Introduction Canine elbow arthrodesis is a salvage procedure that reduces pain while preserving minimal limb function. Historically, plates have been applied to the caudal aspect, but recent techniques have introduced plate application to the lateral and medial aspects. However, biomechanical rigidity comparisons between these methods have not yet been conducted. Elbow arthrodesis involves difficulty in plate contouring. In this study, a custom plate model was designed, and 10 models were classified on the basis of plate position, plate length, and the presence of additional fixation to the radius. Finite element analysis was used to compare the rigidity of each model. Materials and methods A custom plate model was designed, and 10 finite element models were created based on CT data of a canine elbow. Models were categorized by plate position (caudal, medial, lateral), plate length (short vs. long), and the presence of additional radius fixation. An axial force of 150 N was applied to simulate loading, and peak von Mises stress and strain in the plate and bones (humerus, radius, ulna) were measured and compared across models. Results Medial plate application demonstrated the highest rigidity in the plate, followed by lateral and then caudal application. In bone evaluation, the humerus and ulna showed greater rigidity with medial application. Rigidity of both plate and bone models increased with longer plate length and with additional fixation to the radius. For the radius, lateral fixation provided the greatest rigidity among groups with radius fixation. Discussion Finite element analysis suggests that medial plate application provides superior biomechanical rigidity in canine elbow arthrodesis. Furthermore, utilizing a longer plate and incorporating additional fixation to the radius can enhance the overall biomechanical rigidity of the construct.

At present there are no validated numerical models of the frangible bones used in the Motorcyclist Anthropometric Test Device (MATD). This shortcoming limits the research on leg protectors. The purpose of the work was to build and validate FE models of femur and tibia frangible bones of the MATD, as defined in ISO13232. The bones were modelled using data from the ISO13232 and from observation of the components used in a full scale crash test conducted at IDIADA within the framework of the PIONEERS project. Their final design was identified with a design of experiments approach and validated against the requirements of ISO standard with the prescribed quasi-static and dynamic mechanical tests. The models were further assessed with a numerical–experimental comparison using the data of the full-scale crash test. The validated models enable the replacement of Hybrid III dummy bones and provide a reliable tool for improving the evaluation of lower-limb injuries in motorcycle crashes.

To evaluate whether optical coherence tomography (OCT) vibrometry can differentiate causes of conductive hearing loss (CHL) following ossiculoplasty, specifically distinguishing among effusion, soft-tissue fixation, and prosthesis disconnection. We simulated three post-surgical CHL conditions, effusion, soft-tissue fixation, and prosthesis disconnection, in a cadaveric temporal bone model (N = 10 per condition), with a partial ossicular replacement prosthesis (PORP) and cartilage graft implanted via a retrotympanic approach. A custom-built swept-source middle-ear OCT system (λ0 = 1550 nm, Δλ = 40 nm) was used to capture cross-sectional images and mobility measurements at the umbo and center of the cartilage graft across six stimulus frequencies (500, 750, 1000, 1500, 2000, and 3000 Hz). Mobility values (point velocity normalized to sound pressure) served as input features for a Random Forest classifier. Changes in mobility from baseline were also statistically analyzed. The classifier achieved 90.9% accuracy (40/44 datasets) in differentiating conditions in leave-one-out cross-validation, and 100% when trained on the full dataset. Simulated effusion and soft-tissue fixation were associated with broadband mobility decreases of 17.5 dB and 8.0 dB, respectively, averaged across both locations. Prosthesis disconnection at the stapes and at the tympanic membrane led to low-frequency (500 and 750 Hz) mobility increases of 9.9 dB and 11.1 dB, respectively, averaged across both locations. In a cadaveric model of post-surgical CHL, OCT vibrometry accurately distinguished effusion, soft-tissue fixation, and prosthesis disconnection. The ability to identify the cause of post-surgical CHL highlights OCT vibrometry's potential to assist clinical decision-making in revision surgery.

ABSTRACT The re‐association of skeletal remains has been one of the core challenges for anthropological studies of commingled skeletal elements. However, there has been a lack of methodologies focusing on the re‐association of fragmented remains. This work proposes a novel method for the screening of fragmented long bone diaphysis, based on the geometric properties of their 20% and 80% diaphyseal cross‐sections and utilizing support vector machine models. The sample consisted of 3D long bone models from 396 femora, 422 tibiae, and 415 humeri from the modern Athens Collection. The proposed algorithm was further evaluated on an archaeological and historical sample of Greek and British ancestry. The yielded true negative rate values on the reference sample were promising, ranging from 30% (femur) to over 60% (humerus sample). The total accuracy values, calculated for the top five most probable pairs, followed a similar trend (≈30% for humeri, ≈16% for femora). In all three bone sets, however, the rates were notably higher than the respective random expectation (calculated as 5 over the number of possible pairs). The evaluation on the archaeological and historical dataset showed that the algorithm performed generally better on the tibiae, while further examination of the results indicated that its performance differed based on the sample size. Based on these results, this approach has potential as a screening method for commingled assemblages, contributing to narrowing down the potential matches in larger assemblages. Furthermore, it fills the existing gap in literature, as there is a lack of similar methods in the field. However, further optimization and evaluation on different samples is important, as well as other follow‐up analyses.

Abstract Vat photopolymerization (VP)‐based bioprinting is rapidly emerging as a transformative platform for fabricating complex, cell‐laden tissue constructs with unparalleled spatial resolution and geometric precision. This review presents a comprehensive overview of recent advances in VP‐based bioprinting, organized around core themes of photopolymerization chemistry, printing modalities, bio‐ink design, and biomedical applications. We first describe the underlying crosslinking mechanisms including chain‐growth, step‐growth, redox‐mediated, and initiator‐free systems that enable spatiotemporal control over polymerization. The discussion then moves to key VP‐based bioprinting techniques such as stereolithography apparatus (SLA), digital light processing, two‐photon polymerization, and volumetric additive manufacturing, emphasizing their printing principles and suitability for bioprinting applications. A central focus is placed on the rational design of photo‐crosslinkable bio‐inks, comprising functional monomers, photo‐initiators (PIs), and photo‐absorbers (PAs). We critically examine design criteria such as cytocompatibility, rheological and optical behavior, mechanical performance, degradation profiles, and scalability, highlighting the complex trade‐offs between print fidelity and biological function. The utility of VP‐based bioprinting is further illustrated through its application in constructing advanced tissues, including bone, cardiac, cartilage, corneal, and hepatic models. Finally, we explore emerging frontiers such as multi‐material and multi‐modal bioprinting, machine learning‐guided optimization, and regulatory pathways toward clinical translation. Collectively, these insights outline a roadmap for advancing VP‐based bioprinting into a clinically viable, high‐throughput tissue engineering technology.

This study aimed to evaluate the effects of linear elastic vs. hyper-viscoelastic periodontal ligament (PDL) models and uniform vs. nonuniform alveolar bone models on dental biomechanics. Four teeth (incisor 31, canine 43, premolar 45, and molar 36) were subjected to 1 N of force in the distal, lingual, labial, and mesial directions, respectively. The simulations indicated that when the PDL was modeled as hyper-viscoelastic, maximum stress decreased by an average of 68.93%, whereas maximum strain increased by an average of 530.02%. This study quantified the effects of different material models on dental biomechanics and provides guidance for finite element modeling.

Modeling the mechanical anisotropy in the trabecular bone with the measurement and consideration of the structural anisotropy.

Refining near-infrared spectroscopy for collagen quantification: A new predictive model for archaeological bone

Permeability of bone and cartilage, and stiffness of collagen within cartilage, influence osteochondral fluid transport during cyclic compression: A study in finite elements.

Advances in wound ballistic research: Computed tomography analysis of projectile effects in simulants.

This study aimed to evaluate the safety of piezoelectric surgery for bone cutting during implant removal in terms of heat generation and histological changes. The bone model experiments involved titanium implants or non-metal dummy implants placed in bone models. Bone cutting using a piezoelectric surgery with irrigation was performed at distances of 0, 1, and 2mm from the implant, and the temperature was recorded using a contact thermometer placed at the tip of the implant. Using procine mandible models, histological analysis was performed using hematoxylin and eosin-stained images to evaluate the risk of thermal injury. When bone cutting was performed at distances of 0mm from the implants continuously, a significantly greater temperature increase was observed with the titanium implants compared to the non-metal dummy implants. The increase in temperature decreased as the distance between the implant and the cutting position increased. Comparing the cutting patterns, a greater temperature increase was observed with continuous and 10s intermittent cutting. In contrast, it was suppressed with intermittent cutting for 3 and 5s. In the histological analysis with porcine mandibles, findings suggest that thermal injury was not observed in any of the samples. No bone damage was observed in the histological analysis. In contrast, piezoelectric peri-implant bone cutting caused a significant increase in temperature, especially for continuous bone cutting during implant adjustments. However, intermittent cutting for 3 and 5s significantly suppressed the temperature increase. The results suggest that shortening the continuous cutting time may be effective in preventing heat generation when using piezoelectric surgery for peri-implant bone cutting.

The use of three-dimensional (3D) models, created using data obtained from radiological images, has significantly increased in recent years across the fields of medicine and health. The digitization of these models primarily utilizes open-source or commercial software. However, while the use of commercial software presents a significant economic burden, questions remain regarding model accuracy and output quality in open-source solutions. Therefore, this study aims to evaluate the morphometric accuracy of 3D radius models created using open-source medical software (InVesalius®, ITK-SNAP®, Seg3D®, and 3D Slicer®) by comparing them with gold standard (dry bone) measurements. Computed Tomography images of 15 dry human radius bones were used to generate the 3D digital models. These images were used to obtain 3D digital models via four different open-source software programs. Model lengths were calculated using MeshLab®, and volumes were calculated using Mimics® software. For gold standard comparison, the actual bone lengths were measured using digital calipers, and volumes were measured based on the Archimedes Principle.As a result, successful 3D digital radius models were created with all four programs. When the obtained measurements were compared with the gold standard values, no statistically significant difference was found between the programs (p > 0.05). Nevertheless, only the 3D Slicer® software demonstrated a high level of agreement in volume measurements (Cronbach's Alpha: 0.996; 95% CI: 0.988–0.999), standing out among the open-source medical software options.

Background and Objectives: To evaluate the association of surgeon experience, simulation-based training, and hand dominance on drilling accuracy using a synthetic bone model, with the hypothesis that training improves resident performance and left-handed individuals show superior bilateral accuracy. Materials and Methods: A prospective observational study was conducted in the Orthopedic Surgery Division of a tertiary academic center. Drilling accuracy was assessed before and after a standardized simulation-based training program. Twenty-five orthopedic surgeons participated: 9 junior residents (≤3 years of training), 8 senior residents (>3 years), and 8 board-certified experts. All participants completed baseline assessments; only residents were evaluated immediately after training and at a 2-week follow-up. Results: Experts showed superior baseline accuracy, particularly with the non-dominant hand. Senior residents showed a significant overall effect of time on right-hand accuracy (F(2,14) = 5.85, p = 0.014); post hoc pairwise comparisons showed trends toward improvement from baseline to post-training (p = 0.06) and from post-training to 2-week follow-up (p = 0.105); Junior residents showed no significant changes. Left-handed participants consistently outperformed right-handed peers with their non-dominant hands (p = 0.034). Among residents, this pattern persisted across all sessions. At baseline, senior residents and experts had similar right-hand accuracy (p = 0.59), but senior residents performed worse with the left hand (p = 0.038). No significant differences were found between junior and senior residents in either hand across all time points, indicating that residency duration alone does not improve performance without targeted training. Conclusions: Drilling accuracy in orthopedic surgery is influenced by experience level, targeted training, and hand dominance. Experts show greater precision, and senior residents showed a significant overall effect of time on right-hand accuracy, with trends toward improvement following training, while junior residents may need different training strategies. Tailored educational interventions are needed to improve accuracy and ambidexterity across all training stages. Level of evidence: II.

Segmental large-sized long bone defects remain a significant challenge in clinical practice. The standard treatment, involving autologous or allogeneic graft implantation, is often insufficient due to the limited availability of donor bone. As an alternative therapy for long bone defects, guided bone regeneration (GBR) presents a promising approach, effectively enhancing bone augmentation by preventing bone defects from soft tissue infiltration and facilitating osteoblast migration. This technique employs a biomaterial membrane as a protective barrier on the bone surface, promoting osteogenesis. This study proposed a GBR membrane designed specifically for long bone defects for fabrication. A photocurable hydrogel and light-processing 3D printing, based on 3D-scanned long bone models, were utilized to achieve fabrication. A mineralization-inducing compound was also incorporated into the material to enhance cell adhesion and osteogenesis. The 3D-printed GBR membranes demonstrated precise attachment to the long bone surface, confirming successful fabrication. The efficacy of the 3D-printed GBR membranes was evaluated in rabbit radius bone defect models.Graphic abstractSupplementary InformationThe online version contains supplementary material available at 10.1186/s12951-025-03963-1.

IntroductionEvaluation of hip kinematics commonly focuses on how much motion occurs at the joint, i.e., the range of motion (ROM). The helical axis of motion (HAM), comprised of an axis of rotation and a center of rotation (COR), is an alternative kinematics measure that describes how the motion occurs by accounting for the simultaneous rotations and translations. The aim of this analysis was to quantify side-to-side differences (SSD) and sex differences in hip HAM during gait so that “abnormal” symmetry can be identified in future studies of symptomatic individuals.Methods24 healthy young adults (13F, 11M; age 21.9±2.2 years) consented to be included in this IRB-approved study. Synchronized biplane radiographs were collected at 50 images per second during treadmill walking. Subject-specific bone models were created by segmenting CT scans of each participant’s femur and pelvis, and bone motion was determined by a validated volumetric model-based tracking technique that matched the CT-based bone models to the biplane radiographs with submillimeter accuracy. The HAM was calculated over every 3 degree increment of flexion/extension during the stance phase of gait. Outputs included the orientation of the HAM relative to the sagittal, transverse and coronal planes of the pelvis and the intersection of the HAM with the pelvic sagittal plane (the COR). Sex differences in HAM orientation were assessed using unpaired Student’s t-tests (α=0.05).Results109 walking trials were included in the analysis. No sex differences in the orientation of the HAM were identified (all <13.7±9.3°). The average SSD in HAM orientation across gait was 31.3±10.9° in the sagittal plane, 15.3±12.5° in the transverse plane, and 20.4±12.8° in the coronal plane. The average COR was located 2.6±1.6mm anteriorly, 2.6±1.8mm inferiorly, and 3.5±4.3mm lateral from the center of the acetabulum during extension; and 1.7±2.1mm anteriorly, 2.9±1.9mm inferiorly, and 2.1±4.9mm laterally during flexion.DiscussionOur results suggest there are no sex differences in HAM orientation in healthy individuals, however, considerable SSDs exist within an individual. The observed movement of the COR contradicts the assumption that the hip rotates about a fixed center of rotation during gait.

Virtual mechanical testing on image-based bone models (digital twins) provides subject-specific insights about the mechanical behavior of a bone during fracture healing. However, the established workflows for these tests are limited by reliance on commercial software and time-consuming manual procedures needed to create the digital twins. To overcome these barriers to clinical adoption and scalability, we have developed methods for user-independent and automated model generation. This study aimed to: (1) compare four competing methods for digital twin creation (two manual versus two automated approaches), (2) assess the influence of model-creation procedures and choice of material model (single- and dual-zone) on the virtual test results, and (3) evaluate the accuracy of the model-creation techniques through experimental validation of the results. Digital twins were generated from 59 CT scans (33 operated osteotomy fractures, 26 contralateral intact bones). Torsional rigidities were compared between modeling workflows and validated using postmortem physical mechanical test data. There were no significant differences in torsional rigidity between any of the four virtual testing groups and physical testing when a dual-zone material model was implemented for bone and callus. These results confirm that virtual mechanical testing is a reliable alternative to physical mechanical testing for assessing intact and healing long bones, with resilience to variations in digital twin creation methods. Automated model creation was substantially faster than the manual approaches, suggesting that automatic digital twin analysis is the pathway toward future clinical scalability.

IntroductionAcetabular dysplasia (AD) is defined as insufficient coverage of the femoral head by the acetabulum and results in instability of the hip joint. Periacetabular osteotomy (PAO) improves hip joint stability and function and is considered the gold standard for treatment of symptomatic AD. Although hip joint kinematics during activities of daily living (ADLs) have been investigated in asymptomatic young adults, hip kinematics in individuals with symptomatic AD before and after PAO remains elusive. The present study is an interim analysis of an ongoing study comparing hip kinematics before and after PAO in individuals with AD to hip kinematics in a healthy asymptomatic cohort.MethodsFour patients (4F, age 22.9±4.7 years) scheduled to undergo PAO to correct symptomatic AD were included in this IRB-approved study. A dataset of healthy control participants was used as a reference for this analysis, comprised of 24 asymptomatic adults (13F, 11M; age 21.9±2.2 years). Synchronized biplane radiographs were collected at 50 images/sec for 1 second during treadmill walking at a self-selected pace. CT scans were manually segmented to create subject-specific bone models for each hip. These models were then matched to the biplane radiographs by a validated volumetric model-based tracking technique to determine bone motion with submillimeter accuracy. Anatomic coordinate systems were placed in each right femur and hemi-pelvis and mirrored to the left side to produce identical coordinate systems for each hip. Translation of the center of the femoral head relative to the center of the acetabulum was calculated to dynamically measure hip instability, using the static standing position as a reference.ResultsAcross dysplastic hips during gait (n=4), the average magnitude of femoroacetabular translation was 1.3±0.7mm, with a minimum translation of 0.7±0.5mm and a maximum translation of 2.3±1.1mm. Among asymptomatic hips (n=47), the average magnitude of femoroacetabular translation was 1.0±0.6mm, with a minimum translation of 0.3±0.3mm and a maximum translation of 2.3±2.0mm.DiscussionThese interim findings suggest that dysplastic hips experience a range of dynamic translation comparable to that of healthy hips during gait.

IntroductionAbnormal morphology of the anteroinferior iliac spine (AIIS) can result in premature contact between the acetabulum and femur resulting in subspine impingement (SSI). Clinically, symptoms of SSI include decrease hip flexion, adduction, and internal rotation in flexion. Additionally, decreased femoral version, acetabular version (AV), and presence of cam lesions are associated with SSI. The purpose of this study was to quantify the subspine femoral space during activities of daily living and determine if a correlation exists between hip morphology and dynamic subspine space.Methods24 asymptomatic participants (11 men, 13 women; mean age 22±2 years) were enrolled in this study. Synchronized biplane radiographic images were collected at 50 images/sec during walking, squatting, and stair step-up. CT scans were manually segmented to create subject-specific bone models for each hip. These models were then matched to the biplane radiographs by a validated volumetric model-based tracking technique to determine bone motion with submillimeter accuracy. The AIIS and femoral neck were digitally marked to dynamically measure subspine femoral space. Morphological measurements were correlated with subspine femoral distance, and the effects of movement and sex on subspine femoral distance were calculated.ResultsThe average subspine femoral space while walking (22.0±3.2 mm) was significantly larger than during a squat (10.3±3.0 mm) and a step-up activity (10.5±1.8 mm) (p<0.001). Intertuberous distance, anterior head-neck offset (AHNO), and AV were positively correlated with subspine femoral space during stair step-up (p=0.003, p=0.039, p=0.049, respectively). AHNO, alpha angle, Tönnis angle, and McKibbin index were positively correlated with subspine femoral space during walking (p=0.010, p=0.034, p=0.024, p=0.049, respectively). Intertuberous distance was positively correlated with subspine femoral space during squat (p=0.031). Sex had no impact on subspine femoral space during any movement.DiscussionThe findings of the current study demonstrate that activities involving deeper hip flexion decrease the subspine femoral space over 50%, on average, compared to gait. Clinically, examination and imaging procedures of individuals presenting with symptoms consistent with SSI should include positions of deep flexion to evaluate for the presence of SSI. Morphologies associated with hip instability and impingement are positively associated with dynamic subspine femoral space.

Transcranial ultrasound stimulation (TUS) has emerged as a clinically validated neuromodulation technique. Particularly, phased array ultrasound can be applied in TUS to focus on the cortex or deep brain non-invasively, such as the ventral intermediate thalamic nucleus (VIM) and Precuneus (PCu) region for the treatment of essential tremor (ET) and Alzheimer Disease (AD). Current TUS treatment planning relies on computed tomography (CT)-derived skull porosity measurements, which involve patient radiation exposure and potential registration errors. This study proposes a Porosity Index (PI)-based method, derived from Ultrashort Echo Time (UTE) Magnetic Resonance (MR) images, for establishing skull acoustic models as a viable alternative, aiming to eliminate these limitations. Acoustic simulations using the K-Wave open-source platform were performed to validate the PI method's accuracy in predicting skull porosity and simulating focal distributions compared to CT. Focal spot characteristics were quantified using five metrics: peak intensity, target intensity, focal positioning error, Dice similarity coefficient, and Pearson correlation coefficient between CT- and PI-based simulation results. Statistical differences between these metrics were assessed using Tukey's multiple comparisons test. Quantitative comparisons against the gold-standard CT approach demonstrated comparable performance in peak focal intensity (deviation < 5%) and spatial pressure distribution patterns (Dice coefficient > 0.82). No significant differences (p > 0.05) were observed for any of the evaluated metrics. Our findings demonstrate that both the sound pressure distribution and prediction of the porosity are comparable with those from the reference CT. Using the PI to replace the traditional CT porosity has high feasibility and can achieve the purpose of reducing unnecessary radiation exposure and registration error for patients.

Introduction The incidence of pathological fracture of the radius at the site of a marginal defect following graft harvesting reaches 31 %. A finite element computer simulation model allows for non-invasive determination and prediction of the stress and strain (SS) of the bone, the strength and susceptibility to fracture under various loads and strengthening methods.The objective was to present the results of the finite element analysis on the influence of various marginal notch shapes, bone curvature and methods for increasing the strength on the SS of the radial shaft. Material and methods Based on anatomical preparations of the human radius, solid-state linear-elastic modeling of the entire cortical diaphysis of the radius was performed including the shaft with rectangular and triangular marginal notches, curvature in two planes using different reinforcing plates and fixation methods under non-destructive tensile, compressive, torsional and bending loads. The longitudinal stability of the bone was determined. ANSYS and NX Siemens software packages were used in the study. Results A triangular cutout reduced bone stress by 21.4 % in tension and by 51.5 % in torsion as compared to a rectangular cutout increasing the longitudinal stability margin by 1.18 times. Bi-planar bone curvature increased stress and reduced the tensile load-bearing capacity by 2.89 times. A 2 mm thick semi-tubular plate, compared to a flat narrow plate of similar thickness and 10 mm width reduced the level of maximum stresses in the bone model by 1.2–1.5 times in tension and by 3.5–3.9 times in torsion for different cutouts. Measurements of longitudinal stability for a semitubular plate increased critical stresses by 1.3–1.5 times for different osteotomies as compared to a bone without a cutout and plate. Discussion With all the loads, the strength conditions of the bone model with a cutout were provided when fixed with a plate at least 2 mm thick on four 2.0 mm bicortical screws inserted two distally and two proximally to the cutout. Conclusion The findings demonstrated practical use of bone plates reducing SS of the radius with any cutout.