Dual Screw Research Articles

A Biomechanical Analysis of Instrumentation Constructs During Vertebral Column Resection: Stability When You Need It!

Biomechanical Testing. Investigate the optimal construct for stabilization of the spine during vertebral column resection (VCR). VCR is a powerful technique for achieving correction in severe cases of spinal deformity. However, this also creates an unstable spine which requires stable fixation to prevent iatrogenic neurologic injury. It is common practice to place a temporary unilateral rod configuration to achieve this stability during surgery but no study to date has investigated the optimal construct configuration. A unilateral VCR model representing an acute 50° kyphotic deformity with a standardized 30mm resection was created. Three conditions underwent testing: 1) Rod material and diameter, 2) rod configuration, and 3) number of fixation points. Six unique samples were tested in each group in both flexion-extension. Prior to testing a 10N preload and underwent cyclical testing in flexion/extension. System stiffness was calculated and compared across groups. Assessment of rod size and composition using a single screw construct (2 total screws) demonstrated that for Titanium (Ti) rods, increasing rod size significantly increased the construct stiffness (P=0.001). Although Cobalt-chromium (Co-Cr) rods where significantly stiffer than the corresponding sized Ti rods, there was no significant difference between rod diameters for Co-Cr (P=0.98). However, when tested using a dual screw (4 total screws) construct, these constructs were significantly stiffer than the corresponding single screw constructs (P<0.0001). Of the various rod configurations, the dual rod demonstrated the greatest stiffness (34.8±2.1N/mm; P<0.0001). Surgical construct stiffness during a VCR is multifactorial. Larger rod diameter, increased number of fixation points, stiffer rod material, and increased number of rods across the resection site increase the construct stiffness. With minimal points of fixation using Co-Cr rods, increasing rod diameter does not impart greater construct stiffness unless additional fixation points are included.

A Retrospective Case Series of Single-Screw vs Dual-Screw Fixation for Treatment of Medial Malleolus Fractures.

Medial malleolus fractures (MMFs) are common across the world. Currently, there is a lack of consensus on the number of screws used in fixation of MMF. Our aim was to compare the radiographic outcomes of MMF with patients between fractures that have either undergone single-screw (SS) or dual-screw (DS) fixation. This retrospective study assessed patients who had undergone fixation of their MMF from 2012 to 2022. Analysis of their perioperative radiographs was performed to determine the initial type of injury and then radiographic outcomes of nonunion and malunion. A total of 653 patients suffering bimalleolar fractures were identified across a 10-year period. There were 271 patients (41.50%) in the SS group and 382 in the DS group (58.50%). There was no difference found in the nonunion rate of SS (19.19% [52 of 271]) compared with DS (18.85% [72 of 382]) (P = .931). A statistically significant difference between malunion rates was found between the SS group (11.07% [30 of 271]) compared with the DS group (3.93% [15 of 382]) (P < .001).On multiregression analysis, factors that gained significance for development of nonunion was nonfixation of syndesmosis (P = .039), ankle dislocation on arrival (P < .001), and nonrestoration of fibular length (P < .001). Other factors that showed significance for failure to achieve medial anatomical reduction was nonfixation of syndesmosis (P < .001). Use of an SS rather than DS showed a significant increase in nonanatomical reduction but did not increase nonunion or reoperation rate. Syndesmosis fixation was associated with higher rates of MMF nonunion and malunion; as such, surgeons should have a low index of suspicion of injury and fixation. Level III, retrospective case series.

CEPHALOMEDULLARY NAILING FOR SUBTROCHANTERIC FEMORAL SHAFT FRACTURES: A COMPARISON OF SINGLE LAG SCREW DEVICE WITH AN INTERCALATED DUAL SCREW DEVICE

Subtrochanteric femoral fractures are a subset of hip fractures generally treated with cephalomedullary nail fixation\[1\]. Single lag screw devices are most commonly-used, but integrated dual screw constructs have become increasingly popular\[2,3\]. The aim of this study was to compare outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture.Consecutive adult patients (18yrs) with subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Patients that underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022) were included. Medical records and radiographs were reviewed to identify complications of fixation. Cox regression analysis was used to determine the risk of mechanical failure and secondary outcomes by implant design. Multivariable regression models were used to identify predictors of mechanical failure.The study included 622 patients, 354 in the GN group (median age 82yrs, 72% female) and 268 in the IN group (median age 82yrs, 69% female). The risk of any mechanical failure was increased two-fold in the GN group (HR 2.44 \[95%CI 1.13 to 5.26\]; _p=0.024_). Mechanical failure comprising screw cut-out (_p=0.032_), back-out (_p=0.032_) and nail breakage (_p=0.26_) was only observed in the GN group. Technical predictors of failure included varus &gt;5° for cut-out (OR 19.98 \[2.06 to 193.88\]; _p=0.01_), TAD;25mm for back-out (8.96 \[1.36 to 58.86\]; p=0.022) and shortening 1cm for peri-implant fracture (7.81 \[2.92 to 20.91\]; _p=&lt;0.001_).Our results demonstrate that an intercalated screw construct is associated with a lower risk of mechanical failure compared with the a single lag screw device. Intercalated screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures.

Comparative Study between Proximal Femoral Nail Anti Rotation and Proximal Femoral Nail Anti Rotation Asian to Assessing Functional Outcome.

Intertrochanteric fractures are one of the most common fractures around the pelvis and hip joint. Intrerotrochanteric fracture commonly occurs in elderly adult as a result of a simple domestic fall or slippage due to osteoporosis and young adult due to high-energy trauma. In 1990, 26% of all intertrochanteric fractures were reported in Asia, this figure is estimated to 32% in 2025 and 38% in 2050. The main purpose of our study to differentiate functional, radiological, and clinical outcomes of intertrochanteric fracture treated with Proximal Femoral Nail Anti-rotation and Proximal Femoral Nail Anti-rotation Asian. This was a randomized prospective study of 68 intertrochanteric fracture patients (34 cases in the PFN group and 34 cases in the PFN A2 group) from February 2022 to April 2024. Data were collected based on the Harris Hip Score questionnaire at 6 weeks, 3 months, and 6 months and data were entered into Microsoft Excel. Demographic data, surgical duration, intraoperative blood loss, union rates, and complications were recorded and compared between both groups. Statistical analysis was done using Statistical Package for the Social Science software version 26. The mean age was 66.2 ± 15.8 in PFNA2 group whereas 63.1 ± 16 years in PFN group. Majority of the patients were male (63.2%) in both groups whereas female constituting 36.8%. Surgical duration and intraoperative blood loss were significantly less in the PFN A2 group, but functional outcome at 6 weeks, 3 months, and 6 months; complications were not significantly different in both groups. Screw cutout noticed in PFN A2 whereas reverse Z effect observed in PFN follow-up cases. Our study infer that PFN A2 has significant advantages when compare to conventional PFN like statistically significant less surgical duration and intraoperative blood loss with faster union time with smaller incision. Implant-related complications are lesser in PFN A2 that indicate biomechanical dominance of helical blade device over conventional dual screw system.

3D printing of a wood-based furniture element with liquid deposition modeling

Liquid deposition modeling is an energy-efficient, additive manufacturing process for pasty materials. Physical material properties were determined for a water-based paste consisting of the binder carboxymethyl cellulose and wood flour. A continuously operating dual screw extruder was developed, which was used to manufacture a table frame with a height of 18 cm.

A Retrospective Comparison of Single Screw vs Dual Screw Fixation for Treatment of Medial Malleolus Fractures

Category: Trauma; Ankle Introduction/Purpose: Medial Malleolus Fractures (MMF) are frequently managed by orthopaedic surgeons and are one of the most treated fractures of the ankle. Many approaches to fixation are described in the literature. Currently, there is a lack of consensus on the number of screws used in fixation when attempting lag-screw fixation of MMF. Aim: To compare the outcomes of MMF with patients between fractures which have either undergone single-screw (SS) or dual-screw (DS) fixation. Methods: Patients who had undergone surgical fixation of their MMF were identified from 2012 to 2022, using electronic patient records. Analysis of their pre-operative, intra-operative and post-operative radiographs was performed to determine the initial type of injury and then surgical outcomes relating to non-union, malunion and whether revision surgery was required. Results: A total of 653 patients were identified across a 10-year period. There were 271 patients (41.50%) in the SS group and 382 patients in the DS group (58.50%). When comparing the outcomes of SS compared to DS, a non-union rate of 19.19% (52/271) was found in the SS group as compared to 18.85% (72/382) in the DS group. There was a malunion rate of 11.07% (30/271) in the SS group as compared to 3.93% (15/382) in the DS group, which was statistically significant (p &lt;.001). On multi regression analysis, the other factors which gained significance for development of non-union was non fixation of syndesmosis (p= .039), ankle dislocation on arrival (p &lt;.001) and non-restoration of fibular length (p &lt;.001). Conclusion: Use of a single screw rather than double screw showed a significant increase in non-anatomical reduction but did not increase non-union or reoperation rate. Syndesmosis fixation has clear impact on the stresses on the medial malleolus and should have a low index of suspicion of injury and fixation.

Scaphoid fracture and nonunion: new directions.

The scaphoid is the largest of the carpal bones, articulating with both proximal and distal carpal rows. If scaphoid fractures are not appropriately diagnosed and treated, there is a risk of nonunion, osteonecrosis and degenerative arthritis. Operative management of the scaphoid fracture is primarily determined by the fracture location and amount of displacement. There is increased momentum for dual screw fixation constructs, intended to provide greater stability and reduce the risk of nonunion. Our current practice is to utilize two screws without graft as a first-line treatment for scaphoid nonunion with or without humpback deformity and cyst formation. This review will discuss the management of acute scaphoid fractures and the treatment of nonunion.

Reoperation rates after proximal femur fracture fixation with single and dual screw femoral nails: a systematic review and meta-analysis

PurposeThe purpose of this study was to investigate differences in aseptic reoperation rates between single or dual lag screw femoral nails,in the treatment of intertrochanteric fractures (ITF) in elderly patients.MethodsElectronic databases were searched for RCTs and prospective cohort studies treating elderly ITF patients with a single or dual screw femoral nails. Data for aseptic reoperation rates between single screw, dual separated screw and dual integrated screw devices were pooled using a random-effects meta-analysis with 95% CIs. Pooled proportions were compared using a N-1 chi-squared test. Complications contributing to aseptic reoperation rates were extracted, and the contribution of cut-out and periprosthetic fracture as a proportion of reoperations was analysed using a negative binomial regression model.ResultsForty-two (n = 42) studies were evaluated, including 2795 patients treated with a single screw device, 1309 patients treated with a dual separated screw device and 303 patients treated with a dual integrated screw device. There was no significant difference in aseptic reoperation rates between single and dual lag screw femoral nails of both separated and integrated lag screw designs. Moreover, complications of cut-out and periprosthetic fracture as a proportion of reoperations did not differ significantly between devices.ConclusionThe current evidence showed that aseptic reoperation rates were not significantly different between single and dual screw nails of a separated lag screw design. For dual integrated screw devices, due to insufficient evidence available, further high quality RCTs are required to allow for decisive comparisons with these newer devices.

The Utilization of Dual Second Sacral Alar-Iliac Screws for Spinopelvic Fixation in Patients with Severe Kyphoscoliosis.

ObjectivesAs a new pelvic fixation technique, the dual S2AI screws fixation technique could provide highly stable distal strength, and have wide clinical prospect in the correction of severe kyphoscoliosis. However, the ideal trajectory parameters, indications and clinical outcomes of this technique have not been reported so far. This study aimed to determine the anatomical parameters of dual S2AI screws in the normal Chinese adult population, investigating the indications of this technique and evaluating the feasibility and clinical outcomes.MethodsFifteen males and 15 females with normal pelvis underwent a pelvic CT scan to determine ideal dual S2AI screws trajectories. Sagittal angle (SA), transverse angle (TA), maximal length (ML), sacral length, and skin distance were measured. Subsequently, we retrospectively reviewed the data of 16 patients (seven males and nine females) who underwent dual S2AI screw fixation and 23 patients who underwent single S2AI screw fixation between January 2014 and December 2019. Preoperative, postoperative, and latest follow‐up measurements of Cobb angle, coronal balance (CB), spinal pelvic obliquity (SPO), and regional kyphosis (RK) were obtained. The mean follow‐up time was 16.7 ± 7.1 months (range: 12–30 months). Independent t‐test was used to determine the difference in the analysis of the trajectories. The paired sample non‐parametric Wilcoxon test was performed to assess the changes in radiographic parameters between different time points and different groups.ResultsFor both male and females, the proximal S2AI screws had significantly higher TA and ML, but a lower SA than distal screws. Females showed significantly more caudal (SA: 25.03° ± 2.32° vs. 29.82° ± 2.47°, t = 7.742, P < 0.001) trajectories of distal screw. Additionally, ML in the females were significantly shorter than that in males (106.81 mm ± 6.79 mm vs. 101.63 mm ± 6.55 mm, t = 3.007, P = 0.003, 124.41 mm ± 7.57 mm vs. 116.23 mm ± 7.03 mm, t = 4.337, P < 0.001). Eight had unilateral and eight had bilateral dual S2AI screw placement. Respectively, both the single S2AI and dual S2AI groups showed significant postoperative improvement of Cobb angle, RK angle and SPO angle. In patients with dual S2AI screws fixation, two patients found that screws loosening occurred in one of dual screws at 1‐year follow‐up, and in patients with single S2AI screws fixation, six patients found screw loosing as well as two patients found screw breakage at 1‐year follow‐up. None of all patients had any prominent loss of correction.ConclusionThe ideal trajectory of dual S2AI screw could be well established. The dual S2AI screw fixation technique is feasible in patients with severe kyphoscoliosis, and provides satisfactory correction of deformity with few postoperative complications.

Potential evaluation of water-cooled multiple screw chillers with serial water loops and development of ultra-efficient dual screw chillers

Applying serial water loops in multiple screw chillers has the potential to improve the COP of screw chillers above 7.0. However, the maximum potential of this method hasn’t been identified and the ultra-efficient target hasn’t been achieved until now. Therefore, an energy and exergy analysis is performed on the water-cooled multiple chillers with serial water loops in this paper to recognize their maximum potential. Analysis results show that the water-cooled multiple screw chillers with serial water loops have the maximum potential to increase COP by 26.02% and exergy efficiency by approximately 22% relative to the single screw chiller under the normal operating condition. Adding one chiller based on the single chiller system could increase the COP by 11.38%, and it is not suggested to design multiple chillers with more than four chillers owing to the reduced additional improvement in COP with the increasing number of chillers. Moreover, both condensers and both evaporators should be designed with the equal area of heat exchange, respectively, aiming to set the equal temperature difference through both evaporators and both condensers. On basis of analysis results, the ultra-efficient dual screw chillers were developed and tested. The COP and IPLV of the chillers reached 7.22 and 9.50, which were higher than the minimum allowable value of the first-order energy efficiency for water chillers by 20.3% and 26.67%.

A Novel Placement Technique of S2 Screw (from S2 to Promontorium) and Double Screwing from S2

AbstractSince pseudoarthrosis or screw loosening is frequently seen in lumbosacral stabilizations ending in S1, S2 screws are used more frequently to support S1 screws. This study aims to describe a new screw placement technique and location from S2. Revision surgery was applied to the patient who had previously undergone surgery with the rigid instrumentation system and encountered pseudoarthrosis during the follow-up period. Instrumentation was performed from S2 to the promontorium. The patient’s chronic low back pain arising due to pseudoarthrosis was reduced and a strong lumbosacral dynamic instrumentation was performed to the patient. Dual screw placement from S2 and/or screw placement in the S2-promontorium direction is a new alternative to provide a powerful instrumentation.

Kinematics and Dynamics of Flexible Robotic Manipulators Using Dual Screws

In this article, we present a new procedure for the derivation of the linearized kinematics and dynamics of a flexible industrial robotic manipulator. We introduce the Lie groups of dual rotation and dual homogeneous transformation matrices, which are the basis for the derivation of dual twists. In addition, dual screws and dual screw transformation matrices are introduced, which are used for the development of a general and systematic linearization procedure for both kinematics and dynamics. This leads to expressions that are linearized in all the states associated with the elastic motion. The dynamic modeling procedure is based on Kane's method, where the partial velocities and partial angular velocities are given as dual screws arranged as columns of dual projection matrices. The elasticity of the links is modeled by the assumed mode method. The presented procedure is implemented numerically for a 4-degrees of freedom manipulator and the simulation results are given.

Alternative Pedicle Screw Design via Biomechanical Evaluation

With the recent increase in the elderly population, many people suffer from spinal diseases, and, accordingly, spinal fusion surgery using pedicle screws has been widely applied to treat them. However, most research on pedicle screw design has been focused on the test results rather than the behavior of the screws and vertebrae. In this study, a design platform with a series of biomechanical tests and analyses were presented for pedicle screw improvement and evaluation. The platform was then applied to an alternative hybrid screw design with quadruple and double threads. An experimental apparatus was developed to investigate the bending strength of the screw, and several tests were performed based on the ASTM F1717 standard. In the experiments, it was confirmed that the alternative pedicle screw has the highest bending strength. To examine the stress distribution of pedicle screws, finite element models were established, through which it was found that the proposed pedicle screw has sufficient mechanical safety to make it acceptable for spinal fusion treatment. Finally, we conclude that the platform has good potential for the design and evaluation of pedicle screws, and the alternative dual screw design is one of the best options for spinal fusion surgery.

Biomechanical efficacy of four different dual screws fixations in treatment of talus neck fracture: a three-dimensional finite element analysis

BackgroundCurrent there are different screws fixation methods used for fixation of the talar neck fracture. However, the best method of screws internal fixation is still controversial. Few relevant studies have focused on this issue, especially by finite element analysis. The purpose of this study was to explore the mechanical stability of dual screws internal fixation methods with different approaches and the best biomechanical environment of the fracture section, so as to provide reliable mechanical evidence for the selection of clinical internal fixation.MethodsThe computed tomography (CT) image of the healthy adult male ankle joint was used for three-dimensional reconstruction of the ankle model. Talus neck fracture and screws were constructed by computer-aided design (CAD). Then, 3D model of talar neck fracture which fixed with antero-posterior (AP) parallel dual screws, antero-posterior (AP) cross dual screws, postero-anterior (PA) parallel dual screws, and postero-anterior (PA) cross dual screws were simulated. Finally, under the condition of 2400N vertical load, finite element analysis (FEA) were carried out to compare the outcome of the four different internal fixation methods. The results of Von Mises stress, displacement of four groups which contain talus fracture fragments and screws internal fixations were analyzed.ResultsCompared with the other three groups, postero-anterior (PA) parallel dual screws had better results in the stress peak, stress distribution, and displacement of talus and internal fixation.ConclusionsTo sum up, the Von Mises stress of fracture section was the smallest, the stress distribution of screws were the most scattered, and the peak value was the smallest in posterior to anterior parallel double screws fixation, which was obviously better than that in the other three groups. When using screws internal fixation, the method of posterior to anterior screws fixation is better than that of anterior to posterior screws fixation, and the peak value and stress distribution of parallel double screws fixation is better than that of cross double screws fixation. Thus, for the talar neck fracture, the use of posterior to anterior parallel double screws fixation is recommended in clinical surgery.

Nanostarch Surface Coating of Lightweight Coated Paper

Nanostarch has a small particle size and large surface area compared with traditional modified starch. In this study, nanostarch was prepared by dual screw extrusion and was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray diffraction (XRD). The nanostarch was studied as a coating adhesive in surface coating of lightweight coated paper. The crystallinity of nanostarch granules was decreased by dual screw extrusion, and its average particle size was about 100 nm. The results showed that for the paper coating formula of styrene butadiene latex and an ordinary oxidized coating starch ratio of 9:5, all ordinary oxidized coating starch and part of the styrene butadiene latex can be replaced by nanostarch. When 5 parts of ordinary oxidized coating starch and 4 parts of styrene butadiene latex were replaced by 6.5 parts nanostarch, the water retention property of nanostarch coating was increased by 64.0%, and its viscosity was decreased by 11.0%. The IGT printing surface strength of lightweight coated paper by the nanostarch coating was increased by 11.6%, and the glossiness of coated paper was increased by 7.2%. These results show that nanostarch surface coatings have good prospects for application in papermaking.

Biomechanical characteristics of four fixation methods in treatment of pubic symphysis disruption: a finite element analysis

Objective To evaluate the biomechanical characteristics of 4 fixation methods (single reconstruction plate, dual reconstruction plates, single cannulated screw and dual cannulated screws) in the treatment of pubic symphysis disruption. Methods Miniature spiral CT scans were performed on the complete pelvis in 5 healthy volunteers. The primary two-dimensional CT scan data at DICOM format were imported into software Mimics 15.0 for three-dimensional reconstruction of bilateral hips and sacrums. The finite element model of skeletal pelvis was obtained by grid partitioning and assignment using software Abqus 6.13. Models of pubic symphysis disruption were simulated by cutting off the unilateral sacroiliac ligament, sacral spine ligament, sacral tuberosity ligament, pubic ligament and pubic arch. Four implants(single reconstruction plate, dual reconstruction plates, single cannulated screw and dual cannulated screws) were simulated and emplaced onto the models according to standard surgical procedures. Compressive and rotational loads were implemented in all models for finite element analysis. The biomechanical properties were recorded and analyzed, including construct stiffness, micromotion of the pubic symphysis and von Misses stress. Results Under vertical load, the space of pubic symphysis disruption >25 mm. The vertical stiffness and rotational construct stiffness of the pelvis decreased significantly from 442.738±29.946 N/mm and 10.118±1.432 N·m/Deg in the normal group to 14.754±0.876 N/mm and 0.328±0.119 N·m/Deg, respectively. Dual reconstruction plates and dual cannulated screws displayed the best vertical tensile strength; their construct stiffness achieved 117.647±9.193 N/mm and 131.443±4.348 N/mm, respectively. Under anti-rotation load, dual cannulated screws displayed the best performance because they rebuilt 68.6% of the whole structural stiffness. For the local stability of the pubic symphysis, dual reconstruction plates showed a strong local anti-rotation capability and dual cannulated screws a good local anti-tensile capability. The displacement in the dual cannulated screws group was only -0.240±0.119 mm under vertical load while the angular displacement in the dual reconstruction plates group only 0.218°±0.182°. Single reconstruction plate endured the maximum von Misses stress which was obviously concentrated. Conclusion Dual cannulated screws may have biome-chanical advantages for treatment of pubic symphysis disruption. Key words: Pelvis; Finite element analysis; Biomechanical characteristics; Fractures fixation, internal; Comparative study

Prognostic value of the sliding length of cephalocervical screws to predict the risk of non-union after osteosynthesis: a retrospective analysis of 86 patients with intracapsular femoral neck fractures

BackgroundHere, we assessed the prognostic value of the early sliding length (ESL) for predicting the risk of non-union after internal fixation of femoral neck fractures (FNFs) by Dual SC Screws (DSCS).MethodsA retrospective analysis of 86 patients with intra-capsular FNFs was performed. They underwent osteosynthesis by DSCS at our institution between 2008 and 2013 with a minimum follow-up duration of 6 months. Preoperative displacement, fracture reduction quality, ESL of screws at 2 weeks postoperatively, and correlation of non-union with the ESL of screws were evaluated.ResultsBone union without complications was achieved in 74 patients (86.0%), whereas 12 patients (14.0%) showed non-union. The ESL was significantly longer in the non-union group (proximal 3.94 ± 2.79 mm, distal 4.03 ± 3.16 mm) than in the union group (proximal 0.98 ± 1.85 mm, distal 1.01 ± 1.84 mm, P = 0.0001* for proximal, P < 0.0001* for distal). The ESL was significantly associated with non-union, both in the proximal [P = 0.0002, unit odds ratio (OR) 1.58, 95% confidence interval (CI) 1.23–2.16] and distal screws (P = 0.0002, unit OR 1.53, 95% CI 1.21–2.02). The areas under the ROC curves for the ESL of proximal and distal screws were 0.845 and 0.867, respectively; the cut-off values to predict non-union were 1.0 mm (sensitivity 91.7% and specificity 74.3%) and 1.4 mm (sensitivity 83.3% and specificity 81.1%), respectively.ConclusionsIn this study, the ESL was a good predictor of postoperative non-union in patients with FNFs fixed by DSCS.

Comparison of Femoral Head Rotation and Varus Collapse Between a Single Lag Screw and Integrated Dual Screw Intertrochanteric Hip Fracture Fixation Device Using a Cadaveric Hemi-Pelvis Biomechanical Model.

This study compared the stabilizing effect of 2 intertrochanteric (IT) fracture fixation devices in a cadaveric hemi-pelvis biomechanical model. Eleven pairs of cadaveric osteopenic female hemi-pelves with intact hip joint and capsular ligaments were used. An unstable IT fracture (OTA 31-A2) was created in each specimen and stabilized with a single lag screw device (Gamma 3) or an integrated dual screw (IDS) device (InterTAN). The hemi-pelves were inverted, coupled to a biaxial apparatus and subjected to 13.5 k cycles of loading (3 months) using controlled, oscillating pelvic rotation (0-90 degrees) plus cyclic axial femoral loading at a 2:1 body weight (BW) ratio. Femoral head rotation and varus collapse were monitored optoelectonically. For specimens surviving 3 months of loading, additional loading was performed in 0.25 × BW/250 cycle increments to a maximum of 4 × BW or failure. Femoral head rotation with IDS fixation was significantly less than the single lag screw construct after 3 months of simulated loading (P = 0.016). Maximum femoral head rotation at the end of 4 × BW loading was 7× less for the IDS construct (P = 0.006). Varus collapse was significantly less with the IDS construct over the entire loading cycle (P = 0.021). In this worst-case model of an osteopenic, unstable, IT fracture, the IDS construct, likely owing to its larger surface area, noncylindrical profile, and fracture compression, provided significantly greater stability and resistance to femoral head rotation and varus collapse.

Subtle Lisfranc Subluxation: Results of Operative and Nonoperative Treatment

Subtle Lisfranc instability is typically a low-energy, twisting, axial-loading injury. The present study evaluated the operative treatment of subtle Lisfranc injuries after nonoperative failure. The data from consecutive patients with subtle Lisfranc instabilities were reviewed. Those in whom initial nonoperative treatment had failed underwent surgery. The American Orthopaedic Foot and Ankle Society (AOFAS) midfoot score was obtained initially, after nonoperative treatment, and, for those in whom nonoperative treatment had failed, after operative treatment. Of 36 patients enrolled, 16 (44.44%) were successfully treated nonoperatively, and 20 (55.56%) required surgery after nonoperative treatment had failed. Of those treated operatively, 9 (45%) were stabilized with dual screws and 11 (55%) with dual suture buttons. The mean follow-up period was 36 ± 12.2 months. The AOFAS scores significantly improved from the pre- to final post-treatment values. The overall mean pretreatment AOFAS score (62.8 ± 8.84) was significantly lower statistically than the mean overall post-treatment AOFAS score (91.3 ± 8.34; p < .0001). The mean AOFAS score before nonoperative treatment (61.9 ± 9.5) improved to a mean AOFAS score of 75.3 ± 15.8 after nonoperative treatment (p = .0029). The mean preoperative AOFAS score (63.5 ± 8.46) improved to a postoperative AOFAS score of 92.3 ± 8.43 (p < .0001). The mean AOFAS score before nonoperative treatment (61.9 ± 9.5) was not significantly different statistically from the mean preoperative AOFAS score (63.5 ± 8.46; p = .62). The mean AOFAS score after nonoperative treatment (75.3 ± 15.8) was lower than the mean postoperative AOFAS score (92.3 ± 8.43; p < .0001). Of the 9 feet stabilized with dual screws, 7 (77.78%) required screw removal during the observation period. Subtle Lisfranc injuries failing nonoperative treatment were successfully stabilized using either a dual screw or suture button technique.

Coupled Vibration Modal Analysis of Synchronous Dual Ball Screw Feeding System

With the Synchronous Dual Ball Screw Feeding System used in a Milling-Turning compound machining center as the research object. For study the ball screw vibration modal, which using Lagrange established the dynamics equation and using the Lizs series expansion analyzing its various order modal coupling characteristics. Meanwhile using the ANSYS analysis to get the first three order vibration mode diagram and calculate the frequency corresponding to the critical speed for each rank. Through the analysis found that the screw pitch determine the modal coupling axial and corner, the workbench position and load quality changes, the screw vibration frequency also changes. Provide theoretical analysis for the analysis of dynamic characteristics of the next step.