Current testicular prostheses are predominantly manufactured from silicone elastomers and often fail to reproduce the biomechanical and viscoelastic characteristics of native testicular tissue. This study aimed to develop and mechanically characterize a poly(vinyl alcohol) (PVA) hydrogel-based testicular prosthesis with tissue-mimicking properties. PVA hydrogels with concentrations of 5%, 10%, and 15% (w/v) were fabricated using a freeze-thaw crosslinking process and evaluated through comprehensive mechanical testing, including uniaxial compression, tensile testing, stress relaxation, creep, dynamic mechanical analysis (DMA), and cyclic compression fatigue testing. A prototype hydrogel testicular prosthesis was subsequently fabricated and its mechanical performance compared with native testicular tissue and a commercially available silicone implant. Mechanical behavior was strongly dependent on polymer concentration. Increasing PVA concentration resulted in significant increases in compressive modulus, tensile strength, toughness, storage modulus, and fatigue resistance. The 10% PVA hydrogel demonstrated the closest overall agreement with native tissue, exhibiting a compressive modulus of 78 ± 10 kPa compared with 64 ± 12 kPa for native tissue, while maintaining comparable tensile strength, recovery ratio, and energy dissipation characteristics. Viscoelastic characterization revealed tissue-like stress relaxation and creep responses, whereas cyclic compression testing demonstrated stable mechanical performance over 1000 loading cycles. In contrast, the silicone implant exhibited lower compliance, reduced energy dissipation capacity, and inferior overall biomechanical similarity to native tissue. These findings demonstrate that freeze-thaw PVA hydrogels provide a promising platform for biomimetic testicular prostheses. By tailoring polymer concentration, hydrogel implants can achieve mechanical and viscoelastic properties that more closely replicate native tissue than conventional silicone devices. The proposed hydrogel-based approach may improve implant realism and patient outcomes, providing a foundation for future long-term durability studies and in vivo evaluation.


Subject-specific finite element analysis accurately characterizes knee joint mechanics but is computationally expensive. Deep surrogate models provide a near-real-time alternative, yet their generalization across subjects under limited pose and load inputs remains unclear. It remains unclear whether the dominant source of prediction uncertainty arises from temporal history dependence or spatial propagation dependence. 
Methods: 
To disentangle these factors, we employed a shared MeshGraphNet (MGN) backbone with a fixed mesh topology. A dataset of running trials from nine subjects was constructed using an OpenSim-FEBio workflow. We developed four model variants to isolate specific dependencies: (1) a baseline MGN; (2) CT-MGN, incorporating a Control Transformer to encode short-horizon history; (3) MsgModMGN, applying state-conditioned modulation to message passing for adaptive propagation; and (4) CT-MsgModMGN, combining both mechanisms. Models were evaluated using a rigorous grouped 3-fold cross-validation on unseen subjects.
Results: 
The models incorporating history encoding (CT-MGN and CT-MsgModMGN) significantly outperformed the baseline MGN and MsgModMGN in global accuracy (lower RMSE) and spatial consistency (higher Dice/IoU). Crucially, the CT module effectively mitigated the "peak-shaving" defect common in deep surrogates, significantly reducing peak stress prediction errors (REmax). In contrast, the spatial propagation modulation (MsgMod) alone yielded no significant improvement over the baseline, and combining it with CT provided no additional benefit.
Conclusion: 
Temporal history dependence, rather than spatial propagation modulation, is the primary driver of prediction uncertainty in cross-subject knee contact mechanics. Explicitly encoding short-horizon driver sequences enables the surrogate model to recover implicit phase information, thereby achieving superior fidelity in peak-stress capture and high-risk-region localization compared to purely state-based approaches.

Most mandibular finite element models are deterministic and overlook the influence of biological and modeling variability. This study proposes an automated, uncertainty-aware computational workflow for a patient-specific mandibular FE model using Latin Hypercube Sampling and sparse Polynomial Chaos Expansion. We investigated 24 input parameters related to masticatory muscle loading, material properties, and geometric discretization over 2,400 simulations. Global and regional sensitivity analyses were performed using both Spearman rank correlations and variance-based Sobol indices to identify the primary drivers of von Mises stress. Within this modeling framework, muscle force magnitudes and articular disc stiffness are the dominant sources of stress variability, whereas high-resolution bone property classification had a negligible influence within the explored ranges. Statistical convergence analysis demonstrated that contact-sensitive condylar regions require significantly larger sample sizes (N>2,000) for stable sensitivity estimates compared to global metrics. This methodological benchmark identifies critical modeling parameters and provides a scalable pipeline for future patient-specific biomechanical studies and cohort-level simulations.

Existing evaluations of IMU-based joint angle estimation mainly rely on global accuracy metrics, which may obscure local error exposure during complex functional movements. This study analyzed data from 16 healthy male participants in the Hip-ROM-Y dataset. Using leave-one-subject-out outputs from a unified left hip joint predictor, we characterized left hip angle estimation errors by movement category, normalized movement phase, and high-error segment. The relationship between error distribution and post hoc disturbance features was further examined. The results showed that, under the current model and data conditions, complex movements (CMs) generally produced higher errors than basic movements. However, the increase in error was not uniformly distributed, but was mainly concentrated in local mid-phase periods of several CMs and was accompanied by greater deviations in the relative relationship between the pelvis and thigh segment. These findings suggest that evaluations of hip angle estimation under similar wearable configurations should pay attention to local error distributions during CMs and to the stability of the pelvis-thigh segment relationship.

Compared with conventional needle-based injections, needle-free injections offer several advantages, including ease of operation and elimination of accidental needlestick injury. To investigate the influence of piston structure on the performance of a needle-free injection system, this study combined experiments with fluid-structure interaction numerical simulations to systematically examine the effects of groove length (L), groove height (H), and the spacing (L0) between the two grooves on jet performance and piston stress. The results showed that during the initial stage of needle-free injection, both the stagnation pressure and jet velocity exhibited pronounced oscillatory behavior, and the driving structure played a significant role in modulating this oscillation pattern. For the single-groove piston, as the groove volume increased fromL= 0 mm,H= 0 mm toL= 3 mm,H= 0.13 mm, the peak stagnation pressure increased by 22.3%, whereas the maximum von Mises stress in the piston rose from 0.53 MPa to 7.21 MPa. Based on the optimal single-groove configuration, the groove was further divided into a dual-groove structure with identical groove length and height. The results indicated that, as the dual-groove spacingL0increased from 0 to 1.5 mm, the maximum von Mises stress first rose sharply to a peak, then decreased to approximately 3 MPa atL0= 0.25 mm, and remained nearly stable forL0> 0.25 mm. Meanwhile, the peak stagnation pressure gradually decreased with increasing groove spacing. Considering the combined variation in peak stagnation pressure and structural stress,L0= 0.25 mm was identified as the optimal groove spacing. Compared with the optimal single-groove structure, the corresponding dual-groove configuration resulted in a reduction of less than 1% in peak stagnation pressure, while reducing the maximum von Mises stress by 58.4%.

Hand exoskeletons have emerged over the past two decades as promising tools to restore or augment hand function in individuals with neurological injury and to support users in daily activities. This paper presents a comprehensive survey of recent developments in wearable hand exoskeletons. First, key design considerations of hand exoskeletons are investigated, including primary design parameters, actuation and power transmission schemes, and factors related to safety and fit. From a perspective of device control, existing strategies are reviewed according to rehabilitation stages, controller characteristics and feature quantities. Then, functional and clinical evidence was interpreted as engineering or mechanistic validation, functional assistive evidence, or clinically relevant outcomes. Clinically relevant outcomes showed the highest favourable proportion (83%, 19/23 domain-level observations), followed by functional assistive evidence (79%, 22/28) and engineering or mechanistic validation (73%, 11/15), suggesting a broadly positive direction of evidence. Current studies most consistently support short-term functional assistance and task-capacity enhancement, whereas training-related clinical benefits remain promising but limited by small samples, heterogeneous populations and devices, variable training dose, co-interventions, and limited follow-up. The design-control-outcome synthesis suggests that lightweight, low-impedance, well-aligned, and safe architectures, together with intention-aware or adaptive control, may improve usability, engagement, and personalisation, although their independent clinical contribution remains insufficiently isolated. Finally, existing problems of hand exoskeletons are discussed, and potential directions for future research are outlined.

Male stress urinary incontinence (SUI), the involuntary leakage of urine due to physical exertion, is commonly managed by penile clamps. However, there is currently no methodology to quantify how effectively penile clamps prevent urine leakage while preserving blood flow without relying on patient-dependent studies. Our benchtop model provides a controlled, reproducible framework for comparing penile clamp performance under simplified physiological conditions, offering comparative data on clamp efficacy. Force applied by the clamps was determined via a load cell to estimate contact stress. Separately, penile clamps were applied to foam cylinders with channels simulating the urethra and dorsal vein. The following penile clamps were used: The Cunningham Clamp, The Pacey Cuff, The Lunderg Freedom Clamp, and The Squeezer Klip. The foam-based penis model allowed us to assess urine and blood flow inhibition post-clamp application. The channels were both lined with identical latex tubing to standardize compliant wall properties given inter-individual variability in dimensions of the dorsal vein and urethra. To account for variable penile tissue resistances, low-stiffness (Foam 6) and high-stiffness (Foam 17) foams were tested. Average urine flow rates achieved in Foam 6 and 17 were within physiological range for average SUI patients (9.72 ml s-1and 9.06 ml s-1respectively), and a blood pressure of 51.8 mmHg was achieved using a blood substitute with viscosity of 3.7 cP. In Foam 6, no clamps caused more than 10% blood flow inhibition. However, in Foam 17, there were significantly higher levels of blood flow inhibition across almost all clamps and their settings, most notably with the Lunderg Freedom Clamp (approx. 60%). Overall, clamp efficacy was more dependent on pressure distribution via each clamp's design rather than absolute contact stress. Results were consistent with patient reviews, and mechanisms of the clamp itself, suggesting reliability and validity of the model.

The spatiotemporal distribution of coagulation factors fundamentally governs blood coagulation dynamics. Although these dynamics have been examined at the submillimeter scale (hundred micrometers), how this distribution influences thrombus formation at dimensions comparable to or larger than those of medium-sized vessels (on the order of 1 mm in diameter) remains insufficiently clarified. In this study, we performed numerical simulations using a well-established reaction-diffusion model of the intrinsic coagulation pathway to investigate coagulation kinetics over millimeter-scale domains, while explicitly incorporating the effects of walls and convection on coagulation. The simulation settings were validated against experimentally observed coagulation behaviors. Our results indicated that in blood domains adjacent to an active wall surface, the propagation velocities of the thrombin wave and the advancing clot front decreased with increasing distance from the wall and approached a constant value at approximately 200µm. This spatial variation in velocity led to domain-size-dependent behavior in the temporal evolution of the volume-averaged thrombin concentration in millimeter-scale domains analyzed in thrombin generation assays because the domain size determined the ratio of the active surface area to blood volume. In addition, simulations of coagulation along a 5 cm-long thin filament within a rat arteriovenous shunt showed a progressive increase in the coagulation rate along the flow direction, indicating that the longitudinal distribution of coagulation activity governs the total clot volume. Together, these findings underscore the need to resolve multiscale spatial distributions of coagulation, from the micrometer to centimeter scales, to improve understanding of thrombus formation under physiological conditions where the effects of walls and convection interact.

Surface irregularities can substantially modify local hemodynamics within coronary arteries. This study experimentally investigated the influence of controlled grooved surface geometries on pulsatile flow characteristics using idealized coronary-type stenosis models. Four transparent models were fabricated, consisting of a smooth control and three grooved surfaces with increasing groove amplitudes. Time-resolved particle image velocimetry was employed to quantify phase-averaged velocity fields, recirculation structures, and turbulent kinetic energy (TKE). The results showed that groove-induced surface irregularities enhanced jet deflection, near-wall recirculation, and in-plane cross-stream motion compared with the smooth stenosis model. As groove amplitude increased, downstream jet deflection became more pronounced, indicating a redistribution of velocity fluctuations in the post-stenotic region. In contrast, the smooth stenosis sustained a longer and more coherent jet structure. Increased groove amplitude also reduced the downstream extent and magnitude of measured planar TKE. These findings demonstrate that even small-scale surface features can significantly alter post-stenotic flow structures and the spatial development of turbulence under coronary-relevant pulsatile flow conditions.

Beam-hardening and material cross-contamination remain significant challenges in quantitative computed tomography of multi-component samples acquired using polychromatic x-ray sources. In this work, a polychromatic quantitative absorption tomography (QAT) technique is extended to reconstruct component-specific density distribution maps in a two-component sample. The technique decomposes projection sinograms acquired under two distinct incident x-ray spectra into component-specific column density sinograms using a spectral forward model. Residual cross-contamination artifacts are addressed using a quantitative correction procedure based on spatial reference masks obtained by segmenting conventional linear attenuation reconstructions. Contaminated regions are identified from these masks and reinterpreted in the sinogram domain using the same polychromatic forward model prior to back-projection. Experimental validation was performed on an intertwined Al-Cu wire sample. The proposed correction improves material separation, reduces streak artifacts, and brings reconstructed densities within one standard deviation of independently measured average densities of the components. Together, the extended QAT technique and quantitative correction procedure provide a physically consistent methodology for improved quantitative densitometry in multi-component samples, with extensibility to samples containingcomponents.

Opportunistic assessment of volumetric bone mineral density (vBMD) from computed tomography (CT) scans offers a strategy to identify individuals at risk of osteoporosis. However, accurate CT-based vBMD quantification depends on appropriate density calibration, and direct comparisons of synchronous, asynchronous, and tissue-based internal calibration in low-dose chest imaging are limited. This study had two objectives: (1) to assess the impact of calibration methods on image quality in low-dose chest CT, particularly whether the inclusion of a calibration phantom compromises image quality, and (2) to examine whether these variations influence agreement in vBMD measurements across calibration techniques. 51 participants underwent chest CT; 23 with a calibration phantom (synchronous) and 28 without (asynchronous). Trabecular vBMD was quantified at the fourth and eighth thoracic vertebrae (T4 and T8, respectively) and the first lumbar vertebra (L1). Image quality was assessed using stochastic noise and signal-to-noise ratio (SNR) in calibration phantom rods and tissue-based reference regions. Agreement in vBMD measurements was evaluated using Pearson's correlation coefficients, Bland-Altman analyses, and absolute deviations relative to internal calibration. Internal calibration tissues demonstrated stable image quality across synchronous and asynchronous acquisitions, whereas synchronously scanned calibration phantoms exhibited increased noise and reduced SNR. In vBMD measurements, asynchronous calibration demonstrated smaller deviations (19.15 ± 11.59 mg cm-3vs. 10.19 ± 9.69 mg cm-3) than synchronous across vertebral levels. These findings show that calibration strategy affects both image quality and vBMD agreement in low-dose chest CT. Asynchronous and tissue-based internal methods provided more consistent estimates than synchronous calibration, supporting their use for opportunistic osteoporosis assessment.

Accurate restoration of the centre of rotation (CoR) is crucial for the long-term success of a total hip replacement (THR); however, cup positioning remains one of the major challenges of this procedure. The aim of this study was to critically review the existing literature documenting CoR planning in THR. Specifically: 1. The rationale behind component placement; 2. The benefits and limitations of the current techniques used; and 3. Future directions and their application to clinical practice. Traditional two-dimensional (2D) templating, although widely used, has limited accuracy due to magnification errors and variability in patient positioning. Three-dimensional computed tomography (3D-CT) preoperative planning allows for a more precise estimation of CoR. Integration with robotic systems enables intraoperative execution of the plan but comes with high costs and a steep learning curve. Patient-specific instrumentation (PSI) provides a cost-effective alternative. Meanwhile, surgeon experience and intraoperative judgement remain crucial, particularly in patients with abnormal anatomy or deformities. Restoration of CoR within approximately 5 mm of the planned medial and superior position has been associated with improved biomechanical performance and implant longevity. While 2D templating can achieve this in most routine cases, 3D planning, robotic-assisted surgery, and PSI allow for more accurate placement. This is particularly useful in complex cases, such as revisions or developmental dysplasia of the hip, where the risk of clinically significant deviations remains high and more targeted surgical strategies are needed.

Purpose.To compare the biomechanical performance of different femoral condyle donor sites for autologous osteochondral transplantation (AOT) of the talus.Methods.Patient-specific finite element models were constructed based on postoperative computed tomography scans from 17 individuals with cystic osteochondral lesions of the talus. The femoral condyles were divided into six distinct donor sites: the medial superior (MS), medial central (MC), medial inferior, lateral superior , lateral central, and lateral inferior regions. Finite element analysis (FEA) was employed to simulate the biomechanical response under a simulated standing load, quantifying von Mises stress, displacement, and strain.Results.No significant differences were observed in mean stress or mean strain among graft from different femoral condyle sites (P> 0.05). The MS graft demonstrated significantly lower displacement compared to the MC graft (Kruskal-Wallis test,H= 14.710,P= 0.012; Dunn's post-hoc,Z= 3.527, adjustedP= 0.0063) and relative to the adjacent talar articular surface (P= 0.002, Bonferroni-correctedα* = 0.0028). No significant differences were observed in mean stress or strain among other femoral condyle graft sites (P> 0.0028 Bonferroni correction).Conclusion.In AOT using the femoral condyle as the donor site, stress distribution did not differ significantly across different donor regions; however, the MS region showed relatively small displacement.

Clinical gait analysis is essential for understanding motor and cognitive contributions to mobility impairment. Continued methodological advancement in gait analysis is needed to detect important and subtle changes in walking behaviour that will inform this understanding. This study evaluated the reliability of a finite state machine (FSM) algorithm for stride segmentation during preferred and dual-task walking (DTW) and examined changes to temporal and accelerometry kinematic outcomes between tasks. Participants diagnosed with Alzheimer's disease or mild cognitive impairment completed a gait assessment as part of the Ontario Neurodegenerative Disease Research Initiative foundational study. Ankle-worn accelerometers and a GAITRite walkway captured data during preferred walking and three DTW conditions (counting backwards by ones, animal naming, counting backwards by sevens). Acceleration data were processed using the FSM algorithm to extract temporal and accelerometry kinematic outcomes defined by the FSM intra-stride segments. Stride time demonstrated excellent reliability (ICC ⩾ 0.97). Gait speed was significantly associated with gait variability during animal naming and counting backwards by sevens (p< 0.05), but not during counting backwards by ones. The FSM approach showed changes to intra-stride phases and accelerometry derived kinematics not seen with conventional stride-based approaches. There was a reduction in flat-foot phase and an increase in push-off phase across all dual-task conditions compared with PREF (p< 0.05), where conventional stance-phase segmentation did not show consistent differences. Kinematic outcomes were also significantly lower during DTW conditions when compared to preferred walking trials (p< 0.05) for the mid-swing peak amplitude and the slope of the accelerometer push-off. Findings demonstrate differences in performance between preferred and DTW conditions, the influence of gait speed on gait variability, and unique accelerometry-derived kinematics. The FSM segmentation method advances gait assessment by providing precise stride characteristics using low-cost, clinically accessible tools.

Carpal tunnel syndrome is usually assessed by clinical examination and electrodiagnostic testing, but these methods may not always be practical for rapid screening. In this work, it was explored whether hand motion recorded with a low-cost optical camera could add useful information to routine clinical data. Demographic variables, symptom-related findings obtained after the Phalen test, and five thumb-to-finger opposition tasks were collected. Hand landmarks were extracted with MediaPipe and used to derive kinematic descriptors, which were then analyzed together with clinical variables by machine-learning and hybrid deep-learning models. To reduce the risk of overly optimistic estimates, the main evaluation was carried out at hand level with leave-one-group-out cross-validation. In the primary leakage-safe comparison, the best Dataset 4 multimodal model yielded the strongest binary screening profile. Compared with the clinical Dataset 1 baseline, accuracy increased from 82.6% (95% CI 75.0%-90.2%) to 87.0% (79.3%-93.5%), sensitivity from 70.0% (54.4%-85.1%) to 80.0% (64.7%-93.4%), specificity from 88.7% (80.3%-95.6%) to 90.3% (83.1%-96.8%), and ROC-AUC from 0.845 (0.745-0.934) to 0.855 (0.752-0.945). In the same-architecture tests, the kinematic variables did not behave uniformly across model families. The clearest gain among the classical models was seen with light gradient boosting machine. Feature-level results were also consistent with the model findings, as selected thumb-opposition coordinates differed across stages and appeared to capture a functional component not represented by symptom scores. In the four-class severity task, the improvement was small: accuracy increased from 81.5% (72.8%-89.1%) to 82.6% (73.9%-90.2%), and macro-1 increased from 0.706 (0.544-0.823) to 0.748 (0.588-0.850). In this cohort, the optical hand-kinematic measures mainly strengthened the screening analysis. Their use for finer severity staging will need confirmation in larger external datasets and in participant-level analyses.