Search Results (273)

Background/Objectives: Ankylosing Spinal Disorders (ASDs) encompass a heterogeneous group of rheumatic diseases characterized by progressive ankylosis of the axial skeleton, including Ankylosing Spondylitis (AS), Diffuse Idiopathic Skeletal Hyperostosis (DISH), and Non-Radiographic Axial Spondyloarthritis (nr-AxSpA). Spinal ankylosis profoundly alters the biomechanical properties of the vertebral column, transforming it into a rigid long-bone equivalent and dramatically increasing fracture risk even after low-energy trauma. Once a fracture occurs, the long lever arm created by the ankylosed segments generates enormous mechanical stress at the fracture site, making surgical stabilization mandatory in the vast majority of cases. Long posterior instrumentation is the treatment of choice; however, no consensus exists regarding the optimal number of instrumented levels. The aim of this study is to clinically and radiologically evaluate long posterior instrumentation in the 3 + 3 (3 proximal and 3 caudal screws), 3 + 2 (3 proximal and 2 caudal screws), or 2 + 2 (2 proximal and 2 caudal screws) configuration for the treatment of traumatic ASD thoracolumbar vertebral fractures, in terms of implant failure, infection rate, and mortality. Methods: Between 2018 and 2023, 65 consecutive patients with ASD-related thoracolumbar vertebral fractures were treated at our institution. After applying pre-defined inclusion and exclusion criteria, 37 patients were enrolled. Patients were retrospectively divided into three groups according to the posterior arthrodesis configuration (notation indicates number of instrumented vertebral levels proximal + distal to the fracture: 3 + 3, 3 + 2, or 2 + 2). Radiological outcomes were assessed for loosening, screw cut-out, and implant breakage. Infection and mortality rates within 3 months from surgery were evaluated as secondary endpoints. Statistical analysis was performed using the Fisher exact test (significance set at p < 0.05). Results: Thirty-seven patients (28 males and 9 females; mean age 77 ± 7.3 years) were included, with a mean follow-up of 30 ± 5.3 months. Instrumentation configurations were as follows: 23 (3 + 3), 5 (3 + 2), and 9 (2 + 2). Three implant failures (8.1%) and four infections (10.8%) were recorded. Eleven patients died within 3 months of surgery. A statistically significant difference was found between instrumentation length and mechanical complications (p = 0.0468), while no significant difference was observed for infection (p = 1) or mortality rate (p = 0.137). Conclusions: In this exploratory retrospective cohort, the 3 + 3 configuration was associated with the lowest observed rate of implant failure in ASD thoracolumbar fractures, suggesting a potential mechanical advantage over shorter constructs that warrants confirmation in larger prospective studies. No significant correlation was found between instrumentation length and infection rate or early mortality. Prospective, multicentre studies with larger cohorts are warranted to establish definitive guidelines for instrumentation length in this challenging patient population. Full article

Background: Osteochondral lesions of the talus (OLT) remain a challenging condition due to the limited regenerative potential of articular cartilage. Conventional bone marrow stimulation (BMS) techniques often result in fibrocartilage formation with inferior biomechanical properties. This study aimed to evaluate the safety and preliminary clinical efficacy of an arthroscopically assisted, single-stage injection of a heparin-conjugated fibrin hydrogel (HCFH) for OLT treatment. Methods: Twelve patients with symptomatic OLT underwent arthroscopic debridement, microfracturing, and HCFH injection containing autologous mesenchymal stromal cells (MSCs) and growth factors. Safety was assessed through systematic monitoring of adverse events (graded according to Common Terminology Criteria for Adverse Events criteria), wound healing, and serial laboratory inflammatory markers (leukocytes, erythrocyte sedimentation rate, C-reactive protein) during early and late follow-up. Clinical outcomes were evaluated using the Visual Analog Scale (VAS) and American Orthopedic Foot and Ankle Society score (AOFAS) preoperatively and at 6 and 12 months. Morphological assessment was performed using magnetic resonance imaging (MRI) with the modified Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) scoring system, evaluated independently by two blinded musculoskeletal radiologists. Results: No serious adverse events (Grade III–IV) were observed during the 12-month follow-up. All adverse events were mild (Grade I) and self-limited. A transient postoperative elevation in inflammatory markers was observed, returning to clinically acceptable levels by day 14. Significant improvements were noted in pain (VAS decreased from 6.0 to 2.0) and ankle function (AOFAS increased from 70.0 to 90.6) (p < 0.001). MRI demonstrated progressive morphological improvement, with the MOCART score increasing from 34.16 ± 17.1 at 6 months to 75 ± 5.43 at 12 months (p < 0.001). This increase corresponded with imaging features consistent with tissue maturation over time. The favorable MOCART outcomes observed in this study may be explained by the regenerative properties of heparin-conjugated fibrin hydrogels; however, larger randomized controlled trials with longer follow-up are needed to confirm the durability of the regenerated tissue. Interobserver agreement was substantial to almost perfect for MOCART scoring (κ = 0.68–0.84), with perfect agreement observed for surface assessment, bony defect/overgrowth, and cysts. Conclusions: Within the limitations of this study, single-stage HCFH injection demonstrated an acceptable safety profile and favorable preliminary clinical and radiological outcomes at 12 months. These findings suggest potential regenerative capability; however, controlled studies with larger cohorts and longer follow-up are required to determine comparative efficacy and long-term durability. Full article

Background: An exaggerated curve of Spee is a common finding in malocclusions with a deep overbite and requires correction to achieve functional occlusion and long-term stability. Leveling of the curve of Spee using continuous archwire mechanics generates complex force systems, the biomechanical effects of which depend on archwire material properties, cross-sectional dimensions, and the depth of the curvature being corrected. Quantitative data describing stress distribution within the teeth and periodontal ligament during this process remain limited. Objective: To evaluate and compare the stresses generated in the mandibular teeth and periodontal ligament during leveling of the curve of Spee using orthodontic archwires of different materials and dimensions through three-dimensional finite element analysis. Materials and Methods: A three-dimensional finite element model of the mandibular dentition, periodontal ligament, and supporting alveolar bone was constructed from computed tomography data. Orthodontic brackets and archwires of stainless steel, nickel–titanium, and titanium–molybdenum alloy were modeled in four dimensions: 0.014-inch, 0.016-inch, 0.016 × 0.022-inch, and 0.019 × 0.025-inch. Leveling of the curve of Spee was simulated at incremental depths ranging from 2 mm to 6 mm using displacement-controlled activation. Von Mises stresses generated within the teeth and periodontal ligament were recorded and compared across all simulations. Results: Stress magnitudes increased with increasing depth of the curve of Spee, larger archwire dimensions, and greater wire stiffness. Stainless steel archwires produced the highest stresses, followed by titanium–molybdenum alloy, while nickel–titanium archwires consistently generated the lowest stresses in both teeth and periodontal ligament. Conclusions: Archwire material and dimension significantly influence stress generation during leveling of the curve of Spee. Flexible archwires produce lower stress levels and may be advantageous during early correction of deeper curves. Full article

Background/Objectives: The development of high-performance biocompatible polymers such as zirconium-reinforced polyether ether ketone (BioHPP^®) has expanded the range of materials available for implant-supported prostheses, traditionally limited to metal alloys and zirconia. Due to its favorable mechanical properties and elastic modulus similar to cortical bone, BioHPP^® has been proposed as a potential alternative in implant prosthodontics. This systematic review aimed to analyze the biomechanical behavior of zirconium-reinforced PEEK and assess its advantages and limitations in implant prosthetic applications. Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines, including studies published between 2011 and 2025 that evaluated the performance of BioHPP in implant prosthetic applications. Results: The search strategy identified 34 studies that met the inclusion criteria. The included studies evaluated mechanical properties such as fracture resistance, elastic modulus, stress distribution, and peri-implant tissue response. Zirconium-reinforced PEEK demonstrated fracture resistance values reaching up to 1623.31 N and an elastic modulus of approximately 4 GPa, comparable to cortical bone. Several studies also reported favorable stress distribution patterns and reduced mechanical complications when compared with conventional metallic materials. Conclusions: Zirconium-reinforced PEEK exhibits promising biomechanical characteristics for use in implant-supported prostheses, particularly due to its fracture resistance and bone-like elastic modulus. However, the available evidence is predominantly based on in vitro and finite element studies. Long-term clinical trials are required to confirm its clinical performance and establish definitive recommendations for routine use. Full article

Objective: Effectively eliminating xenoimmunogenicity and achieving recellularization in cardiac xenografts remains a critical challenge in developing an ideal implantable xenograft. We have previously demonstrated that the removal of major antigens, including Galα1-3Gal (α-Gal) epitope and non-human sialic acid N-glycolylneuraminic acid (Neu5Gc), using α-galactosidase and peptide N-glycosidase F (PNGase-F), enables a synergistic effect with decellularization, significantly reducing the expression of carbohydrate-binding lectins without altering the biomechanical properties of the graft. The aim of this study was to establish an effective method for in vitro recellularization by seeding human mesenchymal stem cells (MSCs) on decellularized cardiac xenografts that had undergone optimal xenoantigen removal using α-galactosidase and PNGase-F. Additionally, this study aimed to evaluate the potential for in vivo recellularization. Methods: Decellularized porcine pericardium scaffolds treated with both enzymes were further modified by forming a fibrin mesh on their surface and within their structure, followed by the attachment of heparin and human vascular endothelial growth factor to the mesh. Subsequently, the scaffolds were seeded with human adipose tissue-derived stem cells for 8 weeks. In vitro recellularization, differentiation, and extracellular matrix remodeling of decellularized and enzyme-treated xenografts were assessed using vimentin, calponin, fibronectin, CD31, VWF, and phalloidin staining. To evaluate the potential for in vivo recellularization, decellularized glutaraldehyde-crosslinked xenografts with anticalcification treatments were seeded with rat bone marrow MSCs and implanted into rats subcutaneously to evaluate cell infiltration and calcification via histology, von Kossa staining, and micro-computed tomography. Results: In decellularized xenografts treated with both enzymes, stronger signals were detected and mesenchymal cell infiltration into the tissue was significantly faster, leading to accelerated recellularization. This recellularization process was more pronounced as time went on, with greater cell infiltration and evidence of cell differentiation. An in vivo study showed that decellularization and anticalcification treatments revealed stronger vimentin staining in histological analysis. The recellularization for our biocompatible scaffolds exhibited a lower degree of calcification compared to the non-recellularized tissue. Conclusions: We successfully developed major xenoantigen-free scaffolds by demonstrating the safety and synergistic effect of α-galactosidase and PNGase-F treatments and proved, for the first time, the effectiveness of recellularization using a human MSC monoculture on xenoantigen-free scaffolds. Furthermore, there was potential for in vivo recellularization of our biocompatible scaffolds seeded with MSCs. Full article

Aim: The aim of this study is to evaluate the effect of restorative crown materials with different elastic moduli on stress distribution in dentin and supporting tissues of pulpotomized primary anterior teeth under multi-directional loading conditions using the three-dimensional finite element analysis method. Materials and Methods: A three-dimensional model of a maxillary primary central incisor was created based on anatomical data. A clinical pulpotomy scenario was simulated using mineral trioxide aggregate (MTA) and resin-modified glass ionomer cement. Three models were analyzed: healthy tooth (control), Bioflx crown, and prefabricated zirconia crown. Frontal, oblique, and vertical loads were applied to represent functional and traumatic conditions. von Mises and principal stress distributions in the crown, dentin, and supporting tissues were evaluated. Results: In the prefabricated zirconia crown group, higher von Mises stress values were observed under all loading conditions, with significant stress concentrations particularly in the cervical region. In contrast, the Bioflx crown group exhibited lower stress values and a more homogeneous stress distribution. While the stress patterns in the Bioflx group were found to be closer to those of the control group, more localized stress accumulation was observed in the zirconia crowns. No significant differences were observed between the groups in the bone tissue. Conclusions: The elastic modulus of restorative materials plays a decisive role in the stress transfer mechanism. It is believed that materials with dentin-like mechanical properties may provide a more balanced and physiological stress distribution. Multi-directional loading analysis highlights the importance of evaluating the biomechanical behavior of restorative materials under more realistic conditions. Further advanced experimental and clinical studies are needed to clinically validate these findings. Full article

Bone fractures and keel bone damage as a result of osteoporotic implications on skeletal health due to high rates of egg production are of significant concern in the egg industry. This study was conducted to evaluate the effects of two aviary housing configurations and associated exercise opportunities on musculoskeletal health in laying hens. Two commercial aviary designs were compared: Big Dutchman NATURA STEP (STEP) and Big Dutchman NATURA 60 (N60). Musculoskeletal assessments were performed at 60 weeks of age (n = 180), where measurements included CT imaging and radiography, muscle dissections, tibial and humeral biomechanical properties, and bone ash percentage. Results indicated that hens in the STEP aviary exhibited higher tibial breaking strength, humeral stiffness, and heavier muscle groups compared to the N60 system. However, rates of new and old fractures, as well as rates of deviation, were more prevalent in STEP hens compared to N60 hens. These results indicate that housing system design influences musculoskeletal health in laying hens. Full article

Titanium and its alloys are used in dental and orthopedic implants. However, long-term stability remains a clinical challenge. To overcome this limitation, surface modification has been investigated to improve surface properties. Our previous study demonstrated that the immobilization of secretory leukocyte protease inhibitor (SLPI) on the titanium surface promotes osteoblast adhesion, proliferation, and differentiation in vitro. The current study demonstrated the first in vivo evaluation of SLPI as a bioactive coating for medical implants. Grade 5 titanium screws were coated with 10 µg/mL of recombinant human SLPI (rhSLPI) for 24 h via simple physical adsorption, and the results were preliminarily validated via FE-SEM and ELISA. These SLPI-coated titanium screws (TiSs) were then placed in the tibia of Sprague–Dawley rats for 4 and 8 weeks. The hematological and biochemical parameters (BUN, Creatinine, AST, and Troponin I) demonstrated no acute systemic alterations within the 8-week period across all groups. Moreover, micro-computed tomography (micro-CT) and histological analysis revealed significantly higher bone volume fraction (%BV/TV) at 4 weeks compared to uncoated controls (20.64% ± 2.452% vs. 11.73% ± 0.524%). Finally, the biomechanical stability of implants, assessed using the removal torque test, showed that TiSs showed higher strength compared to Ti at both 4 and 8 weeks. In conclusion, this study represents a novel approach to transitioning rhSLPI-coated titanium evaluation from in vitro models to an in vivo rat model. rhSLPI surface functionalization enhances early-stage osseointegration and improves implant mechanical stability without acute hematological and biochemical alterations. These proof-of-concept findings suggest the potential of SLPI as a bioactive coating strategy. Full article

Quercetin (QE) is a widely distributed dietary flavonol with antioxidant and anti-inflammatory properties that has attracted interest as a modulator of bone remodeling and osteoporosis-related bone loss. In vitro data on osteoblasts, osteoclasts, and mesenchymal stem cells indicate that QE attenuates oxidative stress, suppresses pro-inflammatory signaling, and promotes osteogenic differentiation through modulation of pathways such as Nrf2/ARE, NF-κB, Wnt/β-catenin, and ER stress-related cascades. In vivo findings from animal models of estrogen deficiency, diabetes, and glucocorticoid-induced osteoporosis demonstrate that QE improves bone mineral density, trabecular microarchitecture, and biomechanical strength while reducing osteoclast number and activity, thereby attenuating osteoporotic bone deterioration. Collectively, preclinical evidence positions QE as a pleiotropic agent promoting osteoblastogenesis, inhibiting osteoclastogenesis, and balancing redox/inflammatory homeostasis in bone, despite bioavailability challenges. Future research should prioritize clinical trials with optimized formulations (e.g., nanoparticles) to validate efficacy, safety, and fracture outcomes in humans. The present review critically evaluates the chemical characteristics, pharmacokinetics, safety profile, and bone-targeted biological activity of QE, emphasizing effects on bone cells and skeletal metabolism. Full article

Objective: To evaluate the biomechanical effects of varying posterior implant inclinations and loading protocols on peri-implant stress distribution in full-arch maxillary rehabilitations using the All-on-Four concept. Methodology: A three-dimensional finite element model of an edentulous atrophic maxilla was developed from a digital point cloud. Four implants were placed according to the All-on-Four protocol: two anterior vertical implants and two posterior implants with inclinations of 0°, 15°, 30°, or 45°. Mini-abutments and a titanium bar prosthesis were included. Material properties were assumed as homogeneous, isotropic, and linearly elastic. Immediate loading was simulated using frictional contacts (µ = 0.3), whereas delayed loading assumed complete osseointegration (bonded contacts). The models were meshed using 10-node quadratic tetrahedral elements (SOLID187) in ANSYS^®. Maximum von Mises stress in cortical bone, cancellous bone, implants, abutments, and the prosthetic bar was assessed. Results: Posterior implant tilt significantly reduced peri-implant stress. Under immediate loading, the highest stress occurred at 0° inclination in the posterior left implant (82.36 MPa) and decreased progressively with increasing tilt, reaching 33.63 MPa at 45° (≈59% reduction). Delayed loading generally produces lower stress magnitudes, particularly at extreme tilts. Anterior implants experienced lower stress levels across all configurations. Comparative analysis demonstrated that immediate loading increased stress at lower angulations, while differences between loading protocols were minimal at higher inclinations. Conclusions: Posterior implant angulation and loading protocol critically influence peri-implant stress distribution. Increased posterior tilt combined with appropriate loading reduces peak cortical bone stresses, supporting biomechanical optimization in All-on-Four maxillary rehabilitations. Full article

(1) Background: Dental implant instability represents a dynamic biomechanical process influenced by functional loading, peri-implant bone stiffness, and systemic conditions affecting bone metabolism. In patients with systemic bone disorders, altered material properties and impaired remodeling may reduce effective implant–bone interface stiffness, potentially increasing micromotion beyond what is detectable by conventional clinical indicators. The aim of this study was to develop and evaluate a predictive bioengineering model of implant instability based on Periotest-derived dynamic measurements. (2) Methods: A retrospective analysis was performed on 79 dental implants placed in patients with and without systemic bone disorders. Implant micromotion was quantified using Periotest values (PTVs). Linear and logistic regression analyses were applied to model the relationship between systemic bone status, implant location, and biomechanical instability (defined as PTV > +2.0). A load–stiffness–micromotion framework was used to provide mechanical interpretation of the findings. (3) Results: Implants placed in patients with systemic bone disorders exhibited significantly higher Periotest values compared to controls (+2.1 ± 1.3 vs. −0.4 ± 1.1; mean difference 2.5 PTV units, 95% CI 1.97–3.04; p < 0.001). High-risk biomechanical instability (PTV > +2.0) was observed in 46% of implants in the systemic group compared to 9% in controls. Multivariable logistic regression demonstrated that systemic bone disorders were independently associated with a 2.6-fold increase in the odds of high-risk instability after adjustment for implant location. The observed instability pattern was consistent with reduced effective peri-implant stiffness in systemically compromised bone. (4) Conclusions: Dental implant instability in systemically compromised patients can be interpreted as a load–stiffness imbalance at the implant–bone interface. The proposed predictive bioengineering framework links dynamic Periotest measurements with mechanical modeling and systemic bone status, enabling quantitative risk stratification beyond static stability assessments. Full article

Composite bone replicas are widely used in biomechanical testing as alternatives to cadaveric specimens, with numerical models often complementing or replacing experiments. The reliability of these models depends strongly on accurate material parameters. This study investigates a fourth-generation Sawbones composite L5 vertebra, updating cortical material properties under isotropic and transversely isotropic modelling assumptions. Finite element models were calibrated using free-free experimental modal analysis, revealing differences between manufacturer-provided material properties and the measured specimen behaviour. For both models, matching the specimen mass required reducing the cortical density from 1.64 g/cm³ to 1.423 g/cm³. In the isotropic model, the Young’s modulus was reduced from 16,000 MPa to 6500 MPa. In the transversely isotropic model, longitudinal and transverse Young’s moduli were reduced from 16,000 MPa and 11,000 MPa to 6400 MPa and 5500 MPa, respectively, while the shear moduli decreased from 4370 MPa and 6350 MPa to 3500 MPa and 2540 MPa. In both models, the Poisson’s ratio was increased from 0.26 to 0.30. These updates reduced the average eigenfrequency error to 6.12% (isotropic) and 5.83% (transversely isotropic), with the first five modes errors reduced to 3.10% and 2.80%, respectively, substantially improving numerical representation of L5 vertebral mechanics. The updated vertebral FE model and accompanying workflow enhance the reliability of future FE analyses, improve interpretation of Sawbones vertebra biomechanical results, and support vibration-based biomechanical applications such as implant fixation assessment. Full article

Understanding how primary structural features and secondary material properties adapt to functional loads is essential to determining their effect on changes in joint biomechanics over time. The objective of this study was to map and correlate spatiotemporal changes in primary structural features, secondary material properties, and dentoalveolar joint (DAJ) stiffness with age in rats subjected to prolonged chewing of soft foods versus hard foods. To probe how loading history shapes the balance between the primary and secondary features, four-week-old rats were fed either a hard-food (HF, N = 25) or soft-food (SF, N = 25) diet for 4, 12, 16, and 20 weeks, and functional imaging of intact mandibular DAJs was performed at 8, 12, 16, 20, and 24 weeks. Across this time course, the primary structural determinants of joint function (periodontal ligament (PDL) space, contact area, and alveolar bone socket morphology) and secondary material and microstructural determinants (tissue-level stiffness encoded by bone and cementum volume fractions, pore architecture, and bone microarchitecture) were quantified. As the joints matured, bone and cementum volume fractions increased in both the HF and SF groups but along significantly different trajectories, and these changes correlated with a pronounced decrease in PDL-space from 12 to 16 weeks in both diets. With further aging, older HF rats maintained significantly wider PDL-spaces than SF rats. These evolving physical features were accompanied by an age-dependent significant increase in the contact ratio in the SF group. The DAJ stiffness was significantly greater in SF than HF animals at younger ages, indicating that food hardness-dependent remodeling alters the relative contribution of structural versus material factors to joint function across the life course. At the tissue level, volumetric strains, representing overall volume changes, and von Mises bone strains, representing shape changes, increased with age in HF and SF joints, with volumetric strain rising rapidly from 16 to 20 weeks and von Mises strain increasing sharply from 12 to 16 weeks. Bone in SF animals exhibited higher and more variable strain values than age-matched HF bone, and changes in joint space, degrees of freedom, contact area, and bone strain correlated with joint biomechanics, demonstrating that multiscale functional biomechanics, including bone strain in intact DAJs, are colocalized with anatomy-specific physical effectors. Together, these spatiotemporal shifts in primary (structure/form), and secondary features (material properties and microarchitecture) define divergent mechanobiological pathways for the DAJ and suggest that altered loading histories can bias joints toward early maladaptation and potential degeneration. Full article

Bone tissue engineering, as an important branch of regenerative medicine, integrates multidisciplinary knowledge from cell biology, materials science, and biomechanics, aiming to develop novel biomaterials and technologies for functional repair and regeneration of bone tissue. Hydrogels are among the most commonly used scaffold materials; however, conventional hydrogels exhibit significant limitations in physical properties such as strength, tensile strength, toughness, and fatigue resistance, which severely restrict their application in load-bearing bone defect repair. As a result, the development of high-strength hydrogels has become a research hotspot in the field of bone tissue engineering. This paper systematically reviews the latest research progress in this area: First, it delves into the physicochemical characteristics of high-strength hydrogels at the molecular level, focusing on core features such as their crosslinking network structure, dynamic bonding mechanisms, and energy dissipation principles. Next, it categorically summarizes novel high-strength hydrogel systems and different types of biomimetic hydrogels developed based on various reinforcement strategies. Furthermore, it provides a detailed evaluation of the application effects of these advanced materials in specific anatomical sites, including cranial reconstruction, femoral repair, alveolar bone regeneration, and articular cartilage repair. This review aims to provide systematic theoretical guidance and technical references for the basic research and clinical translation of high-strength hydrogels in bone tissue engineering, promoting the effective translation of this field from laboratory research to clinical application. Full article

Osteoarthritis (OA) is a progressive degenerative joint disease that fundamentally alters the mechanical environment of the knee. This study utilizes a finite element framework to evaluate the biomechanical response of the distal femur in healthy and osteoarthritic conditions across critical functional postures. To isolate the bone’s inherent structural stiffness and avoid numerical artifacts, a free-body computational approach was implemented, omitting external surface fixations. The distal femur was modeled as a linearly elastic domain with material properties representing healthy tissue and OA-induced degradation. Simulations were performed under passive gravitational loading at knee flexion angles of $0^{\circ },{60}^{\circ },$ and ${90}^{\circ }$. The results demonstrate that the mechanical response is highly sensitive to postural orientation, with peak von Mises stress consistently occurring at ${60}^{\circ }$ of flexion for both models. Quantitative analysis revealed that the stiffer Normal bone attracted significantly higher internal stress, with a reduction of over 30% in peak stress magnitude observed in the OA model at the most critical flexion angle. Total displacement magnitudes remained relatively stable across conditions, suggesting that OA-induced material softening primarily influences internal stress redistribution rather than global structural sag under passive loads. These findings provide a quantitative index of skeletal vulnerability, supporting the development of patient-specific orthopedic treatments and rehabilitation strategies. Full article