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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


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



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



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...



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



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



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



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


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.



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



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



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



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.



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


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

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



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



Allograft interference screw fixation in meniscus transplantation  

Microsoft Academic Search

Allograft meniscus transplantation is indicated to restore proper knee biomechanics and prevent subsequent articular degeneration in patients with a meniscus-deficient knee. A variety of techniques for fixation of meniscal transplants exist, with some techniques using soft-tissue fixation of the meniscal horns and others using bony fixation. The authors present a technique of meniscus transplantation using a tibial slot with allograft

Jack Farr; R. Michael Meneghini; Brian J. Cole



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



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



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



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



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



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



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



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.



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



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



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 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



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



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



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



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



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



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



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



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



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



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



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


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

PubMed Central

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 of 88 patients receiving open subpectoral biceps tenodesis with either interference screw fixation (34 patients) or suture anchor fixation (54 patients). Average follow up was 13 months. Outcomes included Visual Analogue Pain Scale (0–10), ASES score, modified Constant score, pain at the tenodesis site, failure of fixation, cosmesis, deformity (popeye) and complications. Results There were no failures of fixation in this study. All patients showed significant improvement between their preoperative and postoperative status with regard to pain, ASES score, and abbreviated modified Constant scores. When comparing IF screw versus anchor outcomes, there was no statistical significance difference for VAS (p = 0.4), ASES score (p = 0.2), and modified Constant score (P = 0.09). One patient (3%) treated with IF screw complained of persistent bicipital groove tenderness, versus four patients (7%) in the SA group (nonsignificant). Conclusion Subpectoral biceps tenodesis reliably relieves pain and improves function. There was no statistically significant difference in the outcomes studied between the two fixation techniques. Residual pain at the site of tenodesis may be an issue when suture anchors are used in the subpectoral location.

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



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

Microsoft Academic Search

Purpose  To assess the midterm results of closed reduction and percutaneous fixation (CRPF) with computed tomography (CT)-guided sacroiliac\\u000a screw fixation in longitudinal posterior pelvic ring fractures.\\u000a \\u000a \\u000a \\u000a Methods  Thirteen patients with 15 fractures were treated. Eleven patients received a unilateral, two a bilateral, screw fixation.\\u000a Twenty-seven screws were implanted. Continuous on-table traction was used in six cases. Mean radiological follow-up was 13\\u000a months.

Augustinus Ludwig Jacob; Peter Messmer; Klaus-Wilhelm Stock; Norbert Suhm; Bernard Baumann; Pietro Regazzoni; Wolfgang Steinbrich



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



Dynamic hip screw blade fixation for intertrochanteric hip fractures.  


PURPOSE. To assess the one-year outcome of a dynamic hip screw (DHS) blade in the treatment of AO/OTA 31-A1 and 31-A2 intertrochanteric hip fractures. METHODS. 35 men and 65 women aged 47 to 100 (mean, 83) years underwent fixation with a DHS blade for A1 (n=47) and A2 (n=53) intertrochanteric hip fractures after a low-energy injury. Patients were operated on within 48 hours of admission. Anteroposterior and lateral radiographs were examined for the tip-apex distance and femoral shortening. Potential complications were looked for, including implant migration, cut-out, loosening, or breakage. Functional outcome was based on the Parker mobility score. RESULTS. The 30-day and one-year mortality rates were 5% and 20%, respectively. At the one-year follow-up, 81 patients were available, and all fractures had healed without varus deformity. The mean tip-apex distance was 14.1 (range, 5.7-31.1; SD, 4.3) mm. The mean femoral shortening was 4.9 (range, 0-20.2; SD, 4.8) mm. The mean Parker score decreased to 3.8 at one-year follow-up from 5.9 before injury (p<0.001). There was one loss of fixation secondary to a non-traumatic subcapital fracture at 3 months, for which a bipolar hemiarthroplasty was performed. CONCLUSION. The DHS blade system is effective in treating AO/OTA 31-A1 and 31-A2 intertrochanteric hip fractures and results in a low complication rate. PMID:23255634

Leung, Frankie; Gudushauri, Paata; Yuen, Grace; Lau, Tak-Wing; Fang, Christian; Chow, Shew-Ping



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



Is anterior release necessary in severe scoliosis treated by posterior segmental pedicle screw fixation?  

PubMed Central

With the advent of segmental pedicle screw fixation that enables more powerful corrective forces, it is postulated that an additional anterior procedure may be unnecessary even in severe deformities. The purpose of this paper is to evaluate the results of a posterior procedure alone using segmental pedicle screw fixation in severe scoliotic curves over 70°. Thirty-five scoliosis patients treated by pedicle screw fixation and rod derotation were retrospectively analyzed after a minimum follow-up of 2 years (range 2–10.4). The mean age of patients was 15.3 years (range 9.8–34.2). Diagnoses were idiopathic scoliosis in 29, neuromuscular scoliosis in 3 and scoliosis associated with Marfan syndrome in 3. Scoliosis consisted of single thoracic curve in 18, double thoracic in 5 and double major in 12. Twenty-five patients showed a major thoracic curve greater than 70° (range 70–100), and different ten patients showed a major lumbar curve greater than 70° (range 70–105), pre-operatively. The deformity angle, lowest instrumented vertebral tilt (LIVT) and spinal balance were measured. Pre-operatively there were nine patients with coronal decompensation. The pre-operative thoracic curve of 80 ± 9° with the flexibility of 45 ± 11% (45 ± 11° in side-bending film) was corrected to 27 ± 10° at the most recent follow-up, showing a correction of 66% (53°) and loss of correction of 3.0% (3.7°). The pre-operative lumbar curve of 79 ± 12° with the flexibility of 62 ± 14% (30 ± 11° in side-bending film) was corrected to 33 ± 14° at the most recent follow-up [59% (46°) curve correction, 3.5% (3.0°) loss of curve correction]. The pre-operative LIVT of 30 ± 8° was corrected to 11 ± 6°, showing a correction of 62% (19°). Residual coronal decompensation was observed in three patients postoperatively. Pre-operative thoracic kyphosis of 27° (range 0–82) improved postoperatively to 31° (range 14–53). In conclusion, posterior segmental pedicle screw fixation without anterior release in severe scoliosis had satisfactory deformity correction without significant loss of curve correction. In this series a posterior procedure alone obviated the need for the anterior release and avoided complications related anterior surgery.

Kim, Jin-Hyok; Cho, Kyu-Jung; Kim, Sung-Soo; Lee, Jeong-Joon; Han, Yong-Taek



Cannulated Screw Fixation of Jones FracturesA Clinical and Biomechanical Study  

Microsoft Academic Search

Background: Traditional nonsurgical treatment of Jones fractures has high rates of delayed union, nonunion, and refracture. Internal fixation has become the treatment of choice in athletes and active patients.Purpose: The purpose of this study was (1) to review the short- and long-term clinical results of cannulated screw fixation of Jones fractures and (2) to perform a biomechanical evaluation of fatigue

Keri Reese; Alan Litsky; Christopher Kaeding; Angela Pedroza; Nilesh Shah



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


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

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


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.



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



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.




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


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



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.



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


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


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



A video guided solution for screw insertion in orthopedic plate fixation  

NASA Astrophysics Data System (ADS)

In orthopedic and trauma surgery, metallic plates are used for reduction and fixation of bone fractures. In clinical practice, the intra-operative planning for screw fixation is usually based on fluoroscopic images. Screw fixation is then performed on a free-hand basis. As such, multiple attempts may be required in order to achieve an optimal positioning of the fixing screws. To help the physician insert the screws in accordance to the planned position, we propose a method for screw insertion guidance. Our approach uses a small video camera, rigidly placed on the drill, and a set of small markers that are rigidly fixed on a variable angle drill sleeve. In order to investigate the achievable accuracy of our setup, we simulate the estimation of the drill bit position under two different marker arrangements, planar and 3D, and different noise levels. Furthermore, we motivate our choices for marker design and position given the limited space available for marker positioning, the requirement for accurate position estimation of the drill bit and the illumination changes that could affect the surgical site. We also describe our proposed marker detection and tracking pipeline. Our simulation results let us conclude that we can achieve an accuracy of 1° and 1mm in the estimation of angular orientation and tip position of the drill bit respectively, provided that we have accurate marker detection.

Magaraggia, J.; Kleinszig, G.; Graumann, R.; Angelopoulou, E.; Hornegger, J.



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



Scaphoid fracture in the young athlete - therapeutic outcome of internal fixation using the Herbert screw  

Microsoft Academic Search

Background. A fractured scaphoid is a common disabling injury occurring in contact sports. This study was designed to evaluate the therapeutic outcome of Herbert screw fixation for scaphoid fracture in young athletes. Methods. Thirty athletes with 30 scaphoid fractures were treated. According to the Herbert classification, 10 were classified as acute fracture (group I), 6 as fibrous union (group II)

Keiichi Muramatsu; Kazuteru Doi; Noriyuki Kuwata; Fujio Kawakami; Koichiro Ihara; Shinya Kawai



Intraoperative Vertebral Artery Angiography to Guide C1-2 Transarticular Screw Fixation in a Patient with Athetoid Cerebral Palsy  

PubMed Central

We present a case of an athetoid cerebral palsy with quadriparesis caused by kyphotic deformity of the cervical spine, severe spinal stenosis at the cervicomedullary junction, and atlantoaxial instability. The patient improved after the first surgery, which included a C1 total laminectomy and C-arm guided righ side unilateral C1-2 transarticular screw fixation. C1-2 fixation was not performed on the other side because of an aberrant and dominant vertebral artery (VA). Eight months after the first operation, the patient required revision surgery for persistent neck pain and screw malposition. We used intraoperative VA angiography with simultaneous fluoroscopy for precise image guidance during bilateral C1-2 transarticular screw fixation. Intraoperative VA angiography allowed the accurate insertion of screws, and can therefore be used to avoid VA injury during C1-2 transarticular screw fixation in comorbid patients with atlantoaxial deformities.

Chung, Jong Chul; Park, Ki Seok; Ha, Ho Gyun



Laminoplasty and pedicle screw fixation for cervical myelopathy associated with athetoid cerebral palsy: minimum 5-year follow-up.  


Study design. Retrospective case series.Objective. To evaluate the outcomes following laminoplasty and posterior spinal fusion utilizing pedicle screws for cervical myelopathy associated with athetoid cerebral palsy.Summary of Background data. A variety of surgical procedures have been reported including decompression without fusion, spinal fusion by anterior, posterior or circumferential approach in this population. However, involuntary neck movements bring risk of postoperative neurological deterioration due to progression of kyphosis, pseudoarthrosis or adjacent segmental degeneration.Methods. A consecutive series of 17 patients who underwent midline T-saw laminoplasty and posterior spinal fusion using pedicle screws were retrospectively reviewed. There were 8 female and 9 male with a mean age at the time of surgery of 52 years. The mean follow-up was 71 months. Radiographic measures were made in change of Cobb angle of sagittal plane from C2 to C7 and accuracy of pedicle screws. Barthel index (BI) which shows independence in activities of daily life and the Japanese Orthopaedic Association (JOA) score were also evaluated.Results. Preoperative Cobb angle of sagittal plane from C2 to C7 measured 11.0 ± 14.5 degrees of kyphosis which improved to 1.5 ± 12.7 degrees postoperatively (p<0.05). Solid posterior bony fusion was achieved in all cases without rigid orthosis such as Halo vest. There were two cases of adjacent segmental instability, which required additional surgery. Nineteen (13%) out of the 138 screws showed deviation from the pedicle with postoperative computed tomography. However, there were no neurovascular complications during or after the surgery in any cases. Postoperative JOA score and BI significantly improved in 32 ± 16%, and 48 ± 26% respectively.Conclusions. laminoplasty and pedicle screw fixation provided strong internal fixation and improved neurological function and activities of daily living for cervical myelopathy associated with athetoid cerebral palsy. PMID:24042720

Demura, Satoru; Murakami, Hideki; Kawahara, Norio; Kato, Satoshi; Yoshioka, Katsuhito; Tsuchiya, Hiroyuki



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



Comparison of bioabsorbable interference screws and posts for distal fixation in anterior cruciate ligament reconstruction.  


Comparison of the results of bioabsorbable interference screws and posts for hamstring graft distal fixation in ACL reconstructions are presented. The results of 20 patients with bioabsorbable screws were compared to 22 patients with posts. The assessement was based on Lysholm-Gillquist and Marshall scores and the KT-1000 device. In the study group the points gained were 38.9 in the Lysholm-Gillquist and 12.89 in the Marshall scale. The average KT-1000 difference was 2.46 mm. In the control group the points gained were 32.93 in the Lysholm-Gillquist and 11.47 in the Marshall scale. The average KT-1000 difference was 2.5 mm. There were 14 patients in the study group with interference screw problems; in 2 the implants were removed. (1) There are no differences in outcome using bioabsorbable interference screws and posts for distal fixation of hamstring ACL grafts. (2) The lack of bioabsorbtion with poly L-lactide interference screws is frequent and causes problems. PMID:18064457

Gaweda, Krzysztof; Walawski, Jacek; Weg?owski, Robert; Krzyzanowski, Wojciech



Sol-gel derived titania coating with immobilized bisphosphonate enhances screw fixation in rat tibia.  


A variety of surface modifications have been tested for the enhancement of screw fixation in bone, and locally delivered anti-osteoporosis drugs such as bisphosphonates (BP) are then of interest. In this in vivo study, the impact of surface immobilized BP was compared with systemic BP delivery and screws with no BP. After due in vitro characterization, differently treated stainless steel (SS) screws were divided into four groups with 10 rats each. Three of the groups received screws coated with sol-gel derived TiO(2) and calcium phosphate (SS+TiO(2)+CaP). One of these had no further treatment, one had alendronate (BP) adsorbed to calcium phosphate mineral, and one received systemic BP treatment. The fourth group received uncoated SS screws and no BP (control). The screw pullout force was measured after 4 weeks of implantation in rat tibiae. The immobilized amount and release rate of alendronate could be controlled by different immersion times. The SS+TiO(2)+CaP coating did not increase the pullout force compared to SS alone. Surface delivered alendronate enhanced the pullout force by 93% [p = 0.000; 95% Confidence Interval (CI): 67-118%] compared to SS, and by 39% (p = 0.044; 95% CI: 7-71%) compared to systemic alendronate delivery. Both surface immobilized and systemically delivered alendronate improved implant fixation. Also, locally delivered, that is, surface immobilized alendronate showed a better fixation than systemically delivered. Using sol-gel derived TiO(2) as a platform, it is possible to administer controllable amounts of a variety of BPs. PMID:20186735

Linderbäck, Paula; Areva, Sami; Aspenberg, Per; Tengvall, Pentti





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



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)



Percutaneous screw fixation of acetabular fractures with 2D fluoroscopy-based computerized navigation  

Microsoft Academic Search

Introduction  The treatment of displaced acetabular fractures with formal open reduction and internal fixation has gained general acceptance.\\u000a However, extensile exposure can lead to complications. Two-dimensional fluoroscopy-based computerized navigation for placement\\u000a of percutaneous screw across non-displaced acetabular fractures has attracted interest by making use of stored patient-specific\\u000a imaging data to provide real-time guidance in multiple image planes during implant placement. The

Gao Hong; Luo Cong-Feng; Hu Cheng-Fang; Zhang Chang-Qing; Zeng Bing-Fang



Surgical complications in neuromuscular scoliosis operated with posterior- only approach using pedicle screw fixation  

PubMed Central

Background There are no reports describing complications with posterior spinal fusion (PSF) with segmental spinal instrumentation (SSI) using pedicle screw fixation in patients with neuromuscular scoliosis. Methods Fifty neuromuscular patients (18 cerebral palsy, 18 Duchenne muscular dystrophy, 8 spinal muscular atrophy and 6 others) were divided in two groups according to severity of curves; group I (< 90°) and group II (> 90°). All underwent PSF and SSI with pedicle screw fixation. There were no anterior procedures. Perioperative (within three months of surgery) and postoperative (after three months of surgery) complications were retrospectively reviewed. Results There were fifty (37 perioperative, 13 postoperative) complications. Hemo/pneumothorax, pleural effusion, pulmonary edema requiring ICU care, complete spinal cord injury, deep wound infection and death were major complications; while atelectesis, pneumonia, mild pleural effusion, UTI, ileus, vomiting, gastritis, tingling sensation or radiating pain in lower limb, superficial infection and wound dehiscence were minor complications. Regarding perioperative complications, 34(68%) patients had at least one major or one minor complication. There were 16 patients with pulmonary, 14 with abdominal, 3 with wound related, 2 with neurological and 1 cardiovascular complications, respectively. There were two deaths, one due to cardiac arrest and other due to hypovolemic shock. Regarding postoperative complications 7 patients had coccygodynia, 3 had screw head prominence, 2 had bed sore and 1 had implant loosening, respectively. There was a significant relationship between age and increased intraoperative blood loss (p = 0.024). However it did not increased complications or need for ICU care. Similarly intraoperative blood loss > 3500 ml, severity of curve or need of pelvic fixation did not increase the complication rate or need for ICU. DMD patients had higher chances of coccygodynia postoperatively. Conclusion Although posterior-only approach using pedicle screw fixation had good correction rate, complications were similar to previous reports. There were few unusual complications like coccygodynia.

Modi, Hitesh N; Suh, Seung-Woo; Yang, Jae-Hyuk; Cho, Jae Woo; Hong, Jae-Young; Singh, Surya Udai; Jain, Sudeep



In situ screw fixation of slipped capital femoral epiphysis with a novel approach: a double-cohort controlled study  

PubMed Central

Purpose In situ fixation for mild to moderate slipped capital femoral epiphysis (SCFE) remains an acceptable treatment methodology in most centers. Satisfactory fixation results have been reported with the procedure using either the fracture table or radiolucent table, both of which allow the hip to be imaged during the procedure. The position of the pin within the center of the femoral head is important to secure adequate fixation of the capital femoral epiphysis and prevent further slippage with minimal risk for articular penetration and avascular necrosis (AVN) or chondrolysis. Methods We describe a pre-operative planning technique to determine the pin-entry point for percutaneous pinning of SCFE on a radiolucent operating table. A retrospective review of patients who underwent in situ screw fixation with the usage of a cannulated screw on a radiolucent table or fracture table over a 6-year period was conducted. Results The pin-entry point with this technique was reliable in 92% of procedures and comparable in both accuracy and complications to in situ screw fixation on a fracture table. In situ screw fixation on a regular radiolucent table was straightforward and required significantly less surgical time than on the fracture table (P = 0.01). It was also more efficient during a bilateral procedure, as it required only a single preparation and draping of the patient. Conclusion This pre-operative planning technique for deciding the starting point on the proximal femur is helpful in executing an accurate in situ screw fixation of hips with SCFE.

Pring, Maya E.; Adamczyk, Mark; Hosalkar, Harish S.; Bastrom, Tracey P.; Wallace, C. Douglas



Results and complications after posterior lumbar spondylodesis with the "Variable Screw Placement Spinal Fixation System".  


Between March 1988 and March 1990, 45 patients underwent a spondylodesis using transpedicular screws and plates of the "Variable Screw Placement Spinal Fixation System". The indications for operation were spondylolisthesis (13), spondylolisthesis plus discopathy at the adjacent level (4), degenerative discopathy (13), pseudarthrosis after interbody fusion (7), disc herniations (4) and disc herniations plus degenerative discopathy of the adjacent segment (4). In 1992, 43 patients were available for follow-up. The mean follow-up was 3.85 years. Side effects or complications of a more permanent character were seen 25 times in 43 patients. Eight patients had evidence of screw failure: loosening (5), fracture (2), and malposition (1). Complications, screw failure and reoperation all adversely affected clinical outcome. Overall only 60% of the patients reported a positive clinical outcome at follow-up. In our opinion transpedicular instrumentation is a logical system to provide rigid stabilisation, but it has a high learning curve. The original V.S.P. system with its bulky plates and screws appears to be particularly prone to giving a high rate of unwanted side effects not offset by a high clinical success rate. PMID:9265790

Bohnen, I M; Schaafsma, J; Tonino, A J



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



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



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



Pedicle Morphometry for Thoracic Screw Fixation in Ethnic Koreans : Radiological Assessment Using Computed Tomographic Myelography  

PubMed Central

Objective In the thoracic spine, insertion of a pedicle screw is annoying due to small pedicle size and wide morphological variation between different levels of the spine and between individuals. The aim of our study was to analyze radiologic parameters of the pedicle morphometry from T1 to T8 using computed tomographic myelography (CTM) in Korean population. Methods For evaluation of the thoracic pedicle morphometry, the authors prospectively analyzed a consecutive series of 26 patients with stable thoracic spines. With the consent of patients, thoracic CTM were performed, from T1 to T8. We calculated the transverse outer diameters and the transverse angles of the pedicle, distance from the cord to the inner cortical wall of the pedicle, and distance from the cord to the dura. Results Transverse outer pedicle diameter was widest at T1 (7.66 ± 2.14 mm) and narrowest at T4 (4.38 ± 1.55 mm). Transverse pedicle angle was widest at T1 (30.2 ± 12.0°) and it became less than 9.0° below T6 level. Theoretical safety zone of the medial perforation of the pedicle screw, namely, distance from the cord to inner cortical wall of the pedicle was more than 4.5 mm. Conclusion Based on this study, we suggest that the current pedicle screw system is not always suitable for Korean patients. Computed tomography is required before performing a transpedicular screw fixation at the thoracic levels.

Choi, Yong Soo; Yi, Hyeong-Joong; Kim, Young-Joon



Delayed Union of a Sacral Fracture: Percutaneous Navigated Autologous Cancellous Bone Grafting and Screw Fixation  

SciTech Connect

Delayed or non-union of a sacral fracture is a serious clinical condition that may include chronic pain, sitting discomfort, gait disturbances, neurological problems, and inability to work. It is also a difficult reconstruction problem. Late correction of the deformity is technically more demanding than the primary treatment of acute pelvic injuries. Open reduction, internal fixation (ORIF), excision of scar tissue, and bone grafting often in a multi-step approach are considered to be the treatment of choice in delayed unions of the pelvic ring. This procedure implies the risk of neurological and vascular injuries, infection, repeated failure of union, incomplete correction of the deformity, and incomplete pain relief as the most important complications. We report a new approach for minimally invasive treatment of a delayed union of the sacrum without vertical displacement. A patient who suffered a Malgaigne fracture (Tile C1.3) was initially treated with closed reduction and percutaneous screw fixation (CRPF) of the posterior pelvic ring under CT navigation and plating of the anterior pelvic ring. Three months after surgery he presented with increasing hip pain caused by a delayed union of the sacral fracture. The lesion was successfully treated percutaneously in a single step procedure using CT navigation for drilling of the delayed union, autologous bone grafting, and screw fixation.

Huegli, R. W. [University Hospital, Basel, Department of Radiology (Switzerland)], E-mail:; Messmer, P. [University Hospital, Zuerich, Division of Trauma Surgery (Switzerland); Jacob, A. L.; Regazzoni, P. [University Hospital, Basel, Department of Surgery, Trauma Unit (Switzerland); Styger, S. [University Hospital, Basel, Department of Radiology (Switzerland); Gross, T. [University Hospital, Basel, Department of Surgery, Trauma Unit (Switzerland)



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



A Mid-Term Follow-Up Result of Spinopelvic Fixation Using Iliac Screws for Lumbosacral Fusion  

PubMed Central

Objective Iliac screw fixation has been used to prevent premature loosening of sacral fixation and to provide more rigid fixation of the sacropelvic unit. We describe our technique for iliac screw placement and review our experience with this technique. Methods Thirteen consecutive patients who underwent spinopelvic fixation using iliac screws were enrolled. The indications for spinopelvic fixation included long segment fusions for spinal deformity and post-operative flat-back syndrome, symptomatic pseudoarthrosis of previous lumbosacral fusions, high-grade lumbosacral spondylolisthesis, lumbosacral tumors, and sacral fractures. Radiographic outcomes were assessed using plain radiographs, and computed tomographic scans. Clinical outcomes were assessed using the Oswestry Disability Index (ODI) and questionnaire about buttock pain. Results The median follow-up period was 33 months (range, 13-54 months). Radiographic fusion across the lumbosacral junction was obtained in all 13 patients. The average pre- and post-operative ODI scores were 40.0 and 17.5, respectively. The questionnaire for buttock pain revealed the following: 9 patients (69%) perceived improvement; 3 patients (23%) reported no change; and 1 patient (7.6%) had aggravation of pain. Two patients complained of prominence of the iliac hardware. The complications included one violation of the greater sciatic notch and one deep wound infection. Conclusion Iliac screw fixation is a safe and valuable technique that provides added structural support to S1 screws in long-segment spinal fusions. Iliac screw fixation is an extensive surgical procedure with potential complications, but high success rates can be achieved when it is performed systematically and in appropriately selected patients.

Hyun, Seung-Jae; Kim, Yongjung J.; Kim, Young-Bae



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.



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



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

NASA Astrophysics Data System (ADS)

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

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



Pullout strength of tibial graft fixation in anterior cruciate ligament replacement with a patellar tendon graft: interference screw versus staple fixation in human knees  

Microsoft Academic Search

The endoscopic single incision technique for anterior cruciate ligament (ACL) reconstruction with a femoral half-tunnel may\\u000a lead to a graft\\/tunnel mismatch and subsequent protrusion of the block from the tibial tunnel. The typical tibial fixation\\u000a with an interference screw is not possible in these cases. Fixation with staples in a bony groove inferior to the tunnel outlet\\u000a can be used

T. G. Gerich; A. Cassim; C. Lattermann; H. P. Lobenhoffer



Pullout strength of tibial graft fixation in ACL-replacement with a patellar tendon graft: Interference screw versus staple fixation in human knees  

Microsoft Academic Search

Summary  \\u000a The endoscopic single incision technique for ACL reconstruction with a femoral half-tunnel may lead to a graft\\/tunnel mismatch\\u000a and subsequent protrusion of the block from the tibial tunnel. The typical tibial fixation with an interference screw is not\\u000a possible in these cases. Fixation with staples in a bony groove inferior to the tunnel outlet can be used as an

T. G. Gerich; A. Cassim; C. Lattermann; H. P. Lobenhoffer; H. Tscherne



Operative outcome of unstable lower cervical fracture dislocation by lateral mass screw fixation or anterior plating.  


From February 2009 to September 2012, 15 patients (13 males, 2 females; age range, 18-55 years) with the lower cervical fracture dislocation were treated at NRS Medical College, Kolkata. The fracture dislocation occurred in the following cervical segments: C5 (n = 8), C7 (n = 3), C4 (n = 2), and C6 (n = 2). Forteen patients were associated with neurological deficit graded according to ASIA impairment scale. The time interval between Injury and operation was from 3 to 22 days. Eight patients underwent anterior fusion with anterior locked-cervical plate fixation; 7 patients underwent posterior fusion and the lateral mass screw fixation. During each follow-up clinical and radiological parameters were measured; bone fusion and internal fixation condition were observed by x-ray and the neurological recovery was measured by ASIA impairment scale. Follow-up duration was from 3 months to 30 months in different patients which revealed fusion between vertebrae and significant neurological recovery. The fusion time was 4 to 6 months and there was also no instability of vertebrae or loosening of the internal fixation at 12 months. The selection of operative treatment of subaxial cervical spine injury depends upon neurological and radiological criteria. Both posterior and anterior surgical approaches are viable alternatives for treating subaxial spine injuries with different indication and risk profiles. In case of incomplete neurological injury there is significant improvement. Operative treatment certainly decreases the complications related to prolonged immobilisation in recovery phase by making the patient mobile early. PMID:23785912

Sarkar, Partha Sarathi; Mukhopadhyay, Kiran Kumar; Bera, Amiya Kumar; Latif, Abdul



Lateral fixation of AO type-B2 ankle fractures: the Acutrak plus compression screw technique  

PubMed Central

The Acutrak plus compression screw (APCS) (Acumed Inc., Beaverton, OR, USA) is an intramedullary implant which can achieve stable fixation with minimum soft tissue dissection. The characteristics of the APCS include fully-threaded length, headless, cannulated, and variable thread pitch. Twenty-three patients with AO type-B2 ankle fractures treated with lateral fixation by an APCS were retrospectively reviewed. Evaluation of postoperative roentgenograms for adequacy of reduction revealed a good reduction in 22 of 23 (95.7%) patients. The average wound incision was 4.1 cm. The operative time was 25.3 minutes. All the ankle fractures showed radiographic evidence of healing within four months. At the final follow-up, the ankle scores of the patients were evaluated for functional outcomes. Good to excellent results were obtained in 21 (91.3%) patients. No patient complained of symptomatic hardware. In conclusion, lateral fixation of AO type-B2 ankle fractures by APCS offers several advantages including stable fixation, a small surgical wound, less dissection of soft tissue, no palpable hardware, and easy application with a short operating time.

Lee, Yih-Shiunn; Huang, Chien-Rae; Chen, Shih-Hao



[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



Direct repair of spondylolysis by TSRH’s Hook plus screw fixation and bone grafting: biomechanical study and clinical report  

Microsoft Academic Search

Introduction  The aim of the study was to evaluate the biomechanical performance and clinical results of TSRH’s Hook plus screw fixation\\u000a after direct repair of spondylolysis defects in the pars interarticularis.\\u000a \\u000a \\u000a \\u000a Materials and methods  Biomechanical testing of eight calf cadaver lumbar spines were used to provide comparative biomechanical data on TSRH’s Hook\\u000a plus screw fixation, and for the intact and the destabilized

Jian Fan; Guang-rong Yu; Fan Liu; Jian Zhao; Wei-dong Zhao



Bioabsorbable screw divergence angle, not tunnel preparation method influences soft tissue tendon graft-bone tunnel fixation in healthy bone  

Microsoft Academic Search

Bone tunnel fixation of a soft tissue tendon graft is the weak link immediately following ACL reconstruction. This biomechanical\\u000a study evaluated the influence of extraction drilled or step dilated bone tunnels and bioabsorbable screw divergence on soft\\u000a tissue tendon graft fixation. From an initial group of 50 available specimens, similar apparent bone mineral density porcine\\u000a tibiae (1.2 ± 0.24 g\\/cm2) were divided into

Andrew R. Duffee; Jeffrey A. Brunelli; John Nyland; Robert Burden; Akbar Nawab; David Caborn



Cervical Pedicle Screw Fixation Combined with Laminoplasty for Cervical Spondylotic Myelopathy with Instability  

PubMed Central

Study Design A retrospective study. Purpose To evaluate the surgical results of cervical pedicle screw (CPS) fixation combined with laminoplasty for treating cervical spondylotic myelopathy (CSM) with instability. Overview of Literature Cervical fixation and spinal cord decompression are required for CSM patients with instability. However, only a few studies have reported on CPS fixation combined with posterior decompression for unstable CSM patients. Methods Thirteen patients that underwent CPS fixation combined with laminoplasty for CSM with instability were evaluated in this study. We assessed the clinical and radiological results of the surgical procedures. The Japanese Orthopedic Association (JOA) scoring system was used to evaluate the clinical results. The percentages of sli p, difference in sli p angle between maximum flexion and maximum extension of unstable intervertebrae, and perforation rate of CPS were evaluated. Results The mean JOA scores before surgery, immediately after surgery, and at final follow-up were 9.1, 13.3, and 12.6, respectively. The mean percentages of sli p before surgery, immediately after surgery, and at final follow-up were 9.1%, 3.2%, and 3.5%, respectively; there were significant improvements immediately after surgery and at final follow-up. The difference in sli p angle between the maximum flexion and maximum extension of the unstable intervertebrae changed from 9.0° before surgery to 1.6° at the final follow-up. The perforation rate of CPS was 10.9%. Conclusions The results suggest that CPS fixation combined with laminoplasty is an effective surgical procedure for treating CSM with instability.

Uehara, Masashi; Ogihara, Nobuhide; Hirabayashi, Hiroki; Hashidate, Hiroyuki; Mukaiyama, Keijiro; Shimizu, Masayuki; Kato, Hiroyuki



Minimally invasive unilateral pedicle screw fixation and lumbar interbody fusion for the treatment of lumbar degenerative disease.  


Minimally invasive unilateral pedicle screw fixation for the treatment of degenerative lumbar diseases has won the support of many surgeons. However, few data are available regarding clinical research on unilateral pedicle screw fixation associated with minimally invasive techniques for the treatment of lumbar spinal diseases. The purpose of this study was to evaluate clinical outcomes in a selected series of patients with lumbar degenerative diseases treated with minimally invasive unilateral vs classic bilateral pedicle screw fixation and lumbar interbody fusion. Patients in the unilateral group (n=43) underwent minimally invasive unilateral pedicle screw fixation with the Quadrant system (Medtronic, Memphis, Tennessee). The bilateral group (n=42) underwent bilateral instrumentation via the classic approach. Visual analog scale pain scores, Oswestry Disability Index scores, fusion rate, operative time, blood loss, and complications were analyzed. Mean operative time was 75 minutes in the unilateral group and 95 minutes in the bilateral group. Mean blood loss was 220 mL in the unilateral group and 450 mL in the bilateral group. Mean postoperative visual analog scale pain score was 3.10±0.16 in the unilateral group and 3.30±1.10 in the bilateral group. Mean postoperative Oswestry Disability Index score was 15.67±2.3 in the unilateral group and 14.93±2.6 in the bilateral group. Successful fusion was achieved in 92.34% of patients in the unilateral group and 93.56% of patients in the bilateral group. Minimally invasive unilateral pedicle screw fixation is an effective and reliable option for the surgical treatment of lumbar degenerative disease. It causes less blood loss, requires less operative time, and has a fusion rate comparable with that of conventional bilateral fixation. PMID:23937756

Lin, Bin; Xu, Yang; He, Yong; Zhang, Bi; Lin, Qiuyan; He, Mingchang



Tibial fixation comparison of semitendinosus-bone composite allografts fixed with bioabsorbable screws and bone-patella tendon-bone grafts fixed with titanium screws.  


Tibial fixation remains the weak link of ACL reconstruction over the first 8-12 weeks postoperatively. This study compared the biomechanical properties of tibial fixation for a bone-patellar tendon-bone (BPTB) graft and a novel semitendinosus-bone composite (SBC) allograft with mixed cortical-cancellous bone dowels at each end. Seven paired, fresh frozen cadaveric knees (20-45 years) were stripped of all soft tissue attachments and randomly assigned to receive either the BPTB graft or SBC allograft. Grafts were placed into tibial tunnels via a standard protocol and secured with either a 10 mmx28 mm bioabsorbable (SBC) or titanium (BPTB) screw. Grafts were cycled ten times in a servo hydraulic device from 10-50 N prior to pull to failure testing at a rate of 20 mm/min with the force vector aligned with the tibial tunnel ("worst case scenario"). Wilcoxon Signed Rank Tests were used to evaluate biomechanical differences between graft types ( p<0.05). Tibial bone mineral density and interference screw insertion torque were statistically equivalent between graft types. The mode of failure for all constructs was direct screw and graft construct pullout from the tibial tunnel. Significant differences were not observed between graft types for maximum load at failure strength (BPTB=620.8+/-209 N vs. SBC=601.2+/-140 N, p=0.74) or stiffness (BPTB=69.8 N/mm+/-29 N/mm vs SBC=47.1+/-31.6 N/mm, p=0.24). The SBC allograft yielded significantly more displacement prior to failure than the BPTB graft (15.1+/-4.9 mm vs 9.2+/-1.3 mm, p=0.04). Increased construct displacement appeared to be due to fixation failure, with some evidence of graft tissue tearing around the sutures: Bioabsorbable screw (10 x 28 mm) fixation of the SBC allograft produced unacceptable displacement levels during testing. Further study is recommended using a titanium interference screw or a longer bioabsorbable screw for SBC graft fixation under cyclic loading conditions. PMID:12845425

Kocabey, Y; Klein, S; Nyland, J; Caborn, D



Does keel size, the use of screws, and the use of bone cement affect fixation of a metal glenoid implant?  

Microsoft Academic Search

The objective of this study was to determine the effect of screws and keel size on the fixation of an all-metal glenoid component. A prototype stainless-steel glenoid component was designed and implanted in 10 cadaveric scapulae. A testing apparatus capable of producing a loading vector at various angles, magnitudes, and directions was used. The independent variables included six directions and

Ryan T Bicknell; Allan S. L Liew; Matthew R Danter; Stuart D Patterson; Graham J. W King; David G Chess; James A Johnson



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



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



One-stage posterior C2 and C3 pedicle screw fixation or combined anterior C2-C3 fusion for the treatment of unstable hangman's fracture  

PubMed Central

The present study aimed to evaluate the effect of using one-stage posterior C2 and C3 pedicle screw fixation or combined anterior C2-C3 fusion in the treatment of unstable hangman’s fracture. A total of 13 patients with unstable hangman’s fractures underwent C2 and C3 pedicle screw fixation, lamina interbody fusion or combined anterior C2-C3 fusion and imaging examinations to evaluate the fracture fixation and healing condition at three days and three months following surgery. Postoperative X-ray and computed tomography (CT) results showed high fracture reduction, good internal fixation position and reliable fracture fixation. The three-month postoperative CT showed good vertebral fracture healing. C2 and C3 pedicle screw fixation has a good curative effect in the treatment of unstable hangman’s fracture. The direct fixation of the fracture enables early ambulation by the patients.




Medial pelvic migration of the lag screw in a short gamma nail after hip fracture fixation: a case report and review of the literature  

PubMed Central

Hip fractures are a common injury among the elderly. Internal fixation with an intramedullary (IM) system has gained popularity for the treatment of intertrochanteric femur fractures. Multiple complications associated with IM fracture fixation have been described, however, we report a rare complication of medial pelvic migration of the lag screw of a short IM nail in a stable construct ten weeks post surgery. The patient was subsequently treated with Lag Screw removal and revision surgery with a shorter Lag Screw and an accessory cannulated screw acting as a de-rotational device. The patient did well with the revision surgery and was able to return to full activities.



Medial pelvic migration of the lag screw in a short gamma nail after hip fracture fixation: a case report and review of the literature.  


Hip fractures are a common injury among the elderly. Internal fixation with an intramedullary (IM) system has gained popularity for the treatment of intertrochanteric femur fractures. Multiple complications associated with IM fracture fixation have been described, however, we report a rare complication of medial pelvic migration of the lag screw of a short IM nail in a stable construct ten weeks post surgery. The patient was subsequently treated with Lag Screw removal and revision surgery with a shorter Lag Screw and an accessory cannulated screw acting as a de-rotational device. The patient did well with the revision surgery and was able to return to full activities. PMID:20799945

Li, Xinning; Heffernan, Michael J; Kane, Christina; Leclair, Walter



Screw fixation is superior to N-butyl-2-cyanoacrylate in onlay grafting procedure: a histomorphologic study.  


The aim of this study is the histopathological evaluation of the efficiency of N-2-butyl cyanoacrylate in the fixation of bone block grafts on mandible. Autogenous monocortical block grafts taken from tibial bone were fixed to the outer surface of the angle of the mandible with N-2-butyl cyanoacrylate on the right side and mini screws on the left side. Postoperatively in the first and third months, six rabbits were killed and tissue samples were obtained from the grafted area. No significant difference was found between the cyanoacrylate and screw group with respect to inflammation or foreign body reaction. The level of graft necrosis was found to be significantly higher in the cyanoacrylate group than in the screw group in both the first and third month samples. Bone formation between the graft and recipient bone was evaluated and bone formation was found to be significantly higher in the screw group than in the cyanoacrylate group. No trabecular bone formation was observed between the graft and recipient bone in the cyanoacrylate group. Screw fixation was found to be superior to N-2-butyl cyanoacrylate in all parameters. PMID:22113114

Ba?, B; Ozden, B; Bekçio?lu, B; Sanal, K O; Gülbahar, M Y; Kabak, Y B



Treatment of neuromuscular scoliosis with posterior-only pedicle screw fixation  

PubMed Central

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 postoperative and final follow-up Cobb's angle and pelvic obliquity were analyzed on radiographs. The average age of the patients was 17.5 years (range, 8–44 years) and the average follow-up was 25 months (18–52 months). Results Average Cobb's angle was 78.53° before surgery, 30.70° after surgery (60.9% correction), and 33.06° at final follow-up (57.9% correction) showing significant correction (p < 0.0001). There were 9 patients with curves more than 90° showed an average pre-operative, post operative and final follow up Cobb's angle 105.67°, 52.33° (50.47% correction) and 53.33° (49.53% correction) respectively and 17 patients with curve less than 90° showed average per operative, post operative and final follow up Cobb's angle 64.18, 19.24(70% correction) and 21.41(66.64 correction); which suggests statistically no significant difference in both groups (p = 0.1284). 7 patients underwent Posterior vertebral column resection due to the presence of a rigid curve. The average spinal-pelvic obliquity was 16.27° before surgery, 8.96° after surgery, and 9.27° at final follow-up exhibited significant correction (p < 0.0001). There was 1 poliomyelitis patient who had power grade 3 in lower limbs pre-operatively, developed grade 2 power post-operatively and gradually improved to the pre-operative stage. There was 1 case of deep wound infection and no case of pseud-arthrosis, instrument failures or mortality. Conclusion Results indicate that in patients with neuromuscular scoliosis, acceptable amounts of curve correction can be achieved and maintained with posterior-only pedicle screw instrumentation without anterior release procedure.

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



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


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

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



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


[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



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



A comparative analysis of Ender's-rod and compression screw and side plate fixation of intertrochanteric fractures of the hip.  


The purpose of this study is to compare the results of compression screw fixation and Ender's rods in the treatment of intertrochanteric fractures of the hip. A retrospective analysis of 77 cases of both unstable and stable cases of intertrochanteric fractures showed a higher incidence of complications in the Ender's group; these included backing out, distal femur fracture, need for a secondary procedure, external rotation deformity, and knee pain. Indications for the use of Ender's rods may be found among patients with burns, soft-tissue injuries of the proximal thigh, and patients refusing blood transfusions. Wiring of the distal ends of Ender's rods prevents backing out of the rods. Dacron tape has also been successfully used to prevent the distal ends of the rods from backing out in the last six of the 77 cases. The compression hip screw is a preferred treatment of choice in both stable and unstable intertrochanteric fractures. PMID:2364601

Rao, J P; Hambly, M; King, J; Benevenia, J



Direct Pars Repair Surgery Using Two Different Surgical Methods : Pedicle Screw with Universal Hook System and Direct Pars Screw Fixation in Symptomatic Lumbar Spondylosis Patients  

PubMed Central

Objective The authors performed a retrospective study to assess the clinical and radiological outcome in symptomatic lumbar spondylolysis patients who underwent a direct pars repair surgery using two different surgical methods; pedicle screw with universal hook system (PSUH) and direct pars screw fixation (DPSF), and compared the results between two different treated groups. Methods Forty-seven consecutive patients (PSUH; 23, DPSF; 15) with symptomatic lumbar spondylolysis who underwent a direct pars repair surgery were included. The average follow-up period was 37 months in the PSUH group, and 28 months in the DPSF group. The clinical outcome was measured using visual analogue pain scale (VAS) and Oswestry disability index (ODI). The length of operation time, the amount of blood loss, the duration of hospital stay, surgical complications, and fusion status were also assessed. Results When compared to the DPSF group, the average preoperative VAS and ODI score of the PSUH group were less decreased at the last follow-up; (the PSUH group; back VAS : 4.9 vs. 3.0, leg VAS : 6.8 vs. 2.2, ODI : 50.6% vs. 24.6%, the DPSF group; back VAS : 5.7 vs. 1.1, leg VAS : 6.1 vs. 1.2, ODI : 57.4% vs. 18.2%). The average operation time was 174.9 minutes in the PSUH group, and 141.7 minutes in the DPSF group. The average blood loss during operation was 468.8 cc in the PSUH group, and 298.8 cc in the DPSF group. The average hospital stay after operation was 8.9 days in the PSUH group, and 7 days in the DPSF group. In the PSUH group, there was one case of a screw misplacement requiring revision surgery. In the DPSF group, one patient suffered from transient leg pain. The successful bone fusion rate was 78.3% in the PSUH group, and 93.3% in the DPSF group. Conclusion The present study suggests that the technique using direct pars screw would be more effective than the method using pedicle screw with lamina hook system, in terms of decreased operation time, amount of blood loss, hospital stay, and increased fusion success rate, as well as better clinical outcome.

Shin, Myung-Hoon; Rathi, Nitesh Kumar; Park, Chun-Kun



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



Posterior Interspinous Fusion Device for One-Level Fusion in Degenerative Lumbar Spine Disease : Comparison with Pedicle Screw Fixation - Preliminary Report of at Least One Year Follow Up  

PubMed Central

Objective Transpedicular screw fixation has some disadvantages such as postoperative back pain through wide muscle dissection, long operative time, and cephalad adjacent segmental degeneration (ASD). The purposes of this study are investigation and comparison of radiological and clinical results between interspinous fusion device (IFD) and pedicle screw. Methods From Jan. 2008 to Aug. 2009, 40 patients underwent spinal fusion with IFD combined with posterior lumbar interbody fusion (PLIF). In same study period, 36 patients underwent spinal fusion with pedicle screw fixation as control group. Dynamic lateral radiographs, visual analogue scale (VAS), and Korean version of the Oswestry disability index (K-ODI) scores were evaluated in both groups. Results The lumbar spine diseases in the IFD group were as followings; spinal stenosis in 26, degenerative spondylolisthesis in 12, and intervertebral disc herniation in 2. The mean follow up period was 14.24 months (range; 12 to 22 months) in the IFD group and 18.3 months (range; 12 to 28 months) in pedicle screw group. The mean VAS scores was preoperatively 7.16±2.1 and 8.03±2.3 in the IFD and pedicle screw groups, respectively, and improved postoperatively to 1.3±2.9 and 1.2±3.2 in 1-year follow ups (p<0.05). The K-ODI was decreased significantly in an equal amount in both groups one year postoperatively (p<0.05). The statistics revealed a higher incidence of ASD in pedicle screw group than the IFD group (p=0.029). Conclusion Posterior IFD has several advantages over the pedicle screw fixation in terms of skin incision, muscle dissection and short operative time and less intraoperative estimated blood loss. The IFD with PLIF may be a favorable technique to replace the pedicle screw fixation in selective case.

Kim, Ho Jung; Chun, Hyoung Joon; Oh, Suck Jun; Kang, Tae Hoon; Yang, Moon Sool



Hydroxyapatite coating enhances fixation of loaded pedicle screws: a mechanical in vivo study in sheep  

Microsoft Academic Search

Loosening of the pedicle screws with subsequent non-union or loss of correction is a frequent problem in spinal instrumentation. In a clinical pilot study, coating of pedicle screws with plasma-sprayed hydroxyapatite (HA) resulted in a significant increase of removal torque. An experimental study was performed to investigate the effects of HA coating on the pull-out resistance. Thirteen sheep were operated

Bengt Sandén; Claes Olerud; Sune Larsson



[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



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



Distal femoral fracture through the screw hole of a ligament augmentation device fixation  

Microsoft Academic Search

Summary: Complications associated with fixation of artificial ligaments in augmented repair of the anterior cruciate ligament (ACL) have been reported throughout the literature. However, fractures following ligament augmentation device (LAD) fixation appear to be rare. We report the case of a 43-year-old woman, injured in a road accident, who sustained a depressed fracture of the tibial plateau and knee instability.

Christof Radler; Gerald E. Wozasek; Helmut Seitz; Vilmos Vécsei



A Computed Tomography-Based Anatomic Comparison of Three Different Types of C7 Posterior Fixation Techniques : Pedicle, Intralaminar, and Lateral Mass Screws  

PubMed Central

Objective The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation. Methods A total of 120 patients (60 men and 60 women) with an average age of 51.7±13.6 years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student's t-test. Results At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, 33.9±3.1 mm; ILS, 30.8±3.1 mm; LMS, 10.6±1.3; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, 6.8±1.2 mm; lamina, 6.2±1.2 mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, 18.6±2.0 mm; pedicle, 8.7±1.3 mm; p<0.01). The ideal screw trajectory at C7 was also measured (47.8±4.8° for ILS and 35.1±8.1° for PS). Conclusion Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7.

Jang, Woo Young; Kim, Il Sup; Lee, Ho Jin; Sung, Jae Hoon; Lee, Sang Won



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.



Poly L-Lactide Co-Glycolide/?-Tricalcium Phosphate Interference Screw Fixation for Bone-Patellar Tendon Bone Anterior Cruciate Ligament Reconstruction.  


The objective of this study was to prospectively evaluate the clinical effectiveness and radiographic response of a poly (l-lactide co-glycolide)/?-tricalcium phosphate (PlLA/PGA/?-TCP) interference screw used in bone-patellar tendon-bone (BPTB) anterior cruciate ligament (ACL) reconstruction. A prospective, consecutive series of 104 patellar tendon bone-tendon-bone ACL reconstructions fixed with PLLA/PGA/?-TCP biocomposite screws were studied. After receiving the approval from the Institutional Review Board, the following data were collected preoperatively from all patients: physical examination, Lysholm score, Cincinnati, and International Knee Documentation Committee (IKDC) activity scores, and standard knee radiographs. In addition to these, follow-up assessments included Lachman and pivot-shift tests, Tegner scores, and KT side-to-side differences. Surgical failure was defined by a 2+ Lachman test, positive pivot-shift test, side-to-side KT difference of greater than 5 mm or subsequent ACL revision surgery. Approximately 95% of patients (99 of 104) with an average follow-up of 36 months (range, 24 to 68) are reported. The average age was 30 years (range, 13 to 57 years). Postoperatively, four patients demonstrated +1 Lachman score and one patient demonstrated a +2 Lachman score. Postoperative pivot-shift tests were a trace positive in one patients and +1 in two patients. The average KT side-to-side difference was 0.65 mm. All, but five patients, demonstrated KT side-to-side measurements of 3 mm or less and those five demonstrated measurements of 5 mm or less. No revision reconstructions were performed. Significant improvements in Cincinnati score (41 to 85 postoperative) and Lysholm score (46 to 90) were observed. The average postoperative Tegner score was 7. IKDC activity score increased from 2.3 to 3.1. Approximately 4% of patients (4 of 99) met the criteria for failure. A PLLA/PGA/?-TCP biocomposite interference fixation screw provides good graft fixation, with good radiographic incorporation, without adverse events.The level of evidence of the study is IV. PMID:23575562

Barber, F Alan; Hrnack, Scott A



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

PubMed Central

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

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



Supplementary transverse wire fixation through cuneiforms and cuboid in combination with a screw for the comminuted tarsal navicular fractures  

Microsoft Academic Search

An isolated fracture dislocation of the body of the tarsal navicular is an unusual injury; a displaced one is difficult to treat, and a comminuted one poses a further therapeutic problem. Previously, several authors have described various options with additional fixation across the cuneonavicular joint through a tarsal navicular. However, in the comminuted tarsal navicular fracture, the question arises regarding

Kazumasa Kimura; Hideo Adachi; Masaaki Ogawa; Hideo Sakamoto



Cervico-cephalic Medial Screw Migration after Intertrochanteric Fracture Fixation, OTA/AO 31-A2, Using Intramedullary Nail Gamma3®. Report of 2 Cases and Literature Review.  


SUMMARY:: Cervico-cephalic screw medialization is a rare complication after intertrochanteric fracture synthesis with a Gamma3® type intramedullary nail. Only 6 cases of intrapelvic penetration by Gamma 3® lag screw have been described. We now describe two additional cases and a review of the literature. PMID:23515128

Lozano-Alvarez, Carlos; Alier, Albert; Pelfort, Xavier; Martínez-Díaz, Santos; Puig, Lluis



Segmental pedicle screw fixation for a scoliosis patient with post-laminectomy and post-irradiation thoracic kyphoscoliosis of spinal astrocytoma.  


Spinal deformity is an important clinical manifestation after surgery for spinal cord tumors. One-third of patients who receive laminectomies and irradiation of the spinal column develop scoliosis, kyphosis, or kyphoscoliosis. Recent reports indicate good results after scoliosis surgery using segmental pedicle screws and a navigation system, but these reported studies have not included surgery for post-laminectomy kyphosis. Hooks and wires are ineffective in such patients who undergo laminectomy, and there are also high perioperative risks with insertion of pedicle screws because landmarks have been lost. Here, we report on the 5-year follow-up of a 13-year-old male patient with post-laminectomy and post-irradiation thoracic kyphoscoliosis after surgical treatment of spinal astrocytoma. Posterior segmental pedicle screw fixation was performed safely using a computer-assisted technique. The authors present the first case report for treatment of this condition using a navigation system. PMID:22918210

Tanaka, Masato; Sugimoto, Yoshihiro; Misawa, Haruo; Takigawa, Tomoyuki; Kunisada, Toshiyuki; Ozaki, Toshifumi



Evaluation of femoral head vascularization in slipped capital femoral epiphysis before and after cannulated screw fixation with use of contrast-enhanced MRI: initial results  

Microsoft Academic Search

In this study we used contrast-enhanced magnetic resonance imaging (MRI) to evaluate the vascularization of the femoral head\\u000a in children with slipped capital femoral epiphysis (SCFE) before and after cannulated screw fixation. Eleven consecutive children\\u000a with SCFE, seven boys and four girls, aged 10–15 years were included in the study. There were no preslips; four children had\\u000a acute, three acute-on-chronic, and

G. Staatz; D. Honnef; A. Kochs; C. Hohl; T. Schmidt; H. Röhrig; R. W. Günther



Posterior decompression and short segmental pedicle screw fixation combined with vertebroplasty for K?mmell's disease with neurological deficits  

PubMed Central

The aim of this study was to investigate the treatment of Kümmell’s disease with neurological deficits and to determine whether intravertebral clefts are a pathognomonic sign of Kümmell’s disease. A total of 17 patients who had initially been diagnosed with Kümmell’s disease were admitted, one patient was excluded from this study. Posterior decompression and vertebroplasty for the affected vertebrae were conducted. Pedicle screw fixation and posterolateral bone grafts were performed one level above and one level below the affected vertebrae. Vertebral tissue was extracted for histopathological examination. The mean time of follow-up was 22 months (range, 18 to 42 months). The anterior and middle vertebral heights were measured on standing lateral radiographs prior to surgery, one day postoperatively and at final follow-up. The Cobb angle, the visual analog scale (VAS) and the Frankel classification were used to evaluate the effects of the surgery. The VAS, anterior and middle vertebral heights and the Cobb angle were improved significantly one day postoperatively and at the final follow-up compared with the preoperative examinations (P<0.05). No significant differences were observed between the one-day postoperative results and those at final follow-up (P>0.05). The neurological function of all patients was improved by at least one Frankel grade. All patients in this study exhibited intravertebral clefts, and postoperative pathology revealed bone necrosis. One patient (not included in this study) showed an intravertebral cleft, but the pathology report indicated a non-Hodgkin’s lymphoma. The intravertebral cleft sign is not pathognomonic of Kümmell’s disease. Posterior decompression with short-segment fixation and fusion combined with vertebroplasty is an effective treatment for Kümmell’s disease with neurological deficits.




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.



Successful fusion of remote type II odontoid fracture using anterior screw fixation of the odontoid and rhBMP-2: report of two cases.  


Anterior screw fixation of the odontoid is contraindicated in remote type II fractures. The alternative surgical treatment consists of a posterior C1 to C2 or an occiput to C3 fusion, which is met with much resistance by patients as this option limits head motion, especially rotational movement. Furthermore, elderly patients may not be medically fit to undergo surgery of this magnitude. This report presents two remote type II odontoid fractures in elderly patients (67 and 73 years of age) who were successfully treated by means of anterior screw fixation of the odontoid along with an injection of recombinant human bone morphogenic protein (rhBMP-2) (Medtronic Inc.) into the fracture line with infiltration of the fibrous union tissue and adjacent anterior longitudinal ligament. To our knowledge, this is the first documented report of solid fusion of remote type II odontoid fracture treated with rhBMP-2 and anterior screw fixation. The authors believe that this technique may be a viable alternative for the treatment of failed odontoid fractures older than six months. PMID:23798264

Morgan, Jeremy P; Asfora, Wilson T



Two levels above and one level below pedicle screw fixation for the treatment of unstable thoracolumbar fracture with partial or intact neurology  

PubMed Central

Background Treatment of unstable thoracolumbar fractures is controversial regarding short or long segment pedicle screw fixation. Although long level fixation is better, it can decrease one motion segment distally, thus increasing load to lower discs. Methods We retrospectively analyzed 31 unstable thoracolumbar fractures with partial or intact neurology. All patients were operated with posterior approach using pedicle screws fixed two levels above and one level below the fracture vertebra. No laminectomy, discectomy or decompression procedure was done. Posterior fusion was achieved in all. Post operative and at final follow-up radiological evaluation was done by measuring the correction and maintenance of kyphotic angle at thoracolumbar junction. Complications were also reported including implant failure. Results Average follow-up was 34 months. All patients had full recovery at final follow-up. Average kyphosis was improved from 26.7° to 4.1° postoperatively and to 6.3° at final follow-up. And mean pain scale was improved from 7.5 to 3.9 postoperatively and to 1.6 at final follow-up, All patients resumed their activity within six months. Only 4 (12%) complications were noted including only one hardware failure. Conclusion Two levels above and one level below pedicle screw fixation in unstable thoracolumbar burst fracture is useful to prevent progressive kyphosis and preserves one motion segment distally.

Modi, Hitesh N; Chung, Kook Jin; Seo, Il Woo; Yoon, Hoi Soo; Hwang, Ji Hyo; Kim, Hong Kyun; Noh, Kyu Cheol; Yoo, Jung Han



The influence of sacral morphology on the existence of secure S1 and S2 transverse bone corridors for iliosacroiliac screw fixation.  


Sacroiliac (SI) screw fixation for unstable pelvic fractures stands out as the only minimally invasive method among all other ORIF procedures. A strictly transverse screw trajectory is needed for central or bilateral fracture patterns up to a complete iliosacroiliac fixation. However, secure screw insertion is aggravated by a narrow sacroiliac bone stock. This study investigates the influence of a highly variable sacral morphology to the existence of S1 and S2 transverse corridors. The analysis contained in this study is based on 125 CT datasets of intact human pelvises. First, sacral dysplasia was identified using the "lateral sacral triangle" method in a lateral 3-D semi-transparent pelvic view. Second, 3-D corridors for a 7.3mm screw in the upper two sacral levels were visualised using a proprietary IT workflow of custom-made programme scripts based on the Amira(®)-software. Shape-describing measurement variables were calculated as output variables. The results show a significant linear correlation between ratioT and the screw-limiting S1 isthmus height (Pearson coefficient of 0.84). A boundary ratio of 1.5 represented a positive predictive value of 96% for the existence of a transverse S1-corridor for at least one 7.3mm screw. In 100 out of 125 pelvises (80%), a sufficient S1 corridor existed, whereas in 124 specimens (99%), an S2 corridor was found. Statistics revealed significantly larger S1 and S2 corridors in males compared to females (p<0.05). However, no gender-related differences were observed for clinically relevant numbers of up to 3 screws in S1 and 1 screw in S2. The expanse of the S1 corridor is highly influenced by the dimensions of the dysplastic elevated upper sacrum, whereas the S2 corridor is not affected. Hence, in dysplastic pelvises, sacroiliac screw insertion should be recommended into the 2nd sacral segment. Our IT workflow for the automatic computation of 3-D corridors may assist in surgical pre-operative planning. Furthermore, the workflow could be implemented in computer-assisted surgery applications involving pelvic trauma. PMID:24004615

Mendel, T; Noser, H; Kuervers, J; Goehre, F; Hofmann, G O; Radetzki, F



Treatment of acute thoracolumbar burst fractures with kyphoplasty and short pedicle screw fixation: Transpedicular intracorporeal grafting with calcium phosphate: A prospective study  

PubMed Central

Background: In the surgical treatment of thoracolumbar fractures, the major problem after posterior correction and transpedicular instrumentation is failure to support the anterior spinal column, leading to loss of correction and instrumentation failure with associated complaints. We conducted this prospective study to evaluate the outcome of the treatment of acute thoracolumbar burst fractures by transpedicular balloon kyphoplasty, grafting with calcium phosphate cement and short pedicle screw fixation plus fusion. Materials and Methods: Twenty-three consecutive patients of thoracolumbar (T9 to L4) burst fracture with or without neurologic deficit with an average age of 43 years, were included in this prospective study. Twenty-one from the 23 patients had single burst fracture while the remaining two patients had a burst fracture and additionally an adjacent A1-type fracture. On admission six (26%) out of 23 patients had neurological deficit (five incomplete, one complete). Bilateral transpedicular balloon kyphoplasty with liquid calcium phosphate to reduce segmental kyphosis and restore vertebral body height and short (three vertebrae) pedicle screw instrumentation with posterolateral fusion was performed. Gardner kyphosis angle, anterior and posterior vertebral body height ratio and spinal canal encroachment were calculated pre- to postoperatively. Results: All 23 patients were operated within two days after admission and were followed for at least 12 months after index surgery. Operating time and blood loss averaged 45 min and 60 cc respectively. The five patients with incomplete neurological lesions improved by at least one ASIA grade, while no neurological deterioration was observed in any case. The VAS and SF-36 (Role physical and Bodily pain domains) were significantly improved postoperatively. Overall sagittal alignment was improved from an average preoperative 16° to one degree kyphosis at final followup observation. The anterior vertebral body height ratio improved from 0.6 preoperatively to 0.9 (P<0.001) postoperatively, while posterior vertebral body height improved from 0.95 to 1 (P<0.01). Spinal canal encroachment was reduced from an average 32% preoperatively to 20% postoperatively. Cement leakage was observed in four cases (three anterior to vertebral body and one into the disc without sequalae). In the last CT evaluation, there was a continuity between calcium phosphate and cancellous vertebral body bone. Posterolateral radiological fusion was achieved within six months after index operation. There was no instrumentation failure or measurable loss of sagittal curve and vertebral height correction in any group of patients. Conclusions: Balloon kyphoplasty with calcium phosphate cement secured with posterior short fixation in the thoracolumbar spine provided excellent immediate reduction of posttraumatic segmental kyphosis and significant spinal canal clearance and restored vertebral body height in the fracture level.

Korovessis, Panagiotis; Repantis, Thomas; George, Petsinis



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



Biomechanical comparison of supplemental posterior fixations for two-level anterior lumbar interbody fusion.  


Posterior instrumentations have been used to supplement anterior lumbar interbody fusion with cages. Biomechanical studies on single-level anterior lumbar interbody fusion show that stand-alone cages supplemented with posterior translaminar facet or transfacet screw fixation exhibit comparable stability to those supplemented with pedicle screw/rod fixation, while stability of multilevel anterior lumbar interbody fusion remains mostly unknown. The objectives of this study are to compare the stabilization of three supplemental posterior fixations to two-level anterior lumbar interbody fusion, including translaminar facet fixation, transfacet screw fixation, and pedicle screw/rod fixation. Flexibility tests were conducted on fresh-frozen calf spines with moment up to 8.5 N m in flexion, extension, lateral bending, and axial rotation. Each specimen was tested at three stages: intact, anterior lumbar interbody fusion using Polyetheretherketone (PEEK) interbody cage at L3-L4 and L4-L5, and the same anterior lumbar interbody fusion plus one of the three supplemental posterior fixations. The addition of the supplemental posterior fixation increased stiffness at the fusion levels significantly in flexion (9.9 times), extension (5.4 times), and lateral bending (4.1 times). The pedicle screw/rod and translaminar screw fixations provide approximately 40% higher stiffness than the transfacet screw in lateral bending. The pedicle screw/rod fixation also displayed a trend of superior fixation in extension. Supplemental posterior fixation significantly improved stability of two-level anterior lumbar interbody fusion when compared to the stand-alone cages. Pedicle screw/rod system is still the "gold standard" in providing supplemental stability. However, both translaminar facet screws and transfacet screws are good alternatives to provide adequate fixation. PMID:23662340

Wang, Mei; Tang, Shu-Jie; McGrady, Linda M; Rao, Raj D



Percutaneous kyphoplasty and pedicle screw fixation for the management of thoraco-lumbar burst fractures  

PubMed Central

The study design includes prospective evaluation of percutaneous osteosynthesis associated with cement kyphoplasty on 18 patients. The objective of the study is to assess the efficacy of a percutaneous method of treating burst vertebral fractures in patients without neurological deficits. Even if burst fractures are frequent, no therapeutic agreement is available at the moment. We report in this study the results at 2 years with a percutaneous approach for the treatment of burst fractures. 18 patients were included in this study. All the patients had burst vertebral fractures classified type A3 on the Magerl scale, between levels T9 and L2. The patients’ mean age was 53 years (range 22–78 years) and the neurological examination was normal. A percutaneous approach was systematically used and a kyphoplasty was performed via the transpedicular pathway associated with percutaneous short-segment pedicle screw osteosynthesis. The patients’ follow-up included CT scan analysis, measurement of vertebral height recovery and local kyphosis, and clinical pain assessments. With this surgical approach, the mean vertebral height was improved by 25% and a mean improvement of 11.28° in the local kyphotic angle was obtained. 3 months after the operation, none of the patients were taking class II analgesics. The mean duration of their hospital stay was 4.5 days (range 3–7 days) and the mean follow-up period was 26 months (range 17–30 months). No significant changes in the results obtained were observed at the end of the follow-up period. Minimally invasive methods of treating burst vertebral fractures can be performed via the percutaneous pathway. This approach gives similar vertebral height recovery and kyphosis correction rates to those obtained with open surgery. It provides a short hospital stay, however, and might therefore constitute a useful alternative to open surgical methods.

Blondel, Benjamin; Metellus, Philippe; Gaudart, Jean; Adetchessi, Tarek; Dufour, Henry



[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



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



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



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



In situ screw fixation of slipped capital femoral epiphysis with a novel approach: a double-cohort controlled study  

Microsoft Academic Search

Purpose  In situ fixation for mild to moderate slipped capital femoral epiphysis (SCFE) remains an acceptable treatment methodology\\u000a in most centers. Satisfactory fixation results have been reported with the procedure using either the fracture table or radiolucent\\u000a table, both of which allow the hip to be imaged during the procedure. The position of the pin within the center of the femoral

Maya E. Pring; Mark Adamczyk; Harish S. Hosalkar; Tracey P. Bastrom; C. Douglas Wallace; Peter O. Newton



Theoretical assessment of an intramedullary condylar component versus screw fixation for the condylar component of a hemiarthroplasty alloplastic TMJ replacement system.  


Virtual design gives flexibility to explore constructive solutions or structures. It enables analysis that would often be impossible even if expensive real prototypes were available. Simulations using finite element models allow access to the stress and strain tensor or to the deformation tensor within an implant or a tissue which is impossible experimentally, even in vitro. This study is based on two numerical models of temporomandibular joint (TMJ) implants, comparing two bone-implant connections: an external connection performed with surgical screws (commercial model) and an internal connection carried out by penetration into the intramedullary space. The finite element models were constructed based on a cadaveric mandible and considering the five principal muscles in action. Strain distributions into the surrounding bone tissue are analysed and in both models they show significant differences at the external surface of the mandible in displacements. However, while the intramedullary fixation increases strains in the cancellous tissue, the study shows that strain distribution is mainly influenced by the number and distribution of screws in commercial solution. PMID:23684530

Ramos, A; Mesnard, M; Relvas, C; Completo, A; Simões, J A



Proximal metatarsal osteotomy for hallux valgus: an audit of radiologic outcome after single screw fixation and full postoperative weightbearing.  


BACKGROUND: Proximal metatarsal osteotomy combined with a distal soft-tissue procedure is a common treatment for moderate to severe hallux valgus. Secure stabilisation of the metatarsal osteotomy is necessary to avoid complications such as delayed union, nonunion or malunion as well as loss of correction. The aim of this study was to report our results using a single screw for stabilisation of the osteotomy. METHODS: We retrospectively reviewed 151 patients with severe hallux valgus who were treated by the above mentioned way with full postoperative weightbearing in a stiff soled shoe. Mean age of patients at time of surgery was 54 years, 19 patients were male and 132 female. Assessment of clinical and radiographic results was performed after 2 days and 6 weeks. Results were also correlated to the experience of the performing surgeon. RESULTS: Mean preoperative HVA (hallux valgus angle) was 36.4 degrees, and then 3.5 degrees 2 days and 13.4 degrees 6 weeks after the procedure (p < 0.001). Mean preoperative IMA (intermetarsal angle) was 16.8 degrees, and then 6.4 degrees after 2 days and 9.8 degrees after 6 weeks (p < 0.001). Mean preoperative first metatarsal length of 56.4 mm decreased to 53.6 mm after 6 weeks. Possible non-union of the osteotomy was observed in 4 patients (2.6%) after 6 weeks. Performing residents (n = 40) operated in 65 minutes and attending surgeons (n = 111) in 45 minutes, with no significant differences in radiographic measurements between both groups. CONCLUSIONS: Single screw stabilisation of proximal chevron osteotomy is a reliable method for treating severe hallux valgus deformities with satisfactory results. PMID:23725485

Mittag, Falk; Leichtle, Ulf; Meisner, Christoph; Ipach, Ingmar; Wülker, Nikolaus; Wünschel, Markus



[Comparison of the Ender's nailing and Dynamic Hip Screw (DHS) fixation in the treatment of trochanteric fractures in elderly patients].  


The aim of this study was an evaluation which operative method of treatment: stabilisation with the Dynamic Hip Screw or with Ender's nails is less invasive procedure in elderly patients with trochanteric fractures. 100 consecutive patients with trochanteric fracture were enrolled into the study, of which 53 patients (49 women, 4 men; mean age 89 years) were stabilised intramedullarily with the use of Ender's nails and 47 patients (26 women, 21 men; mean age 76 years) were treated operatively with the use of Dynamic Hip Screw. The factors compared the mean length of hospital stay, the mean duration of the surgery, post-operative blood loss, early local and general complication rate and mortality in both groups. We took into account their general health and coexisting illnesses according to the American Society of Anesthesiologists (ASA) classification, type of fracture according to AO and Evan's classifications and the surgeon's experience. The mean duration of the surgery was 27 minutes longer in the case of DHS stabilisation. The complication rate was higher and the mean length of postoperative hospital stay was longer after Ender nailing. The mean blood loss: the drop in Red Blood Cells (RBC), Haematocrit (Ht) and the Mean Haemoglobin Concentration (Hb) was also higher in patients treated with the use of Ender nails. The mean rate of blood units that had to be transfused postoperatively was also higher in "Ender" group. The difference was statistically significant, especially in the group of patients treated as emergency procedure at the day of admission (p < 0.05). The operative treatment of trochanteric fractures in elderly patients with the use of DHS device showed to be a less invasive procedure in comparison to Ender nailing. In conclusion, the indications for this method of trochanteric fractures' treatment should be expanded, especially in the case of unstable fractures. PMID:17455526

Sliwka, Andrzej; Zgoda, Marcin; Górski, Rados?aw; Purski, Karol; Wasilewski, Piotr; Górecki, Andrzej




PubMed Central

Objective To evaluate the clinical performance of the Dynamic Helical Hip System (DHHS) spiral blade relative to the Dynamic Hip Screw (DHS) lag screw. Design Randomized prospective study. Setting One level-2 trauma center and one level-3 trauma center. Patients Fifty-one consecutive patients were recruited into the trial. Inclusion criteria included patients over 50 years of age with AO/OTA 31A1 or 31A2 fracture. Intervention Surgeries were performed by one of 15 participating community orthopaedic surgeons. The patients were randomized to either a DHHS or DHS implant. Follow-up occurred at two weeks and six weeks and then at six-week intervals until healing occurred. Main Outcome Measures Primary outcome variables included sliding of die implant on the final AP radiographs, failure by cut-out and implant failure. Results There were 24 patients in the DHS group and 27 in the DHHS group. There was no difference in age, gender, ASA score, fracture classification or in the quality of reduction measured on the immediate postoperative radiographs (p=0.28) between the two groups. The tip apex distance was 18.7 mm in the DHHS group and 18.5 mm in the DHS group (p=0.40). The DHHS group had average blade sliding of 7.4 mm while the DHS group had an average lag-screw sliding of 7.7 (p=0.45). The DHHS group had two failures by central protrusion of the blade through the femoral head without significant varus collapse or superior migration. One was revised to a DHS and healed, the other was revised to a proximal femoral locking plate, which also failed and eventually required revision to a total hip arthroplasty. Investigation of the implants post failure showed evidence of binding of the blade shaft in the barrel as a mechanism of failure in both cases. No DHS implants cut out in this series, although one patient was revised to a total hip arthroplasty for symptomatic segmental osteonecrosis. Conclusion Both implants performed well in a majority of cases. The higher incidence of failure in the DHHS group is concerning, despite the low numbers. The mechanism of failure of the DHHS implant left adequate bone stock for attempts at revision fixation.

Fitzpatrick, Daniel C; Sheerin, Daniel V; Wolf, Brian R; Wuest, Thomas K



Coracoid bone graft osteolysis after Latarjet procedure: A comparison study between two screws standard technique vs mini-plate fixation  

PubMed Central

Aims: One of the reason for Latarjet procedure failure may be coracoid graft osteolysis. In this study, we aimed to understand if a better compression between the coracoid process and the glenoid, using a mini-plate fixation during the Latarjet procedure, could reduce the amount of coracoid graft osteolysis. Materials and Methods: A computed tomography scan analysis of 26 prospectively followed-up patients was conducted after modified Latarjet procedure using mini-plate fixation technique to determine both the location and the amount of coracoid graft osteolysis in them. We then compared our current results with results from that of our previous study without using mini-plate fixation to determine if there is any statistical significant difference in terms of corcacoid bone graft osteolysis between the two surgical techniques. Results: The most relevant osteolysis was represented by the superficial part of the proximal coracoid, whereas the deep part of the proximal coracoid graft is least involved in osteolysis and has best bone healing. The current study showed a significant difference only for the deep part of the distal coracoid with our previous study (P < 0.01). Discussion: To our knowledge, there are no studies in literature that show the causes of coracoid bone graft osteolysis after Latarjet procedure. Conclusion: Our study suggests that there is a significant difference only for the deep part of the distal coracoid in terms of osteolysis. At clinical examination, this difference did not correspond with any clinical findings. Level of Evidence: Level 4. Clinical Relevance: Prospective case series, Treatment study.

Giacomo, Giovanni Di; Costantini, Alberto; de Gasperis, Nicola; De Vita, Andrea; Lin, Bernard K. H.; Francone, Marco; Beccaglia, Mario A. Rojas; Mastantuono, Marco



A case of hypertrophic ischial tuberosity non-union treated by closed wedge osteotomy and plate and screws fixation.  


We report a case of a 21-year-old male with massive hypertrophic ischial tuberosity non-union. Among multiple other lesions, the patient suffered an open avulsion of the ischial tuberosity in a severe traffic accident in adolescence. A conservative treatment was decided for the avulsion. Because of sciatic pain and difficulties while sitting since the age of 19, X-rays were realised and showed a massive hypertrophic non-union of the ischial tuberosity. To preserve hamstring origin with bone attachment, the non-union was mobilised, reduced by osteotomy and fixed by plate and screws. At the follow up of one year, the patient sits without pain and can work without interruption. Avulsion of the ischial tuberosity is infrequent and the diagnosis is often missed (Gidwani et al., BMJ 329:99-100, 2004; Hamada, Clin Orthop 31:117-130, 1963). This lesion is more often seen in adolescence as the consequence of a sport injury (Gidwani et al., BMJ 329:99-100, 2004). Treatment is generally conservative and outcome good. Surgical therapy is only needed in cases with severe displacement. Long-term problems are seldom and surgical therapy to solve these problems is the exception. PMID:23411936

Putman, S; Rommens, P M



New means in spinal pedicle hook fixation  

Microsoft Academic Search

Pedicle hooks which are used as an anchorage for posterior spinal instrumentation may be subjected to considerable three-dimensional forces. In order to achieve stronger attachment to the implantation site, hooks using screws for additional fixation have been developed. The failure loads and mechanisms of three such devices have been experimentally determined on human thoracic vertebrae: the Universal Spine System (USS)

U. Berlemann; P. Cripton; L.-P. Nolte; K. Lippuner; F. Schläpfer



Strong stimulation of N2 fixation in oligotrophic Mediterranean Sea: results from dust addition in large in situ mesocosms  

NASA Astrophysics Data System (ADS)

The response of N2 fixation to contrasted (wet and dry) Saharan dust deposition was studied in the framework of the DUNE project "a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem" during which realistic simulations of dust deposition (10 g madditions were conducted in June 2008 (DUNE-1-P: simulation of a wet deposition, DUNE-1-Q: simulation of a dry deposition) and 2010 (DUNE-2-R: simulation of successive wet depositions) in the north western oligotrophic Mediterranean Sea. Here we show that wet and dry dust deposition induced a rapid (24 h or 48 h after dust additions), strong (2- to 5.3-fold) and long (4 to 6 days duration) increase in N2 fixation indicating that both wet and dry Saharan dust depositions were able to relieve efficiently the nutrient limitation(s) of N2 fixation. This means in particular that N2 fixation activity was not inhibited by the NO3- input associated with the simulated wet deposition. The contribution of N2 fixation to primary production was negligible before (on average 0.4%) and after (on average 1%) dust additions in all experiments indicating that N2 fixation was a poor contributor to the N demand for primary production. Before seedings, new production (NP) was mainly supported by NO3- as a source of N as shown by the low contribution of N2 fixation to NP (on average 3%). Despite the stimulation of N2 fixation by dust, the rates remained low, and did not allow to significantly change the contribution of N2 fixation to NP as a maximum of 10% contribution was evidenced. A comparison of the responses of N2 fixation by diazotrophs and CO2 fixation by the whole phytoplankton community suggests that those metabolic processes were limited or co-limited by different nutrients. The estimated input of new nitrogen (NO3-) from simulated wet deposition was much higher than that associated with N2 fixation. We confirm that although the biogeochemical impact of N2 fixation seems negligible in the oligotrophic waters of the western Mediterranean Sea, Saharan dust pulses by bringing new nutrients represent a key controlling factor of the magnitude of N2 fixation rate in the Mediterranean Sea and potentially in all LNLC areas impacted by dust deposition such as the tropical Atlantic and Pacific Oceans.

Ridame, C.; Guieu, C.; L'Helguen, S.



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



Distal interlocking screws with a modular revision stem for revision total hip arthroplasty in severe bone defects.  


A prospective study of 15 patients was designed to examine whether the modular cementless revision stem (Revitan curved; Zimmer GmbH, Winterthur, Switzerland) is suitable for stem revisions with a defective isthmus when distal interlocking screws are also used for fixation. During a follow-up period of 35.4 +/- 11.4 months (24-70 months), there was one stem loosening with screw breakage in a case of a stem that was too thin. According to Engh et al, bony ingrowth fixation of the stem occurred in 12 cases and stable fibrous fixation in 2 cases. The Harris Hip Score rose continuously from 44.7 +/- 12.9 points preoperatively to 75 +/- 10 points at 24 months. This concept of additional stem fixation with distal interlocking screws represents a useful treatment option for revision arthroplasty in rare cases of a defective isthmus. PMID:19577879

Fink, Bernd; Grossmann, Alexandra; Fuerst, Martin



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


An S-2 alar iliac pelvic fixation. Technical note.  


Multiple techniques of pelvic fixation exist. Distal fixation to the pelvis is crucial for spinal deformity surgery. Fixation techniques such as transiliac bars, iliac bolts, and iliosacral screws are commonly used, but these techniques may require separate incisions for placement, leading to potential wound complications and increased dissection. Additionally, the use of transverse connector bars is almost always necessary with these techniques, as their placement is not in line with the S-1 pedicle screw and cephalad instrumentation. The S-2 alar iliac pelvic fixation is a newer technique that has been developed to address some of these issues. It is an in-line technique that can be placed during an open procedure or percutaneously. PMID:20192658

Matteini, Lauren E; Kebaish, Khaled M; Volk, W Robert; Bergin, Patrick F; Yu, Warren D; O'Brien, Joseph R



Single column locking plate fixation is inadequate in two column acetabular fractures. A biomechanical analysis  

PubMed Central

Background The objective of this study was to determine whether one can achieve stable fixation of a two column (transverse) acetabular fracture by only fixing a single column with a locking plate and unicortical locking screws. We hypothesized that a locking plate applied to the anterior column of a transverse acetabular fracture would create a construct that is more rigid than a non-locking plate, and that this construct would be biomechanically comparable to two column fixation. Methods Using urethane foam models of the pelvis, we simulated transverse acetabular fractures and stabilized them with 1) an anterior column plate with bicortical screws, 2) an anterior locking plate with unicortical screws, 3) an anterior plate and posterior column lag screw, and 4) a posterior plate with an anterior column lag screw. These constructs were mechanically loaded on a servohydraulic material testing machine. Construct stiffness and fracture displacement were measured. Result and Discussion We found that two column fixation is 54% stiffer than a single column fixation with a conventional plate with bicortical screws. There was no significant difference between fixation with an anterior column locking plate with unicortical screws and an anterior plate with posterior column lag screw. We detected a non-significant trend towards more stiffness for the anterior locking plate compared to the anterior non-locking plate. Conclusion In conclusion, a locking plate construct of the anterior column provides less stability than a traditional both column construct with posterior plate and anterior column lag screw. However, the locking construct offers greater strength than a non-locking, bicortical construct, which in addition often requires extensive contouring and its application is oftentimes accompanied by the risk of neurovascular damage.



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



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



Serial Magnetic Resonance Imaging Evaluation of Operative Site After Fixation of Patellar Tendon Graft With Bioabsorbable Interference Screws in Anterior Cruciate Ligament Reconstruction  

Microsoft Academic Search

Summary: Magnetic resonance imaging (MRI) is accepted as the imaging procedure of choice for showing internal derangement of the knee. In contrast to metal implants, bioabsorbable interference screws do not produce an artifact and provide an opportunity to expand the evaluation of the postoperative anterior cruciate ligament (ACL) ligament repair. There is the potential to evaluate the implant, the graft,

Georg Lajtai; Irene Noszian; Klaus Humer; Franz Unger; Gernot Aitzetmüller; Ernst Orthner



Malpractice of Epiphyseal Cannulated Screw Fixation in a Child with Avulsion Fracture of the Tibial Eminence Complicating with Lack of Knee Extension and Distal Femoral Fracture  

Microsoft Academic Search

Avulsion fracture of the tibial eminence is rare in children. This report describes a case of a 9-year -old boy who had been treated previously with an epiphyseal cannulated screw and washer , but without notchplasty , for an avulsion fracture of the tibial eminence. The patient subsequently presented with extension block and knee stif fness. After removal of the

Tsung-Ying Tsai; Jen-Huei Chang; Yu-Kai Yeh; Fu-Kai Chuang; Che-Wei Liu; Shyu-Jye Wang


Femoral fracture following knee ligament reconstruction surgery due to an unpredictable complication of bioabsorbable screw fixation: a case report and review of literature  

Microsoft Academic Search

We report an unusual case of femoral fracture from minimal trauma, due to the rapid disappearance of a bioabsorbable interference\\u000a screw used for reconstruction of the posterolateral corner of the knee. The literature on bone tunnel fractures following\\u000a knee ligament reconstruction surgery is also reviewed.

Sujith Konan; Fares Sami Haddad



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



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



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



Transsacral fixation for failed posterior fixation of the pelvic ring  

Microsoft Academic Search

Introduction: In the treatment of certain pelvic ring pathologies (non-unions and failure of ilio-sacral screw fixation) trans-sacral\\u000a fixation (i.e. fixation from iliac wing to the other traversing the body of S1) may be necessary. The purpose of our study\\u000a was to describe our early experience and describe the surgical technique. Materials and methods: Seven cases of trans-sacral fixation were identified

Paul E. Beaulé; John Antoniades; Joel M. Matta



Biomechanical optimization of different fixation modes for a proximal femoral L-osteotomy  

PubMed Central

Background Numerous proposed surgical techniques have had minimal success in managing greater trochanter overgrowth secondary to retarded growth of the femoral capital epiphysis. For reconstruction of residual hip deformities, a novel type of proximal femur L-osteotomy was performed with satisfactory results. Although the clinical outcome was good, the biomechanical characteristics of the femur after such an osteotomy have not been clearly elucidated. Therefore, this study presents a three dimensional finite element analysis designed to understand the mechanical characteristics of the femur after the L-osteotomy. Methods A patient with left hip dysplasia was recruited as the study model for L-osteotomy. The normal right hip was used as a reference for performing the corrective surgery. Four FEA models were constructed using different numbers of fixation screws but the same osteotomy lengths together with four FEA models with the same number of fixation screws but different osteotomy lengths. The von Mises stress distributions and femoral head displacements were analyzed and compared. Results The results revealed the following: 1). The fixation devices (plate and screws) sustained most of the external loading, and the peak value of von Mises stress on the fixation screws decreased with an increasing number of screws. 2). Additional screws are more beneficial on the proximal segment than on the distal segment for improving the stability of the postoperative femur. 3). The extent of osteotomy should be limited because local stress might be concentrated in the femoral neck region with increasing length of the L-osteotomy. Conclusion Additional screw placement on the proximal segment improves stability in the postoperative femur. The cobra-type plate with additional screw holes in the proximal area might improve the effectiveness of L-osteotomies.

Tai, Ching-Lung; Chen, Weng-Pin; Chen, Hsih-Hao; Lin, Chien-Yu; Lee, Mel S



Fixation of periprosthetic femoral shaft fractures occurring at the tip of the stem  

Microsoft Academic Search

This study evaluated 5 currently used periprosthetic femoral shaft fracture fixation techniques to determine which technique provided the greatest fixation stability. Periprosthetic fractures in 30 synthetic femurs were fixed with a plate with cables, plate with proximal cables and distal bicortical screws (Ogden concept), plate with proximal unicortical screws and distal bicortical screws, plate with proximal unicortical screws and cables

Michael G Dennis; Jordan A Simon; Frederick J Kummer; Kenneth J Koval; Paul E DiCesare



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



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



Biological fixation of endosseous implants  

Microsoft Academic Search

Primary implant stability is ensured by a mechanical fixation of implants. However, during implant healing a biological anchorage is necessary to achieve final osseointegration.Aim of this study was to investigate the histological aspects of biological fixation around titanium screws.Forty-eight titanium screws with different surfaces (smooth, plasma sprayed, sand blasted) were inserted in tibiae and femura of sheep and analyzed by

M. Franchi; M. Fini; D. Martini; E. Orsini; L. Leonardi; A. Ruggeri; G. Giavaresi; V. Ottani



Bioabsorbable interference screw fixation of distal biceps ruptures through a single anterior incision: a single-surgeon case series and review of the literature  

Microsoft Academic Search

Introduction  We present a single-surgeon series of 14 acute ruptured distal biceps tendons repaired using a biotenodesis screw through\\u000a a single anterior incision.\\u000a \\u000a \\u000a \\u000a \\u000a Patients  The demographics of this population reveal a typical injury pattern and reflect the preponderance of distal biceps ruptures\\u000a in the middle aged, active male. Goniometric post-operative assessment of flexion, pronation and supination range demonstrates\\u000a excellent clinical function in

Will G. P. Eardley; Saurabh Odak; T. Simon Adesina; Richard P. Jeavons; Jim L. McVie



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



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



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



Evaluation the treatment outcomes of intracapsular femoral neck fractures with closed or open reduction and internal fixation by screw in 18-50-year-old patients in Isfahan from Nov 2010 to Nov 2011  

PubMed Central

Background: There is conflict of interest in the treatment of intracapsular femoral neck fractures and the outcomes. The aim of this study was evaluation the treatment outcomes of closed and open reduction and internal fixation with screw in 18–50-year-old patients. Materials and Methods: This clinical randomized study was conducted in Ayatollah Kashani Center in Isfahan from Nov 2010 to Nov 2011. In 42 patients selected in a randomized manner, fractures were reduced by closed reduction or open if necessary and C-ARM was controlled in AP and lateral plans. Movement range and femur pain severity were evaluated according to Visual analogue Scale (VAS) score at 3 and 6 months after surgery. Data were analyzed by SPSS 18. Chi-square, t-test, one-way analysis of variance (ANOVA), and descriptive statistics such as frequency distribution, mean, and mean deviation were used. Results: Forty-two patients with femoral neck fracture were treated by open [31 patients (73.8%)] or closed reduction [11 patients (26.2%)] and also osteosynthesis. Their mean age was 47.3 ± 9.8 years; 29 of them were males and 13 were females. Twelve patients had bad range of motion (ROM) (28.6%), 16 had intermediate ROM (38%), and 14 had good ROM (33.4%). After 6 months, 12 patients (28.6%) had bad ROM, 10 (23.8%) had intermediate ROM, and 20 (47.6%) had good ROM. There were 11 cases of non-union (35.5%) in the open reduction group and 4 in the closed group. Conclusion: This study showed that femoral neck fracture is associated with several complications, especially if open reduction was necessary. So, the surgical method and necessary equipments such as radiolucent bed, C-ARM machine, and implant cannulated screw set should be considered.

Javdan, Mohammad; Bahadori, Mehran; Hosseini, Alireza



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



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



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


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



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



Hybrid fixation: evaluation of a novel technique in adult osteochondritis dissecans of the knee  

Microsoft Academic Search

Purpose  Treatment of osteochondritis dissecans of the adult knee requires bone and cartilage integration of the loose fragment. Screw\\u000a fixation provides primary stability but does not guarantee bony consolidation. Additional biological fixation using osteochondral\\u000a grafts—hybrid fixation—could improve fragment integration.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  The study included seven patients [median age 21 years (15–29)] who underwent surgery for Bedouelle IIB or III osteochondritis\\u000a dissecans of the medial

Francois Lintz; Nicolas Pujol; Christophe Pandeirada; Philippe Boisrenoult; Philippe Beaufils



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



Dynamic simulations of cancellous bone resorption around orthopaedic fixative implants  

Microsoft Academic Search

Progressive loosening of bone fixation screws is a well-documented phenomenon, induced by stress shielding and subsequent adaptive bone remodeling which results in bone loss around the screw. A set of two-dimensional computational (finite element) models was developed In order to test the effect of various screw profiles on the predicted extent of bone resorption. An algorithm simulating local bone adaptation

A. Gefen



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



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



The asymptomatic contralateral hip in unilateral slipped capital femoral epiphysis: morbidity of prophylactic fixation.  


Prophylactic contralateral fixation in unilateral slipped capital femoral epiphysis (SCFE) remains a controversial issue. In this study, 66 patients treated for unilateral SCFE (July 1997-April 2009) were screened for complications with need for surgical reintervention in the asymptomatic contralateral hip. Except for one patient, prophylactic fixation was performed in all cases. Major complications such as avascular necrosis were not seen; minor complications such as wound revision occurred in 4.6% (three of 65). In 16.9% (11/65) secondary loss of fixation with need for second fixation occurred. As the need for second fixation arose mostly bilaterally (10.7%, 7/65), only four patients (6.2%) required an additional surgical procedure for second fixation. Children who needed second fixation were significantly younger (11.8 years) than those who did not (13.1 years, P=0.013). In conclusion, this retrospective analysis shows that prophylactic contralateral fixation in SCFE is a safe procedure with no major complications and an acceptable rate of minor complications. When Kirschner wires are used for prophylactic pinning, there is a possibility of secondary loss of fixation due to length growth at the level of the physis. To avoid the need for secondary fixation, screw epiphysiodesis might be considered. PMID:22406770

Woelfle, Julia V; Fraitzl, Christian R; Reichel, Heiko; Nelitz, Manfred



Coralline hydroxyapatite granules inferior to morselized allograft around uncemented porous Ti implants: unchanged fixation by addition of concentrated autologous bone marrow aspirate.  


We compared early fixation of titanium implants grafted with impacted allograft bone or coralline hydroxyapatite (HA) granules (Pro Osteon 200) with and without the addition of concentrated bone marrow cells (BMC). Autologous bone marrow aspirate was centrifuged to increase the BMC concentration. Four nonloaded cylindrical, porous coated titanium implants with a circumferential gap of 2.3 mm were inserted in the proximal humeri of eight dogs. Coralline HA granules +/- BMC were impacted around the two implants on one side, and allograft +/- BMC was impacted around the contra lateral implants. Observation time was 4 weeks. The implants surrounded by allograft bone had a three-fold better fixation than the HA-grafted implants. The concentration of BMC after centrifugation was increased with a factor 2.1. The addition of BMC to either of the bone graft materials had no statistically significant effects on implant fixation. The allografted implants were well osseointegrated, whereas the HA-grafted implants were largely encapsulated in fibrous tissue. The addition of concentrated autologous BMCs to the graft material had no effect on implant fixation. The HA-grafted implants were poorly anchored compared with allografted implants, suggesting that coralline HA granules should be considered a bone graft extender rather than a bone graft substitute. PMID:21793192

Baas, Jorgen; Svaneby, Dea; Jensen, Thomas Bo; Elmengaard, Brian; Bechtold, Joan; Soballe, Kjeld



Relative strength of tailor's bunion osteotomies and fixation techniques.  


A paucity of data is available on the mechanical strength of fifth metatarsal osteotomies. The present study was designed to provide that information. Five osteotomies were mechanically tested to failure using a materials testing machine and compared with an intact fifth metatarsal using a hollow saw bone model with a sample size of 10 for each construct. The osteotomies tested were the distal reverse chevron fixated with a Kirschner wire, the long plantar reverse chevron osteotomy fixated with 2 screws, a mid-diaphyseal sagittal plane osteotomy fixated with 2 screws, the mid-diaphyseal sagittal plane osteotomy fixated with 2 screws, and an additional cerclage wire and a transverse closing wedge osteotomy fixated with a box wire technique. Analysis of variance was performed, resulting in a statistically significant difference among the data at p <.0001. The Tukey-Kramer honestly significant difference with least significant differences was performed post hoc to separate out the pairs at a minimum ? of 0.05. The chevron was statistically the strongest construct at 130 N, followed by the long plantar osteotomy at 78 N. The chevron compared well with the control at 114 N, and they both fractured at the proximal model to fixture interface. The other osteotomies were statistically and significantly weaker than both the chevron and the long plantar constructs, with no statistically significant difference among them at 36, 39, and 48 N. In conclusion, the chevron osteotomy was superior in strength to the sagittal and transverse plane osteotomies and similar in strength and failure to the intact model. PMID:23103076

Haddon, Todd B; LaPointe, Stephan J



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



High speed fracture fixation: assessing resulting fixation stability and fastener withdrawal strength.  


A new method of bone fracture fixation has been developed in which fixation darts (small diameter nails/pins) are driven across a fracture site at high velocity with a pneumatically powered gun. When fixation darts are inserted oblique to one another, kinematic constraints prevent fragment motion and allow bone healing to progress. The primary aim of this study is to determine if fixation darts can provide reasonable fixation stability compared to bone screws, which were used as a benchmark since they represent a simple, yet well-established, surgical technique. The first objective was to evaluate macro-level stability using different numbers of darts inserted parallel and oblique to each other; experimental comparisons were undertaken in a bone analog model. Experimental results showed fixation darts could not be substituted for screws on a one-to-one basis, but that a plurality of fixation darts provided comparable fixation to two bone screws while allowing for faster insertion and damaging less bone. A second objective was to evaluate micro-level stability; a finite element model was created in order to provide a detailed look at the stress state surrounding the fixation darts and the evolution of the fracture gap. Even with relatively weak fixation dart configurations, the fracture gap was maintained below physiological thresholds for bone healing. Most failures of the fixed fractures were attributed to fixation dart pullout from the cancellous structure. The final objective of the study was to characterize this mode of failure with separate fixation dart and screw pullout tests conducted in Sawbones® cancellous foam and fresh porcine cancellous bone. The results showed that the cancellous foam was an acceptable substitute for real bone and provided a conservative estimate of the fixation darts' performance relative to bone screws. A final comparison between experimental and numerically predicted pullout strengths provided confirmation that the model and experiments were consistent. PMID:23722627

Prygoski, Matthew Philip; Sanchez Caballero, Samuel; Schmid, Steven R; Lozier, Antony J; Selles, Miguel Angel



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



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

Microsoft Academic Search

Current fixation techniques in medial knee reconstructions predominantly utilize interference screws alone for soft tissue\\u000a graft fixation. The use of concurrent fixation techniques as part of a hybrid fixation technique has also been suggested to\\u000a strengthen soft tissue fixation, although these hybrid fixation techniques have not been biomechanically validated. The purpose\\u000a was to biomechanically evaluate two distal tibial superficial MCL

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



Two potential causes of EPL rupture after distal radius volar plate fixation.  


Rupture of the extensor pollicis longus tendon can occur after volar plate fixation of dorsally comminuted distal radius fractures. We attempted to identify the etiology of extensor pollicis longus tendon injury after volar plate fixation of the distal radius and potential solutions to this problem. After describing two case reports, we examine six cadaveric specimens and retrospectively review 10 selected patients to evaluate possible technique refinements to minimize damage to the extensor pollicis longus tendon during volar plating of the distal radius. We identify specific screw holes in three commercially available volar distal radius plates that direct the drill bit or prominent screw tips into the third extensor compartment. In addition, after reduction and plate fixation, bone fragments or dorsal gapping may predispose the extensor pollicis longus tendon to injury. We recommend either using shorter screw lengths or leaving the implicated plate holes unfilled. In addition, we suggest consideration of an open assessment of the third extensor compartment, if indicated, as performed through a small dorsal incision ulnar to Lister's tubercle. PMID:16770281

Benson, Eric C; DeCarvalho, Alex; Mikola, Elizabeth A; Veitch, John M; Moneim, Moheb S



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



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


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



Percutaneous computer-assisted translaminar facet screw: an initial human cadaveric study  

Microsoft Academic Search

Background contextTranslaminar facet screws are a minimally invasive technique for posterior lumbar fixation with good success rates. Computer-assisted image navigation using virtual fluoroscopy allows multiple simultaneous screens in various planes to plan and drive spinal instrumentation.

Rick C. Sasso; Natalie M. Best; Eric A. Potts



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



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



Dynesys fixation for lumbar spine degeneration  

Microsoft Academic Search

The dynamic fixation system Dynesys is utilized in the last 10 years for treatment of degenerative segmental disease of the\\u000a lumbar spine. Dynesys is a semi-rigid fixation system that allows minimal lengthening and shortening between two segmental\\u000a pedicle screws as opposed to a rigid metal bar. Thus, the system is regarded to maintain stability and near physiological\\u000a motion patterns of the

Matthias Bothmann; Erich Kast; Gerald Jens Boldt; Joachim Oberle



Effects of elevated CO2 and N addition on growth and N2 fixation of a legume subshrub (Caragana microphylla Lam.) in temperate grassland in China.  


It is well demonstrated that the responses of plants to elevated atmospheric CO(2) concentration are species-specific and dependent on environmental conditions. We investigated the responses of a subshrub legume species, Caragana microphylla Lam., to elevated CO(2) and nitrogen (N) addition using open-top chambers in a semiarid temperate grassland in northern China for three years. Measured variables include leaf photosynthetic rate, shoot biomass, root biomass, symbiotic nitrogenase activity, and leaf N content. Symbiotic nitrogenase activity was determined by the C(2)H(2) reduction method. Elevated CO(2) enhanced photosynthesis and shoot biomass by 83% and 25%, respectively, and the enhancement of shoot biomass was significant only at a high N concentration. In addition, the photosynthetic capacity of C. microphylla did not show down-regulation under elevated CO(2). Elevated CO(2) had no significant effect on root biomass, symbiotic nitrogenase activity and leaf N content. Under elevated CO(2), N addition stimulated photosynthesis and shoot biomass. By contrast, N addition strongly inhibited symbiotic nitrogenase activity and slightly increased leaf N content of C. microphylla under both CO(2) levels, and had no significant effect on root biomass. The effect of elevated CO(2) and N addition on C. microphylla did not show interannual variation, except for the effect of N addition on leaf N content. These results indicate that shoot growth of C. microphylla is more sensitive to elevated CO(2) than is root growth. The stimulation of shoot growth of C. microphylla under elevated CO(2) or N addition is not associated with changes in N(2)-fixation. Additionally, elevated CO(2) and N addition interacted to affect shoot growth of C. microphylla with a stimulatory effect occurring only under combination of these two factors. PMID:22046376

Zhang, Lin; Wu, Dongxiu; Shi, Huiqiu; Zhang, Canjuan; Zhan, Xiaoyun; Zhou, Shuangxi



Intraprosthetic fixation techniques in the treatment of periprosthetic fractures-A biomechanical study  

PubMed Central

AIM: To develop new fixation techniques for the treatment of periprosthetic fractures using intraprosthetic screw fixation with inserted threaded liners. METHODS: A Vancouver B1 periprosthetic fracture was simulated in femur prosthesis constructs using sawbones and cemented regular straight hip stems. Fixation was then performed with either unicortical locked-screw plating using the less invasive stabilization system-plate or with intraprosthetic screw fixation using inserted liners. Two experimental groups were formed using either prostheses made of titanium alloy or prostheses made of cobalt chrome alloy. Fixation stability was compared in an axial load-to-failure model. Drilling was performed using a specially invented prosthesis drill with constantly applied internal cooling. RESULTS: The intraprosthetic fixation model with titanium prostheses was superior to the unicortical locked-screw fixation in all tested devices. The intraprosthetic fixation model required 10 456 N ± 1892 N for failure and the unicortical locked-screw plating required 7649 N ± 653 N (P < 0.05). There was no significant difference between the second experimental group and the control group. CONCLUSION: Intraprosthetic screw anchorage with special threaded liners enhances the primary stability in treating periprosthetic fractures by internal fixation.

Brand, Stephan; Klotz, Johannes; Hassel, Thomas; Petri, Maximilian; Haasper, Carl; Bach, Friedrich-Wilhelm; Krettek, Christian; Goesling, Thomas



Treatment of complex proximal interphalangeal joint fractures using a new dynamic external fixator: 15 cases.  


The management of proximal interphalangeal joint fractures of the fingers is difficult. Dynamic traction splinting systems are cumbersome and the Suzuki fixator does not prevent secondary fracture displacement. Fifteen cases were treated with a new dynamic external fixator with distraction, the Ligamentotaxor. In two cases, additional fixation was required with a screw. After 10 months, grip strength scored 85.7% compared with the contralateral hand, flexion achieved 76.3 degrees and the extension deficit was 19.6 degrees . The visual analogical scale pain level (VAS) was 1.9 and the Quick DASH score totalled 16.9. Revision treatment was needed for sepsis for one patient. A case of secondary fracture displacement was corrected in the outpatient clinic. Consolidation was achieved in all cases. In conclusion, despite imperfect outcomes for these complex fractures, we believe that the Ligamentotaxor technique is useful. PMID:19362033

Körting, O; Facca, S; Diaconu, M; Liverneaux, P



SOS and UVM Pathways Have Lesion-Specific Additive and Competing Effects on Mutation Fixation at Replication-Blocking DNA Lesions  

PubMed Central

Escherichia coli cells have multiple mutagenic pathways that are induced in response to environmental and physiological stimuli. Unlike the well-investigated classical SOS response, little is known about newly recognized pathways such as the UVM (UV modulation of mutagenesis) response. In this study, we compared the contributions of the SOS and UVM pathways on mutation fixation at two representative noninstructive DNA lesions: 3,N4-ethenocytosine (?C) and abasic (AP) sites. Because both SOS and UVM responses are induced by DNA damage, and defined UVM-defective E. coli strains are not yet available, we first constructed strains in which expression of the SOS mutagenesis proteins UmuD? and UmuC (and also RecA in some cases) is uncoupled from DNA damage by being placed under the control of a heterologous lac-derived promoter. M13 single-stranded viral DNA bearing site-specific lesions was transfected into cells induced for the SOS or UVM pathway. Survival effects were determined from transfection efficiency, and mutation fixation at the lesion was analyzed by a quantitative multiplex sequence analysis procedure. Our results suggest that induction of the SOS pathway can independently elevate mutagenesis at both lesions, whereas the UVM pathway significantly elevates mutagenesis at ?C in an SOS-independent fashion and at AP sites in an SOS-dependent fashion. Although mutagenesis at ?C appears to be elevated by the induction of either the SOS or the UVM pathway, the mutational specificity profiles for ?C under SOS and UVM pathways are distinct. Interestingly, when both pathways are active, the UVM effect appears to predominate over the SOS effect on mutagenesis at ?C, but the total mutation frequency is significantly increased over that observed when each pathway is individually induced. These observations suggest that the UVM response affects mutagenesis not only at class 2 noninstructive lesions (?C) but also at classical SOS-dependent (class 1) lesions such as AP sites. Our results add new layers of complexity to inducible mutagenic phenomena: DNA damage activates multiple pathways that have lesion-specific additive as well as suppressive effects on mutation fixation, and some of these pathways are not directly regulated by the SOS genetic network.

Rahman, M. Sayeedur; Humayun, M. Zafri



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.



Guide to radiation fixatives  

SciTech Connect

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

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



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



Preliminary experience with biodegradable implants for fracture fixation  

PubMed Central

Background: Biodegradable implants were designed to overcome the disadvantages of metal-based internal fixation devices. Although they have been in use for four decades internationally, many surgeons in India continue to be skeptical about the mechanical strength of biodegradable implants, hence this study. Materials and Methods: A prospective study was done to assess the feasibility and surgeon confidence level with biodegradable implants over a 12-month period in an Indian hospital. Fifteen fractures (intra-articular, metaphyseal or small bone fractures) were fixed with biodegradable implants. The surgeries were randomly scheduled so that different surgeons with different levels of experience could use the implants for fixation. Results: Three fractures (one humeral condyle, two capitulum), were supplemented by additional K-wires fixation. Trans-articular fixator was applied in two distal radius and two pilon fractures where bio-pins alone were used. All fractures united, but in two cases the fracture displaced partially during the healing phase; one fibula due to early walking, and one radius was deemed unstable even after bio-pin and external fixator. Conclusions: Biodegradable -implants are excellent for carefully selected cases of intra-articular fractures and some small bone fractures. However, limitations for use in long bone fractures persist and no great advantage is gained if a “hybrid” composite is employed. The mechanical properties of biopins and screws in isolation are perceived to be inferior to those of conventional metal implants, leading to low confidence levels regarding the stability of reduced fractures; these implants should be used predominantly in fracture patterns in which internal fixation is subjected to minimal stress.

Dhillon, Mandeep S; Prabhakar, Sharad; Prasanna, Chandiralingam



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



Biomechanical evaluation of an expandable meshed bag augmented with pedicle or facet screws for percutaneous lumbar interbody fusion  

Microsoft Academic Search

ObjectiveTo evaluate the biomechanics of lumbar motion segments instrumented with stand-alone OptiMesh system augmented with posterior fixation using facet or pedicle screws and the efficacy of discectomy and disc distraction.

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




NSDL National Science Digital Library

Addition can be so much fun, especially with these games. Tweet, Tweet, Addition is not a game for the birds. Keep the game Math Popper away from all sharp pins! Watch out! Addition facts are attacking the spaceships in Addition Attack In Cannon Math you can shoot people out of a cannon! It is great fun!! Dr. Brain s Robot needs help with his math facts. Can you help ...

Games, Aidan'S M.



Mechanical comparison of fixation techniques for the offset V osteotomy: a saw bone study.  


Four different techniques for the fixation of an offset V bunionectomy were tested on solid-foam saw-bone models for the purpose of determining the strongest form of fixation for the osteotomy. Twenty identical models were placed into 4 different groups. Groups varied as to the placement and caliber of fixation. Models were loaded with a servo-hydraulic testing machine until failure of fixation occurred. Video analysis was used to record the pattern of failure of the fixation. Failure occurred either distal to the first screw, through the first screw hole, between the 2 screws, through the second screw hole, or proximal to the second screw. The mean force to failure of the groups was group 1, 58.1 N; group 2, 59.3 N; group 3, 64.0 N; and group 4, 105.66 N. There was a statistical significant difference between group 4 and the other 3 groups (F(1) = 55.45, P < 0.05). There was no statistical difference between groups 1 to 3. In groups 1 to 3, 87% of the failures were through the distal screw hole, whereas the remaining 13% were through the proximal screw hole. In group 4, 60% of the failures were through the proximal screw hole and 40% were through the distal screw hole. It was concluded that, in this model, the strongest form of fixation for an offset V osteotomy was the 2.7-mm cortical screw placed distally with the proximal point of fixation being a threaded 0.062-inch Kirschner wire. PMID:14688775

Jacobson, Keith; Gough, Adam; Mendicino, Samuel S; Rockett, Matthew S


The Mechanics of External Fixation  

PubMed Central

External fixation has evolved from being used primarily as a last resort fixation method to becoming a main stream technique used to treat a myriad of bone and soft tissue pathologies. Techniques in limb reconstruction continue to advance largely as a result of the use of these external devices. A thorough understanding of the biomechanical principles of external fixation is useful for all orthopedic surgeons as most will have to occasionally mount a fixator throughout their career. In this review, various types of external fixators and their common clinical applications are described with a focus on unilateral and circular frames. The biomechanical principles that govern bony and fixator stability are reviewed as well as the recommended techniques for applying external fixators to maximize stability. Additionally, we have illustrated methods for managing patients while they are in the external frames to facilitate function and shorten treatment duration.

Rozbruch, S. Robert



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



A new device for internal fixation of thoracolumbar and lumbar spine fractures: the 'fixateur interne'.  


A new system of operative fixation of thoracolumbar and lumbar spine fractures is presented: the 'fixateur interne' (F.I.). From a posterior approach long Schanz screws are inserted through the pedicles into the body of the two vertebrae just adjacent to the lesion and connected by th threaded F.I. rods. By tightening the nuts the Schanz screws are fixed in all directions. The advantages of the F.I. system are: excellent reposition by the long lever-arm of the Schanz screws, immobilization of only two segments and therefore good mobility of the residual spine, stability against flexion forces better than is obtained with Harrington distraction rods, additional rotational stability, and fixation in lordosis or kyphosis as is desired. The F.I. does not act as a four point bending system like all other dorsal spine instrumentation systems, but provides stability in flexion by itself. Therefore it can be Used independently of the condition of all ligaments (including the anterior longitudinal ligament) and of the posterior wall of the fractured vertebrae, and there is no need to fix more than the two immediately adjacent vertebrae, thus avoiding the often painful and cumbersome iatrogenic loss of lumbar lordosis and of mobility and permitting early mobilization of the patient. Experience with the first 45 patients is very promising. PMID:3900882

Dick, W; Kluger, P; Magerl, F; Woersdörfer, O; Zäch, G



[Biomechanical properties of external Ilizarov fixator with hybrid implants system].  


Possible ways of improving the stability of the fragments of the femur under elongation by introducing hybrid implant systems (the Kirschner wires and the Schanz screws) into the Ilizarov fixator structure were explored. Experimental studies were conducted on physical models with the fixator mounted on a pipe section modelling the femur shaft. Ten modifications of the Ilizarov fixator were developed and tested. The designs differed in the kind and configuration of implants. The effect of the developed Ilizarov fixator designs was examined by comparing the coefficients of axial, transversal and torsional rigidity of the structures. The research results clearly show that the Ilizarov fixator's rigidity (particularly transverse rigidity) coefficients can be considerably increased by replacing the Kirschner wires with the Schanz screws or using hybrid systems of these implants. As a result, the stability of the femur fragments improves and so does the quality of the regenerated bone, which makes it possible to reduce the treatment time to a minimum. PMID:16021824

Filipiak, Jaros?aw; Morasiewicz, Leszek




NSDL National Science Digital Library

We will practice adding! Practice with Fribbit! Fribbit Addition Add the numbers to save the apples. Save the Apples! Help the pirate add his marbles. Pirate Marble Addition Catch the correct sum! Fish Addish Balance the sides of the equal sign. Balance Equations ...

Hoffmann, Mrs.



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



Fractures of the Proximal Fifth Metatarsal: Percutaneous Bicortical Fixation  

PubMed Central

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

Mahajan, Vivek; Chung, Hyun Wook



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


Operative time analysis of miniplate fixation of the mandible.  


Our purpose in this study was to report and compare operating room times for the various methods of mandible fracture repair. We describe a methodology of treatment in selected patients, using efficient repair techniques; namely, miniplate fixation with four-screw mandibular occlusion. We report our outcomes in successful healing, occlusion, complications, and operating times. A retrospective chart review was performed of 68 patients suffering mandible fractures treated by various surgeons at a single institution. Miniplate fixation technique requires significantly less time in the operating room than other mandible repair techniques, including mandibulomaxillary fixation. Miniplate fixation technique is both an efficacious and an efficient means of repairing certain mandible fractures. PMID:16307396

Scurry, W Cooper; Beus, Kirt S; McGinn, Johnathan; Fedok, Fred G



Retrospective Comparison of Percutaneous Fixation and Volar Internal Fixation of Distal Radius Fractures  

PubMed Central

A change in the practice of a single surgeon provided an opportunity for retrospective comparison of comparable cohorts treated with percutaneous fixation (17 patients) or a volar plate and screws (23 patients) an average of 30 months after surgery. The final evaluation was performed according to the Gartland and Werley and Mayo rating systems and the DASH questionnaire. There were no significant differences on the average scores for the percutaneous and volar plating groups, respectively: Gartland and Werley, 4 vs 5; Mayo, 82 vs 83; and DASH score 13 for both cohorts. Motion, grip, and radiographical parameters were likewise comparable. Volar internal plate and screw fixation can achieve results comparable to percutaneous fixation techniques in the treatment of fractures of the distal radius.

Lozano-Calderon, Santiago A.; Doornberg, Job N.



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.



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



Modification of arch bars used for intermaxillary fixation in oral and maxillofacial surgery.  


Arch bars and intermaxillary fixation (IMF) screws are the most popular ways to achieve IMF in oral and maxillofacial surgery. Both techniques have advantages and limitations. The author proposes a simple modification of the conventional arch bar in order to place it with 1.5 mm screws in a quicker procedure that is safer for the surgical team. PMID:23245627

de Queiroz, S B F



Spontaneous urinary voiding of metallic screws in a patient with symphyseal plating for type II pelvic ring disruption.  


With rapid advancement in surgical techniques and improvement in implant materials, rate of internal fixation for pubic symphyseal disruption in rotationally and vertically unstable pelvic ring injuries has increased. Among various modes of implant failure, screw/plate breakage and loosening are common complications following unstable fixation. Migration of loose screws into the urinary bladder has been reported as an extremely uncommon complication of pubic symphyseal plating. Here we present a case report of a 52-year-old female who presented with asymptomatic passage of screws in her urine following migration into the bladder, 2 years after symphyseal plating for pubic diastasis in an anteroposterior compression pelvic ring injury. PMID:23910676

Yadav, Sanjay; Arora, Naresh Chander; Prasad, Manish; Varma, Rohit



[Remarks on biomechanics of external fixation.].  


In our experimental study we report results of a measurement of the stiffness of different types of external fixators. In model of external fixation of the femur the mechanical properties of Hoffmann, Wagner, Ilizarov and Poldi 7 aparates were evaluated in model of external fixation of the tibia the properties of the different configurations of the unilateral frame and of the combined unilateral frame and bilateral frame were evaluated. Our results have shown the importance: - the stiffness of an applied frame, - the proper interconection of the used configura tion of the apparatus (frame), - the number and placement of an individual im plants screws, pins. Some of the obtained results were applied in our clinical practice. Key words: external fixation, biomechanics. PMID:20470527

Stehlík, J; Novotný, R; Klézl, Z; Cech, O



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



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



Intraosseous ultrasound for pedicle screw positioning in the subaxial cervical spine: an experimental study  

Microsoft Academic Search

Background  In contrast to other regions of the human spine, dorsal fixation with rods and pedicle screws is comparatively rarely performed\\u000a in the cervical spine. Although this technique provides a higher mechanical strength than the more frequently used lateral\\u000a mass screws, many surgeons fear the relatively high rate of misplacements. This higher incidence is mainly due to the complex\\u000a vertebral anatomy

Sven Rainer Kantelhardt; Hans Christoph Bock; Laila Siam; Jörg Larsen; Ralf Burger; Wolfgang Schillinger; Volker Bockermann; Veit Rohde; Alf Giese



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


Bone changes after experimental osteotomies fixed with absorbable self-reinforced poly- l-lactide screws or metallic screws studied by plain radiographs, quantitative computed tomography and magnetic resonance imaging  

Microsoft Academic Search

The healing of the distal femoral osteotomy fixed with self-reinforced poly-l-lactide (SR-PLLA) or metallic screws in 16 rabbits was evaluated with plain radiographs, quantitative computed tomography and magnetic resonance imaging (MRI). At 36 weeks in the metallic fixation there was significantly more external callus than in the SR-PLLA fixation. On the metallic fixation side the cortical bone mineral density was

J. Viljanen; J. Kinnunen; S. Bondestam; A. Majola; P. Rokkanen; P. Törmälä



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



SPECT-CT Assessment of Pseudarthrosis after Spinal Fusion: Diagnostic Pitfall due to a Broken Screw  

PubMed Central

A 43-year-old drug addicted female was referred for a L5-S1 posterolateral in situ fixation with autologous graft because of an L5/S1 severe discopathy with listhesis. After six months, low back pain recurred. A Tc-99m HDP SPECT-CT diagnosed a pseudarthrosis with intense uptake of the L5-S1 endplates and a fracture of the right S1 screw just outside the metal-bone interface without any uptake or bone resorption around the screw. The absence of uptake around a broken screw is a pitfall that the physician should be aware of.

Rager, Olivier; Amzalag, Gael; Varoquaux, Arthur; Schaller, Karl; Ratib, Osman; Tessitore, Enrico



Fixation of distal radius fractures in adults: a review.  


In patients for whom function is a priority, anatomic reduction and stable fixation are prerequisites for good outcomes. Several therapeutic options exist, including orthopedic treatment and internal fixation with pins (intra- and extrafocal), external fixation which may or may not bridge the wrist, and different internal fixation techniques with dorsal or palmar plates using or not, locking screws. Arthroscopy may be necessary in case of articular fracture. In the presence of significant metaphyseal bone defects, filling of the comminution with phosphocalcic cements provides better graft stability. The level of evidence is too low to allow recommending one type of fixation for one type of fracture; and different fixation options to achieve stable reduction exist, each with its own specific complications. With the new generations of palmar plate, secondary displacement is becoming a thing of the past. PMID:23518070

Obert, L; Rey, P-B; Uhring, J; Gasse, N; Rochet, S; Lepage, D; Serre, A; Garbuio, P



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



Rigid versus wire fixation for mandibular advancement: Skeletal and dental changes after 5 years  

Microsoft Academic Search

The bilateral sagittal split osteotomy (BSSO) is the most common surgical procedure for the correction of mandibular retrognathism. Commonly, the proximal and distal segments are fixated together with either wire or rigid screws or plates. The purpose of this study was to compare long-term (5 years) skeletal and dental changes between wire and rigid fixation after BSSO. In this multisite,

Calogero Dolce; John P. Hatch; Joseph E. Van Sickels; John D. Rugh



The retrograde nail for distal femoral fractures in the elderly: high failure rate of the condyle screw and nut.  


Displaced distal femoral fractures in elderly patients benefit from surgical fixation. We describe the use of a retrograde femoral nail to treat these fractures. The implant has a special condyle screw and nut that allows for manual compression of the fracture when there is an additional inter-condylar split. We present our results when using this implant to treat 16 patients over a 13-month period. The mean patient age was 78 years (range, 65-96 years). All 16 patients were available at the time of final follow up and proceeded to union at an average time of 11 weeks (range, 10-14 weeks). Twenty-six condyle screw and nuts were used. Ten out of 26 condyle screws in 10 out of 16 patients failed by disengaging at a mean time of 10 weeks (range, 8-12 weeks). Our union rate was unaffected by the nut and bolt disengaging. This would suggest that the condylar compression generated by the nut and bolt may not be critical for union. PMID:16499912

Singh, S K; El-Gendy, K A; Chikkamuniyappa, C; Houshian, S



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.



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



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

Microsoft Academic Search

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

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



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



Improvements in bio-mechanical adhesion of screws used in medical field: first application in spinal surgery.  


Metallic screws are becoming more and more useful to join bones or for prosthesis support in orthopaedic and dental surgery. High biocompatible materials such as titanium alloys and hydroxyapatite ceramics are making possible the realization of stable fixation devices utilizable in load-bearing applications. The mechanical and biological anchorage of metallic screws to the bone depends on many factors: mechanical screws-bone thread matching, use of cements between bone and screw, chemical-physical treatments of screw surface, use of screw coverage films based on osteointegrating ceramics or active bioglasses, use of porous coverage films to induce bone ingrowth into the pore, and so on. The first step of the research, the aim of the present paper, is the comparison among screws of different shapes and geometric characteristics in order to find the best macromechanical system versus the different load conditions. Static and dynamic tests are applied to the screws mounted on segments of pig spine, in order to measure the mechanical characteristics of the system under tension (pull-out), bending on the principal planes along the axis of the screw and fatigue loads. Physical analysis, obtained using energetic charged particles, such as SEM, RBS, and AES, are used to characterize the screw surface compositions and morphology. PMID:7773142

Guglielmino, E; La Rosa, G; Russo, T C; Torrisi, L



Lateral Mass and Pedicle Screws Fixation of Cervical Spine  

Center for Biologics Evaluation and Research (CBER)

Text Version... Nazarian Spine 1991 Levine Spine 1992 ... Spine 1992;17:S442-6. 6. Levine AM, Mazel C, Roy-Camille R. Management of fracture ... More results from


Mycobacterium fortuitum infection after anterior cruciate ligament reconstruction using a polylactic acid bioabsorbable screw: Case report.  


We report a case of pretibial sinus and abscess after anterior cruciate ligament reconstruction using a polylactic acid tricalcium phosphate bioabsorbable screw for tibial fixation. Mycobacterium fortuitum was identified as the pathogen after specific mycobacterial cultures were obtained from operative specimens. M. fortuitum is a known but rare cause of periprosthetic infection. Diagnosis is often delayed as routine microbiological cultures do not utilise specific culture requirements for mycobacterial growth. There have been several reports in the literature of sterile abscesses associated with bioabsorbable screws. To our knowledge, this is the first case report of a non-tuberculous mycobacterial infection associated with a bioabsorbable implant. This case illustrates that post-operative Mycobacterium infection can occur as a complication of ACL reconstruction with bioabsorbable screw fixation and should be considered in the differential diagnosis of post-operative periprosthetic infection. PMID:19744856

Oh, Horng Lii; Chen, Darren B; Seeto, Bradley G; Macdessi, Samuel J



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



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


The biomechanical analysis of three plating fixation systems for periprosthetic femoral fracture near the tip of a total hip arthroplasty  

Microsoft Academic Search

BACKGROUND: A variety of techniques are available for fixation of femoral shaft fractures following total hip arthroplasty. The optimal surgical repair method still remains a point of controversy in the literature. However, few studies have quantified the performance of such repair constructs. This study biomechanically examined 3 different screw-plate and cable-plate systems for fixation of periprosthetic femoral fractures near the

James P Lever; Rad Zdero; Markku T Nousiainen; James P Waddell; Emil H Schemitsch



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



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



Mechanical evaluation of cross pins used for femoral fixation of hamstring grafts in ACL reconstructions.  


The goal of this study was to test the mechanical strength of 4 different cross pins currently available for femoral fixation by loading each cross pin to failure as received and determine the effect of 1 million cycles of fatigue loading. Additionally, the strength of resorbable pins was tested after prolonged exposure to biologic conditions. Six implants each of the Arthrotek LactoSorb (Biomet, Warsaw, Indiana), Mitek RigidFix (DePuy Mitek Inc, Raynham, Massachusetts), Arthrotek Bone Mulch Screw (Biomet), cortical allograft, and control were tested for 3-point failure without prior loading and after cyclic loading between 50 to 200 N at 10 Hz for 1 million cycles. The bioabsorbable pins were placed in sterile water at 37°C and tested after 2, 4, and 6 months for 3-point failure strength. All implants tested without antecedent loading demonstrated adequate strength for initial fixation for hamstring grafts. During fatigue testing, RigidFix implants (n=6) failed at 18,893±8365 cycles (with a central deformation of 0.48±0.11 mm prior to fracture). All of the other implants tested endured 1 million cycles of loading (50-200 N) without fracture or 1.5 mm central deformation. Neither of the bioabsorbable pins demonstrated a significant change in yield strength after prolonged exposure to water. All implants tested demonstrated adequate strength for initial fixation of hamstring grafts. The metal and bone implants far exceed the strength required to sustain mechanical fixation until biological fixation occurs; both polymeric implants demonstrated that they maintained enough mechanical strength to achieve this goal. PMID:20954667

Bellisari, Gregory E; Kaeding, Christopher C; Litsky, Alan S



Evaluation of pelvic fixation in neuromuscular scoliosis: a retrospective study in 55 patients  

PubMed Central

The literature has described different indications for pelvic fixation in neuromuscular scoliosis. We retrospectively evaluated changes in pelvic obliquity for a minimum of two years among three groups: group I (initial pelvic obliquity >15°; with pelvic fixation), group II (initial pelvic obliquity >15°; without pelvic fixation), and group III (initial pelvic obliquity <15°; without pelvic fixation). We used iliac screws for pelvic fixation in group I. There was significant postoperative improvement (p?15° require pelvic fixation to maintain the correction and balance over time while obliquity <15° does not require pelvic fixation.

Modi, Hitesh N.; Song, Hae-Ryong; Hyuk Yang, Jae; Jajodia, Nirmal



Hamate hook non-union treated with a break-away screw: a case report.  


Hamate hook non-union is a relatively rare, but on the increase. We encountered a 25-year-old male baseball instructor with hamate hook non-union, and treated it with debridement of the fractured region and osteosynthesis using a break-away screw. Splint fixation was applied for three weeks after surgery, and active/passive range of motion exercises were actively performed thereafter. Bone union was noted three months after surgery. Transient ulnar paralysis resolved, and the patient could return to the same sports activity as that before injury six months after surgery. Since break-away screws are capable of loading a strong pressure on the fractured region and these screws can be inserted by preparing only a surgical field for guide wire insertion, requiring no soft tissue dissection to prepare a region for applying fixation materials, break-away screws are useful for the fixation of small bone fragments and osteosynthesis in a deep surgical field. PMID:24156590

Naito, Kiyohito; Yoshikawa, Kei; Kaneko, Kazuo; Obayashi, Osamu



Failure of volar locking plate fixation of an extraarticular distal radius fracture: A case report  

PubMed Central

Background Volar locking plates provide significant structural stability to the distal radius. Failure of a volar locked plating is a rarely reported complication in the literature. Case Presentation A 40 year-old, obese female patient who presented with a displaced extraarticular distal radius fracture, underwent open reduction and internal fixation of the fracture using a volar locking plate. Radiographs taken at 10 weeks postoperatively showed failure of fixation with breakage of the four distal locking screws. A hardware removal was performed at 6 months, and the patient was then lost to follow-up. She presented again at 18 months after the first surgery, with significant pain, and radiographic signs of a radial collapse and a fracture-nonunion. A total wrist fusion was performed as the method of choice at that point in time. Conclusion Volar locked plating represents the new "gold standard" of distal radius fracture fixation. However, despite the stability provided by locking plates, hardware failure may occur and lead to a cascade of complications which will ultimately require a wrist fusion, as outlined in this case report. Additional structural support by bone grafting may be needed in selected cases of volar locked plating, particularly in patients with a high risk of developing a fracture-nonunion.



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



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



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



Fixation, leaching, and plant uptake of fluorine from additions of certain fluorides in representative sandy soils: the fluorine problem in certain Florida areas  

Microsoft Academic Search

Experiments were conducted to determine the effects of fluorides upon the fertility of sandy soils. The results of soil leaching of fluorides, as well as the possible effect of additive fluorides upon seed emergence and plant response are presented. Related uptake of fluorine by plants at various durations of growth were investigated. Observations reveal that grass seed was not affected




Biomechanical comparison of fixation devices in experimental scaphoid osteotomies.  


This study determined the force, bending rigidity, and bending moment at failure of three types of internal fixation systems for the scaphoid bone. A pair of parallel, 0.045-inch Kirschner wires were compared on a paired, bilateral basis with either a Herbert screw or a 3.5 millimeter cannulated screw in repairing a transverse waist osteotomy in cadaver scaphoids. The mean values at failure of the Herbert screw and the cannulated screw versus the paired, parallel Kirschner wires for force (65 N and 77 N versus 23.7 N), rigidity (0.47 Nm2 and 0.54 Nm2 versus 0.16 Nm2) and bending (0.98 Nm and 1.15 Nm versus 0.36 Nm) were approximately three times greater. These differences were statistically significant when compared on a paired basis. This experiment demonstrates that the Herbert screw and cannulated screw are significantly stronger in resisting bending forces than paired, parallel Kirschner wires. PMID:1940173

Carter, F M; Zimmerman, M C; DiPaola, D M; Mackessy, R P; Parsons, J R



In vitro biomechanical evaluation of sagittal split osteotomy fixation with a specifically designed miniplate.  


Recent studies have evaluated many methods of internal fixation for sagittal split ramus osteotomy (SSRO), aiming to increase stability of the bone segments while minimizing condylar displacement. The purpose of this study was to evaluate, through biomechanical testing, the stability of the fixation comparing a specially designed bone plate to other two commonly used methods. Thirty hemimandibles were separated into three equal groups. All specimens received SSRO. In Group I the osteotomies were fixed with three 15 mm bicortical positional screws in an inverted-L pattern with an insertion angle of 90°. In Group II, fixation was carried out with a four-hole straight plate and four 6mm monocortical screws. In Group III, fixation was performed with an adjustable sagittal plate and eight 6mm monocortical screws. Hemimandibles were submitted to vertical compressive loads, by a mechanical testing unit. Averages and standard deviations were submitted to analysis of variance using the Tukey test with a 5% level of significance. Bicortical screws presented the greatest values of loading resistance. The adjustable miniplate demonstrated 60% lower resistance compared to bicortical screws. Group II presented on average 40% less resistant to the axial loading. PMID:22898312

Pereira Filho, V A; Iamashita, H Y; Monnazzi, M S; Gabrielli, M F R; Vaz, L G; Passeri, L A



Low complications after minimally invasive fixation of calcaneus fracture  

PubMed Central

Calcaneus fractures are still a delicate point regarding the indication for osteosynthesis. Knowing the skin’s poor vascularisation of the back foot, the purpose of this study is to present the benefits of proper surgical options between an open and invasive osteosynthesis with anatomical reduction and internal fixation or minimally invasive approach preserving the quality of the soft parts. 66 interventions that targeted reduction and internal fixation of calcaneus fractures were performed between 2009-2012, in the Orthopaedic and Traumatology Department of Bucharest Emergency University Hospital. 29 cases underwent open reduction and internal fixation with plates and screws or Kirschner wires, and 37 cases underwent a minimally invasive reduction and Essex Lopresti osteosynthesis technique. No patient who underwent a minimally invasive reduction had skin lesions, but showed pain due to osteoarthritis lesions that appeared in the subtalar joint. 4 of them, who underwent open reduction and internal fixation had postoperative wound infections and skin necrosis.

Ene, R; Popescu, D; Panaitescu, C; Circota, G; Cirstoiu, M; Cirstoiu, C



The "medio-latero-superior trajectory technique": an alternative cortical trajectory for pedicle fixation.  


An alternative pedicle trajectory for use at the superior end of a construct to limit dissection of the mobile superior facet joint and reduce incision length and muscle dissection, thus minimizing approach-related trauma during pedicle fixation, is reported. The medio-latero-superior trajectory technique involves a starting point on the medial aspect of the pars and angulation of the pedicle screw in a mediolateral and caudocranial direction. This approach takes advantage of a predominantly cortical trajectory to assist with bone fixation. Drawbacks of this new screw trajectory are discussed along with its potential benefits. PMID:23420749

Mobbs, Ralph J



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

Microsoft Academic Search

Background  This study evaluates the outcome and complications of decompressive cervical Laminectomy and lateral mass screw fixation in\\u000a 110 cases treated for variable cervical spine pathologies that included; degenerative disease, trauma, neoplasms, metabolic-inflammatory\\u000a disorders and congenital anomalies.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  A retrospective review of total 785 lateral mass screws were placed in patients ages 16-68 years (40 females and 70 males).\\u000a All cases were

Moh’d M Al Barbarawi; Ziad A Audat; Moutasem M Obeidat; Tareq M Qudsieh; Waleed F Dabbas; Mouness H Obaidat; Anas A Malkawi



Chemical fixation of arsenic in contaminated soils  

Microsoft Academic Search

Arsenic-contaminated soils have been successfully treated using fixation methods whereby chemicals are added to prevent As mobilization. However, the chemistry of the fixation process used in the field is poorly understood. We have examined one process which succeeded in immobilizing 0. I to 0.2 weight % As in soil at a 69 a old dump site through the addition of

Remy J.-C. Hennet; S. L. Brantley



A biomechanical experiment and clinical study of the use of figure of eight plus circular wiring fixation for the treatment of olecranon fractures.  


The aim of the present study was to evaluate the stability of the figure of eight plus circular wiring fixation technique compared with four common internal fixation techniques and to provide experimental data for the selection of internal fixation techniques clinically. A total of 20 fresh cadaveric elbow joints were used as transverse, oblique and comminuted olecranon fracture models. Five techniques of internal fixation were investigated: circular wiring, figure of eight wiring, circular plus figure of eight wiring, Kirschner wire (K-wire) and screw fixation. The elbow joints were flexed at 90°. The fixation performance was tested using a high-precision displacement sensor. Displacement-load curves revealed that the strength of internal fixation was weakest when using circular wiring alone and that circular wiring plus figure of eight wiring fixation was stronger than that of figure of eight wiring or screw fixation. The difference was statistically significant (P<0.05). There were no significant differences between circular wiring plus figure of eight wiring fixation and K-wire fixation in the transverse and oblique fracture models (P>0.05). However, figure of eight plus circular wiring fixation was superior to K-wire fixation in the comminuted fracture model, with a tensile force of 67.42±2.17 vs. 58.52±2.17 N, respectively (P<0.05). All 152 patients with olecranon fractures who received circular wiring plus figure of eight wiring fixation recovered and 108 were included in the follow-up for an average of 12 months. The rate of excellent/fairly good recovery was 98.10%. Due to its reliability, simple surgery, lower invasiveness and lower cost, figure of eight plus circular wiring fixation is an ideal choice for the internal fixation of olecranon fractures, particularly comminuted fractures, compared with circular wiring, figure of eight wiring or screw fixation. PMID:23226778

Wang, Wulian; Wu, Guangwen; Shen, Fuer; Zhang, Yiyuan; Liu, Xianxiang



A biomechanical experiment and clinical study of the use of figure of eight plus circular wiring fixation for the treatment of olecranon fractures  

PubMed Central

The aim of the present study was to evaluate the stability of the figure of eight plus circular wiring fixation technique compared with four common internal fixation techniques and to provide experimental data for the selection of internal fixation techniques clinically. A total of 20 fresh cadaveric elbow joints were used as transverse, oblique and comminuted olecranon fracture models. Five techniques of internal fixation were investigated: circular wiring, figure of eight wiring, circular plus figure of eight wiring, Kirschner wire (K-wire) and screw fixation. The elbow joints were flexed at 90°. The fixation performance was tested using a high-precision displacement sensor. Displacement-load curves revealed that the strength of internal fixation was weakest when using circular wiring alone and that circular wiring plus figure of eight wiring fixation was stronger than that of figure of eight wiring or screw fixation. The difference was statistically significant (P<0.05). There were no significant differences between circular wiring plus figure of eight wiring fixation and K-wire fixation in the transverse and oblique fracture models (P>0.05). However, figure of eight plus circular wiring fixation was superior to K-wire fixation in the comminuted fracture model, with a tensile force of 67.42±2.17 vs. 58.52±2.17 N, respectively (P<0.05). All 152 patients with olecranon fractures who received circular wiring plus figure of eight wiring fixation recovered and 108 were included in the follow-up for an average of 12 months. The rate of excellent/fairly good recovery was 98.10%. Due to its reliability, simple surgery, lower invasiveness and lower cost, figure of eight plus circular wiring fixation is an ideal choice for the internal fixation of olecranon fractures, particularly comminuted fractures, compared with circular wiring, figure of eight wiring or screw fixation.




Evaluation of the syndesmotic-only fixation for Weber-C ankle fractures with syndesmotic injury  

PubMed Central

Background: With the length of the fibula restored and the syndesmosis reduced anatomically, internal fixation using a plating device may not be necessary for supra-syndesmotic fibular fractures combined with diastasis of inferior tibio-fibular joint. A retrospective observational study was performed in patients who had this injury pattern treated with syndesmosis-only fixation. Materials and Methods: 12 patients who had Weber type-C injury pattern were treated with syndesmosis only fixation. The treatment plan was followed only if the fibular length could be restored and if the syndesmosis could be anatomically reduced. Through a percutaneous or mini-open reduction and clamp stabilization of the syndesmosis, all but one patient had a single tricortical screw fixation across the syndesmosis. Patients were kept non-weight-bearing for 6 weeks, followed by screw removal at an average of 8 weeks. Outcomes were assessed using an objective ankle scoring system (Olerud and Molander scale) and by radiographic assessment of the ankle mortise. Results: At a mean follow-up of 13 months, the functional outcome score was 75. Excellent to good outcomes were noted in 83% of the patients. Ankle mortise was reduced in all cases, and all but one fibular fracture united without loss of fixation. Six patients had more than one malleolar injury, needing either screw or anchor fixations. One patient had late diastasis after removal of the syndesmotic screw and underwent revision surgery with bone grafting of the fibula. This was probably due to early screw removal, before union of the fibular fracture had occurred. Conclusion: We recommend syndesmosis-only fixation as an effective treatment option for a combination of syndesmosis disruption and Weber type-C lateral malleolar fractures.

Mohammed, R; Syed, S; Metikala, S; Ali, SA



New techniques and alternative fixation for the lapidus arthrodesis.  


Arthrodesis of the first metatarsocuneiform joint is a powerful and durable procedure to help correct moderate to severe hallux valgus and/or first ray hypermobility. However, painful nonunion remains a notoriously high potential outcome. Research regarding locking plates seems promising, and data show lower rates of nonunion. Innovative fixation techniques are new and should be considered in the future as further literature is available on their long-term use. Regardless of the fixation, proper joint preparation and good compression is fundamentally the most important. A case of Lapidus fusion with locking plates after a failed arthrodesis with screws alone is presented. PMID:23827494

Young, Nathan J; Zelen, Charles M



Nitrogen fixation ability of exopolysaccharide synthesis mutants of Rhizobium sp. strain NGR234 and Rhizobium trifolii is restored by the addition of homologous exopolysaccharides.  

PubMed Central

Several transposon Tn5-induced mutants of the broad-host-range Rhizobium sp. strain NGR234 produce little or no detectable acidic exopolysaccharide (EPS) and are unable to induce nitrogen-fixing nodules on Leucaena leucocephala var. Peru or siratro plants. The ability of these Exo- mutants to induce functioning nodules on Leucaena plants was restored by coinoculation with a Sym plasmid-cured (Nod- Exo+) derivative of parent strain NGR234, purified EPS from the parent strain, or the oligosaccharide from the EPS. Coinoculation with EPS or related oligosaccharide also resulted in formation of nitrogen-fixing nodules on siratro plants. In addition, an Exo- mutant (ANU437) of Rhizobium trifolii ANU794 was able to form nitrogen-fixing nodules on white clover in the presence of added EPS or related oligosaccharide from R. trifolii ANU843. These results demonstrate that the absence of Rhizobium EPSs can result in failure of effective symbiosis with both temperate and subtropical legumes. Images

Djordjevic, S P; Chen, H; Batley, M; Redmond, J W; Rolfe, B G



Salvage hip arthroplasty after failed fixation of proximal femur fractures.  


We reviewed 46 patients who underwent salvage hip arthroplasty (SHA) for revision of failed cannulated screws (CS), sliding hip screws (SHS), or intramedullary nails (IMN). The primary objective was to determine differences in operative difficulty. SHA after failed femoral neck fixation was associated with lower intra-operative demands than after failed peri-trochanteric fractures. Similarly, analysis by the index implant found that conversion arthroplasty after failed CSs was associated with lower intra-operative morbidity than failed SHSs or IMNs; differences between SHS and IMN were not as clear. Importantly, intra-operative data in cases of failed SHSs were similar regardless of the original fracture type, showing the device played a larger role than the fracture pattern. Complications and revision surgery rates were similar regardless of fracture type or fixation device. Our results suggest that operative demands and subsequent patient morbidity are more dependent on the index device than the fracture pattern during SHA. PMID:23489728

DeHaan, Alexander M; Groat, Tahnee; Priddy, Michael; Ellis, Thomas J; Duwelius, Paul J; Friess, Darin M; Mirza, Amer J



Treatment of Palatal Fractures by Osteosynthesis with 2.0-mm Locking Plates as External Fixator  

PubMed Central

Treatment options for palatal fractures range from orthodontic braces, acrylic bars, and arch bars for maxillomandibular fixation to internal fixation, with plates and screws placed under the palate mucosa and periosteum, together with pyriform aperture or alveolar plating plus buttress reconstruction. Forty-five patients, ages 4 to 56, were treated using medium- or high-profile locking plates placed over the palatal mucosa as an external fixator for palatal fractures, together with treatment for other associated facial fractures. In open fractures, plates were placed after approximating the edges of the mucosal wounds. Plates and screws for palate fixation were removed at 12 weeks, when computed tomography scans provided evidence of fracture healing. All palatal fractures healed by 12 weeks, with no cases of mucosal necrosis, bone exposure, fistulae, or infections. This approach achieves adequate stability, reduces the risk of bone and mucosal necrosis, and promotes healing of mucosal wounds in case of open fractures.

Cienfuegos, Ricardo; Sierra, Eduardo; Ortiz, Benjamin; Fernandez, Gerardo



An alternative method of fixation of calcaneal tuberosity fractures using the tightrope(®) technique.  


Calcaneal tuberosity fractures account for 1% to 3% of all calcaneal fractures. These fractures are frequently seen in the osteoporotic or diabetic elderly population. The patient's comorbidities, coupled with the usually osteoporotic bone, make fixing this fracture pattern a challenge. Numerous surgical techniques have been advocated for this fracture, including the standard lag screw fixation, tension band wiring, suture anchors, and direct suture repair. Whichever method is used, the construct must resist the massive pull of the gastrocnemius-soleus complex. We have described a method of fixing the avulsed calcaneal tuberosity using the TightRope(®) ankle syndesmosis fixation device (Arthrex(®), Naples, FL), which offers the advantages of allowing a robust and reliable fixation of a small or comminuted fragment. It is particularly advantageous in osteoporotic bone because of concern regarding the use of standard lag screw fixation, and it also may eliminate complications associated with retained hardware. PMID:24160723

Harb, Ziad; Dachepalli, Sunil; Mani, Ganapathyraman


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


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

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



Femoral neck fracture fixation: rigidity of five techniques compared.  

PubMed Central

Artificial cadaveric femoral neck fractures were internally fixed with five different devices and subjected to cyclical loading of 0-1.0 kilonewtons (approximately one body weight) whilst in an anatomical position. Displacement of the proximal fragment was detected by a transducer and charted. Bone strength was assessed by a preliminary control loading phase on the intact bone. Efficiency of each fracture fixator could then be directly compared by the relative movement in each case. Five specimens each were tested with Moore's Pins, Trifin Nail, Garden Screws and a sliding screw-plate (OEC Ltd). By the criteria of the experiment, which put a severe shearing load on the implant, none of these devices reliably bore the representative body weight. An extended barrel-plate, which supported the sliding screw almost up to the fracture line, was then made. This device, employing some of Charnley's concepts, tolerated body weight in four cases out of five.

Mackechnie-Jarvis, A C



Cellulitis related to bioabsorbable plate and screws in infraorbital rim fracture.  


An absorbable plating system is most commonly used to fix the bones in craniomaxillofacial surgery. Many studies focused on the advantages and clinical utility of absorbable plate and screws, but there are no reports on the complications related to these devices. From March 2004 to March 2009, 430 patients with facial bone fractures including infraorbital rim fractures underwent craniomaxillofacial surgery, in which rigid fixation was achieved with an absorbable plate and screws (Stryker, Freiburg, Germany). Five men with a delayed inflammatory reaction and infection at infraorbital rim fracture site were reviewed. Their mean age was 39 (range, 18-53 y), and all patients had maxillary sinusitis. The period from surgery to the onset of symptoms ranged from 3 to 10 weeks with a mean of 5 weeks. One patient was managed with oral antibiotics, but the other 4 patients required incisional drainage with the removal of the plate and screws because of abscess formation. The patients' symptom improved after removing the absorbable plate and screws and saline irrigation, and there was no recurrence of infection during the 12-month follow-up period. When fixing infraorbital fractures, particularly in patients with sinusitis, it is recommended to use short screws to prevent penetration of the maxillary sinus wall. In particular, one should pay attention and use shorter screws owing to the thinness of the medial infraorbital rim. PMID:21403541

Kwon, Ho; Kim, Sang-Wha; Jung, Sung-No; Sohn, Won-Il; Moon, Suk-Ho



Fatigue failures of austenitic stainless steel orthopedic fixation devices  

Microsoft Academic Search

Failures of four different 300-series austenitic stainless steel biomedical fixation implants were examined. The device fractures\\u000a were observed optically, and their surfaces were examined by scanning electron microscopy. Fractography identified fatigue\\u000a to be the failure mode for all four of the implants. In every instance, the fatigue cracks initiated from the attachment screw\\u000a holes at the reduced cross sections of

M. E. Stevenson; M. E. Barkey; R. C. Bradt



Closed Reduction and Percutaneous Fixation of Pelvic Fractures  

Microsoft Academic Search

\\u000a This chapter on minimally-invasive percutaneous screw fixation of acetabular and sacral fractures will try to guide the reader\\u000a through the process of understanding the biomechanics and classification of the specific injury he or she is investigating,\\u000a recognizing and weighing the different conservative, minimallyinvasive and open treatment options and explaining how to perform\\u000a some of the minimally-invasive techniques. Close collaboration between

Rolf Huegli; Thomas Gross; Augustinus L. Jacob; Peter Messmer


Enhancing Biological Nitrogen Fixation.  

National Technical Information Service (NTIS)

The report summarizes present understanding of the broad area of the chemical and biological aspects of nitrogen fixation. It suggests: (a) opportunities for increasing fixation by leguma-bacterial and other types of systems, (b) approaches toward extendi...

H. J. Evans



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

Microsoft Academic Search

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

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



Efficacy of two point rigid internal fixation in the management of zygomatic complex fracture  

Microsoft Academic Search

Purpose  To evaluate the efficacy of two point rigid internal fixation in the immobilization of zygomatic complex fractures.\\u000a \\u000a \\u000a \\u000a Patients and methods  30 patients with zygomatic complex fractures were managed by open reduction and internal fixation using titanium mini bone\\u000a plate screws at the frontozygomatic and zygomatic buttress region. This prospective study was carried out at the Department\\u000a of Oral & Maxillofacial Surgery,

Ashish Chakranarayan; G. K. Thapliyal; R. Sinha; Menon P. Suresh



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


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

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



Biomechanical evaluation of a new fixation device for the thoracic spine  

PubMed Central

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

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



A radiological and cadaveric study of oblique lumbar interbody fixation in patients with normal spinal anatomy.  


The purpose of this study was to determine whether it would be feasible to use oblique lumbar interbody fixation for patients with degenerative lumbar disease who required a fusion but did not have a spondylolisthesis. A series of CT digital images from 60 patients with abdominal disease were reconstructed in three dimensions (3D) using Mimics v10.01: a digital cylinder was superimposed on the reconstructed image to simulate the position of an interbody screw. The optimal entry point of the screw and measurements of its trajectory were recorded. Next, 26 cadaveric specimens were subjected to oblique lumbar interbody fixation on the basis of the measurements derived from the imaging studies. These were then compared with measurements derived directly from the cadaveric vertebrae. Our study suggested that it is easy to insert the screws for L1/2, L2/3 and L3/4 fixation: there was no significant difference in measurements between those of the 3-D digital images and the cadaveric specimens. For L4/5 fixation, part of L5 inferior articular process had to be removed to achieve the optimal trajectory of the screw. For L5/S1 fixation, the screw heads were blocked by iliac bone: consequently, the interior oblique angle of the cadaveric specimens was less than that seen in the 3D digital images. We suggest that CT scans should be carried out pre-operatively if this procedure is to be adopted in clinical practice. This will assist in determining the feasibility of the procedure and will provide accurate information to assist introduction of the screws. PMID:23814253

Wu, A M; Tian, N F; Wu, L J; He, W; Ni, W F; Wang, X Y; Xu, H Z; Chi, Y L



Treatment of thoracolumbar fracture with pedicle screws at injury level: a biomechanical study based on three-dimensional finite element analysis.  


The aim of this study was to investigate the biomechanical mechanisms of treatment of thoracolumbar compression fracture with pedicle screws at injury level based on a three-dimensional finite element method. We constructed one three-dimensional finite element model of T11-L1 in a patient with a compression fracture of the T12 vertebral body(anterior edges of vertebral body were compressed to 1/2, and kyphosis Cobb angle was 18.6°) fixed by four pedicle screws and another model fixed by six pedicle screws at the injured vertebrae, and then assigned different forces to the two models to account for axial compression, flexion, extension, left lateral bending, and rightward axial rotation by Ansys software. After different loading forces were applied to the models, we recorded stress measurements on the vertebral pedicle screws, as well as the maximum displacement of T11. The stress distribution suggested that stress concentration was appreciable at the root of the pedicle screws under different loading modalities. Under axial compression, flexion, extension, left lateral bending, and rightward axial rotation load, the stress for the superior screw was significantly greater than the stress for the inferior screw (P < 0.05). The stress in the six pedicle screw fixation model was significantly decreased compared to the four screw interbody fusion model (P < 0.05), but the maximum displacement of T11 between two models under different loadings was not statistically different. The use of pedicle screws at injured vertebral bodies may optimize internal fixation load and reduce the incidence of broken screws. PMID:23412208

Li, Qin-Liang; Li, Xiu-Zhong; Liu, Yi; Zhang, Hu-Sheng; Shang, Peng; Chu, Zhao-Ming; Chen, Jin-Chuan; Chen, Ming; Qin, Rujie



Proximal femoral osteotomies in children using the Richards hip screw: techniques, outcome and subsequent removal  

PubMed Central

Introduction We investigated the clinical and radiological outcome of proximal femoral osteotomies in children using the Richards hip screw. We also describe previously unreported techniques used in the insertion of the screw to aid satisfactory correction of the neck shaft angle and medialisation. Methods Seventy-two children undergoing 81 proximal femoral osteotomies under the care of the senior author over a 10-year period were reviewed. Results For the primary procedure, there was an overall complication rate of 5%. This included two (2.5%) cases requiring re-operation. There were no fractures and no long-term complications. For subsequent removal of the metalwork, the complication rate was 5%, with a re-operation rate of 1%. Conclusion We conclude that the Richards hip screw is a safe, atraumatic and easy-to-use method of fixation for proximal femoral osteotomies in children, with lower complication.

Almaiyah, Mohammed; McVie, Jim; Montgomery, Richard J.



Internal fixation in patients with multiple injuries.  


The hypothesis is advanced that there are additional and exceptional indications for the use of internal fixation in the patient with multiple injuries. Eleven case studies of patients who sustained major injuries support this hypothesis. PMID:6629496

Merriam, W F; Mifsud, R P



The use of intraosseous screw for upper molar distalization: a case report.  


The use of implants has made a major change in orthodontic treatment mechanics. They have replaced conventional unaesthetic and compliance dependent extraoral appliances with well accepted intraoral mechanics. Implants can be used in molar and canine distalization, intrusion and in extraoral force applications. In the present case report, treatment of a case using an intermaxillary fixation screw (IMF) will be presented. The treatment results will be evaluated using pretreatment, post distalization and post treatment cephalometric radiographs and dental casts. PMID:19212521

Polat-Ozsoy, Omür



The Use of Intraosseous Screw for Upper Molar Distalization: A Case Report  

PubMed Central

The use of implants has made a major change in orthodontic treatment mechanics. They have replaced conventional unaesthetic and compliance dependent extraoral appliances with well accepted intraoral mechanics. Implants can be used in molar and canine distalization, intrusion and in extraoral force applications. In the present case report, treatment of a case using an intermaxillary fixation screw (IMF) will be presented. The treatment results will be evaluated using pretreatment, post distalization and post treatment cephalometric radiographs and dental casts.

Polat-Ozsoy, Omur



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



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



Two fixations suffice in face recognition.  


It is well known that there exist preferred landing positions for eye fixations in visual word recognition. However, the existence of preferred landing positions in face recognition is less well established. It is also unknown how many fixations are required to recognize a face. To investigate these questions, we recorded eye movements during face recognition. During an otherwise standard face-recognition task, subjects were allowed a variable number of fixations before the stimulus was masked. We found that optimal recognition performance is achieved with two fixations; performance does not improve with additional fixations. The distribution of the first fixation is just to the left of the center of the nose, and that of the second fixation is around the center of the nose. Thus, these appear to be the preferred landing positions for face recognition. Furthermore, the fixations made during face learning differ in location from those made during face recognition and are also more variable in duration; this suggests that different strategies are used for face learning and face recognition. PMID:19000210

Hsiao, Janet Hui-wen; Cottrell, Garrison



Plate fixation of premaxillomaxillary suture and compensatory midfacial growth changes in the rabbit.  


It has been suggested that rigid fixation of the developing craniofacial skeleton may lead to altered craniofacial growth. However, recent experimental studies have shown that microplate fixation of slow-growing calvarial sutures resulted in regional growth disturbances but had little effect on overall craniofacial growth. The present study was designed to assess the effects of microplate fixation of the more rapidly growing facial sutures on compensatory midfacial growth in the rabbit. Twenty-two 1.5-week-old rabbits were randomly divided into 2 groups: sham controls (n = 11) and animals with bilateral premaxillomaxillary suture fixation (n = 11). Fixation was accomplished using an intraoral approach, a 6-mm straight Luhr microplate, and two 2-mm long self-tapping screws across each suture. Serial lateral head radiographs were collected at 1.5, 3.5, 6, 12, and 18 weeks of age. Results revealed that by 3.5 weeks, animals with rigid fixation showed significantly shortened premaxillary lengths (p < 0.05), class III occlusal relationships, decreased midfacial heights, and abnormal palatocranial base angles compared with sham control animals. By 12 weeks of age, "catch-up" growth was evident in most dimensions in animals with fixation compared with shams. Gross examination of the cleaned and dried skulls revealed bony bridging across the premaxillomaxillary suture and osseous fracture lines extending superiorly from the site of screw fixation. Results demonstrated that rigid fixation of a rapidly growing facial suture did not impair long-term midfacial growth in the rabbit model and suggest that compensatory changes may have occurred at fracture lines from the self-tapping screws in these animals. PMID:1298421

Mooney, M P; Losken, H W; Siegel, M I; Tsachakaloff, A; Losken, A; Janosky, J



[Growth and deformity after in situ fixation of slipped capital femoral epiphysis].  


Background: For mild to moderate slipped capital femoral epiphysis (SCFE) in situ fixation is the current treatment standard. However, concerning the implant selection (screw versus k-wires) as well as the prophylactic stabilisation of the non-affected hip, controversies still exist. The aim of this study was to analyse femoral residual growth and femoral deformities after in situ fixation of SCFE either with k-wires or screws. Patients and Methods: We conducted a retrospective analysis of the radiographs of adolescents treated for SCFE in our department between 01/2003 and 02/2011. To evaluate femoral growth the articulo-trochanteric distance, centro-trochanteric distance, caput-collum-diaphyseal angle, pin-joint ratio and pin-physis ratio were determined. The femoral deformity was assessed by measuring the sphericity of the femoral head. Degenerative changes were evaluated in the final radiographs. Statistical analysis was performed concerning differences between therapeutically and prophylactically treated hips as well as stabilisations with k-wires and screws. Results: A total of 22 patients (female : male = 14 : 8, mean age girls: 11 ± 1 years, boys: 13 ± 2 years) with 26 slipped capital femoral epiphyses was analysed. K-wires were used for fixation in 4 hips each therapeutically and prophylactically, 22 hips with SCFE and 14 non-affected hips were stabilised with screws. Treatment with screws did not lead to significantly earlier physeal closure than k-wire pinning. Regarding the femoral growth parameters a significant decrease in the articulo-trochanteric distance and CCD angle was detectable in all groups. The pin-joint ratio revealed an adequate residual growth in 58 % of the therapeutically and in 72 % of the prophylactically treated hips without significant difference between k-wires and screws. The pin-physis ratio demonstrated similar values. Regarding the femoral deformity the SCFE hips resulted in a significantly reduced sphericity, which remained unchanged during follow-up. The prophylactic stabilisation did not result in any deterioration of sphericity. Conclusion: The results of this study imply that further growth of the proximal femur after insertion of a sliding screw for in situ stabilisation of mild to moderate slipped capital femoral epiphysis does occur. Furthermore, an increase of deformity during follow-up through screw fixation as compared to pinning was not noticed. Hence, the assumption that screw fixation leads to permanent physeal impairment cannot be confirmed. The consideration of these results may be helpful for implant selection as well as indicating prophylactic surgery for non-affected hips. PMID:23963984

Druschel, C; Placzek, R; Funk, J F



In vitro and in vivo evaluations of nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) as a novel bioactive bone screw.  


In this study, we prepared nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) bioactive bone screws. The microstructure, morphology and coating of the screws were characterised, and the adhesion, proliferation and viability of MC3T3-E1 cells on n-HA/PA66/GF scaffolds were determined using scanning electron microscope, CCK-8 assays and cellular immunofluorescence analysis. The results confirmed that n-HA/PA66/GF scaffolds were biocompatible and had no negative effect on MC3T3-E1 cells in vitro. To investigate the in vivo biocompatibility, internal fixation properties and osteogenesis of the bioactive screws, both n-HA/PA66/GF screws and metallic screws were used to repair intercondylar femur fractures in dogs. General photography, CT examination, micro-CT examination, histological staining and biomechanical assays were performed at 4, 8, 12 and 24 weeks after operation. The n-HA/PA66/GF screws exhibited good biocompatibility, high mechanical strength and extensive osteogenesis in the host bone. Moreover, 24 weeks after implantation, the maximum push-out load of the bioactive screws was greater than that of the metallic screws. As shown by their good cytocompatibility, excellent biomechanical strength and fast formation and ingrowth of new bone, n-HA/PA66/GF screws are thus suitable for orthopaedic clinical applications. PMID:23861888

Su, Bao; Peng, Xiaohua; Jiang, Dianming; Wu, Jun; Qiao, Bo; Li, Weichao; Qi, Xiaotong



Retrieval of a migrated Axialif lumbosacral screw using fluoroscopic guidance with simultaneous real-time sigmoidoscopy; technical report.  


: Study design. Technical Report.Objective. This article describes the technique of using intra-operative sigmoidoscopy as an adjunct for retrieval of the Axialif lumbosacral screw after failure of lumbar fusion.Summary of Background Data. Minimally invasive axial lumbar interbody fusion devices have emerged over the last 3 years as an alternative to traditional surgery for the treatment of intractable back pain. No reports of inferior migration of the lumbosacral screw causing rectal symptoms have been previously described. A 32 year old firefighter with intractable lumbar back pain was treated with minimally invasive axial lumbar interbody fusion with L4-S1 pedical screw fixation. Over 18 months sequential imaging demonstrated loosening and migration of the axial screw 3.5cm inferiorly causing impression on the rectum and symptoms of tenesmus.Methods. Pre-operative sigmoidoscopy was performed to exclude rectal perforation. During retrieval of the lumbosacral screw, simultaneous sigmoidoscopy was performed to ensure the rectum was not damaged.Results. The lumbosacral screw was successfully removed using a pre-sacral approach. The patient's rectal symptoms improved post-operatively, and was discharged after 48 hours.Conclusion. For the retrieval of migrated Axialif lumboscral screws, intra-operative sigmoidoscopy is technically feasible and serves as a useful adjunct to ensure the integrity of the rectal mucosa is maintained. This technique can be used to avoid the potential morbidity of rectal perforation, and subsequent laparotomy and defunctioning colostomy. PMID:24042713

Wilson, Jrf; Timothy, A; Rao, J; Sagar, P M



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



Bilateral tubular minimally invasive approach for decompression, reduction and fixation in lumbosacral lythic spondylolisthesis.  


This video demonstrates the minimally invasive surgical technique used in a 56-year-old woman suffering from L-5 spondylolysis and grade 2 L5-S1 spondylolisthesis. The first author used expandable tubular retractors bilaterally to perform neural decompression, mini-open TLIF, spondylolysthesis reduction and L5-S1 pedicle screw fixation. L-5 cement augmentation was performed through cannulated and fenestrated screws to enhance resistance to screw pull-out secondary to reduction maneuvers. Sequential surgical steps related to microsurgery, spondylolysthesis reduction and instrumentation are shown and commented. We submit that in cases of lythic spondylolisthesis a bilateral traversing and exiting nerve roots decompression is a safer option prior to performing the deformity reduction and fixation; the proposed minimally invasive technique may help in reducing surgical morbidity and improving postoperative recovery. The video can be found here: PMID:23829858

Barbagallo, Giuseppe M V; Certo, Francesco; Sciacca, Giovanni; Albanese, Vincenzo



Technique tip: percutaneous fixation of partial incongruous lisfranc injuries in athletes.  


Open reduction with screw fixation is considered the standard surgical approach for injuries of the Lisfranc complex in athletes. However, multiple incisions are required, which increase the risk for postoperative complications. We present a novel percutaneous reduction and solid screw fixation technique that may be a viable option to address partial incongruous injuries of the Lisfranc complex in athletes. At our institution, no intraoperative or postoperative complications have been encountered. Screw breakage did not occur. Reduction of the second metatarsal was considered anatomic across all patients. All patients have returned to their respective sport without limitation. The percutaneous approach appears to decrease complications while the targeting-reduction guide appears to precisely reduce the injury. Consequently, outcomes have been more consistent and predictable. The authors note that this percutaneous approach is specific to partial incongruous injuries of the Lisfranc complex. When presented with more extensive injuries, the authors advocate an open approach. PMID:23631892

Bleazey, Scott T; Brigido, Stephen A; Protzman, Nicole M



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.



Photographic fixative poisoning  


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


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

PubMed Central

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

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



A biomechanical study of the fatigue characteristics of thoracolumbar fixation implants in a calf spine model.  


Clinical failures of internal fixation implants for the treatment of the thoracolumbar spine are generally attributed to fatigue. Few studies, however, have characterized changes in fixation rigidity with time or subjected spine-implant fixation constructs to fatigue loading until failure. Fatigue characteristics of five dorsally applied spinal fixation implants were determined using lumbosacral calf spines, with an L3 vertebrectomy, loaded cyclically in combined compression (maximum 605 N) and flexion (maximum 16 Nm) for up to 100,000 cycles. Displacement transducers monitored motion at the site of instability and at the segment above the implants. Flexibility and strain at these segments were then calculated. A one-way analysis of variance showed that there were no significant differences in flexibility of the five fixation constructs (P greater than .05). A multiple Bonferroni test revealed that the AO and Kluger fixateur interne and Steffee plates, with fixation at L2 and L4, allowed significantly more strain (P less than .01) across the site of instability than did Harrington rods and Luque plates with fixation at L1, L2, L4, and L5. There were no significant differences between fixation constructs in initial strain above the implants. After 10,000 cycles, however, there were significant increases in strain across the segment above the Luque and Harrington implants (P less than .05). Failure of the AO Schanz screw occurred in three of six constructs at a mean of 73,300 cycles. The Steffee screws failed in four of five constructs at a mean of 20,800 cycles. The rods of the Kluger fixateur interne broke in four of five constructs at a mean of 47,800 cycles, and one screw slipped at 11,000 cycles. There were no metal failures in the Harrington or Luque implants.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1631711

Wittenberg, R H; Shea, M; Edwards, W T; Swartz, D E; White, A A; Hayes, W C



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.



Titanium Expandable Pedicle Screw for the Treatment of Degenerative and Traumatic Spinal Diseases in Osteoporotic Patients: Preliminary Experience.  


Osteoporosis is a major global health problem, with over 10 million people currently diagnosed with the disease. Although 80% of osteoporotic patients are women, a considerable number of men are also affected. Also, due to increasing life expectancy, the number of elderly patients with osteoporosis affected by degenerative and traumatic spinal diseases will increase further. Osteoporosis reduces bone quality through negative bone remodelling. Low bone quality can reduce the pull-out strength of pedicle screw, and negative bone remodelling can cause delayed bone fusion. However, pedicle screw instrumentation of the osteoporotic spine carries an increased risk of screw loosening, pull-out, and fixation failure. Our preliminary study aims to investigate the efficiency of expandable pedicle screws (OsseoScrew-Zodiac,® Scient'x® Alphatec Spine Inc, Carlsbad, CA) in osteoporotic spinal patients. All osteoporotic patients with degenerative and traumatic spinal diseases admitted in our department underwent a pre-operative spinal x-Ray and MRI or CT. Pre-operative clinical assesment of patients was based on the visual analog scale (VAS) and Owestry Disability (ODI) questionnaire-a disease-specific outcome measure. Ten osteoporotic patients were treated with expandable pedicle screws (OsseoScrew®). Post-operative clinical assessment of patients was based on the VAS and ODI questionnaire at 3 months and 1 year of follow-up. Post-operative radiologic follow-up was performed after 3 days (CT, x-ray); 3 months (xray); 6 months (spinal CT); and 1 year (spinal CT). Expandable pedicle screws improved pull-out strength as compared to standard pedicle screws in steoporotic patients with degenerative and traumatic spinal diseases. PMID:23023577

Gazzeri, Roberto; Roperto, Raffaelino; Fiore, Claudio



Experimental and finite element comparison of various fixation designs in combined loads.  


The short- and long-term successes of tibial cementless implants depend on the initial fixation stability often provided by posts and screws. In this work, a metallic plate was fixed to a polyurethane block with either two bone screws, two smooth-surfaced posts, or two novel smooth-surfaced posts with adjustable inclinations. For this last case, inclinations of 0, 1.5, and 3 deg were considered following insertion. A load of 1031 N was eccentrically applied on the plate at an angle of approximately 14 deg, which resulted in a 1000 N axial compressive force and a 250 N shear force. The response was measured under static and repetitive loading up to 4000 cycles at 1 Hz. The measured results demonstrate subsidence under load, lift-off on the unloaded side, and horizontal translation of the plate specially at the loaded side. Fatigue loading increased the displacements, primarily during the first 100 cycles. Comparison of various fixation systems indicated that the plate with screw fixation was the stiffest with the least subsidence and liftoff. The increase in post inclination from 0 to 3 deg stiffened the plate by diminishing the liftoff. All fixation systems demonstrated deterioration under repetitive loads. In general, the finite element predictions of the experimental fixation systems were in agreement with measurements. The finite element analyses showed that porous coated posts (modeled with nonlinear interface friction with and without coupling) generated slightly less resistance to liftoff than smooth-surfaced posts. In the presence of porous coated posts, Coulomb friction greatly overestimated the rigidity by reducing the liftoff and subsidence to levels even smaller than those predicted for the design with screw fixation. The sequence of combined load application also influenced the predicted response. Finally, the finite element model incorporating measured interface friction and pull-out responses can be used for the analysis of cementless total joint replacement systems during the post-operation period. PMID:11601722

Shirazi-Adl, A; Patenaude, O; Dammak, M; Zukor, D



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



Evaluation of unilateral cage-instrumented fixation for lumbar spine  

PubMed Central

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



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



High energy tibial plateau fractures treated with hybrid external fixation  

PubMed Central

Management of high energy intra-articular fractures of the proximal tibia, associated with marked soft-tissue trauma, can be challenging, requiring the combination of accurate reduction and minimal invasive techniques. The purpose of this study was to evaluate whether minimal intervention and hybrid external fixation of such fractures using the Orthofix system provide an acceptable treatment outcome with less complications. Between 2002 and 2006, 33 patients with a median ISS of 14.3 were admitted to our hospital, a level I trauma centre, with a bicondylar tibial plateau fracture. Five of them sustained an open fracture. All patients were treated with a hybrid external fixator. In 19 of them, minimal open reduction and stabilization, by means of cannulated screws, was performed. Mean follow-up was 27 months (range 24 to 36 months). Radiographic evidence of union was observed at 3.4 months (range 3 to 7 months). Time for union was different in patients with closed and grade I open fractures compared to patients with grade II and III open fractures. One non-union (septic) was observed (3.0%), requiring revision surgery. Pin track infection was observed in 3 patients (9.1%). Compared to previously reported series of conventional open reduction and internal fixation, hybrid external fixation with or without open reduction and minimal internal fixation with the Orthofix system, was associated with satisfactory clinical and radiographic results and limited complications.



Outcome of complex tibial plateau fractures treated with external fixator  

PubMed Central

Background: Tibial plateau fractures are usually associated with communition and soft tissue injury. Percutaneous treatment of these complex fractures is intended to reduce soft issue complications and postoperative stiffness of the knee joint. We assessed the complications, clinical outcome scores, and postoperative knee range of movements, after fluoroscopic assisted closed reduction and external fixator application. Materials and Methods: Seventy eight complex tibial plateau fractures in 78 patients were included in the study. All fractures were managed with closed reduction and external fixator application. In 28 cases with intraarticular split, we used percutaneous cancellous screw fixation for reduction and fixation of condylar parts. In nine open fractures, immediate debridement was done. In 16 cases, elevation of depressed segment and bone grafting was required, which was done from a very small incision. All patients were clinically and radiographically evaluated at a mean followup of 26.16 months (range 6–60 months). Results: Clinical results were evaluated according to the Rasmussen's criteria. Average healing time was 13.69 weeks (range 12– 28 weeks). Mean knee range of motion was 122.60° (range 110°–130°). Forty seven results were scored as excellent, 25 good, 2 fair, and 1 as poor. Conclusion: We believe that minimally invasive treatment by percutaneous techniques and external fixation is a fairly reasonable treatment alternative, if near anatomical reduction of joint surface can be confirmed on fluoroscopy.

Mankar, Sushil H; Golhar, Anil V; Shukla, Mayank; Badwaik, Prashant S; Faizan, Mohammad; Kalkotwar, Sameer



Cancellous bone screw purchase: a comparison of synthetic femurs, human femurs, and finite element analysis.  


Biomechanical assessments of orthopaedic fracture fixation constructs are increasingly using commercially available analogues such as the fourth-generation composite femur (4GCF). The aim of this study was to compare cancellous screw purchase directly between these surrogates and human femurs, which has not been done previously. Synthetic and human femurs each had one orthopaedic cancellous screw (major diameter, 6.5 mm) inserted along the femoral neck axis and into the spongy bone of the femoral head to a depth of 30 mm. Screws were removed to obtain pull-out force, shear stress, and energy values. The three experimental study groups (n = 6 femurs each) were the 4GCF with a 'solid' cancellous matrix, the 4GCF with a 'cellular' cancellous matrix, and human femurs. Moreover, a finite element model was developed on the basis of the material properties and anatomical geometry of the two synthetic femurs in order to assess cancellous screw purchase. The results for force, shear stress, and energy respectively were as follows: 4GCF solid femurs, 926.47 +/- 66.76 N, 2.84 +/- 0.20 MPa, and 0.57 +/- 0.04 J; 4GCF cellular femurs, 1409.64 +/- 133.36 N, 4.31 +/- 0.41 MPa, and 0.99 +/- 0.13 J; human femurs, 1523.29 +/- 1380.15N, 4.66 +/- 4.22 MPa, and 2.78 +/- 3.61J. No statistical differences were noted when comparing the three experimental groups for pull-out force (p = 0.413), shear stress (p = 0.412), or energy (p = 0.185). The 4GCF with either a 'solid' or 'cellular' cancellous matrix is a good biomechanical analogue to the human femur at the screw thread-bone interface. This is the first study to perform a three-way investigation of cancellous screw purchase using 4GCFs, human femurs, and finite element analysis. PMID:19143412

Zdero, R; Olsen, M; Bougherara, H; Schemitsch, E H



Rigid internal fixation with titanium versus bioresorbable miniplates in the repair of mandibular fractures in rabbits.  


The purpose of this study was to compare by qualitative histology the efficacy of rigid internal fixation with titanium system and the Lacto Sorb system in mandibular fractures in rabbits. Thirty male adult rabbits Oryctolagus cuniculus were used. Unilateral mandibular osteotomies were performed between the canine and first premolar. The animals were divided into two groups: for Group I-rigid internal fixation was performed with titanium system 1.5 mm (Synthes, Oberdorf, Switzerland), with two screws of 6 mm (bicortical) on each side of the osteotomy. For Group II-rigid internal fixation was performed with PLLA/PGA system 1.5 mm (Lacto Sorb, WLorenz, Jacksonville, FL, USA). The histological analysis evaluated the presence of inflammatory reaction, degree of bone healing and degree of resorption of the Lacto Sorb screws. The results of both fixation systems were similar, only with a small difference after 15 and 30 days. In Group I a faster bony healing was noted. But after 60 days, bony healing was similar in both groups. It is concluded that both PLLA/PGA and titanium plates and screws provide sufficient strength to permit mandibular bone healing. The resorption process of PLLA/PGA osteosynthesis material did not cause acute or chronic inflammatory reaction or foreign body reaction during the studied period. PMID:15695046

Hochuli-Vieira, E; Cabrini Gabrielli, M A; Pereira-Filho, V A; Gabrielli, M F R; Padilha, J G



Mechanical comparison of two types of fixation for ludloff oblique first metatarsal osteotomy.  


The Ludloff oblique metatarsal osteotomy is an effective method to correct hallux valgus deformity, although a number of problems have been associated with it, including inherent instability, delayed union, dorsal malunion, and fixation failure. The purpose of the present study was to compare the mechanical characteristics of fixation of the Ludloff osteotomy in 20 identical synthetic bone models, 10 fixated using 2 screws (group I) and 10 fixated using 2 screws augmented with a mini locking plate (group II). Each specimen was loaded to failure, and the mean average load to failure, stiffness, and absorbed energy to failure were compared using unpaired Student's t test. The mean average stiffness of the Ludloff osteotomy fixed with 2 screws (group I) and with the supplementary mini locking plate (group II) was 172.7 ± 31.7 N/mm and 193.3 ± 39 N/mm, respectively (p = .21). The mean average load to failure for groups I and II was 278.4 ± 64.4 N and 356.2 ± 77.9 N, respectively (p = .025). The mean average energy absorbed before failure for groups I and II was 506.7 ± 206.4 Nmm and 769.8 ± 339.4 Nmm, respectively (p = .05). The use of a medially applied supplementary mini locking plate offers a simple and effective method to improve the mechanical stability of the Ludloff oblique osteotomy. PMID:21813302

Tsilikas, Stavros P; Stamatis, Emmanouil D; Kourkoulis, Stavros K; Mitousoudis, Athanasios S; Chatzistergos, Panayiotis E; Papagelopoulos, Panayiotis J



Mechanical stability analysis of reference clamp fixation in computer-assisted spine surgery  

Microsoft Academic Search

Background  Pedicle screw misplacement is a common complication, while 7% may result in neurological complications. Computer-assisted\\u000a navigation improves the rate of ideally placed screws. Inappropriate reference marker attachment can cause major problems\\u000a in the outcome and duration of surgery.\\u000a \\u000a \\u000a \\u000a \\u000a Objective  To improve fixation of reference bases by comparing different designs of spine clamps and measuring their stability against\\u000a the relevant thoracic and

Nesrin Uksul; Eduardo M. Suero; Timo Stübig; Mustafa Citak; Tobias Hüfner; Christian Krettek; Musa Citak



Measures for Protection Against Abrasion on Screws Used in Extruding Ceramic Compounds  

NASA Astrophysics Data System (ADS)

In the ceramic industry, the materials and additives used in the extrusion process result in heavy wear on the screws and barrels. To counteract this effect, it is crucial that the processing units are designed to provide an economically acceptable working life. The screws should also be able to be re-coated i.e. used several times to reduce the cost-to-working-life ratio. There are various means for providing protection against premature wear.

Reisinger, Walter


The Search for the Ideal Fixation of Palatal Fractures: Innovative Experience with a Mini-Locking Plate  

PubMed Central

Fractures of the palate have defied conventional management, such that malrotation and disinclination of the palatal shelves occur in a significant number of patients after repair. The fractured palatal shelves of eight patients were first prealigned. To do so, one or more 205-mm ratchet clamps and two intermaxillary fixation (IMF) posts were used. Rigid fixation was then achieved by applying a 2.0-mm mini-locking titanium plate (across the palatal vault) and by applying an adaptation miniplate across the fracture line as it exited the anterior surface of the maxilla. Screws were passed directly through the mucoperiosteum, to engage the palatal shelves and to lock the locking plate into position. Lacerations in the mucoperiosteum were neither used to aid fixation nor used as portals for dissection; incisions and mucoperiosteal flaps in the palatal vault were avoided. Adjuncts, such as intraoral splints, have not been used in cases to date, and early mobilization was allowed. Reconstitution of the craniomaxillofacial buttresses was added in patients with more extensive maxillary injury. The palatal appliance and screws remained rigidly in position in the roof of the mouth, much like an external fixator, until their removal 8 to 12 weeks after the repair. No patient suffered erosion of the mucoperiosteum or other major morbidity, other than a transient fistula of the soft palate. The palatoalveolar segments remained in proper realignment and inclination, and pretraumatic occlusal patterns and the width and depth of the lower face appear to have been restored with one exception. The latter suffered a subtle posterolateral open bite that was corrected orthodontically. Prealignment of fractured palatal shelves with one or more large ratchet clamps and two IMF posts provides several points of forced reduction of the palatal shelves, along the dental arch. In addition, stabilization with mini-locking plate(s) in the palatal vault and an adaptation plate across the fracture line, as it exits the maxilla, appear to have merit, based on this preliminary report (n?=?8). Outcomes seen on computed tomography and clinical examination during this 3-year experience have been favorable.

Pollock, Richard A.



Internal Fixation for Fractures  


... American Academy of Orthopaedic Surgeons Internal Fixation for Fractures When members of the American Academy of Orthopaedic ... bones together. Can be used alone to treat fractures of small bones, such as those found in ...


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



Prospective randomized clinical comparison of femoral transfixation versus bioscrew fixation in hamstring tendon ACL reconstruction—a preliminary report  

Microsoft Academic Search

The purpose of this study is to clinically evaluate hamstring tendon anterior cruciate ligament (ACL)-reconstruction using femoral fixation with bioresorbable interference screws and with a bioresorbable transfixation device. The ACL-reconstruction using the transfixation device at the femoral side leads to less knee laxity and therefore to a better clinical outcome for the patient. Prospective randomized clinical outcome study. From February

Tim Rose; Pierre Hepp; Julia Venus; Christoph Stockmar; Christoph Josten; Helmut Lill



The meniscus Arrow or metal screw for treatment of osteochondritis dissecans? In vitro comparison of their effectiveness.  


Three draw bench tests in axial direction were conducted of the pull out forces in predrilled human condylar bone of one single meniscus Arrow, one single metal screw, and three Meniscus Arrows in one bone block, the Arrows being inserted using the standard hand instruments. Bone blocks with three meniscus Arrows were tested additionally in tangential direction, imitating shear forces. All observed values were within the range of 1 standard error (SE) or higher and exceeded the values in meniscal tissue as reported in the literature. These are much higher than the shear force during a single movement in the human knee. Most metallic devices used for fixation of the fragments in the treatment of osteochondritis dissecans must be removed in a second operation. Left in place, as with the Herbert screws, they can disturb future imaging and damage the opposite cartilage of the tibia plateau. Staples left in place can break. Finally, some metals evoke allergic reactions and, at least in animals, are potent carcinogens. Although fusion of osteochondritis dissecans fragments in their original locations fixed with noncompressive biodegradable pins has been reported, these tests show the hold of compressive meniscus Arrows in bone to contribute to a better result than noncompressive pins. Other biodegradable devices are also available for this application. However, one advantage is that using meniscus Arrows, already available in the hospital for mending ruptured menisci, saves the costs of investing in other sets of instruments and devices. Another advantage is the smaller diameter of the meniscus Arrows than that of other biodegradable devices, resulting in less damage to the fragments. PMID:14586489

Wouters, Diederick B; Bos, Rudolf R M; Mouton, Leonora J; van Horn, Jim R



An internal fixator for posterior application to short segments of the thoracic, lumbar, or lumbosacral spine. Design and testing.  


A new spinal implant has been designed and biomechanical testing completed, intended for application to "short-segment" spinal defects such as disc degeneration, fracture, spondylolisthesis, or tumor. Major improvements over currently available devices include: only 2-3 vertebrae are spanned, not 5-7 as with Harrington rods; true three-dimensional fixation is achieved, preventing such problems as hook or rod dislocation; three-dimensional adjustment is easily accomplished, allowing fracture or spondylolisthesis reduction to be readily performed; attachment to vertebrae is by means of transpedicular screws eliminating deliberate encroachment into the spinal canal, such as Luque wires or Harrington hooks; no special alignment between screws is needed (such as with holes or slots in a plate), allowing screw placement to fully conform to anatomic structures; and laminectomy sites and lumbosacral junction are readily instrumented. Background investigations presented here for design of this device include: CT-defined pedicle morphometry showing that screws may be larger than those currently used; effect of pitch, minor diameter, and tooth profile on screw pull-out strength; mechanical testing of a compact, three-dimensionally adjustable, strong, nonloosening articulating clamp; and establishing of the relationship between depth of penetration and strength of fixation of transpeduncular screws. PMID:3956000

Krag, M H; Beynnon, B D; Pope, M H; Frymoyer, J W; Haugh, L D; Weaver, D L



Automatic determination of pedicle screw size, length, and trajectory from patient data.  


Pedicle screw insertion is an orthopaedic spinal fixation procedure involving the placement of screws through individual spine pedicles and secured in spinal vertebrae. Pedicle anatomy varies widely within and across the patient population, and many complications have been reported with the surgical technique. To reduce complications, an automated procedure was developed that utilizes patient-specific medical imaging data to predetermine optimum pedicle screw size, length, and trajectory. The procedure involves importing medical imaging scans into the software, creating uniform voxel data for algorithm simplicity, segmenting the bony anatomy of the spine and defining its boundary, and identifying the pedicle using a search algorithm. The operations are performed in two-dimensions in the coordinate system of the medical imaging data. For each image slice, the minimum pedicle width is identified, and examining all slices identifies the overall minimum pedicle width. The optimum trajectory is determined using a 3D linear least squares fit to the array of minimum pedicle width midpoints. With the optimum trajectory determined, the maximum screw size and length are determined. PMID:17271977

Wicker, Ryan; Tedla, Buz



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



Universal Clamp system in thoracolumbar spinal fixation: technical note  

Microsoft Academic Search

Background  The Universal Clamp is a polyester band passed under the lamina and connected to a rod by a titanium clamp that has been recently\\u000a reported as an alternative for replacing screws and hooks for thoracolumbar spinal diseases. To date, there is no report of\\u000a an evaluation of the effectiveness and safety of posterior fixation and fusion using this technique.\\u000a \\u000a \\u000a \\u000a Methods  This

Roberto Gazzeri; Andrea Faiola; Marcelo Galarza; Marco Tamorri



Navigation of vertebro-pelvic fixations based on CT-fluoro matching  

PubMed Central

Different navigation procedures (based on 2D-, 3D-fluoroscopy or CT modalities) with their respective limitations are established in orthopedic surgery. The hypothesis is that intraoperative matching of different modalities (fluoro and CT) increases the precision of navigated screw placement and reduces the fluoroscopy time. Vertical unstable pelvic ring fractures of 12 patients were treated with vertebro-pelvic fixations (6 in the standard technique and 6 using the fluoro-CT navigation). An optimal osseous corridor could be determined by the navigation procedure increasing the overall precision of screw placement (no misplacement in the second group as compared to one malplaced pedicle screw in the standard group). The achieved screw lengths were [(mean ± SE) 78 ± 5 vs. 53 ± 4 mm, p < 0.001). Less invasive open approaches and a reduction of fluoroscopy time (time per screw in seconds: 121 vs. 62 s) were observed. CT-fluoro-matched navigation improves the intraoperative visualization of osseous structures and increases the precision of screw placement with less radiation exposure.

Gras, Florian; Klos, Kajetan; Wilharm, Arne; Muckley, Thomas; Hofmann, Gunther O.



Biomechanical failure of metacarpal fracture resorbable plate fixation.  


Metacarpal fractures are a relatively common hand injury that may require operative intervention to ensure adequate reduction and stabilization. The use of permanent hardware, although acceptable, may lead to complications and an increased number of surgical procedures. The use of resorbable hardware such as poly-L-lactic acid and polyglycolic acid copolymer plates and screws may circumvent some of these complications. In vitro studies have demonstrated that the biomechanical characteristics of these resorbable plates may provide the rigid fixation necessary to allow for union of metacarpal fractures in vivo. However, limited clinical data are available regarding the success of their use in this application. The authors present what they believe is the first reported case of the failure of a poly-L-lactic acid and polyglycolic acid copolymer miniplate after use in the fixation of a metacarpal shaft fracture. PMID:12187350

Lionelli, Gerald T; Korentager, Richard A



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.



Screw elastic intramedullary nail for the management of adult forearm fractures  

PubMed Central

Background: The failure of the conventional nailing of both forearm bones or isolated fractures of radius and ulna pose a potential problem of nail migration and rotational instability, despite the best reduction. The purpose of this paper is to evaluate the results of screw elastic intramedullary nail for the treatment of adult diaphyseal fractures of both forearm bones, which effectively addresses the problems associated with the conventional nailing systems for the forearm fractures. Materials and Methods: Seventy-six adults with forearm fractures (radius and ulna or isolated fracture of the single bone) were retrospectively evaluated. Fifty males and 26 females with the mean age of 38 years (range, 18-70 years) underwent closed reduction and screw intramedullary nail fixation. Ten patients required limited open reduction. The fractures were classified according to the AO/OTA system. The average followup was 12 months (range, 6 to 18 months). Results: The mean surgical time was 45 minutes (35 to 65 minutes). The meantime to union was 14 weeks (10-21 weeks). The results were graded as excellent in 50, good in 18 patients, and acceptable in eight patients, using the criteria of Grace and Eversman. We had superficial infection in three cases, one case of delayed infection, painful bursa in two cases, delayed union in two cases, malunion with dislocation of the DRUJ in two cases, injury to the extensor tendon of the thumb in one case, and one case of incomplete radioulnar synostosis. Conclusion: Closed reduction and internal fixation of forearm fractures by screw intramedullary nails reestablishes the near normal relationship of the fractured fragments. Screw intramedullary nail effectively controls both rotatory forces and the migration of the nail. It produces excellent clinical results in isolated fractures of either bones, as well as both bones of the forearm in adults.

Gadegone, Wasudeo; Salphale, Yogesh S; Lokhande, Vijayanand



Load Sharing Mechanism Across Graft-Bone Interface in Static Cervical Locking Plate Fixation  

PubMed Central

Objective This study is a retrospective clinical study over more than 4 years of follow up to understand the mechanism of load sharing across the graft-bone interface in the static locking plate (SLP) fixation compared with non-locking plate (NLP). Methods Orion locking plates and Top non-locking plates were used for SLP fixation in 29 patients and NLP fixation in 24 patients, respectively. Successful interbody fusion was estimated by dynamic X-ray films. The checking parameters were as follows : screw angle (SA) between upper and lower screw, anterior and posterior height of fusion segment between upper and lower endplate (AH & PH), and upper and lower distance from vertebral endplate to the end of plate (UD & LD). Each follow-up value of AH and PH were compared to initial values. Contributions of upper and lower collapse to whole segment collapse were estimated. Results Successful intervertebral bone fusion rate was 100% in the SLP group and 92% in the NLP group. The follow-up mean value of SA in SLP group was not significantly changed compared with initial value, but follow-up mean value of SA in NLP group decreased more than those in SLP group (p=0.0067). Statistical analysis did not show a significant difference in the change in AH and PH between SLP and NLP groups (p>0.05). Follow-up AH of NLP group showed more collapse than PH of same group (p=0.04). The upper portion of the vertebral body collapsed more than the lower portion in the SLP fixation (p=0.00058). Conclusion The fused segments with SLP had successful bone fusion without change in initial screw angle, which was not observed in NLP fixation. It suggests that there was enough load sharing across bone-graft interface in SLP fixation.

Han, In Ho; Kuh, Sung Uk; Chin, Dong Kyu; Jin, Byung Ho; Cho, Yong Eun



Posterior instrumentation and fusion for unstable fractures and fracture-dislocations of the thoracic and lumbar spine. A comparative study of three fixation devices in 70 patients.  


Acute unstable thoracic and lumbar spine fractures were treated with either Harrington rods and hooks, Luque rods with sublaminar wires, or A-O dynamic compression plates with pedicle screws. The results demonstrated failure of all three techniques to maintain the sagittal plane correction at 12 months' follow-up. Furthermore, in lumbar fractures, Harrington rods did not restore or maintain sagittal plane alignment as well as Luque rods or pedicle screws and plates. Lastly, the pedicle screw fixation system required a shorter segment fusion. PMID:8470006

Sasso, R C; Cotler, H B



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.



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



[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



Delayed pericarditis associated with an implantable cardioverter defibrillator implantation using an active-fixation atrial lead.  


A 57-year-old man with nonischemic dilated cardiomyopathy and ventricular tachycardia underwent routine dual chamber implantable cardioverter defibrillator (ICD) implantation. An active-fixation atrial lead was positioned at the lateral wall of the right atrium. He subsequently developed chronic severe pericarditis. Histopathological findings of the pericardium showed mechanical stimulus localized pericarditis. This case demonstrates that contact of the screw of the active-fixation atrial lead with the pericardium may be a possible mechanism for pericarditis after pacemaker/ICD implantation. PMID:18439181

Kono, Koichi; Todoroki, Masakatsu; Karasawa, Tsuyoshi; Ito, Itaru; Tadokoro, Kazuyoshi; Shinbo, Goro; Horinaka, Shigeo; Matsuoka, Hiroaki; Mochizuki, Yoshihiko



Arthroscopically-assisted reduction and fixation of an old osteochondral fracture of the lateral femoral condyle  

PubMed Central

Summary Background Osteochondral fracture (OCF) of the lateral femoral condyle has a low incidence and old OCF is even more rarely seen; it is difficult to differentiate from late osteochondritis dissecans (OCD). Case Report In this report, we present the case of a 20-year-old male patient with an old OCF of the lateral femoral condyle. The possible etiology of OCF is discussed, along with its clinical manifestation, diagnosis, and treatment. He underwent arthroscopically-assisted reduction and fixation with cannulated screws. Four months after the surgery, arthroscopy showed good osteochondral healing, and screws were removed. He had achieved good functional recovery by the follow-up visit. Conclusions Old OCF should be distinguished from OCD in clinical practice, and osteochondral bodies should be preserved as much as possible. Osteochondral reduction and fixation under arthroscopy was minimal and the clinical effect was good.

Li, Runguang; Guo, Gang; Chen, Bin; Zhu, Lijun; Lin, Angru



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



Improving carbon fixation pathways.  


A recent resurgence in basic and applied research on photosynthesis has been driven in part by recognition that fulfilling future food and energy requirements will necessitate improvements in crop carbon-fixation efficiencies. Photosynthesis in traditional terrestrial crops is being reexamined in light of molecular strategies employed by photosynthetic microbes to enhance the activity of the Calvin cycle. Synthetic biology is well-situated to provide original approaches for compartmentalizing and enhancing photosynthetic reactions in a species independent manner. Furthermore, the elucidation of alternative carbon-fixation routes distinct from the Calvin cycle raises possibilities that novel pathways and organisms can be utilized to fix atmospheric carbon dioxide into useful materials. PMID:22647231

Ducat, Daniel C; Silver, Pamela A



Improving Carbon Fixation Pathways  

PubMed Central

A recent resurgence in basic and applied research on photosynthesis has been driven in part by recognition that fulfilling future food and energy requirements will necessitate improvements in crop carbon-fixation efficiencies. Photosynthesis in traditional terrestrial crops is being reexamined in light of molecular strategies employed by photosynthetic microbes to enhance the activity of the Calvin cycle. Synthetic biology is well-situated to provide original approaches for compartmentalizing and enhancing photosynthetic reactions in a species independent manner. Furthermore, the elucidation of alternative carbon-fixation routes distinct from the Calvin cycle raises possibilities that alternative pathways and organisms can be utilized to fix atmospheric carbon dioxide into useful materials.

Ducat, Daniel C.



Variable fixation of staphylococcal slime by different histochemical fixatives  

Microsoft Academic Search

A variety of histochemical fixatives were used to compare the fixation of bacterial films produced by a standard slime-producing strain ofStaphylococcus epidermidis on plastic tissue culture plates. Some reagents were completely ineffective in fixing the slime layer, whereas others gave variable results. The best alternative to the fixative of the reference method, the potentially explosive Bouin's reagent, was air drying.

L. Baldassarri; W. A. Simpson; G. Donelli; G. D. Christensen



Meniscus bucket-handle fixation with an absorbable biofix tack: development of a new technique  

Microsoft Academic Search

The authors present a new method for fixation of meniscus bucket-handle lesions. This technique is based on the development of a Biofix self-reinforced polylactic acid tack and an application system. The main goal of this technique has been to eliminate or at least reduce the risk of neurovascular injury during meniscus fixation and to simplify the fixation procedure. Additional skin

P. Albrecht-Olsen; G. Kristensen; P. Tiirmiilii



The flying buttress construct for posterior spinopelvic fixation: a technical note  

Microsoft Academic Search

Background  Posterior fusion of the spine to the pelvis in paediatric and adult spinal deformity is still challenging. Especially assembling\\u000a of the posterior rod construct to the iliac screw is considered technically difficult. A variety of spinopelvic fixation techniques\\u000a have been developed. However, extreme bending of the longitudinal rods or the use of 90-degree lateral offset connectors proved\\u000a to be difficult,

Barend J van Royen; Martijn van Dijk; Dirk PH van Oostveen; Bas van Ooij; Agnita Stadhouder



Fixative for fixing biological materials  

US Patent & Trademark Office Database

A fixative for fixing biological materials contains a depot agent, preferably a polyamine and especially hexamethylenetetramine, which reacts chemically with positively charged ions, especially H+ from an acid, while forming a fixative, where the fixative is an aldehyde and especially formaldehyde, which in turn reacts chemically with the biological material to be fixed in order to fix it and is consumed in doing so. By adjusting the pH of a solution containing the depot agent, a chemical equilibrium reaction occurs between the depot agent, fixative and biological material, so that just as much fixative is continuously formed as can be immediately consumed by the biological material. With that, the fixative, and especially the hazardous formaldehyde, cannot escape. Thus, an externally formaldehyde-free fixative that at the same time has the excellent fixative properties of formaldehyde is created.

Szabados; Andreas (Grunwald, DE); Gerigk; Roberto (Muhldorf a. Inn, DE)



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


Nitrogen fixation and nitrogen fertilization of soybeans.  


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

Merbach, W; Jacob, H J



Rapid Two-Temperature Formalin Fixation  

PubMed Central

Formalin fixation is a mainstay of modern histopathologic analysis, yet the practice is poorly standardized and a significant potential source of preanalytical errors. Concerns of workflow and turnaround time drive interest in developing shorter fixation protocols, but rapid protocols can lead to poor histomorphology or inadequate downstream assay results. Additionally, assays such as immunohistochemistry for phosphorylated epitopes have historically been challenging in the context of formalin-fixed tissue, indicating that there may be room for improvement in this process that is fundamental to the practice of anatomic pathology. With these issues in mind, we studied basic formalin biochemistry to develop a novel formalin fixation protocol that involves a pre-incubation in subambient temperature formalin prior to a brief exposure to heated formalin. This new protocol is more rapid than standard protocols yet preserves histomorphology and yields tissue that is compatible with an expanded set of downstream clinical and research assays, including immunohistochemistry for phosphorylated epitopes.

Roberts, Esteban; Borlee, Grace; Otter, Michael; Baird, Geoffrey S.



Rapid two-temperature formalin fixation.  


Formalin fixation is a mainstay of modern histopathologic analysis, yet the practice is poorly standardized and a significant potential source of preanalytical errors. Concerns of workflow and turnaround time drive interest in developing shorter fixation protocols, but rapid protocols can lead to poor histomorphology or inadequate downstream assay results. Additionally, assays such as immunohistochemistry for phosphorylated epitopes have historically been challenging in the context of formalin-fixed tissue, indicating that there may be room for improvement in this process that is fundamental to the practice of anatomic pathology. With these issues in mind, we studied basic formalin biochemistry to develop a novel formalin fixation protocol that involves a pre-incubation in subambient temperature formalin prior to a brief exposure to heated formalin. This new protocol is more rapid than standard protocols yet preserves histomorphology and yields tissue that is compatible with an expanded set of downstream clinical and research assays, including immunohistochemistry for phosphorylated epitopes. PMID:23349806

Chafin, David; Theiss, Abbey; Roberts, Esteban; Borlee, Grace; Otter, Michael; Baird, Geoffrey S



The Fixation of Nitrogen.  

ERIC Educational Resources Information Center

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

Andrew, S. P. S.



Carbon dioxide fixation.  

National Technical Information Service (NTIS)

Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO(sub 2) conv...

E. Fujita



Nitrogen Fixation by Gloeocapsa  

Microsoft Academic Search

The continuous growth in a medium free of combined nitrogen and the experimental production of ethylene via acetylene reduction indicate that nitrogen fixation by blue-green algae is not solely confined to filamentous genera with heterocysts. Axenic cultures of Gloeocapsa sp., adapted to nitrate-free medium, form ethylene at rates comparable to those of species known to fix nitrogen.

J. T. Wyatt; J. K. G. Silvey



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



Management of acute displaced midshaft clavicular fractures using Herbert cannulated screw: Technique and results in 114 patients  

PubMed Central

Purpose: A new and simple operative technique has been developed to provide internal fixation for midshaft clavicle fractures. This involves the use of a large fragment Herbert Screw that is entirely embedded within the bone. Screw fixation is combined with bone grafting from intramedullary reamings of the fracture fragments. The purpose of this report is to assess the outcomes following treatment of midshaft clavicular fracture using this method. Materials and Methods: One hundred and fourteen patients with acute displaced midshaft fracture were identified between 2002 and 2007. All patients were followed until fracture union. Patients’ medical records were reviewed. Disability of the Arm, Shoulder, and Hand questionnaire (DASH), and American Shoulder and Elbow Surgeons Elbow form (ASES) were posted to all patients. Outcome measures included union rate, time to union, implant removal rate, DASH, and ASES scores. Results: Patients’ median age was 29.5 years (interquartile range, 19-44 years). The most common injury mechanism was sports injury (28%). The median time from injury to surgery was 5 days (interquartile range, 2-9 days). Union occurred in an average of 8.8 weeks. Non-union occurred in three cases (2.6%). The re-operation rate for symptomatic hardware prominence screw was 1.7%. The median DASH score was 0.83 and the median ASES was 100 (n = 35). Conclusions: Intramedullary fixation using cannulated Herbert screw can be used as an effective approach for operative management of midshaft clavicular fractures. Using this method, an appropriate outcome could be achieved and a second intervention for implant removal could be avoided in great majority of cases. Level of Evidence: Level III

Richardson, Martin; Asadollahi, Saeed; Richardson, Louise



The preliminary study and tentative animal study on the sintered PDLLA/TCP composites as bone fracture internal fixation.  


Polyesters based on the lactic acid have been reported safety and biodegradation in the human beings for two decades. The greatest advantage of the material is its degradation only conducted by the hydrolysis, where the ester backbones are supposed to be unchained in the aqueous condition. The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment. The goal of this study was aimed to develop a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles as orthopedic application. The TCP particles in a range of 30-60 wt% (with 5 wt% increment) were doped into the PDLLA matrix for the reinforcement, which were prepared by the melting and hot pressing techniques. The basic mechanical strength, biodegradable behavior, and biological response of the composites will be investigated in the study. Various techniques, such as pH meter, UV, FTIR, XRD ect., were used to examine and record the degradable process of the composites soaked in the saline for 1-16 weeks. The rabbit femur condyle fracture fixation test was used to evaluate the tissue compatibility and the effects of bone fracture fixation of the composites. The histological observation and x-ray photography were applied for investigating assistance. In the histological evaluation of rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the new generated bone without fibrous tissue around after 8 weeks implantation. The fracture bone was gradually healing and the composite always firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling. The developed composite was thought to be an alternative material for orthopedic application in the future, especially in bone screw and bone plate. PMID:9603016

Lin, F H; Chen, T M; Lee, C J



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.



Correlation of the experimental and numerical results for the holding power of dental, traumatic, and spinal screws.  


The holding power of the bone-screw interfaces is one of the key factors in the clinical performance of screw design. The value of the holding power can be experimentally measured by pullout tests. Historically, some researchers have used the finite-element method to simulate the holding power of the different screws. Among them, however, the assumed displacement of the screw withdrawal is unreasonably small (about 0.005-1.0 mm). In addition, the chosen numerical indices are quite different, including maximum stress, strain energy, and reaction force. This study systematically uses dental, traumatic, and spinal screws to experimentally measure and numerically simulate their bone-purchasing ability within the synthetic bone. The testing results (pullout displacement and holding power) and numerical indices (maximum stress, total strain energy, and reaction forces) are chosen to calculate their correlation coefficients. The pullout displacement is divided into five regions from initial to final withdrawal. The experimental results demonstrate that the pullout displacement consistently occurs at the final region (0.6-1.6 mm) and is significantly higher than the assumed value of the literature studies. For all screw groups, the measured holding power within the initial region is not highly or even negatively correlated with the experimental and numerical results within the final region. The observation from the simulative results shows the maximum stress only reflects the loads concentrated at some local site(s) and is the least correlated to the measured holding power. Comparatively, both energy and force are more global indices to correlate with the gross failure at the bone-screw interfaces. However, the energy index is not suitable for the screw groups with rather tiny threads compared with the other specifications. In conclusion, the underestimated displacement leads to erroneous results in the screw-pullout simulation. Among three numerical indices the reaction-force is the optimal index for the screw-pullout problem. PMID:22269112

Lee, Chia-Ching; Lin, Shang-Chih; Wu, Shu-Wei; Li, Yu-Ching; Fu, Ping-Yuen



Percutaneous pedicle screw reduction and axial presacral lumbar interbody fusion for treatment of lumbosacral spondylolisthesis: A case series  

PubMed Central

Introduction Traditional surgical management of lumbosacral spondylolisthesis is technically challenging and is associated with significant complications. The advent of minimally invasive surgical techniques offers patients treatment alternatives with lower operative morbidity risk. The combination of percutaneous pedicle screw reduction and an axial presacral approach for lumbosacral discectomy and fusion offers an alternative procedure for the surgical management of low-grade lumbosacral spondylolisthesis. Case presentation Three patients who had L5-S1 grade 2 spondylolisthesis and who presented with axial pain and lumbar radiculopathy were treated with a minimally invasive surgical technique. The patients-a 51-year-old woman and two men (ages 46 and 50)-were Caucasian. Under fluoroscopic guidance, spondylolisthesis was reduced with a percutaneous pedicle screw system, resulting in interspace distraction. Then, an axial presacral approach with the AxiaLIF System (TranS1, Inc., Wilmington, NC, USA) was used to perform the discectomy and anterior fixation. Once the axial rod was engaged in the L5 vertebral body, further distraction of the spinal interspace was made possible by partially loosening the pedicle screw caps, advancing the AxiaLIF rod to its final position in the vertebrae, and retightening the screw caps. The operative time ranged from 173 to 323 minutes, and blood loss was minimal (50 mL). Indirect foraminal decompression and adequate fixation were achieved in all cases. All patients were ambulatory after surgery and reported relief from pain and resolution of radicular symptoms. No perioperative complications were reported, and patients were discharged in two to three days. Fusion was demonstrated radiographically in all patients at one-year follow-up. Conclusions Percutaneous pedicle screw reduction combined with axial presacral lumbar interbody fusion offers a promising and minimally invasive alternative for the management of lumbosacral spondylolisthesis.



The merit of sintered PDLLA/TCP composites in management of bone fracture internal fixation.  


Polyesters based on lactic acid have been reported in terms of safety and biodegradation in human beings for 2 decades. The greatest advantage of such material is its degradation conducted only by hydrolysis, whereby the ester backbones are supposed to be unchained in the aqueous condition. The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment. The goal of this study was aimed at developing a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles for orthopedic application. The TCP particles in a range of 30-60 wt% with 5 wt% increments were doped into the PDLLA matrix which was prepared by melting and hot pressing techniques for the reinforcement. The basic mechanical strength, biodegradable behavior, and biological response of the composites were investigated in the study. Various techniques such as pH meter, UV, Fourier-transform infrared, and x-ray diffractometer were used to examine and record the degradable process of the composites soaked in saline for 1-16 weeks. The rabbit femur condyle fracture fixation test was used to evaluate tissue compatibility and the effects of bone fracture fixation on the composites. Histological observation and x-ray photography were used for investigating assistance. The mechanical strength of the composites initially increased with TCP additions up to 50wt%, but thereafter they showed no significant difference (p < 0.05). The composite with 50 wt% TCP addition showed greater mechanical strength and had good agreement with cortical bone in terms of its elastic modulus of 30-40 GPa. The weight loss of the pure PDLLA soaked in the saline started at 4 weeks and reached 95% after 16 weeks. The composites compared with pure PDLLA, however, showed no apparent evidence of degradation after soaked for 12 weeks. The possible mechanisms for the delayed degradation of the composites in saline might have been solution penetration retardation by the ceramic particles and chemical bonds formed between the interface of the TCP particles and the PDLLA matrix. In the histological evaluation of the rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the newly generated bone without fibrous tissue around 8 weeks after implantation. The fractured bone was gradually healed and the composite firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling. The developed composite was thought to be an alternative material for orthopedic application in the future, especially for bone screws and bone plates. PMID:10027889

Lin, F H; Chen, T M; Lin, C P; Lee, C J



Tissue reaction to implant corrosion in 38 internal fixation devices.  


The corrosion characteristics, metallurgical properties, and clinical performance of 38 retrieved internal fixation devices were correlated with the tissue reaction to these devices. Metallurgical parameters included thin and heavy inclusion content, Rockwell hardness, and grain size. The excised fibrous tissue strip was directly overlying each plate at removal and sectioned between screw-hole sites. The material studied from the 38 plates consisted of 201 screw-hole junctions with associated tissue biopsy sites. Clinical histories were obtained on all 38 patients with hardware removal. The average age at the time of plate insertion was 35.6 years (range, 4 to 75 years). Insertion diagnoses included acute trauma (35 patients), joint dislocations (two patients), and fracture nonunion (one patient). The devices included seven upper extremity bone plates, 19 lower extremity bone plates, and 12 hip screw plates. The devices remained in situ an average of 20.4 months (range, 3 to 60 months). Routine asymptomatic removals were performed on 17 of the patients, while the remaining 21 patients were symptomatic at the time of removal. Included in the reasons for symptomatic removal were pain associated with the implant (eight patients), nonunion (four patients), bursae prominence (three patients), and implant breakage (two patients). Significant correlations were found between average tissue reaction scores and average crevice corrosion scores; a trend of increasing average tissue reaction scores with increasing average screw surface corrosion scores also was observed for the 38 devices, although this relationship was not significant. Average crevice corrosion scores and average screw surface corrosion scores were highly correlated for all removals, and for the asymptomatic and symptomatic removal groups. The metallurgical parameters of thin inclusion content and heavy inclusion content also were significantly correlated for all removals, as well as for symptomatic removals. Similarly, significant correlations were found between the individual tissue reaction scores and crevice corrosion scores from the 201 individual sites, again for all devices and for the asymptomatic and symptomatic removal groups. Tissue reaction scores and time in situ showed significant correlation, with tissue reaction decreasing over time. Crevice corrosion and screw surface corrosion scores were not significantly related to time in situ. The results of this study indicate that there is considerable tissue reaction to the corrosion products of this material.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3368412

Thomas, K A; Cook, S D; Harding, A F; Haddad, R J



Biology Nitrogen Fixation: Fundamentals  

Microsoft Academic Search

The enzyme responsible for N_2 fixation, nitrogenase, is only found in prokaryotes. It consists of two metalloproteins, both irreversibly destroyed by exposure to the O_2 of air. The MoFe-protein binds N_2 and the Fe-protein, after activation by MgATP, supplies electrons. H_2 is evolved during the reduction of N_2 to NH_3 and can become the sole reaction in the absence of

J. R. Postgate



Computer-assisted virtual technology in intracapsular condylar fracture with two resorbable long-screws.  


Our aim was to fix intracapsular condylar fractures (ICF) with two resorbable long screws using preoperative computer-assisted virtual technology. From February 2008 to July 2011, 19 patients with ICF were treated with two resorbable long screws. Preoperatively we took panoramic radiographs and spiral computed tomography (CT). Depending on their digital imaging and communications in medicine (DICOM) data, the dislocated condylar segments were restored using the SimPlant Pro™ software, version 11.04. The mean (SD) widths of the condylar head and neck from lateral to medial were 19.01 (1.28)mm and 13.84 (1.13)mm, respectively. In all patients, the mandibles and the ICF seen intraoperatively corresponded with the preoperative three-dimensional and virtual reposition. All patients were followed up for 6-46 months (mean 21). Occlusion and mouth opening had been restored completely in all but one patient, and absolute anatomical reduction was also achieved in most cases. Computer-assisted virtual technology plays an important part in the diagnosis of ICF, as well as in its preoperative design. Fixation with only two resorbable long screws is an effective and reliable method for fixing ICF. PMID:22546281

Wang, W H; Deng, J Y; Zhu, J; Li, M; Xia, B; Xu, B



Biomechanical Comparison of 2 Different Locking Plate Fixation Methods in Vancouver B1 Periprosthetic Femur Fractures  

PubMed Central

Locking plates are commonly used to treat fractures around a well-fixed femoral component. The optimal construct should provide sufficient fixation while minimizing soft-tissue dissection. The purpose of the current study was to determine whether plate length, working length, or bone mineral density affects survival of locking plate fixation for Vancouver type B1 periprosthetic hip fractures. A transverse osteotomy was created just distal to cemented femoral prostheses in 9 pairs of cadaveric femurs. Fractures were stabilized with long (20-hole) or short (12-hole) locking plates that were secured proximally with cables and screws and distally with screws only. Specimens were then cycled 10 000 times at 2500 N of axial force and 15 Nm of torque to simulate full weightbearing. A motion capture system was used to record fracture displacement during cycling. Failure occurred in 5 long and 3 short plates, with no significant differences found in the number of cycles to failure. For the specimens that survived, there were no significant differences found between long and short plates for displacement or rotation observed at the fracture site. A shorter working length was not associated with increased failure rate. Lower bone mineral density was significantly associated with failure (P = .02). We concluded that long locked plates do not appear to offer a biomechanical advantage over short locking plates in terms of fixation survival, and that bone mineral density was a better predictor of failure than was the fixation construct type.

Pletka, Joshua D.; Marsland, Daniel; Belkoff, Stephen M.; Mears, Simon C.; Kates, Stephen L.



Expandable intramedullary nails for fixation of tibial shaft fractures.  


Interlocking intramedullary nailing is currently the preferred treatment for most tibial fractures requiring operative treatment, with good results and a relatively low complication rate as reported in large clinical series. However, vascular and neurological complications caused by interlocking screws have been reported. In addition, insertion of distal interlocking screws can be technically demanding and may entail substantial exposure. We present the results with an expandable self-locking nail in the management of 52 AO type A and B tibial shaft fractures. The mean time to union was 15.8 weeks and the rate of union was 98%. The average surgical time was 60 minutes. Complications were those usually seen in diaphysis nailing and no complication was noted during nail expansion. Interlocking screws are not necessary, which reduces the risk of iatrogenic lesions. The expandable nail allows effective management of AO type A and B diaphyseal fractures of the tibia, a lower radiation exposure and shorter operative time. PMID:23409575

Ghafil, Dior; Ackerman, Pieter; Baillon, Renaud; Verdonk, Rene; Delince, Philippe



Numerical investigations of MRI RF field induced heating for external fixation devices  

PubMed Central

Background The magnetic resonance imaging (MRI) radio frequency (RF) field induced heating on external fixation devices can be very high in the vicinity of device screws. Such induced RF heating is related to device constructs, device placements, as well as the device insertion depth into human subjects. In this study, computational modeling is performed to determine factors associated with such induced heating. Methods Numerical modeling, based on the finite-difference time-domain (FDTD) method, is used to evaluate the temperature rises near external device screw tips inside the ASTM phantom for both 1.5-T and 3-T MRI systems. The modeling approach consists of 1) the development of RF coils for 1.5-T and 3-T, 2) the electromagnetic simulations of energy deposition near the screw tips of external fixation devices, and 3) the thermal simulations of temperature rises near the tips of these devices. Results It is found that changing insertion depth and screw spacing could largely affect the heating of these devices. In 1.5-T MRI system, smaller insertion depth and larger pin spacing will lead to higher temperature rise. However, for 3-T MRI system, the relation is not very clear when insertion depth is larger than 5?cm or when pin spacing became larger than 20?cm. The effect of connection bar material on device heating is also studied and the heating mechanism of the device is analysed. Conclusions Numerical simulation is used to study RF heating for external fixation devices in both 1.5-T and 3-T MRI coils. Typically, shallower insertion depth and larger pin spacing with conductive bar lead to higher RF heating. The heating mechanism is explained using induced current along the device and power decay inside ASTM phantom.



The in vivo performance of 250 internal fixation devices: a follow-up study.  


The in vivo performance of 250 retrieved internal fixation plates was evaluated. The corrosion characteristics and metallurgical properties of each implant were assessed and correlated with respective clinical performance. Screw-plate interface corrosion and screw surface corrosion were graded; Rockwell hardness, grain size, thin inclusion content, and heavy inclusion content measurements were made. The devices studied included 169 bone plates, 59 Richards type hip screw-plates and 22 Jewett type hip nail-plates. The devices remained in situ for an average of 26.3 months, with in situ periods ranging from 1 to 192 months. The majority of the plates (50.4%) were removed due to cause-related reasons, while the remaining devices (49.6%) were removed on a routine asymptomatic basis. The primary symptomatic removal reasons consisted of implant related pain, nonunion or malunion, infection, loosening and implant breakage. Upon stereomicroscopic examination, 89% of all plates exhibited some degree of interface crevice corrosion, and 88% of all screws exhibited some degree of surface corrosion. Statistical analysis of corrosion gradings and metallurgical data revealed significant correlations between the two. As was suggested in our previous study of a limited number of implants, this study demonstrates that stricter manufacturing standards for metallurgical properties would serve to enhance corrosion resistance and improve the in vivo performance of stainless steel internal fixation devices. It is also suggested that the routine removal of all internal fixation plates after fracture healing has been achieved would reduce the occurrence of symptomatic complications, such as implant breakage, implant loosening and implant related pain. PMID:3607150

Cook, S D; Thomas, K A; Harding, A F; Collins, C L; Haddad, R J; Milicic, M; Fischer, W L



Fixator-assisted nailing and consecutive lengthening over an intramedullary nail for the correction of tibial deformity.  


We report the results of using a combination of fixator-assisted nailing with lengthening over an intramedullary nail in patients with tibial deformity and shortening. Between 1997 and 2007, 13 tibiae in nine patients with a mean age of 25.4 years (17 to 34) were treated with a unilateral external fixator for acute correction of deformity, followed by lengthening over an intramedullary nail with a circular external fixator applied at the same operating session. At the end of the distraction period locking screws were inserted through the intramedullary nail and the external fixator was removed. The mean amount of lengthening was 5.9 cm (2 to 8). The mean time of external fixation was 90 days (38 to 265). The mean external fixation index was 15.8 days/cm (8.9 to 33.1) and the mean bone healing index was 38 days/cm (30 to 60). One patient developed an equinus deformity which responded to stretching and bracing. Another developed a drop foot due to a compartment syndrome, which was treated by fasciotomy. It recovered in three months. Two patients required bone grafting for poor callus formation. We conclude that the combination of fixator-assisted nailing with lengthening over an intramedullary nail can reduce the overall external fixation time and prevent fractures and deformity of the regenerated bone. PMID:20044694

Bilen, F E; Kocaoglu, M; Eralp, L; Balci, H I



External fixation of pediatric femoral fractures.  


Fifteen pediatric femoral fractures in 14 patients were treated with external fixation using the EBI Orthofix unilateral external fixator. The average patient age was 8.5 years (range, 3-13 years). There were 7 children with multiple injuries and 7 with isolated fractures. The average duration in the fixator was 63 days; average followup was 34 months. All 15 fractures healed without additional operative intervention. Average angulation at the fracture site was 4.4 degrees in the anteroposterior plane (range, 0 degrees-10 degrees) and 4.6 degrees in the lateral plane (range, 0 degrees-11 degrees). There were 5 pin tract infections, all of which resolved with systemic antibiotics. There was 1 case of refracture in a boy with muscular dystrophy. Ten patients had clinically equal leg lengths, 3 patients had < 1 cm of inequality, and 1 patient had a 1.5 cm discrepancy. External fixation is a well-proven technique for managing pediatric femoral fractures in the child with multiple injuries. It is also an effective means of treating isolated femoral fractures in the pediatric population. PMID:7671516

Davis, T J; Topping, R E; Blanco, J S



Comparison of Apical Axial Derotation between Adolescent Idiopathic and Neuromuscular Scoliosis with Pedicle Screw Instrumentation  

PubMed Central

Study Design A retrospective study. Purpose To compare outcomes of apical derotation with pedicle screws in idiopathic and neuromuscular scoliosis (NMS). Overview of Literature No information about apical derotation in NMS with pedicle screws is available. Methods We performed deformity correcting surgery using pedicle screw constructs on 12 adolescent idiopathic scoliosis (AIS) patients (mean age 14.1 years) and 16 NMS patients (mean age 16.5 years). Preoperative, postoperative, and final follow-up radiographs were analyzed for Cobb's angle and pelvic obliquity, while apical rotation was measured on CT scans using the Aaro-Dahlborn method. Results For AIS, the mean preoperative Cobb's angle, pelvic obliquity, and apical rotation values were 57.3°, 2.8°, and 20.4°, respectively, and postoperatively they were 16.8°, 1.1° and 14.7°, respectively, showing significant correction. For NMS, the mean preoperative Cobb's angle, pelvic obliquity, and apical rotation values were 75.6°, 13.7°, and 42.9°, respectively, and postoperatively they were 27.1°, 5.8°, and 34.1°, respectively, also showing significant correction. There were no significant differences between AIS and NMS patients Cobb's angle p=0.306, pelvic obliquity p=0.887 and apical derotation p=0.113°. There were no differences in curve severity in the three groups (AIS, NMS >80°and NMS <80°); or the correction of apical rotation (p=0.25), although less correction was achieved in the Cobb's angle in the >80 NMS group (p=0.04). Conclusions Apical axial derotation can be achieved with posterior only pedicle screw fixation in NMS without anterior release, with comparable results in idiopathic scoliosis.

Modi, Hitesh N; Srinivasalu, S; Mehta, Satyen; Yang, Jae-Hyuk



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



Forefoot applications of external fixation.  


The use of external fixation in foot and ankle surgery has steadily increased with the advent of devices geared toward the foot and ankle that have evolved over the past decade, as well as a greater understanding of the indications and advantages of external fixation. The application of external fixators in the forefoot may at first glance seem both limited and possibly overkill, but once the basics of external fixation and the types of devices available are understood the options for use become numerous. PMID:12613075

DeHeer, Patrick A



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



[Osteosynthesis of severe injuries of the thoracic and lumbar spine with internal fixation].  


From a posterior approach long Schanz screws are inserted through the pedicles into the bodies of the two vertebrae just adjacent to the lesion and connected by the threaded Fixateur-interne-rods. By tightening the nuts the Schanz screws are fixed in all directions. The advantages of the F.I.-system are: excellent reposition by the long lever-arm of the Schanz screws, immobilization of only two segments avoiding the iatrogenic loss of mobility and lumbar lordosis, stability against flexion forces better than with Harrington distraction rods, additional rotational stability. PMID:6503540

Dick, W



Definitive Bone Fixation and Reconstruction: Conversion from Temporary External Fixation to Internal Fixation Methods  

Microsoft Academic Search

\\u000a Temporary external fixation is frequently employed in the military combat theater of operations to temporize devastating extremity\\u000a injuries and facilitate transport of the wounded soldier. Multiple civilian and a few military studies have provided helpful\\u000a insight into the staged treatment of these injuries including conversion of temporary external fixation to definitive stabilization\\u000a with internal fixation. Diaphyseal fractures of the long

Craig S. Bartlett; Benjamin Geer; David L. Helfet


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



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



Removal of Slipped Capital Femoral Epiphysis Screws:A 10 year review  

Microsoft Academic Search

Attitudes to removal of metalwork in cases of slipped capital femoral epiphysis ({SCFE}) vary. In a survey of paediatric orthopaedic surgeons 33\\\\% of respondents always remove the metalwork after fusion of the physis in {SCFE}, and 43\\\\% felt that the decision to remove the metal would depend on additional factors.1 Whilst screw removal is favoured by many orthopaedic surgeons, a

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



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



Treatment of stress fracture of the olecranon in throwing athletes with internal fixation through a small incision  

PubMed Central

The present study is a report of retrospective case series of stress fracture of the olecranon. Six patients presented posterior elbow pain in throwing in baseball and softball, but fracture was not diagnosed in radiographs. We detected stress fracture of the olecranon using computed tomographic (CT) scan and treated the patient with internal fixation with a headless cannulated double threaded screw through a small skin incision. All patients returned to competitive level without elbow complaints after the operation. When throwing athletes present with unusual posterior elbow pain and no significant findings on radiographs, a CT scan examination should be performed. We recommend surgical treatment of internal fixation with a screw through a small skin incision, as a good option for stress fracture of the olecranon in order to allow early return to sports activity in competitive athletes.



Treatment of stress fracture of the olecranon in throwing athletes with internal fixation through a small incision.  


The present study is a report of retrospective case series of stress fracture of the olecranon. Six patients presented posterior elbow pain in throwing in baseball and softball, but fracture was not diagnosed in radiographs. We detected stress fracture of the olecranon using computed tomographic (CT) scan and treated the patient with internal fixation with a headless cannulated double threaded screw through a small skin incision. All patients returned to competitive level without elbow complaints after the operation.When throwing athletes present with unusual posterior elbow pain and no significant findings on radiographs, a CT scan examination should be performed. We recommend surgical treatment of internal fixation with a screw through a small skin incision, as a good option for stress fracture of the olecranon in order to allow early return to sports activity in competitive athletes. PMID:23241173

Fujioka, Hiroyuki; Tsunemi, Kenjiro; Takagi, Yohei; Tanaka, Juichi



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


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

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



Posterior Surgery for Adolescent Idiopathic Scoliosis With Pedicle Screws and Ultra-high Molecular Weight Polyethylene Tape: Achieving the Ideal Thoracic Kyphosis.  


STUDY DESIGN:: Prospective clinical case series. OBJECTIVES:: To describe our surgical procedure and results for posterior correction and fusion with a hybrid approach using pedicle screws, hooks, and ultra-high molecular weight polyethylene tape with direct vertebral rotation (DVR) (the PSTH-DVR procedure) for treatment of adolescent idiopathic scoliosis (AIS) with satisfactory correction in the coronal and sagittal planes. SUMMARY OF BACKGROUND DATA:: Introduction of segmental pedicle screws in posterior surgery for AIS has facilitated good correction and fusion. However, procedures using only pedicle screws have risks during screw insertion, higher costs, and decreased postoperative thoracic kyphosis. We have obtained good outcomes compared with segmental pedicle screw fixation in surgery for AIS using a relatively simple operative procedure (PSTH-DVR) that uses fewer pedicle screws. METHODS:: The subjects were 30 consecutive patients with AIS who underwent the PSTH-DVR procedure and were followed for a minimum of two years. Preoperative flexibility, preoperative and postoperative Cobb angles, correction rates, loss of correction, thoracic kyphotic angles (T5-T12), coronal balance, sagittal balance, and shoulder balance were measured on plain radiographs. Rib hump, operation time, estimated blood loss, spinal cord monitoring findings, complications, and scoliosis research society (SRS)-22 scores were also examined. RESULTS:: The mean preoperative curve of 58.0° (range 40°-96°) was corrected to a mean of 9.9° postoperatively, and the correction rate was 83.6%. Fusion was obtained in all patients without loss of correction. In ten cases with preoperative kyphosis angles (T5-T12) <10°, the preoperative mean of 5.8° improved to 20.2° at the final follow-up. Rib hump and coronal, sagittal and shoulder balances were also improved, and good SRS-22 scores were achieved at final follow-up. CONCLUSION:: The correction of deformity with PSTH-DVR is equivalent to that of all-pedicle screw constructs. The procedure gives favorable correction, is advantageous for kyphosis compared with segmental screw fixation, and uses the minimum number of pedicle screws. Therefore, the PSTH-DVR procedure may be useful for treatment of idiopathic scoliosis. PMID:22907066

Imagama, Shiro; Ito, Zenya; Wakao, Norimitsu; Ando, Kei; Hirano, Kenichi; Tauchi, Ryoji; Muramoto, Akio; Matsui, Hiroki; Matsumoto, Tomohiro; Sakai, Yoshihito; Katayama, Yoshito; Matsuyama, Yukihiro; Ishiguro, Naoki



Pedicle Screw Instrumentation for Adolescent Idiopathic Scoliosis: The Insertion Technique, the Fusion Levels and Direct Vertebral Rotation  

PubMed Central

The pedicle is a power nucleus of the vertebra and offers a secure grip of all 3 columns. Pedicle screw instrumentation has advantages of rigid fixation with improved three-dimensional (3D) correction and it is accepted as a reliable method with a high margin of safety. Accurate placement of the pedicle screws is important to reduce possible irreversible complications. Many methods of screw insertion have been reported. The author has been using the K-wire method coupled with the intraoperative single posteroanterior and lateral radiographs, which is the most safe, accurate and fast method. Identification of the curve patterns and determining the fusion levels are very important. The ideal classification of adolescent idiopathic scoliosis should address the all patterns, predict the extent of accurate fusion and have good inter/intraobserver reliability. My classification system matches with the ideal classification system, and it is simple and easy to learn; and my classification system has only 4 structural curve patterns and each curve has 2 types. Scoliosis is a 3D deformity; the coronal and sagittal curves can be corrected with rod rotation, and rotational deformity has to be corrected with direct vertebral rotation (DVR). Rod derotation and DVR are true methods of 3D deformity correction with shorter fusion and improved correction of both the fused and unfused curves, and this is accomplished using pedicle screw fixation. The direction of DVR is very important and it should be opposite to the direction of the rotational deformity of the vertebra. A rigid rod has to be used to prevent rod bend-out during the derotation and DVR.




Technology Transfer Automated Retrieval System (TEKTRAN)

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


Delayed Presentation of Lateral Femoral Circumflex Artery Injury Post Cannulated Hip Screw Surgery -A Case Report  

PubMed Central

An elderly patient underwent cannulated hip screw surgery for a subcapital neck of femur fracture.Nine days post surgery, she was noted to have collapsed with a falling haemoglobin level. Computed tomography revealed a large haematoma to the thigh. Further angiography showed active bleeding from one of the branches of the lateral femoral circumflex artery (LFCA),which we postulate was caused by the sharp tip of a version guidewire used during fracture fixation surgery. Iatrogenic injury during hip fracture fixation is a rare event,particularly to the circumflex branches of the profunda femoris artery (PFA), and may occur from hard wire use intraoperatively or from the fracture itself. The LFCA branches laterally from the PFA, runs anterior to the femoral neck,where we suspect it was injured in our case.Whilst a version wire is a useful radiological guide intra-operatively,manually clearing a passage for its insertion into the femoral head/neck junction and using the blunt end is recommended. A combination of acute swelling in the operated region and falling haemoglobin post surgery should alert the clinician to possible vascular injury.Compared to duplex ultrasonography,CT angiography remains the gold standard in its specificity and sensitivity for diagnosing arterial injuries.With early recognition and prompt radiological intervention, this rare complication of fracture fixation surgery can be treated without the need for further surgery.

Davda, Kinner; Pollard, Thomas CB; Graham, Alastair J



Permanent cardiac pacing with electrodes of a new type of fixation in the endocardium.  


To improve electrode construction the following main problems have been considered: (1) reliable initial fixing in the endocardium, and (2) reducing the area of contact surface and improving threshold values. In this article we have described three original electrodes: 1) an endocardial electrode with a multi-edged tip (contact area 28 mm2), which gives high electric field strength and low thresholds; 2) a spreading tip electrode, which was created on the basis of morphological data. The tissues grow into the spread spaces of this tip and ensure better stability (contact area 17.8 mm2); and 3) a double-screw-in electrode which differs from the other corkscrew types. The contact end (surface area--10.4 mm2) consists of two sickle-shaped hooks. The sickle handle is 0.7 mm in length which prevents further hook penetration in the wall of the heart. It was found that a multi-edged electrode and electrodes supplied with a fixation device are, in terms of energy consumption, more effective compared to electrodes with spherical or cylindrical tips of the same area of contact surface. The double-screw-in endocardial electrode has useful features: reliable fixation and a small contact surface area and, therefore, a low threshold value. Thirty-five double-screw-in electrodes were inserted into an atrial position and 28 into a ventricular position. We have not observed any displacement of such electrodes during the past two years. PMID:83617

Bredikis, J; Dumcius, A; Stirbys, P; Muckus, K; Veteikis, R; Koroliov, V; Yarmilko, P



Understanding Nitrogen Fixation  

SciTech Connect

The purpose of our program is to explore fundamental chemistry relevant to the discovery of energy efficient methods for the conversion of atmospheric nitrogen (N{sub 2}) into more value-added nitrogen-containing organic molecules. Such transformations are key for domestic energy security and the reduction of fossil fuel dependencies. With DOE support, we have synthesized families of zirconium and hafnium dinitrogen complexes with elongated and activated N-N bonds that exhibit rich N{sub 2} functionalization chemistry. Having elucidated new methods for N-H bond formation from dihydrogen, C-H bonds and Broensted acids, we have since turned our attention to N-C bond construction. These reactions are particularly important for the synthesis of amines, heterocycles and hydrazines with a range of applications in the fine and commodity chemicals industries and as fuels. One recent highlight was the discovery of a new N{sub 2} cleavage reaction upon addition of carbon monoxide which resulted in the synthesis of an important fertilizer, oxamide, from the diatomics with the two strongest bonds in chemistry. Nitrogen-carbon bonds form the backbone of many important organic molecules, especially those used in the fertilizer and pharamaceutical industries. During the past year, we have continued our work in the synthesis of hydrazines of various substitution patterns, many of which are important precursors for heterocycles. In most instances, the direct functionalization of N{sub 2} offers a more efficient synthetic route than traditional organic methods. In addition, we have also discovered a unique CO-induced N{sub 2} bond cleavage reaction that simultaneously cleaves the N-N bond of the metal dinitrogen compound and assembles new C-C bond and two new N-C bonds. Treatment of the CO-functionalized core with weak Broensted acids liberated oxamide, H{sub 2}NC(O)C(O)NH{sub 2}, an important slow release fertilizer that is of interest to replace urea in many applications. The synthesis of ammonia, NH{sub 3}, from its elements, H{sub 2} and N{sub 2}, via the venerable Haber-Bosch process is one of the most significant technological achievements of the past century. Our research program seeks to discover new transition metal reagents and catalysts to disrupt the strong N {triple_bond} N bond in N{sub 2} and create new, fundamental chemical linkages for the construction of molecules with application as fuels, fertilizers and fine chemicals. With DOE support, our group has discovered a mild method for ammonia synthesis in solution as well as new methods for the construction of nitrogen-carbon bonds directly from N{sub 2}. Ideally these achievements will evolve into more efficient nitrogen fixation schemes that circumvent the high energy demands of industrial ammonia synthesis. Industrially, atmospheric nitrogen enters the synthetic cycle by the well-established Haber-Bosch process whereby N{sub 2} is hydrogenated to ammonia at high temperature and pressure. The commercialization of this reaction represents one of the greatest technological achievements of the 20th century as Haber-Bosch ammonia is responsible for supporting approximately 50% of the world's population and serves as the source of half of the nitrogen in the human body. The extreme reaction conditions required for an economical process have significant energy consequences, consuming 1% of the world's energy supply mostly in the form of pollution-intensive coal. Moreover, industrial H{sub 2} synthesis via the water gas shift reaction and the steam reforming of methane is fossil fuel intensive and produces CO{sub 2} as a byproduct. New synthetic methods that promote this thermodynamically favored transformation ({Delta}G{sup o} = -4.1 kcal/mol) under milder conditions or completely obviate it are therefore desirable. Most nitrogen-containing organic molecules are derived from ammonia (and hence rely on the Haber-Bosch and H{sub 2} synthesis processes) and direct synthesis from atmospheric nitrogen could, in principle, be more energy-efficient. This is particularly attractive giv

Paul J. Chirik



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



Proximal humeral fractures: internal fixation.  


Fractures of the proximal humerus are common injuries that are increasing in incidence as the population ages. These fractures are often treated nonsurgically; however, surgery is indicated if displacement, concurrent dislocation, or unacceptable alignment is present. Knowledge of the anatomic and physiologic characteristics of the proximal humerus and shoulder joint and familiarity with the available fixation elements will help surgeons make informed and patient-specific decisions regarding treatment. Reduction and internal fixation of proximal humeral fractures has expanding indications in comparison with arthroplasty, in part because of improvements in fixation technology and a better understanding of anatomy and physiology. The outcomes of proximal humeral fractures managed with percutaneous pinning, open reduction and locked-plate fixation, and intramedullary fixation are being actively investigated. PMID:23395021

Aaron, Daniel; Shatsky, Joshua; Paredes, Juan Carlos S; Jiang, Chunyan; Parsons, Bradford O; Flatow, Evan L



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.



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

PubMed Central

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

Akel, Ibrahim; Demirkiran, Halil Gokhan



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


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

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



Fixation disparity in binocular stress.  


Fixation disparity has been taken as a sign of stress on binocular vision because it is established that prism stress creates fixation disparity. This paper looks at the effect on fixation disparity of the stress caused by requiring subjects to read in inadequate illumination. It is found that the reduction in illumination does not in itself immediately change the magnitude of the fixation disparity. There is, however, an increase in the mean slope of the central part of the fixation disparity curve which suggests that when the effect of reduced illumination is added to prism stress, fixation disparity is increased. The stress created by asking subjects to read in reduced illumination for half an hour resulted in the mean associated heterophoria being