Bicortical Screws Research Articles

Assessment of biomechanical strength of titanium versus unsintered-hydroxyapatite/poly-L-lactic acid (u-HA/PLLA) osteosynthesis screws in bilateral sagittal split ramus osteotomy

Titanium osteosynthesis is considered to be stable for the bilateral sagittal split ramus osteotomy (BSSRO) procedure in orthognathic surgery but is disregarded owing to a multitude of complications, the most significant necessitating a secondary surgery for removal. Bioresorbable osteofixation devices, especially third-generation unsintered-hydroxyapatite/poly-L-lactic acid (u-HA/PLLA), are increasingly used in the mandibular region because of their strength and bioactive/osteoconductivity. To date, three titanium bicortical screws has been the standard for the rigid fixation of BSSRO. As data on the use of u-HA/PLLA bicortical screws are limited, we conducted an in vitro biomechanical strength test to evaluate the performance of 12-mm bicortical u-HA/PLLA screws in comparison with titanium screws using mandibular bone models. BSSRO was performed on all specimens, followed by fixation with either three titanium screws or three, four, or five u-HA/PLLA screws, and loading was performed using a clinically presumed occlusal force. Displacement forces (measured in newton ‘N’) of 50N, 130N, and 220N were applied. Our results showed that the use of three u-HA/PLLA screws was unstable, that of four u-HA/PLLA screws was comparable, and that of five u-HA/PLLA screws provided stability equal to that of the three titanium bicortical screws. Although further clinical assessment is needed, our study demonstrated that the five u-HA/PLLA bicortical screws are viable alternatives to titanium in BSSRO osteofixation.

Bicortical Compression and Construct Stability With Variable Pitch Locking Screws in Cadaveric Specimens.

A variable pitch locking screw is intended to provide interfragmentary compression combined with fixed angle stability of locking plate constructs. The objective of this study was to compare variable pitch locking screws (3.5-mm KreuLock Ti locking compression screws, Arthrex Inc., Naples, FL) with standard locking screws (from the same manufacturer) in bicortical fixation scenarios in cadaver bone by assessing (1) interfragmentary compression and plate-bone compression and (2) construct biomechanical stability. Nine matched pairs of fresh-frozen cadaveric specimens with an average age of 67.2 years (range, 37-83) were used. Interfragmentary compression and plate-bone compression associated with insertion of single bicortical screws were compared between the variable pitch and standard locking screws at increasing levels of torque. The specimens tested were distal tibiae having a simulated longitudinal fracture. Additionally, fibulae were osteotomized to create a stable longitudinal fracture pattern and were fixed with a 5-screw plate construct with either all variable pitch or all standard locking screws. One of the 5 screws was placed across the osteotomy without lagging. Fibulae were tested cyclically with axial with torsional loading to compare displacements, rotation, and loads at failure or tested in 4-point bending to compare construct stiffness and maximum force to failure. Interfragmentary and plate-bone compression forces in the distal tibia model varied across specimens but were significantly higher with variable pitch locking screws compared with standard locking screws [512 N (SD = 324 N) vs. 79 N (SD = 64 N), P = 0.002, and 242 N (SD = 119 N) vs. 104 N (SD = 123 N), P = 0.028, respectively]. In cyclic loading of fibula constructs, no significant differences were detected in construct axial displacement or angular displacement (P > 0.05). In 4-point bending, no differences were detected in maximum force or bending stiffness (P > 0.05). Variable pitch locking screws produced interfragmentary compression between cortices and plate-bone compression that was greater than that produced by standard locking screws. In a stable bicortical fibula fixation scenario under external loading, the stability of variable pitch locking screw constructs was similar to constructs with standard locking screws.

Computer modeling and validation testing for glenoid component rotation and optimal glenoid screw angles for reverse shoulder arthroplasty in an Asian population.

Good initial fixation of glenoid component for reverse total shoulder arthroplasty (RTSA) relies on component placement and screw purchase in the scapula bone. This is especially difficult in an Asian population with small glenoid geometry. Optimal glenoid component roll angle and screw angulation to achieve the longest screws for best fixation has not been defined in the current literature. Computer 3D modelling of 133 scapulas with RTSA performed were analyzed to determine patient specific optimal glenoid roll angle (GRA) for the longest bi-cortical screws attainable. The cranial-caudal angle (CCA), anterior-posterior angle (APA) and lengths for the superior and inferior screws were measured. Validation testing using calculated average (CA) angles and rounded average (RA) angles to the nearest 5 degree were recomputed for each case to determine the bi-cortical screw lengths achievable. The CA and RA screw lengths were compared against patient specific modelling using paired-sample t-tests. Average GRA was - 1.6°, almost perpendicular to the long axis of the glenoid and achieves an average bi-cortical screw length of 51.3mm and 45.5mm for the superior and inferior screws respectively. The CCA and APA were 9.1° cranial and 6.5° posterior for the superior screw and screw angulation of 11.2° caudal and 0.7° anterior for the inferior screw. Validation testing shows statistically shorter screw lengths in the CA and RA models compared to patient specific modelling (p < 0.01). Validation testing with average angles for GRA, CCA and APA demonstrates strong patient heterogeneity and anatomical variation. Despite this, screw lengths attainable in the RA group were > 38mm with good safety profile. Surgeons may consider the additional use of navigation-assisted, or 3D printed patient specific instrumentation to optimize baseplate and screw configuration for RTSA.

Impact of transpedicular fixation on thoracolumbar junction burst fracture stability: a biomechanical perspective

Introduction. The treatment of burst fractures at the thoracolumbar junction remains a contentious issue in vertebrology. Despite a broad array of surgical interventions available, many surgeons favor isolated posterior stabilization, which can be performed using either minimally invasive or open approaches. However, the biomechanical properties of these methods have not been thoroughly investigated. Objective: This study aims to evaluate the biomechanical stability of the thoracolumbar junction following transpedicular stabilization of a burst fracture at the Th12 vertebra, under different system configurations influenced by lateral flexion. Materials and Methods: A mathematical finite element model of the human thoracolumbar spine, featuring a burst fracture at the Th12 vertebra, was developed. The model included a transpedicular stabilization system with eight screws, simulating “long” stabilization. We examined four variants of transpedicular fixation using both mono- and bicortical screws, with and without the inclusion of two cross-links. Results: The study found that the load borne by the damaged Th12 vertebral body varied depending on the fixation system employed. Specifically, stress levels were 24.0 MPa, 27.3 MPa, 18.4 MPa, and 25.8 MPa for models with short screws without cross-links, long screws without cross-links, short screws with cross-links, and long screws with cross-links, respectively. At the screw entry points in the vertebral arch, the highest stress values were recorded at the L2 vertebra, showing 11.8 MPa, 14.0 MPa, 9.4 MPa, and 13.4 MPa for each respective model. Among the metal construct elements, the connecting rods consistently exhibited the highest stress, with values of 226.7 MPa, 313.4 MPa, 212.4 MPa, and 293.98 MPa, respectively. Conclusion: The results underscore that utilizing cross-links in the stabilization of burst fractures at the thoracolumbar junction, which is only feasible through an open installation, somewhat mitigates stress within the stabilized spinal segment. Meanwhile, the modeling of lateral flexion revealed only minimal differences in stress values between open and minimally invasive installations.

The Effectiveness of Artificial Intelligence-based Pedicle Screw Trajectory Planning in Patients With Different Levels of Bone Mineral Density.

Retrospective cohort study. To evaluate the effectiveness of pedicle screw trajectory planning based on artificial intelligence (AI) software in patients with different levels of bone mineral density (BMD). AI-based pedicle screw trajectory planning has potential to improve pullout force (POF) of screws. However, there is currently no literature investigating the efficacy of AI-based pedicle screw trajectory planning in patients with different levels of BMD. The patients were divided into 5 groups (group A-E) according to their BMD. The AI software utilizes lumbar spine CT data to perform screw trajectory planning and simulate AO screw trajectories for bilateral L3-5 vertebral bodies. Both screw trajectories were subdivided into unicortical and bicortical modes. The AI software automatically calculating the POF and pullout risk of every screw trajectory. The POF and risk of screw pullout for AI-planned screw trajectories and AO standard trajectories were compared and analyzed. Forty-three patients were included. For the screw sizes, AI-planned screws were greater in diameter and length than those of AO screws (P<0.05). In groups B-E, the AI unicortical trajectories had a POF of over 200N higher than that of AO unicortical trajectories. POF was higher in all groups for the AI bicortical screw trajectories compared with the AO bicortical screw trajectories (P<0.05). AI unicortical trajectories in groups B-E had a lower risk of screw pullout compared with that of AO unicortical trajectories (P<0.05). AI unicortical screw trajectory planning for lumbar surgery in patients with BMD of 40-120mg/cm3 can significantly improve screw POF and reduce the risk of screw pullout.

Clinical and radiographic outcomes using standard length of cannulated screws for traditional Latarjet procedure

PurposeThe purpose of this study was to evaluate the clinical and radiographic outcomes of open traditional Latarjet stabilization using 32mm and 30mm long cannulated screws in males and females respectively with a minimum of 2 years’ follow-up. MethodsWe retrospectively reviewed open Latarjet procedures using cannulated screws of standard length with a minimum of 2 years follow-up. Functional evaluation was performed with postoperative Rowe and Walch score, visual analogue scale for pain (VAS) and return to sport. Graft healing was assessed with CT scans at 4 to 6 months postoperatively. Patients were divided into 2 groups according to postoperative radiographic measurements: a bicortical or unicortical screw groups. The α angle between the shaft of the screw and the glenoid subchondral bone was measured for superior and inferior screws. Level of significance was 0.05. The post hoc power analysis was 0.89. ResultsA total of 69 patients met the criteria for inclusion. Of these patients, 60 (87%) were available for final follow-up (n =62 shoulders), with a mean age of 28.4 ±9.5 years (range, 16-55 years) at time of surgery. 56 males (93.3%) and 4 females (6.7%) were included. The mean final follow-up period was a mean of 38 months after the procedure (range, 25-48 months). 8 out 60 patients (13.3%) had persistent apprehension in abduction–external rotation position. One patient (1.7%) had a recurrence of shoulder subluxation. The mean Walch-Duplay score was 90±11.6 points (range, 40-100 points), and the mean Rowe score was 93.4±11 points (range, 50-100 points). The mean VAS score for the evaluation of pain was 0.9±1.3 (range, 0-4). The coracoid healed the glenoid neck in 87.1% (54/62) of the shoulders on the postoperative CT scan. Lower alpha angle for inferior and superior screws had more rate of unicortical fixation (P=0.05 and P=0.04, respectively). 14 out 62 (22.6%) shoulders were found unicortical screws. Six bicortical cases and 2 cases unicortical screws (25%) showed nonunion (p=0.86). There were 2 complications, one patient had hematoma that required drainage, one case had transient axillary nerve palsy which resolved spontaneously. No complications associated with the hardware were found. ConclusionOpen traditional Latarjet procedure using 32 mm and 30mm long cannulated screws in male and females respectively, provided good outcomes with acceptable complication rates. Unicortical screws fixation does not have a higher rate of non-union than bicortical screws.

Comparative Biomechanical Study of Different Screw Fixation Methods For Minimally Invasive Hallux Valgus Surgery: A Finite Element Analysis

BackgroundThere are different screw configurations utilised for minimally invasive hallux valgus (HV) deformity despite limited biomechanical data assessing the stability and strength of each construct. We aimed to compare the strength of various screw configurations for minimally invasive HV surgery using finite element analysis (FEA). MethodsA FEA model was developed from a CT of a female with moderate HV deformity. Five screw configurations utilizing one or two bicortical or intramedullary screws were tested. Stress analysis considered osteotomy displacement, maximum and minimum principal stresses, and von Mises stress for both implants and bone for each screw configuration. ResultsFixation with two screws (one bicortical and one intramedullary) demonstrated the lowest values for osteotomy displacement, minimum and maximum total stress, and equivalent von Mises stress on the bone and screws in both loading conditions. ConclusionThe optimal configuration when performing minimally invasive surgery for moderate HV is one bicortical and one intramedullary screw. Level of evidenceLevel III

Assessment of biomechanical stability of the thoracolumbar junction with a burst fracture of Th12 following surgical stabilization under rotational loading

The thoracolumbar junction is the most vulnerable to traumatic injuries, with over 65 % of injuries to the thoracolumbar spine occurring in this region. Objective: To examine the stress-strain state of the thoracolumbar spine model with a burst fracture of the Th12 vertebra under various transpedicular fixation options influenced by rotational loading. Materials and Methods: A mathematical finite-element model of the human thoracolumbar spine was developed, including a burst fracture of the Th12 vertebra and a transpedicular stabilization system containing eight screws implanted in the Th10, Th11, L1, and L2 vertebrae. Four variants of transpedicular fixation were modelled using short and long screws passing through the anterior surface of the vertebra, with and without two crosslinks. Results: The analysis showed sufficiently high loading values for both the bone structures of the models and the elements of the metal construct. The maximum stress level in the body of the damaged vertebra was 33.2, 26.7, 30.1, and 24.2 MPa, respectively, for models with monocortical screws without crosslinks, bicortical screws without crosslinks, monocortical screws with crosslinks, and bicortical screws with crosslinks. High values were also recorded for the vertebrae adjacent to the damaged one: 13.0, 8.4, 10.9, and 7.1 MPa for the L1 vertebra and 10.2, 8.9, 7.1, and 6.2 MPa for the Th11 vertebra in the respective models. The stress on the supporting rods was registered at 582.0, 512.5, 512.6, and 452.7 MPa respectively. Conclusion: The conducted analysis demonstrated that under rotational loading, the model with monocortical screws without crosslinks shows the highest peak loads at control points, whereas the model with bicortical screws and crosslinks shows the minimum. Meanwhile, models with short screws and crosslinks and long screws without crosslinks exhibit comparable results

Preventing Iatrogenic Fibula Fractures Using the Push-Pull Technique: A Biomechanical Comparison of Unicortical Versus Bicortical Post Screws.

Displaced diaphyseal fractures can be reduced using the push-pull technique, wherein a plate is affixed to the distal fragment of the fracture, a post screw is placed proximal to the plate, and a lamina spreader creates distraction. This study evaluated the load to failure and mechanism of failure of bicortical and unicortical post screws during reduction. Four matched pairs of cadaver legs were subjected to a 2-cm oblique osteotomy simulating a displaced, oblique diaphyseal fracture. A 6-hole compression plate was affixed to the distal fragment with 2 unicortical locking screws, and a 12-mm unicortical or 20-mm bicortical screw was inserted as a post screw proximal to the plate. A lamina bone spreader was used to exert a distraction force between the plate and the post screw. A mechanical actuator simulated the distraction procedure until failure. Maximum applied load, displacement, and absorbed energy were recorded and compared across unicortical and bicortical groups by paired t tests. At maximum load, we found statistically significant differences in displacement (P=.003) and energy absorbed (P=.022) between the two groups. All unicortical screws failed through screw toggle and bone cut-out. Bicortical screws failed through bending, with no visible damage to the bone at the screw site. When diaphyseal fractures are significantly shortened and require a greater distraction force to achieve reduction, bicortical screws demonstrate a higher mechanical load to failure and increased bone loss from the screw-removal site. A unicortical post screw may be used if minimal distraction is needed. [Orthopedics. 2024;47(5):308-312.].

Clinical study on freehand of bicortical sacral screw fixation with the assistance of torque measurement device

BackgroundSacral screw loosening is a typical complication after internal fixation surgery through the vertebral arch system. Bicortical fixation can successfully prevent screw loosening, and how improving the rate of bicortical fixation is a challenging clinical investigation.ObjectiveTo investigate the feasibility of improving the double corticality of sacral screws and the optimal fixation depth to achieve double cortical fixation by combining the torque measurement method with bare hands.MethodsNinety-seven cases of posterior lumbar internal fixation with pedicle root system were included in this study. Based on the tactile feedback of the surgeon indicating the expected penetration of the screw into the contralateral cortex of the sacrum, the screws were further rotated by 180°, 360°, or 720°, categorized into the bicortical 180° group, bicortical 360° group, and bicortical 720° group, respectively. Intraoperatively, the torque during screw insertion was recorded. Postoperatively, the rate of double-cortex engagement was evaluated at 7 days, and screw loosening was assessed at 1 year follow-up.ResultsThe bicortical rates of the 180° group, 360° group, and 720° group were 66.13%, 91.18% and 93.75%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P < 0.05). However, there was no statistically significant difference between the 360° group and the 720° group (P > 0.05).The rates of loosening of sacral screws in the 180° group, 360° group, and 720° group were 20.97%, 7.35% and 7.81%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P < 0.05). However, there was no statistically significant difference between the 360° group and the 720° group (P > 0.05). The bicortical 360° group achieved a relatively satisfactory rate of dual cortical purchase while maintaining a lower rate of screw loosening.ConclusionManual insertion of sacral screws with the assistance of a torque measurement device can achieve a relatively satisfactory dual cortical purchase rate while reducing patient hospitalization costs.

Post-BSSO condylar position stability: a comparison of miniplate and lag screw fixation

BackgroundThis study was conceived to assess the postoperative stability of condylar position following fixation with miniplates and lag screws after bilateral sagittal split osteotomy (BSSO).MethodsThis retrospective study included a cohort of 20 patients undergoing BSSO using the Obwegeser-Dal Pont modification. The bony segments were stabilized using either miniplates with two 2.0-mm monocortical screws per segment or three 2.0-mm bicortical lag screws along the mandible’s superior border. Pre- and postoperative (7-day interval) spiral computed tomography scans were conducted to assess skeletal changes across both groups. Data analysis employed Wilcoxon signed-rank and Wilcoxon rank-sum tests (α = 0.05).ResultsNo statistically significant difference was observed between the pre-and postoperative condylar position parameters (P>0.05). However, the lag screw group showed a marginal significant increase in the left condyle’s angulation (preoperative: 24.83 ± 6.37 vs. postoperative: 32.5 ± 4.93; P = 0.04). Changes in condylar height, length, and width were not statistically significant before and after BSSO in either groups (P>0.05). Nor was any statistically significant difference found between the miniplates and lag screws groups regarding condylar position parameters (P>0.05).ConclusionThe results indicated that both lag screw and miniplate fixation methods can be effectively employed in BSSO procedures without impacting condylar position parameters. Thus, either fixation method can be chosen depending on factors such as the surgeon’s preference and clinical outcomes.

Four-screw compression plate fixation for diaphyseal humerus fractures.

While many humeral shaft fractures can be successfully treated with nonoperative management, compression plating techniques using at least three or four screws on either side of the fracture are the current gold standard. We hypothesized that a less rigid construct using compression with only two screws on either side of the fracture can provide adequate strength for uneventful fracture union. This is a retrospective review of all the patients who underwent open reduction and compression plate fixation for acute diaphyseal humerus fractures (ADHFs) at an academic Level-1 urban trauma center between 2018 and 2023. Patients treated with compression plating using only two screws and three or four plate-holes on either side of the fracture (Group 1) were matched one-to-one with patients treated using the conventional number of screws (three or more on either side of the fracture - Group 2). The incidence of nonunion/malunion, infection, and implant failure was compared among the two groups. There were eleven matched patients in both groups. The nonunion, infection complications, and hardware failure rates were 0% and 9.1% for the control group (Group 2) and four-screw group (Group 1) respectively. This difference was not statistically significant (p = 1.00). Although convention dictates the use of six or more bicortical screws (at least three bicortical screws on each side of the fracture), four-screw bicortical fixation may be a feasible option for ADHFs treated with large fragment compression plating techniques.

Developing A Temporary External Fixator (TEF) for Mandibular Reconstruction using Two-Phase QFD and TRIZ Approach

A temporary external fixator (TEF) is a device used to bridge resection defects after sequestrectomy and before secondary mandibular reconstruction surgery. A well-designed TEF should be customizable and adjustable to accommodate individual patient needs. This study developed a TEF for mandibular reconstruction using the quality function deployment (QFD) and the theory of inventive problem-solving (TRIZ). Customer needs (CNs) were investigated from literature reviews and a survey. Subsequently, a questionnaire was developed, refined, and delivered to 22 experts to identify the essential principles of TEF. Afterwards, the QFD priorities were analyzed based on the acquired CNs and technical requirements (TRs), and the top priorities were found to be safety and adequate operational space. The guidelines for developing a TEF with TRIZ were established as follows: First, using carbon fiber epoxy composite and Ti-6Al-4V as the material for TEFs is recommended Second, permanent magnet should be inserted into the clamp lock bolts to prevent them from falling off during surgery. Last, replacing one Schanz screw with three Bicortical screws is recommended for the fixator pins. Additionally, it was also found that changing the screw size from 2.5–4.0 mm to 2.0–2.4 mm could reduce hole defects in the mandible.

Analysis of load distribution after transpedicular stabilization of burst fractures in the thoracolumbar junction

Background. In the structure of all traumatic spine injuries, the thoracolumbar junction is predominant, accounting for over 53 % of all vertebral fractures. One of the most clinically significant types of injuries in this area are burst fractures. The purpose was to study the stress-strain state of the thoracolumbar spine model with a burst fracture of the Th12 vertebra in various transpedicular fixation options under compression load. Materials and methods. The study developed and investigated a finite element model of the thoracolumbar spine with a burst fracture of the Th12 vertebra. The burst fracture was modeled by dividing the vertebral body of the Th12 into several planes, transforming it into separate fragments. The gaps between these fragments were filled with a material that simulated the interfragmentary regenerate. Variants of transpedicular stabilization using different types of screws, mono- or bicortical, and with or without cross-links, were examined. The model was analyzed under compression load. Results. The maximum level of stress among the bone structures directly involved in fixation was registered in the L2 vertebral body. It amounted to 19.9, 15.6, 19.4, and 15.1 MPa, respectively, for models with monocortical screws without cross-links, bicortical screws without cross-links, monocortical screws with cross-links, bicortical screws with cross-links. Simultaneously, the zone of screw entry into the arch of this vertebra shows values of 10.1, 15, 10.2, and 14.3 MPa for these models, respectively. Peak loads on the metal structure elements are observed on the rods, amounting to 212.5, 159.6, 203.7, 142.8 MPa, respectively, for the considered models. Conclusions. The results of the study showed that under the influence of compression load when modeling a burst fracture of the thoracolumbar junction, the use of long screws leads to a reduction in stress levels, both in the elements of the metal structure and in the bone elements of the model, while the use of cross-links has a negligible effect.

Evaluating osteoporosis and bone quality in the aging spine: modern considerations for surgical management in the geriatric population.

Surgical management paradigms of spinal pathologies in the aging population carry inherent substantial risks, with surgical complications being more prevalent among patients with osteoporosis compared to those with normal bone mineral density. In this narrative review, we aim to highlight important clinical understanding and considerations in perioperative evaluation and management of patients elected to undergo spinal surgery. Osteoporosis is a well-defined risk factor for mechanical complications following spinal surgery, and as such, perioperative optimization of bone health in the setting of surgery for geriatric patients remains a critical research area alongside intraoperative surgical augmentation techniques. Surgical techniques to circumvent challenges with instrumentation of poor bone mineral density have included augmentation of pedicle screw fixation, including segmental bicortical screw fixation techniques, cement augmentation with fenestrated screws, or use of expandable pedicle screws to improve bone-implant interface. Judicious selection of treatment modalities and subsequent perioperative optimization is paramount to minimize surgical complications. Contemporary guidelines and evolving paradigms in perioperative evaluation, optimization, and management of the aging spine include the advent of quantitatively evaluating computed tomography (CT) via assessment of the magnitude of Hounsfield units. Prescribing pharmacotherapeutic agents and monitoring bone health requires a multidisciplinary team approach, including endocrinologists and geriatricians to coordinate high-quality care for advanced-age patients who require surgical management of their spinal disorders.

Some aspects of biomechanics of the operated thoracolumbar junction following two-level corpectomy

Traumatic spinal injuries pose a significant medico-social challenge, with about 60% of all spine fractures occurring at the thoracolumbar junction. Optimizing care for these patients remains a critical issue, despite the development of numerous surgical and conservative treatment methods, with outcomes still far from ideal. A key factor contributing to the consistently high rate of unsuccessful surgical interventions, which lead to stabilization failures in both the early and late postoperative periods, is the disregard of the biomechanical characteristics of the thoracolumbar junction area. Clinical protocols often regulate intervention methods based on the degree and nature of damage to the thoracolumbar spine as a whole. Enhancing the reliability of fixation, while maintaining the number of transpedicular screws, can be significantly achieved by using cross-links and adjusting screw length. The purpose of our study was to investigate the distribution of loads on the metal construct elements and bone structures in the thoracolumbar junction after extensive decompressive-stabilizing interventions. The load was modeled with a backward tilt. A mathematical finite element model of the human thoracolumbar spine segment was developed, incorporating vertebrae Th9-Th11, L2-L5, with Th12-L1 vertebrae removed, as well as elements of the metal construct—interbody support and a transpedicular system. We modeled four variants of transpedicular fixation using both short and long screws that penetrate the anterior surface of the vertebral body, with and without the use of two cross-links. Stress parameters were monitored at 20 control points in the models. Comparative analysis of the results revealed that models including long bicortical screws and two cross-links demonstrated the best biomechanical performance when the torso was tilted backward, effectively reducing stress in critical areas and enhancing the durability and effectiveness of the fixation.

Does adjunctive fixation in conjunction with miniplate affect condylar position and morphology after mandibular advancement through bilateral sagittal split ramus osteotomy? A retrospective 3-dimensional CT comparative study

To minimize condylar positional and morphological changes after mandibular advancement through bilateral sagittal split ramus osteotomy (BSSRO), surgeons add either a bicortical screw or a two-hole plate distal to the conventional single miniplate. Since there have been no previous studies investigating the effect of this combination, our study aimed to evaluate the short- and long-term effects of these adjunctive fixation methods (AFM) on condylar positional and morphological changes after mandibular advancement through BSSRO.This retrospective cohort study included consecutive patients with retruded mandibles who were treated in the Department of Orthognathic and TMJ Surgery at West China Hospital of Stomatology, Sichuan University. The patients were divided into two groups based on the primary predictor variable, which was the addition of AFM — either a single bicortical screw or a two-hole plate in addition to the single miniplate. The primary outcome variable was the condylar positional and morphological changes after mandibular advancement through BSSRO. Three-dimensional facial CT scans were obtained at three different time points (preoperatively — T0, 1 week postoperatively — T1, and 1 year postoperatively — T2) and analyzed using ITK-SNAP, 3D Slicer, and SlicerSALT software. Intergroup comparisons were conducted with an independent t-test, with a p-value of <0.05 considered significant. Correlations between the variables were estimated by Pearson correlation. The study comprised 51 patients (32 females, 19 males; mean age 25.13 ± 4.24 years), involving a total of 81 condyles (21 unilateral and 60 bilateral).There was a significant difference in long-term condylar displacement in favor of AFM along with a single miniplate (p < 0.001). The bicortical screw group recorded less condylar displacement than the two-hole plate group horizontally (0.11 mm vs 0.22 mm) and sagittally (0.03 mm vs 0.17 mm), but more vertically (0.85 mm vs 0.03 mm). Bone formation associated with AFM occurred on all condylar surfaces, compared with only three surfaces in the single miniplate group.The adjunctive method in addition to the single miniplate fixation method showed less condylar displacement and more bone apposition after mandibular advancement through BSSRO. The follow-up duration variable was the only significant determinant for volumetric changes in the condyle.

Evaluation of Different Fixation Methods Combinations After L-Shaped Osteotomy Reduction Malarplasty: An In Vitro Biomechanical Study.

This in vitro study compared the stability of different fixation method combinations for the zygomatic complex after simulated L-shaped osteotomy reduction malarplasty, a common facial contouring surgery in East Asia with high postoperative complications due to poor fixation methods. The study used 108 zygoma replicas with various fixation methods combinations in the zygomatic body (L-shaped plate with short wing on zygoma and on the maxilla, two bicortical screws, one bicortical screw with L-shaped plate, square plate, and rectangular plate) and zygomatic arch (Mortise-Tenon structure, 3-hole plate, and Mortise-Tenon structure plus short screw). The failure force under incremental load was applied through the Instron tensile machine to a well-stabilized model using a rubber band simulating the masseter muscle and recorded the increasing force digitally. ANOVA test was used for comparison between recorded values (P < 0.05). The results showed that the most stable combination was a six-hole rectangular plate and a Mortise-Tenon structure plus one short screw (358.55 ± 51.64 N/mm2). The results also indicated that the placement vector of the fixation methods around the L-shaped osteotomy and the use of the two-bridge fixation method were important factors in enhancing the stability of the zygomatic complex. The study suggested that surgeons should choose appropriate fixation methods based on these factors to reduce postoperative complications and improve surgical outcomes. This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Unstable Vancouver B1 periprosthetic femoral fracture fixation: A biomechanical comparison between a novel C-shaped memory alloy implant and cerclage wiring.

To compare the biomechanical stability of a novel, C-shaped nickel-titanium shape memory alloy (SMA) implant (C-clip) with traditional cerclage wiring in the fixation of a Vancouver B1 (VB1) periprosthetic femoral fracture (PFF). In total, 18 synthetic femoral fracture models were constructed to obtain unstable VB1 fracture with an oblique fracture line 8 cm below the lesser trochanter. For each model, the distal portion was repaired using a 10-hole locking plate and four distal bi-cortical screws. The proximal portion was repaired using either three, threaded cerclage wirings or three, novel C-shaped implants. Specimens underwent biomechanical testing using axial compression, torsional and four-point bending tests. Each test was performed on three specimens. The C-clip was statistically significantly stronger (i.e., stiffer) than cerclage wiring in the three biomechanical tests. For axial compression, medians (ranges) were 39 (39-41) and 35 (35-35) N/mm, for the C-clip and cerclage wiring, respectively. For torsion, medians (ranges) were, 0.44 (0.44-0.45) and 0.30 (0.30-0.33) N/mm for the C-clip and cerclage wiring, respectively. For the four-point bending test, medians (ranges) were 39 (39-41) and 28 (28-31) N/mm; for the C-clip and cerclage wiring, respectively. Results from this small study show that the novel, C-shaped SMA appears to be biomechanically superior to traditional cerclage wiring in terms of stiffness, axial compression, torsion and four-point bending, and may be a valuable alternative in the repair of VB1 PFF. Further research is necessary to support these results.

Comparing the Biomechanical Stability of Cerclage Cable with Plate Insert Versus Locking Screw in Periprosthetic Humeral Fracture.

In the setting of periprosthetic humeral fractures, the humeral stem of the implant represents a substantial challenge to the optimal method of proximal fixation. This study aimed to compare the initial biomechanical stability provided by cerclage cables with a locking plate insert versus bicortical locking screws (i.e., the gold standard for fixation) in fresh cadaveric humeri. After calculating the sample size, we utilized 10 sets of cadaveric specimens and created a 5-mm osteotomy gap 120 mm distal to the tip of the greater tuberosity, simulating a Wright and Cofield type-B periprosthetic humeral fracture on each specimen. Using 3 locking screws for distal fragment fixation, identical in all specimens, the specimens were assigned to Group A (3 cerclage cables with a plate insert) or Group B (3 locking bicortical screws) for proximal fragment fixation. Biomechanical tests included stiffness in varus and valgus bending, torsion, and axial compression, and a single load to failure. No significant differences were observed in the biomechanical metrics between the 2 groups. Our study revealed that fixation with use of cerclage cables with a plate insert demonstrated biomechanical stability comparable with that of bicortical locking screw fixation when addressing the proximal fragment in Wright and Cofield type-B periprosthetic humeral fractures. For proximal fragment fixation of periprosthetic humeral fractures, cerclage cables with a plate insert can be utilized as an effective fixation method that offers initial fixation strength that is comparable to the use of 3 locking bicortical screws.