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Introduction: Percutaneous screws placed into the posterosuperior femoral neck are frequently extraosseous or "in-out-in" (IOI). These IOI screws are not readily identifiable on anteroposterior (AP) and lateral fluoroscopic images. The purpose of this study was to examine the ability of surgeons to identify IOI guide pins using sequential fluoroscopic rollover images., Materials and Methods: A 3.2-mm guide pin was placed into the posterosuperior quadrant of eleven synthetic femur models. Five samples were "all-in" (AI), and six were IOI. Sequential fluoroscopic rollover images were obtained starting with an AP image, then images at 10-degree rollover intervals ending with a direct lateral image. Images were reviewed in a blinded fashion by five attending orthopedic trauma surgeons and 20 resident surgeons to determine whether guide pins were AI or IOI. Accuracy, interobserver reliability, sensitivity, and specificity were assessed., Results: The overall accuracy of responses was 86% with no difference between attending trauma surgeons and residents (p = 0.5). The sensitivity and specificity for an IOI guide pin were 98.0% and 71.2%, respectively. Interobserver reliability among surgeons was good (κ = 0.703)., Conclusion: The use of the sequential fluoroscopic rollover images after placement of the posterosuperior guide pin into the femoral neck was highly sensitive for detecting an IOI position. The 40-degree rollover image was the best view to evaluate the proximity of the guide pin to the posterior cortex.

Background: There has been a paucity of cohort trials directly comparing multiple cannulated screws (MCS) and sliding hip screws (SHS) in femoral neck fractures at any level. Thus, a well-conducted clinical trial with an adequate sample size is urgently needed. We undertake a retrospective study to compare outcomes in patients who undertake MCS or SHS fixation for femoral neck fractures., Methods: A retrospective review of femoral neck fractures performed with SHS or MCS between February 2016 and June 2018 was conducted with Institutional Review Board approval in the First Affiliated Hospital of Dali University of Orthopedic Trauma. All cases were performed by a single surgeon. Of these, we included 180 patients (90 hips) that were performed surgery in treatment of femoral neck fractures. All patients received the same standardized postoperative multimodal pain protocol and the same postoperative rehabilitation program. The primary endpoint was Harris Hip Score. Secondary outcome measures include operation time, length of hospital stay, incision length, patient satisfaction, and postoperative complications. Multivariate linear and regression analyses was used to identify independent predictors of outcome. A P-value of <.05 was defined as statistical significance., Results: We hypothesize that both treatments provide comparable outcomes., Trial Registration: This study protocol was registered in Research Registry (researchregistry5638).

The aim of this study is to assess if there is a difference in outcomes between a dynamic hip screw with or without an anti-rotation screw in the treatment of hip fractures. All patients with an intracapsular hip fracture who underwent dynamic hip screw osteosynthesis between January 2010 and December 2013 in three Dutch hospitals were reviewed. Minimal follow-up was one year. The study included a total of 364 patients. 24 patients were lost to follow-up and excluded. 297 (87.4%) were in the dynamic hip screw group and 43 (12.6%) in the dynamic hip with anti-rotation screw group. Direct comparison of patient characteristics of the two groups showed significant differences in age, sex, Garden classification and Pauwels classification. Patients operated with a dynamic hip screw and anti-rotation screw are significantly younger and their fractures are significantly more dislocated and steeper. To draw conclusions about differences in outcome, a randomised clinical trial should be performed.

Objective: To compare the clinical and radiographic outcomes of bioabsorbable screw and metallic screw for Maisonneuve fracture., Methods: The clinical data of 68 patients of Maisonneuve fracture treated with open reduction and internal fixation between October 2012 and October 2016 were retrospectively analyzed. Metallic screw fixation was used in 37 cases (group A) and absorbable screw fixation was used in 31 cases (group B). There was no significant difference in age, gender, weight, operated side, cause of injury, time from injury to operation, and complications between the two groups ( P >0.05). At last follow-up, the tibiafibular clear space (TFCS), tibiafibular overlap (TFO), medial clear space (MCS), and syndesmotic malreduction rate were recorded. And the dorsiflexion and plantar-flexion range of motion, pain visual analogue scale (VAS) score, ankle and hind foot score of American Orthopaedic Foot and Ankle Society (AOFAS), and Olerud-Molander (OM) score were recorded., Results: All patients were followed up 25-43 months, with an average of 32.3 months. There was no significant difference in the operation time between the two groups ( t =1.229, P =0.282). All the fractures healed, and there was no significant difference in fracture healing time between the two groups ( t =1.367, P =0.413). At last follow-up, the syndesmotic malreduction rate of group A was 16.2% (6/37), showing no significant difference when compared with group B [6.2% (2/31)] ( χ 2 =1.549, P =0.213). There were 3 complications in group A, 1 was superficial wound infection, 1 was local heterotopic ossification due to failure to remove the screws in time, 1 was local heterotopic ossification of the screws; and there were 2 complications in group B, 1 was rejection and 1 was local heterotopic ossification of the screws. There was no significant difference in the incidence of complications between the two groups ( χ 2 =0.068, P =0.794). There was no significant difference in TFCS, MCS, TFO, ankle dorsiflexion and plantar-flexion range of motion, AOFAS score, OM score, and VAS score between the two groups at last follow-up ( P >0.05)., Conclusion: Compared with metallic screw, absorbable screws provide adequate fixation and functional recovery with avoiding screw removal and lower syndesmotic malreduction.

Objectives: This study aims to compare the results of internal fixation with dynamic hip screw (DHS)/antirotation screw and conventional cannulated screw (CS) for femoral neck fracture., Patients and Methods: This retrospective study included a total of 78 patients (57 males, 21 females) with collum femoris fractures treated with internal fixation between January 2015 and January 2019. Group 1 comprised 41 patients with a mean age of 45.7 years (range, 19 to 62 years) treated with DHSs/antirotation screws, while group 2 comprised 37 patients with a mean age of 41.9 years (range, 17 to 75 years) treated with CSs. The patients were evaluated for union, avascular necrosis (AVN), femoral neck shortness, operation time, duration of fluoroscopy exposure, and functional outcomes., Results: Age, gender, and Garden classification stages were similar in both groups. No significant difference was found between the groups in respect of AVN and non-union rates. The non-union rate was 12.2% in group 1 and 21.6% in group 2 (p>0.05). The duration of fluoroscopy exposure was statistically significantly higher in group 2 (p=0.001) and the operation time was statistically significantly longer in group 1 (p=0.001). In group 2, femoral neck shortness stature was significantly higher (p=0.007). At the final follow-up examination, the Harris hip score was statistically significantly higher in group 1 (p=0.04)., Conclusion: Dynamic hip screw/antirotation screw was a more relevant treatment method for transcervical femoral neck fractures compared to CS with more favorable functional outcomes and less fluoroscopy exposure.

Objective:  The aim of this study was to to determine the comparative stiffness following repair of an axial sagittal fracture model in equine distal sesamoid bones using either a single 3.5-mm or 4.5-mm cortical bone screw placed in lag fashion., Study Design:  The present study was an in vitro biomechanical study., Results:  The mean (±standard deviation) stiffness value for the 4.5-mm screw-bone construct (522.49 N/mm ± 168.21) was significantly greater than the 3.5-mm screw-bone construct (408.46 N/mm ± 131.13) ( p  = 0.047). This represents a 28% difference in mean stiffness., Conclusions:   In vitro , the 4.5-mm screw-bone construct creates a stiffer repair of fractured distal sesamoid bones by a margin of 28%. The 4.5-mm cortical bone screw may better withstand forces imparted on the distal sesamoid bone sustained during anaesthetic recovery, normal weight bearing and athletic exercise, thereby minimizing the risk of implant failure., Competing Interests: All authors have no conflicts of interest to disclose., (Georg Thieme Verlag KG Stuttgart · New York.)

Objective: To determine whether 2.0 mm cancellous screws are superior to 2.0 mm cortical screws when inserted into cancellous and bicortical bone., Study Design: Biomechanical study., Methods: The 2.0 mm cancellous screws and 2.0 mm cortical screws were inserted according to the recommended guidelines in synthetic cancellous and bicortical blocks. Fifteen screw-block constructs per group were tested to failure in axial pullout. Axial pullout strength and yield strength were calculated. Data were analyzed using a one-way ANOVA., Results: The 2.0 mm cortical screws achieved lower axial pullout strength than 2.0 mm cancellous screws in cancellous blocks. The 2.0 mm cortical screws achieved greater pullout strength than 2.0 mm cancellous screws in bicortical blocks., Conclusion: The 2.0 mm cancellous screws may offer a biomechanical advantage in bone with thin cortices (<1 mm thick), whereas 2.0 mm cortical screws may be preferred in cortical bone with cortices measuring at least 1 mm in thickness., (© 2017 The American College of Veterinary Surgeons.)

Background: Proximal femoral fracture rates are increasing due to osteoporosis and traffic accidents. Proximal femoral nails are routinely used in the treatment of these fractures in the proximal femur., Aims: To compare various combinations and to determine the ideal proximal lag screw position in pertrochanteric fractures (Arbeitsgemeinschaft für Osteosynthesefragen classification 31-A1) of the femur by using optimized finite element analysis., Study Design: Biomechanical study., Methods: Computed tomography images of patients' right femurs were processed with Mimics. Afterwards a solid femur model was created with SolidWorks 2015 and transferred to ANSYS Workbench 16.0 for response surface optimization analysis which was carried out according to anterior-posterior (-10°0) and posterior-anterior directions of the femur neck significantly increased these stresses. The most suitable position of the proximal lag screw was confirmed as the middle of the femoral neck by using optimized finite element analysis.

Purpose: Inter-fragmentary rotational and axial instabilities are major challenges in nailing of complex or comminuted fractures. We aimed to compare the inter-fragmentary rotational and axial stability of novel anti-rotation interlocking nail and the conventional interlocking nail in complex or comminuted femur shaft fractures., Methods: Twenty composite femurs were divided into two groups, 30 mm was resected from the mid-portion of all composite femurs. The inter-fragmentary rotational and axial stabilities were assessed., Results: Between 10-N m external and 6-N m internal rotation torques, mean maximum inter-fragmentary rotational arc motion in the novel nails was 1.63 mm and 291 % less than that of the conventional nails (6.38 mm, P = 0.000). Between 150 N distraction and 2300 N compression, mean axial motion in the novel nails was 0.8 mm and 257 % less than that of the conventional nails (2.86 mm, p = 0.000)., Conclusion: An anti-rotational novel nail is superior to the conventional interlocking nail in terms of maximum inter-fragmentary rotational and axial stabilities in complex and comminuted femur shaft fractures.

Objectives: To compare the rate of cutout of helical blades and lag screws in low-energy peritrochanteric femur fractures treated with a cephalomedullary nail (CMN)., Design: Retrospective review., Setting: Academic medical center., Patients: Overall, this study included 362 patients with an average age of 83 year old, a majority of whom were women, and had sustained a low-energy peritrochanteric femur fracture treated with a CMN. All patients had at least 3 months of clinical and radiographic follow, with an average follow-up of 11 months and a range of 3-88 months follow-up., Intervention: Cephalomedullary nailing with the use of a helical blade or single lag screw for proximal fixation., Main Outcome Measurements: Cutout of the helical blade or lag screw., Results: Twenty-two cutouts occurred, 14 (15.1%) of 93 patients with helical blades and 8 (3.0%) of 269 patients with lag screws. Cutout with the helical blade was significantly more frequent than with the lag screw (P = 0.0001). The average tip-apex distance (TAD) was significantly greater for those patients who experienced cutout both for the helical blades (23.5 vs. 19.7 mm; P = 0.0194) and lag screws (24.5 vs. 20.0 mm; P = 0.0197). An absolute TAD predictive of cutout could not be determined., Conclusions: When the helical blade was used, implant cutout occurred at a significantly higher rate compared with lag screw fixation. There was not a threshold TAD that was predictive of cutout for either implant., Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Objectives: To evaluate the biomechanical performance of femoral neck system (FNS) in comparison with established methods for fixation of femoral neck fractures in a cadaveric model., Methods: Twenty pairs of fresh-frozen human cadaveric femora were instrumented either with dynamic hip screw and antirotation screw (DHS-screw), DHS-blade, 3 cannulated screws (3CS) or with FNS in a partially paired design. The specimens were randomized to 2 paired treatment groups based on the bone mineral density (BMD), namely DHS-screw/DHS-blade and FNS/3CS. A reduced unstable femoral neck fracture with postero-caudal comminution, OTA/AO 31-B2.3, 70 degrees Pauwels III, was simulated by cutting 30 degrees distal and 15 degrees posterior wedges. Cyclic axial loading was applied in 16 degrees adduction, starting at 500 N and with progressive peak force increase of 0.1 N/cycle until construct failure. Axial stiffness was measured in the third loading cycle. Femoral neck and leg shortening, and varus tilting and implant migration were calculated by means of optical motion tracking., Results: Mean axial stiffness was 688.8 ± 132.6 N/mm for DHS-screw, 629.1 ± 94.1 N/mm for DHS-blade, 748.9 ± 211.4 N/mm for FNS, and 584.1 ± 156.6 N/mm for 3CS, with no statistical significances. Cycles until 15-mm leg shortening were comparable for DHS-Screw (20,542 ± 7465), DHS-blade (19,161 ± 3793) and FNS (17,372 ± 2996), however significantly higher than for 3CS (7293 ± 2819), P < 0.001. Similarly, cycles until 15 mm femoral neck shortening were comparable between DHS-screw (20,846 ± 7339), DHS-blade (18,974 ± 4032) and FNS (18,171 ± 2585), and significantly higher than 3CS (8039 ± 2778), P < 0.001., Conclusions: From a biomechanical point of view, the femoral neck system is a valid alternative to treat unstable femoral neck fractures, representing the advantages of a minimally invasive implant with comparable stability to the 2 DHS systems and superior to cannulated screws.

Background: Goal of this study is to present an easily reproducible and reliable measurement to evaluate accuracy of screw placement in cervical spine., Methods: Accuracy of cervical screw position was assessed in 52 patients treated with 163 screws. Each patient receiving pedicle, transarticular C1/2, lateral mass, or laminar screws and postoperative CT scan was included. Placement position was categorized in 5 grades: Grade 1 is ideal with pedicle wall perforation < 1 mm, grade 2 < 2 mm, grade 3 < 3 mm, and grade 4 < 4 mm. Grade 5 > 4 mm and/or obstruction of transverse foramen by more than half a screw diameter. Intraclass correlation coefficient (ICC) values were assessed for inter- and intraobserver reliability., Results: The mode of individual evaluations was calculated to assign a single value to each screw. This yielded 89 grade 1 (54.6%), 48 grade 2 (29.4%), 14 grade 3 (8.6%), 3 grade 4 (1.8%), and 9 grade 5 (5.5%) screws. Intraobserver reliability ICC was 0.966 and 0.959 for measurements. Interobserver reliability ICC was 0.938., Conclusion: This study introduces a reliable classification of cervical spine instrumentation with various screw types. This should enable the use of a uniform and reproducible, and thus comparable classification for screw position in cervical spine.

Objectives: To identify discrete construct characteristics related to overall construct rigidity that may be independent predictors of nonunion after lateral locked plate (LLP) fixation of distal femur fractures., Design: Retrospective case-control study., Setting: Three level-1 urban trauma centers., Patients/participants: Two hundred and seventy-one supracondylar femoral fractures treated with LLP at 3 affiliated level 1 urban trauma centers between August 2004 and December 2010., Methods: Nonunion was defined as a secondary procedure for poor healing. Construct variables included: (1) combined plate design and material variable, (2) Plate length, (3) # screws proximal to fracture, (4) total screw density (TSD), (5) proximal screw density (PSD), (6) presence of a screw crossing the main fracture, and (7) rigidity score multivariable analysis was performed using logistic regression to identify independent risk factors for nonunion., Intervention: LLP fixation., Main Outcome Measure: Nonunion., Results: Nonunion rate was 13.3% (n = 36). There was a significant association between plate design/material and nonunion with 41% of stainless constructs and 10% of titanium constructs resulting in a nonunion (P < 0.001). Rigidity scores reached significance (P = 0.001) with constructs resulting in a nonunion having higher scores. No significant univariate differences with respect to number of proximal screws, plate length, total screw density, or proximal screw density were observed between healed fractures and those with nonunion. Results of the multivariate analysis confirmed that the primary significant independent predictor of nonunion was plate design/material (odds ratio, 6.8; 95% CI, 2.9-16.1; P < 0.001)., Conclusions: When treating distal femur fractures with LLP, combined plate design and material variable has a highly significant influence on the risk of nonunion independent of any other construct variable., Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Study Design: Retrospective clinical cohort study., Objective: To compare the clinical and radiographic outcomes of patients who were treated with intrasegmental pars fixation by either laminar compression screw (LS) or a pedicle screw, rod, and laminar hook (PSRH) construct., Summary of Background Data: Spondylolysis is a nonunion defect of the pars interarticularis. In symptomatic spondylolysis, direct repair of the pars interarticularis defect can preserve motion and prevent abnormal stresses at the adjacent levels., Methods: Sixteen patients who failed nonoperative treatment and underwent direct pars repair by using LS (n=9) or PSRH (n=7) constructs were included in the study. Clinical outcome was assessed by using the MacNab criteria. Radiologic fusion and complications were evaluated using plain radiographs or computed tomography images and patient charts., Results: The healing rate was 100% after 6 months. The healing time was similar in both the groups: LS, 6.5 months; PSRH, 6.2 months. Patients with PSRH (5.9 mo) were more likely to return to sports earlier relative to patients with LS (7.7 mo). There were no complications in the LS group; in the PSRH group, 1 patient had mild sensory deficit and 2 had superficial wound infections. The MacNab criteria for pain assessment showed an excellent or good outcome in 8 of 9 patients in LS group and 6 of 7 patients in PSRH group. Relative to LS patients, there was a significant increase in surgical time and estimated blood loss among PSRH patients., Conclusions: Either of the mentioned 2 techniques appears to produce acceptable results. Biplanar fluoroscopy and navigation systems could minimize the risk of screw misplacement with LS construct. Familiarity with the various fixation techniques will allow the surgeon to select the most appropriate surgical technique.

The contour of the ilium is curved and the iliac fossa is thin, making adequate fixation for fractures involving the iliac wing challenging to achieve at times. The purpose of this article is to describe a previously unreported technique for enhancing fixation in iliac fractures using simple cortical screws.

A plethora of screw designs and sizes are available from multiple companies for use in upper extremity surgery. Knowing the dimensions of screws is critical in the treatment of bone of varying dimensions for fractures, osteotomies, or arthrodeses. Although many screws are named by their major thread diameter, this is not always true. Because of this confusing nomenclature and vast number of options, we sought to review the most commonly used screws and codify their dimensions into a readily available article and reference chart. This article highlights the basic dimensions of commonly used headless screws, stand-alone lag screws, non-locking and locking screws for plating, and biocomposite screws. Commonly described treatments using these screws include fixation of elbow, wrist, carpal, metacarpal, and phalangeal fractures and osteotomies, as well as arthrodeses of upper extremity joints. This article and its tables are by no means exhaustive of all commercially available implants. The focus is on the most commonly used implants in the United States as of 2014., (Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Objective: Posterior-to-anterior directed screws are stronger than anterior-to-posterior directed screws for coronoid fracture fixation. Anterior approaches that facilitate direct reduction and fixation of coronoid fractures have been described. The present study was based on the hypothesis that anterior-to-posterior headless screw (Acutrak Mini® 3.5 mm × 26 mm, Acumed, Hillsboro, Oregon, USA) fixation of coronoid fractures would be as strong as posterior-to-anterior 2.7 mm Association for Osteosynthesis (AO) cortical screw fixation., Methods: This study included 14 ulnas obtained from 14 formalin-preserved adult cadavers. Coronoid type 2 fractures were created and fixed randomly using anterior-to-posterior headless screws (antegrade group) and posterior-to-anterior 2.7 mm AO cortical screws (retrograde group). The experimental constructs were loaded until 2 mm of displacement. Failure load (N), fixation stiffness (Nmm-1), and indentation stiffness were calculated., Results: Failure load was higher in the retrograde screw group (p=0.03), whereas loading stiffness values of the fixation devices and bones did not differ between the 2 fixation groups (p>0.05)., Conclusion: The present study failed to show that anterior-to-posterior directed headless screw fixation of coronoid fractures could adequately replace posterior-to-anterior placed screw fixation.

Objective: The aim of this study was to compare the biomechanical properties of minimal invasive sliding antirotator compressive hip screw (MIS-A-CHS), and multiple cannulated screws (CS) on a Pauwels type 3 femoral neck fracture model., Methods: A Pauwels type 3 vertical femoral neck fractures was created on 12 third-generation proximal femur models which were divided into two equal groups. The fracture was fixed with three CS in the first group, and MIS-A-CHS in the second group. The axial and rotational stiffness and maximum compression effect were compared between the groups., Results: The axial and rotational stiffness and maximum compression were significantly higher in MIS-A-CHS group (912.5 N, 540 N and 10.2 N/m, respectively) than the CS group (627.5 N, 380 N, and 3.9 N/m, respectively)., Conclusion: MIS-A-CHS appears to be a more secure fixation method in Pauwels type 3 femoral neck fractures than the CS.

Cervicocephalic screw medialization is a rare complication after intertrochanteric fracture synthesis with a Gamma3-type intramedullary nail. Only 6 cases of intrapelvic penetration by Gamma3 lag screw have been described. We now describe 2 additional cases and a review of the literature.

In recent times, the use of miniscrew implants to obtain absolute anchorage has gained momentum in clinical orthodontics as rigid anchorage modality. Miniscrew implants offers many advantages when used as temporary anchorage devices like, easy placement and removal, immediate loading, can be used in a variety of locations, provide absolute anchorage, economic and requires less patient cooperation. This makes them as a necessary treatment option in cases with critical anchorage that would have otherwise resulted in anchorage loss if treated with conventional means of anchorage. The aim of this comprehensive review is to highlight the gradual evolution, clinical use, advantages and disadvantages of the miniscrew implants when used to obtain a temporary but absolute skeletal anchorage for orthodontic applications.

Purpose: Hip perforation is a major complication in proximal femoral nailing. For biaxial nails, knowledge of their biomechanics is limited. Besides re-evaluation of accepted risk factors like the tip-apex distance (TAD), we analysed the influence of anti-rotational pin length., Methods: We compared 22 hip perforation cases to 50 randomly chosen controls. TAD, lag-screw position, angle between lag-screw and femoral neck axis, lag-screw gliding capacity, displacement and anti-rotational pin length were investigated., Results: Hip perforation was associated with a higher angle of deviation between lag-screw and femoral neck axis (p = 0.001), a lower telescoping capacity of the lag screw (p = 0.02), and higher TAD (p = 0.048). If the anti-rotational pin exceeded a line connecting the tip of the nail and the lag screw (NS line), hip perforation incidence was increased (p = 0.009). Inadequate pin length resulted in an odds ratio of 10.8 for hip perforation (p = 0.001)., Conclusions: In biaxial nails anti-rotational element positioning is underestimated, however, crucial.

Study Design: Evaluation using 3-dimensional screw trajectory software and computed tomographic scans., Objective: To investigate the anatomic feasibility of laminar screw placement in the upper thoracic spine compared with pedicle screw placement., Summary of Background Data: Although laminar screws have been suggested as an alternative to pedicle screws in the upper thoracic spine, previous anatomic feasibility studies have some limitations., Methods: Four types of screws were simulated from T1 to T6: unilaminar screw (US), superior bilaminar screw (SBS), inferior bilaminar screw (IBS), and pedicle screw (PS). Maximum allowable screw dimensions and the success rates of 4.5-mm screw placement were compared for each level. Laminar screw dimensions with more than 90% success rate at each level were determined for reference., Results: Computed tomographic scans of 132 patients were analyzed. Laminar screw diameters gradually increased from T1 (4.4-5.4 mm, for each type) to T6 (4.8-6.7 mm), whereas PS diameter steeply declined from T1 (5.9 mm) to T4 (3.4 mm) and then leveled off. At T1, PS had greater success rate of 4.5-mm screw placement than laminar screws (US > IBS > SBS); at T2, US had greater success rate than IBS, followed by PS and SBS; and at T3 to T6, laminar screws (US > IBS > SBS) had greater success rate than PS in all comparisons. Except for SBS at T1, laminar screw diameters with more than 90% success rates were between 3.5 and 5.0 mm., Conclusion: In view of their anatomic feasibility, laminar screws can be a viable alternative to PSs in the upper thoracic spine. Particularly at T3 to T6 where the pedicle width is inherently small, the success rates of laminar screw placement were significantly and consistently higher than those of PS placement. The comparable success rates of laminar screws using commercially available screw sizes further emphasize their potential clinical use.

Authors chose anterior approach through the antecubital fossa for better exposure in that case of isolated coronoid process fracture. The objective of the study was to report validity of anterior approach for the Regan and Morrey type III, isolated fracture of the coronoid process of the ulna without residual valgus or varus instability. From January 2007 and January 2010, we evaluated eleven consecutive patients (7 men, 4 women; mean age 44 years; range 25-67 years) who underwent surgical fixation through the anterior approach. The mean follow-up period was 21 months (range 15-34 months). Preoperative and follow-up roentgenograms were evaluated for assessment of the fracture configuration and confirmation of fracture union. Clinical evaluation included an analysis of surgical complication, range of motion, Mayo elbow performance score, and DASH (disability of the arm, shoulder, and hand) score. Fractures were mainly fixed with plate and screws in 8 cases, cannulated screws in 3 cases. There was no residual joint instability after fracture fragment fixation. All fractures were united, and the average union time was 15.2 weeks with a range of 11-20 weeks. Mean flexion contracture of the elbow was 3.6° (range 0°-10°), and further flexion was 130.9° (range 125°-140°) at the last follow-up. Mean Mayo elbow performance score was 92.3 (range 80-100 points), and mean DASH score was 5.9 (range 1.6-8.3 points). In conclusion, Primary fixation of the coronoid process fractures through the anterior approach could be particularly useful in the Regan and Morrey type III isolated coronoid process fractures.

Micro-screws (MSs) have gained rapid popularity among orthodontic specialists over the past decade. Subsequently, as general dental practitioners (GDPs) continue to provide general care for patients undergoing orthodontic treatment they are likely to encounter MSs. This article is aimed at GDPs and provides an overview of MS design, placement, removal and safety. Two examples of treated cases will also be used to demonstrate the use of MSs in contemporary orthodontic practice.

Purpose: To compare intersegmental displacements after mandibular setback sagittal split ramus osteotomy with reference to the fixation system applied: miniplate with monocortical screw, 3 bicortical screws, and 1 bicortical screw and 2 resorbable screws., Materials and Methods: The 42 subjects were divided into 3 groups according to the osteosynthesis method applied. To evaluate the intersegmental displacements from immediately after surgery (T0) to 6 months after surgery (T1), 2 cone-beam computed tomographic data sets were superimposed on the symphyseal area and the lower part of the mandible below the root apex. On the superimposed 3-dimensional images, the mean and standard deviation of the differences of the coordinates (x, y, z) between T0 and T1 were calculated., Results: From T0 to T1, group B (bicortical screws) manifested the greatest condylion (Cd) and coronoid process (Cp) displacements (P < .05). In group A, the right Cd moved anteriorly and the left Cd moved anteriorly and inferiorly, whereas the right and left Cps moved anteriorly. In group B, the right and left Cps moved laterally and inferiorly. In group C, the right Cd moved anteriorly and inferiorly, the left Cd changed laterally and anteriorly, the right Cp moved anteriorly, and the left Cp moved anteriorly and inferiorly., Conclusions: In the present study, group B (bicortical screws) showed the greatest displacement after the healing period. In view of these findings, surgeons should consider carefully their choice of osteosynthesis method to effectively decrease intersegmental displacement., (Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Introduction: Implanting on an atrophic maxilla alveolar ridge may require bone augmentation. Screwed expanders may sometimes be used, thus avoiding a more invasive bone graft. It allows bone density to increase and results in alveolar ridge expansion, by using bone elasticity and adaptation, allows the optimization of the available bone volume, with low morbidity., Technical Note: Despite its apparent simple implementation, the technique should be adapted to each type of bone so as to optimize results. We present two clinical cases, use of screwed expanders, their action on the crestal bone, and the limitations of this technique depending on ridge configuration., Discussion: Screwed expanders are non-traumatic easy-to-use tools. They can be inserted like implants because they have a good self-tapping effect. Their use is more secure in narrow spaces; they are more comfortable for the patient than impacted expanders use. They allow increase of cancellous bone density, which improves primary stability in case of low density bone. Bone volume preservation and avoiding bone grafts can shorten the implant treatment procedure and decrease costs for the patient. Unfortunately, this technique does not allow alveolar ridge height increase. If this is required, onlay graft or guided tissue generation are the best alternatives., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Purpose: One of the most common types of failure in dental implants is fracture of the abutment screw, after which the remnant is usually not easily removed. The purpose of this study was to investigate the effect of abutment screw length on the amount of screw resistance load and strain after loading., Materials and Methods: Twenty-one implants and straight abutments were prepared. The implants were placed in acrylic resin blocks at an angle of 30 degrees relative to the long axis. The abutment screws were prepared and classified into seven groups based on length (n = 3 abutments per group). The implants and abutments were joined with a torque of 30 Ncm. Strain gauges were attached to the abutments, and the implant-abutment assemblies were compressed. Curves of strain over time, peak load, and load at fracture were measured. Linear models of the variables over the abutment screw length were analyzed., Results: The break and peak loads were significantly associated with abutment screw length. However, all measured break and peak loads were greater than the maximal occlusal force. There were no significant changes in peak or break strain values associated with screw length (P > .05)., Conclusions: Clinically, fractured abutment screws may be replaced by shorter abutment screws without removal of the broken screw remnant.

Study Design: Numerical modeling and simulations of scoliotic spine instrumentation using monoaxial, uniaxial, polyaxial, and multiple-degrees-of-freedom (6DOF) postloading pedicle screws., Objective: To biomechanically analyze the general curve reduction effects and bone-screw force levels of monoaxial, uniaxial, polyaxial, and 6DOF pedicle screws for scoliotic spine instrumentation., Summary of Background Data: The ideal spinal fusion construct for treating scoliosis is still debatable. Studies on the effects of different types of implants were mainly based on postoperative radiograph measurements. Systematic studies are yet to be done on how bone-screw forces are correlated with screw types., Methods: Computer biomechanical models were built using 3-dimensional geometry and spine stiffness of 10 patients with adolescent idiopathic scoliosis having undergone spinal instrumentation. The surgical instrumentations were simulated each time, using a different type of screw. For each case and screw type, 15 screw placement variations were simulated to investigate their effects on bone-screw forces., Results: The maximum differences between different screw types were 6.4°, 1.1°, and 4.7°, respectively, for main thoracic Cobb angles, main thoracic apical vertebral rotation, and thoracic kyphosis (1.2°, 0.3°, and 0.3° on average). The average bone-screw forces were higher for monoaxial (229 N ± 140 N) than uniaxial (206 N ± 122 N), polyaxial (141 N ± 99 N), and 6DOF screws (103 N ± 42 N). Bone-screw forces with monoaxial screws were, respectively, 1.1, 2.5, and 25 times more sensitive to screw placement variation than uniaxial, polyaxial, and 6DOF screws., Conclusion: The bone-screw loads of different screws were significantly different. The descending order of bone-screw loads was monoaxial, uniaxial, polyaxial, and 6DOF screws. For patients with large and stiff spinal deformities or for patients with compromised bone quality, screws with more degrees of freedom offer better perspective to reduce bone-screw connection failure.

Purpose: The purpose of this study was to compare the interfragmentary compression force across a simulated scaphoid fracture by two commonly used compression screw systems; the Acutrak 2 Standard and the 3.0 mm Synthes headless compression screw., Methods: Sixteen (8 pairs; 6 female, 2 male) cadaver scaphoids were randomly assigned to receive either the Acutrak 2 or Synthes screw with the contralateral scaphoid designated to receive the opposite. Guide wires were inserted under fluoroscopic control. Following transverse osteotomy, the distal and proximal fragments were placed on either side of a custom load cell, to measure interfragmentary compression. Screws were placed under fluoroscopic control using the manufacturer's recommended surgical technique. Compressive forces were measured during screw insertion. Recording continued for an additional 60s in order to measure any loss of compression after installation was complete. The peak and final interfragmentary compression were recorded and paired t-tests performed., Results: The mean peak compression generated by the Acutrak 2 Standard was greater than that produced by the Synthes compression screw (103.9 ± 33.2 N vs. 88.7 ± 38.6 N respectively, p = 0.13). The mean final interfragmentary compression generated by the Acutrak 2 screw (68.6 ± 36.4 N) was significantly greater (p = 0.04) than the Synthes screw (37.2 ± 26.8 N). Specimens typically reached a steady state of compression by 120-150s after final tightening., Conclusion: Peak interfragmentary compression observed during screw installation was similar for both screw systems. However, the mean interfragmentary compression generated by the Acutrak 2 Standard was significantly greater. Our study demonstrates that the Synthes headless compression screw experienced a greater loss of interfragmentary compressive force from the time of installation to the final steady state compression level. The higher post-installation compression of the Acutrak 2 Standard may be attributable to the greater number of threads throughout the entire length of the screw. The clinical significance of these results, are, at this point uncertain. We do demonstrate that a fully threaded design offers a more reliable compression that may translate to more predictable bony union.

The current study evaluated the success and the possible complication of intermaxillary fixation with self-tapping and self-drilling screws (STSDSs) in nondislocated or slightly dislocated mandibular fractures.Forty patients with mandibular fractures, treated with intermaxillary fixation using STSDSs, were clinically assessed by means of a dental vitality test and evaluation of tooth mobility adjacent to the cortical screw holes, and radiologically by means of a panoramic dental radiograph upon removal of the screws.The main complication was screw loss in 4.4% of cases, followed by coverage by oral mucosa in 1.2% of cases. However, no dental root damage, screw breakage, malocclusion, or poor consolidation of mandibular fractures was observed.The use of STSDSs for intermaxillary fixation is a useful alternative to the use of arch bars in the treatment of some types of mandibular fractures. In addition, there is no risk of dental lesions as with self-tapping screws.

Background: Following open reduction, internal fixation of fractures of the mandible is predominantly achieved using plates and screws. Today, a multitude of osteosynthesis systems are available on the market. One therapy modality, primarily developed for orthopaedic surgery, is using angular stable osteosynthesis plate systems. The dominating principle of these is the bond between screw and plate following insertion. This principle of an "internal fixateur" results in a more stable fixation of the fragments associated with less compression of the bone surfaces., Material: A new multidirectional osteosynthesis system (TiFix=Smartlock, Hamburg - Germany) was modified to fit the maxillofacial region and compared with four other well established osteosynthesis systems developed by Mondial, Medicon, Synthes, Leibinger-Stryker, one of these (Unilock by Synthes) being also angular stable. The resistance to deformation in varying directions was investigated following fixation in four different materials., Results: The TiFix system proved more resistant to deformation even when mounted with fewer screws than the non-angular stable systems., Conclusion: This system results in greater stability even when fewer screws are used. For the clinician this means smaller access incisions, less soft tissue trauma, better aesthetic results, decreased duration of operation and a reduction of costs.

Though not a novel therapeutic concept, the use of miniscrew implants to obtain absolute anchorage has recently become very popular in clinical orthodontic approaches. The mode of anchorage facilitated by these implant systems has a unique characteristic owing to their temporary use, which results in a transient, albeit absolute anchorage. The foregoing properties together with the recently achieved simple application of these screws have increased their popularity, establishing them as a necessary treatment option in complex cases that would have otherwise been impossible to treat. The aim of this comprehensive review is to present and discuss the development, clinical use, benefits, and drawbacks of the miniscrew implants used to obtain a temporary but absolute/skeletal anchorage for orthodontic applications. Topics to be discussed include classification, types and properties (e.g., biocompatibility, osseointegration, types of anchorage, screw head, and thread design), clinical applications, site and placement method selection, clinical procedures for implant insertion, and loading and removal processes. Lastly, the potential complications and the advantages and disadvantages accompanying their use are presented.

In this paper we reviewed 28 patients who had been treated surgically for lumbar degenerative spondylolisthesis. They were operated between 1998-2003. The decompression and anterior lumbar interbody fusion with the use of interbody cages, was performed in all of them. The outcome was assessed using rating system of Prolo and VAPS. The disc height, degree of slippage and segmental lordosis were measured, on the radiographs, before surgery, after 6 weeks and at the time of final follow-up. In all cases spinal fusion was achieved. The disc height, degree of slipage and segmental lordosis were improved and these results were stable in time. A significant decrease in radicular pain and low back pain were seen but the relation between clinical and radiological autcomes was not observed.

Objective: To evaluate long-term outcome of repair of femoral capital physeal fractures with 70 mm cannulated screws in juvenile bulls that weighed >350 kg (770 lb)., Design: Retrospective study., Animals: 20 bulls., Procedure: Medical records of affected cattle were identified and reviewed. Follow-up information was obtained by means of a written questionnaire, 1 to 15 years after discharge, from the veterinarians who supervised the postoperative care at bull stud facilities., Results: Mean age and body weight at time of repair were 19 months (range, 11 to 27 months) and 513 kg (1128.6 lb; range, 364 to 720 kg [800.8 to 1584 lb]), respectively. Surgical repair was performed with 70 mm cannulated screws. A second surgery to replace malpositioned implants was required in 1 bull. Fourteen of the 20 bulls were considered serviceable for semen collection after surgical repair, and persistent lameness was evident in 11 of the 14. Mean duration for bulls to become serviceable was 5.5 months (range, 2 to 11 months). Age, weight, duration of injury at the time of repair, and degree of reduction did not have a significant effect on whether surgical repair was successful. Six bulls remained severely lame and were euthanatized., Conclusions and Clinical Relevance: Results indicated that surgical repair of femoral capital physeal fractures in adolescent bulls with 70 mm cannulated screws placed in lag fashion has a good prognosis for long-term function in a semen collection facility.

Purpose: During the early postoperative period, the stability of the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. The aim of this study was to evaluate if the initial fixation strength of a new suspension screw is comparable to that of the biodegradable interference screw fixation technique in the hamstring reconstruction of the anterior cruciate ligament (ACL)., Type of Study: Experimental laboratory study., Methods: We evaluated the initial fixation strength of a biodegradable poly-L-lactide/tri-calcium phosphate (PLLA/TCP) screw that suspended the graft in the bone tunnel and compared it with the strength of an interference screw for fixation of hamstring grafts in ACL reconstruction using bovine knees. Single-cycle and cyclic loading tests were performed using a materials testing machine., Results: The suspension screw provided a significantly higher yield load and ultimate failure load than the interference screw. There was no significant difference in the stiffness of both techniques. The typical failure mode for the suspension screw was fracture of the screw and for the interference screw it was slippage of the graft past the screw. In cyclic testing, both methods of fixation ran out to 1,000 cycles up to 250 N with a mean displacement of 2.6 mm (range, 1.8 to 3.3 mm) for the suspension screw and 4.1 mm (range, 2.3 to 6.0 mm) for the interference screw. Only the grafts fixed with the suspension screw survived a protocol with 1,000 cycles up to 400 N., Conclusions: Our biomechanical data suggest that hamstring graft fixation using a biodegradable PLLA/TCP suspension screw provides an alternative to interference screw fixation., Clinical Relevance: Hamstring graft fixation using a suspension screw provides a reasonable alternative to interference screw fixation.

Objective: Compare the initial stability at the fusion site of ankle arthrodesis fixed with two and three screws., Design: Finite element models of ankle arthrodesis were developed from computed tomography images. Two-screw constructs were augmented with a third screw in different orientations and subjected to loads likely to affect the ankle postoperatively., Background: More stable fixation seems to increase the chance of fusion, as it minimises the motion between the tibiotalar interfaces., Methods: Non-linear elastic finite element analyses were performed in external torsion and dorsiflexion. The micromotions at the tibiotalar interface were computed to compare the two- and three-screw fixation in intact and flat-cut arthrodesis., Results: Adding a third screw reduced the micromotions at the fusion site. Inserting the third screw anteriorly predicted lower peak micromotions than inserting the screw posteriorly, except for the intact arthrodesis tested in dorsiflexion. Three-screw intact arthrodesis predicted lower peak micromotions than flat-cut arthrodesis., Conclusions: Better stability was predicted for three-screw ankle arthrodesis. In flat-cut arthrodesis, a third screw inserted anteriorly performed better than a posterior screw. In intact arthrodesis, a posterior screw seemed a better option when flexion stability was the main concern. Even with three-screw fixation, the configuration of the first two-crossed screws may still be important to improve the stability at the fusion site.

Study Design: An anatomic study evaluating the feasibility of posterior screw fixation on the lateral mass of the atlas and comparing the pullout force of C1 posterior lateral mass screws with that of occipital and C2 pedicle screws., Objectives: To study the feasibility, anatomy, and biomechanics of posterior screw fixation within the lateral mass of the atlas., Summary of Background Data: Occipitocervical fusion is a common choice for atlantoaxial dislocations. After that the movement of occipitocervical region will be restricted. If screws could be placed in the lateral mass of the atlas, 1) the movement of C0-C1 junction will be preserved; 2) through the screw the dislocated atlas could be pulled backward; and 3) the fractured lateral mass can be fixed using the posterior lateral mass screw directly., Methods: Thirty atlas specimens of native adults were used to measure pertinent clinical data. Six fresh upper cervical specimens were used to observe the association of the C2 nerve and the lateral mass of the atlas. The pullout force of the C1 lateral mass was measured and compared with that of screws placed into the occiput and C2 pedicle, respectively., Results: The distances from the midline to the midpoint of the C1 lateral mass, to the inner wall of the transverse foramen, and to the inner edge of the pedicle were 17.6 +/- 1.2 mm, 23.0 +/- 1.7 mm, and 14.2 +/-1.1 mm, respectively. The width and height of the C1 lateral mass were 11.6 +/- 1.4 mm and 12.7 +/- 1.0 mm, respectively. The distance between the inferior midpoint of the C1 lateral mass in the transverse plane of the midposterior arch of the atlas to the edge of the inferior atlas joint line was 4.1 +/- 0.7 mm. The width of the posterior arch at the point of vertebral artery overpass was 4.7 +/- 1.0 mm. The observation on the fresh specimens showed that the C2 nerve passes inferolateral to the C1-C2 joint and could be pulled sideways. The screw pullout force within the lateral mass of the atlas was 1818.16 +/- 422.67 N. This is significantly less than that of screws within the occiput, and there was no difference with that of a C2 pedicle screw., Conclusion: The width and height of the atlas lateral mass were larger than that of the C2 pedicle, and there was enough space to insert a 3.5-mm diameter screw in the atlas lateral mass over the C2 nerve. The pullout force of the screw on the lateral mass of the atlas was the same as that of the C2 pedicle screw. It is possible toinsert a 3.5-mm screw in the lateral mass of the atlas. The direction of the screw should be about 20 degrees anterosuperior in the vertical plane and 15 degrees inward in the horizontal plane. The suitable length of the screw should be approximately 22 mm inside the lateral mass.

This study used finite element simulation to investigate the load transfer mechanisms within the screw/vertebra complex under different interface conditions, and under varying screw lengths. Both bonded and contact conditions were employed to demonstrate the interface between the screw and vertebra. Loadings were applied at the superior surface of the vertebra and screw unthreaded end, respectively, to represent two modes of flexion loads. The results indicated that the screw within the vertebra underwent a series of discontinuities of loading, identified by the localized high contact pressures, thus creating localized bending moments. The peak stress of screw was located at the junction of the screw's hub and thread, which is consistent with the location of screw failure observed in a clinical setting and the values of peak stress in the screw were proportional to the amount of moments generated by the two loading modes. The interface condition plays an important role in transferring the force within the screw/vertebra complex. A contact interface condition induces significantly higher stress in the screw than the bonded condition. Therefore providing a binding surface (with HA, or porosity coating on the screw surface) between the screw and the vertebra might be the most effective way to prevent screw failure. The influences of screw length on the peak stress in the screw become negligible when the screw is of sufficient length to extend fully into the vertebral body.

The basilar crescentic osteotomy is a popular method for correcting moderate to severe hallux valgus. However, inadvertent dorsiflexion of the osteotomy can result from intraoperative malposition or from malunion after fixation failure. The mechanical properties of osteotomies are dependent on the nature of the osteotomy and the type of fixation. This study examines the mechanical properties of the SCARF and crescentic osteotomies of the first metatarsal by using a cannulated asymmetric pitched screw or AO cancellous screws. Sixteen human cadaveric first metatarsal specimens were tested in plantar to dorsiflexion cantilever bending by using a mechanical testing machine. The data was compared with our recent work on the mechanical properties of the SCARF and crescentic osteotomies. Ultimate load and stiffness of the SCARF osteotomy were superior to the crescentic osteotomy but were not dependent on screw type. Screw type was a prominent factor in the stiffness but not in the strength of the crescentic osteotomy. The ultimate load and the stiffness of SCARF osteotomy fixed with the cannulated asymmetric pitched screws were not significantly different compared with AO screws (ultimate load, 124.6 N [SD = 56.8] v 105.3 N [SD = 57.0]; stiffness, 52.0 N/mm [SD = 48.0] v 31.8 N/mm [SD = 19.0]). Modes of failure were fracture of the cortical bone bridge between the screw hole and the osteotomy in all crescentic osteotomies and fracture of the proximal dorsal bridge in all SCARF osteotomies. The superior mechanical properties of the SCARF osteotomy, fixed with cannulated asymmetric pitched screws, make this a more secure construct, with less risk of malunion than the crescentic osteotomy. Stiffness is an important mechanical factor that helps distinguish the mechanical performance of different osteotomy techniques.

Objective: Qualitative comparison of the initial stability provided by two joint preparation techniques and various screw configurations in ankle arthrodesis, using the finite element method.Design. A three-dimensional model of a healthy ankle was developed from computed tomography images. Two groups of models were built, one with the joint contours resected to produce flat surfaces, and the second with the joint contours preserved. In each case, a variety of screw orientations were examined., Background: Despite the improved results of ankle arthrodesis, failure rates due to non-union are still reported. The initial stability of the arthrodesis construct seems important in the final outcome of the fusion., Methods: Non-linear contact finite element analyses were performed in the arthrodesis constructs subjected to internal/external torsion and dorsiflexion. Micromotions at the bone-to-bone interface were calculated for frictionless and Coulomb friction contact, and compared for the two joint preparation techniques and screw configurations., Results: Overall lower peak micromotions were predicted when preserving the joint contours both in torsion and dorsiflexion. For both preparation techniques, the lowest micromotions tended to occur with the screws inserted at 30 degrees with respect to the long axis of the tibia, crossing above the fusion site. Inclusion of friction in the models caused a general decrease on the magnitude of the micromotions as compared to the frictionless case, but did not affect the ranking of the models., Conclusions: The finite element method can be used as a qualitative tool to study the initial stability of ankle arthrodesis, overcoming the difficulties of measuring bone-to-bone interface micromotions experimentally. Better initial stability was predicted for ankle arthrodesis when the joint contours were preserved rather than resected. Crossing the screws above the fusion site at a steeper angle also tended to increase the stability at the fusion site., Relevance: Finite element analyses can help during the pre-operative planning of ankle arthrodesis. When bone density is not compromised, preserving the joint contour and inserting the screws at less than 45 degrees to the long axis of the tibia, crossing over the arthrodesis site, may offer better initial stability.

The purpose of this study was to compare the compression effect of the 7.0-AO screw and the 6.5 mm Ideal Compression Screw (I.CO.S.) screw in an in vitro subtalar arthodesis model. Six fresh-frozen, human cadaver foot specimens were obtained for analysis. The subtalar joint was opened laterally without affecting the articular surfaces. ATekscan 5051 sensor with a maximum pressure of 250 PSI and a sensel-density of 62 sensel/sq-cm was placed into the joint, which allowed for continuous measurement of the contact area and contact forces achieved by one 7.0 AO-screw, and thereafter by one 6.5 I.CO.S.-screw. When tightening the screw, mean contact area increased by 0.21 cm2 for the AO-screw (p<0.05), and by 0.27 cm2 for the I.CO.S.-screw (p>0.05). When comparing the tightened AO-screw and I.CO.S.-screw, mean contact area increased from 1.40 cm2 to 1.97 cm2 (p<0.05). The mean contact force also increased when tightening the screws. This increase was 7.6 N for the AO-screw (p<0.05) and 14.8 N for the I.CO.S.-screw (p>0.05). When comparing the tightened AO-screw and I.CO.S.-screw, mean contact force increased from 54.9 N to 81.7 N (p<0.05). The obtained results have shown that the design of the screw influences the achieved compression force. The superior compression of the I.CO.S.-screw might be explained by the better gripping and additional compression mechanism of its head. The shape of the head of the cannulated AO-screw, in contrast, may be critical to resist against the weak cortical bone of the calcaneus, i.e. it can sink into soft bone resulting in a loss of compression force.

Study Design: Clinically relevant aspects of pedicle screws were subjected to electrical resistance testing., Objectives: To catalog commonly used pedicle screws in terms of electrical resistance, and to determine whether polyaxial-type pedicle screws have the potential to create a high-resistance circuit during stimulus-evoked electromyographic testing., Summary of Background Data: Although stimulus-evoked electromyography is commonly used to confirm the accuracy of pedicle screw placement, no studies have documented the electrical resistance of commonly used pedicle screws., Methods: Resistance measurements were obtained from eight pedicle screw varieties (5 screws of each type) across the screw shank and between the shank and regions of the screw that would be clinically accessible to stimulus-evoked electromyographic testing with a screw implanted in a pedicle. To determine measurement variability, resistance was measured three times at each site and with the crown of the polyaxial-type screw in three random positions., Results: Resistance across the screw shank ranged from 0 to 36.4 ohms, whereas resistance across the length of the monoaxial-type screws ranged from 0.1 to 31.8 ohms. Resistance between the hexagonal port and shank of polyaxial-type screws ranged from 0 to 25 ohms. In contrast, resistance between the mobile crown and shank of polyaxial-type screws varied widely, ranging from 0.1 ohms to an open circuit (no electrical conduction). Polyaxial-type screws demonstrated an open circuit in 28 of 75 measurements (37%) and a high-resistance circuit (exceeding 1000 ohms) in 5 of 75 measurements (7%)., Conclusions: Polyaxial-type pedicle screws have the potential for high electrical resistance between the mobile crown and shank, and therefore may fail to demonstrate an electromyographic response during stimulus-evoked electromyographic testing in the setting of a pedicle breech. To avoid false-negative stimulus-evoked electromyographic testing, the cathode stimulator probe should be applied to the hexagonal port or directly to the screw shank, and not to the mobile crown.

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 engineering designs of fixation screws on the predicted screw-bone stress transfer, and consequently, on the biomechanical conditions for osteosynthesis. A dimensionless set of stress-transfer parameters (STP) was developed to quantify the screw-bone load sharing, enabling a convenient rating to be given of the biomechanical compatibility of practically any given screw design according to the nature of the simulated mechanical interaction. The results indicated that newly proposed screw designs, i.e. a "graded-stiffness" composite screw with a reduced-stiffness-titanium core and outer polymeric threads and an "active-compression" hollow screw which generates compressive stresses on the surrounding bone, are expected to provide significantly better biomechanical performances in terms of the STP criteria, compared with conservative screw designs. Accordingly, the present work demonstrates that finite element computer simulations can be used as a powerful tool for design and evaluation of bone screws, including geometrical features, material characteristics and even coatings.

The Food and Drug Administration (FDA) is correcting a final rule that classified certain previously unclassified pre amendments pedicle screw spinal systems and reclassified certain post amendments pedicle screw spinal systems. The agency is correcting the rule to include an intended use that was inadvertently omitted from the codified language in the rule. In addition, the agency is correcting the rule to clarify that, when intended for certain uses, the device is a pre amendments, not a post amendments, device. These actions are being taken under the Federal Food, Drug, and Cosmetic Act (the act), as amended by the Medical Device Amendments of 1976 (the 1976 amendments), the Safe Medical Devices Act of 1990 (SMDA), and the Food and Drug Administration Modernization Act of 1997 (FDAMA).

Four mandibular screw-plate locking systems were studied in sheep. Three to four centimetres angular continuity resections of the mandible were performed and the defects bridged with pre-bent angular reconstruction plates fixed with four screws in the body part and three in the ramus. Each type was used four times. Clinical and radiological examinations were carried out 1 and 2 months later. All sheep were able to eat and ruminate normally throughout the postoperative period. Radiology revealed that 6/16 plates and 5/112 screws fractured during the follow-up period. In one type, no fracture occurred. Screw fracture was confined to just one reconstruction system. Six of 16 mandibles showed slight to moderate bone resorption under the plate. The results point to the internal shortcomings of the systems tested.

We studied the holding power during cut-out tests of 4 different screw fixation devices of the femoral head, correlated to head size and bone density, on 48 paired deep frozen proximal femurs of fresh gross specimens. We found no significant effect of the device on the holding power. There was a significantly higher maximal load at failure in large and dense heads. It seems then unnecessary to advocate more sophisticated but also more expensive devices to fix femoral neck fractures.