The Role of the Collateral Ligaments in Stabilizing the Distal Interphalangeal Joint in Fingers With Small Mallet Fractures: A Biomechanical Study.

Dermal filler injection can restore facial volume and improve contour; however, the precise mechanism underlying its lifting effect remains insufficiently characterized. This study explores how targeted filler placement within facial ligamentous structures contributes to mechanical support and contour elevation through anatomic, ultrasonographic, and biomechanical perspectives. Cadaveric dissection and high-frequency ultrasonography were conducted to examine the morphology, orientation, and density of major retaining ligaments, including the zygomatic, mandibular, and platysmal-auricular regions. Observations were correlated with clinical facial dynamics to delineate how sub-SMAS filler deposition affects fibrous anchoring structures. Facial retaining ligaments were identified as collagen- and proteoglycan-rich fibrous condensations providing localized tensile resistance. Age-related attenuation of these structures reduces their capacity to maintain facial suspension. Targeted sub-SMAS filler injection increased local fibrous density and enhanced SMAS tension, thereby transmitting mechanical lift to the skin through ligamentous attachments. Region-specific reinforcement of dense anchoring zones produced efficient contour elevation with minimal filler volume. The lifting effect of filler injection arises from a synergistic mechanism that combines volumetric restoration with biomechanical reinforcement of fibrous anchoring structures. Understanding the regional variability and mechanical behavior of facial ligaments enables anatomy-based, low-volume rejuvenation strategies that preserve natural dynamics. Further clinical and quantitative biomechanical studies are warranted to validate these observations under physiological conditions.

Introduction The optimal treatment for complex acetabular fracture involving the posterior wall and column remains controversial. To address this issue, a novel anatomically integrated acetabular plate (AIP) was developed, designed to integrate the biomechanical advantages of both reconstruction and T-shaped plates. This biomechanical study aimed to evaluate the mechanical performance of the AIP in comparison with conventional fixation methods. Methods Acetabular fractures involving the posterior wall and column were created in 18 fresh-frozen pelvis specimens and assigned to three fixation groups: (1) an anatomically integrated plate (AIP), (2) two reconstruction plates with a T-plate (RPTP), and (3) two reconstruction plates with two lag screws (RPLS). A standing position was simulated, and a Zwick Z100 testing machine applied an axial load from 0 to 1400 N. A load-displacement sensor and digital dial gauge were used to measure overall displacement, stiffness, and displacement of the posterior wall and column to evaluate the mechanical stability of each fixation construct. Results Under increasing axial loading, all three groups of model specimens exhibited a linear trend in axial displacement without sudden load drops. Among the groups, the AIP group demonstrated the smallest overall displacement (1.87 ± 1.09 mm), followed by the RPTP (2.29 ± 1.12 mm) and RPLS groups (2.63 ± 1.21 mm). No significant difference in displacement was observed between the AIP and RPTP groups under loads of 0–1000 N ( P > 0.05), whereas a significant difference emerged at higher loads of 1200–1400 N ( P < 0.05). Under a peak load of 1400 N, the axial stiffness followed the trend: Normal (NOR) group > AIP group > RPTP group > RPLS group, with mean stiffness values of 356.10 ± 12.33 N/mm, 339.87 ± 21.86 N/mm, 302.04 ± 13.69 N/mm, and 266.32 ± 9.16 N/mm, respectively. The AIP group exhibited significantly higher stiffness than both the RPTP and RPLS groups ( P < 0.05), with no significant difference between the AIP and NOR groups ( P > 0.05). Furthermore, the AIP group showed significantly lower displacement of the acetabular posterior wall and column compared to the RPTP and RPLS groups ( P < 0.05). Notably, two specimens in the RPLS group showed posterior wall displacements exceeding 2 mm, which met the criteria for internal fixation failure. Conclusion Overall, the AIP group provided the best biomechanical performance in terms of minimizing displacement and maximizing stiffness, followed by RPTP and RPLS group, indicating its potential superiority for the stabilization of acetabular fractures involving the posterior wall and column.

Background Ankylosing spondylitis (AS) commonly progresses to thoracolumbar kyphosis. Pedicle subtraction osteotomy (PSO) and Ponte osteotomy are frequently used surgical methods. However, systematic comparative biomechanical studies of these two methods are insufficient, and differences in postoperative mechanical complication risks remain unclear. Objective To compare the biomechanical characteristics of Ponte and PSO osteotomies in the treatment of AS with thoracolumbar kyphotic deformity, providing a biomechanical basis for clinical surgical decision-making. Methods Finite element models representing unresected (M0), Ponte osteotomy (M1), and PSO osteotomy (M2) conditions were constructed based on CT data from an AS patient. A vertical load of 500 N and moments of 10 N·m in each direction were applied to the T3 vertebral body. Six loading conditions, including flexion and extension, were simulated. Spinal range of motion (ROM), vertebral stress, internal fixation stress, and displacement were analyzed. Results Model validation showed that ROM of M0 was consistent with previous studies. After surgery, ROM significantly decreased in both osteotomies compared with M0, with M2 showing lower ROM than M1. In the M1 model, stress in the T3–T5 vertebral bodies decreased, but stress in T6 did not significantly change. In the M2 model, stress in T4–T5 vertebral bodies decreased, while stress in T7–T8 increased. Internal fixation stress in M1 was significantly lower than in M2 across all loading conditions, although displacement was greater in M1. Conclusion Ponte osteotomy distributes stress across multiple segments, reducing internal fixation load, and is therefore suitable for moderate kyphotic deformities. PSO osteotomy provides superior corrective capability but concentrates stress on distal vertebral segments, making it suitable for severe deformities. These results can guide clinical decisions for individualized surgical selection.

Effect of Edema on Flexor Tendon Tensile Forces Following Zone II Repair: A Biomechanical Analysis in a Cadaveric Model.

To compare the biomechanical performance of adjunctive locking plating and double-loop cerclage wiring in feline femora implanted with Zurich cementless total hip replacement (THR) stems. Cadaveric biomechanical study. Paired femora (n = 32) from 16 feline cadavers. Two sequential studies were performed. First, femora implanted with Zurich cementless stems alone were compared with those stabilized by an adjunctive locking plate. Second, femora with locking plates were compared with those with cerclage wires. Constructs underwent cyclic axial and torsional loading followed by load-to-failure testing. Outcome measures included residual axial and torsional displacement, yield and ultimate forces and torques, energy absorption, and brittle failure frequency. Parameters were normalized to bone volume. The locking plate group demonstrated substantially reduced residual torsional displacement and a trend toward lower axial displacement compared with the stem-only group. Yield and ultimate failure strength did not differ. The cerclage group exhibited 36% greater ultimate axial displacement, 76% greater energy absorption, and 32% greater torsional displacement than the locking plate group. Normalization accentuated these differences. Cerclage wire fixation was associated with a lower frequency of brittle failure. Locking plates improved cyclic stability by reducing micromotion, while cerclage wires enhanced compliance and energy absorption under destructive loading. Neither method increased load to failure. Adjunctive plate or cerclage wire provided biomechanical advantages in femora implanted with Zurich cementless THR stems. Locking plates may support implant stability, whereas cerclage wiring improves energy dissipation under supraphysiologic loading. Adjunctive fixation strategies should be tailored to patient-specific femoral morphology and fracture risk in feline THR.

Fractures of the posterior margin of the distal end of the tibia, also referred to as posterior malleolus fractures, represent an important but often underestimated component of ankle injuries. They are rarely isolated but rather occur as part of more complex fractures classified as Weber type B and C, or they accompany high-energy pilon tibial fractures and spiral fractures of the tibial shaft. In recent decades, there has been a significant shift in the understanding of biomechanical importance of the posterior malleolus, which plays a key role in maintaining the stability of the distal tibiofibular syndesmosis and preserving the congruency of the ankle joint surface. Indications for surgical treatment as well as surgical approaches and fixation techniques have changed dramatically. This review article aims to summarize current knowledge of these fractures, with a focus on anatomy, diagnosis, classification, and particularly surgical treatment options, including the choice of approach and methods of fragment reduction. The literature search was conducted in the PubMed and Web of Science databases, focusing on publications released before the end of 2024. The search included the following keywords: "posterior malleolus fracture," "posterior tibial margin," "ankle fracture," "CT classification," "syndesmosis injury," and "surgical fixation." Original clinical studies, review articles, anatomical and biomechanical studies as well as case reports that provide clinically relevant information on the diagnosis and surgical management of these fractures were included in the review. The introduction of CT imaging has significantly contributed to a better understanding of the morphology of the posterior margin and led to the development of new classification systems (Haraguchi, Bartoníček and Rammelt, Mason), which serve as a guide in selecting the optimal surgical approach. Fixation of the posterior malleolus has a positive effect on ankle and syndesmotic stability even in small fragments. The choice of surgical approach is individualized - the posterolateral, posteromedial, transfibular, or modified lateral approach are used most commonly. Direct reduction and stabilization of the fragment allow for more accurate restoration of the joint surface and are associated with a lower risk of secondary displacement compared to indirect fixation. Surgical treatment of posterior tibial margin fractures should rely on a precise CT scan-based diagnosis and careful assessment of fracture morphology. Direct visualization, anatomical reduction, and fixation of the fragment provide better clinical and functional outcomes and should be preferred in displaced or complex fractures.

Evaluation of calcium phosphate bone cement in augmenting screw hole defects in the ulna: A biomechanical study.

Effect of interspecies differences on the mechanical behavior of liver and a strain-rate dependent visco-hyperelastic constitutive model.

Statistical approaches for estimating forelimb ground reaction forces in foals during walking and trotting.

Background:A novel retropatellar tendon implant (LIFT) that is fixed deep to the patellar tendon proximal to the tibial tubercle may provide patellofemoral offloading benefits.Purpose/Hypothesis:The purpose of this study was to analyze the patellofemoral contact pressures from 0° to 60° of knee flexion in 3 states: (1) intact knee, (2) knee with the implantation of a retropatellar tendon implant, and (3) knee with a 45° anteromedialization tibial tubercle osteotomy (TTO). It was hypothesized that the implant would significantly reduce the contact pressure between the patella and trochlea compared with the intact state and produce a similar offloading effect as an anteromedializing TTO.Study Design:Controlled laboratory study.Methods:Trochlear pressure sensors were placed in 7 cadaveric knees (6 donors). Patellofemoral contact area, contact pressure, peak force, and center of force were measured using a model for native quadriceps force on the patella. On each specimen, measurements were taken in an intact state, after implantation of a novel retropatellar tendon implant, and after a 45° anteromedializing TTO. Force data were collected from 0° to 60° of flexion in 15° increments and normalized to each specimen's intact state.Results:Compared with the intact and implant groups, the TTO reduced the contact area at 30°, 45°, and 60° of flexion. TTO reduced contact pressure compared with intact from 15° to 60° of flexion, and reduced contact pressure at 15° when compared with the implant. The implant reduced the contact pressure compared with the intact state at 30° and 45° of flexion. For peak force, TTO reduced the force seen in 15° to 60° of flexion compared with the intact condition, while outperforming the implant at 15° of flexion. The implant reduced the peak force compared with the intact condition at 30° of flexion. Center of force analysis revealed that the implant medialized the center of force at 45° and 60° of flexion.Conclusion:The main finding from our biomechanical cadaveric study was that the novel retropatellar tendon implant did not reduce patellofemoral contact area, contact pressure, and peak force as much as a 45° anteromedializing TTO. The implant does reduce peak and contact pressures in early degrees of knee flexion compared with native states.Clinical Relevance:An implant that allows for offloading patellofemoral contact pressures without the morbidity, complication profile, or postoperative rehabilitation associated with a TTO may aid in the treatment of patellofemoral chondral lesions and retropatellar knee pain.

A biomechanical study comparing combined S1AI and S3AI trajectories to other pelvic fixation techniques: A finite element analysis.

This study aimed to construct a forelimb contracture model in rabbits to mechanically quantify pronation-supination movements during the healing phase following joint capsule and ligament injuries. Additionally, a finite element model of the human elbow joint was developed to investigate the mechanical environment of the elbow joint during pronation-supination movements in the healing phase. White rabbits were randomly assigned to either a control group (no injury) or an injury group (joint capsule and ligament injury). The injured forelimbs were immobilized for 2, 4, 6, and 8 weeks (designated as 2IM, 4IM, 6IM, 8IM groups, respectively), and mechanical tests were performed on the joints. A finite element model of the human elbow joint was utilized to simulate elbow joint protonation from 0° to 50° during different healing periods, and changes in soft tissue forces within the elbow joint were analyzed. During the healing phase, the injured group experienced significant reductions in total range of motion (ROM), with decreases of 26.8°, 43.8°, and 57.4° at 4 IM, 6 IM, and 8 IM, respectively. These reductions were accompanied by histological phenomena such as cellular adhesion within the joint capsule. Additionally, internal soft tissue stress gradually increased over time, with the highest stress observed in the annular ligament. Throughout the healing process, stress on the humeral cartilage consistently exceeded that on the ulnar cartilage, with the maximum stress reaching 15.8 times that of the ulnar cartilage. Stress on the joint capsule also increased progressively, rising by 69.5%, 87.5%, and 139.2% at 4, 6, and 8 weeks post-injury, respectively. Healing time is significantly negatively correlated with total joint range of motion, as evidenced by the continuous accumulation and transfer of internal soft tissue loading. These findings are associated with worsening histological changes within the joint capsule. These results are of great significance for further understanding the biomechanical environment within the joint cavity during elbow contracture and for guiding elbow contracture release surgery.

Immediate stability of a novel bidirectional expandable interbody device in an oblique lateral interbody fusion model: an in vitro biomechanical study

New design of plate implant for bone healing assessment using frequency measurement: a biomechanical cadaveric study

Medial plating versus newly designed intramedullary nail with distal interlocking system for distal tibia fractures: A biomechanical study with finite element analysis

This systematic review evaluates long-term outcomes after anterior cruciate ligament reconstruction (ACLR) with lateral extra-articular tenodesis (LET), including patient-reported outcome measures (PROMs), failure rates, objective knee scores and radiographic osteoarthritis (OA). A search of MEDLINE, Embase and Emcare was conducted until April 2025. Studies were eligible if they reported ≥10-year outcomes following combined ACLR and LET in adults. Exclusion criteria included cadaveric, biomechanical, paediatric and non-English studies. Methodological quality was assessed using Risk of Bias 2.0 Tool (RoB 2) for randomized trials and methodological index for non-randomized studies (MINORS) for non-randomized studies. Narrative synthesis and descriptive statistics were performed. Eleven studies (n = 603) were included, with a mean follow-up of 15.8 years (standard deviation [SD] 5.9). Graft failure rates ranged from 0% to 19.5%, with lower rates in studies using stricter revision-based definitions. LET was associated with lower failure and instability rates compared to isolated ACLR in three studies. Radiographic OA findings were mixed: some reported increased lateral OA (notably with bone-patellar tendon-bone [BTB] grafts), while others suggested protective effects, especially in patients with hamstring grafts and prior meniscectomy. Lysholm scores consistently exceeded 85, while Tegner activity levels declined modestly. International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) and Knee Injury and Osteoarthritis Outcome Score (KOOS) scores were favourable, and most patients achieved IKDC objective Grade A or B. This review demonstrated that ACLR augmented with LET provided durable long-term outcomes, including high rates of subjective satisfaction and objective stability, without being consistently associated with increased radiographic OA or unacceptable failure rates. However, heterogeneity in study design, surgical technique and outcome reporting limits definitive conclusions. Level IV.

Background/Objectives: In two-stage flexor tendon reconstruction, a biomechanically strong connection between the tendon graft, the motor unit, and the distal phalanx of the finger is essential to enable active rehabilitation after surgery. However, the available literature contains few biomechanical studies concerning the strength of this connection. In this study, we tested a new model of this connection involving suturing the tendon graft to the phalanx using an anchor and to the flexor digitorum profundus stump with a three-level continuous suture (palmaris longus—flexor digitorum profundus—anchor (PL-FDP-A)). Methods: For this study, we used eight fingers from patients with injuries that were unsuitable for replantation, as well as eight palmaris longus tendons harvested from cadavers. Eight specimens simulating the PL-FDP-A connections were prepared and tested on a tensile testing machine. The elongation of the specimens under a 20 N load (the minimum for active loading) and the force at rupture were assessed. Results: The mean rupture strength was 44.53 N (SD 16.27, min. 16.50, max. 64.60), with elongation at 20 N of 4.28 mm (SD 2.65, min. 1.49, max. 9.14). Conclusions: Based on our findings, we recommend the PL-FDP-A connection for use in two-stage flexor tendon reconstruction due to (1) rupture values which significantly exceeded the force required for active rehabilitation, and (2) minimal elongation at 20 N, so that motion transmission was not impaired.

ABSTRACT Kinesiology, as a major, is an interdisciplinary field with somewhat distinct areas of study. However, motor control/learning (MCL), and biomechanics (BIO-M) courses overlap considerably in their area of study, human movement. These courses are often taken later in an undergraduate curriculum plan of study as they have different pre-requisites. The purpose of the present study was to determine if the sequence in which MCL and BIO-M classes were taken influences student success in each course, as determined by final grades. We hypothesized that students would score better when the two classes were taken together. Data was included for 195 students that completed upper-level courses in both MCL and BIO-M for 6 continuous semesters, between the fall of 2022 and spring of 2025. Three course sequences were examined: 1.) BIO-M taken first, 2.) MCL taken first, 3.) courses taken together. The results showed that grades were slightly higher overall for the BIO-M class than the MCL class. Overall, grades were lower in both classes when the MCL course was taken first, despite both classes requiring higher-order thinking and learning, and the assessments being similar. The BIO-M class does provide more specific, individualized feedback early in the class, as well as a potential for re-taking the first exam. We posit that students are not used to free response assessments and that taking the BIO-M class first prepares them better for both classes.

In the domain of rock climbing research, existing biomechanical and physiological studies mostly focus on few, typically upper-body muscles and frequently do not replicate ecological conditions. This study investigates full-body muscle excitation and contact forces between climber and holds in two stationary climbing stances. Surface electromyography of 22 upper and lower-body muscles and contact forces between climber and holds were recorded in 14 climbers (6 males, 8 females; age 24 ± 6years; height 1.71 ± 0.07m; mass 64 ± 8kg; IRCRA 11-23). We recorded contact forces at three vertices of a rectangle: feet on the lower vertices, right hand on the upper right vertex. The protocol involved five repetitions of two 10-s positions (UP and DOWN) at three wall angles (SLAB: + 5°; VERTICAL: 0°; OVERHANG: -5). Root-mean-square values of electromyographic signals were determined for each repetition and scenario. A two-way RM-ANOVA assessed differences by wall angle and position. Steeper wall angles cause load transfer from feet to hand, homolateral in UP and contralateral in DOWN. DOWN position involves greater excitation of finger flexors muscles and brachioradialis at all wall angles, suggesting that preference for DOWN position in OVERHANG may not be simply explained by the degree of excitation of those muscles. This study provides a comprehensive mapping of full-body superficial muscle excitation and contact forces across two ecological climbing positions at different wall angles, helping to clarify climbing kinetics, inform targeted training and rehabilitation exercises, and optimize protocols for future research.