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Abstract:Multibody dynamics simulation of the musculoskeletal system is an essential tool for analyzing the biomechanical mechanisms underlying human motion. Recent research trends have shifted from traditional physics-based models toward data-driven or data-physics hybrid frameworks. This review presents the latest developments in these areas. Physics-based multibody dynamics simulations have undergone significant progress in terms of simulation fidelity, optimization algorithms, and software tools. However, their practical implementation remains constrained by the need for complex experimental data and the computational expense of solving differential equations. Conversely, data-driven methods bolstered by advancements in deep learning have demonstrated remarkable efficiency in predicting joint angles, postures, ground reaction forces, joint torques, and muscle forces, as well as developing control algorithms for exoskeletons. However, despite these advantages, data-driven approaches face challenges such as limited generalizability and potential violation of biomechanical principles.To address these limitations, data-physics hybrid approaches (e.g., physics-informed neural network, PINN) which integrate physical constraints (e.g., Newton-Euler equations, muscle constitutive laws) with data-driven architectures have been developed. This synergy enhances prediction accuracy while preserving the biological plausibility of solutions. Nevertheless, critical challenges persist, including the integration of multi-scale physical equations and the modeling of multi-joint coordination dynamics. Future research should prioritize: optimizing hybrid model architectures to balance computational efficiency and mechanistic accuracy, incorporating markerless motion capture techniques to improve real-world applicability, exploiting multi-scale physics and personalized parameter inversion to advance precision rehabilitation and motion analysis. These efforts will foster innovations in intelligent rehabilitation systems, clinical motion assessment, and related translational fields.

Abstract:Motor dysfunction seriously affects people’s quality of life, and currently is one of the main health problems facing mankind. Sports and rehabilitation biomechanics focuses on motor dysfunction, providing the theoretical basis for motor function assessment, dysfunction intervention technology and equipment development. In 2024, the biomechanical research of motor dysfunction achieved fruitful results. From 3 aspects, namely, non-contact assessment of motor function, intelligent classification and grading of dysfunction, and neurobiomechanical mechanism of motor dysfunction, this review summarizes the research progress in the past year and discusses the future development direction.

Abstract:Objective To explore the electroencephalography (EEG) characteristics of patients with knee osteoarthritis (KOA) which are different from those of healthy subjects during dynamic balance tests, and study the connection and influence between brain activity and KOA. Methods: Fifteen patients with KOA and 17 healthy subjects performed the timed up to go test (TUGT) and 5-times sit to stand test (5STS) . The EEG characteristics of the 4 frequency bands, namely δ (0.5–4 Hz), θ (4–8 Hz), α (8–14 Hz) and β (14–30 Hz)?of 9 electrodes including CZ, C3, C4 in the central lobe, PZ, P3, P4 in the parietal lobe, and OZ, O1, O2 in the occipital lobe of the cerebral cortex of the subjects were recorded. Time and frequency domain analysis were conducted. Results During 5STS, the time-domain amplitudes of electrodes C4, P3, and P4 in the δ band, electrodes C4, P3, and P4 in the θ band, and electrodes P3 and P4 in the β band of KOA patients were significantly higher than those of healthy subjects (P<0.05); the power of electroencephalogram signals of electrodes P3, P4, and O2 in the β band was significantly higher than that of healthy subjects. During TUGT, except that the time-domain amplitude of electrode PZ in the θ band of KOA patients was significantly lower than that of healthy subjects (P<0.05), there was no significant difference in all electrodes in other frequency bands; the power of electroencephalogram signals of electrodes C3, CZ, C4, PZ, P4, O1, OZ, O2 in the δ band and electrodes CZ, P3, PZ, and OZ in the α band and electrodes CZ, P4, OZ, and O2 in the β band was significantly lower than that of healthy subjects (P<0.05). Conclusions Compared with healthy subjects, the activity in the parietal lobe area of the brain of KOA patients during 5STS was stronger, while the brain activity in the central lobe, parietal lobe, and occipital lobe areas of KOA patients during TUGT was weaker than that of healthy subjects. This study may provide some references for clinicians in the prevention and treatment of KOA.

Abstract:Objective The isokinetic muscle strength indicators and surface electromyography (sEMG) signals of the healthy side lower limb of patients with non-contact anterior cruciate ligament injury (ACLD) in the acute phase were compared with those of healthy individuals, so to provide a theoretical basis for the prevention of secondary ACL rupture in the healthy side lower limb of ACLD patients. Methods 21 patients with ACLD in the acute phase (ACLD group) and 21 healthy individuals (control group) were subjected to isokinetic muscle strength tests for hip flexion, extension, adduction, abduction, and knee flexion, and sEMG signals of the vastus medialis, vastus lateralis, semitendinosus, biceps femoris, and gluteus maximus were collected during the single-leg jumping movements. The differences between the two groups in relative peak torque, antagonist muscle ratio, root mean square amplitude, and co-contraction index were analyzed by independent sample t-test. Results The extension of the knee (P=0.040) and hip flexion strength (P=0.041) were lower in the healthy side lower limb of ACLD patients. In the single-leg landing action, there were lower activation of the vastus medialis muscle in the pre-activation phase (P=0.014), lower activation of the vastus medialis (P=0.010) and gluteus maximus (P=0.002) in the reaction phase, and also lower co-activation levels of the biceps femoris-semitendinosus (BF-ST) (P=0.020). Conclusions At the early stage of injury, the function of the healthy side lower limb of ACLD patients changes, which may indicate why ACLD patients face a greater risk of contralateral lower limb injury.

Abstract:Objective To investigate the dynamic features of patients with patellofemoral pain (PFP) during running by using support vector machine (SVM) classifier and feature selection methods, so as to provide theoretical support for the prevention and rehabilitation of PFP. Methods An SVM classification model was used to classify healthy individuals (n=13), PFP patients with long-term disease course (n=13), and PFP patients with short-term disease course (n=10) based on their dynamic features during running. The most effective minimum feature set was selected through feature selection methods. Results The accuracy rate of the constructed classification model was 83.3%. The minimum feature set selected contained 3 key features. PFP patients with short-term disease course showed a delay in the appearance of impact valleys and active peaks, while PFP patients with long-term disease course showed a lower impact peak-valley slope. Conclusions PFP patients with short-term disease course mainly showed a prolonged shock absorption process and a delayed propulsion action, while PFP patients with long-term disease course showed the most significant feature of having a lower vertical reaction force impact peak-valley slope. These features revealed the specific characteristics of PFP at different stages of the disease, providing a basis for developing individualized rehabilitation programs.

Abstract:Objective To analyze the effects of different sensory integration tasks on biomechanical characteristics of the lower limbs during walking in female patients with patellofemoral pain (PFP), and exlpore the relationship between these characteristics and patellofemoral joint stress (PFJS), so as to provide a reference for the prevention of PFP recurrence. Methods A total of 36 female patients with PFP were recruited for the study, and kinematic and kinetic data were collected while the subjects were walking. The effects of baseline, tactile integration task, listening integration task and visual integration task, on lower limb biomechanical characteristics was evaluated through the use of one-way ANOVA. Pearson correlation analysis was used to analyze the relationship between the above biomechanical characteristics and PFJS. Results Compared to the baseline, step length (P=0.004) and cadence (P=0.001) were significantly reduced in patients with PFP when performing the listening integration task. Furthermore, both variables exhibited a negative correlation with PFJS. Both the hip internal rotation angle (P=0.001) and the ankle internal rotation angle (P=0.022) were significantly increased in tactile integration task. Furthermore, the aforementioned metrics were significantly and positively correlated with PFJS (hip internal rotation angle: P<0.001; ankle internal rotation angle: P<0.001). The hip internal rotation angle (P=0.001), knee flexion angle (P=0.019), ankle inversion angle (P=0.003), and ankle plantarflexion angle (P=0.048) were increased in patients with PFP performing the visual integration task. These biomechanical characteristics exhibited a positive correlation with PFJS (P<0.050). Conclusions The listening integration task decreases step length and cadence in patients with PFP, and the tactile and visual integration tasks increase hip internal rotation angle and ankle internal rotation angle. On this basis, the visual integration task also increases the knee flexion angle and ankle plantarflexion angle during walking. Overall, it appears that the visual integration task has the greatest effect on gait biomechanics in female patients with PFP, and changes in these biomechanical characteristics are associated with elevated PFJS.

Abstract:Objective To investigate the immediate impact of changes in kinematic and dynamic characteristics before and after visual intervention on the gait of hemiplegic patients. Methods Thirty visually normal hemiplegic patients were recruited. Plane mirrors (0°), concave lenses (+150°, +450°) were selected to simulate normal vision, moderate myopia, and high myopia scenarios for straight line walking tests. The Qualisys three-dimensional (3D) motion capture system and Kistler 3D force platform were employed to collect kinematic and dynamic parameters of the patients, and the differences in related indicators before and after visual intervention were compared. Results Visual intervention affected the step length, walking speed, and joint angles of hemiplegic patients. Especially after acute vision changes, there was a significant difference in the stride length and ankle joint angles on the patient’s affected side. Under high myopia, the step length and step length symmetry were better than those under moderate myopia, but at the expense of gait speed. Visual intervention led to asymmetric trends in step the length symmetry and joint angle symmetry. There were very significant differences in center of pressure (COP) and COP symmetry between normal vision and high myopia. Conclusions Acute vision changes can significantly affect the gait of hemiplegic patients, especially when there is a notable decrease in walking speed and changes in ankle joint angles with high myopia, and an increase in walking speed with moderate myopia. Additionally, under all conditions of vision changes, the COP symmetry is reduced, indicating a higher risk of falls. During the rehabilitation process of hemiplegic patients, reasonable vision assessment and corresponding intervention measures are expected to improve walking ability and life quality of the patients.

Abstract:Objective To explore the differences in muscle synergies of healthy individuals, intact limbs and residual limbs of above-knee amputees under different gaits, provide references for electromyographic control of the prosthetics. Methods Surface electromyography (sEMG) signals of 7 muscles (4 thigh muscles, 3 calf muscles) were collected from 7 healthy individuals and 3 lower-limb amputees during walking, ascending/descending slopes, and ascending/descending stairs. Muscle synergy weights (W) and temporal activation coefficients (H) were extracted using concatenated non-negative matrix factorization (CNMF). The weight matrices were compared using the coefficient of determination R2, and the activation coefficients were analyzed using statistical parametric mapping (SPM). Furthermore, peak activation and activation integral were used for hierarchical clustering analysis. Results The comparison of W matrices indicated a similar set of muscle synergies between the healthy group and the intact limb of amputees, whereas the residual limb showed greater variability in synergies. The analysis of H showed statistically significant differences in muscle activation throughout the gait cycle for all amputees. Clustering of time-domain features revealed that amputees exhibited higher activation integral and peak values in their intact limb during ascending slopes. Conclusions This study provides an in-depth investigation of the neuromuscular compensation strategies in lower-limb amputees under different gaits, offering theoretical insights for gait rehabilitation and assisting in the development of EMG-controlled prosthetics.

Abstract:Objective To investigate how interference from motor and cognitive tasks affects the postural stability of older adults during stair descent. Methods A total of elderly subjects were recruited. Using the Vicon infrared motion capture system and Kistler force plate, the kinematic and dynamic data were collected simultaneously during stair descent under three conditions: single task (ST), motor task (MT), and cognitive task (CT). Dynamic stability of the body during stair descent was assessed using the margin of stability (MoS) algorithm. Repeated measures ANOVA was applied to compare differences across conditions. Results Compared to the ST condition, both step speed (P<0.001) and step frequency (P<0.001) were significantly reduced under MT and CT conditions. Step length (P=0.037) was also significantly reduced under the CT condition compared to those under the ST condition. In the aspect of anterior-posterior dynamic stability, compared to the ST condition, centroid velocity (P<0.001) and extrapolated centroid position (P<0.001) were significantly increased, while MoS (P<0.001) was significantly decreased under both MT and CT conditions. In comparison to the CT condition, centroid displacement (P=0.011) and velocity (P=0.014), as well as extrapolated centroid position (P<0.001), were significantly greater those under the MT condition. In the aspect of medial-lateral dynamic stability, compared to the ST condition, centroid displacement (P<0.001) was significantly reduced under MT and CT conditions Additionally, the extrapolated centroid position (P=0.001) was significantly reduced, and MoS (P=0.038) was significantly increased under the MT condition compared to those under the ST condition. Conclusions Older adults adjust their gait in response to dual-task interference during stairs descent by ‘slowing down step speed, reducing step frequency, and shortening step length’. This adjustment helps maintain medial-lateral dynamic stability, but significantly decreases anterior-posterior dynamic stability, thereby increasing the risk of falls.

Abstract:Objective To investigate the gait characteristics of school-age children with generalised joint hypermobility (GJH). Methods The kinematic and kinetic data of lower extremity joints in 56 children with GJH and 56 healthy children were collected by 3D motion capture system and 3D force plates, and the differences between the two groups were compared and analyzed. Results Kinematics parameters: the mean ankle inversion angle(P=0.000),maximum hip adduction angle (P=0.002) and maximum foot clearance angle (P=0.004) in stance phase decreased in the GJH children group, while the mean foot progression angle (P=0.000), the maximum foot internal rotation angle(P=0.000) in stance phase, and the knee flexion angle (P=0.032) in the middle stance phase increased. Kinetics parameters: the maximum power of knee (P=0.005), and hip(P=0.000), joints and the maximum inversion moment of ankle joints (P=0.009)in stance phase decreased in GJH children group. Temporal and spatial parameters: the step length (P=0.001), walking velocity (P=0.000), and cadence (P=0.000) decreased in GJH children group, while the stance phase percentage(P=0.000), and step width(P=0.000) increased. Conclusions There is a decrease in walking efficiency and balance stability of children with GJH. The line alignment is abnormal in ankle joint. The knee joint function needs long-term attention.

Abstract:Objective To investigate the effects of strength training and flexibility training on the strategy of crossing obstacles for the elderly women and the risk of tripping over obstacles. Methods Twenty five elderly women were randomly divided into strength training group (n=13) and flexibility training group (n=12), and received corresponding intervention training for 12 weeks. The kinematics data of obstacle crossing were collected using an infrared three-dimensional (3D) motion capture system before and after training. Results Both strength training and flexibility training could significantly improve the gait speed (P=0.033), stride length (P=0.020) and toe distance (P=0.014) during 25 cm obstacle crossing. The interactive effect of training and time was significant for the crossing height (15 cm：P=0.025；25cm：P=0.019). The interactive effect of training and time was significant for the margin of stability (MOS)in the internal-external direction during 25 cm obstacle crossing (P＜0.05). The minimum MOS in the first single support period (P=0.046) and the MOS at the time when the toe crossed directly above the obstacle (P=0.043) in strength training group were significantly increased. Conclusions Both strength training and flexibility training can improve the spatiotemporal characteristics of the elderly women during obstacle crossing. Compared with flexibility, muscle strength is the most important reason that restricts the crossing height of the elderly women. Strength training can effectively reduce the risk of tripping over obstacles by improving the crossing height and dynamic stability of elderly women.

Abstract:Objective To evaluates the effects of cross-balance training on knee function, dynamic balance, and rectus femoris (RF) activation in patients after anterior cruciate ligament reconstruction (ACLR). Methods Forty ACLR patients at 5–6 week after operation were randomly divided into experimental group and control group. The experimental group received the cross-balance training on the basis of the standard rehabilitation, while the control group received only standard rehabilitation. Knee function was assessed with the Lysholm score, dynamic balance, and root mean square (RMS) of RF surface electromyography. The correlation between RMS and dynamic balance was also examined. Results After intervention, the Lysholm score of the experimental group was significantly higher than that of the control group (P<0.01). Regarding balance function, both the gait line length and single support line length of the experimental group were significantly greater than those of the control group (P<0.01). Conversely, mediolateral displacement of the experimental group was significantly lower than that of the control group (P<0.01). Furthermore, the RF RMS of the experimental group was significantly larger than that of the control group (P<0.01). The RF RMS was positively correlated with the gait line length and single support line length, whereas it was negatively correlated with the mediolateral displacement (P<0.05). Conclusions Cross-balance training significantly enhances knee function, dynamic balance, and RF activation in post-ACLR patients, supports the theory of cross-education. This study shows that cross-balance training has certain application values in ACL postoperative rehabilitation.

Abstract:Objective To determine the effect of Tai Chi practice on balance control ability of the individuals with functional ankle instability (FAI) in single-leg stance, and further observe the augmented effect from attention focus on ankle. Methods A total 46 individuals with FAI were randomly divided into ankle focus group, free focus group and control group. The ankle focus group and FFG performed Tai Chi practice for 10 weeks; the ankle focus group focused their attention on the ankle joint, while the free focus group didn’t require attention focus; the control group maintained the origin lifestyle and didn’t engage in special physical activities. The three-dimensional force plate and Y balance test (YBT) were used to evaluate the static (with eyes open and closed) and dynamic (instant and continuous) balance ability of individuals with FAI. Results For ankle focus group and free focus group, the anterior-posterior (AP) and medial-lateral (ML) sway distances of center of pressure (COP) in single-leg stance (SLS) with eyes open and closed were significantly reduced, and the reach distance in YBT in three directions were increased. For the ankle focus group, the medial lateral stability index and the dynamic postural stability index were significantly reduced during single-leg drop landing. The ankle focus group and free focus group got significantly smaller ML COP sway distance than control group in SLS with eyes open; the ankle focus group got significantly smaller ML COP sway distance than free focus group and control group in SLS with eyes closed; and reach distance of ankle focus group in posterior-medial & posterior-lateral direction in YBT was longer than of free focus group and control group. Conclusions Tai Chi practice can comprehensively improve static and dynamic balance control ability of the individuals with FAI in SLS, and ankle attention-focused Tai Chi practice is more effective, especially for the enhancement of their medial-lateral control ability in closed-eye static and continuous dynamic SLS.

Abstract:Objective To observe the differences in dynamic stability and kinematic and kinetic characteristics of the lower limbs between patients with knee osteoarthritis (KOA) and healthy individuals at the begining stage of practicing Tai Chi Yunshou movement. Methods Thirty Tai Chi beginners, including 15 patients with KOA and 15 healthy controls, were recruited to practice Tai Chi Yunshou movement for two hours under the guidance of a Tai Chi expert. A motion capture system and a three-dimensional force platform were used to collect and calculate dynamic stability parameter as well as kinematic and kinetic parameters of the left lower limb during the Yunshou movement. Results Compared with healthy controls, patients with KOA demonstrated a smaller center of mass (COM)-center of pressure (COP) inclination angle, reduced mean and peak ankle dorsiflexion angle, reduced peak hip adduction angle and increased peak knee flexion moment during the Yunshou movement (P<0.05). Conclusions Patients with KOA use adaptive postural strategies to maintain the lateral stability in Tai Chi Yunshou exercise, but a comprehensive training programme should be recommended to reduce the joint loading during flexion of the lower limbs at the benginning stages of this exercise.

Abstract:Objective To explore the effect of bionic electrical stimulation (BES) combined with resistance tightening leg training on postpartum pelvic floor dysfunction (PFD). Methods A total of 205 patients with PFD were divided into BES group (n=102) and the combined group (n=103) by random number table method. All of them received routine pelvic floor muscle training. In addition, the BES group was treated with BES intervention, and the combined group was treated with BES combined with resistance tightening leg training, with 8 weeks of treatment. The classification of pelvic floor muscle strength, electrophysiological indexes of pelvic floor function, urodynamics and stress urinary incontinence (SUI) classification/pelvic organ prolapse (POP) degree were compared between the two groups before and after treatment. Results After treatment, the pelvic floor muscle strength classification, SUI classification and POP degree in the combined group were significantly better than those in BES group (P< 0.05). After treatment, ClassⅠ/ ClassⅡmuscle fiber fatigue, vaginal dynamic pressure and maximal electromyography (EMG) value of fast muscle in the combined group were (-1.20±0.35)%, (-0.90±0.30) %, (76.30±5.51) cmH2O, (43.00±5.82) μV, respectively, which were all significantly higher than those in BES group (P<0.05). After treatment, the indexes of urodynamics in both groups were significantly improved, and the combined group was better than the BES group (P<0.05). Conclusions BES combined with resistance tightening leg training can significantly improve pelvic floor muscle strength, muscle fiber fatigue and urodynamics in patients with PFD, thus alleviating SUI/POP symptoms.

Abstract:Objective A Cobb angle prediction model for adolescent idiopathic scoliosis (AIS) based on three-point mechanical data from three-dimensional (3D)-printed orthotics and various machine learning algorithms was developed, so as to provide an innovative, radiation-free method for early clinical screening and monitoring of AIS. Methods Clinical data from AIS patients and mechanical data from 3D-printed orthotics were collected to construct a comprehensive dataset with features such as gender, age, disease type, weight, and Risser score. Six algorithms, namely, random forest, support vector regression, gradient boosting regressor, extreme gradient boosting, lightgbm, and catboost, were used to construct and evaluate the performance of Cobb angle prediction models. Results The gradient boosting regressor model had the best performance on several evaluation metrics, achieving a precision rate of 0.937, recall rate of 0.818, F1-score of 0.949, and an area under curve (AUC) value of 0.843. In the validation set, the model’s predictions reached an accuracy rate of 0.942, fitting well with the actual Cobb values. Conclusion The Cobb angle prediction model based on mechanical data and machine learning effectively avoids the radiation risks associated with traditional full-spine X-ray examinations in early clinical screening. It provides a non-invasive assessment for AIS patients, enhancing the safety and efficiency of screening and monitoring, and offering a powerful decision-making tool for clinicians, with a great clinical significance.

Abstract:Objective To investigate the effect of orthosis design parameters on correction of scoliosis and orthosis-trunk interface pressure. Methods A finite element model of scoliosis was constructed to simulate the assembly effect of the orthosis. The orthosis was divided into four loading areas (left rib, right rib, anterior-left and posterior-right area) to simulate six modification conditions. In Models 1, 2 and 3, a fixed modification of 20 mm was applied on the anterior left and posterior right areas, while the displacement loads of 20, 25 and 30 mm were applied on both the left rib and right rib areas. In Models 4, 5 and 6, a fixed modification of 25 mm was applied on left rib and right rib areas, with the displacement loads of 15, 20 and 25 mm applied on both anterior left and posterior right areas. The Cobb angle, apical vertebral rotation (AVR) and interface pressure were calculated. Results The correction of Cobb angle in Models 1, 2 and 3 was 8.94°, 15.62° and 17.91°, respectively, with AVR correction of 7.53°, 6.69° and 5.87°, respectively. In Models 4, 5 and 6, the correction of Cobb angle were 14.55°, 15.62° and 16.09°, with AVR correction of 5.25°, 6.69° and 8.63°, respectively. In Model 6, the correction rate of Cobb angle and AVR were 45.48% and 41.22%, respectively, with a maximum pressure of 26.51 kPa on orthosis-trunk interface, achieving the most significant outcome. Conclusions The modification of orthosis has a significant effect on the correction of Cobb and AVR angles. The loading on the left rib and right rib areas mainly affect the Cobb angle, while the loading on anterior left and posterior right areas mainly affect the spinal axial-rotation. A modification of 25 mm on all loading areas achieves the optimal spinal correction. This study provides the quantitative data for orthosis design.

Abstract:Objective In response to the clinical needs for personalized wrist orthoses, a topological optimization design method was proposed to achieve an integrated macro- and micro-structural optimization of a personalized, lightweight, and comfortable wrist orthosis. Methods A composite biomechanical finite element model of the wrist orthosis and upper limb was established to quantify the effects of the orthosis geometry on its fixation performance and comfort. A multi-condition topological optimization and microstructure design approach was employed to optimize the non-load-bearing areas of the orthosis. The orthosis was manufactured using three-dimensional (3D)-printed polyether ether ketone (PEEK), and the feasibility of the design was validated. Results While maintaining mechanical strength, the weight of the 3D-printed PEEK orthosis was reduced by 28% compared to the traditional orthoses. Both the pressure at the skin contact interface and the results of a subjective questionnaire indicated that test subjects experienced a high level of comfort wearing the orthosis. Conclusions The orthosis design achieved personalization, lightweight structure, and high comfort while ensuring mechanical strength and fixation performance.

Abstract:Objective To conduct the biomechanical analysis on a new power-assisted knee orthosis. Methods A self-force source power-assisted knee orthosis was used, and four motions (level walking, sitting and standing, ascending and descending stairs) were measured before and after wearing the orthosis. A musculoskeletal multibody dynamic model was adopted to calculate the joint angles and pressures at the knee, patellofemoral and hip joints. The effects of power-assisted knee orthosis on biomechanical changes of lower limbs were investigated by comparing the joint angles and pressures before and after wearing it. Results The orthosis would reduce the knee joint angle during level walking, as well as the knee joint pressures during sitting and standing on the wearing side. Wearing the orthosis did not significantly affect the joint angles during sitting and standing; however, it led to a significant decrease in joint pressures at both bilateral knee joints and patellofemoral joint. During ascending and descending stairs, the knee joint angle on the wearing side was opposite to that on the non-wearing side. The maximum increase of the knee joint angle was (14.3±3.6)%. Conclusions The power-assisted knee orthosis can offer a conservative treatment for individuals with various knee diseases by reducing joint angles and pressures in daily motions.

Abstract:Objective To explore the role of Piezo2 in venous vascular smooth muscle cell (VSMC) dysfunction and neointimal hyperplasia following exposure of veins to an arterial mechanical environment, and elucidate its potential role in venous restenosis after coronary artery bypass grafting (CABG) and arteriovenous fistula (AVF) surgery. Methods Based on transcriptomic datasets, differentially expressed genes between AVF or grafted veins with normal veins were analyzed using GEO2R and GO. Immunofluorescence was used to detect expression of Piezo2 in two AVF clinical samples. FX-5000TM cyclic stretch application system was used to apply 1.25 Hz stretch with 15% amplitude to VSMCs to simulate arterial conditions in vitro. The protein expressions of Piezo2, SM22 (VSMC phenotypic marker), and PCNA (proliferation-related molecule) were measured with Western Blot. Calcium-free medium was further used to remove extracellular Ca2?, and the effect of Ca2? on stretch-induced changes in related molecules were analyzed. Results Transcriptomic analysis revealed that Piezo2 was upregulated in AVF and grafted veins compared to normal veins. Immunofluorescence showed the increased protein expression of Piezo2 in AVF tissues compared to normal veins. Notably, in the neointimal tissue of AVF samples, Piezo2 was significantly upregulated, while SMA was downregulated. In vitro, 15% cyclic stretch upregulated Piezo2 and PCNA expression but downregulated SM22 expression, which suggested a phenotypic switch of venous VSMCs from the contractile phenotype to the synthetic phenotype. Removal of extracellular Ca2? partially reversed the stretch-induced VSMC phenotypic switch and proliferation. Conclusions After veins exposed to an arterial mechanical environment, the upregulated Piezo2 may induce neointimal hyperplasia by promoting VSMC phenotypic switch. This study may provide mechanobiological insights and potential therapeutic targets for the prevention and treatment of venous restenosis following CABG and AVF surgeries.

Abstract:Objective To study the effects of different clearance conditions (equal upper and lower axial clearance, change of upper/lower axial clearance, axial displacement of blades) on efficiency and hemolysis performance of blood pump. Methods The blood pumps under three kinds of clearance conditions were numerically simulated by computational fluid dynamics. Results For efficiency, when the upper and lower axial clearance was equal, the lower axial clearance was unchanged and the upper axial clearance was reduced, the efficiency of blood pump could be improved by 0.85%, 1.71% and 2.90%, respectively. While the upper shaft clearance remained unchanged, the lower shaft clearance was decreased by 1.18%. For hemolysis, the increase of the clearance can reduce the hemolysis index (HI) under the first two clearance conditions, while the axial migration of the blade wheel would increase the HI. When the upper axial clearance was unchanged and the lower axial clearance was 0.3 mm, the HI was the largest, which was . When the upper and lower axial clearance was 0.7 mm, the HI was the smallest, which was . Conclusions Improving blood pump clearance is helpful to optimize the performance of blood pump. This study can provide some references for the design and optimization of interstitial structure of blood pump.

Abstract:Objective To measure the three-dimensional (3D) motion of the knee joint in healthy people and patients after total knee arthroplasty (TKA). Methods The coordinate system for the tibia and femur of the knee joint was established, and the marking points were pasted at the bone landmarks. Then the 3D motion of human knee joint was measured by biplane high-speed photogrammetry, and the data were processed according to the coordinate transformation. Results The peak values of adduction and abduction, internal and external rotation, internal and external translation, and proximal and distal movement of the artificial knee joint were larger than those of the healthy knee joint (P<0.05), but there was no statitistic difference in posterior displacement between the artificial and healthy knee joints (P=0.05). Conclusions By measuring the knee joint motion, not only the difference in knee joint motion between the healthy volunteers and TKA patients was revealed, but also the effectiveness of biplane high-speed photography in knee joint kinematic measurement was demonstrated.

Abstract:Objective To enhance the mechanical properties of trichiral honeycomb sandwich structures and satisfy the design criteria for vertebral implant structures. Methods A chiral-like honeycomb sandwich structure with an auxiliary support structure was constructed for optimal design. The finite element method was used to study the influence of the auxiliary support structure on the chiral-like honeycomb sandwich structure and the relationship between the support position and mechanical property parameters. Furthermore, the influence of the deformation mechanism of different structures on mechanical properties was discussed. Results All chiral-like honeycomb sandwich structures exhibited enhanced mechanical properties in comparison to trichiral honeycomb sandwich structures. The mechanical properties of the chiral-like honeycomb sandwich structure with the auxiliary support structure positioned perpendicular to the ligament were optimal, and this position represented the optimal support position. When the volume was used as a control variable, the compressive stiffness, stiffness-to-mass ratio, and transverse strain of the chiral-like honeycomb sandwich structure in the direction were significantly correlated with the change of the support position, and all of them were positively correlated. Conclusions As a novel chiral-like honeycomb structure, it provides a biomechanical basis for the optimal design and clinical application of honeycomb sandwich structures as vertebral implant structures.

Abstract:Objective To investigate the biomechanical characteristics of Salto Talaris tibial components with different heights at the bone-prosthesis interface during different gait support phases after total ankle replacement. Methods An ankle joint model was reconstructed using a weight-bearing CT from a 61-year-old female patient with ankle arthritis, and Salto Talaris tibial components with different heights (5, 7, 9, 11 mm) were modelled to simulate the loading of the tibial-prosthesis during four gait support phases, and to analyse the micromotion and stresses at the bone-prosthesis interface. Results The 11 mm and 9 mm models had a poorer prosthesis stability, with the peak micromotion exceeding 50 μm and the peak internal tibial stresses of 30.75 MPa and 29.86 MPa, respectively, which exceeded the yield stress of the cancellous bone. The tibial stresses of the 7 mm and 5 mm models were within reasonable ranges and the average peak micromotions were only 42.66 μm and 40.32 μm. In contrast, the initial stability of the 5 mm model prosthesis was the best. Conclusions For total ankle replacement with Salto prosthesis, the height of the tibial component should be chosen appropriately, and the optimal height was about 5 mm. Excessive flexion and extension activities of the ankle joint should be avoided to maintain the stability of the prosthesis after surgery. This study provides a theoretical basis for the improvement of the structural parameters of the Salto prosthesis, which is valuable for the selection of clinical surgical prostheses and helps to improve the results of total ankle replacement.

Abstract:Objective To investigate the compressive relaxation behavior of cartilage in different regions of the knee joint at different strain rates, and construct the viscoelastic mechanics of cartilage in each region, so as to provide a reference for the prevention of cartilage-related diseases and the development of cartilage repair materials. Methods The knee cartilage of beagle dogs was regionally divided, and the uniaxial unconfined compressive relaxation properties of cartilage in each region were tested by a universal testing machine at different strain rates, and the constitutive models were constructed. Results The cartilage exhibited a notable stress attenuation. Furthermore, the normalized stress reduction increased significantly with increasing strain rate. For cartilage in lateral plateaus of tibia, the normalized stress reduction at strain rate 5×10-4 s-1 was 19%, and increased to 69% at strain rate 5×10-2 s-1. The relaxation equilibrium stress remained relatively constant at all strain rates. The Ogden-Prony viscoelastic model of cartilage in each region was developed with a goodness of fit R2>0.98. Conclusions The knee cartilage demonstrates a significant viscoelastic response in relaxation tests, exhibiting the rate-dependent and region-dependent properties. The Ogden-Pony viscoelastic model can reflect the strain rate-dependent stress relaxation behavior of cartilage.

Abstract:Objective To investigate the conformational states of ADAMTS13 under different pH conditions. Methods Atomic force microscopy (AFM) was applied to pull ADAMTS13 molecules with two distinct pulling systems: the Biotin-Streptavidin system and the 6×His-Anti-His antibody system. The rupture forces and molecular contour lengths were analyzed. Results Under pH7.4 condition, when ADAMTS13 was pulled by Biotin-Streptavidin system, the mean molecular contour length was (30.93 ± 1.56) nm, exhibiting a bimodal frequency distribution with peak positions at (22.12 ± 0.01) and (49.57 ± 0.05) nm. When ADAMTS13 was pulled using 6×Hist-anti-His antibody system, the mean molecular contour length was (32.77 ± 0.72) nm, also showing a bimodal distribution, with a peak position at (25.73 ± 0.16) and (43.84 ± 0.63) nm, respectively. Under pH6.0 condition, when ADAMTS13 was pulled by Biotin-Streptavidin system, the mean molecular contour length increased to (47.07 ± 1.6) nm, and the frequency distribution shifted to trimodal, with peak positions at (22 ± 1.25), (55.09 ± 2.62) and (76.69 ± 3.06) nm. The conformation of ADAMTS13 was more extended at pH6.0 compared with that at pH7.4. Conclusion ADAMTS13 exists in ‘closed’ and intermediate conformational states at physiological pH7.4. However, at pH6.0, ADAMTS13 can adopt ‘closed’, intermediate, and ‘open’ conformational states. This study contributes to a further understanding of the role of ADAMTS13 in normal physiology and thrombotic thrombocytopenic purpura, providing insights for the development of novel recombination ADAMTS13 drugs.

Abstract:Objective To analyze the motion, deformation, and adhesion behavior of circulating tumor cells (CTCs) in bifurcated microvessels, reveal their mechanical properties under different flow conditions and explore their role in the process of cancer metastasis. Methods A cell-scale modeling approach was adopted, combining the immersed boundary-lattice Boltzmann method (IB-LBM) and the adhesive-dynamics model to simulate the motion and adhesion behavior of circulating tumor cells in microvessels. Results The adhesion behavior of CTCs was significantly influenced by the Reynolds number (Re) and the surface elastic moduli of cells. Under the condition of Re=0.003, the adhesion behavior of CTCs was the most stable; CTCs with a lower surface elastic modulus exhibited greater deformation during adhesion and demonstrated stronger adhesive forces. Conclusions The mechanical properties of CTCs and flow field conditions jointly determine their transport and adhesion behavior in microvessels. The levels of Re and surface elastic modulus play a critical role in the deformation and adhesion of CTCs. The study of the adhesion characteristics of CTCs provides mechanistic insights and new potential directions for cancer prevention and treatment research.

Abstract:Objective To systematically investigate biomechanical characteristics of One-Finger Zen Push Method applied at the Fengchi acupoint under different force conditions, in order to provide precise quantitative data and enhance the treatment efficacy. Methods Ten senior Tuina practitioners were recruited. The German Novel Pliance-X 32 Expert dynamic pressure distribution system was used to record the mechanical parameters during the application of One-Finger Zen Push Method at the Fengchi acupoint under three force intensities: light, medium, and heavy, for 3 minutes. Data from the stable 1-minute segment of the mechanical output was selected for data analysis, and key biomechanical parameters such as the maximum force, average force, peak pressure, mean pressure, force-time integral (FTI), pressure-time integral (PTI), and operational frequency were evaluated. Results Under light, medium, and heavy force conditions, the mean maximum force applied by senior Tuina practitioners at the Fengchi acupoint were 6.31, 9.45, and 18.27 N, respectively, while the mean force were 3.31, 5.64, and 9.05 N, respectively. The mean peak pressures were 26.10, 34.80, and 70.00 kPa, while the mean pressures were 11.95, 21.00, and 26.15 kPa, respectively. The mean FTIs were 55.65, 182.10 , and 225.21 N·s, and the mean PTIs were 167.10, 489.59, and 795.83 kPa·s, respectively. The mean operational frequencies were 156.00, 150.60, and 154.80 times/min, respectively. Conclusions Ten senior Tuina practitioners showed a high degree of consistency between their subjective definitions of light, medium, and heavy force and the objectively measured mechanical parameters. This reflected their precise control over the applied force under different force conditions, verifying the practicality and reproducibility of the One-Finger Zen Push method in clinical applications. This study provides a reliable basis for quantitative research and development of standardized clinical operation guidelines.

Abstract:Objective To construct a transparent and visualized bionic model of human utricle and explore the biomechanical response of the utricle to linear acceleration Methods Using three-dimensioanl (3D) printing technology and PVA-gelatin composite hydrogel fabrication method, a visual physical model of the utricle with a ratio of 10︰1 to the human body was successfully prepared. The biomechanical response of the utricle macula was investigated by varying acceleration and direction stimulation experiments. Results Under 1–5 Hz sinusoidal reciprocating linear excitation, the response amplitude of the bionic macula increased from 4.11 μm to 48.82 μm. The response amplitude of the bionic macula increased linearly with the acceleration. In addition, the macula showed deformation differences in response to acceleration in a specific direction. Conclusion The bionic utricle model prepared in this study can accurately simulate the working mechanism of human utricle, which is expected to provide a new way for the pathological study of vestibular dysfunction and expand a new direction for the application of bionic technology in the field of biomedical engineering.

Abstract:The human gravity line (GL) is a virtual vertical line that passes through the centre of gravity (COG) of the human body and holds significant importance in assessing human biomechanics. Due to the inability to directly determine GL through imaging methods, its application in past research and clinical practice has been somewhat limited. However, with the advancement of technology, the measurement and application of GL have made remarkable progress, becoming an essential supplement to traditional radiographic measurements and demonstrating an increasingly broad application prospect in the field of spinal health. This review summarizes the GL anatomical basis, measurement methods, and its relationship with other commonly used vertical lines. Furthermore, the current status of GL’s clinical application in the field of spinal health is also summmrzied, and its potential role in the diagnosis and treatment of spinal diseases is discussed. It is hoped that the findings will offer new perspectives for the diagnosis and treatment of spinal diseases, and promote further research and application of GL in the field of spinal medicine.

Abstract:Surgical intervention for malignant bone tumors frequently results in bone defects located at the metaphysis of the long bones in the lower extremities. The morphological heterogeneity of the metaphysis poses significant challenges for conventional treatment methods to adequately conform to the defect area. The utilization of three-dimensional (3D)-printed titanium bone repair scaffolds has emerged as an effective reconstructive approach for metaphyseal bone defects, as these scaffolds offer precise shape conformity and provide adequate mechanical support. However, the current commonly used scaffolds do not adequately replicate the biomechanical environment of bone defects, resulting in a suboptimal bone ingrowth within the scaffolds and subsequent prosthesis loosening and failure post-operation. Bone is an organ that is highly responsive to forces, and its fate is regulated by biomechanical signals. Consequently, designing scaffolds with consideration of biomechanical principles to ensure mechanical compatibility between the femoral stems and the bone defect sites is a critical factor influencing the success of bone defects reconstruction. This review mainly introduces the biomechanical factors influencing bone defect repair and the advancements in designing 3D-printed titanium bone repair scaffolds biomechanically matched with bones, offering theoretical guidance for scaffold design and preparation.

Abstract:Osteoporosis caused by type 2 diabetes mellitus (T2DM) increases the risk of fracture and post-fracture mortality. However, the pathogenesis of the disease remains unclear, resulting in a lack of effective strategies for its prevention and treatment. In this review, firstly, the effects of advanced glycation end products (AGEs) produced by non-enzymatic glycation on bone matrix composition, bone structure, and mechanical properties of T2DM are summarized. Then, the biological mechanism of AGEs and receptor for AGEs (RAGE) affecting bone degeneration in T2DM is clarified. Finally, antidiabetic and other drugs that are beneficial to bone anabolism are discussed. These drugs positively affect bone quality through inhibiting AGE/RAGE signaling pathway. Accordingly, it is expected to provide potential intervention targets and ideas for the prevention and treatment of T2DM-related osteoporosis.

Abstract:The hemodynamics within the aortic lumen are highly complex, and the mechanical stimuli generated by blood flow play a crucial role in the occurrence and progression of aortic dilation disease. Endothelial cells, as key components of the vascular endothelium, respond precisely to microenvironmental changes caused by blood flow through mechanoreceptors, including ion channels, receptor tyrosine kinases, and membrane structures. These mechanoreceptors convert mechanical stress into biochemical signals, thereby affecting the physiological functions and pathological changes of blood vessels. In recent years, significant advances have been made in understanding the mechanisms by which endothelial mechanoreceptors are involved in aortic dilation disease. This review summarizes the research progress of mechanoreceptor-mediated endothelial cell function in regulating aortic dilation disease and provides a perspective on future research directions, with the aim of offering new insights and potential targets for the development of clinical treatment strategies.