Journal of Biomechanical Engineering

Adolescent idiopathic scoliosis (AIS) alters spinal geometry and may influence the biomechanical response of the spine during functional postures. However, posture-dependent changes in spinal loading and paraspinal muscle forces in AIS remain poorly understood. This study investigated the effects of trunk posture on intervertebral loading and paraspinal muscle forces using a subject-specific musculoskeletal model of an adolescent with AIS. The spinal deformity was reconstructed from biplanar radiographs and incorporated into a full-body musculoskeletal model. Flexion, extension, lateral bending, and axial rotation were simulated at three incremental magnitudes, with motion distributed across the thoracolumbar spine. Intervertebral compressive and lateral forces around the curve apex and forces in the erector spinae (ES) and multifidus (MF) muscles were evaluated. Trunk flexion produced the greatest compressive loading, reaching 337 N at the curve apex and 372 N two levels below the apex at 30{degrees} flexion. Lateral bending produced pronounced direction-dependent loading: concave-side bending increased lateral forces, whereas convex-side bending increased compressive forces. Axial rotation produced similar but smaller direction-dependent changes. Paraspinal muscle forces were consistently asymmetric, with concave-side dominance of the ES and convex-side dominance of the MF. Flexion and convex-sided movements generally produced greater muscle imbalance, while increasing posture magnitude amplified spinal loading and muscle forces. These findings demonstrate that trunk posture, movement direction, and magnitude substantially influence the biomechanical environment of the scoliotic spine and should be considered when evaluating spinal mechanics in AIS.

Purpose: Fibrotic remodeling of the uterus, associated with aging, disease, and environmental exposures, alters collagen organization and tissue stiffness, yet how these changes influence organ-level mechanical behavior remains poorly understood. Glutaraldehyde (GA)-induced collagen crosslinking was used as a controlled surrogate for fibrotic remodeling to determine whether image-informed inverse finite element analysis (iFEA), combined with inflation testing and micro-computed tomography (microCT), could detect and quantify the resulting changes in uterine constitutive behavior. Methods: Murine uteri (n = 6 untreated, n = 6 GA-crosslinked) underwent volume-controlled balloon inflation with simultaneous microCT imaging to quantify deformation of the inner and outer wall boundaries for iFEA. Specimen-specific Gasser-Ogden-Holzapfel (GOH) finite element models were optimized by adjusting model parameters to reproduce experimentally measured wall contours throughout inflation. Model performance was evaluated using contour root mean square error (RMSE), and parameter identifiability was assessed through sensitivity analyses. Results: GA treatment significantly increased inflation work, linear stiffness, and maximum inflation resistance (p < 0.001). The iFEA framework accurately reproduced experimental deformation (RMSE < 3%) and revealed significant increases in the estimated GOH parameters C10 (9.2-fold), k1 (2.0-fold), and k2 (2.7-fold), consistent with increased effective tissue stiffness and a shift toward earlier collagen fiber recruitment. Sensitivity analyses demonstrated unique, well-defined minima for all parameter combinations. Conclusion: Image-informed iFEA provides a quantitative framework for relating collagen remodeling to organ-level uterine mechanics through specimen-specific constitutive parameter estimation. This approach establishes a foundation for investigating the mechanical consequences of uterine fibrosis and other remodeling processes.

ObjectiveThis study investigates knee joint biomechanics during lunges under varying tibial angles and external loads using musculoskeletal modeling and finite element analysis. The goal is to provide a biomechanical basis for understanding knee loading patterns and optimizing sports training and rehabilitation. MethodsTwenty-six healthy young men performed lunges under tibial inclination angles relative to the ground (60{degrees} and 90{degrees}) and two external load conditions (bodyweight and an additional 98 N external load). Kinematic and kinetic data were captured using motion capture and force plates. Musculoskeletal models were used to estimate joint moments, range of motion, and stiffness, with data analyzed using two-way repeated-measures ANOVA. Finite element analysis was performed at 90{degrees} tibial angle to evaluate tissue stress and displacement. ResultsThe joint moment at a 60{degrees} tibial angle was much higher than at a 90{degrees}. External load showed significant effects on knee stiffness, with lower rotational stiffness in the horizontal plane (P < 0.001) and lower coronal plane stiffness at 90{degrees} (P = 0.012) under the 98 N external-load condition, indicating reduced resistance to angular displacement in these planes. Under the 90{degrees} tibial-angle condition with external load, peak stress and displacement were concentrated in the posterior horn of the meniscus, with a maximum displacement of 3.12 mm. ConclusionThe anterior tilt of the tibia increased sagittal-plane knee loading, while external load mainly reduced joint stiffness in the coronal and horizontal planes. Under the 90{degrees} loaded condition, the concentration of stress and displacement in the posterior horn of the meniscus suggests a mechanically unfavorable loading pattern rather than direct evidence of injury risk. These findings may provide useful biomechanical information for load management during lunge-based training and rehabilitation.

Classical neuronal cable theory relies on quasi-static electric field approximations and neglects magnetic induction, Lorentz force coupling, and transient electromagnetic currents, limiting its ability to fully characterize action potential propagation within geometrically branched axons and dendrites. This work develops a coupled Maxwell-electromagnetic cable framework by integrating finite-difference time-domain (FDTD) solutions of Maxwells equations with extended Hodgkin-Huxley and Fitzhugh-Nagumo membrane dynamics, incorporating magnetic gating perturbations, electromagnetic trans-membrane currents IEM, and nanoscale quantum corrections for thin neural segments. Controlled propagation experiments are designed to quantify deviations from standard cable predictions across asymmetric and symmetric axonal bifurcation geometries. Numerical results demonstrate that inductive magnetic effects lower the critical branch radius for junction conduction failure and break symmetric action potential invasion in geometrically identical child branches under external transverse magnetic fields. An electromagnetic corrected geometric ratio GREM is proposed to revise impedance-matching conditions at branch points, accounting for size-dependent axial current imbalance induced by magnetic and displacement currents. Parent axon conduction velocity deviates substantially from the canonical [Formula] scaling law when electromagnetic feedback and quantum charge distributions are included, triggering early signal blockage at large cable diameters. Collectively, this study establishes that quasi-static cable models underestimate electromagnetic corrections to propagation speed, waveform shape, and bifurcation transmission fidelity; the coupled Maxwell-cable framework provides a comprehensive multi-physics tool for modeling electrodynamic signal behavior in complex neuronal architectures.

The relationship between external forces and bone strain in running is often complex and nonintuitive. We used Groucho running (i.e., running with exaggerated knee flexion) as a model to dramatically reduce the vertical ground reaction force (VGRF) and examined the relationship between peak VGRF and finite element (FE)-predicted tibia-fibula bone strain. Nine physically active males ran on an instrumented treadmill at 2.8 m/s with their preferred running technique, increased knee flexion (Groucho), and exaggerated knee flexion (Ex Groucho) in a randomized order. Strains at the tibia-fibula midshaft were calculated using computed-tomography-based FE modeling with loads and boundary conditions calculated from an inverse-dynamics based musculoskeletal model. Pressure-modified von Mises strain was used to quantify the peak strain (90th percentile strain) and strained volume (volume of bone experiencing strains above 3000 {micro}{varepsilon}). We further explored the relationship between peak VGRF, lower leg angle, and FE-predicted strain variables. The results showed that a 15.8% and 22.9% reduction in VGRF during Groucho and Ex Groucho, respectively, had no significant effect on FE-predicted peak strain (p > 0.304) and strained volume (p>0.053). Changes in peak VGRF did not correlate with FE-predicted strain variables (p>0.54) while changes in lower leg angle in the sagittal plane were moderately correlated (r>0.65; p<0.047). Our findings suggest that reductions in peak external forces do not always coincide with reductions in bone strain, especially in cases where running kinematics are dramatically altered. This work has important implications for designing gait retraining interventions based on reductions in external force measures.

Ankle stiffness is decreased during movement compared to posture; however, the etiology of this decrease remains unknown. Determining what gives rise to this decrease is critical for understanding how humans successfully interact with their physical world and how that ability is compromised by functional impairments. While the triceps surae and Achilles tendon primarily dictate ankle stiffness, the relative contributions across posture and movement remain unknown. Therefore, our study sought to quantify the relative contributions of the muscle and tendon to ankle stiffness and how those contributions differ between posture and movement. We used our technique, which combines B-mode ultrasound imaging with joint-level perturbations, to quantify ankle, muscle, and tendon stiffness simultaneously. Since ankle, muscle, and tendon stiffness all scale with torque, participants matched torque between posture and movement tasks. During posture, the Achilles tendon is the dominant contributor to ankle stiffness. However, during movement, the triceps surae and Achilles tendon contribute more equally to ankle stiffness, which can be attributed to a significant decrease in muscle stiffness during movement. Here, we provide the first empirical data on how state-dependent properties of the triceps surae and Achilles tendon contribute to ankle stiffness in conditions relevant to locomotion.

This study aimed to (1) develop an elasticity framework for the sprint force-velocity (F-V) relationship and (2) examine how maximal force (F_{0}), maximal velocity (v_{0}), and sprint distance modulate the four derived elasticity metrics, and (3) explore these elasticity metrics' interrelation. After modelling the F-V relationship differential equation, four elasticity metrics were defined as force elasticity (F_{e}), the elasticity of sprint time to F_{0}; velocity elasticity (v_{e}), the elasticity of sprint time to v_{0}; the force-velocity elasticity norm {(\mathrm{F}-\mathrm{V}}_{\mathrm{EN}}=\sqrt{F_{e}^{2}+v_{e}^{2}}), capturing the combined sprint time sensitivity to proportional changes in F_{0} and v_{0}; and the force-velocity elasticity ratio {(\mathrm{F}-\mathrm{V}}_{\mathrm{ER}}=F_{e}{\div v}_{e}), indicating which variable dominates the sprint time response. Model simulations showed that F_{e} decreased with rising F_{0} and increased with rising v_{0}, while v_{e} showed the opposite pattern. With increasing sprint distance, F_{e} decreased and v_{e} increased. Given its negligible effect on sprint time, ignoring air resistance yields a conservation law (2F_{e}+v_{e}\equiv 1), indicating that a gain in one elasticity metric necessarily diminishes the other in a fixed proportion. This framework also identifies a valley distance (d_{valley}) at {\mathrm{F}-\mathrm{V}}_{\mathrm{ER}}=2, where {\mathrm{F}-\mathrm{V}}_{\mathrm{EN}} is minimized (\sqrt{0.2}) and sprint time is least responsive to changes in F-V relationship variables. Empirical data confirmed that the two theoretical laws still hold approximately when air resistance is considered. By linking changes in F_{0} and v_{0} to sprint time across different distances, the elasticity framework provides a quantitative basis for estimating the theoretical sprint time response to documented changes in F-V relationship variables.

BackgroundCardiovascular disease risk is higher in men than in women. Although sex differences in aortic wall adaptation following antihypertensive treatment have been reported in acute hypertension models, the response after gradually developing hypertension, which mimics human essential hypertension, remains unclear. This study investigated sex differences in aortic wall adaptation following acute blood pressure reduction after gradually developing hypertension. MethodSeventeen-week-old spontaneously hypertensive rats (SHRs) were assigned to the Hypertensive group or the antihypertensive (Reversal) group (N = 5/sex each). The Reversal group received the antihypertensive drug captopril for 4 weeks to maintain systolic blood pressure below 130 mmHg. Age-matched Wistar Kyoto rats (N = 3/sex) served as normotensive (Normal) group. After the experimental period, arterial wall thickness, circumferential wall stress, smooth muscle cell phenotype, and histological changes were evaluated. ResultsAntihypertensive treatment significantly reduced systolic blood pressure in both sexes. Both male and female SHRs exhibited elevated circumferential wall stress during the gradual development of hypertension. In females, antihypertensive treatment significantly reduced medial thickness compared with the Hypertensive group, whereas males showed no reduction. Circumferential wall stress in female Reversal group did not differ significantly from either the Hypertensive or Normal group, whereas males exhibited a significant reduction in circumferential wall stress compared with the Hypertensive group. Furthermore, the reduced collagen area fraction in the Hypertensive group returned to the normotensive levels only in females following antihypertensive treatment. ConclusionThese findings indicate that vascular remodeling induced by gradually developing hypertension is more effectively reversed by antihypertensive treatment in females than in males.

The foreign body response (FBR) is an immune mediated event that occurs with every material implant. The extent of the fibrosis is dependent on many factors including the biomaterial design, tissue location, and host factors such as age, sex, ancestry, diet. There are known clinical outcomes of implants dependent on age and sex, including increased fibrosis and implant failure in aged and female patients. As the population ages, there is a growing need to understand how aging affects the FBR, and how preclinical models can capture this to guide biomaterial design. Here, we investigated how chronic fibrosis in a murine model of the FBR is altered by two biological factors: age and sex. We investigated changes in fibrosis using a volumetric muscle loss (VML) injury model coupled with polycaprolactone (PCL) or polyethylene (PE) microparticle implants. Fibrosis was quantified through gene expression, microscopic analysis of histologic sections, and the corresponding immune response measured via gene expression and flow cytometry data. We found gene expression differences with immune pathways enriched in female mice, and microscopy revealed collagen birefringence area increased in young male mice. Both the innate and adaptive immune response were altered by age and sex via T cell and macrophage phenotype, and the effects of aging differed between sexes. These results reveal both variables contribute to discrepant outcomes in both fibrosis and the local immune response to synthetic material implants. This demonstrates a clear need to understand and account for the influence of biological factors in biomaterial design.

Most widely used lower-limb musculoskeletal models are derived from male anatomy and adapted to female participants solely by linear scaling, which may not capture sex-specific differences in pelvic and hip geometry. We developed a population-averaged, female lower-limb musculoskeletal model, built from MRI-based models of a cohort of 25 adult women using thin-plate-spline muscle-path mapping, bilateral symmetrisation, and wrapping-surface optimisation. We hypothesised that this average model, adapted to a new individual by standard linear scaling alone, would reproduce that individual's MRI-based model's walking biomechanics more closely than a linearly scaled generic male-based model. We also expected that this advantage would be concentrated in pelvis- and hip-dependent outputs rather than distributed evenly across all joints. Using 5-fold cross-validation, the scaled average-female model and the scaled male model were each compared against the held-out individual's MRI-based model across gait kinematics, joint moments, muscle moment arms, muscle forces/activations, and joint reaction forces. The average-female model outperformed the male model in every output category (Holm-corrected p [&le;] *10-5), supporting our primary hypothesis. Consistent with our secondary hypothesis, differences were largest and most sustained for pelvis tilt, hip flexion, and gluteal/adductor moment arms and forces, and smaller for knee and ankle kinematics. Some divergence remained localised to early-stance knee kinematics and patellofemoral loading. The population-averaged female musculoskeletal model is freely available on SimTK https://simtk.org/projects/aver_fem and is recommended for studies involving female participants, particularly when pelvic and hip biomechanics are the primary outcomes.

Background: Acute osteoporotic vertebral fractures (OVFs) may be difficult to detect on conventional radiographs, particularly before substantial vertebral collapse occurs. Comparing supine and sitting lateral radiographs may reveal load-dependent vertebral mobility. This preliminary study evaluated the diagnostic accuracy of supine to sitting dynamic radiography for detecting MRI confirmed acute OVFs. Methods: This retrospective, single center diagnostic accuracy study included consecutive patients who underwent paired supine and sitting lateral radiography and MRI of the same spinal region between April 2024 and July 2026. Dynamic radiographs were interpreted by a board certified orthopedic and spine surgeon who was blinded to the MRI findings. MRI was independently interpreted by a second board certified orthopedic surgeon and served as the reference standard. The primary outcome was patient-level sensitivity and specificity. Vertebra level diagnostic accuracy was evaluated secondarily, with patient cluster bootstrap confidence intervals used to account for within patient correlation. Results: Sixty three patients (mean age, 80.6 years; 51 women [81.0%]) and 490 evaluable vertebrae were analyzed. MRI identified acute OVFs in 34 patients and 36 vertebrae. At the patient level, dynamic radiography yielded 31 true positive, no false-positive, three false negative, and 29 true negative results. Sensitivity was 91.2% (95% confidence interval [CI], 76.3%-98.1%), specificity was 100.0% (95% CI, 88.1%-100.0%), positive predictive value was 100.0%, negative predictive value was 90.6%, and overall accuracy was 95.2%. At the vertebral level, sensitivity was 91.7% (33/36; patient cluster bootstrap 95% CI, 81.3%-100.0%) and specificity was 100.0% (454/454). The three missed fractures involved T9, L2, and L3. No false-positive vertebrae were observed. Conclusions: Supine to sitting dynamic radiography demonstrated high patient level sensitivity and no observed false positive findings for MRI confirmed acute OVFs. It may provide a practical complementary diagnostic option when MRI is not immediately available. However, a negative dynamic radiographic examination does not exclude an acute fracture, and the apparent perfect specificity requires validation in larger, prospective multi-reader studies.

Maternal thermal strain is associated with adverse pregnancy outcomes, yet fetal temperatures cannot currently be directly measured, limiting quantification of fetal thermal strain. Here, we develop two steady-state models for estimating internal temperatures in a near-term fetus. First, we improve the only previously published human fetal thermoregulation model, deriving a closed-form solution within its simplified uniform-cylinder representation. Second, we introduce a multilayer, anatomically segmented model that resolves tissue-specific temperatures. Both couple the fetal body to central blood pool and amniotic fluid compartments and incorporate a new placenta-umbilical cord heat-exchanger representation. Predictions agree with available intrauterine scalp measurements, with fetal core and head-center temperatures approximately 0.5{degrees}C and 0.8{degrees}C above maternal core, respectively. Physiologically plausible changes in umbilical cord heat-exchanger effectiveness or blood flow increased fetal temperatures by approximately 0.3{degrees}C. These models enable estimation of otherwise inaccessible temperatures, while the multilayer formulation lays a foundation for transient, coupled maternal-fetal thermoregulation modeling.

Muscle architecture shapes muscle function and changes with age, growth, training and disease, yet quantifying three-dimensional (3D) muscle architecture in vivo remains challenging. We introduce a hybrid fascicle tractography approach for freehand 3D ultrasound data that accurately reconstructs 3D muscle fascicles with respect to an objective, anatomically relevant coordinate system defined by the muscle's central aponeurosis. The hybrid approach combines Hessian-based fascicle detection with wavelet-based refinement to generate volumetric fascicle orientations. In a synthetic dataset with known ground truth, fascicle orientations and lengths were estimated with errors of [&le;]2{degrees} and ~1.5%, respectively. In vivo, the approach detected physiologically plausible fascicle lengthening in the human tibialis anterior following a passive plantar flexion rotation, whereas diffusion tensor imaging of the same muscle did not. The proposed method enables anatomically relevant, objective and non-invasive quantification of 3D muscle architecture in vivo, providing a practical framework for applications in clinical and applied muscle physiology.

Mechanical homeostasis plays a central role in promoting and preserving optimal structure and function in the adult aorta. Although pathogenic variants can compromise homeostatic processes, it appears that intramural cells yet attempt to compensate for some genetically induced changes. In particular, lysyl oxidase is higher in the adult Marfan aorta compared with the age-matched control aorta. Here, we block lysyl oxidase in adult Fbn1C1041G/+ Marfan syndrome mice after stimulating aortic disease progression via induced hypertension. Whereas hypertension alone increases aortic dilatation, concurrent blocking of lysyl oxidase results in a dramatic increase in disease severity, driving an otherwise mild aortic phenotype in adult male Fbn1C1041G/+ Marfan mice to aneurysmal dilatations as well as dissection and rupture, with frequent premature death. Deposition and cross-linking of fibrillar collagens, among other extracellular matrix constituents, can represent a protective compensation against severe disease in the Marfan aorta. The present study emphasizes the need clinically to avoid compromising new collagen deposition and suggests that strategies to augment collagen cross-linking could be beneficial.

Continuous wave diffuse correlation spectroscopy (cw-DCS) is a noninvasive optical technique to monitor the tissues blood flow changes. This technique measures the tissue blood flow index (BFI) by evaluating the decay rate of the autocorrelation function. The derived BFI is proportional to mean squared displacements of the red blood cells considered as the fast-dynamic scatterer component of tissue in time. However, biological tissue contains static scatterer component and slow-dynamic scatterer component which affect the decay rate of autocorrelation function and as a result the derived BFI. In this study, we assessed the fractional contribution of static, slow-dynamic and fast-dynamic scatterer components of a medium in the flow index derived by cw-DCS. The measurements performed on Agar-based phantom with tube showed that presence of static scatterer component and slow-dynamic scatterer component led to substantial underestimation ({approx} 123%) of the flow index derived by Siegert relation, compared to effective diffusion coefficient of fast-dynamic scatterers components derived by modified Siegert relation and bi-exponential model. The less underestimation was observed for the corresponding parameters obtained from the liquid phantom measurements ({approx} 25%) as well as during the forearm occlusion test and respiratory challenges ({approx} 16% - 26%).

Purpose To evaluate whether domain-adaptive self-supervised pretraining on musculoskeletal radiographs improves fracture classification and attribution faithfulness relative to ImageNet-pretrained baselines. Materials and Methods This study (June 2025 to May 2026) used previously acquired radiographs to compare three ResNet-50 initializations: supervised ImageNet pretraining (control), self-supervised ImageNet pretraining (DINO), and DINO with additional domain-adapted pretraining on 44,029 musculoskeletal radiographs (DINO-Ortho). All models underwent supervised fine-tuning in three experiments: in-distribution (MURA and FracAtlas datasets), out-of-distribution (an external dataset of 5,365 calcaneal radiographs from 1,775 patients), and initial weights (calcaneal radiographs only). Metrics included sensitivity, specificity, test accuracy, area under the receiver operating characteristic curve (AUROC), and Cohen's kappa; attribution faithfulness was quantified using Remove and Debias scores from Grad-CAM saliency maps. Comparisons used DeLong and Friedman tests. Results Classification performance did not differ significantly between DINO-Ortho and either baseline in any experiment (DINO-Ortho AUROC, 0.89 in-distribution and 0.95 with initial weights). All three models discriminated poorly out-of-distribution (control, 0.59; DINO, 0.57; DINO-Ortho, 0.58). DINO-Ortho showed significantly higher attribution faithfulness than both baselines in all three experiments, including out-of-distribution (25.39 vs -10.41 and 2.14; P < .001) and initial weights (20.88 vs 11.51 and 1.27; P < .001). Qualitative rankings favored DINO-Ortho but did not differ significantly. Conclusion Domain-adapted self-supervised pretraining on musculoskeletal radiographs improved attribution faithfulness while maintaining classification performance comparable to ImageNet-pretrained baselines; no model generalized adequately to external radiographs without task-specific fine-tuning.

Cerebrovascular pulsatility drives measurable brain tissue deformation and has been associated with ageing and a range of neurological disorders. Yet how pulsatile haemodynamic forces are transmitted through deformable cerebral arteries into the surrounding brain remains poorly understood, particularly in anatomically realistic vascular geometries. Existing computational approaches have largely treated cerebral fluid and tissue mechanics separately or relied on idealised geometries, limiting our ability to determine how vascular anatomy simultaneously governs intraluminal haemodynamics and extravascular mechanical loading. Here, we develop an image-derived three-dimensional computational framework that jointly resolves pulsatile blood flow, arterial wall deformation and surrounding brain tissue motion in representative cerebral arteries. Four arterial segments, including the middle cerebral artery, middle cerebral artery bifurcation, basilar artery and internal carotid artery, are reconstructed from high-field (5 Tesla) magnetic resonance imaging data of a healthy subject. A finite-deformation fluid-structure interaction model is established by coupling non-Newtonian blood flow, hyperelastic arterial wall and hyper-viscoelastic brain tissue. The predicted tissue response is benchmarked against in vivo magnetic resonance elastography measurements of cardiac-induced volumetric strain over a cardiac cycle. Results reveal spatially localised arterial and tissue deformation whose magnitude and distribution are strongly governed by vascular geometry and wall thickness. Among the segments examined, the internal carotid artery exhibits the largest deformation response, while reduced wall thickness increases strain transmission into the surrounding tissue. Geometrically complex regions also exhibit greater spatial heterogeneity in near-wall haemodynamic metrics. These findings demonstrate that cerebral vascular anatomy simultaneously shapes intraluminal haemodynamics and extravascular mechanical loading. By integrating image-derived vascular anatomy, coupled blood-vessel-brain mechanics and in vivo benchmarking within a unified framework, this study provides a mechanically consistent reference for healthy cerebral pulsatility and establishes a foundation for quantifying how blood-vessel-brain interactions are altered under pathological conditions.

Pulmonary hypertension (PH) is characterized by progressive structural and mechanical remodeling of the pulmonary vasculature, yet few computational frameworks directly link disease mechanisms to longitudinal progression and therapeutic response. In this study, we utilized a multiscale pulmonary arterial growth and remodeling (G&R) framework to capture evolving functional metrics from rat models of PH. This framework couples morphometric tree hemodynamics, constrained mixture theory-based wall mechanics, and maladaptive cellular remodeling. Disease progression was driven by three mechanistically interpretable parameters governing excess smooth muscle production, remodeling activation, and passive stiffening. These parameters were calibrated to longitudinal monocrotaline (MCT) measurements of pressure, wall thickness, and stiffness from prior work using a multiobjective optimization. To show the predictive value of this model, we simulated therapeutic intervention within the same disease-specific framework by using functional cell-level responses to therapy to inform changes in parameter values. Calibration to the study-specific MCT dataset reproduced the temporal increases in pressure, wall thickness, and stiffness, demonstrating that the model could capture multiple features of vascular remodeling simultaneously, with R2 values of 0.81, 0.83, and 0.95, respectively. Simulated treatment reduced pressure, wall thickness, and stiffness. Predicted pressure and wall-thickness responses agreed closely with the corresponding experimental treatment effects, whereas stiffness recovery was overpredicted, suggesting that additional mechanisms may contribute to persistent vascular stiffening after intervention. The framework also captured the overall progression of pulmonary pressure increases across both aggregated MCT and Sugen-hypoxia datasets, suggesting utility across studies and animal models. This work outlines a physics-based, multiscale framework that simulated quantities of direct clinical interest in a mechanistically interpretable platform for linking pulmonary vascular remodeling and treatment response. It supports comparisons across experimental phenotypes and interventions while identifying where constitutive refinements are needed to improve predictive capability across phenotypes.

Electrostatic actuation is an emerging technology for generating tactile sensations on capacitive touchscreens through voltage-induced attractive forces between a fingertip and the surface. However, accurate control of electrostatic attraction during natural touchscreen interactions remains challenging because the applied normal force and sliding speed continuously vary, and their effects on the fingertip-screen contact and resulting actuation strength are not fully characterized. Here, we show how normal force and sliding speed systematically alter fingertip- screen contact area and electrical impedance, and use these measured changes to estimate electrostatic attraction during sliding. Contact area, interaction forces, and electrical impedance were measured simultaneously as participants slid their fingertips across an electrostatic surface under systematically varied normal forces and sliding speeds. These measurements revealed condition-dependent changes in fingertip contact, electrical interaction impedance, effective capacitance, derived effective gap thickness, and electrostatic attraction. We then incorporated these measured contact quantities into a physics-informed, data-driven model based on parallel-plate capacitor theory, in which effective capacitance, apparent contact area, and effective voltage determine the estimated electrostatic attraction. The resulting model links force- and speed-dependent changes in these quantities to electrostatic attraction while accounting for inter-participant variability through a participant-specific scaling factor. These findings provide experimentally grounded guidance for designing electrostatic surface-haptic feedback and future adaptive control strategies under realistic touch conditions.

Introduction: Metastatic spinal lesions substantially alter vertebral mechanical properties and increase fracture risk. Computed tomography (CT) based finite element (FE) models can estimate vertebral strength, but their accuracy depends on how CT derived material properties are represented. This study evaluated the effect of two material grouping strategies on simulated strength and stiffness in metastatic vertebrae. Methods: We compared Adaptive Clustering (AC) with Uniform fixed width grouping in 44 vertebrae from 11 donors (8 osteolytic, 12 osteoblastic, 12 mixed, 12 no observed lesion (NOL)). FE models were generated based on CT scans with 2 to 500 material groups and compared for material mapping error and simulated strength and stiffness. Overall and lesion stratified agreement with experimental measurements was assessed in an exploratory analysis. Results: AC showed significantly lower Young's modulus root mean square error than Uniform (p < 0.05). Simulated strength and stiffness stabilised by 50 material groups. At 50 groups, simulated strength showed moderate correlation with experimental strength overall (R2 = 0.57), strongest in NOL vertebrae (R2 = 0.82) and lower in lesion-bearing vertebrae (R2 = 0.4-0.59). Stiffness showed weaker correlation overall (R2 = 0.27), highest in NOL vertebrae (R2 = 0.48) and negligible in mixed lesions (R2 = 0.007). Bland Altman analyses indicated systematic underestimation of experimental fracture load. Discussion: AC improved material-mapping fidelity, whereas increasing material groups beyond 50 had little influence on simulated strength or stiffness. Numerical stabilisation therefore did not imply experimental accuracy. Lesion stratified findings were exploratory and should be interpreted cautiously because of limited subgroup sizes.