior pillar) without a concomitant rupture of the coracoclavicular ligaments can destabilize the acromioclavicular joint with its subsequent dislocation; prophylactic or therapeutic operative treatment involving open reduction and internal fixation has been traditionally recommended. This report presents a new technique of percutaneous reduction and stabilization of the coracoid fracture with indirect acromioclavicular joint reduction under fluoroscopic guidance; biplanar visualization of coracoid process anatomy is obtained using 2 specific radiographic/fluoroscopic-beam angulations (Bhatia views), and this permits a guided placement of screws for controlled reduction of this dual injury. The technique is based on the author's original work on coracoid process anatomy and development of radiographic views for orthogonal visualization of coracoid pillars in their entirety. Technical tips to facilitate percutaneous fracture fixation and to avoid potential complications are discussed. PMID:22411122

Bhatia, Deepak N



Role of rod diameter in comparison between only screws versus hooks and screws in posterior instrumentation of thoracic curve in idiopathic scoliosis  

Microsoft Academic Search

Since the introduction of Cotrel–Dubousset instrumentation in 1984, the correction techniques in scoliosis surgery have changed\\u000a from Harrington principles of concave distraction to segmental realignment to a variety of possibilities including the rod\\u000a rotation manoeuvres, and to segmental approximation via cantilever methods. Additionally, pedicle screw utilization in lumbar\\u000a curves enhanced correction and stabilization of various deformities, and various studies have

Claudio Lamartina; Maria Petruzzi; Marcello Macchia; Paola Stradiotti; Alberto Zerbi



The influence of ankle joint mobility when using an orthosis on stability in patients with spinal cord injury: a pilot study.  


Objectives:Perceived risk of falling is an important factor for people with spinal cord injury (SCI). This study investigated the influence of ankle joint motion on postural stability and walking in people with SCI when using an orthosis.Methods:Volunteer subjects with SCI (n=5) participated in this study. Each subject was fitted with an advanced reciprocating gait orthosis (ARGO) equipped with either solid or dorsiflexion-assist type ankle-foot orthosis (AFOs) and walked at their self-selected speed along a flat walkway to enable the comparison of walking speed, cadence and endurance. A force plate system and a modified Falls Efficacy Scale (MFES) were utilized to measure postural sway and the perceived fear of falling, respectively.Results:There were significant differences in the mean MFES scores between two types of orthosis (P=0.023). When using two crutches, there was no significant difference in static standing postural sway in the medio-lateral (M/L) direction (P=0.799), but significant difference in the antero-posterior (A/P) direction (P=0.014). However, during single crutch support, there was a significant difference in both M/L (P=0.019) and A/P (P=0.022) directions. Walking speed (7%) and endurance (5%) significantly increased when using the ARGO with dorsi flexion assisted AFOs. There was no significant deference between two types of orthoses in cadence (P=0.54).Conclusions:Using an ARGO with dorsiflexion-assisted AFOs increased the fear of falling, but improved static postural stability and increased walking speed and endurance, and should therefore be considered as an effective orthosis during the rehabilitation of people with SCI. PMID:23896671

Arazpour, M; Bani, M A; Hutchins, S W; Curran, S; Javanshir, M A



Multifragmentary Tibial Pilon Fractures: Midterm Results After Osteosynthesis with External Fixation and Multiple Lag Screws  

PubMed Central

Osteosynthesis of intraarticular tibial pilon fractures is preferably achieved using locking plates via a minimally invasive technique. If combined with severe soft tissue damage there is a high risk of wound-healing deficits after plate osteosynthesis. Thus our aim was to find an alternative method of treatment for those cases with combined soft tissue injuries. We report on five cases with comminuted fractures of the joint surface combined with critical soft tissue condition that were treated with lag screws and external fixation (AO) applied across the ankle joint. All five patients were followed up, undergoing clinical and radiological examination. Using this approach we achieved fracture healing of comminuted fractures without further complications. Clinical follow-up after an average of 55.6 (36–75) months revealed a mean AOFAS score of 81 (62–100). We therefore propose combined treatment using lag screws with external fixation as a practical treatment option for those fractures for which lag screws combined with a locking plate are not feasible or when there is a high risk of wound-healing deficits due to severe soft tissue damage.

Kiene, Johannes; Herzog, Jan; Jurgens, Christian; Paech, Andreas



Optimal alignment of the distal screws in the tibial nailing  

Microsoft Academic Search

Serious stress concentration around the regions near the distal nail?holes and the distal screws in conventional tibial interlocking nails has been reported in previous studies. A three?dimensional finite element model was used to study the interlocking nail, the fractured tibia and the locking screws. The distal screws were inserted into the tibial nail in different configurations. We found that the



Visuality in The Turn of the Screw: \\  

Microsoft Academic Search

Scarry is referring to the half-formed, transitory, vanishing quality of ghosts—a quality shared, more or less, by any mental image we might choose to form in the mind's eye. In this sense The Turn of the Screw is a perfect ghost story. It is a story about seeing ghosts, about picturing them, and perhaps about imagining them altogether. In fact,

Josh Rothman


Helical Screw Expander Evaluation Project. Final Report.  

National Technical Information Service (NTIS)

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 conditi...

R. McKay



A phenomenological study on twin screw extruders  

Microsoft Academic Search

Although more and more twin screw extruders are being used in the polymer industry, the theoretical background is relatively undeveloped. The literature abounds in contradictions and often informs the reader that all extrusion problems can be solved if a certain new design is considered. The development of successful machines has mainly been possible through the application of commercially valuable empirical

L. P. B. M. Janssen



Lapidus bunionectomy: Early evaluation of crossed lag screws versus locking plate with plantar lag screw.  


We compared outcomes of the Lapidus bunionectomy fixated with crossed lag screws versus a locking plate with a plantar lag screw. Forty patients who underwent Lapidus bunionectomy between August 2001 and May 2006 were evaluated in a combined retrospective and prospective fashion. Crossed lag screws were used in 19 of the patients, and a locking plate with a plantar lag screw was used in 21 of the patients. Other than fixation, the only interventional difference pertained to postoperative weight bearing, where those receiving the plate initiated full weight bearing on the operated foot at 4 weeks postoperative, as compared to 6 weeks for those receiving crossed screws. Overall, the mean preoperative AOFAS hallux score was 41.75 +/- 2.52, and the postoperative score was 90.48 +/- 8.41 (P < .0001). The overall mean preoperative first intermetatarsal angle was 15.3 degrees +/- 2.32 degrees , and long term the angle was 5.03 degrees +/- 2.86 degrees (P < .0001). When comparisons were made based on the method of fixation, use of an adjunct Akin osteotomy and surgery performed before 2003 were statistically significantly associated with crossed screw fixation, and the preoperative AOFAS score was statistically significantly higher in the locking plate fixation group. There were no statistically significant differences related to postoperative complications between the 2 fixation groups. In conclusion, the Lapidus bunionectomy fixated with a locking plate and a plantar lag screw allows earlier weight bearing in comparison with crossed lag screws, without a difference in complications. Level of Clinical Evidence: 2. PMID:19232969

Saxena, Amol; Nguyen, Aidan; Nelsen, Elise


Hybrid technique for posterior lumbar interbody fusion: a combination of open decompression and percutaneous pedicle screw fixation.  


The authors describe a hybrid technique that involves a combination of open decompression and posterior lumbar interbody fusion (PLIF) and percutaneously inserted pedicle screws. This technique allows performance of PLIF and decompression via a midline incision and approach without compromising operative time and visualization. Furthermore, compared to standard open decompression, this approach reduces post-operative wound pain because the small midline incision significantly reduces muscle trauma by obviating the need to dissect the paraspinal muscles off the facet joint complex and by avoiding posterolateral fusion, thus requiring limited lateral muscle dissection off the transverse processes. A series of patients with Grade I-II spondylolisthesis at L4-5 and moderate-severe canal/foraminal stenosis underwent midline PLIF at L4-5, with closure of the midline incision. Percutaneous pedicle screws were inserted, thereby minimizing local muscle trauma, reduction of the spondylolisthesis being performed by using a pedicle screw construct. Rods were inserted percutaneously to link the L4 and L5 pedicle screws. Image intensification was used to confirmed satisfactory screw placement and reduction of spondylolisthesis. The results of a prospective study comparing a standard open decompression and fusion technique for spondylolisthesis versus the minimally invasive hybrid technique are discussed. The minimally invasive technique resulted in shorter hospital stay, earlier mobilization and reduced postoperative narcotic usage. The long-term clinical outcomes were equivalent in the two groups. PMID:23658050

Mobbs, Ralph J; Sivabalan, Praveenan; Li, Jane; Wilson, Peter; Rao, Prashanth J



Pedicle screw placement with O-arm and stealth navigation.  


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



Technical factors related to the incidence of adjacent superior segment facet joint violation after transpedicular instrumentation in the lumbar spine  

Microsoft Academic Search

Segmental pedicle screw fixation is rapidly becoming a popular method of spinal instrumentation. Few studies have investigated\\u000a the rates of adjacent superior segment facet joint violation. The purpose of our study were to investigate the incidence of\\u000a superior segment facet joint violation after pedicle screw instrumentation in the lumbar spine and to evaluate technical factors\\u000a related to the incidence. A

Zhiming Chen; Jie Zhao; Hao Xu; Aigang Liu; Jiandong Yuan; Cong Wang



Comparison between the accuracy of percutaneous and open pedicle screw fixations in lumbosacral fusion.  


BACKGROUND CONTEXT: In pedicle screw fixation, accurate insertion is essential to avoid neurological injury or weak stability. The percutaneous pedicle screw system was developed for minimally invasive spine surgery, and its safety has already been reported. However, the accuracy of percutaneous pedicle screw fixation (PPF) has not been compared with that of the open system to date. PURPOSE: To compare the accuracy of PPF with that of open pedicle screw fixation (open PF) and to investigate the risk factors associated with pedicle wall penetration. STUDY DESIGN/SETTING: A retrospective case series. PATIENT SAMPLE: The study group included 237 patients who underwent posterior pedicle screw fixation between January 2008 and October 2010 at a single institute with a total of 1,056 pedicle screw fixations completed. One hundred and twenty-six patients with 558 screws underwent open PF and 111 patients with 498 screws underwent PPF. OUTCOME MEASURES: Postoperative computerized tomography, including sagittal and coronal reformatted images. METHODS: Consecutive surgeries with either conventional open PF or PPF for anterior lumbar interbody fusion or transforaminal lumbar interbody fusion were performed. The open pedicle screw employed was from the WSH system (Winova, Seoul, Korea), and the two percutaneous pedicle screw systems were the Sextant (Medtronics, Minneapolis, MN, USA) and the Viper systems (DePuy Spine, Raynham, MA, USA). Computed tomography images were evaluated to determine pedicle wall penetration after operation. Severity was classified as mild (<3 mm), moderate (3-6 mm), and severe (?6 mm), and the direction was assessed as medial, lateral, inferior, and superior. RESULTS: Pedicle wall penetration occurred in 75 patients (13.4%) in the open PF group and 71 patients (14.3%) in the PPF group and was not statistically different between the groups (p=.695). Assessment of the severity of the pedicle wall penetration revealed that minor penetration was the most common (open PF group, 9.7%; PPF group, 10.6%), although the distribution of the degree of severity was not statistically different between the groups (p=.863). A relatively higher incidence of lateral penetration was observed in the open PF group (66.7% vs. 43.7%), whereas medial, superior, and inferior penetrations were higher in the PPF group (p=.033). Other parameters such as age, sex, surgical method, and surgeon factors did not influence the penetration rate, but bone mineral densitometry negatively correlated with the penetration. CONCLUSIONS: Pedicle wall penetration during screw fixation was not different between the open PF and PPF groups. The lateral, paraspinal, muscle-splitting approach seems to lessen medial wall penetration, especially in the S1 vertebra. Distribution of the direction of penetration differs between the groups, with lateral wall penetration being more prominent in the open PF group. Careful placement of pedicle screws is necessary for a stronger construct because of the high incidence of penetration. PMID:23647827

Oh, Hyeong Seok; Kim, Jin-Sung; Lee, Sang-Ho; Liu, Wei Chiang; Hong, Soon-Woo



Cervical pedicle screw placement: feasibility and accuracy of two new insertion techniques based on morphometric data  

Microsoft Academic Search

This morphometric and experimental study was designed to assess the dimensions and axes of the subaxial cervical pedicles\\u000a and to compare the accuracy of two different techniques for subaxial cervical pedicle screw (CPS) placement using newly designed\\u000a aiming devices. Transpedicular fixation is increasingly used for stabilizing the subaxial cervical spine. Development of the\\u000a demanding technique is based on morphometric studies

M. Reinhold; F. Magerl; M. Rieger; M. Blauth



The role of supplemental translaminar screws in anterior lumbar interbody fixation: a biomechanical study  

Microsoft Academic Search

The immediate stabilization provided by anterior interbody cage fixation is often questioned. Therefore, the role of supplementary\\u000a posterior fixation, particularly minimally invasive techniques such as translaminar screws, is relevant. The purpose of this\\u000a biomechanical study was to determine the immediate three-dimensional flexibility of the lumbar spine, using six human cadaveric\\u000a functional spinal units, in four different conditions: (1) intact, (2)

G. C. Rathonyi; T. R. Oxland; U. Gerich; S. Grassmann; L.-P. Nolte



Load sharing properties of cervical pedicle screw-rod constructs versus lateral mass screw-rod constructs.  


Lateral mass screws have a history of successful clinical use, but cannot always be used in the subaxial cervical spine. Despite safety concerns, cervical pedicle screws have been proposed as an alternative. Pedicle screws have been shown to be biomechanically stronger than lateral mass screws. No study, however, has investigated the load sharing properties comparing constructs using these screws. To investigate this, 12 fresh-frozen single cervical spine motion segments (C4-5 and C6-7) from six cadavers were isolated. They were randomized to receive either lateral mass or pedicle screw-rod constructs. After preloading, the segments were cyclically loaded with a uniplanar axial load from 0 to 90 N both with and without the construct in place. Pressure data at the disc space were continuously collected using a dynamic pressure sensor. The reduction in disc space pressure between the two constructs was calculated to see if pedicle screw and lateral mass screw-rod constructs differed in their load sharing properties. In both the pedicle screw and lateral mass screw-rod constructs, there was a significant reduction in the disc space pressures from the no-construct to construct conditions. The percentage decrease for the pedicle screw constructs was significantly greater than the percentage decrease for the lateral mass screw constructs for average pressure (p < or = 0.002), peak pressure (p < or = 0.03) and force (p < or = 0.04). We conclude that cervical pedicle screw-rod constructs demonstrated a greater reduction in axial load transfer through the intervertebral disc than lateral mass screw-rod constructs. Though there are dangers associated with the insertion of cervical pedicle screws, their use might be advantageous in some clinical conditions when increased load sharing is necessary. PMID:20119837

Dunlap, Bradley J; Karaikovic, Eldin E; Park, Hyung-Soon; Sokolowski, Mark J; Zhang, Li-Qun



Failure analysis of broken pedicle screws on spinal instrumentation.  


Revised spinal surgery is needed when there is a broken pedicle screw in the patient. This study investigated the pedicle screw breakage by conducting retrieval analyses of broken pedicle screws from 16 patients clinically and by performing stress analyses in the posterolateral fusion computationally using finite element (FE) models. Fracture surface of screws was studied by scanning electron microscope (SEM). The FE model of the posterolateral fusion with the screw showed that screws on the caudal side had larger axial stress than those on the cephalic side, supporting the clinical findings that 75% of the patients had the screw breakage on the caudal side. SEM fractography showed that all broken screws exhibited beach marks or striations on the fractured surface, indicating fatigue failure. Screws of patients with spinal fracture showed fatigue striations and final ductile fracture around the edge. Among the 16 patients who had broken pedicle screws 69% of them achieved bone union in the bone graft, showing that bone union in the bone graft did not warrant the prevention of screw breakage. PMID:15990065

Chen, Chen-Sheng; Chen, Wen-Jer; Cheng, Cheng-Kung; Jao, Shyh-Hua Eric; Chueh, Shan-Chang; Wang, Chang-Chih



Clinical and mechanical evaluation of screw-retained implant-supported zirconia restorations. A 36 months prospective clinical study.  


This study evaluated the clinical performance of screwed customized zirconia abutments. Additionally, the marginal fit between the selected implant components was measured and the clinical gingival response was monitored. Thirty patients were consecutively selected for a prospective study of 30 implant-supported restorations. Customized zirconia abutment complexes were prepared, then ceramic was performed directly. The abutments were screwed onto the implants and restored with all-ceramic crowns. Plaque and gingival indices were recorded monthly intervals over a 12- month period. All ceramic zirconia abutments offered sufficient stability to support implantsupported single-tooth reconstructions in anterior and premolar regions. The soft and hard tissue reaction toward zirconia was favorable. PMID:23756842

Di Alberti, L; Di Alberti, C; Donini, F; Lo Muzio, L; Cadrobbi, F; D'Agostino, A; De Santis, D; Bertossi, D



[Computer-assisted arthrodesis of the sacroiliac joint].  


Arthrodesis of the sacroiliac joint (SI) usually requires a large surgical exposure using the lateral approach. Computer-assisted surgery based on intraoperative 3D fluoroscopy imaging can reduce the approach to stab incisions. The clinical example shows the insertion of two screws and a cylindrical bone graft to achieve an arthrodesis of the SI joint. The intraoperatively navigated placement of implants and bone graft was performed only by stab incisions. PMID:15971076

Gebhard, F; Sarkar, M; Maier, G; Kinzl, L; Arand, M



Chronic volar distal radioulnar joint instability: joint capsular plication to restore function  

PubMed Central

Background Volar instability of the distal radioulnar joint (DRUJ) is uncommon, and there is little written about it. The purpose of this study is to describe a new procedure to treat volar DRUJ instability and to present the outcomes of patients who received this unique surgical repair at a minimum of 1 year follow-up. Methods We performed a retrospective case series of 6 consecutive patients treated with a volar and dorsal capsular plication procedure by an upper extremity specialist surgeon at a teaching hospital between April 1999 and October 2004. We evaluated measures, including wrist range of motion, grip strength, radiographs, Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire and Patient-Rated Wrist Evaluation (PRWE), at final follow-up. Results Five of 6 patients had resolution of pain and instability symptoms. The average difference in range of motion between operative and contralateral sides was –7° flexion, 2° extension, 4° radial deviation, 2° ulnar deviation, –17° supination and –2° pronation. Average grip strength measured 83% of the uninjured side. The average DASH score was 13.5 (range 0–46.7), and the average PRWE score was 26.7 (range 0–70). One patient had a low ulnar neuropathy, which resolved. One patient fractured the temporary DRUJ stabilization screw and had radiographic evidence of nonbridging heterotopic ossification. Conclusion Joint capsular plication for DRUJ has not yet been described in the literature. It is less elaborate in that it does not require a tendon graft with bone tunnels. The results at an average 16.5 months postoperatively are promising.

Johnston, Kelly; Durand, D'Arcy; Hildebrand, Kevin A.



Comparison of the retro screw and standard interference screw for ACL reconstruction.  


The objective of the study was to compare the load to failure between a retro screw (RS) and a standard interference screw (IS) for tibial-sided anterior cruciate ligament (ACL) fixation. We used 20 bovine tibia and extensor tendons for the study. A group of 10 specimens underwent IS fixation while the other 10 underwent RS fixation. Within each group, five specimens had graft suture in contact (interdigitating) with the screw threads. All specimens were tested on the MTS 858 Mini Bionix II (MTS Systems, Shakopee, MN). There was no statistically significant difference between the RS and IS with respect to peak load to failure. IS with suture interdigitation failed at an average of 520 N (range: 358 to 793 N), while the RS with suture interdigitation failed at 613 N (range: 438 to 1089 N). The IS without suture interdigitation failed at 654 N and the RS without suture interdigitation at 531 N. Specimens with a whipstitch in contact with the screw did not demonstrate higher pull out strength. The RS fixation strength appears to equal the IS. Graft suture contact with screw threads does not increase fixation strength. Based on this study, using a RS for tibial ACL soft tissue graft fixation is feasible and provides equal fixation strength compared with the standard IS. PMID:23057142

Wang, Robert Y; Arciero, Robert A; Obopilwe, Elifho; Mazzocca, Augustus D



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.

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



Cervical and upper thoracic screwing for spinal fusion: strategy for its safe insertion to avoid major complications  

Microsoft Academic Search

There are several screwing techniques to attain cervical fusion such as pedicle screw, lateral mass screw, facet screw, transarticular\\u000a and laminar screw. Each screwing technique has advantages and disadvantages. In this study, we introduce our strategy for\\u000a safe screwing and its clinical results. Our strategy is as follows: lateral mass screw for C1, 3, 4, 5, 6 and pedicle screw

Koichi Sairyo; Toshinori Sakai; Kosaku Higashino; Tatsuya Tamura; Shinsuke Katoh; Natsuo Yasui



The use of fusion mass screws in revision spinal deformity surgery.  


STUDY DESIGN: To report the use of a posterior based 'fusion mass screw' (FMS) as a primary or salvage fixation point in a revision spinal deformity following a previous posterior spinal fusion (PSF). Our experience of this technique in a case report and the clinical and radiological results are reported. OBJECTIVES: To describe the technique and uses of the FMS as a primary/salvage fixation point in osteotomies in previously arthrodesed spinal deformity surgery. Obtaining fixation points to correct and stabilize a spinal deformity with coronal and sagittal imbalance in a previously arthrodesed spine during revision surgery can be challenging. Several alternate pedicle fixation techniques and laminar screw techniques have been described in the literature. However, there is no description of these techniques in the presence of a spinal fusion with distorted anatomy. A pedicle screw placed coronally across a thick posterior fusion mass can provide an alternate method of fixation in these cases with complex anatomy. METHODS: Two cases of complex spinal deformity and corrective spinal osteotomies using fusion mass screws (FMSs) placed coronally across the posterior fusion mass are described. The first case is an 8-year-old patient with Marfan's syndrome who developed a crank shaft phenomenon and severe thoracolumbar kyphoscoliosis following a previous PSF. The second case is a 53-year-old patient with coronal imbalance following PSF as a child using Harrington instrumentation who developed distal degeneration with stenosis in her remaining mobile segments. Both patients underwent vertebral column resection and osteotomy closure plus stabilisation using FMS. The clinical and radiological results and technique for insertion of the FMS are described. CONCLUSION: In this report, we present a novel method of using posterior FMSs to achieve fixation and correction in cases of revision deformity surgery with difficult anatomy. While we feel pedicle screws are the gold standard in deformity correction, knowledge of alternatives such as the FMS can allow surgeons to achieve stable constructs when faced with challenging situations. PMID:23744035

Lewis, Stephen J; Arun, Ranganathan; Bodrogi, Andrew; Lebel, David E; Magana, Sofia P; Dear, Taylor E; Witiw, Chris



How pilot-hole size affects bone-screw pullout strength in human cadaveric cancellous bone  

PubMed Central

Objective Screw failure of cancellous bone screws is not uncommon. To compare the effect of varying pilot-hole size on pullout strength of cancellous bone screws in human cadaveric bone, we designed and performed a biomechanical study to allow quantitative analysis. Methods Three pairs of distal femurs and 4 pairs of proximal tibias from embalmed human cadavers were stabilized in a mould, and the bone cortex was overdrilled. Four sites in a linear transverse plane were randomly assigned, anatomically matched with the paired bone and drilled with either pilot-hole size 3.2 mm or 2.5 mm. The cancellous screw (Synthes noncannulated 4.5-mm shaft, 6.5-mm external diameter) was guided into the pilot hole and pulled on by a test frame (Instron 8874 biaxial servo-hydraulic test frame) with increasing force to the point of failure, and the forces at which failure resulted were compared. Results A comparison of 25 anatomically paired sites with a 2-tailed paired t test and Wilcoxon matched-pairs signed rank test indicated significantly stronger pullout strength (p = 0.047 and p = 0.047) of the 2.5-mm compared with the 3.2-mm pilot hole. Subanalysis of the 4 studied locations indicated that 3 supported the above findings and 1 supported a reverse trend. Conclusions Generally, cancellous screws demonstrated a significantly (p < 0.05) stronger hold using a smaller size pilot hole than the recommended standard diameter. All locations except the inner lateral site supported this finding.

Steeves, Mark; Stone, Craig; Mogaard, John; Byrne, Stephanie



Research and application of absorbable screw in orthopedics: a clinical review comparing PDLLA screw with metal screw in patients with simple medial malleolus fracture.  


Objective: To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. Methods: A total of 129 patients with simple medial malleolus fracture were studied. Among them, 64 patients were treated with poly-D, L-lactic acid (PDLLA) absorbable screws, while the others were treated with metal screws. All the patients were followed up for 12-20 months (averaged 18.4 months) and the therapeutic effect was evaluated according to the American Orthopaedic Foot and Ankle Society clinical rating systems. Results: In absorbable screw group, we obtained excellent and good results in 62 cases (96.88%); in steel screw group, 61 cases (93.85%) achieved excellent and good results. There was no significant difference between the two groups. Conclusion: In the treatment of malleolus fracture, absorbable screw can achieve the same result compared with metal screw fixation. Absorbable screw is preferred due to its advantages of safety, cleanliness and avoiding the removal procedure associated with metallic implants. PMID:23384867

Tang, Jin; Hu, Jin-Feng; Guo, Wei-Chun; Yu, Ling; Zhao, Sheng-Hao



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.



Comparative endurance testing of the Biomet Matthews Nail and the Dynamic Compression Screw, in simulated condylar and supracondylar femoral fractures  

PubMed Central

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 Biomet Matthews Nail (BMN) were implanted into composite femurs, which were subsequently cyclically loaded using a materials testing machine. Simulated fractures were applied to each femur prior to the application of load. Either a Y type fracture or a transverse osteotomy was prepared on each composite femur using a jig to enable consistent positioning of cuts. Results The Biomet Matthews Nail demonstrated a greater endurance limit load over the dynamic compression screw in both fracture configurations. Conclusion The distal locking screws pass through the Biomet Matthews Nail in a unique "cruciate" orientation. This allows for greater purchase in the bone of the femoral condyle and potentially improves the stability of the fracture fixation. As these fractures are usually in weak osteoporotic bone, the Biomet Matthews Nail represents a favourable surgical option in these patients.

O'Connor-Read, Laurence M; Davidson, Jerome A; Davies, Benjamin M; Matthews, Michael G; Smirthwaite, Paul



[Cement distribution in vertebroplasty pedicle screws with different designs].  


The effects of deteriorated bone density become particularly apparent in cases where spinal instrumentation is needed. Cement augmentation of pedicle screws for better bone purchase became the subject of many studies, which proved the biomechanical superiority and the increased pullout strength of cement augmented screws. Inadequate, and sometimes dangerous, cement distribution made the need for development of special implants inevitable. Pedicle screws with side openings and a central drill hole allow cement augmentation through the implant and increase not only the screw diameter but also the interfacial strength between the three components (screw-cement-bone). Accordingly cement distribution can be affected by the selection of the side openings (size and position). Screws with conical core and distally situated side openings facilitate the development of uniform cement dough. PMID:20549485

Kafchitsas, K; Geiger, F; Rauschmann, M; Schmidt, S



Missing Screw as a Rare Complication of Anterior Cervical Instrumentation  

PubMed Central

Although anterior cervical arthrodesis is an effective procedure for the treatment of cervical disorders, the method has some complications. Here, we describe this rare complication of cervical instrumentation with a literature review. A 23-year-old male patient was operated for a C6-C7 dislocation. At postoperative month 10, he presented with hemoptysis and dysphagia. Cervical roentgenograms showed anterior migrations of one broken screw and a plate-locking screw at the C6 corpus. One screw was missing. We concluded that the missing screw had perforated the esophagus and had been eliminated spontaneously through the gastrointestinal tract. No screw should migrate. Even loose screws should be noted in follow-up X-ray studies. If such findings are detected, a second operation for revision should be considered as soon as possible to prevent potentially fatal complications.

Duransoy, Yusuf Kurtulus; Mete, Mesut; Zengel, Baha; Selcuk?, Mehmet



Screw-matrix method in dynamics of multibody systems  

Microsoft Academic Search

In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical\\u000a equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings\\u000a of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson\\/Wittenberg formalism.

Liu Yanzhu



Distal interphalangeal joint arthrodesis: an analysis of complications.  


One hundred thirty-nine patients underwent 181 arthrodeses of finger distal interphalangeal joints (144) and/or thumb interphalangeal joints (37). Techniques included (1) crossed Kirschner pins (111 joints), (2) interfragmentary wire and longitudinal Kirschner pin (43 joints), and (3) Herbert screw (27 joints). Each technique had a similar nonunion rate. There were 21 nonunions: 13 were pain free, 6 were successfully fused on the second attempt, 1 was painful (but the patient refused further surgery), and 1 was amputated. Inadequate bone stock, inadequate bone resection, premature pin removal, and infection appear to complicate the attainment of bony union. Twenty percent of the fusions had major complications (nonunion, malunion, deep infection, and osteomyelitis). Minor complications (dorsal skin necrosis, cold intolerance, proximal interphalangeal joint stiffness, paresthesias, superficial wound infection, and prominent hardware) occurred in 16% of the joints fused. PMID:1430956

Stern, P J; Fulton, D B





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

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



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


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

Szivek, J A; Yapp, R A



Evaluation of screw loosening on new abutment screws and after successive tightening.  


This study evaluated the loss of the torque applied after use of new screws and after successive tightening. Four infrastructures (IE), using UCLA castable abutment type, were cast in cobalt-chromium alloy and new abutment screws (G1) were used in a first moment. Subsequently, the same abutment screws were used a second time (G2) and more than two times (G3). The values of the torques applied and detorques were measured with a digital torque wrench to obtain the values of initial tightening loss (%). Data were analyzed by ANOVA and Tukey's test (?=0.05). Significant differences were observed between the G1 (50.71% ± 11.36) and G2 (24.01% ± 3.33) (p=0.000) and between G1 (50.71% ± 11.36) and G3 (25.60% ± 4.64) (p=0.000). There was no significant difference between G2 and G3 (p=0.774). Within the limitations of the study, it may be concluded that the percentage of the initial torque loss is lower when screws that already suffered the application of an initial torque were used, remaining stable after application of successive torques. PMID:21519649

Barbosa, Gustavo Seabra; Silva-Neto, João Paulo da; Simamoto-Júnior, Paulo Cezar; Neves, Flávio Domingues das; Mattos, Maria da Gloria Chiarello de; Ribeiro, Ricardo Faria



Modeling bicortical screws under a cantilever bending load.  


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

James, Thomas P; Andrade, Brendan A



Percutaneous pedicle screw for unstable spine fractures in polytraumatized patients: A report of two cases  

PubMed Central

Unstable spine fractures commonly occur in the setting of a polytraumatized patient. The aim of management is to balance the need for early operative stabilization and prevent additional trauma due to the surgery. Recent published literature has demonstrated the benefits of early stabilization of an unstable spine fracture particularly in patients with higher injury severity score (ISS). We report two cases of polytrauma with unstable spine fractures stabilized with a minimally invasive percutaneous pedicle screw instrumentation system as a form of damage control surgery. The patients had good recovery from the polytrauma injuries. These two cases illustrate the role of minimally invasive stabilization, its limitations and technical pitfalls in the management of unstable spine fractures in the polytrauma setting as a form of damage control surgery.

Tan, Boon Beng; Chan, Chris Yin Wei; Saw, Lim Beng; Kwan, Mun Keong



Time derivatives of screws with applications to dynamics and stiffness  

Microsoft Academic Search

Screw quantities provide geometric insight into three-dimensional mechanics modeled by rigid bodies and lumped parameters. Four distinct cases of time differentiation are examined by combining fixed and moving body derivatives (fundamental to rigid body mechanics) with material and local derivatives (fundamental to continuum mechanics). Three combinations always yield another screw quantity while the most common, the material derivative with respect

Harvey Lipkin



Pedicle screw insertion: computed tomography versus fluoroscopic image guidance  

PubMed Central

Computed tomography image-guided surgery (CTGS) clearly improves the accuracy of pedicle screw insertion. Recent reports claim that a fluoroscopy-guided system (FGS) offered high accuracy and easy application. However, the superiority of either technique remains unclear in clinical application. This study compares the accuracy of pedicle screws installed using CTGS with that of screws installed using FGS. Seventy-four screws inserted using FGS in 13 patients and 76 screws inserted using CTGS in 11 patients were compared. The study population included ten cases of vertebral fracture, five cases of degenerative spondylolisthesis, three cases of spondylolytic spondylolisthesis, two cases of tuberculous spondylitis, two cases of failed earlier back surgery and two case of ankylosing spondylitis with pseudarthrosis. The installed vertebral levels ranged from T8 to S1. Screw positions were assessed with postoperative radiographs and computed tomography. Sixty-nine (93.2%) screws were correctly placed in the FGS group, and seventy-three (96.1%) screws were correctly placed in the CTGS group (P?=?0.491). The results indicated that both image-guided systems offer high accuracy. However, the fluoroscope image-guided system could be considered the primary tool for lower thoracic and lumbosacral pedicle placement because it enables real-time navigation and does not require a preoperative CT scan.

Fu, Tsai-Sheng; Wong, Chak-Bor; Tsai, Tsung-Ting; Liang, Yen-Chiu; Chen, Lih-Huei



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


Accuracy of Pedicle Screw Placement in Thoracic Spine Fractures  

Microsoft Academic Search

Background and Purpose: Transpedicular instrumentation in the thoracic spine is technically difficult because of small pedicle diameters. There are not many studies assessing in vivo accuracy, complications, and the revision rate of transpedicular screws in the thoracic spine. In this retrospective study 278 thoracic pedicle screws of 43 patients were assessed using a scoring system and postoperative computed tomography (CT)

Marty Zdichavsky; Michael Blauth; Christian Knop; Joachim Lotz; Christian Krettek; Leonard Bastian



T1 intralaminar screws: an anatomic, morphologic study.  


In some scenarios, such as complex revisions or tumor cases, intralaminar screw placement in the upper thoracic spine can be used to supplement or replace traditional pedicle screw placement. Despite the theortic feasibility of placing these screws, no thorough anatomic study has evaluated the morphology of the T1 lamina for screw placement.Anatomic data of the T1 lamina, including height, width (the upper, middle, and lower one-third segments), and length (with and without penetration of the facet articulation) were analyzed for 112 T1 vertebrae. The placement of screws with widths of 3.5 or 4 mm and screws with lengths of 24 or 26 mm in the T1 lamina was feasible in all of the laminas measured with the exception of 2 outliers. Furthermore, relationships were found between T1 lamina size and patient height and between T1 lamina size and sex, but no relationship was found between T1 lamina size and race.The morphology of the T1 lamina allows for the simple and safe placement of common screw diameters and is a viable salvage or alternative to the traditional pedicle screw. PMID:23590788

Weaver, John; Seipel, Shane; Eubanks, Jason



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.



Intraosseous screw fixation of anterior cervical graft construct after diskectomy.  


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



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, ...


Screw Withdrawal Resistance of Types A and AB Sheet Metal Screws in Particleboard and Medium-Density Hardboard.  

National Technical Information Service (NTIS)

The common type A sheet metal screw has been replaced by type AB. To compare the face and edge withdrawal resistance of types A and AB screws, the Forest Products Laboratory evaluated their performance in eight particleboards and three medium-density hard...

M. J. Superfesky



Ceramic joints  


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)



Evaluation of compression generated by self compressing Orthofix bone pins and lag screws in simulated lateral humeral condylar fractures.  


A simulated lateral humeral condylar fracture was created in each of the 52 humeri collected from 26 dogs. One humerus from each pair was stabilized with a 2.0 mm cortical bone screw which was inserted in lag fashion. The other humerus from each pair was stabilized with a 2.2 mm threaded diameter Orthofix pin inserted across the condyle. Prior to each repair, an antirotational K-wire was placed and then the Pressurex Sensitive film was inserted in the osteotomy site in order to determine the compressive pressure (MPa), compressive force (KN), and area of compression (cm(2)) achieved during fixation. The maximum insertional torque achieved before stripping was measured for each implant. The mean compression generated by insertion of a 2.0 mm lag screw was 20.36 +/- 1.51 MPa compared to 18.88 +/- 1.76 MPa generated by a 2.2 mm Orthofix pin (p < 0.003). The mean area of compression generated by insertion of a 2.0 mm lag screw was 2.39 +/- 1.29 cm(2), compared to 1.16 +/- 0.84 cm(2) generated by insertion of a 2.2 mm Orthofix pin (p < 0.0001). The mean compressive force (compression x area compressed) generated by insertion of a 2.0 mm lag screw was 4.96 +/- 2.90 Kn, compared to 2.20 +/- 1.65 Kn generated by insertion of a 2.2 mm Orthofix pin (p < 0.0001). The mean insertion torque to failure for the lag screws was 0.49 +/- 0.07 NM, compared to 0.91 NM +/- 0.18 NM generated by the Orthofix pins (P < 0.0001). Both repair methods are likely to be acceptable for the repair of similar fractures in small breed dogs. PMID:17846682

Daubs, B M; McLaughlin, R M; Silverman, E; Rizon, J



Fixation of the Lapidus arthrodesis with a plantar interfragmentary screw and medial low profile locking plate.  


The Lapidus arthrodesis can be used to correct pathology within the forefoot or midfoot, and severe hallux valgus deformities as well as hypermobility of the medial column may be amenable to correction with this procedure. Many different skeletal fixation methods have been described for this procedure, and one form that appears to provide enough construct stability to allow patients to bear weight early in the postoperative period is described herein. This construct consists of an interfragmental compression screw oriented from the plantar aspect of the first metatarsal to the superior aspect of the medial cuneiform, with medial locking plate augmentation. PMID:22632842

Cottom, James M



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

SciTech Connect

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

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



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.

Anand, Neel; Baron, Eli M.



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

Microsoft Academic Search

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

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




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



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.



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.

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



Distal radioulnar joint injuries.  


Distal radioulnar joint is a trochoid joint relatively new in evolution. Along with proximal radioulnar joint, forearm bones and interosseous membrane, it allows pronosupination and load transmission across the wrist. Injuries around distal radioulnar joint are not uncommon, and are usually associated with distal radius fractures,fractures of the ulnar styloid and with the eponymous Galeazzi or Essex_Lopresti fractures. The injury can be purely involving the soft tissue especially the triangular fibrocartilage or the radioulnar ligaments. The patients usually present with ulnar sided wrist pain, features of instability, or restriction of rotation. Difficulty in carrying loads in the hand is a major constraint for these patients. Thorough clinical examination to localize point of tenderness and appropriate provocative tests help in diagnosis. Radiology and MRI are extremely useful, while arthroscopy is the gold standard for evaluation. The treatment protocols are continuously evolving and range from conservative, arthroscopic to open surgical methods. Isolated dislocation are uncommon. Basal fractures of the ulnar styloid tend to make the joint unstable and may require operative intervention. Chronic instability requires reconstruction of the stabilizing ligaments to avoid onset of arthritis. Prosthetic replacement in arthritis is gaining acceptance in the management of arthritis. PMID:23162140

Thomas, Binu P; Sreekanth, Raveendran



Distal radioulnar joint injuries  

PubMed Central

Distal radioulnar joint is a trochoid joint relatively new in evolution. Along with proximal radioulnar joint, forearm bones and interosseous membrane, it allows pronosupination and load transmission across the wrist. Injuries around distal radioulnar joint are not uncommon, and are usually associated with distal radius fractures,fractures of the ulnar styloid and with the eponymous Galeazzi or Essex_Lopresti fractures. The injury can be purely involving the soft tissue especially the triangular fibrocartilage or the radioulnar ligaments. The patients usually present with ulnar sided wrist pain, features of instability, or restriction of rotation. Difficulty in carrying loads in the hand is a major constraint for these patients. Thorough clinical examination to localize point of tenderness and appropriate provocative tests help in diagnosis. Radiology and MRI are extremely useful, while arthroscopy is the gold standard for evaluation. The treatment protocols are continuously evolving and range from conservative, arthroscopic to open surgical methods. Isolated dislocation are uncommon. Basal fractures of the ulnar styloid tend to make the joint unstable and may require operative intervention. Chronic instability requires reconstruction of the stabilizing ligaments to avoid onset of arthritis. Prosthetic replacement in arthritis is gaining acceptance in the management of arthritis.

Thomas, Binu P; Sreekanth, Raveendran



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



Case Report: A Technique to Remove a Jammed Locking Screw from a Locking Plate  

PubMed Central

Background Locking titanium plates revolutionized the treatment of osteoporotic and metaphyseal fractures of long bones. However as with any innovation, with time new complications are identified. One of the problems with titanium locking plates is removal of screws, often attributable to cold welding of screw heads into the locking screw holes. Several techniques have been described to overcome this problem. We describe a new easy technique to remove a jammed locking screw in a locking plate that is easily reproducible and suggest an algorithm to determine the method to remove screws from locking plates. Case Description A 57-year-old man underwent removal of a locking titanium plate from the distal femur. Because the screws could not be readily removed, we used a new technique to remove the jammed locking screws. A radial cut was made in the plate into the locking screw hole and wedged with an osteotome. This released the screw head from the locking screw hole. The screw holes were connected with radial cuts and jammed locking screws were removed in a similar fashion. Literature Review Instruments used for removal of locking screws, including conical extraction screws, hollow reamers, extraction bolts, modular devices, and carbide drill bits, have been described. However, these do not always work. Purposes and Clinical Relevance Removing screws from locking titanium plates can be difficult. There is no method of implant removal that can be universally applied. Therefore, this new technique and our algorithm may be used when removing screws from locking titanium plates.

Dunlop, Colin



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



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.



Joint Replacement (Finger and Wrist Joints)  


... mean to have a “joint replacement” or an “artificial joint”? The abnormal bone and lining structures of ... When should joint replacement surgery NOT be done? Artificial joints should not be done when: There is ...


Optically driven Archimedes micro-screws for micropump applications: multiple blade design  

NASA Astrophysics Data System (ADS)

We study the rotation of photo-driven Archimedes screw with multiple blades. The micron-sized Archimedes screws are readily made by the two-photon polymerization technique. Free-floating screws that are trapped by optical tweezers align in the laser irradiation direction, and rotate spontaneously. In this study we demonstrate that the rotation speeds of two-blade-screws is twice the rotation speed of one-blade-screw. However, more complex 3-blade-screws rotate slower than 2-blade-screws due to their limited geometry resolution at this micron scale.

Baldeck, Patrice L.; Lin, Chih-Lang; Lin, Yu-Sheng; Lin, Chin-Te; Chung, Tien-Tung; Bouriau, Michel; Vitrant, Guy



Mini-Open or Percutaneous Bilateral Lumbar Transfacet Pedicle Screw Fixation: A Technical Note.  


STUDY DESIGN:: Case report. OBJECTIVE:: To describe the technique used to place bilateral lumbar transfacet pedicle screws. SUMMARY OF BACKGROUND DATA:: Transfacet pedicle screw fixation is a growing alternative and biomechanically comparable with traditional pedicle screw fixation. There is no clear description of technique steps for placing transfacet pedicle screws available in the literature, despite recognizing that screw placement is not intuitive even with fluoroscopy, and is dissimilar to placing traditional pedicle screws or translaminar facet screws. METHODS:: We present two illustrative cases where bilateral transfacet pedicle screws were placed for posterior instrumentation following a step by step technique which can be used in a mini-open or percutaenous procedure. RESULTS:: Postoperatively, both patients had adequately placed transfacet pedicle screws bilaterally on x-ray imaging with one patient demonstrating fusion and intact fixation at 11 months follow up. CONCLUSIONS:: Transfacet pedicle screws were successfully placed in two patients in a stepwise technique described to achieve lumbar fusion. PMID:23222099

Chin, Kingsley Richard; Seale, Jason; Cumming, Vanessa



The effect of screw insertion angle and thread type on the pullout strength of bone screws in normal and osteoporotic cancellous bone models.  


Screw fixation can be extremely difficult to achieve in osteoporotic (OP) bone because of its low strength. This study determined how pullout strength is affected by placing different bone screws at varying angles in normal and OP bone models. Pullout tests of screws placed axially, and at angles to the pullout axis (ranging from 10° to 40°), were performed in 0.09 g cm(-3), 0.16 g cm(-3) and 0.32 g cm(-3) polyurethane (PU) foam. Two different titanium alloy bone screws were used to test for any effect of thread type (i.e. cancellous or cortical) on the screw pullout strength. The cancellous screw required a significantly higher pullout force than the cortical screw (p<0.05). For both screws, pullout strength significantly increased with increasing PU foam density (p<0.05). For screws placed axially, and sometimes at 10°, the observed mechanism of failure was stripping of the internal screw threads generated within the PU foam by screw insertion. For screws inserted at 10°, 20°, 30° and 40°, the resistance to pullout force was observed to be by compression of the PU foam material above the angled screw; clinically, this suggests that compressed OP bone is stronger than unloaded OP bone. PMID:20558097

Patel, Purvi S D; Shepherd, Duncan E T; Hukins, David W L



21 CFR 888.3070 - Pedicle screw spinal system.  

Code of Federal Regulations, 2013 CFR

...SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3070 Pedicle screw spinal system. ...22Cr-13Ni-5Mn stainless steel, Ti-6Al-4V, and unalloyed titanium, that allow the surgeon to build an implant...



Application of Screw Calculus to the Evaluation of Manipulator Workspace.  

National Technical Information Service (NTIS)

In this paper, an analytical technique is presented that is based on screw calculus and dual-number matrices to derive the kinematic equations and the workspace formulations of manipulators. A computational procedure for the quantitative evaluation of wor...

L. M. Hsia T. W. Lee



Lateral Mass Screw Fixation in the Cervical Spine  

Center for Biologics Evaluation and Research (CBER)

Text Version... posterior cervical spine may paradoxically result in ... these devices by undertrained spinal surgeons ... Nerve root injury attributed to screw placement ... More results from


Screw thread parameter measurement system based on image processing method  

NASA Astrophysics Data System (ADS)

In the industrial production, as an important transmission part, the screw thread is applied extensively in many automation equipments. The traditional measurement methods of screw thread parameter, including integrated test methods of multiparameters and the single parameter measurement method, belong to contact measurement method. In practical the contact measurement exists some disadvantages, such as relatively high time cost, introducing easily human error and causing thread damage. In this paper, as a new kind of real-time and non-contact measurement method, a screw thread parameter measurement system based on image processing method is developed to accurately measure the outside diameter, inside diameter, pitch diameter, pitch, thread height and other parameters of screw thread. In the system the industrial camera is employed to acquire the image of screw thread, some image processing methods are used to obtain the image profile of screw thread and a mathematics model is established to compute the parameters. The C++Builder 6.0 is employed as the software development platform to realize the image process and computation of screw thread parameters. For verifying the feasibility of the measurement system, some experiments were carried out and the measurement errors were analyzed. The experiment results show the image measurement system satisfies the measurement requirements and suitable for real-time detection of screw thread parameters mentioned above. Comparing with the traditional methods the system based on image processing method has some advantages, such as, non-contact, easy operation, high measuring accuracy, no work piece damage, fast error analysis and so on. In the industrial production, this measurement system can provide an important reference value for development of similar parameter measurement system.

Rao, Zhimin; Huang, Kanggao; Mao, Jiandong; Zhang, Yaya; Zhang, Fan



Backflow in twin-screw-type multiphase pump  

SciTech Connect

The performance of a twin-screw-type multiphase pump was investigated from the viewpoints of backflow in a gap along the twin-screw shafts and of scaleup parameters. Although both the backflow and the scaleup parameters have been recognized as important factors in developing multiphase pumps, they have not yet been clarified. The twin-screw pump was equipped with pressure sensors, set in the multiphase-test facility, and experimented with under various conditions to clarify the relationship between backflow rates and factors such as differential pressure, gas-void fractions (GVF`s), and the rotation speed of the shaft. A physical model was proposed with the empirical relationship of pressure distribution along the screw, and was successfully associated with scaleup parameters, such as the geometrical data of the twin-screw pump. Then it was used successfully to simulate the backflow in twin-screw pumps on relatively broad experimental conditions, judging from the comparison between the model and the experimental data.

Egashira, Kazuyuki; Shoda, Shinji; Tochikawa, Tetsuro [Japan National Oil Corp., Chiba (Japan); Furukawa, Akinori [Kyushu Univ. (Japan)



Effects of Feed Rate and Screw Speed on Operating Characteristics and Extrudate Properties During Single-Screw Extrusion Cooking of Rice Flour  

Microsoft Academic Search

Cereal Chem. 76(2):236-242 Rice flour (37% moisture content) was used to examine the effects of feed rate and screw speed on the specific energy input during single-screw extrusion cooking. Torque, raised by decreasing screw speed or increasing feed rate, was found to be a power law function of the ratio of feed rate to screw speed (Fr\\/Ss) with r2 >

An-I Yeh; Yih-Mon Jaw



Use of the radial groove view intra-operatively to prevent damage to the extensor pollicis longus tendon by protruding screws during volar plating of a distal radial fracture.  


The aims of this study were to assess the efficacy of a newly designed radiological technique (the radial groove view) for the detection of protrusion of screws in the groove for the extensor pollicis longus tendon (EPL) during plating of distal radial fractures. We also aimed to determine the optimum position of the forearm to obtain this view. We initially analysed the anatomy of the EPL groove by performing three-dimensional CT on 51 normal forearms. The mean horizontal angle of the groove was 17.8° (14° to 23°). We found that the ideal position of the fluoroscopic beam to obtain this view was 20° in the horizontal plane and 5° in the sagittal plane. We then intra-operatively assessed the use of the radial groove view for detecting protrusion of screws in the EPL groove in 93 fractures that were treated by volar plating. A total of 13 protruding screws were detected. They were changed to shorter screws and these patients underwent CT scans of the wrist immediately post-operatively. There remained one screw that was protruding. These findings suggest that the use of the radial groove view intra-operatively is a good method of assessing the possible protrusion of screws into the groove of EPL when plating a fracture of the distal radius. Cite this article: Bone Joint J 2013;95-B:1372-6. PMID:24078534

Lee, S K; Bae, K W; Choy, W S



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.

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



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



Safety and Efficacy of Pedicle Screws and Titanium Mesh Cage in the Treatments of Tuberculous Spondylitis of the Thoracolumbar Spine  

PubMed Central

Study Design This is a retrospective series. Purpose We wanted to analyze the safety and effectiveness of using the newer generation metallic implants (pedicle screws and/or titanium mesh) for the treatment of tuberculous spondylitis. Overview of the Literature There have been various efforts to prevent the development of a kyphotic deformity after the treatment of tuberculous spondylitis, including instrumentation of the spine. Pedicle screws and titanium mesh cages have become more and more popular for treating various spinal problems. Methods Twenty two patients who had tuberculous spondylitis were treated with anterior radical debridement and their anterior column of spine was supported with a tricortical iliac bone graft (12 patients) or by mesh (10 patients). Supplementary posterior pedicle screw instrumentation was performed in 17 of 22 patients. The combination of surgeries were anterior strut bone grafting and posterior pedicle screws in 12 patients, anterior titanium mesh and posterior pedicle screws in 5 patients and anterior mesh only without pedicle screws in 5 patients. The patients were followed up with assessing the laboratory inflammatory parameters, the serial plain radiographs and the neurological recovery. Results The erythrocyte sedimentation rate and C-reactive protein levels were eventually normalized and there was no case of persistent infection or failure to control infection in spite of a mettalic implant in situ. The overall correction of kyphotic deformity was initially 8.9 degrees, and the loss of correction was 6.2 degrees. In spite of some loss of correction, this technique effectively prevented clinically significant kyphotic deformity. The preoperative Frankel grades were B for 1 patient, C for 4, D for 4 and E for 13. At the final follow-up, 7 of 9 patients recovered completely to Frankel grade E and only two patients showed a Frankel grade of D. Conclusions Stabilizing the spine with pedicle screws and/or titanium mesh in patients with tubercuous spondylitis effectively prevents the development of kyphotic deformity and this did not prevent controlling infection when this technique was combined with radical debridement and anti-tuberculous chemotherapy.

Lee, Jae Chul; Kim, Yon-Il



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



Screw fixation of the syndesmosis: a cadaver model comparing stainless steel and titanium screws and three and four cortical fixation  

Microsoft Academic Search

We assessed syndesmotic set screw strength and fixation capacity during cyclical testing in a cadaver model simulating protected weight bearing. Sixteen fresh frozen legs with artificial syndesmotic injuries and a syndesmotic set screw made of stainless steel or titanium, inserted through three or four cortices, were axially loaded with 800N for 225,000 cycles in a materials testing machine. The 225,000

Annechien Beumer; Martin M. Campo; Ruud Niesing; Judd Day; Gert-Jan Kleinrensink; Bart A. Swierstra



First metatarsophalangeal joint arthrodesis.  


First MTP joint arthrodesis continues to be a time-honored, effective, and valuable procedure as a primary or secondary surgery for various pathologies afflicting the first ray segment. Though commonly thought of as a salvage procedure, it has proven beneficial in the management of primary hallux limitus and rigidus, geriatric hallux valgus deformity, severe arthritis of any etiology, and conditions in which joint instability or deformity are not readily correctable by more traditional approaches. Since its initial description in the 1800s, the procedure has continued to be popular among orthopedic and podiatric surgeons. Success of the procedure is highly dependent on the position of fusion. Though surgeons are often fascinated and at times obsessed with a particular fixation technique, it cannot be over-emphasized that this takes a back seat to the importance of achieving proper position to meet the needs of an individual patient. Unlike joint resection or implant arthroplasty procedures, which commonly leave the hallux lacking stability and propulsion, first MPJ fusion has been shown to be effective during weight bearing and propulsion. The success enjoyed by the senior author continues to reinforce that motion is not necessary at the first MTP joint for good, pain-free function. PMID:15012033

Yu, Gerard V; Gorby, Paul O



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.



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

PubMed Central

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

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



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



The influence of screw configuration on the pretreatment performance of a continuous twin screw-driven reactor (CTSR).  


A combination of a continuous twin screw-driven reactor (CTSR) and a dilute acid pretreatment was used for the pretreatment of biomass with a high cellulose content and high monomeric xylose hydrolyzate. With the newly modified CTSR screw configuration (Config. 3), the influences of the screw rotational speed (30-60 rpm), of the pretreatment conditions such as acid concentration (1-5%) and reaction temperature (160-175 °C) at the operating condition of biomass feeding rate (1.0 g/min) and acid feeding rate (13.4 mL/min) on the pretreatment performance were investigated. The cellulose content in the pretreated rape straw was 67.1% at the following optimal conditions: barrel temperature of 165 °C, acid concentration of 3.0% (w/v), and screw rotational speed of 30 rpm. According to the three screw configurations, the glucose yields from enzymatic hydrolysis were 70.1%, 72.9%, and 78.7% for screw Configs. 1, 2, and 3, respectively. PMID:23395738

Choi, Chang Ho; Um, Byung-Hwan; Oh, Kyeong Keun



Proximal interphalangeal arthrodesis in the horse. A retrospective study and a modified screw technique.  


Arthrodesis of the proximal interphalangeal joint was used to treat lameness resulting from osteoarthrosis and for closed subluxation in 35 horses. Six horses had bilateral arthrodeses. Several conventional internal fixation techniques and a three converging screw method were used. Criteria for success included the horse performing its previous or intended athletic activity and the owner being satisfied with the outcome. Using these criteria, a successful outcome was obtained in 65% of the 26 animals in which adequate follow-up was available. A successful outcome was observed in four of six horses with bilateral arthrodeses. The internal fixation technique used did not influence the success rate, and the duration of postoperative casting was similar in successful and unsuccessful cases. The success rate of proximal interphalangeal arthrodeses was 46% in the fore limbs and 83% in the hind limbs. Complications included infection, cast ulcers, bone or implant failure, implant loosening, and laminitis. PMID:2349775

Caron, J P; Fretz, P B; Bailey, J V; Barber, S M


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



Ipsilateral mid-third clavicle fracture with grade V acromioclavicular joint dislocation  

Microsoft Academic Search

We report the case of a 20-year-old man with an ipsilateral mid-third clavicle fracture with grade V acromioclavicular joint (ACJ) dislocation. The combination of these two injuries is rare. A literature search produced various treatment algorithms. In this case, the patient was successfully treated with a Bosworth screw.

V. Lenin Babu; K. Baskaran



A posterior approach for inspection of reduction of sacroiliac joint disruption  

Microsoft Academic Search

Summary This anatomic study was undertaken to describe a new posterior approach enabling direct inspection of reduction of sacroiliac joint disruption (SIJD), and guidance of iliosacral screw placement. The reduction of SIJD is usually monitored by inspection of the opposing sacrum and ilium at the posterior margin of the greater sciatic notch and there is a relative lack of information

N. A. Ebraheim; J. Lu; B. E. Heck; R. A. Yeasting



Arthroscopic ACL reconstruction with reverse "Y"-plasty grafts and fixation in the femur with either a bioabsorbable interference screw or an Endobutton.  


We propose a new reverse "Y"-plasty graft for use in anterior cruciate ligament (ACL) reconstruction that involves double tibial tunnels and a single femoral tunnel. With this technique, the hamstrings were used as autografts and fixed separately with bioabsorbable interference screws (group A) or Endobuttons (group B) in femurs. A prospective series of 63 patients underwent primary reconstruction of the ACL; all procedures were performed by the same surgeon. Group A included 35 patients (22 male, 13 female), with a mean age of 25.5 (17-40) years, who were followed up for 28.5 (12-48) months. Group B included 28 patients (17 male, 11 female), with a mean age of 24.3 (18-38) years, who were followed up for 29.5 (12-46) months. Lysholm, International Knee Documentation Committee (IKDC) and Larson scoring were used to compare the therapeutic effects experienced at the knee. Lysholm scores were 93.26±2.67 (group A) and 93.81±2.42 (group B); Larson scores were 91.91±2.29 (group A) and 92.81±2.39 (group B); IKDC scores were 93.89±1.88 (group A) and 94.15±1.77 (group B). None of the scoring differences between groups were statistically significant (T(1)=0.849, P(1)=0.399, T(2)=1.506, P(2)=0.137, T(3)=0.560, P(3)=0.578). The Lachman test was negative in 46 patients (90.2%) and 51 knees, including 25 (89.3%) of the 28 knees in group A and 21 (91.3%) of the 23 knees in group B. Negative Pivot shift was present postoperatively in 49 knees of 51 patients (96.1%), including 27 (96.4%) of the 28 knees in group A and 22 (95.7%) of the 23 knees in group B. All of the patients in both groups achieved full extension and at least 135° of knee flexion. This novel technique involves the creation of double tibial tunnels and a single femoral tunnel. In the tibia, there was a bone bridge, ranging from 2 to 3mm, between the two bundles, which are tensioned at different degrees of flexion to maintain the stability of the knee. In the femur, the grafts were fixed with bioabsorbable interference screws or Endobuttons. The outcomes show that normal function and joint stability were achieved in both groups, as compared with preoperative measurements. Although the outcomes in group A (grafts fixed with the bioabsorbable interference screws in the femur) was better than those observed in group B (grafts fixed with Endobuttons), there was no statistical difference between the groups. PMID:21159514

Ping, Li Wei; Bin, Song; Rui, Yang; Yang, Song; Zheng, Zhang Zheng; Yue, Ding



Windshield-wiper loosening: a complication of in situ screw fixation of slipped capital femoral epiphysis.  


A retrospective review of patients treated for slipped capital femoral epiphysis (SCFE) by in situ screw fixation with a cannulated titanium screw was performed. Of the 18 hips with at least 1-year follow-up, windshield-wiper loosening of the cannulated screw in the femoral head had occurred in three. In all three cases, the screw had been left protruding > 1.5 cm from the anterolateral cortex of the femur. We postulate that with hip motion the protruding screw is toggled by the anterolateral soft tissues, causing a windshield-wiper effect in the femoral head, leading to eventual screw loosening. We believe that leaving the screw protruding from the fascia lata is a potential source of screw loosening by the windshield-wiper mechanism and now routinely place the screw head within 1.5 cm of the anterolateral cortex of the femur. PMID:8376561

Maletis, G B; Bassett, G S


Biomechanical analysis of pedicle screw density in spinal instrumentation for scoliosis treatment: first results.  


Clinical studies reveal remarkable variation in screw patterns, or screw density in spinal instrumentation. Screw density may have a great impact on blood loss, operative time, radiation, risk of screw malposition, and cost. Thus, there is a need to understanding of the biomechanical effects of screw density so as to minimize the number of pedicle screws while ensuring safe and effective instrumentation. The objective of this study was to compare the deformity correction effects and bone-screw loadings of different pedicle screw densities in spinal instrumentation for scoliosis treatment. Spinal instrumentation simulations were performed on three scoliosis patients using 3 screw density patterns (low, preferred, and high screw density) proposed by two experienced surgeons and basic correction techniques: concave rod attachment, rod derotation, apical vertebral derotation, and convex side rod attachment. Simulation results showed that all tested screw densities generated quite similar correction, with differences between the achieved corrections all below 3°. The average bone-screw forces were 244±67N, 214±66 N, and 210±71 N, respectively for low, preferred, and high densities. It remains a complex challenge balancing the benefit of load sharing between more implants with the overconstraints and limited degrees of freedom introduced by the increased number of implants. Studies on additional screw densities and patterns proposed by more surgeons for a variety of cases, and using more diverse correction techniques are necessary to draw stronger conclusions and to recommend the optimal screw density. PMID:22744515

Wang, Xiaoyu; Aubin, Carl-Eric; Larson, A Noelle; Labelle, Hubert; Parent, Stefan



The tantalum screw for treating femoral head necrosis: rationale and results  

PubMed Central

Femoral head necrosis (FHN) is a progressive pathology due to the failure of blood supply to the proximal femoral epiphysis, with consequent necrosis of the sub-chondral bone and collapse of the articular cartilage and loss of congruity between the head and the acetabulum. Borrowing the biological and mechanical principles from the vascularized fibular graft technique for the femoral neck, the tantalum screws have been introduced. They show an extraordinary porosity, osteoconductivity, biocompatibility and very good osteoinductivity. Vitreous tantalum can be processed to take the form of a screw, with a round medial extremity and a 25 mm threaded lateral extremity that can be inserted into the neck of the femur, thereby supporting the articular cartilage, stimulating the repair process, interrupting the interface between necrotic and healthy tissue and favoring local vascularization. We have drawn up a treatment protocol for early-stage FHN, based on the insertion of a tantalum screw into the femoral neck. The implant has a cylindrical shape, with a 10 mm diameter in the smooth part and 15 mm in the threaded part. It is available in different sizes from 70 to 130 mm, with 5 mm increments. The aim of the study is to describe the clinical and instrumental results of the tantalum screw for FHN. From June 2004 to June 2006 we performed 15 implants. The tantalum screw was inserted with an incision on the trochanteric region with traction and under X-ray control. For the clinical evaluation of the hip, we used the Harris hip score (HHS). For diagnosis and staging we used standard X-rays in two views and/or MRI, using the Steinberg classification (J Bone Joint Surg Br 77:34–41, 1995) and CT. In all cases, the osteonecrosis extended to not more than 30% of the joint surface and the cartilage was intact with no collapse. To assess the results, we compared the pre-operative and the post-operative HHS, calculated the percentage differences between the two. We then compared X-rays, CT scans and MRI before and some time after the operation to assess whether the problem had been addressed, taking into account the intracancellous edema and the possible extension of necrosis. After an average follow-up period of 15.43 ± 5.41 months, ten implants (seven patients out of ten) were examined and all but one patient showed a marked improvement in HHS (the average increase was 127.9%), with no further progression of the disease. We believe that this procedure can be suitable for young patients with limited first or second stage osteonecrosis. The objective for the foreseeable future is to resolve the pain, improve the quality of life and prevent or at least postpone arthroplasty.

Aldegheri, R.; Berizzi, A.



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.

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



Design of internal screw thread measuring device based on the Three-Line method principle  

NASA Astrophysics Data System (ADS)

In accordance with the principle of Three-Line, this paper analyze the correlation of every main parameter of internal screw thread, and then designed a device to measure the main parameters of internal screw thread. Internal thread parameters, such as the pitch diameter, thread angle and screw-pitch of common screw thread, terraced screw thread, zigzag screw thread were obtained through calculation and measurement. The practical applications have proved that this device is convenience to use, and the measurements have a high accuracy. Meanwhile, the application for the patent of invention has been accepted by the Patent Office (Filing number: 200710044081.5).

Hu, Dachao; Chen, Jianguo



[Observations on before and after employ of screw of implant denture with SEM].  


The loss of screw is one of the clinic complication in MDIC implant denture cases. The purpose of this study is to find the cause of loss of screw. The authors has studied MDIC implant denture with SEM before and after employ of the screw and found that the causes of screw loss were crevice corrosion and friction pressure. Crevice corrosion may promote the loss of screw. Base the above condition, it is necessary to select Ti-alloy screw and associat with anticorrosive measure in MDIC implant denture construction. PMID:10677963

Song, Y; Xu, J; Ma, X



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



A processing method for orthodontic mini-screws reuse  

PubMed Central

Background: The possibility of mini-screws reuse would reduce treatment cost. The aim of this study is to introduce a new method (application of phosphoric acid 37% for 10 minutes followed by sodium hypochlorite 5.25% for 30 minutes) for cleansing of mini-screws and assessing the efficacy of this method. The effects of this processing on the insertion, removal, and fracture torques of mini-screws were evaluated. Materials and Methods: This experimental study was done in two parts. In part I the amount of calcium ion on mini-screws surfaces as an index of tissue remnants was assessed. In part II of this study, the effects of previous use, processing method, and resterilization on the insertion, removal, and fracture torques of mini-screws were assessed. Each part of this study had 3 groups; non-processed used (NP), processed used (P), and as-received (C). Each group had 16 samples in part I and 20 samples. Non parametric statistical tests were used in part I and one way ANOVA in part II. Results: The mean amount of calcium ion in groups non-processed (NP1), processed (P1), and control (C1) were 4.7, 0.43, and 0.02 ppm, respectively. The amount of calcium ion in group NP1 was significantly greater than in the other groups (P = 0.000), but the difference between groups P1 and C1 was not significant (P = 0.087). The mean insertion torque of group NP2 was lower than that of other groups (P < 0.05) but P2 and C2 did not have significant differences (P = 0.988). The mean of removal and fracture torque did not have significant differences among all groups. Conclusion: Cleaning of used mini-screws with phosphoric acid 37% (10 minutes) and sodium hypochlorite 5.25% (30 minutes) reduces tissue remnants to the level of as-received mini-screws. So it can be suggested as a processing method of used mini-screws. Previous insertion of mini-screws into the bone and above-mentioned processing method and resterilization with autoclave had no adverse effects on insertion, removal, and fracture torque values as mechanical properties indices.

Noorollahian, Saeed; Alavi, Shiva; Monirifard, Mohammad



Percutaneous Iliac Screws for Minimally Invasive Spinal Deformity Surgery  

PubMed Central

Introduction. Adult spinal deformity (ASD) surgeries carry significant morbidity, and this has led many surgeons to apply minimally invasive surgery (MIS) techniques to reduce the blood loss, infections, and other peri-operative complications. A spectrum of techniques for MIS correction of ASD has thus evolved, most recently the application of percutaneous iliac screws. Methods. Over an 18 months 10 patients with thoracolumbar scoliosis underwent MIS surgery. The mean age was 73 years (70% females). Patients were treated with multi-level facet osteotomies and interbody fusion using expandable cages followed by percutaneous screw fixation. Percutaneous iliac screws were placed bilaterally using the obturator outlet view to target the ischial body. Results. All patients were successfully instrumented without conversion to an open technique. Mean operative time was 302 minutes and the mean blood loss was 480?cc, with no intraoperative complications. A total of 20 screws were placed successfully as judged by CT scanning to confirm no bony violations. Complications included: two asymptomatic medial breaches at T10 and L5, and one patient requiring delayed epidural hematoma evacuation. Conclusions. Percutaneous iliac screws can be placed safely in patients with ASD. This MIS technique allows for successful caudal anchoring to stress-shield the sacrum and L5-S1 fusion site in long-segment constructs.

Wang, Michael Y.



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.



Screw dislocations in GaN grown by different methods.  


A study of screw dislocations in hydride-vapor-phase-epitaxy (HVPE) template and molecular-beam-epitaxy (MBE) overlayers 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. PMID:15306067

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



Percutaneous iliac screws for minimally invasive spinal deformity surgery.  


Introduction. Adult spinal deformity (ASD) surgeries carry significant morbidity, and this has led many surgeons to apply minimally invasive surgery (MIS) techniques to reduce the blood loss, infections, and other peri-operative complications. A spectrum of techniques for MIS correction of ASD has thus evolved, most recently the application of percutaneous iliac screws. Methods. Over an 18 months 10 patients with thoracolumbar scoliosis underwent MIS surgery. The mean age was 73 years (70% females). Patients were treated with multi-level facet osteotomies and interbody fusion using expandable cages followed by percutaneous screw fixation. Percutaneous iliac screws were placed bilaterally using the obturator outlet view to target the ischial body. Results. All patients were successfully instrumented without conversion to an open technique. Mean operative time was 302 minutes and the mean blood loss was 480?cc, with no intraoperative complications. A total of 20 screws were placed successfully as judged by CT scanning to confirm no bony violations. Complications included: two asymptomatic medial breaches at T10 and L5, and one patient requiring delayed epidural hematoma evacuation. Conclusions. Percutaneous iliac screws can be placed safely in patients with ASD. This MIS technique allows for successful caudal anchoring to stress-shield the sacrum and L5-S1 fusion site in long-segment constructs. PMID:22900162

Wang, Michael Y



Security and Stability Operations Measures of Effectiveness.  

National Technical Information Service (NTIS)

Security and stabilization operations (SASO) will continue to confront Joint Task Force (JTF) Commanders with a unique set of challenges and concerns. Future joint forces will require new skill sets to meet the challenges of SASO. The current measures of ...

D. Nathanson



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.



SEM and fractography analysis of screw thread loosening in dental implants.  


Biological and technical failures of implants have already been reported. Mechanical factors are certainly of importance in implant failures, even if their exact nature has not yet been established. The abutment screw fracture or loosening represents a rare, but quite unpleasant failure. The aim of the present research is an analysis and structural examination of screw thread or abutment loosening compared with screw threads or abutment without loosening. The loosening of screw threads was compared to screw thread without loosening of three different implant systems; Branemark (Nobel Biocare, Gothenburg, Sweden), T.B.R. implant systems (Benax, Ancona, Italy) and Restore (Lifecore Biomedical, Chaska, Minnesota, USA). In this study broken screws were excluded. A total of 16 screw thread loosenings were observed (Group I) (4 Branemark, 4 T.B.R and 5 Restore), 10 screw threads without loosening were removed (Group II), and 6 screw threads as received by the manufacturer (unused) (Group III) were used as control (2 Branemark, 2 T.B.R and 2 Restore). The loosened abutment screws were retrieved and analyzed under SEM. Many alterations and deformations were present in concavities and convexities of screw threads in group I. No macroscopic alterations or deformations were observed in groups II and III. A statistical difference of the presence of microcracks were observed between screw threads with an abutment loosening and screw threads without an abutment loosening. PMID:17897496

Scarano, A; Quaranta, M; Traini, T; Piattelli, M; Piattelli, A


Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery -- a finite element analysis  

PubMed Central

Background Little is known about the biomechanical effectiveness of transforaminal lumbar interbody fusion (TLIF) cages in different positioning and various posterior implants used after decompressive surgery. The use of the various implants will induce the kinematic and mechanical changes in range of motion (ROM) and stresses at the surgical and adjacent segments. Unilateral pedicle screw with or without supplementary facet screw fixation in the minimally invasive TLIF procedure has not been ascertained to provide adequate stability without the need to expose on the contralateral side. This study used finite element (FE) models to investigate biomechanical differences in ROM and stress on the neighboring structures after TLIF cages insertion in conjunction with posterior fixation. Methods A validated finite-element (FE) model of L1-S1 was established to implant three types of cages (TLIF with a single moon-shaped cage in the anterior or middle portion of vertebral bodies, and TLIF with a left diagonally placed ogival-shaped cage) from the left L4-5 level after unilateral decompressive surgery. Further, the effects of unilateral versus bilateral pedicle screw fixation (UPSF vs. BPSF) in each TLIF cage model was compared to analyze parameters, including stresses and ROM on the neighboring annulus, cage-vertebral interface and pedicle screws. Results All the TLIF cages positioned with BPSF showed similar ROM (<5%) at surgical and adjacent levels, except TLIF with an anterior cage in flexion (61% lower) and TLIF with a left diagonal cage in left lateral bending (33% lower) at surgical level. On the other hand, the TLIF cage models with left UPSF showed varying changes of ROM and annulus stress in extension, right lateral bending and right axial rotation at surgical level. In particular, the TLIF model with a diagonal cage, UPSF, and contralateral facet screw fixation stabilize segmental motion of the surgical level mostly in extension and contralaterally axial rotation. Prominent stress shielded to the contralateral annulus, cage-vertebral interface, and pedicle screw at surgical level. A supplementary facet screw fixation shared stresses around the neighboring tissues and revealed similar ROM and stress patterns to those models with BPSF. Conclusions TLIF surgery is not favored for asymmetrical positioning of a diagonal cage and UPSF used in contralateral axial rotation or lateral bending. Supplementation of a contralateral facet screw is recommended for the TLIF construct.



The Influence of Screw Positions of Bone Fixation Screws on a TMJ Implant  

Microsoft Academic Search

\\u000a There are several diseases that can affect the human temporomandibular joint (TMJ), among which we highlight cancer, trauma\\u000a or fracture, congenital malformation and osteochondritis.\\u000a \\u000a \\u000a TMJ reconstruction was developed to improve mandibular function, reduce disability. Total replacement of the TMJ involves\\u000a the removal of the “non functional” joint and placing an artificial one. Materials and geometry play an important key role

A. Ramos; M. Mesnard; C. Relvas; A. Completo; P. Talaia; J. A. Simões


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.



[Odontoid fracture: Long-term subarachnoid hemorrhage after anterior screw fixation. Case report and literature review].  


Odontoid fractures have been classified by Anderson and D'Alonzo into three main categories. The most unstable injuries, type II fractures involve the base of the odontoid peg at the junction with the C2 body. Due to the proximity of vital neural structures, fracture of the odontoid process may result in instability and fatal neurological damage. Treatment aims to re-establish stability of the atlanto-axial complex by restoring the odontoid process. This may be achieved by conservative or surgical treatment. Anterior screw fixation of the odontoid peg is an interresting alternative surgical option but this technique has a significant complication rate. However, vascular injury is very rare with three case reported in the literature: one case of an intracranial vertebral artery (VA) injury, one case of a cervical internal carotid artery (ICA) injury and one case of anterior pseudoaneurysm of the spinal artery branch. We report a new case of long term vascular injury after screw fixation revealed by a subarachnoid hemorrhage. We discuss the incidence, the mechanisms of injury and the conditions necessary for the occurrence of this complication. PMID:22683208

Le Corre, M; Suleiman, N; Lonjon, N



Biodegradation of Inion fast-absorbing biodegradable plates and screws.  


Biodegradable plates and screws are recommended for use in surgery of the craniofacial skeleton of children. To be effective and not interfere with growth of the child's skull, the plates must biodegrade sufficiently to release the holding power of the plate and screw within 1 year. It is also essential that excessive foreign body reaction and cyst formation does not occur when the plates and screws biodegrade. The purpose of this experimental study was to evaluate the rate of biodegradation of Inion CPS Baby biodegradable plates and screws under different clinical circumstances in the rabbit craniofacial skeleton and evaluate their efficacy for use in pediatric craniofacial surgery. Foreign body reaction would be evaluated. Inion baby plates and screws were tested in a rabbit model. Plates were applied to the frontal bone, over a bony defect of the parietal bone, to a nasal bone fracture, and inserted in the subcutaneous space over the occipital bone in thirty 6-week-old rabbits. Six rabbits were euthanized at 9, 12, 15, and 18 months' postoperative time point and examined for residual plates and screws. Bone from each surgical site was excised, fixed by immersion in 10% neutral-buffered formalin, decalcified in Immunocal solution, and examined by 7-microm paraffin sections stained with hematoxylin and eosin. At 9 months, the plates and screws had effectively biodegraded and no longer had holding power on the bones. Fragmentation of the implant material was noted. Residual implant material was still present on gross and histologic examination in rabbits at 9, 12, 15, and 18 months. Residue of a screw was still palpable in 1 rabbit at 18 months. There was no evidence of cyst formation in any of the examined specimens. Macrophages and giant cells were present in most of the specimens at 9, 12, 15, and 18 months. Findings from the current study revealed a relative short resorption time (9 mo) and normal inflammatory sequelae in an adult rabbit model. These findings suggest that these plates may be used safely in fixing the pediatric craniofacial skeleton. PMID:18520394

Losken, H Wolfgang; van Aalst, John A; Mooney, Mark P; Godfrey, Virginia L; Burt, Tripti; Teotia, Sumeet; Dean, Shay B; Moss, Jonathan R; Rahbar, Reza




Microsoft Academic Search

factors that leads to progressive degeneration of the joint and continued deficits in joint dynamics, balance, and coordination. Much clinical research has demonstrated that individuals with proprioception and neuromuscular response deficits as a result of injury, lesions, and joint degeneration are less capable of maintaining postural stability and equilibrium. However, no normal reference data on ankle proprioception represented by kinesthesia

Jing Xian Li; Blaine Hoshizaki


Fixation with reconstruction plates under critical conditions: the role of screw characteristics  

Microsoft Academic Search

Mandibular angular ostectomy defects in 12 sheep were bridged with a titanium plate system (THORP), designed according to the screw-plate-locking principle. Two screw designs (hollow and solid) and two rough (plasma-coated, sandblasted)-surface and one smooth (anodized)-surface structure were tested in a critical two-screw anchorage model. Fixation with two screws only per fragment was successful in only one-third of the cases.

Anna-Lisa Söderholm; Berton A. Rann; Kai Skutnabb; Christian Lindqvist



The optimal transarticular c1-2 screw length and the location of the hypoglossal nerve  

Microsoft Academic Search

BACKGROUNDInjury to the hypoglossal nerve is a complication associated with transarticular C1-2 screw placement. This complication can be caused by a misdirected or too long screw. Little is known about the optimal screw length and its relationship to the hypoglossal nerve.METHODSTwenty cervical spine specimens were used to study the optimal length of the transarticular C1-2 screw. Using the Magerl technique,

Nabil A Ebraheim; Joseph R Misson; Rongming Xu; Richard A Yeasting



Kinematic Structure of Machines for Cutting Screws with a Variable Pitch  

Microsoft Academic Search

In some branches of the industry, for moving products subsequently subjected to required compaction and shaping, for example in production of plastic articles, screws with a variable pitch are used to ensure axially-directed compaction of the product. In general, in the process of manufacture of screws with a variable pitch, the actuating motion of the tool occurs along the screw

V. A. Vanin



Defects in hexed gold prosthetic screws: A metallographic and tensile analysis  

Microsoft Academic Search

Statement of Problem. Prosthetic gold screw fracture remains a clinical problem in implant prosthodontics. Purpose. This study examined hexed gold prosthetic screws for internal defects and determined the effect of these defects on tensile strength. The microstructure, microhardness, and major constituents of the alloys also were determined. Material and Methods. Four intact hexed gold prosthetic screws, 1 from each of

Sameer K. Rambhia; William W. Nagy; Raymond A. Fournelle; Virendra B. Dhuru



The effect of repeated torque on the ultimate tensile strength of slotted gold prosthetic screws  

Microsoft Academic Search

Statement of Problem. Repeated torque may alter the mechanical properties and fracture resistance of certain prosthetic retaining screws. Purpose. This study evaluated the effect of repeated torque and salivary contamination on the ultimate tensile strength of one type of slotted gold prosthetic retaining screw. Material and Methods. Forty-five slotted gold prosthetic screws from the same manufacturer (Implant Innovations) were divided

Mohammed A. Al Rafee; William W. Nagy; Raymond A. Fournelle; Virendra B. Dhuru; George K. Tzenakis; Charles E. Pechous



A novel approach toward pedicle screw placement in the thoracic spine  

Microsoft Academic Search

Purpose of study: Because of the smaller size of the thoracic pedicle, primarily in the coronal plane, most surgeons have opted to avoid the used of transpedicular screws in the thoracic spine. A new technique for placement of screws through thoracic pedicles with and without lateral wall violation is described.Methods used: From April 1992 through February 1999, 1,064 pedicle screws

John Thalgott; Mark Kabins; James Giuffre



Effect of an antirotation resistance form on screw loosening for single implant-supported crowns  

Microsoft Academic Search

Statement of problem: The gold screw of the single tooth implant-supported restoration has frequently been reported to exhibit the problem of screw loosening. Purpose: This in vitro study considered an antirotation resistance form with an increased moment arm length as a strategy to increase the net effect of the retaining screw preload. Material and methods: Three groups examined included (a)

Hoda Aboyoussef; Saul Weiner; David Ehrenberg



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



Failure Analysis of Ozark, Arkansas, Power Plant Socket-Head Cap Screws.  

National Technical Information Service (NTIS)

This research analyzed the socket-head cap screws which failed in the turbines of the Ozark Power Plant, Ozark, AR. The cause of failure was found to be fatigue in improperly heat-treated cap screws. The reduced fatigue strength of the cap screws was furt...

E. P. Cox



Posterior thoracic segmental pedicle screw instrumentation: Evolving methods of safe and effective placement  

Microsoft Academic Search

The use of pedicle screw instrumentation in the spine has evolved over the last two decades. The initial use of pedicle screws began in the lumbar spine. As surgeons have become more comfortable with the complex anatomy required for accurate screw placement, the use of pedicle instrumentation has evolved to include their use in the thoracolumbar and thoracic spine. The

S. C. Zeiller; J. Lee; M. Lim; A. R. Vaccaro



To retain or remove the syndesmotic screw: a review of literature  

Microsoft Academic Search

Introduction: Syndesmotic positioning screws are frequently placed in unstable ankle fractures. Many facets of adequate placement techniques have been the subject of various studies. Whether or not the syndesmosis screw should be removed prior to weight-bearing is still debated. In this study, the recent literature is reviewed concerning the need for removal of the syndesmotic screw. Materials and methods: A

T. Schepers



[Interpositional arthrodesis of the first metatarsophalangeal joint].  


Background: Interpositional arthrodesis of the first metatarsophalangeal joint is a rare procedure which is indicated for reconstruction of an insufficient, short first ray due to loosening of an endoprosthesis, osteomyelitis or after a Keller procedure. Patients and Methods: In a retrospective study we evaluated the outcome of 15 patients with a mean age of 62 years, who underwent an interpositional arthrodesis of the first MTP joint. Correction of the deformity was achieved by osteotomy of the tricortical bone graft. Osteosynthesis was performed by use of screw fixation alone or by combined screw, plate and K-wire fixation. Postoperatively patients were mobilised for 10 weeks in a forefoot off loading shoe. Clinical and radiological examination was performed 10 weeks postoperatively. Radiological parameters such as hallux valgus angle, MTP dorsiflexion angle and the graft size were measured. In all patients pre- and postoperatively, the intensity of pain (VAS), the overall satisfaction with the procedure and the American orthopaedic foot and ankle score (AOFAS score) were evaluated. Results: The mean follow-up was 26 months (range 4-48 months). The mean pain intensity measured with the VAS was reduced from 7.5 preoperatively to 0.5 postoperatively. In 14 patients fusion of the arthrodesis was achieved at a mean of 12 weeks. One patient developed a pseudarthrosis which was effectively treated by extracorporeal shockwaves. Postoperatively radiological measurements demonstrated a mean hallux valgus angle of 16° (range 6-28°), a mean MTP dorsiflexion angle of 17° (range 12-27°) and a mean graft size of 16 mm (range 10-30 mm). The mean AOFAS score improved from 26 preoperatively to 81 postoperatively. All but 1 patient were satisfied with the final outcome and achieved free mobility. Conclusions: Interpositional arthrodesis of the first MTP joint achieves good clinical and radiological results with a high level of patient satisfaction in patients with an insufficient and short first ray of the foot. PMID:24129722

Waldecker, U



Noimisothermal Model of Single Screw Extrusion of Generalized Newtonian Fluids  

Microsoft Academic Search

A nonisothermal model of Ike single screw extrusion processing of generalized Newtonian fluids is presented. Various temperature dependent forms of a generalized Newtonian fluid constitutive equation representing the Herschel-Bulkley fluid and its simplifications, including Bingham plastic, power law of Ostwald-de Waele, and Newtonian fluids, are applicable. The model includes the generally ignored transverse convection terms of the equation of energy.

Adeniyi Lawal; Dilhan M. Kalyon



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...


Primary thoracoplasty and pedicle screw instrumentation in thoracic idiopathic scoliosis  

Microsoft Academic Search

Thoracoplasty in combination with spine fusion is an established method to address the rib cage deformity in idiopathic scoliosis. Most reports about thoracoplasty and scoliosis correction focused on Harrington or CD instrumentation. We report a retrospective analysis of 21 consecutive patients, who were treated with pedicle screw instrumentation for idiopathic thoracic scoliosis and concomitant thoracoplasty. Minimal follow up was 24

Kan Min; Beat Waelchli; Frederik Hahn



Fuzzy Sliding Mode Control of a Ball Screw Driven Stage  

Microsoft Academic Search

Ball screw driven systems are widely used for motion control applications. In such systems, friction dominates the resulting performance and it should be compensated to achieve high precision in positioning and tracking. Hereby a friction model is introduced to describe dynamic behavior of the system and then three control strategies i.e. sliding mode control (SMC), complementary sliding mode control (CSMC)

M. Shams; M. Zarei-nejad; M. Safdari




Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

39. VIEW OF VESSEL STERN-ON IN DRYDOCK. NOTE TWIN SCREWS AND RUDDER. GENTLEMEN IN VIEW UNKNOWN Original 5'x5' photograph taken by Robert S. Douglas in 1966 - Pilot Schooner "Alabama", Moored in harbor at Vineyard Haven, Vineyard Haven, Dukes County, MA


Dynamics of parallel manipulators by means of screw theory  

Microsoft Academic Search

An approach to the dynamic analysis of parallel manipulators is presented. The proposed method, based on the theory of screws and on the principle of virtual work, allows a straightforward calculation of the actuator forces as a function of the external applied forces and the imposed trajectory. In order to show the generality of such a methodology, two case studies

J. Gallardo; J. M. Rico; A. Frisoli; D. Checcacci; M. Bergamasco



Throttling means for geothermal streams. [helical screw expander  

Microsoft Academic Search

A helical screw expander for deriving energy from geothermally heated water is described. The expander includes a pair of helical rotors with helical structures fitted in an expansion chamber. The geothermally heated water is introduced into said chamber through a throttle port located at an end face of the expansion chamber, whereby precipitation which occurs as a consequence of reduction




Bone registration method for robot assisted surgery: pedicle screw insertion  

Microsoft Academic Search

SUMMARY A registration method that identifies bone geometry with respect to a robotic manipulator arm is presented. Although the method is generally applicable to many orthopaedic internal fixation, it was only demonstrated for the insertion of pedicle screws in vertebral bodies for spine fixation. The method relies upon obtaining an impression of the vertebral bodies. Computed Tomography scans of both

K Abdel-Malek; D P McGowan; V K Goel; D Kowalski; A Hager




Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey



Plate and screw fixation for atlanto-axial subluxation  

Microsoft Academic Search

Summary Our experience with 30 cases of atlanto-axial dislocation, over the period of 3 years and 9 months, is described. A modified plate and screw method of fixation of the lateral masses of the atlas and axis was successfully used in these cases. The technical aspects and merits of the method, wherein a 100% union rate was achieved, with no

A. Goel; V. Laheri



Stress Reduction at the Production of Bottle-Cap Screws.  

National Technical Information Service (NTIS)

To seal contents gastight on a large scale aluminium cap screws are produced on production lines where in a full extent stress at the operating positions is a fact harmful vapors, heat and other factors injurious to health. Only with new engineering the p...

V. Schach H. Schach H. Haeufgloeckner



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



Outpatient percutaneous screw fixation of the acute Jones fracture  

Microsoft Academic Search

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

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



Complications with K-wire Insertion for Percutaneous Pedicle Screws.  


STUDY DESIGN:: Retrospective Study. OBJECTIVE:: To determine the risk profile and complications associated with anterior vertebral body breach by K-wire during percutaneous pedicle screw insertion. SUMMARY OF BACKGROUND DATA:: Percutaneous techniques and indications are rapidly expanding with numerous studies now supporting the use of percutaneous pedicle screw stabilisation as an adjunct for multiple pathologies such as degenerative, tumour and trauma. With regards to complication rates, little has been documented. METHODS:: 525 consecutive percutaneous pedicle screws were retrospectively reviewed and the rate of anterior vertebral body breach was recorded, including any potential adverse clinical outcomes. RESULTS:: Of 525 percutaneous pedicle screw insertions, there were 7 anterior breaches recorded. We rated the breaches as a minor breach (<5 mm; n=3), moderate breach (5-25 mm; n=2) and major breach (>25 mm; n=2). Two patients had a postoperative ileus with a retroperitoneal haematoma on post-op CT scan. No patient required reoperation or blood transfusion. CONCLUSION:: The indications for minimally invasive spinal fusion have expanded to include conditions such as degenerative, trauma, deformity, infection and neoplasia. While the rate of anterior K-wire breach is low, the technique requires the acquisition of a new set of skills including the safe passage of a K-wire, and knowledge of potential complications that may ensue. PMID:23698104

Mobbs, Ralph J; Raley, Darryl A



Gas Expansion Motor with Screw-Type Air Compressor.  

National Technical Information Service (NTIS)

This pilot project in the field of energy conversion aims to utilize the unused exergetic gradient in the gas fed into the furnaces of a glass fabrication plant by means of a gas expansion motor which drives a screw-type compressor. The experiences gained...

H. B. Fuehr



Two Turns of the Screw: Feminism and the Humanities.  

ERIC Educational Resources Information Center

Maintains that the humanities get "screwed" in the academy because they are feminized. Explores this process of "feminization," focusing on college English departments. Offers a different view of the relationship between "soft" humanities and "hard" disciplines, reconceived from a feminist perspective. (SR)

Heinzelman, Susan Sage



Screw dislocation in zirconium: An ab initio study  

NASA Astrophysics Data System (ADS)

Plasticity in zirconium is controlled by 1/3<12¯10> screw dislocations gliding in the prism planes of the hexagonal close-packed structure. This prismatic and not basal glide is observed for a given set of transition metals like zirconium and is known to be related to the number of valence electrons in the d band. We use ab initio calculations based on the density functional theory to study the core structure of screw dislocations in zirconium. Dislocations are found to dissociate in the prism plane in two partial dislocations, each with a pure screw character. Ab initio calculations also show that the dissociation in the basal plane is unstable. We calculate then the Peierls barrier for a screw dislocation gliding in the prism plane and obtain a small barrier. The Peierls stress deduced from this barrier is lower than 21 MPa, which is in agreement with experimental data. The ability of an empirical potential relying on the embedded atom method (EAM) to model dislocations in zirconium is also tested against these ab initio calculations.

Clouet, Emmanuel



Bimaxillary protrusion with masseter muscle hypertrophy treated with titanium screw anchorage and masseter surgical reduction.  


This case report describes the treatment of a patient with bimaxillary protrusion and masseter muscle hypertrophy. At age 21 years 7 months, this woman had temporomandibular disorder (TMD) symptoms, severe bimaxillary protrusion, and a prominent mandibular angle with facial asymmetry. After an attempt to alleviate the TMD symptoms with occlusal splint stabilization, portions of the masseter muscle and the mandible were surgically removed. Titanium screws were placed bilaterally in both arches, and a retraction force was applied. After active treatment for 38 months, the convexity of the facial profile with lip protrusion was improved remarkably, and good occlusion was achieved. The prominent mandibular angle with facial asymmetry was improved as a result of the surgical reduction of the masseter muscle and the modeling ostectomy near the masseteric tuberosity. The TMD symptoms disappeared, and the jaw movement pattern became normal. Therefore, our results suggest that this combination treatment would be useful for masseter muscle hypertrophy for morphologic and functional problems. PMID:19361742

Hashimoto, Takashi; Kuroda, Shingo; Kamioka, Hiroshi; Mishima, Katsuaki; Sugahara, Toshio; Takano-Yamamoto, Teruko



Investigation of the interaction between hydrogen and screw dislocation in silicon by first-principles calculations.  


The stability of atomic and molecular hydrogen in the vicinity of a screw dislocation in silicon has been investigated using first-principles calculations. The lowest energy configurations are obtained for H atoms located in the dislocation core, suggesting that the segregation of hydrogen is favoured in the dislocation core. It is found that a spontaneous dissociation of H(2) could occur in the dislocation core. Finally, the variation of the interaction energy between hydrogen and the dislocation core as a function of the separation distance has been calculated. There is no sizeable interaction variation for H(2). However, in the case of a single H, an inverse law has been obtained, which can be explained by the anisotropic stress field generated by the insertion of H in the silicon lattice. PMID:21386298

Matsubara, M; Godet, J; Pizzagalli, L



A technique for indirect fabrication of an implant-supported, screw-retained, fixed provisional restoration in the esthetic zone.  


This article describes an alternative technique for the fabrication of an implant-supported, screw-retained, fixed provisional restoration in the esthetic zone. After an implant-level impression is made with a polyether impression material, the provisional restoration is fabricated indirectly. This technique is easy, saves time, and has economic advantages, while maintaining color stability and esthetic properties for the provisional restoration. It may be contraindicated for severely misaligned implants that require extensive reduction of the implant temporary abutments and denture teeth laminates. PMID:19961998

Lin, Wei-Shao; Ercoli, Carlo



Placement of pedicle screws in thoracic idiopathic scoliosis: a magnetic resonance imaging analysis of screw placement relative to structures at risk  

Microsoft Academic Search

In posterior pedicle screw instrumentation of thoracic idiopathic scoliosis, screw malposition might cause significant morbidity\\u000a in tems of possible pleural, spinal cord, and aorta injury. Preoperative axial magnetic resonace images (MRI) in 12 consecutive\\u000a patients with right thoracic adolescent scoliosis, all with King type 3 curves, were analyzed in order to evaluate the relationship\\u000a between the inserted pedicle screw position

Ahmet Y?lmaz ?arlak; Levent Buluç; Hasan Tahsin Sar?soy; Kaya Memi?o?lu; Bilgehan Tosun



Anterior retropharyngeal fixation C1-2 for stabilization of atlantoaxial instabilities: study of feasibility, technical description and preliminary results  

Microsoft Academic Search

Posterior transarticular screw fixation C1-2 with the Magerl technique is a challenging procedure for stabilization of atlantoaxial instabilities. Although its high primary stability favoured it to sublaminar wire-based techniques, the close merging of the vertebral artery (VA) and its violation during screw passage inside the axis emphasizes its potential risk. Also, posterior approach to the upper cervical spine produces extensive,

Heiko Koller; Volker Kammermeier; Dietmar Ulbricht; Allan Assuncao; Stefan Karolus; Boris van den Berg; Ulrich Holz



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



Translaminar facet joint screws to enhance segmental fusion of the lumbar spine  

Microsoft Academic Search

De 1984 à 1988, 70 arthrodèses lombaires et lombo-sacrées renforcées par un vissage translamaire des articulations interapophysaires ont été réalisées consécutivement pour des atteintes dégénératives segmentaires du rachis. Vingt patients ont eu dans le m^eme temps une décompression partielle pour sténose centrale, 15 une discectomie et 19 une décompression radiculaire latérale. Le délai moyen de fusion a été de 4,5

D. G. Marchesi; N. Boos; K. Zuber; M. Aebi



Bioresorbable screws reinforced with phosphate glass fibre: manufacturing and mechanical property characterisation.  


Use of bioresorbable screws could eliminate disadvantages associated with metals such as removal operations, corrosion, MRI interference and stress shielding. Mechanical properties of bioresorbable polymers alone are insufficient for load bearing applications application as screws. Thus, reinforcement is necessary to try and match or surpass the mechanical properties of cortical bone. Phosphate based glass fibres were used to reinforce polylactic acid (PLA) in order to produce unidirectionally aligned (UD) and unidirectionally plus randomly distributed (UD/RM) composite screws (P40 UD and P40 UD/RM). The maximum flexural and push-out properties for the composite screws (P40 UD and P40 UD/RM) increased by almost 100% in comparison with the PLA screws. While the pull-out strength and stiffness of the headless composite screws were ?80% (strength) and ?130% (stiffness) higher than for PLA, those with heads exhibited properties lower than those for PLA alone as a result of failure at the heads. An increase in the maximum shear load and stiffness for the composite screws (?30% and ?40%) in comparison to the PLA screws was also seen. Maximum torque for the PLA screws was ?1000 mN m, while that for the composite screws were slightly lower. The SEM micrographs for P40 UD and P40 UD/RM screws revealed small gaps around the fibres, which were suggested to be due to buckling of the UD fibres during the manufacturing process. PMID:23122715

Felfel, R M; Ahmed, I; Parsons, A J; Rudd, C D



Transient Non-Newtonian Screw Flow  

NASA Astrophysics Data System (ADS)

The influence of axial flow on the transient response of the pseudoplastic rotating flow is carried out. The fluid is assumed to follow the Carreau-Bird model and mixed boundary conditions are imposed. The four-dimensional low-order dynamical system, resulted from Galerkin projection of the conservation of mass and momentum equations, includes additional nonlinear terms in the velocity components originated from the shear-dependent viscosity. In absence of axial flow the base flow loses its radial flow stability to the vortex structure at a lower critical Taylor number, as the pseudoplasticity increases. The emergence of the vortices corresponds to the onset of a supercritical bifurcation which is also seen in the flow of a linear fluid. However, unlike the Newtonian case, pseudoplastic Taylor vortices lose their stability as the Taylor number reaches a second critical number corresponding to the onset of a Hopf bifurcation. Existence of an axial flow, manifested by a pressure gradient appears to further advance each critical point on the bifurcation diagram. In addition to the simulation of spiral flow, the proposed formulation allows the axial flow to be independent of the main rotating flow. Complete transient flow field together with viscosity maps are also presented.

Ashrafi, Nariman



Pullout strength of anterior spinal instrumentation: a product comparison of seven screws in calf vertebral bodies  

PubMed Central

A lot of new implant devices for spine surgery are coming onto the market, in which vertebral screws play a fundamental role. The new screws developed for surgery of spine deformities have to be compared to established systems. A biomechanical in vitro study was designed to assess the bone–screw interface fixation strength of seven different screws used for correction of scoliosis in spine surgery. The objectives of the current study were twofold: (1) to evaluate the initial strength at the bone–screw interface of newly developed vertebral screws (Universal Spine System II) compared to established systems (product comparison) and (2) to evaluate the influence of screw design, screw diameter, screw length and bone mineral density on pullout strength. Fifty-six calf vertebral bodies were instrumented with seven different screws (USS II anterior 8.0 mm, USS II posterior 6.2 mm, KASS 6.25 mm, USS II anterior 6.2 mm, USS II posterior 5.2 mm, USS 6.0 mm, USS 5.0 mm). Bone mineral density (BMD) was determined by quantitative computed tomography (QCT). Failure in axial pullout was tested using a displacement-controlled universal test machine. USS II anterior 8.0 mm showed higher pullout strength than all other screws. The difference constituted a tendency (P = 0.108) when compared to USS II posterior 6.2 mm (+19%) and was significant in comparison to the other screws (+30 to +55%, P < 0.002). USS II posterior 6.2 mm showed significantly higher pullout strength than USS 5.0 mm (+30%, P = 0.014). The other screws did not differ significantly in pullout strength. Pullout strength correlated significantly with BMD (P = 0.0015) and vertebral body width/screw length (P < 0.001). The newly developed screws for spine surgery (USS II) show higher pullout strength when compared to established systems. Screw design had no significant influence on pullout force in vertebral body screws, but outer diameter of the screw, screw length and BMD are good predictors of pullout resistance.

Wahl, Dieter; Wild, Alexander; Krauspe, Rudiger; Schneider, Erich; Linke, Berend



The biomechanical consequences of rod reduction on pedicle screws: should it be avoided?  


BACKGROUND CONTEXT: Rod contouring is frequently required to allow for appropriate alignment of pedicle screw-rod constructs. When residual mismatch is still present, a rod persuasion device is often used to achieve further rod reduction. Despite its popularity and widespread use, the biomechanical consequences of this technique have not been evaluated. PURPOSE: To evaluate the biomechanical fixation strength of pedicle screws after attempted reduction of a rod-pedicle screw mismatch using a rod persuasion device. METHODS: Fifteen 3-level, human cadaveric thoracic specimens were prepared and scanned for bone mineral density. Osteoporotic (n=6) and normal (n=9) specimens were instrumented with 5.0-mm-diameter pedicle screws; for each pair of comparison level tested, the bilateral screws were equal in length, and the screw length was determined by the thoracic level and size of the vertebra (35 to 45 mm). Titanium 5.5-mm rods were contoured and secured to the pedicle screws at the proximal and distal levels. For the middle segment, the rod on the right side was intentionally contoured to create a 5-mm residual gap between the inner bushing of the pedicle screw and the rod. A rod persuasion device was then used to engage the setscrew. The left side served as a control with perfect screw/rod alignment. After 30 minutes, constructs were disassembled and vertebrae individually potted. The implants were pulled in-line with the screw axis with peak pullout strength (POS) measured in Newton (N). For the proximal and distal segments, pedicle screws on the right side were taken out and reinserted through the same trajectory to simulate screw depth adjustment as an alternative to rod reduction. RESULTS: Pedicle screws reduced to the rod generated a 48% lower mean POS (495±379 N) relative to the controls (954±237 N) (p<.05) and significantly decreased work energy to failure (p<.05). Nearly half (n=7) of the pedicle screws had failed during the reduction attempt with visible pullout of the screw. After reduction, decreased POS was observed in both normal (p<.05) and osteoporotic (p<.05) bone. Back out and reinsertion of the screw resulted in no significant difference in mean POS, stiffness, and work energy to failure (p>.05). CONCLUSIONS: In circumstances where a rod is not fully seated within the pedicle screw, the use of a rod persuasion device decreases the overall POS and work energy to failure of the screw or results in outright failure. Further rod contouring or correction of pedicle screw depth of insertion may be warranted to allow for appropriate alignment of the longitudinal rods. PMID:23769931

Paik, Haines; Kang, Daniel G; Lehman, Ronald A; Gaume, Rachel E; Ambati, Divya V; Dmitriev, Anton E



Jointness: A Selected Bibliography.  

National Technical Information Service (NTIS)

JDEIS is the Joint Doctrine, Education and Training Community Electronic Information System. It encompasses a searchable Joint Doctrine Database, a Joint Education section that includes the JPME Prospective Research Topics Database, as well as award-winni...

L. Garder



Knee Joint Laxity and Neuromuscular Characteristics of Male and Female Soccer and Basketball Players  

Microsoft Academic Search

Anterior cruciate ligament injuries are occurring at a higher rate in female athletes compared with their male counterparts. Research in the area of anterior cruciate ligament injury has increasingly focused on the role of joint proprioception and muscle activity in promoting knee joint stability. We measured knee joint laxity, joint kinesthesia, lower extremity balance, the amount of time required to

Susan L. Rozzi; Scott M. Lephart; William S. Gear; Freddie H. Fu



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)



Nonisothermal model of single screw extrusion of generalized Newtonian fluids  

SciTech Connect

A nonisothermal model of the single screw extrusion processing of generalized Newtonian fluids is presented. Various temperature dependent forms of a generalized Newtonian fluid constitutive equation representing the Herschel-Bulkley fluid and its simplifications, including Bingham plastic, power law of Ostwald-de Waele, and Newtonian fluids, are applicable. The model includes the generally ignored transverse convection terms of the equation of energy. The importance of keeping the transverse convection terms in the analysis is demonstrated by applying the model and comparing findings to experimental results involving the transverse flow temperature distributions in single screw extruders, available in the literature. The numerical instabilities, arising principally from the convection terms, generally encountered in high-Peclet-number extrusion flows, could be eliminated by the use of the streamline upwind/Petrov-Galerkin formulation. The model is sufficiently general to accommodate Navier's wall slip at the wall boundary condition commonly encountered during the processing of gels and concentrated suspensions.

Lawal, A.; Kalyon, D.M. (Stevens Inst. of Technology, Hoboken, NJ (United States). Highly Filled Materials Inst.)



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.



Release of elements from retrieved maxillofacial plates and screws.  


Vitallium appliances and surrounding tissues were investigated to evaluate the release and accumulation of elements. Four microplates, sixteen screws and surrounding tissues were removed from three patients presenting inflammation 4 to 6 years after surgery and were submitted to SEM and X-ray microprobe analysis. Histology was performed on paraffin or PMMA sections of tissues.A continuous release of elements from metallic appliances into soft tissues was observed. Cobalt, chromium, and nickel were detected in soft and boney tissues in close proximity to the appliance. Aluminium, as a component of screw coatings, accumulated in soft tissues, and a remarkable amount of aluminium was detected in the dense lamella of lamellar bone. The results suggest that coatings containing aluminium should be avoided and the time these appliances are allowed to remain in patients should be shortened. Further studies on element release and the fate of aluminium in bone are warranted. PMID:16167115

Bertoldi, C; Pradelli, J M; Consolo, U; Zaffe, D



Diffusion in a smectic liquid crystal with screw dislocations  

NASA Astrophysics Data System (ADS)

Screw dislocations provide barrier-free pathways that enhance interlayer diffusion in smectic liquid crystals and other layered materials. To explore this contribution to interlayer diffusion we study a ``random parking garage'' model in which a random walker can move between layers only by circling a dislocation core. We find that in such a layered system with a density of ? screw dislocations per unit area, with randomly chosen position, Burgers vector and phase, the ratio of interlayer to intralayer diffusion coefficients is D||/D?=(?b2/4?)ln R/a. Here b is the layer spacing, R is the layer radius, and a is the dislocation core size. Monte Carlo simulations are in agreement with this result. We discuss implications for both molecular simulation and experimental studies of diffusion in smectics.

Blumberg Selinger, Robin L.



Alternative technique of cement augmentation of loosened pedicle screws -- technical note and presentation of two cases.  


An alternative cement augmentation technique for pedicle screws is described, which was applied in two patients with mono- and bisegmental non-union after preceding multisegmental lumbar fusion. The correctly placed pedicle screws in S1 with diameters of 6 and 8.5 mm had severely enlarged the screw cavities due to segmental instability. Revision screws with 10 mm diameter demonstrated sufficient purchase only on the left side. Therefore, cement augmentation was performed for the right sided screws. After verification of intact pedicle borders, the cavity was filled up with PMMA bone cement. Afterwards, a Kirschner wire was positioned centrally, the hardening of the cement was awaited, the cement was gradually drilled and the screw was placed. In both patients, sufficient purchase of the cemented pedicle screws was documented. Screw insertion after awaiting the hardening of the bone cement in pedicles and vertebral bodies with huge defect situations seems to be an alternative to previous cement augmentation techniques of pedicle screws with the advantage, that the screws could be more easily unscrewed, if necessary. PMID:23452428

Kocak, T; Däxle, M; Reichel, H; Lattig, F



Management of odontoid fractures with percutaneous anterior odontoid screw fixation  

Microsoft Academic Search

Minimally invasive techniques have revolutionized the management of a variety of spinal disorders. The authors of this study\\u000a describe a new instrument and a percutaneous technique for anterior odontoid screw fixation, and evaluate its safety and efficacy\\u000a in the treatment of patients with odontoid fractures. Ten patients (6 males and 4 females) with odontoid fractures were treated\\u000a by percutaneous anterior

Yong-Long Chi; Xiang-Yang Wang; Hua-Zi Xu; Yan Lin; Qi-Shan Huang; Fang-Min Mao; Wen-Fei Ni; Sheng Wang; Li-Yang Dai



Cellulose and the twofold screw axis: modeling and experimental arguments  

Microsoft Academic Search

Crystallography indicates that molecules in crystalline cellulose either have twofold screw-axis (21) symmetry or closely approximate it, leading to short distances between H4 and H1? across the glycosidic linkage. Therefore,\\u000a modeling studies of cellobiose often show elevated energies for 21 structures, and experimental observations are often interpreted in terms of intramolecular strain. Also, some computer models\\u000a of cellulose crystallites have

Alfred D. French; Glenn P. Johnson



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



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



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



Suture suspension arthroplasty technique for basal joint arthritis reconstruction.  


Numerous techniques have been developed to address thumb basal joint arthritis. Many techniques include trapeziectomy with ligament reconstruction, most commonly performed by sacrificing a tendon that is used for ligament reconstruction and stabilization of the first metacarpal, with or without pin fixation. Harvesting a tendon for use in basal joint reconstruction is time-consuming and not without potential complications. Redirecting tendons via drill holes or anchoring tendons via suture anchors adds additional morbidity and time to the operative procedures. The authors introduce a novel technique of basal joint reconstruction, employing suture suspension for maintenance of joint arthroplasty space and stabilization of the base of the first metacarpal. PMID:19956040

DelSignore, Jeanne L; Accardi, Kimberly Z




SciTech Connect

The vulnerability of underground structures and openings in deep jointed rock to ground shock attack is of chief concern to military planning and security. Damage and/or loss of stability to a structure in jointed rock, often manifested as brittle failure and accompanied with block movement, can depend significantly on jointed properties, such as spacing, orientation, strength, and block character. We apply a hybrid Discrete Element Method combined with the Smooth Particle Hydrodynamics approach to simulate the MIGHTY NORTH event, a definitive high-explosive test performed on an aluminum lined cylindrical opening in jointed Salem limestone. Representing limestone with discrete elements having elastic-equivalence and explicit brittle tensile behavior and the liner as an elastic-plastic continuum provides good agreement with the experiment and damage obtained with finite-element simulations. Extending the approach to parameter variations shows damage is substantially altered by differences in joint geometry and liner properties.




Effect of Micrometer-Scale Roughness of the Surface of Ti6Al4V Pedicle Screws in Vitro and in Vivo  

PubMed Central

Background: Titanium implants that have been grit-blasted and acid-etched to produce a rough microtopography support more bone integration than do smooth-surfaced implants. In vitro studies have suggested that this is due to a stimulatory effect on osteoblasts. It is not known if grit-blasted and acid-etched Ti6Al4V implants also stimulate osteoblasts and increase bone formation clinically. In this study, we examined the effects of micrometer-scale-structured Ti6Al4V surfaces on cell responses in vitro and on tissue responses in vivo. Methods: Ti6Al4V disks were either machined to produce smooth surfaces with an average roughness (Ra) of 0.2 ?m or grit-blasted, resulting in an Ra of 2.0, 3.0, or 3.3 ?m. Human osteoblast-like cells were cultured on the disks and on tissue culture polystyrene. The cell number, markers of osteoblast differentiation, and levels of local factors in the conditioned media were determined at confluence. In addition, Ti6Al4V pedicle screws with smooth or rough surfaces were implanted into the L4 and L5 vertebrae of fifteen two-year-old sheep. Osteointegration was evaluated at twelve weeks with histomorphometry and on the basis of removal torque. Results: The cell numbers on the Ti6Al4V surfaces were lower than those on the tissue culture polystyrene; the effect was greatest on the roughest surface. The alkaline-phosphatase-specific activity of cell lysates was decreased in a surface-dependent manner, whereas osteocalcin, prostaglandin E2, transforming growth factor-?1, and osteoprotegerin levels were higher on the rough surfaces. Bone-implant contact was greater around the rough-surfaced Ti6Al4V screws, and the torque needed to remove the rough screws from the bone was more than twice that required to remove the smooth screws. Conclusions: Increased micrometer-scale surface roughness increases osteoblast differentiation and local factor production in vitro, which may contribute to increased bone formation and osteointegration in vivo. There was a correlation between in vitro and in vivo observations, indicating that the use of screws with rough surfaces will result in better bone-implant contact and implant stability. Clinical Relevance: The osteointegration of screws with rough microtopographies is likely to be better than that of screws with smoother surfaces.

Schwartz, Zvi; Raz, Perry; Zhao, Ge; Barak, Yael; Tauber, Michael; Yao, Hai; Boyan, Barbara D.



Mid-term results of hydroxyapatite-coated threaded cup implanted without supplementary supporting screws.  


We retrospectively reviewed the clinical, radiographic, and survivorship outcomes in a series of 180 patients that underwent 204 primary Total Hip Arthroplasties with the use of a second generation threaded hydroxyapatite-coated acetabular cup that was implanted without any supplementary supporting screws. At an average follow-up period of 10.2 (range: 8-14) years, one hundred and seventy-four patients (198 cups) were available for assessment. All patients underwent detailed physical and radiographic examination; their functional status was evaluated according to the Harris Hip Score (HHS). Following their digitization, all radiographs were further reviewed in order to determine the existence of any migration of the acetabular cup. Osteolytic lesions, radiolucent lines or zones of increased bone density were also recorded and classified according to the system of DeLee & Charnley. The modified Engh's criteria were used in order to evaluate the stability of the prosthesis. The patients' mean HHS at their latest follow-up visit (97.24 points) was statistically significantly better than the preoperative mean score of 40.31 points (p<0.001). Radiographic analysis showed "stable with bone ingrowth" fixation (modified Engh's criteria) of all implants with no significant migration of the cup (mean cranial migration: 0.597 mm, mean horizontal migration: 0.607 mm, mean observed difference of the cup's inclination angle: 0.26 degrees). No areas of significant osteolysis were found. The cumulative survival rate of the implants was 97.05%. Our results suggest that second generation hydroxyapatite-coated threaded acetabular cups can be successfully implanted (and achieve excellent results) without the use of any supplementary supporting screws. PMID:19462365

Trapotsis, Stergios J; Petsatodis, George E; Antonarakos, Petros D; Givissis, Panagiotis K; Christodoulou, Anastasios G; Pournaras, John D


Twin screw wet granulation: the study of a continuous twin screw granulator using Positron Emission Particle Tracking (PEPT) technique.  


In this paper, Positron Emission Particle Tracking (PEPT) techniques are utilised to track the trajectory of single particles through the mixing and conveying zones of a Twin Screw Granulator (TSG). A TSG consisting of conveying zones and mixing zones is used in this study. The mixing zones are arranged with kneading discs at an angle of 30°, 60° or 90°. Experiments were carried out using different mixing configurations with various screw speed and total mass flow rate. The PEPT data obtained were then utilised to obtain the residence time distribution (RTD) and the Peclet number in an attempt to gain some insight into the mixing of the process. The fill level of the granulator was also estimated to study the mechanism of granulation. As might be expected, it was shown that the residence time of the granulation process increases with decreasing screw speed. It also increases with increasing angle of the arrangement of kneading blocks in the mixing zones, but will decreases when powder feed rate is increased. The fill level of the mixing zone in particular increases when the screw speed decreases or when powder feed rate increases. Furthermore, the fill level of the granulator will increase when the mixing zone configuration changes from 30° to 90°. It is shown that the granulator is never fully filled, even using 90° mixer elements implying limited compaction which may explain why the granules produced are porous compared with those from a high shear mixer. Interestingly, the RTD analysis reveals that the extent of axial mixing in the mixing zone of the granulator does not change significantly for different configurations and process conditions. There is evidence of a tail in the RTD which implies some material hold up and channelling. PMID:22561951

Lee, Kai T; Ingram, Andy; Rowson, Neil A



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



Influence of moisture content and cooking on screw pressing of crambe seed  

Microsoft Academic Search

The cooking and drying conditions for oilseeds preparatory to screw pressing are some of the most important factors that influence\\u000a screw-press performance. Screw-press oil recovery, residual oil, pressing rate, and oil sediment content were measured for\\u000a uncooked crambe seed and crambe seed cooked at 100C for 10 min, pressed at six moisture contents ranging from 9.2 to 3.6%\\u000a dry basis.

K. K. Singh; D. P. Wiesenborn; K. Tostenson; N. Kangas



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:; 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)



Fatigue Fracture of Implant System Using TiN and WC Coated Abutment Screw  

Microsoft Academic Search

Dental implant systems are subject to failure in the screw connection part which can occur due to screw loosening or fracture. For solving the problem of loosening, some researchers had carried out the TiN(titanium nitride) and WC(tungsten carbide) coating on the abutment screw, while fatigue failure may still be not researched as an issue of coating materials. In this study,

H. C. Choe; C. H. Lee; Y. H. Jeong; Y. M. Ko; M. K. Son; C. H. Chung



Efficacy of computer-assisted pedicle screw insertion for cervical instability in RA patients  

Microsoft Academic Search

We evaluated the efficacy of the computer-assisted cervical pedicle screw insertion, compared with those inserted without\\u000a the help of the system on the cervix of rheumatoid arthritis (RA) patients. Eighty-six cervical pedicle screws were inserted\\u000a without the help of the system. Of the 86, 59 screws were in non-RA patients with degenerative spine, and 27 were in RA patients.\\u000a The

H. Ito; M. Neo; M. Yoshida; S. Fujibayashi; H. Yoshitomi; T. Nakamura



Morphometric trajectory analysis for the C2 crossing laminar screw technique  

Microsoft Academic Search

This paper reports a morphometric study of the C2 laminae to provide quantitative anatomical data for safe crossing laminar\\u000a screw placement. A valid trajectory is essential for C2 crossing laminar screw placement. Although several clinical technique\\u000a notes and modifications to define a safe screw trajectory have been introduced in the recent years, no morphometric analysis\\u000a has been performed to confirm

Bin Yue; Dai-Soon Kwak; Moon-Kyu Kim; Seong-Oh Kwon; Seung-Ho Han



Subaxial cervical pedicle screw insertion with newly defined entry point and trajectory: accuracy evaluation in cadavers  

Microsoft Academic Search

Successful placement of cervical pedicle screws requires accurate identification of both entry point and trajectory. However,\\u000a literature has not provided consistent recommendations regarding the direction of pedicle screw insertion and entry point\\u000a location. The objective of this study was to define a guideline regarding the optimal entry point and trajectory in placing\\u000a subaxial cervical pedicle screws and to evaluate the

Xiujun Zheng; Rahul Chaudhari; Chunhui Wu; Amir A. Mehbod; Ensor E. Transfeldt



Factors affecting the accurate placement of percutaneous pedicle screws during minimally invasive transforaminal lumbar interbody fusion  

Microsoft Academic Search

We retrospectively evaluated 488 percutaneous pedicle screws in 110 consecutive patients that had undergone minimally invasive\\u000a transforaminal lumbar interbody fusion (MITLIF) to determine the incidence of pedicle screw misplacement and its relevant\\u000a risk factors. Screw placements were classified based on postoperative computed tomographic findings as “correct”, “cortical\\u000a encroachment” or as “frank penetration”. Age, gender, body mass index, bone mineral density,

Moon-Chan Kim; Hung-Tae Chung; Jae-Lim Cho; Dong-Jun Kim; Nam-Su Chung


The original hole-in-one guide for atlantoaxial transarticular screw fixation  

Microsoft Academic Search

Atlantoaxial fusion by transarticular screw fixation provides firm fixation, and good results have been reported. However,\\u000a there are also problems, such as injury of the vertebral artery at the time of screw insertion. For accurate facet fusion,\\u000a we developed a new hole-in-one guide for screw fixation and obtained good results with its use. In 60 adult subjects, we measured\\u000a the

Yasuo Ito; Yasuhiro Hasegawa; Kazukiyo Toda; Masato Tanaka; Shinnosuke Nakahara



A new finger joint prosthesis.  


A new finger joint prosthesis is being developed for the proximal and distal interphalangeal positions. Currently available "joint spacer" prostheses provide relief from pain and cosmetic improvement, but relatively poor long-term function. The new prosthesis employs a mechanical hinge at the joint. It is fabricated from titanium alloy (6A14V). The hinge mechanism avoids direct metal to metal contact by using high density polyethylene bearings. In vitro tests of the hinge mechanism have passed 75 million cycles of continuous flexure without failure (n = 12). The hinge also incorporates a mechanical limit stop to prevent hyperextension. The hinge mechanism is enclosed in a sealed elastomeric jacket that isolates the hinge from connective tissue ingrowth. The jacket, equivalent to an artificial synovial membrane, has an integrally textured exterior surface designed to promote tissue attachment to the implant to stabilize tissue capsule formation around the joint. To test the in vivo efficacy of the new design, a series of 12 devices were implanted in the knee joint position of adult rabbits. A jacketed prosthesis was implanted on one side, whereas 2 weeks later an unjacketed control was implanted contralaterally. The animals then were maintained for an 8 week period. At sacrifice, the implants were removed, and the response of the surrounding tissues was studied histologically. At the time of implantation, the range of motion of the joints was approximately 100-105 degrees. There was a progressive loss in range of motion observed in both groups. The fibrous tissue capsule around the jacketed implants, however, was significantly reduced in thickness compared with the controls (mean thickness, 1.5 mm vs. 4.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8268583

Whalen, R L; Bowen, M A; Sarrasin, M J; Fukumura, F; Harasaki, H


Propulsive and maneuvering performance of two joints biorobotic autonomous undersea vehicle SPC-III  

Microsoft Academic Search

Biorobotic autonomous undersea vehicle SPC-III, developed by Robotics institute, BeiHang University, is a mission-scale autonomous submersible vehicle. The submersible vehicle possesses a torpedo-shape rigid hull. The aft section is a two joints caudal fin thruster driven by two servo motors, which may be substituted by a screw propeller maintaining the same body shape. The accurate motion of the caudal fin

Jianhong Liang; Weifeng Zheng; Li Wen; Tianmiao Wang; Chengyin Xie



Free-hand thoracic pedicle screws placed by neurosurgery residents: a CT analysis  

PubMed Central

Free-hand thoracic pedicle screw placement is becoming more prevalent within neurosurgery residency training programs. This technique implements anatomic landmarks and tactile palpation without fluoroscopy or navigation to place thoracic pedicle screws. Because this technique is performed by surgeons in training, we wished to analyze the rate at which these screws were properly placed by residents by retrospectively reviewing the accuracy of resident-placed free-hand thoracic pedicle screws using computed tomography imaging. A total of 268 resident-placed thoracic pedicle screws was analyzed using axial computed tomography by an independent attending neuroradiologist. Eighty-five percent of the screws were completely within the pedicle and that 15% of the screws violated the pedicle cortex. The majority of the breaches were lateral breaches between 2 and 4 mm (46%). There was no clinical evidence of neurovascular injury or injury to the esophagus. There were no re-operations for screw replacement. We concluded that under appropriate supervision, neurosurgery residents can safely place free-hand thoracic pedicle screws with an acceptable breach rate.

Wang, Vincent Y.; Chin, Cynthia T.; Lu, Daniel C.; Smith, Justin S.



Intramedullary tibial nailing in distal third tibial fractures: distal locking screws and fracture non-union.  


Distal third tibial fractures are prone to non-union following tibial nail insertion. The purpose of this study was to assess the union of distal third tibial fractures in patients who have undergone intra-medullary (IM) tibial nailing with one versus two distal locking screws. Sixty-five patients who had intramedullary tibial nail fixation were retrospectively analysed. Our results showed that 80% of non-unions in distal third fractures had only one distal locking screw compared to 20% who had two distal locking screws. This is statistically significant (p<0.01). We therefore conclude that two distal locking screws are essential for distal third fractures. PMID:17410364

Mohammed, Aso; Saravanan, Ramaswamy; Zammit, Jason; King, Richard



A Universal Pedicle Screw and V-Rod System for Lumbar Isthmic Spondylolysis: A Retrospective Analysis of 21 Cases  

PubMed Central

Objective To investigate the surgical outcome of a universal pedicle screw-V rod system and isthmic bone grafting for isthmic spondylolysis. Methods Twenty-four patients with isthmic spondylolysis at L5 and grade 0–I spondylolisthesis (Meyerding classification) received isthmic bone graft and stabilization using the universal pedicle screw-V rod system. Back pain was evaluated using the visual analog scale (VAS) and time to bone healing, improvement in spondylolisthesis and intervertebral space height at L5/S1 and L4/L5 were assessed. Results Twenty-one patients were followed up for 24 months and included in the analysis. Back pain was markedly improved at 3 months postoperatively with a statistical difference in VAS scores compared with preoperative VAS scores (P<0.001). The VAS scores were 0 to 3 at 6 months postoperatively in all patients and no back pain was reported in all patients except 2 patients who complained of back pain after prolonged sitting. X-ray examination showed a bone graft healing time of 3 to 12 months. Grade I spondylolisthesis improved to grade 0 in 4 patients and no noticeable change was observed in the remaining 17 cases. The intervertebral space height at L5/S1 was statistically increased (P<0.05) while no statistically significant change was seen at L4/L5. There was no statistically significant difference in the ROM of the intervertebral disks of L5/S1 and L4/5 before and after surgery. Conclusions The universal pedicle screw-V rod system and isthmic bone grafting directly repairs isthmic spondylolysis and reduces back pain, prevents anterior displacement of the diseased segment and maintains intervertebral space height, thus offering a promising alternative to current approaches for isthmic spondylolysis.

Chen, Xiong-sheng; Zhou, Sheng-yuan; Jia, Lian-shun; Gu, Xiao-min; Fang, Lei; Zhu, Wei



Fixation of lapidus arthrodesis with a plantar interfragmentary screw and medial locking plate: a report of 88 cases.  


Lapidus arthrodesis is a powerful procedure that can be used to correct pathologic features within the forefoot or midfoot. Many different methods of fixation for this procedure have been reported. The use of plating constructs has been shown to provide increased stability compared with screw-only constructs. The technique we have described consists of a plantar to dorsal retrograde lag screw across the arthrodesis site, coupled with a low-profile medial locking plate. A total of 88 consecutive patients were treated with this modification of the Lapidus procedure by 2 surgeons and were retrospectively evaluated. All patients followed an early postoperative weightbearing protocol. Patient age, gender, follow-up duration, interval to weightbearing and radiographic fusion, preoperative and postoperative intermetatarsal angle, hardware removal, preoperative and postoperative American Orthopaedic Foot and Ankle Society midfoot scores, and adjunct procedures were analyzed. The mean follow-up period was 16.76 ± 5.9 (range 12 to 36) months, and all healed fusions demonstrated radiographic union at a mean of 51 ± 19.1 (range 40 to 89) days. The patients were treated with weightbearing starting a mean of 10.90 ± 4.1 (range 5 to 28) days postoperatively. Complications included 15 patients (17%) requiring hardware removal, 2 cases (2%) of hallux varus, 6 cases (7%) of radiographic recurrent hallux valgus, and 2 patients (2%) with first metatarsocuneiform nonunion. The results of the present study have demonstrated that plantar lag screw fixation with medial locking plate augmentation for Lapidus arthrodesis allows for early weightbearing with satisfactory outcomes, improved clinical and radiographic alignment, and improved American Orthopaedic Foot and Ankle Society scores. PMID:23540755

Cottom, James M; Vora, Anand M



Average depth of tarsometatarsal joint for trephine arthrodesis.  


The trephine arthrodesis technique has been shown to be an effective method for various foot and ankle fusion procedures, with acceptable rates of fusion reported. The tarsometatarsal joints are an excellent example for this procedure because of the joint shape and soft tissue stability. The success of this procedure depends on many factors, but a large consideration is adequate joint resection. A cadaveric study to examine the joint depth of the Lisfranc complex was undertaken, allowing for improved understanding of the resection needed to maintain a stable plantar cortex while removing all apposing joint surfaces. A statistical analysis was then performed to determine the significance of the joint depth to available demographic data. A total of 51 limbs were evaluated for the depth of the first, second, and third metatarsal-cuneiform joints. The average joint depth for the first through third metatarsal-cuneiform joints was 32.3, 26.9, and 23.6 mm, respectively. The plantar cortex depth was less than 2 mm for the first through third metatarsal-cuneiform joints. The correlation between the length of the foot and the joint depth was statistically significant. Subgroups stratified by shoe size were analyzed for differences in joint size and were also statistically significant. A better understanding of the tarsometatarsal joint anatomy would benefit the trephine technique for Lisfranc arthrodesis. PMID:22192856

Ryan, Jay D; Timpano, Eugene D; Brosky, Thomas A



Dynamic condylar screw as a solution to operative dilemma in early sub-trochanteric fracture following cannulated screw fixation for slipped capital femoral epiphysis: a case report.  


A 14-year-old boy presented with a 2-month history of left groin pain and a limp on the left side. Radiographs confirmed slipped capital femoral epiphysis (SCFE) of the left hip. The surgical procedure he received used a single, 8-mm, partially threaded, cannulated screw. Postoperatively he was advised to remain strictly non-weight bearing on the affected lower limb until physeal closure was achieved. Unfortunately, he fell down 4 weeks postoperatively and sustained a subtrochanteric fracture on the same hip, with the cannulated screw still in place. This injury was surgically treated using a dynamic condylar screw and a side plate. PMID:23016786

Sidaginamale, Raghavendra Prasad; Fadero, P; Apostolopoulos, Alexandros P; Zolcze, L



Feasibility of Intra-operative Computed Tomography Navigation System for Pedicle Screw Insertion of the Thoraco-lumbar Spine.  


STUDY DESIGN:: A retrospective analysis of feasibility of intraoperative computed tomography (iCT) navigation for pedicle screw insertion of the thoraco-lumbar spine OBJECTIVES:: This study assessed the feasibility of an iCT navigation system by evaluating the screw insertion time, screw revision time, and learning curve of the iCT surgical team in patients who underwent thoraco-lumbar pedicle screw surgery using this navigation system. SUMMARY OF BACKGROUND DATA:: The iCT navigation system has been reported to improve the accuracy and safety of pedicle screw insertion. However, the assessment of the feasibility of spinal instrumentation guided by iCT navigation system is limited. METHODS:: From the time iCT navigation system was set-up to a period covering 16 months, consecutive patients who underwent thoracic or lumbar spinal pedicle screw surgery were enrolled. The screw insertion and screw revision times were estimated using the system's automatic time recording between the intra-operative CT scans. The insertion time per screw of the first 50 patients not requiring screw revision was also analyzed to evaluate the learning curve of the iCT surgical team. RESULTS:: There were 178 patients with a total of 932 pedicle screws. The cortical breach rate was 3.2% and the screw revision rate was 1.4%. The insertion time per screw was 10.2±6.3?min and the screw revision time was 13.8±9.9?min. The learning curve of the iCT surgical team for pedicle screw insertion guided by this navigation system was not steep and experience from less than 10 patients was adequate to provide familiarity with this system. CONCLUSION:: The iCT navigation system is clinically feasible for thoraco-lumbar pedicle screw surgery. It provides high-level safety and accuracy, as well as ease of screw revision when required. PMID:23222100

Lee, Ming-Hsueh; Lin, Martin Hsiu-Chu; Weng, Hsu-Huei; Cheng, Wan-Chun; Tsai, Yuan-Hsiung; Wang, Ting-Chung; Yang, Jen-Tsung



Mechanical performance of standard and cannulated 4.0-mm cancellous bone screws.  


The mechanical performance of bone screws is determined by their pull-out strength (holding power), compressive force, stripping torque, yield bending moment, ultimate bending moment, and fatigue strength. These parameters are related to the parameters of the screw design, including major thread diameter, minor thread diameter, thread length, pitch, shaft diameter, cannulation diameter, and material properties. The goal of the study was to theoretically predict the static performance of five 4.0-mm, 45-46-mm-long, cancellous, partially threaded standard and cannulated bone screws and compare the predictions with experimental measurements. A secondary goal was to determine if cannulation of the bone screw diminished its mechanical performance. The predicted values for pull-out force, compressive force, and stripping torque were determined by the thread length, major thread diameter, and thread shape factor. The screws with the largest major thread diameter and longest thread length had the greatest pull-out force, compressive strength, and stripping torque. However, when correcting for the thread length, a higher thread shape factor compensated for a smaller major diameter. The coefficient of determination (r2) for the correlation between the predicted and measured pull-out force improved from 0.75 to 0.90 when the theoretical model included the thread shape factor. The yield and ultimate bending moments are a function of the section modulus and material properties of the screw. The Ace solid screw had the greatest section modulus and yield and ultimate bending moments. The experimental data support the theoretical models for predicting the mechanical performance of bone screws. The design of the bone screws can be optimized on the basis of theoretical modeling. The strong correlation between the predicted and measured parameters allows comparison between bone screws without repeated experimental tests. Theoretical and experimental results show that cannulation of the bone screw did not inherently diminish its mechanical performance. PMID:10815833

Brown, G A; McCarthy, T; Bourgeault, C A; Callahan, D J



Comparison of success rates of orthodontic mini-screws by the insertion method  

PubMed Central

Objective The aim of this study was to compare the success rates of the manual and motor-driven mini-screw insertion methods according to age, gender, length of mini-screws, and insertion sites. Methods We retrospectively reviewed 429 orthodontic mini-screw placements in 286 patients (102 in men and 327 in women) between 2005 and 2010 at private practice. Age, gender, mini-screw length, and insertion site were cross-tabulated against the insertion methods. The Cochran-Mantel-Haenszel test was performed to compare the success rates of the 2 insertion methods. Results The motor-driven method was used for 228 mini-screws and the manual method for the remaining 201 mini-screws. The success rates were similar in both men and women irrespective of the insertion method used. With respect to mini-screw length, no difference in success rates was found between motor and hand drivers for the 6-mm-long mini-screws (68.1% and 69.5% with the engine driver and hand driver, respectively). However, the 8-mm-long mini-screws exhibited significantly higher success rates (90.4%, p < 0.01) than did the 6-mm-long mini-screws when placed with the engine driver. The overall success rate was also significantly higher in the maxilla (p < 0.05) when the engine driver was used. Success rates were similar among all age groups regardless of the insertion method used. Conclusions Taken together, the motor-driven insertion method can be helpful to get a higher success rate of orthodontic mini-screw placement.

Kim, Jung Suk; Choi, Seong Hwan; Cha, Sang Kwon; Kim, Jang Han; Lee, Hwa Jin; Yeom, Sang Seon



Helical rotary screw expanders to generate electricity from geothermal brines  

SciTech Connect

A 1-megawatt, self-contained, helical rotary screw expander power plant to generate electricity of a geothermal brine wellhead was evaluated. The test support equipment, including a computer-controlled data system, an instrumentation and control van, and a 1000-kilowatt, variable bank were investigated. It was stated that the power was technically feasible although it operated at only about 45% average efficiency. Its technology transfer testing program involved Mexico, Italy, and New Zealand. The mineral laden geothermal brines of Mexico are more prone to scale formation than the Utah brine, and the power plant showed an increase in efficiency to a maximum of 62%.

Not Available



Oral Extrusion of Screw after Anterior Cervical Interbody Fusion  

PubMed Central

We present a case of delayed oral extrusion of a screw after anterior cervical interbody fusion in a 68-year-old man with osteoporosis. Fifteen months earlier, he had undergone C5 corpectomy and anterior cervical interbody fusion at C4-6 for multiple spinal stenoses. The patient was nearly asymptomatic, except for a foreign body sensation in his throat. We conclude that the use of a mesh graft or other instrument in elderly patients and those with osteoporosis or problematic bone quality should be considered carefully and that if surgery were to be performed, periodic postoperative follow-up evaluations are mandatory.

Lee, Jin Soo; Hwang, Soo Hyun; Han, Jong Woo



Oral extrusion of screw after anterior cervical interbody fusion.  


We present a case of delayed oral extrusion of a screw after anterior cervical interbody fusion in a 68-year-old man with osteoporosis. Fifteen months earlier, he had undergone C5 corpectomy and anterior cervical interbody fusion at C4-6 for multiple spinal stenoses. The patient was nearly asymptomatic, except for a foreign body sensation in his throat. We conclude that the use of a mesh graft or other instrument in elderly patients and those with osteoporosis or problematic bone quality should be considered carefully and that if surgery were to be performed, periodic postoperative follow-up evaluations are mandatory. PMID:19096688

Lee, Jin Soo; Kang, Dong-Ho; Hwang, Soo Hyun; Han, Jong Woo



Lapidus bunionectomy: arthrodesis of the first metatarsocunieform joint.  


Fusion of the first metatarsocunieform (MC) joint allows for correction of the first metatarsal in three planes, including adduction, plantarflexion, and rotation. It also allows for decreased jamming of the great toe joint and increased medial column stability. As knowledge about other medial column procedures grows, fusion of the first MC joint will continue to grow in popularity. It is an excellent procedure for hallux limitus and also for metatarsus primus elevatus cases. PMID:15012034

Baravarian, Babak; Briskin, Gary B; Burns, Patrick



Rigid and flexible spinal stabilization devices: A biomechanical comparison  

Microsoft Academic Search

The surgical devices for the treatment of degenerative disc disease are based on different concepts (rods for spine fusion, ROM-restricting or load-bearing devices for dynamic stabilization). In the present work, the effects of some stabilization systems on the biomechanics of the lumbar spine were investigated by means of a finite element model of the L2–L5 spine segment. Pedicular screws and

Fabio Galbusera; Chiara Maria Bellini; Federica Anasetti; Cristina Ciavarro; Alessio Lovi; Marco Brayda-Bruno



Relationship of Kinetic Demands of Sports and Knee Joint Laxity  

Microsoft Academic Search

The stability of the knee joint is crucial when playing most sport. Understanding the factors that increase the strength of the knee, especially the anterior cruciate ligament (ACL), is important to prevent knee injuries and improve treatment. Studying different sports, which place different demands on the knee joint, also helps us understand which exercises are most likely to strengthen the

Simon Yeung; Murray Maitland


A simple PD controller for robots with elastic joints  

Microsoft Academic Search

The point-to-point control of manipulators having elastic joints is considered. It is shown that a simple PD (proportional plus derivative) controller, similar to that used for rigid robots, suffices to globally stabilize the elastic joint robots about a reference position. A robustness analysis is also given with respect to uncertainties on the robot parameters. The results of numerical simulation tests

P. Tomei



Acromioclavicular joint instability—reconstruction indications and techniques  

Microsoft Academic Search

Injuries to the acromioclavicular joint are common and may lead to instability or degenerative changes requiring surgical intervention. The spectrum of injury ranges from sprain to disruption of the acromioclavicular and coracoclavicular ligaments, which provide horizontal and vertical stability to the distal clavicle. Most injuries are the result of direct trauma to the acromioclavicular joint. The majority of injuries can

Brent A Ponce; Peter J Millett; Jon J. P Warner



Joint Injection/Aspiration  


... osteoarthritis. What usually is injected into the joint space? Corticosteroids (such as methylprednisolone and triamcinolone formulated to ... for producing inflammation and pain within the joint space. Although corticosteroids may also be successfully used in ...


Arthritis: Metacarpophalangeal (MP) Joint  


... activities. Arthritis is the wearing away of the cartilage at a joint. Cartilage is the coating layer of tissue on the ... that acts as a shock-absorber. Loss of cartilage can lead to joint destruction and a shift ...


Large displacement spherical joint  


A new class of spherical joints has a very large accessible full cone angle, a property which is beneficial for a wide range of applications. Despite the large cone angles, these joints move freely without singularities.

Bieg, Lothar F. (Albuquerque, NM); Benavides, Gilbert L. (Albuquerque, NM)



Surgical Outcomes and Complications after Occipito-Cervical Fusion Using the Screw-Rod System in Craniocervical Instability  

PubMed Central

Objective Although there is no consensus on the ideal treatment of the craniocervical instability, biomechanical stabilization and bone fusion can be induced through occipito-cervical fusion (OCF). The authors conducted this study to evaluate efficacy of OCF, as well as to explore methods in reducing complications. Methods A total of 16 cases with craniocervical instability underwent OCF since the year 2002. The mean age of the patients was 51.5 years with a mean follow-up period of 34.9 months. The subjects were compared using lateral X-ray taken before the operation, after the operation, and during last follow-up. The Nurick score was used to assess neurological function pre and postoperatively. Results All patients showed improvements in myelopathic symptoms after the operation. The mean preoperative Nurick score was 3.1. At the end of follow-up after surgery, the mean Nurick score was 2.0. After surgery, most patients' posterior occipito-cervical angle entered the normal range as the pre operation angle decresed from 121 to 114 degree. There were three cases with complications, such as, vertebral artery injury, occipital screw failure and wound infection. In two cases with cerebral palsy, occipital screw failures occurred. But, reoperation was performed in one case. Conclusion OCF is an effective method in treating craniocervical instability. However, the complication rate can be quite high when performing OCF in patients with cerebral palsy, rheumatoid arthritis. Much precaution should be taken when performing this procedure on high risk patients.

Choi, Sung Ho; Park, Chan Woo; Kim, Woo Kyung; Yoo, Chan Jong; Son, Seong



Arthroscopically assisted coracoclavicular ligament reconstruction for chronic acromioclavicular joint instability  

Microsoft Academic Search

The treatment of symptomatic chronic acromioclavicular joint dislocations can be challenging. Different surgical procedures\\u000a have been described in the literature. We present an arthroscopically assisted stabilization using a gracilis tendon transclavicular-transcoracoid\\u000a loop technique augmented with a Tight-Rope (Arthrex, Naples, FL, USA). In contrast to the classic Weaver–Dunn procedures this\\u000a technique is designed to stabilize the acromioclavicular joint by recreating the

Markus Scheibel; Adeleke Ifesanya; Stephan Pauly; Norbert P. Haas



16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame...  

Code of Federal Regulations, 2013 CFR

...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment 6 Figure 6 to Part 1633 Commercial Practices...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment...



16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame...  

Code of Federal Regulations, 2010 CFR

... false Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment...Part 1633âBurner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame Allowing Burner Height...



16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame...  

Code of Federal Regulations, 2010 CFR

... false Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment...Part 1633âBurner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame Allowing Burner Height...



Rotator cuff repair with bioabsorbable screws: An in vivo and ex vivo investigation  

Microsoft Academic Search

Purpose: The purpose of this study was to evaluate in vivo the clinical outcomes of rotator cuff repairs with bioabsorbable screws compared with metal suture anchors, and to compare the ex vivo initial load to failure of rotator cuff repairs using 3 different bioabsorbable screws, suture anchors, and transosseous sutures. Type of Study: In vivo clinical outcomes investigation, and ex

Craig A. Cummins; Sabrina Strickland; Richard C. Appleyard; Zoltan L. Szomor; Jeanette Marshall; George A. C. Murrell



Application of screw theory to motion analysis of assemblies of rigid parts  

Microsoft Academic Search

Screw theory is well known to do kinematic computations. Recently it has been used to create kinematic models of assembly features so allowing assembly analysis. Motion limit analysis uses the mathematics of screw theory to model the ability of mechanical assembly features to allow or constrain rigid body motions in six degrees of freedom. A user of this theory is

Jeffrey D. Adams; Salvatore Gerbino; Daniel E. Whitney



Anatomic considerations of the second sacral vertebra and dorsal screw placement  

Microsoft Academic Search

Direct measurements and measurements from images of axial cross-sections on 20 cadaveric sacra that had been scanned on computer were used in this study. The measurements, including parameters from the vertebral body, lateral mass and spinal canal of the second sacral vertebra (S2) were performed. The length of the screw path and the optimal angulation of the screw placement for

N. A. Ebraheim; J. Lu; H. Yang; B. E. Heck; R. A. Yeasting



Anatomic considerations of the second sacral vertebra and dorsal screw placement  

Microsoft Academic Search

Summary Direct measurements and measurements from images of axial cross-sections on 20 cadaveric sacra that had been scanned on computer were used in this study. The measurements, including parameters from the vertebral body, lateral mass and spinal canal of the second sacral vertebra (S2) were performed. The length of the screw path and the optimal angulation of the screw placement

N. A. Ebraheim; J. Lu; H. Yang; B. E. Heck; R. A. Yeasting



The effect of Dirac phase on acoustic vortex in media with screw dislocation  

NASA Astrophysics Data System (ADS)

We study acoustic vortex in media with screw dislocation using the Katanaev–Volovich theory of defects. It is shown that the screw dislocation affects the beam's orbital angular momentum and changes the acoustic vortex strength. This change is a manifestation of topological Dirac phase and is robust against fluctuations in the system.

Torabi, Reza; Rezaei, Zahra



Posterior interbody fusion using a diagonal cage with unilateral transpedicular screw fixation for lumbar stenosis  

Microsoft Academic Search

Few reports have described the combined use of unilateral pedicle screw fixation and interbody fusion for lumbar stenosis. We retrospectively reviewed 79 patients with lumbar stenosis. The rationale and effectiveness of unilateral pedicle screw fixation were studied from biomechanical and clinical perspectives, aiming to reduce stiffness of the implant. All patients were operated with posterior interbody fusion using a diagonal

Jian Zhao; Feng Zhang; Xiaoqing Chen; Yu Yao



Treatment of neuromuscular scoliosis with posterior-only pedicle screw fixation  

Microsoft Academic Search

BACKGROUND: To determine whether posterior-only approach using pedicle screws in neuromuscular scoliosis population adequately addresses the correction of scoliosis and maintains the correction over time. METHODS: Between 2003 and 2006, 26 consecutive patients (7 cerebral palsy, 10 Duchenne muscular dystrophy, 5 spinal muscular atrophy and 4 others) with neuromuscular scoliosis underwent posterior pedicle screw fixation for the deformity. Preoperative, immediate

Hitesh N Modi; Seung-Woo Suh; Hae-Ryong Song; Harry M Fernandez; Jae-Hyuk Yang



A method for restoring facially inclined implants with a screw-retained restoration.  


Cement-retained implant restorations have 2 major disadvantages: they have a submucosal cement line and the prosthesis is difficult to retrieve. Although a screw-retained implant restoration negates both of these concerns, anatomic limitations can hinder its use. This article describes a simple technique for restoring a buccally inclined dental implant with a screw-retained restoration. PMID:23566609

Takanashi, Kazunari; Lee, Joung Min; Sedler, Anatoly; Aalam, Alina Krivitsky



On the Vertical Screw Conveyor for Non-Cohesive Bulk Materials.  

National Technical Information Service (NTIS)

The behavior of non-cohesive bulk materials is studied in order to find a pressure distribution that can be used for calcualtion of vertical screw conveyors. A new calculation method for vertical screw conveyors is presented. Regard is paid to the larger ...

L. G. Nilsson



Stress analysis of the distal locking screws for femoral interlocking nailing  

Microsoft Academic Search

In femoral locked nailing, the distal locking screws are vulnerable to mechanical failure. Biomechanical studies have shown that the stress on these screws is substantially affected by the fit of the nail in the medullary canal. In this study, a “closed form” mathematical model based on elastic beam-column theory was developed to investigate how the nail–cortical contact, which was simulated

Jinn Lin; Son-Jyh Lin; Po-Quang Chen; Shu-Hua Yang



Albert Baldwin Wood, the Screw Pump, and the Modernization of New Orleans  

Microsoft Academic Search

Albert Baldwin Wood and his screw pumps modernized New Orleans by bringing flood-free streets and cleaner water to the city while providing the potential for growth by pumping swamp lands dry. While Wood was never part of the local Progressive movement, his work with the pumps fit with Progressive initiatives for modernization. At first, the screw pumps removed rain water

Nicole Romagossa



Wave analysis of implant screw loosening using an air cylindrical cyclic loading device  

Microsoft Academic Search

Statement of Problem. The mechanics of implant screw loosening or fracture are well understood in the field of engineering. They have not been as widely explored in dentistry. Purpose. This study investigated the effects of simulated mastication on implant components and used wave analysis to document the basic mechanisms of screw loosening in a simulated oral environment. Material and Methods.

Juneseok Lee; Yung-Soo Kim; Chang-Whe Kim; Jung-Suk Han



Interference Screw vs. Suture Anchor Fixation for Open Subpectoral Biceps Tenodesis: Does it Matter?  

Microsoft Academic Search

BACKGROUND: Bioabsorbable interference screw fixation has superior biomechanical properties compared to suture anchor fixation for biceps tenodesis. However, it is unknown whether fixation technique influences clinical results. HYPOTHESIS: We hypothesize that subpectoral interference screw fixation offers relevant clinical advantages over suture anchor fixation for biceps tenodesis. STUDY DESIGN: Case Series. METHODS: We performed a retrospective review of a consecutive series

Peter J Millett; Brett Sanders; Reuben Gobezie; Sepp Braun; Jon JP Warner



Slipped capital femoral epiphysis screw removal: complications and survey of attitudes of adult hip surgeons  

Microsoft Academic Search

We have reviewed the complication rate over a ten year period for removal of screws placed for slipped capital femoral epiphysis ({SCFE}) and have surveyed the views of orthopaedic surgeons with an adult hip practice in Scotland on leaving the metalwork in situ. Whilst screw removal is favoured by many orthopaedic surgeons, a recent review of the literature reported that

E. Oburu; D. Macdonald; N. I. L. Wilson



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

Code of Federal Regulations, 2010 CFR

...Labor 8 2010-07-01 2010-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section...CONSTRUCTION Tools-Hand and Power § 1926.305 Jacksâlever and ratchet, screw, and hydraulic. (a) General...



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

Code of Federal Regulations, 2010 CFR

...Labor 8 2009-07-01 2009-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section...CONSTRUCTION Tools-Hand and Power § 1926.305 Jacksâlever and ratchet, screw, and hydraulic. (a) General...



Development of Solid-Lubricated Ball-Screws for Use in Space.  

National Technical Information Service (NTIS)

Ball-screws lubricated by solid lubricant films containing molybdenum disulphide are developed. The ball-screws (shaft diameter: phi 25 mm, length: 667 mm) were operated under a load of 40 to 120 N at a speed of 1.5 to 200 rpm at 10(exp -5) Pa. First, bal...

M. Chiba T. Gyougi M. Nishimura K. Seki



What Every Member of the Trade Community Should Know About: Distinguishing Bolts from Screws.  

National Technical Information Service (NTIS)

Steel Screws and bolts are classified in Chapter 73, Harmonized Tariff Schedule of the United States (HTSUS) under heading 7318. The tariff has separate provisions for the different types of screws and bolts, and separate provisions for threaded and non-t...



Severe cartilage damage by broken poly– L –lactic acid (PLLA) interference screw after ACL reconstruction  

Microsoft Academic Search

Poly–L–lactic acid (PLLA) bioabsorbable interference screws are widely used for fixation of tendon to bone and bone to bone in anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstructions. Complications are rare. To our knowledge this is the first report of severe chondral damage caused by late breakage of the screw. Breakage of bioscrews has only been published in

Burkhard Lembeck; Nikolaus Wülker



Experimental study of friction in aluminium bolted joints  

NASA Astrophysics Data System (ADS)

This study aims at developing an experimental tool useful to define accurately the friction coefficients in bolted joints and, therefore, at relating precisely the tightening torque to the bolt preloading force in some special components used in front motorbike suspensions. The components under investigation are some clamped joints made of aluminium alloy. The preloading force is achieved by applying a torque wrench to the bolt head. Some specific specimens have been appropriately designed and realized in order to study the tribological aspects of the tightening phase. Experimental tests have been performed by applying the Design of Experiment (DOE) method in order to obtain a mathematical model for the friction coefficients. Three replicas of a full factorial DOE at two levels for each variable have been carried out. The levels include cast versus forged aluminium alloy, anodized versus spray-painted surface, lubricated versus unlubricated screw, and first tightening (fresh unspoiled surfaces) versus sixth tightening (spoiled surfaces). The study considers M8x1.25 8.8 galvanized screws.

Croccolo, D.; de Agostinis, M.; Vincenzi, N.



Effectiveness of interference screw fixation in ulnar collateral ligament reconstruction.  


Ulnar collateral ligament disruptions of the elbow are increasingly common for athletes involved in overhead sports. One newer reconstructive technique combines the use of a biotenodesis screw for ulnar fixation with the docking procedure for humeral fixation referred to as the DANE procedure. Biomechanical evaluations have determined that the combined procedure has properties similar to previous methods, but few comparative clinical studies have been performed. The current study compares the DANE procedure to a traditional method of ulnar collateral ligament reconstruction with a medium range follow-up. Twelve ulnar collateral ligament reconstructions were observed for a minimum of 21 months. Six reconstructions were performed using bone tunnels on the ulna. The other 6 used a biotenodesis interference screw on the ulna. Both groups used the docking procedure on the humerus. Identical rehabilitation phases were followed by both groups. Attention was paid not only to the time to return to play and the level able to be returned to but also to interoperative differences, including tourniquet time. We concluded that the DANE reconstruction is an appropriate and effective method. Results are similar to those achieved with a traditional reconstructive method. The study also demonstrates that tourniquet time and, therefore, operative time is less for the DANE procedure. PMID:19292392

Nissen, Carl W



Molecular dynamics studies of the dissociated screw dislocation in silicon  

NASA Astrophysics Data System (ADS)

Characterizing the motion of dislocations through covalent, high Peierls barrier materials is a key problem in materials science, while despite the progress in experimental studies the actual observation of the atomistic behaviour involved in core migration remains limited. We have applied a hybrid embedding scheme to investigate the dissociated screw dislocation in silicon, consisting of two 30° partials separated by a stacking fault ribbon, under the influence of a constant external strain. Our 'learn on the fly' hybrid technique allows us to calculate the forces on atoms in the vicinity of the core region using the tight binding Kwon potential, whilst the remainder of the bulk matrix is treated within a classical approximation. Applying a 5% strain to the dissociated screw dislocation, for a simulation time of 100 ps at a temperature of 600 K, we observe movement of the partials through two different mechanisms: double kink formation and square ring diffusion at the core. Our results suggest that in these conditions, the role of solitons or anti-phase defects in seeding kink formation and subsequent migration is an important one, which should be taken into account in future studies.

Choudhury, R.; Gattinoni, C.; Makov, G.; De Vita, A.



Collapsible mechanical joint  

NASA Astrophysics Data System (ADS)

A mechanical joint that can be configured to be either flexible or rigid is presented. The mechanical joint comprises three members which are flexibly attached to each other with a cable. When the cable is tightened, the three members come together to form a rigid joint capable of withstanding structural loads.

Robertson, Glen A.



Bolted Hybrid Joints.  

National Technical Information Service (NTIS)

The report presents the results of an analytical study of hybrid steel butt joints of A36, A440 and A514 steel. The joints were fastened by either A325 or A490 bolts. The studies were designed to determine the effect of various variables on the joint stre...

R. Kormanik J. W. Fisher



Misplacement Pattern of Pedicle Screws in Pediatric Patients with Spinal Deformity: A Computed Tomography Study.  


STUDY DESIGN:: A retrospective study. OBJECTIVE:: To assess the accuracy and safety of the placement of pedicle screws on pediatric patients with congenital scoliosis younger than 10 years old through post-operative CT scanning. SUMMARY OF BACKGROUND DATA:: The accuracy of the placement of pedicle screws in adolescent and adult population with various spinal problems has been thoroughly studied. As to pediatric patients with congenital scoliosis, the related studies were inadequate. METHODS:: A retrospective review on 96 pediatric patients with congenital scoliosis younger than 10 years old who received posterior instrumentation from February 2006 to June 2012. Postoperative CT scan was utilized to assess the accuracy of pedicle screw placement. Pedicle perforations were classified as medial or lateral or anterior and categorized into one of four grades: Grade 1?2 mm, Grade 2 2.1-4.0 mm, Grade 3 4.1-6.0 mm, Grade 4?6.1 mm. The positions of screws were also classified as acceptable (fully contained screws or with screws either ?2 mm of medial wall perforation or ?6 mm of lateral wall perforation and without impingement of visceral organs) or unacceptable. The variables of pedicle screw position as defined by fully contained were statistically examined using Fisher (two-tailed) exact test with regard to: (1) side of curvature (convex or concave); (2) region (thoracic or lumbar); (3) magnitude of curvature (<80° or ?80°); (4) apical region and overall; (5) deformed vertebrae versus normal vertebrae. RESULTS:: A total of 625 screws were inserted, 512 screws (81.9%) were fully contained within the cortical boundaries of the pedicle. 569 (91.0%) screws were regarded as acceptably positioned while 56 (9.0%) as unacceptably positioned. 317 screws were inserted in thoracic spine, and 67 (21.1%) perforations occurred while 308 screws in lumbar spine, and 46 (14.9%) perforated. The breach rate was found higher in thoracic spine than in lumbar spine (P<0.05). 306 screws were inserted on the concave side of the curve, and 50 (16.3%) perforations occurred while 319 on the convex side. 63 (19.7%) perforations occurred. There is no difference with regard to the breach rates between the concave side and the convex side of the curve (P>0.05). 328 screws were inserted in patients with the Cobb angle <80°, and 41 (12.5%) screws perforated the pedicles while 297 in the patients with the Cobb angle > 80°, and 72 (24.2%) screws perforated pedicles. the breach rate was higher in the patients with the Cobb angle > 80° than in the patients with the Cobb angle <80° (P<0.05). 154 screws were inserted in the apical vertebrae, and 57 (37.1%) screws perforated the pedicle walls. The breach rate in apical vertebrae was higher than overall (55/154 VS. 113/625) (P<0.05). 252 screws were inserted in the deformed vertebrae, and 58 (23.0%) perforated the pedicle walls. 373 screws were inserted in normal vertebrae, and 55 (14.7%) perforated the pedicle walls. The breach rate in the deformed vertebrae was higher than in normal vertebrae (P<0.05). CONCLUSION:: PSs insertion in pediatric patients with congenital scoliosis was less accurate than that in adult patients. However, the safety of placement was quite satisfactory. The possibility of pedicle breaching increased when placing PSs at deformed vertebra, on the apex of the curve and in the thoracic spine, which reminds surgeons to be more cautious when placing PSs in these regions. PMID:23563329

Zhu, Feng; Sun, Xu; Qiao, Jun; Ding, Yitao; Zhang, Bing; Qiu, Yong



Guidewire Breakage: An Unusual Complication of Anterior Odontoid Cannulated Screw Fixation  

PubMed Central

The preferred treatment of a type II odontoid fracture is anterior odontoid screw fixation to preserve the cervical spine range of movement. This case report describes an unusual complication of guidewire breakage during anterior odontoid cannulated screw fixation for a 52-year-old patient who presented with a type II odontoid fracture after a motor vehicle accident. The distal segment of the guidewire was bent over the tip of the cannulated odontoid screw and broke off during guidewire withdrawal. The three months follow-up computed tomography examination of the cervical spine showed acceptable screw placement, good odontoid process alignment with incomplete fusion, and no migration of the fractured segment of the guidewire. It is recommended that the guidewire be withdrawn once the cannulated screw is passed through the fractured site into the odontoid process and a new guidewire be used in each surgical procedure instead of been reused to avoid metal stress fatigue that can result in easy breakage.

Bin-Nafisah, Sharaf; Almusrea, Khaled; Alfawareh, Mohamed



Role of the O-arm and Computer-assisted Navigation of Safe Screw Fixation in Children with Traumatic Rotatory Atlantoaxial Subluxation  

PubMed Central

Study Design A retrospective analysis of 7 patients with traumatic rotatory atlanto-axial subluxation. Overview of Literature Cases of traumatic rotatory atlantoaxial subluxation in children are difficult to be stabilized. Surgical challenges include: narrow pedicles, medial vertebral arteries, vertebral artery anomalies, fractured pedicles or lateral masses, and fixed subluxation. The use of O-arm and computer-assisted navigation are still tested as aiding tools in such operative modalities. Purpose Report of clinical series for evaluation of the safety of use of the O-arm and computed assisted-navigation in screw fixation in children with traumatic rotatory atlantoaxial subluxation. Methods In the present study, 7 cases of rotatory atlantoaxial traumatic subluxation were operated between December 2009 and March 2011. All patient-cases had undergone open reduction and instrumentation using atlas lateral mass and axis pedicle screws with intraoperative O-arm with computer-assisted navigation. Results All hardware was safely placed in the planned trajectories in all the 7 cases. Intraoperative O-arm and computer assisted-navigation were useful in securing neural and vascular tissues safety with tough-bony purchases of the hardware from the first and only trial of application with sufficient reduction of the subluxation. Conclusions Successful surgery is possible with using the intraoperative O-arm and computer-assisted navigation in safe and proper placement of difficult atlas lateral mass and axis pedicle screws for rotatory atlantoaxial subluxation in children.

Orief, Tamer; Almusrea, Khaled; Alfawareh, Mohamed; Soualmi, Lahbib; Orz, Yasser



The effect of repeated torque and salivary contamination on the preload of slotted gold implant prosthetic screws  

Microsoft Academic Search

Statement of Problem. Screw loosening and\\/or fracture is common and has been attributed to many factors, including improper torque and preload. Purpose. This study evaluated the effect of repeated preload torque and salivary contamination on the preload of the slotted gold implant prosthetic screw. Material and Methods. Fifteen slotted gold prosthetic screws were tested in an unused stack of components

George K. Tzenakis; William W. Nagy; Raymond A. Fournelle; Virendra B. Dhuru



Factors affecting the interface of cervical spine facet screws placed in the technique by Roy-Camille et al  

Microsoft Academic Search

The objective of the study was to investigate the influence of bone cement, length of burr hole and bone density on pullout force and insertional screw torque of cervical spine facet screws. Both facets of 24 human cervical vertebrae were scanned for bone mineral density (BMD) and assigned to two groups for measuring of insertional screw torque and pullout strength.

T. R. Pitzen; S. Zenner; D. Barbier; T. Georg; W. I. Steudel



Stability: from biomechanical concept to chiropractic practice  

PubMed Central

This paper formalizes stability in a clinician-friendly way and then discusses ways for chiropractors to ensure stability of spinal joints that may have their stability compromized from manipulation. ImagesFigure 1Figure 4Figure 5Figure 6Figure 7

McGill, Stuart M



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

PubMed Central

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



[Is implant removal after percutaneous iliosacral screw fixation of unstable posterior pelvic ring disruptions indicated?].  


The aim of this study was to examine the indication for implant removal (IR) after percutaneous iliosacral screw fixation of unstable posterior pelvic ring disruptions by systematic literature analysis and clinical follow-up examination. Retrospective identification revealed 27 operatively stabilized patients [12 females, mean age: 35 years, ISS 22 points (range: 14-37)] between January 1996 and July 2001. Patient characteristics, AO classification, Hannover fracture scale pelvis, ISS, and DGU pelvis score points were analyzed. All cases showed a C-type lesion (C1:67%, C2:33%). A total of 21 patients were seen at follow-up, 12 with and 9 without IR. In ten cases with IR, clinical outcome improved after surgery according to the DGU pelvis score ( p=0.001, Wilcoxon's test). These mostly young patients also showed a better outcome compared with those cases without IR. Due to the good clinical results, implant removal seems to be beneficial for selected individual patients, especially when pain is present. PMID:15150648

Yücel, N; Lefering, R; Tjardes, T; Korenkov, M; Schierholz, J; Tiling, T; Bouillon, B; Rixen, D



Wall-locking of kink modes in a line-tied screw pinch with a rotating wall  

SciTech Connect

The effect of rotating conducting walls on mode-locking is studied in a line-tied, linear screw pinch experiment and then compared to a torque balance model which has been extended to include differential wall rotation. Wall rotation is predicted to asymmetrically affect the mode-unlocking threshold, with fast rotation eliminating the locking bifurcation. Static error fields are observed to lock the resistive wall mode (RWM) variant of the current driven kink instability by modifying the electromagnetic torque. Using locked modes, the stabilizing effect of wall rotation on the RWM is experimentally demonstrated by illustrating a reduction of the RWM growth rate and an extension of the RWM-stable operation window.

Paz-Soldan, C.; Brookhart, M. I.; Hegna, C. C.; Forest, C. B. [Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)



Adhesively-bonded joints in metallic alloys, polymers and composite materials: Mechanical and environmental durability performance  

Microsoft Academic Search

The factors affecting the mechanical and environmental durability (or stability), and performance of the adhesively bonded joints in various adherends including metallic alloys, polymers and composite materials are studied in detail. The primary function of a joint is to transfer load from one structural member to another. In most bonded joints the load transfer takes place through interfacial shear. At

A. Baldan



[Mechanical circulatory assist using a miniaturized Archimedes screw].  


An axial flow blood pump (Archimedes screw) for intraarterial left ventricular assist was evaluated in comparison to standard roller pump left heart bypass (LHBP) in 13 bovine experiments (bodyweight 74 +/- 15 kg). Full systemic heparinization (ACT greater than 500 s) was used for LHBP in comparison to limited systemic heparinization (ACT greater than 180 s) for axial. A standard battery of blood samples was taken before and at regular intervals throughout perfusion: (table; see text) Transarterial access and relatively limited blood trauma appear to be the main advantages of the evaluated axial flow blood pump. However, the impossibility to assess the pump flow may be a major problem for the management of the failing left ventricle. PMID:2050534

von Segesser, L K; Bisang, B; Leskosek, B; Turina, M



FEM analysis of a new miniplate: stress distribution on the plate, screws and the bone  

PubMed Central

Objectives: Non-homogeneous force distribution along the miniplates and the screws is an unsolved question for skeletal anchorage in orthodontics. To overcome this issue, a miniplate structure was designed featuring spikes placed on the surface facing the cortical bone. The aim of this study was to examine and compare the force distribution of the newly designed plate-screw systems with the conventional one. Methods: A model of bone surface with 1.5 mm cortical thickness, along with the two newly designed miniplates and a standard miniplate-screw were simulated on the three-dimensional model. 200 g experimental force was applied to the tip of the miniplates and the consequential effects on the screws and cortical bone was evaluated using three-dimensional finite element method. Results: As a result of this finite element study, remarkably lower stresses were observed on the screws and the cortical bone around the screws with the newly designed miniplate when compared with the conventional one. Conclusion: The newly designed miniplate that has spikes was found effective in reducing the stress on and around the screws and the force was distributed more equivalently.

Nalbantgil, Didem; Tozlu, Murat; Ozdemir, Fulya; Oztoprak, Mehmet Oguz; Arun, Tulin



Image forces of screw dislocations in a magnetoelectroelastic layered half-plane  

NASA Astrophysics Data System (ADS)

The two-dimensional analysis of elastic, electric, and magnetic fields induced by generalized screw dislocations embedded in a transversely isotropic magnetoelectroelastic layered half-plane is presented in this study. The results indicate that explicit solutions for this problem consist only of the simplest solutions for an infinite magnetoelectroelastic medium with a generalized screw dislocation. It is shown that the physical meaning of the solution is the image method. The mathematical method used in this study provides an automatic determination for the locations and magnitudes of image screw dislocations. From the generalized Peach-Koehler equation, the explicit forms of image forces exerted on a generalized screw dislocation in a layered half-plane are derived from the full-field solutions of the generalized stresses. Numerical results for the full-field distributions of the generalized stresses in the layered half-plane medium are presented. The image forces and equilibrium positions of one screw dislocation, two screw dislocations, and an array of screw dislocations are presented by numerical calculations and are discussed in detail.

Ma, Chien-Ching; Lee, Jui-Mu



Cadaver training module for teaching thoracic pedicle screw placement to residents.  


Surgical training using simulators has been shown to be highly effective but is not available for some applications and is too expensive for many programs. The authors piloted a cadaver-based module with the goal of objectively measuring and significantly improving orthopedic residents' surgical skills in placing thoracic pedicle screws, an advanced procedure. An experienced spine surgeon placed thoracic pedicle screws in 7 cadavers (T1-T12) to establish the skilled accuracy rate. For this pilot study, 3 orthopedic residents unfamiliar with the procedure were given didactic training for safe thoracic pedicle screw insertion. Each resident instrumented alternating sides of 5 consecutive cadavers (T1-T12). Screw positions were graded by computed tomography in a blinded fashion, with accuracy defined as no shank breach of the pedicle or vertebral body. Results were reviewed with the residents, instruction was repeated, and alternating sides of 5 cadavers were instrumented by the residents. The experienced surgeon accurately placed 67 (82%) of 82 pedicle screws. Residents accurately placed 80 (44%) of 180 pedicle screws in the initial set of specimens and 105 (58%) of 180 pedicle screws in the second set of specimens (P=.01). Accuracy varied significantly among residents before but not after computed tomography review. The study's results show that a cadaver-based training module that resembles the clinical setting can be used to teach complex surgical skills to orthopedic residents. PMID:24025002

Tortolani, P Justin; Moatz, Bradley W; Parks, Brent G; Cunningham, Bryan W; Sefter, John; Kretzer, Ryan M



Correction of adolescent idiopathic scoliosis using thoracic pedicle screw fixation versus hook constructs.  


This retrospective study was undertaken to determine the effectiveness and cost of thoracic pedicle screws versus laminar and pedicle hooks in patients undergoing surgical correction of adolescent idiopathic scoliosis (AIS). Immediate preoperative and 6-week postoperative radiographs were examined in 25 consecutive cases of children with AIS who were divided into two groups, those with thoracic pedicle screw constructs and those with thoracic hook constructs. Endpoints collected included radiographic measures, complications, surgical time, implant cost, and quality-of-life measures. Ten children underwent spinal fusion using thoracic pedicle screw fixation and 15 underwent thoracic constructs composed of hooks. Similar sex and age distribution were noted in both groups, and among the 20 girls and 5 boys the average age was 14.5. The mean preoperative Cobb angle was 53.5 degrees for the screw group and 52.5 degrees for the hook group. Correction averaged 70.2% for the screw group and 68.1% for the hook group. There were no significant differences between the two patient groups in terms of percentage of or absolute curve change after surgery. The apical vertebral translation, end vertebral tilt angle, and coronal balance did not differ significantly between the two patient groups. Comparison of operative time and quality of life revealed no significant differences. Screw constructs were significantly more expensive than hook constructs. The correction obtained from thoracic pedicle screw fixation is comparable to traditional hook constructs in AIS. Surgery using either construct effectively corrects AIS. PMID:15958886

Storer, Stephen K; Vitale, Michael G; Hyman, Joshua E; Lee, Francis Y; Choe, Julie C; Roye, David P


Does screw-bone interface modelling matter in finite element analyses?  


The effect of screw-bone interface modelling strategies was evaluated in the setting of a tibial mid-shaft fracture stabilised using locking plates. Three interface models were examined: fully bonded interface; screw with sliding contact with bone; and screw with sliding contact with bone in an undersized pilot hole. For the simulation of the last interface condition we used a novel thermal expansion approach to generate the pre-stress that the bone would be exposed to during screw insertion. The study finds that the global load-deformation response is not influenced by the interface modelling approach employed; the deformation varied by less than 1% between different interaction models. However, interface modelling is found to have a considerable impact on the local stress-strain environment within the bone in the vicinity of the screws. Frictional and tied representations did not have significantly different peak strain values (<5% difference); the frictional interface had higher peak compressive strains while the tied interface had higher tensile strains. The undersized pilot hole simulation produced the largest strains. The peak minimum principal strains for the frictional interface were 26% of those for the undersized pilot hole simulation at a load of 770 N. It is concluded that the commonly used tie constraint can be used effectively when the only interest is the global load-deformation behaviour. Different contact interface models, however, alter the mechanical response around screw holes leading to different predictions for screw loosening, bone damage and stress shielding. PMID:22537570

MacLeod, Alisdair R; Pankaj, Pankaj; Simpson, A Hamish R W



The use of bovine screws to promote bone formation using a tibia model in dogs.  


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 of 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 killed 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 among groups (P < .05). Histologic examination revealed an intimate contact between the newly formed bone and the resorbing bone screws. We conclude that bovine bone screws provide an environment for new bone formation and thus may provide an alternative therapy for enhancing bone formation vertically, including for regenerative procedures as well as before 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



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


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

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



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.



Analysis of stress distribution in a screw-retained implant prosthesis.  


Four types of implant superstructures were screwed onto implant bodies, and the strains created around the implant bodies were compared and analyzed within the IMZ Implant System. Three IMZ implants were embedded in the center of a polyurethane block (30 x 40 x 30 mm), and a total of 16 superstructures was fabricated by 4 methods: 1-piece cast, 1-piece cast/split soldering, soldering, and passive fit. Six strain gauges were placed on the surface of the block 1 mm apart. Three embedded implants were numbered, and a fixed partial denture was placed on these implants and screwed by a torque wrench using 14.5 Ncm torque. This procedure was repeated 7 times for each fixed partial denture, and each created strain was measured when the last screw was tightened. In all fixed partial dentures, strains were produced around the implant bodies when screws retaining the prosthesis were tightened, and the strain was relieved with unscrewing. The magnitude of strain was greater with the 1-piece cast method or the section/solder method than with the soldering and passive-fit methods. Of the 2 soldering methods, when the screw on the middle implant was tightened before those on the terminal 2 implants, the magnitude of strain was lower with the soldering method than with the 1-piece cast/split soldering method. When the order of screw tightening was changed, there were significant differences in the magnitude of strain at each gauge with the soldering method. With the passive-fit method, no differences in the magnitude of strain attributable to the order of screw tightening could be detected. The magnitude of strain produced around a screw-retained implant prosthesis was significantly lower with the passive-fit method when compared to the other 3 fabricating methods. Furthermore, the implants prepared by the passive-fit method were not affected by the order of screw tightening. PMID:10795453

Watanabe, F; Uno, I; Hata, Y; Neuendorff, G; Kirsch, A


Comparison of multiple linear regression and artificial neural network in developing the objective functions of the orthopaedic screws.  


Optimizing the orthopaedic screws can greatly improve their biomechanical performances. However, a methodical design optimization approach requires a long time to search the best design. Thus, the surrogate objective functions of the orthopaedic screws should be accurately developed. To our knowledge, there is no study to evaluate the strengths and limitations of the surrogate methods in developing the objective functions of the orthopaedic screws. Three-dimensional finite element models for both the tibial locking screws and the spinal pedicle screws were constructed and analyzed. Then, the learning data were prepared according to the arrangement of the Taguchi orthogonal array, and the verification data were selected with use of a randomized selection. Finally, the surrogate objective functions were developed by using either the multiple linear regression or the artificial neural network. The applicability and accuracy of those surrogate methods were evaluated and discussed. The multiple linear regression method could successfully construct the objective function of the tibial locking screws, but it failed to develop the objective function of the spinal pedicle screws. The artificial neural network method showed a greater capacity of prediction in developing the objective functions for the tibial locking screws and the spinal pedicle screws than the multiple linear regression method. The artificial neural network method may be a useful option for developing the objective functions of the orthopaedic screws with a greater structural complexity. The surrogate objective functions of the orthopaedic screws could effectively decrease the time and effort required for the design optimization process. PMID:21134702

Hsu, Ching-Chi; Lin, Jinn; Chao, Ching-Kong