Search Results (1,095)

This article discusses advanced artificial intelligence (AI)-based strategies for the design and personalization of three-dimensionally (3D) fabricated hand exoskeletons, with a focus on adaptive, data-driven methodologies. It highlights the crucial role of intelligent personalization in improving user comfort, functional performance, and rehabilitation outcomes, particularly in medical and care settings. The proposed approach integrates biomechanical modeling, high-resolution 3D scanning, and machine learning (ML) algorithms to create exoskeleton systems tailored to the unique anatomical and motor characteristics of individual users. This article presents both a theoretical framework and practical implementation of AI-based adaptation, addressing key challenges such as precise anatomical fit, ergonomic optimization, and real-time responsiveness. Specific emphasis is placed on AI-based feedback mechanisms that enable continuous, dynamic adjustment of control parameters during device operation. Case studies illustrate the effectiveness of these techniques in improving performance and rehabilitation progress for individual users. By combining intelligent modeling, adaptive control, and additive manufacturing, this research advances the field of wearable robotics and points the way to more accessible, efficient, and fully personalized assistive technologies. Full article

Neurogenic atrophy is the most severe type of muscle atrophy. It can be caused by injury or disease of the nerve that connects to the muscle. Damage to the sciatic nerve (nervus ischiadicus) initiates molecular processes that lead to the transformation of muscle dysfunction into an atrophic state. Oxidative stress is one of the key factors that initiates skeletal muscle atrophy. Therefore, this study evaluates the effects of oral administration of water-soluble C₆₀ fullerenes (daily dose: 1 mg/kg), as powerful antioxidants, on the contraction dynamics of the rat musculus soleus on days 15, 30, and 45 following neurogenic atrophy induced by transection of the nervus ischiadicus. Using biophysical (tensometric), biochemical, and histological analyses, we evaluated the biomechanical parameters of musculus soleus contraction (time of onset of muscle force response, integrated muscle power, maximum and minimum contraction forces), blood biochemical markers (concentrations of C-reactive protein, lactate, creatinine, and reduced glutathione, as well as superoxide dismutase and catalase activities), as well as histological and morphometric indicators of muscle damage in rats on days 15, 30, and 45 after injury induction. It was found that the use of water-soluble C₆₀ fullerenes improves the contractile activity of the musculus soleus after neurogenic atrophy and has a time-dependent nature. Specifically, by day 45 of the experiment, the maximum therapeutic effect reached 23–35 ± 2% for the biomechanical parameters of muscle contraction, and the biochemical blood parameters have nearly approached the control values. Finally, histological analysis confirmed a significant reduction in signs of destruction in muscle fibers and the level of fibrosis in the musculus soleus. These findings suggest the potential application of water-soluble C₆₀ fullerenes in the treatment of pathological conditions of the muscular system arising from peripheral nerve injury. Full article

Background: Digital workflows based on computer-aided design and computer-aided manufacturing (CAD/CAM) enable the modification of the vertical dimension of occlusion (VDO) during occlusal splint design; however, the clinical reproducibility of these digital adjustments compared with conventional methods remains unclear. Objective: This in vitro study aimed to evaluate the accuracy and reproducibility of vertical dimension increase achieved with three different dental CAD software systems. Methods: A standardized STL dataset was used to design occlusal splints with three CAD software systems: ExoCAD DentalCAD (Exocad GmbH, Darmstadt, Germany), InLab SW 23 (Dentsply Sirona, Bensheim, Germany), and Medit Link (Medit Corp., Seoul, South Korea). A conventional articulator-derived condition served as the comparator. Splints were manufactured using Night Guard Firm 2 Midnight resin (SprintRay Inc., Los Angeles, CA, USA), and the vertical dimension was measured with a digital caliper (Mitutoyo Corp., Kanagawa, Japan). Representative STL superimposition was performed using OraCheck 5.0 (Dentsply Sirona, Bensheim, Germany), and biomechanical behavior was assessed using ANSYS Mechanical 2025 R2 (ANSYS Inc., Canonsburg, PA, USA). Data were analyzed using one-way ANOVA followed by Tukey’s HSD post hoc tests, with the significance level set at α = 0.05. Results: The CAD systems showed variable accuracy in reproducing the reference vertical dimension; the Medit Link group yielded values closest to the reference (22.80 mm vs. 22.68 mm), the InLab group demonstrated marked overestimation (26.70 mm), and the ExoCAD group presented intermediate values (24.36 mm). One-way ANOVA confirmed statistically significant differences between the four groups for both sides (p < 0.001) with very large effect sizes (η² > 0.98). Three-dimensional superimposition revealed that the InLab splint presented the smallest mean surface deviation from the control (0.36 mm) and the highest proportion of points within 0.1 mm (59%), whereas Medit Link and ExoCAD showed larger mean global distances (0.83 mm and 0.70 mm, respectively). FEA revealed differences in biomechanical behavior, with the highest representative von Mises stress in the Medit Link geometry and the highest representative total deformation in the ExoCAD geometry. Conclusions: Digital modification of VDO is feasible, but its accuracy and reproducibility depend on the CAD system used. Careful verification of CAD design parameters against a conventional clinical reference is advisable before manufacturing occlusal splints involving vertical dimension modification, while representative 3D superimposition may provide complementary descriptive information. Full article

The high rate of reinjury after anterior cruciate ligament reconstruction (ACLR), persistent sex-related disparity, and increased susceptibility during transitional stages in female football players highlight the need for more specific strategies to identify biomechanical parameters associated with valgus collapse. This study aimed to compare three-dimensional knee kinematic and synchronized electromyography (EMG) muscle activity of the medial and lateral thigh muscle complexes during a change of direction (COD) task, between ACLR and healthy controls players. A cross-sectional case–control study was conducted with 26 under-23 semiprofessional female football players (22.89 ± 2.68 years), divided into ACLR (n = 13) and control (n = 13) groups. The maximum and minimum peaks and range of knee angular velocity across three planes, along with the average and peak electromyography (EMG) muscle activity of the Biceps Femoris (BF), Semitendinosus (ST), Vastus Medialis (VM), and Vastus Lateralis (VL), were recorded during the preparation and load phases. Between-group differences were assessed using independent t-tests or Mann–Whitney U tests. Statistical significance after Holm–Bonferroni correction was established at p-Holm < 0.05. ACLR players demonstrated significant increased knee valgus angular velocity, alongside 4% reduced average ST muscle activity and 27% diminished peak BF muscle activity during the load phase, compared to controls. These findings indicate altered knee kinematic and muscle activity patterns during COD in ACLR players, suggesting persistent long-term functional adaptations in female football players after ACLR. Full article

Perennial alfalfa roots form a composite with the soil, contributing to intensified grassland degradation and reduced yields. Soil-loosening and root-cutting tools are effective in disrupting root–soil composites and reducing soil compaction. However, loosening and root-cutting operations commonly face challenges, such as high tillage resistance and disturbance. This study developed a simulation model of the alfalfa root–soil composite based on the coupled Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH) method when considering the biomechanical properties of roots. The validity of the model was verified using direct shear and cutting tests. The errors in both simulation and test results were less than 8%. Additionally, a vibration root-cutting shovel was designed. The factors of tillage speed, vibration frequency, amplitude, and direction were analyzed for their impact on tillage resistance and root shear displacement. Results indicated that the incorporation of vibration enhanced soil breaking and reduced root-cutting displacement. The optimal combination of parameters determined using the Response Surface Method (RSM) for minimizing tillage resistance and shear displacement were a tillage speed of 0.86 m·s⁻¹, vibration amplitude of 3.79 mm, vibration frequency of 45.05 Hz, and vibration parallel to the tillage direction. Field tests confirmed the effectiveness of the vibratory root-cutting shovel. The addition of vibration parallel to the tillage direction can reduce tillage resistance by 16.68% and penetration resistance by 26.80%. This study provides a methodology for modeling root–soil composite and improving the root-cutting shovel for grassland degradation restoration. Full article

Viscous effects play an important role in the mechanical characterization of soft biological tissues under high-strain-rate loading. Accurate modeling of these behaviors is important for impact biomechanics, injury prediction, and crash safety analysis, in which biological tissues may experience high-strain-rate deformation. To describe the dynamic mechanical responses of soft tissues, a reliable constitutive framework is therefore needed to represent the dynamic response of soft tissues under high-strain-rate loading. The objective of this study is to develop and evaluate a viscohyperelastic constitutive framework for describing the dynamic compressive responses of multiple soft tissues. The proposed formulation is constructed within a continuum mechanics framework, in which the viscous contribution is expressed using objective invariant functions, namely $J_2$, $J_6$, and $J_7$. The developed analytical formulations are calibrated against high-strain-rate experimental data from different soft biological tissues, namely porcine meniscus, bovine liver, and ovine brain tissues. To find the material model parameters, genetic algorithm optimization is used to identify the material parameters and assess the robustness of the fitting procedure. In order to assess the robustness of the proposed constitutive framework across different loading rates, a multi-objective optimization strategy is used to calibrate the model parameters by fitting multiple strain-rate-dependent responses at the same time. This approach enables the model predictive capability to be evaluated over a range of high-strain-rate conditions. These results show that the proposed framework can reasonably describe the nonlinear and rate-dependent mechanical responses of different soft tissues under dynamic compression. Full article

Background/Objectives: Previous studies have measured a limited number of biomechanical parameters during medical rehabilitation of an anterior cruciate ligament (ACL) rupture. This study aimed to quantitatively assess changes in gait biomechanics, knee function, and lower-extremity muscle activity during after ACL reconstruction. Methods: The study included 32 patients after arthroscopic ACL reconstruction. The patients were divided into three groups based on postoperative time points: 0.5 year (12 men), 1 year (7), and over 1 year (9). Gait analysis at both self-selected and fast speeds was performed using an inertial system. Statistical analysis was performed using rank models and full-factorial orthogonal designs. Results: After 0.5 year, the timing of the gait cycle at self-selected speed was within the control group’s range and showed no significant asymmetry. With increasing speed, a decrease in knee joint range of motion was observed in the 0.5 year and 1-year groups, without achieving a full physiological increase in range of motion at long-term follow-up. Multivariate analysis revealed the greatest biomechanical imbalance during fast walking at one year and a phase-dependent effect of time after surgery, speed, and limb status on kinematics and EMG, particularly in the quadriceps. Conclusions: Basic temporal gait parameters during self-selected walking were within the control range by 0.5 year, but load-dependent knee kinematic and EMG abnormalities persisted. The knee joint’s response to increased loads remained impaired for at least one year. The persistence of phase-specific compensatory changes in kinematics and muscle activity at later stages can be assessed using exercise testing. Full article

This study proposes mechanical stress as a common integrative parameter that connects biological bone adaptation with engineering mechanics. In engineering, stress is defined as the internal reactive force per unit area within a loaded body; in clinical practice, its biological consequences can be observed on radiographs, CT, and MRI as callus formation, hypertrophy, or oedema, and perceived by the patient as localised pain. Three-dimensional geometry models were constructed in Autodesk Fusion and Inventor, and stress distributions were visualised using Abaqus finite element analysis. Representative clinical cases (n = 5) were drawn from the radiographic archive of Dubrovnik County Hospital. The analysis showed that regions of elevated stress predicted by finite element models corresponded spatially with areas of callus growth observed on clinical radiographs, and that the presence or absence of stress correlated with subjective pain reports. These findings suggest that stress may serve as a clinically and biomechanically relevant parameter bridging radiographic observation and engineering analysis of bone healing and remodelling. Full article

Background: Knee osteoarthritis (KOA) alters the performance of daily activities, such as stair negotiation, by compromising lateral stability and neuromuscular control. This pilot study aimed to evaluate the feasibility of a 10-week Dynamic Neuromuscular Stabilization (DNS) program and to explore its preliminary biomechanical effects during stair ascent and descent in middle-aged women with KOA. Methods: Twenty-six participants were randomly assigned to a DNS group (n = 13) or a control group (n = 13). The DNS group completed a 10-week intervention (twice weekly). Feasibility was assessed via recruitment, retention, and adherence. Primary outcomes were mediolateral (ML) center of pressure (COP) parameters, while secondary outcomes included anteroposterior (AP) COP parameters and lower limb range of motion (ROM). Effect sizes (η²_p) were estimated using 3D motion analysis and force plates. Results: The intervention showed high potential feasibility, with 100% recruitment and retention rates and 98.5% compliance. No adverse events occurred. Large effect sizes were observed for reduced ML COP velocity (ascent: η²_p = 0.79; descent: η²_p = 0.62) and RMS (descent: η²_p =0.16). Secondary outcomes, including AP COP parameters and joint ROM (increased sagittal flexion and decreased coronal instability), also demonstrated large effect sizes. Conclusions: This pilot study suggests that progressive DNS training appears to be feasible and safe for patients with KOA. The preliminary effect sizes observed in COP control and lower kinetic chain mechanics may serve as useful foundational data for designing future adequately powered clinical trials to further examine the efficacy and underlying biomechanical mechanisms of DNS training. Full article

Running velocity is an important methodological factor in footwear research, given its potential influence on biomechanical parameters used to evaluate shoe-specific effects. Since most previous studies have assessed footwear effects at standardized running velocities, it remains unclear whether shoe-specific biomechanical response patterns differ when runners transition to individually selected faster outdoor running velocities. Therefore, this study examined whether footwear-related biomechanical responses were modified by running velocity. Twenty-two runners completed outdoor running trials at two running velocities in seven running shoes differing in cushioning and midsole bending stiffness. Four commonly used inertial measurement unit-derived biomechanical parameters were assessed to determine whether shoe-specific responses differed between the two velocity conditions. Across all parameters, no significant shoe condition × running velocity interaction effects were observed. Higher running velocities increased the magnitude of the measured parameters, while the tested interaction terms did not provide statistical evidence that the relative shoe-related response patterns were systematically altered within the investigated velocity range. These findings suggest that individually preferred running velocities may be suitable for comparing relative shoe effects in field-based footwear testing for the investigated parameters and velocity range. Full article

Vertebral fractures are among the most common skeletal injuries and present significant clinical and biomechanical challenges, particularly in older adults and individuals with low bone density. Accurate prediction of vertebral mechanical response and failure under varying loading conditions is essential for improving understanding of spinal injury mechanisms. This study develops a density-dependent viscoelastic analytical model to predict the stiffness and fracture force of human vertebral specimens subjected to different compression rates. The vertebral body is represented as a composite structure consisting of a cortical shell and a trabecular core. Cortical bone is modeled as a linear elastic material, whereas trabecular bone is described using a Kelvin–Voigt viscoelastic formulation. Density-dependent constitutive relationships are incorporated for the elastic modulus and viscous coefficient of trabecular bone. Unknown material parameters are identified through optimization using the Nelder–Mead algorithm, based on experimental compression data from cadaveric vertebral specimens tested under quasi-static and dynamic loading conditions. The calibrated model reproduced the overall trend of specimen-to-specimen mechanical variation observed experimentally. Predicted stiffness values were in reasonable agreement with measured data. Fracture force predictions showed moderate agreement for dynamically tested specimens (R² = 0.60), which improved to R² = 0.88 after exclusion of one statistically identified outlier. Compared with a purely linear elastic formulation, the proposed viscoelastic model demonstrated modest improvement in stiffness prediction and more substantial improvement in fracture force prediction. These findings indicate that incorporating density-dependent viscoelastic effects improves representation of vertebral mechanical behavior, particularly at higher loading rates. Owing to its simplicity and computational efficiency, the proposed model requires only limited imaging input and may be useful for future biomechanical investigations, rapid screening, and injury risk prediction. Full article

Hydrotherapy is widely used in rehabilitation because it reduces mechanical loading while preserving neuromuscular and cardiovascular stimulation. However, the biomechanical characterization of deep-water running remains limited, particularly when using accessible wearable systems for cycle-based movement analysis. This study aimed to evaluate the concurrent validity and agreement of a low-cost accelerometry device for cycle-based analysis of deep-water running, using a commercial accelerometry system as the reference measurement system. Twenty-one healthy participants performed a 25 m deep-water running task with simultaneous data acquisition from mechanically coupled sensors to ensure alignment. A total of 75 synchronized cycles were processed using a standardized pipeline that included filtering, synchronization, cycle detection, and parameter extraction. Statistical analysis was conducted using the Wilcoxon signed-rank test, intraclass correlation coefficient, Spearman’s correlation, Bland–Altman analysis, and error metrics. The results showed good agreement for temporal and volumetric variables, including cycle duration (ICC = 0.84), cumulative acceleration (ICC = 0.82), and area under the curve (ICC = 0.68). However, lower agreement and systematic bias were observed for intensity-related variables, particularly RMS and peak acceleration, despite more than 92% of cycles falling within the 95% limits of agreement (LoA). These findings suggest that the proposed device provides acceptable agreement for temporal and volumetric variables during deep-water running and may represent a low-cost alternative for movement monitoring in aquatic environments. However, intensity-related variables should be interpreted with caution due to the systematic differences observed between systems. Full article

Objective: Patellofemoral pain syndrome (PFPS) is one of the most common causes of anterior knee pain and is associated with biomechanical, muscular, and functional impairments affecting the extensor mechanism of the knee. Quadriceps muscle dysfunction, altered tendon morphology, and impaired lower extremity biomechanics have been suggested to contribute to patellofemoral joint instability and pain development. The aim of this study was to evaluate the muscle and tendon thicknesses of the extensor mechanism using ultrasonography in individuals with PFPS and to investigate the relationship of these measurements with knee pain, knee function, and physical performance, with particular emphasis on the combined assessment of muscle morphology, tendon morphology, and functional performance parameters. Methods: This cross-sectional study was conducted between 5 November 2019 and 15 December 2019, including 80 individuals aged 18–45 years who presented with anterior knee pain and were clinically diagnosed with patellofemoral pain syndrome (PFPS). Demographic characteristics of the participants were collected. Pain severity was assessed using the Visual Analog Scale (VAS), and functional status was evaluated with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Physical performance was assessed using the 6 m walk test and the five-repetition sit-to-stand test. Ultrasonographic examination was used to measure rectus femoris muscle thickness, vastus intermedius muscle thickness, quadriceps tendon thickness, and patellar tendon thickness using a high-frequency linear probe in a standardized supine position with the knee relaxed and the lower extremity muscles at rest. Results: The mean age of the participants was 32.11 ± 7.08 years, and the mean body mass index (BMI) was 25.05 ± 4.11 kg/m². Of the participants, 42 (52.5%) were male and 38 (47.5%) were female; 46 (57.5%) were smokers and 34 (42.5%) were non-smokers. Ultrasonographic measurements showed that rectus femoris muscle thickness was 1.98 ± 0.45 cm, vastus intermedius muscle thickness was 1.75 ± 0.53 cm, quadriceps tendon thickness was 0.54 ± 0.12 cm, and patellar tendon thickness was 0.35 ± 0.08 cm. Rectus femoris, vastus intermedius, and quadriceps tendon thicknesses were significantly higher in males compared to females (p = 0.001). Individuals with BMI > 25 had greater rectus femoris (p = 0.023) and vastus intermedius (p = 0.001) muscle thicknesses. A negative correlation was found between rectus femoris muscle thickness and WOMAC total (r = −0.227, p = 0.042) and WOMAC pain scores (r = −0.233, p = 0.028). Additionally, a significant relationship was observed between quadriceps tendon thickness and the five-repetition sit-to-stand test (r = −0.247, p = 0.044). Conclusions: In patients with PFPS, quadriceps muscle and tendon thicknesses were found to be associated with certain demographic and clinical parameters. Ultrasonographic evaluation of muscle and tendon structures may be a useful, non-invasive, dynamic, and radiation-free method for better understanding the clinical characteristics of PFPS and its relationship with physical performance. Ultrasonographic assessment may also provide complementary information for rehabilitation planning and functional evaluation in individuals with PFPS, although these findings should be interpreted cautiously because of the cross-sectional design and weak correlations observed. Full article

Objective: To evaluate the clinical outcome, safety and efficacy of the APrevent Vocal Implant System (VOIS) in patients with unilateral vocal fold paralysis (UVFP), with particular emphasis on the timing and impact of postoperative saline adjustments. Methods: This retrospective−prospective longitudinal study included 11 patients with chronic UVFP who underwent VOIS medialization thyroplasty (MT) under local anesthesia (n = 2) and general anesthesia (n = 9). Multidimensional voice parameters were analyzed preoperatively and at 1, 3, 6, and 12 months postoperatively. Statistical analyses included the Friedman test for repeated measures and the comparison of outcomes between pre- and each postoperative timepoints was evaluated with the Wilcoxon signed-rank test. Results: Significant and sustained improvements were observed across all multidimensional voice parameters. Mean mVHI-10 decreased from 31.7 ± 4.5 preoperatively to 5.8 ± 5.1 at 12 months, while mean MPT increased from 7.1 ± 3.8 to 14.4 ± 4.5 s (p < 0.05, r > 0.7). Acoustic parameters, including jitter, shimmer, and NHR, demonstrated progressive improvement over 12 months. A high proportion of patients (72.73%) underwent postoperative saline adjustment at a mean interval of 6.23 ± 1.23 months, beyond the early postoperative edema phase, with each adjustment yielding further enhancement in voice outcomes. No major complications, including airway obstruction or hematoma, were observed. Conclusions: VOIS MT is safe and effective, providing sustained improvements in multidimensional voice outcomes. The ability to perform postoperative saline adjustments enables dynamic optimization of glottal closure, reducing the need for revision surgery and addressing evolving laryngeal biomechanics. These findings support VOIS as a flexible, adjustable alternative to static medialization techniques and provide dynamic voice optimization in patients with UVFP. Full article

This systematic review examined the validity and reliability of wearable inertial sensor systems to quantify spatiotemporal gait parameters in post-stroke adults, a population in which gait asymmetry and altered motor control challenge accurate measurement. Sixteen studies involving 300 participants were included. Spatial parameters gait speed, cadence, and step/stride length showed consistently good-to-excellent agreement with reference systems (ICC 0.85–0.98; 95% LoA ±0.03–0.08 m/s for gait speed, ±4–10 steps/min for cadence, and ±3–8 cm for step/stride length) and high test–retest reliability. Temporal parameters demonstrated greater heterogeneity, with larger errors and lower concordance (ICC 0.40–0.85; LoA ±0.04–0.12 s), particularly for swing time (ICC 0.40–0.70; LoA up to ±0.15 s). Paretic-side measurements showed 10–20% lower concordance and 30–50% wider limits of agreement compared with the non-paretic side, although within-subject reliability remained moderate to high. No consistent influence of sensor number on measurement accuracy was observed. Overall, wearable inertial sensors provide robust estimates of spatial gait parameters, whereas temporal outcomes especially swing time remain limited due to challenges in gait event detection under stroke-related biomechanical alterations. These findings highlight the need for standardized protocols and improved algorithms to enhance comparability across studies and support broader clinical adoption. Full article