Repetitive loading of bone is associated with microdamage accumulation and material property degradation that may ultimately result in fatigue fracture. Our previous work used continuum damage mechanics (CDM)-based finite element (FE) modeling to predict stiffness loss and fatigue failure in whole bone; however, this model did not account for inter-specimen variability in fatigue behaviour and combined loading effects, which limited its applied efficacy. In this study, we refined the CDM-based FE model to predict experimental fatigue-life measurements from 21 whole rabbit tibiae subjected to cyclic compression with different magnitudes of superposed torsion. Machine learning (ML) methods were used to predict damage parameters from initial, undamaged, conditions, which were then used to predicted stiffness degradation and fatigue failure with the CDM-based FE modeling pipeline. Regression analysis was used to compare CDM-based FE fatigue-life predictions with experimental measurements. A random forest ML model predicted specimen-specific damage parameters with high accuracy (R2 = 0.85) and the CDM-based FE models demonstrated remarkable predictive capability, explaining up to 91% of the variance in fatigue-life measurements. Stiffness degradation profiles also followed a similar trend to experimental measurements; however, this agreement worsened with the level of superposed torsion suggesting additional refinements to the model may be necessary. These findings demonstrate the efficacy of integrating ML with CDM-based FE modeling to predict fatigue life and stiffness degradation. The observed agreement with experimental measurements suggests the modeling framework may provide valuable information regarding the mechanisms of fatigue fracture in whole bone.

As automated vehicle technologies enable increased seat recline angles during travel, understanding the biomechanics of injury under these novel occupant postures becomes imperative. This study evaluated the pelvis injury response and associated kinematics of reclined small female post-mortem human surrogates (PMHS) subjected to frontal sled tests across three restraint configurations. Each configuration varied in seat stiffness and the presence of a knee bolster to assess their influence on pelvic dynamics and submarining risk. Nine PMHS tests were conducted using a consistent reclined posture (38° thorax, 75-80° pelvis angle) and production restraint systems. Submarining probability was estimated using a validated logistic regression referenced from previous study. Distinct pelvic kinematics, fracture patterns, and associated injury mechanisms emerged across the test configurations in the current dataset. Configuration 1, featuring a stiffer seat without a knee bolster, exhibited complex pelvic fractures-most notably iliac wing fractures resulting from inward bending of the ilium-and a higher probability of submarining primarily due to rearward pelvic rotation. In contrast, Configuration 2, with a compliant seat and no knee bolster, produced comminuted iliac wing fractures, dominated by shear component and a moderate probability of submarining driven primarily by downward pelvic displacement. Configuration 3, which included a knee bolster, showed injury propagation to the posterior pelvis, and none of the subjects submarined. Each configuration included three specimens; therefore, results should be interpreted with caution. Despite the small sample size, the findings highlight the critical influence of seat stiffness and restraint design on pelvic kinematics and injury mechanisms under reclined conditions. The data provided could serve in validating computational models and anthropomorphic test devices (ATDs) in reclined seating configurations.

Cell culturing on soft substrates has become a widely applied method towards mimicking the compliant mechanical environment of cells in vivo, and substrate stiffness was shown to influence cell behavior. The cell-perceived stiffness, however, does not only depend on the modulus of the substrate material, but also on its thickness. In the present work, we propose an in silico approach to quantify the effect of substrate thickness on cell-perceived substrate stiffness. We coupled a discrete network representation of the cellular cytoskeleton including subcellular cell-substrate connections, i.e. focal adhesions (FA), with a continuum model of the substrate, and simulated the contraction of individual cells and cell patches. The results indicate that for substrates of heights larger than a multiple of the FA size (i.e. in the range of 5-10 μ m) the cell-perceived displacements and forces depend only on the substrate material, i.e. the latter is perceived as a semi-infinite continuum. The FA displacements depend more strongly on substrate thickness than FA forces. Based on the present model with subcellular resolution, the length scale of FAs emerges as the governing length scale for depth sensing, which is independent of the dimensions of the cells or cell patches.

Osteonecrosis of the femoral head (ONFH) is a progressive disorder characterized by regional trabecular bone deterioration that ultimately results in collapse. While elastic property changes in diseased bones are well documented, the contribution of region-specific viscoelastic behavior and its relationship to multiscale microarchitecture and composition remain insufficiently defined. Eighteen femoral heads (mean age: 40.8 ± 7.1 years; 15 males, 3 females; diagnosis: Ficat Stage III/IV) were retrieved during total hip arthroplasty. Patient-matched trabecular cores were harvested from three distinct zones: necrotic (NCZ), sclerotic (SCZ), and healthy (HZ). Bone quality was evaluated using micro-CT, uniaxial compression, nanoindentation, FTIR, and XRD. Viscoelasticity was characterized via stress relaxation and dynamic mechanical analysis (DMA) tests. The NCZ demonstrated microarchitectural decay (bone volume/total volume reduced by 54.54%, p < 0.001) and lower elastic modulus (reduced by 60.25%, p < 0.001) compared to SCZ. DMA revealed that while the NCZ exhibited the lowest storage modulus (E[']), it showed a trend toward greater matrix-dominated stress relaxation (~ 25% increase). Conversely, the SCZ exhibited a 60% increase in E['] (p < 0.01) but significantly reduced damping and post-yield energy than NCZ, consistent with a stiff yet brittle phenotype. Stress relaxation correlated strongly with mineral/matrix ratio (r = - 0.71) and collagen maturity (r = - 0.64), with collagen spectral markers significantly predicting microscale mechanical properties. ONFH induces profound viscoelastic and structural heterogeneity. This zonal mismatch between the compliant necrotic core and the stiff, brittle sclerotic rim likely promotes stress concentrations, driving structural instability and subchondral failure.

Transient hypertension precedes sustained hypertension and can arise from reduced aortic compliance with aging. We recently demonstrated that daily hypertension transients in swine rapidly lead to irreversible increases in left ventricular (LV) chamber stiffness without the development of anatomic hypertrophy (LVH). This dissociation was surprising and led us to hypothesize that the transcriptional response to pressure overload was determined by LV diastolic chamber stiffness. Myocardial tissue for RNASeq was obtained 24-hours after transient pressure elevation (LVEDP from 12.2±0.8 mmHg to 34.3±2 mmHg and LVSP from 105±3 mmHg to 223±8 mmHg) using phenylephrine. Animals with a single episode (SPO, n=6) were compared to those with daily repetitive pressure overload for 2-weeks (RPO, n=8). After RPO, LV diastolic chamber stiffness increased 4-fold (0.55±0.08 to 2.38±0.50 mmHg/mL/m[2] after RPO, p <0.01) and fibrosis increased (normal 5.7±0.2% to 12.9±1.8% after RPO, p <0.01) without the development of LVH (128±6.6 g/m[2] vs.129±3.6 g/m[2] after RPO, p-ns). There was a robust transcriptional response to SPO, with 5,885 of 12,483 genes (47%) differentially expressed (DEGs). These included potential determinants of chamber stiffness (extracellular matrix, fibrosis, and actin-cytoskeleton), hypertrophy and inflammation. In contrast, after 2-weeks of RPO, the transcriptional response to similar elevations in pressure was markedly attenuated with only 841 DEGs (7%). Our data indicate that LV chamber stiffness is a key determinant of the transcriptional response to pressure overload that attenuates hypertrophic gene expression. This may explain the wide variability of LVH among patients with a similar extent of pressure overload.

Gecko-inspired soft robots offer unique advantages for confined-space operations. Here, we introduce a soft climbing robot designed for tasks such as spacecraft inspection and disaster response. Unlike conventional attachment mechanisms relying on claws, suction-based adhesion, or electromagnetic components, the proposed system integrates polyurethane-based dry adhesive footpads, which passively adapt to a wide range of surfaces and require no external power. A key innovation of this work is the incorporation of variable stiffness footpads capable of actively tuning their mechanical properties in response to surface interaction demands, thereby optimizing both attachment stability and detachment efficiency during locomotion. Experimental characterization indicates that these footpads achieve an adhesion-to-detachment force ratio of 11:77, demonstrating a favorable balance between strong attachment and reliable release. Furthermore, the robot integrates a bioinspired crawling mechanism that synchronizes limb actuation with the deformation of a flexible spine structure, effectively enhancing propulsion and maneuverability across irregular terrain. Validation experiments conducted on diverse surface types confirm the robot's environmental adaptability and highlight its potential for deployment in constrained, unstructured, and dynamically changing operational contexts.

Knee osteoarthritis (OA) is a leading cause of chronic pain and disability. With projections indicating 642 million affected individuals globally by 2050, identifying safe, scalable, and potentially disease-modifying non-pharmacological interventions is an urgent public health priority. This study aims to compare the clinical effectiveness of Tai Chi, Baduanjin, and a health-education programme in preserving joint function and quality of life for patients with knee OA.

Ankylosing spondylitis (AS) and axial spondyloarthritis (axSpA) are chronic inflammatory diseases primarily affecting the axial skeleton. Increasing evidence indicates that their impact extends beyond the musculoskeletal system and includes clinically relevant cardiovascular involvement. Cardiovascular disease has become an important determinant of long-term outcomes in these patients, with growing evidence showing increased risks of myocardial infarction, stroke, atrial fibrillation, and other major adverse cardiovascular events. In addition to overt clinical events, subclinical vascular abnormalities, endothelial dysfunction, arterial stiffness, and structural cardiac changes are frequently observed. Cardiovascular injury in this setting arises from a complex interplay between traditional risk factors and persistent systemic inflammation. Inflammatory pathways involving tumor necrosis factor, interleukin-17, and interleukin-6 appear to promote endothelial activation, oxidative stress, lipid dysfunction, vascular remodeling, and atherosclerosis. Current evidence suggests that tumor necrosis factor inhibitors may provide cardiovascular benefit through improved control of inflammation, whereas the long-term cardiovascular effects of interleukin-17 inhibitors, non-steroidal anti-inflammatory drugs, and Janus kinase inhibitors remain incompletely defined. These findings support a more integrated clinical approach in AS/axSpA, combining disease control with cardiovascular risk assessment, modification of conventional risk factors, and ongoing cardiovascular surveillance.

While electroacupuncture (EA) alleviates pain in knee osteoarthritis (KOA), high-quality evidence from large trials is limited, and its potential to influence structural progression is unknown. We investigated whether EA confers structural benefits beyond symptom relief.