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Abstract:Rehabilitation engineering and biomechanics are naturally closely related, and biomechanics is the core problem in many rehabilitation projects. In 2021, the latest progress in the field of biomechanics of rehabilitation engineering is mainly reflected in three aspects: biomechanics of anthropomorphic design of rehabilitation equipment and assistive devices, biomechanics of human environment interface, and biomechanics of human-computer dynamic interaction. Based on the latest progress in 2021, this review summarized the research methods, main applications and existing problems of rehabilitation engineering biomechanics, and discussed the future development direction.

Abstract:Objective To explore the lower limb motor coordination and stability of older adults over 65 years oldduring Tai Chi brush knee and twist step. Methods A total of 30 Tai Chi practitioners randomly completed walkingand brush knee and twist step. The lower limb kinematics datawere collected by Vicon three-dimensional (3D)motion capture system. Results During brush knee and twist step, the joint angle in sagittal plane and continuous relative phase ( CRP) values of hip-knee and knee-ankle joints during brush knee and twist step changed frequently. The mean absolute relative phase (MARP) for hip-knee and knee-ankle joint and the mean deviation phase ( DP) for hip-knee joint were significantly lower than those during walking. Conclusions Compared with walking, the hip-knee and knee-ankle joints present a more coordinated and stable segment motion pattern during Tai Chi brush knee and twist step. Tai Chi exercise may provide a specific coordination training method for older adults, enhance posture stability and prevent falls

Abstract:Objective To explore biomechanical characteristics of hemiplegic patients using UOHL (up obstacles with healthy leg, down obstacles with affected leg) and UOAL ( up obstacles with affected leg, down obstacles with healthy leg) to pass through obstacles, and to provide theoretical basis for reducing the incidence of falls in patients. Methods The Qualisys motion capture system and three-dimensional ( 3D) force plate were used to collect the kinematics and dynamics data of 15 hemiplegic patients passing through obstacles with normal walking mode (NWM), UOHL and UOAL, and the data were processed and analyzed. Results Compared with NWM,805 both UOHL and UOAL increased bilateral lower extremity range of motion ( ROM) to some extent. Compared with NWM and UOHL, vertical ground reaction force (GRF) of affected leg side under UOAL fluctuated more, and gait stability was worse, indicating a greater risk of falling. Conclusions When patients pass through the obstacle, the requirements for joint ROM on the side of the obstacle are relatively high, the adaptability of the affected leg side is poor. The GRF in vertical direction changes greatly during single-leg support period after touching the ground. When the body weight is completely transferred to this side, it is easy for the patient to fall. Compared with UOAL, patients can easily maintain gait stability when using UOHL to pass through obstacles, and the risk of falling will be reduced.

Abstract:Objective To investigate the effect of foot metatarsophalangeal (MTP) joint constraint on human gait stability. Methods Gait experiment under two states was conducted on a horizontal wet-slip test bench, namely,with and without constraint of the MTP joints. The differences in time-space gait parameters, kinematic parameters, kinetic parameters, and utilization coefficient of friction (UCOF) were analyzed. Results Under the state of MTP joint constraint, the average human walking speed was reduced by 50 mm / s, the stride length was reduced by 0. 22 m, and the double support phase time was shortened by 70 ms. MTP joint constraint resulted in a significant increase in the range of motion (ROM) of the hip and knee in sagittal plane and a decrease in the ROM of the ankle. Meanwhile, the UCOF amplitude with MTP joint constraint was 1. 15 times higher than that without MTP joint constraint, indicating an increased probability of human slip and fall as well as an increased walking instability. Conclusions MTP joint constraint in the foot can reduce walking stability. The results of thisstudy provide data and theoretical support for the development of toe flexion rehabilitation device.

Abstract:Objective To study the method of hand gesture recognition using surface electromyography ( sEMG) signals from the forearm and hand, as well as joint angles of the thumb and index finger under different hand gestures, so as to explore the feasibility of controlling the exoskeleton hand with sEMG signals. Methods The sEMG signals of six muscles in the right upper limb of 20 healthy right-handed subjects were collected. The time domain feature values of sEMG signals were extracted. Classifiers such as artificial neural network (ANN), Knearest neighbor (KNN), decision tree ( DT), random forest ( RF) and support vector machine (SVM) were used for pattern recognition of six daily hand gestures. Meanwhile, trajectory of the thumb and index finger movements was captured by the Vicon camera tracking system. The thumb and index finger angles were calculated. Results Pattern recognition of six hand gestures could be achieved using sEMG signals of the forearm and hand, and the ANN classifier had the best classification prediction, with test set prediction accuracy of 97. 9% and Kappa coefficient of 0. 975. The thumb and index finger angles under six hand gestures were also calculated, and correlation analysis of joint angles under different hand gestures was conducted. Conclusions By using forearm and hand sEMG signals for hand gesture recognition, it is possible to achieve classification prediction with almost identical results. The results in this study demonstrate the feasibility of applying sEMG signal based-hand gesture recognition to exoskeleton hand control.

Abstract:Objective To better evaluate the ergonomics of an ankle-foot orthosis (AFO), this study proposed a method for evaluating the impact of AFO stiffness on gait biomechanics based on human-machine coupling model. Methods Firstly, mechanical properties for two kinds of AFO were evaluated, and AFO stiffnesses were quantified. Next, kinetics and kinematics parameters from lower limb joints of 30 subjects were collected during normal walking and walking with two kinds of AFO stiffness. Finally, the impact of AFO stiffness on joint angle,joint torque, and muscle force of lower limbs during walking were quantitatively analyzed by simulation. Results Under the circumstance of two different AFO stiffness, the peak ankle dorsiflexion angle, peak knee flexion angle, and hip extension angle significantly increased (P<0. 05). The peak muscle force of soleus and gastrocnemius also showed an increasing trend. The peak ankle plantarflexion angle, hip flexion angle and peak moment of hip flexion obviously decreased (P<0. 05). Conclusions The AFO human-machine coupling simulation method can effectively realize the quantitative evaluation of the AFO stiffness effect on gait biomechanics. It can also be applied to assess and optimize the ergonomics of other assistive devices. These results provide theoretical guidance for the selection, adaptation, and optimization design of AFO.

Abstract:Objective To observe the effects of frailty state and walking speed on kinematic characteristics of lower limb joints in older adults. Methods A total of 59 old people aged 60 and above participated in this study.The subjects were divided into non-frailty, pre-frailty, and frailty groups by the Kihon Checklist. The Xsens MVN motion capture inertial sensor was used to collect kinematic data from three groups of older adults during walking at slow, customary and fast speeds, and two-way repeated-measures analysis of variance was performed to determine the difference of kinematic characteristics between three groups of older adults walking under different frailty states and at different speeds. Results The age of frailty group was significantly older than that of nonfrailty group (P<0. 01). The maximum knee flexion angle and range of motion (ROM) of knee and ankle joints in frailty group were significantly smaller than those in non-frailty group and pre-frailty group (P< 0. 05), and the maximum plantar-flexion angle of the ankle joint in frailty group was significantly smaller than that in non-frailty group (P<0. 05). With walking speed increasing, the single support time of frailty group increased significantly (P<0. 05), the maximum hip flexion and extension angle, the maximum knee flexion angle, the maximum ankle plantar-flexion angle, the hip and ankle ROMs in three groups were significantly increased (P<0. 05), the double support time, the maximum ankle dorsiflexion angle, the knee ROM were significantly decreased (P<0. 05), and only the maximum hip extension angle, the hip ROM and the maximum knee flexion angle showed significant differences between slow speed and customary speed(P< 0. 05). Correlation analysis showed that the hip and knee ROMs were significantly positively correlated in pre-frailty group and frailty group at different walking speeds (P<0. 01),the knee and ankle ROMs were significantly positively correlated in frailty group at customary and fast walking speeds (P<0. 05). Conclusions With the change of frailty state, the sagittal plane angle of lower limb joints in older adults decreased continuously, mainly concentrating on knee and ankle joints. The synchronization between the two joints were enhanced, and the degree of freedom was decreased during walking. With the increase of walking speed, older adults under different frailty states adopted the same walking strategy. These results are helpful for screening and rehabilitation guidance of the frailty population.

Abstract:Objective To explore the differences in physical activity, sedentary behaviour and balance ability between older adults and young people, and the correlation of physical activity at different levels and sedentary behaviour with balance ability. Methods A total of 74 older adults and 60 young people were selected. The physical activity and sedentary behaviour of the subjects were monitored by three-axis accelerometers, and their static balance ability was measured by three-dimensional (3D) force platform. Results For elderly women, moderate-to-vigorous physical activity (MVPA) were positively correlated with static balance ability (P<0.05), and sedentary time was negatively correlated with static balance ability (P<0.05). For elderly men, sedentary breaks were positively correlated with static balance ability (P<0.05). Conclusions Compared with young people, older adults have higher light physical activity levels and less sedentary time. For older adults, especially elderly women, those with higher MVPA levels or less sedentary time have better static balance ability. Physical activity has a positive effect on balance control.

Abstract:Objective To explore the correlation between sagittal balance and plantar pressure in adolescent idiopathic scoliosis (AIS). Methods Forty patients meeting the criteria of AIS were selected. Plantar pressure test was conducted for each patient after they finished the Xray shooting. The sagittal parameters included lumbar lordosis (LL), thoracic kyphosis (TK), sacral slope (SS), pelvic incidence (PI), pelvic tilt (PT), spine sacral angle (SSA) and C7sagittal vertical axis (C7SVA). The plantar pressure parameters included contact area and pressure percentage of the forefoot and rearfoot. The correlation between sagittal parameters and plantar pressure parameters was analyzed. Results Among the sagittal parameters, LL was correlated with SS, PI, PT, SSA; PI was correlated with SS, PT, SSA; SS was strongly correlated with SSA; C7SVA and SSA had a correlation. On the main curve side, LL was negatively correlated with contact area of the rearfoot and whole foot, and positively correlated with the pressure percentage of the rearfoot and whole foot; there was a negative correlation between TK and pressure percentage of the forefoot. PT was positively correlated with contact area of the forefoot, rearfoot and whole foot. Other sagittal parameters such as SS, PI, SSA and C7SVA had no correlation with plantar pressures. On the opposite side of the main curve, there was no correlation between sagittal parameters and plantar pressures. Conclusions In the AIS, the sagittal balance is closely related to the plantar pressure distribution. In particular, the sagittal parameters LL, TK, and PT are most correlated to the plantar pressure parameters.

Abstract:Objective To compare the differences in dynamic stability and cost of dual-task stability during walking with different dual tasks. Methods Kinematics data of 40 subjects walking with different dual tasks were collected by three-dimensional (3D) motion capture system, and the related dynamic stability indexes were indirectly calculated. One-way repeated measures ANOVA was used to compare gait parameters and dynamic stability between single-task walking and different dual-task walking. Two-way repeated measures ANOVA was used to analyze the effects of dual-task types (cognitive tasks and motor tasks) and task loads (simple tasks and difficult tasks) on cost of human dual-task stability and the interaction between them. Results Compared with the single task, the pace under intervention of different dual tasks decreased (P<0.05), the pacing frequency and dynamic stability increased (P<0.05), the step length under intervention of double motor loads was smaller than that during single-task walking (P<0.05), and the step length under intervention of a single cognitive task and double cognitive tasks was larger than that during single-task walking (P<0.05). The stability cost of a simple cognitive task was higher than that of a simple motor task (P<0.05), the stability cost of a difficult cognitive task was lower than that of a difficult motor task (P<0.05), and the stability cost of a simple motor task was lower than that of a difficult motor task (P<0.05). Conclusions Compared with single-task walking, the intervention of different dual tasks will increase dynamic stability of human body. For the stability cost of dual tasks, there are interaction effects among different task types and different task loads. When the task load is high, the dual-task cost of the cognitive task is low. Namely, the negative interference amplitude of the cognitive task increases, which will damage dynamic posture control ability of the body. When the second task is the motor task, the negative interference amplitude on dynamic stability of human body increases under a low load, which reduces dynamic posture control ability.

Abstract:Objective To study the age and gender characteristics for static and dynamic posture control ability (PCA) of 4-6 years old children, analyze the contribution rate of each sensor to PCA. Methods A total of 100 children were tested for static and dynamic PCA. The differences in PCA of two single legs were analyzed by the independent sample t-test. The effects of age × gender and four standing conditions (with eyes open/closed on solid ground, with eyes open/closed on mat) on PCA were analyzed by ANOVA. Results There was a very significant difference in static PCA of two single legs for 4-6 years old children standing with eyes open on hard ground (P<0.01), and the static PCA was 6-year old age group>5-year old age group>4-year old age group. The main effect of standing time under four standing conditions was very significant (P<0.01), the sum of the contribution rates of each receptor was greater than 100%, and the contribution rates were vestibular sensation>vision>proprioception. The dynamic PCA of 6-year old age group was significantly better than that of 4-year old age group and 5-year old age group. Conclusions The static PCA of 46 years old children showed the differences in dominant leg and non-dominant leg. The dynamic and static PCA increased with age, and the development speed of the vestibular sensory system in 6-year old girls was faster than that in 6-year old boys. The body maintains posture control through complex integration of vision, proprioception, vestibular perception and so on, and vestibular sense plays a major role, followed by vision and proprioception.

Abstract:Objective To study pressure pain threshold (PPT) of the spine and lower limbs for patients with acute unilateral neck pain and neck mobility deficits, and its relationship with cervical pain and cervical range of motion (ROM), so as to establish accurate quantitative assessment index by comparison with healthy controls. Methods A total of 48 patients with unilateral neck pain and neck mobility deficits (experimental group), as well as 48 healthy adults (control group) were included. The PPTs of the splenius capitis, upper fibers of trapezius, rhomboideus major, quadratus lumborum, midpoint of hamstring, popliteal fossa, mid and lower point of gastrocnemius, and plantar fascia at base of the second metatarsal were tested by using a handheld thresholds algometer. The pain score and cervical ROM were recorded. ResultsThere were significant differences in neck extension as well as rotation and lateral flexion of the affected side between experimental group and control group. The PPTs of splenius capitis, trapezius, mid and lower part of gastrocnemius in the affected side in experimental group were significantly different from those in the healthy side and in control group (P＜0.05). There was a negative correlation between neck pain and ROMs of neck extension, lateral flexion of the affected side and rotation of the affected side (P＜0.05). A correlation between neck pain and the PPTs of splenius capitis, upper trapezius, midpoint of gastrocnemius muscle and lower part of gastrocnemius muscles was also found (P＜0.05). Conclusions The PPTs of trapezius muscle, splenius capitis and gastrocnemius decrease in patients with acute neck pain and unilateral mobility deficits, and they are significantly correlated with neck pain and mobility deficits. This study provides references for quantitative assessment of patients with neck pain in clinic.

Abstract:Objective To understand relevant characteristics of foot soles in older adults during walking through three types of insoles, so as to provide references for current design of the insoles for older adults, as well as theoretical basis for the manufacturers’ production. Methods A total of 25 physically and mentally healthy older adults were selected. They put on Pedar-x plantar stress test equipment, and performed walking test on a treadmill at the speed of 4 km/h, so as to obtain the plantar force, pressure and pulse. The subjective feedback from the subjects were obtained through questionnaire survey. Results There was a very significant difference between insole A and insole C in the average score of soft and hard liking and rebound strength of rear feet (P<0.01). The maximum force and average pressure of insole C in each plantar region were significantly lower than those of insole A and insole B (P<0.01). The impulse of insole C from M1 region (heel) to M7 region (2nd-5th phalanx) was lower than that of insole A and insole B, and there was a significant difference in M1 region (heel) (P<0.05). The impulse of insole A and insole C in M2 region (lateral arch) had a significant difference (P<0.05), and the impulse of insole B and insole C in M5 region (2nd-4th metatarsal) also had a significant difference (P<0.01). Conclusions Changing the insole design can effectively interfere with plantar pressure of older adults during walking. Polyurethane foam material is suitable for the insole of older adults. Adding gel shock absorber in front foot and heel of the insole can effectively reduce high pressure of older adults during walking. However, the physical thickness of the front, middle and rear part of the insole is different, which is easy to cause foot fatigue of older adults during walking.

Abstract:Objective To investigate the inner relationship of mechanical properties and migration during epithelial-mesenchymal transition (EMT) of melanoma A375 cells. Methods EMT was induced by TGF-β1 in epithelial-like melanoma A375 cells, and further morphological observation and analysis of A375 cells were performed. The effect of TGF-β1 on EMT-related protein expression was detected by immunofluorescence. Cell scratch and transwell assay were used to detect cell migration and invasion. The cell stiffness was measured by atomic force microscopy (AFM). The cytoskeletal proteins of G-actin and F-actin were determined by flow cytometry. Results Melanoma A375 cells were successfully induced by TGF-β1 stimulation to establish the EMT phenotype. TGF-β1 increased the expression of mesenchymal marker of vimentin and decreased the expression of epithelial marker of E-cadherin in a timedependent manner, which further enhanced cell migration and invasion. TGF-β1-induced EMT also altered the biomechanical properties of melanoma A375 cells, which showed a significant increase in cytoskeletal G-actin/F-actin ration and an obvious decrease in cell stiffness. Conclusions The cytoskeleton of melanoma A375 cells undergoes depolymerization and cell stiffness decreases in response to TGF-β1-induced EMT, which enhances the ability of cell migration and invasion. These research findings provide new strategy in mechanobiology for clinical treatment of cancer metastasis.

Abstract:Objective To investigate the role of osteocytic connexin43 (Cx43)-formed channels after being submitted to mechanical overloading on knee joint. Methods The strain was applied to left knee joint of 15-week Cx43 transgenic mice (R76W: gap junctions were blocked and hemichannels were promoted; Δ130-136: both hemichannels and gap junctions were blocked) and their wild-type littermates, and right knee joint was as control. A week later, the mice gait was analyzed to evaluate the structure of subchondral bone and articular cartilage.After inhibition of Cx43 channels, MLO-Y4 cells were submitted to 15% cyclic tensile strain, and the expression of related factors were detected. The supernatant was collected to culture ATDC5 cells, and the gene expression and the osteogenic differentiation ability were detected in ATDC5 cells. Results Gait analysis showed that inhibition of Cx43 channels did not significantly affect the mice gait. However, the femoral OARSI score increased significantly and the ratio of trabecular bone area decreased in transgenic mice. Conditional medium from MLO-Y4 cells with inhibition of Cx43 channels reduced the expression of ADAMTS5 and COL2 in ATDC5 cells, and enhanced the osteogenic differentiation ability. Conclusions The osteocytic Cx43 channels can respond to mechanical overloading, affect the expression of key genes and is involved in osteogenic differentiation process in chondrocytes, thus affects cartilage structure in response to mechanical overloading. The study will provide new ideas for the prevention and treatment of osteoarthritis.

Abstract:Objective To investigate the regulatory mechanism of wild-type (WT) and gain-of-function (GOF) ADAMTS13 interaction with VWF A2. Methods The adhesion frequency, rupture force, and bond lifetime between WT or GOF ADAMTS13 and VWF A2 under different external forces were measured by atomic force microscope (AFM). The kinetic parameters were derived by fitting with the Bell-Evans model. Results The widths of the potential barrier along the direction of force were 0.41 nm and 0.29 nm, and the dissociation rates under 0 N force were 1.50 s-1 and 3.28 s-1for the WT ADAMTS13-VWF A2 complex and the GOF ADAMTS13VWF A2 complex, respectively. Furthermore, the lifetime of bond and dissociation rate of the complexes under different applied forces were measured by AFM clamp mode. The result revealed that the interaction between WT or GOF ADAMTS13 and VWF A2 exhibited the characteristics of biphasic forcedependent ‘catch-slip’transition bond. Conclusions The mechanical strength and stability of the WT ADAMTS13VWF A2 complex are higher than those of the GOF ADAMTS13-VWF A2 complex. Both the binding of these two complexes exhibits the mechanical response characteristics of the ‘catch-slip’ transition bond. The research findings contribute to further understanding the interaction between ADAMTS13 and VWF, so as to provide new ideas for the development of antithrombotic drugs.

Abstract:Objective To quantitatively investigate the cupula time constant in vestibular semicircular canals of human inner ear by numerical simulation and experiment, and to clarify the time process of coding angular motion by semicircular canals. Methods The numerical model of bilateral semicircular canals in human inner ear was constructed, and then biomechanical responses of the cupula were simulated by fluid-structure interaction to calculate the mechanical relaxation time constant of the cupula. Meanwhile, cupula time constant of the volunteers was calculated based on their nystagmus slow-phase velocity obtained in vestibulo-ocular reflex experiment. Results The mechanical relaxation time constant of the cupula calculated by numerical model of semicircular canals in human inner ear was 3.75 s. The average cupula time constant was approximately 4.86 s measured by experiment. The result in numerical model was approximately consistent with that in experiment. Conclusions The cupula time constant in vestibular semicircular canals of human inner ear was approximately 4.86 s, which reflected a combined effect of mechanical relaxation of the cupula and afferent adaptation of semicircular canals, as well as revealed the time process of coding angular motion by semicircular canals.

Abstract:Objective To explore the universal behavior or law of viscoelastic properties of biological soft tissues. Methods According to mechanical structure of biological soft tissues, four-element viscoelastic structure models were built, based on the varied configurations of two linear springs and two dashpots. The differential equations for motion of the viscoelastic models were derived through their geometry, and then were applied to analyze the stress relaxation, creep behavior, stress relaxation time and creep time of the four-element models. Results All the possible four-element viscoelastic models had universal constitutive relation, stress relaxation and creep function. The comparison between the model prediction and the experimental data from various tissues including the aortic valves, ligaments and cerebral artery illustrated that the mechanical behaviors of biological soft tissues could be adequately characterized by the four-element viscoelastic models. Two characteristic time τ1 and τ2 had a significant effect on stress relaxation of biological soft tissues, and the ‘fast’ relaxation time τ1 had a significant effect on the time required for the stress to reach the equilibrium state, while the ‘slow’ relaxation time τ2 didn’t obviously influence the relaxation rate, but had obvious influences on the state of stress relaxation. Conclusions The time-dependent behaviour of biological soft tissues can be characterized by two characteristic time scales, known as ‘fast’ and ‘slow’ time. The stress-strain relationship, stress relaxation and creep function of biological soft tissues with two characteristic times have the same mathematical form, which is independent of the configuration and arrangement of the selected spring and dashpots. However, in order to ensure the rationality of mechanical parameters of the model, suitable models should be selected for different biological soft tissues.

Abstract:Objective To investigate the effects of controllable tensile stress on intervertebral disc degeneration (IDD) in goats. Methods Twenty-four male 6-8 month-old goats were selected to construct the IDD models by axial induction of 40 N compression stress with elastic stress device. After the IDD models were completed, they were randomly divided into 6 groups (Group A-C were control groups, and Group D-F were the experimental groups). The compressive stress on IDD model was converted into tensile stress. The tensile stress of Group A-C was 0 N, the tensile stress of Group D-F was 40 N. The duration of tensile stretch was 4, 6 and 8 weeks, respectively. The degeneration and rehydration of intervertebral discs were detected by imaging (X-ray, magnetic resonance imaging) and histopathology (HE staining, immunohistochemistry). Results With prolongation of tensile stretch, disc height index (DHI) of experimental groups increased. Pfirrmann grading indicated that IDD degree of experimental groups was the lowest at 6th week. More nucleus pulposus cells were observed in experimental groups. Immunohistochemistry showed that type I collagen decreased first and then increased, while type II collagen increased first and then decreased in nucleus pulposus. Conclusions IDD can be repaired and rehydrated in a certain amount of time under a certain tensile stress. The results provide new insight and theoretical foundation for clinical practice in treating IDD low back pain.

Abstract:Objective To investigate the adaptive response of patella patellar tendon junction (PPTJ) and tibial patellar tendon junction (TPTJ) in rabbits under short-term jumping loads. Methods Nineteen 18-week old female New Zealand white rabbits were randomly divided into control group (n=4) and 1-day jump (J1), 3-day jump (J3), 5-day jump (J5) group (n=5 in each group). Electrical stimulation quantitative jumping device was used to make rabbits complete 150 jumps per day (10 groups × 15 jumps, 3 minutes’ per group, 6 minutes rest after completion of 4th and 8th groups, 3 minutes rest after completion of the other groups, the average jumping speed was 0.083 times/s, the total training time per day was about 70 minutes). The rabbits were executed at 24th hour after the training. The corresponding knee tissues from left and right hind limbs were taken for HE staining and immunohistochemistry. The histomorphological results were qualitatively described. The cell density, cartilage thickness, and the expression of IL-1β, IL-6, and TGF-β1 were quantitatively monitored. Results The micro-injury of PPTJ and TPTJ occurred at different degrees in jump groups (J1, J3, J5 groups). The IL-1β and IL-6 expressions of PPTJ in J5 group were significantly higher than those in control group and J1 group; the IL-6 expressions of PPTJ in J3 group were significantly higher than those in control group; the thickness of TPTJ cartilage band in J5 group was significantly greater than that in control, J1 and J3 groups; in control group, the IL-1β and IL-6 expressions of PPTJ were significantly lower than those of TPTJ; in J1 group, the IL-1β, TGF-β1, IL-6 expressions of PPTJ were significantly lower than those of TPTJ；in J3 group, the IL-6 expressions of PPTJ were significantly lower than those of TPTJ. ConclusionsThe pathological changes of PPTJ induced by short-term jumping loads were earlier than those of TPTJ. The rabbit PPTJ inflammatory factors IL-1β and IL-6 were up-regulated during injury process under short-term jumping loads, but there was no significant change of inflammatory factors in rabbit TPTJ. The results provide laboratory evidence for the pathogenesis of patellar tendinopathy.

Abstract:Objective To study mechanical properties of two thoracic aortic bare stents (stent Ze and stent Fa), so as to provide the theoretical basis for the design and clinical selection of bare stents. Methods The finite element models and experimental models of two bare stents were constructed. Finite element analysis (FEA) on bending, radial force, simulated use of the two models were conducted. The accuracy of FEA was verified by experiment result and the vessel stress and strain after stent implantation were predicted. Results The FEA indicated that section flattening rates of stent Ze and stent Fa were 3.83% and 18.83% at 90° bending (8.57% and 14.27% in test results) and 12.02% and 23.72% at 180° bending (14.37% and 23.35% in experiment results). The maximal radial forces of stent Ze and stent Fa were 33 and 429 N/m in systolic phase (31 and 433 N/m in experiment results), and 27 and 146 N/m in diastolic phase (29 and 179 N/m in experiment results). The maximal stresses, strains, and diameter expansion rates of vessels implantation of stent Ze and stent Fa were 4 and 18 kPa, 4.17% and 13.92%, and 1.03% and 8.98%, respectively. There was no significant difference between the FEA and experiment results (P>0.05). Conclusions After implantation of stent Ze and stent Fa, the maximum stress and strain of vessels were within the allowable range. Stent Ze is suitable for curved vessel implantation with a better bending performance. Meanwhile, stent Ze has a lower radial force, and it can provide intimal support as the Petticoat stent with a lower radial force. Stent Fa has a higher radial force, and it can enhance its stability in vessels and reduce the risk of spinal ischemia, thus being suitable for restrictive bare stents.

Abstract:Objective To reconstruct three-dimensional vascular model bases on CT images, and to study the influence patters of external uniform magnetic field on hemodynamic behavior. Methods The mathematical model of blood flow with external uniform magnetic field was established by using the theory of computational fluid dynamics and the method of magnetohydrodynamics. The simulation was carried out by using the multi-physical field coupling simulation software COMSOL Multiphysics to explore the effects of magnetic field intensity on blood flow velocity, pressure and shear stress. Results The magnetic field significantly suppressed the velocity at the center of blood vessel with magnetic field intensity increasing. The wall pressure decreased with magnetic field intensity increasing, and the influence of magnetic field on wall pressure before blood flow bifurcation was obvious, but the influence on wall pressure after blood flow bifurcation was weak. After blood flow entered the branch vessel,the wall shear stress increased significantly, and the effect of magnetic field on shear stress also increased significantly. Conclusions Human blood has magnetohydrodynamic characteristics, and the magnetic field in a certain intensity range has a significant impact on blood flow. The results provide a theoretical basis for the design of artificial equipment with high intensity magnetic field, evaluation for the effects of artificial magnetic field on human hemodynamics, and diagnosis of the diseases caused by artificial magnetic field.

Abstract:Objective To compare the stress distributions on various tissues in temporomandibular joint (TMJ) before maxillary expansion and with maxillary expander on the maxillary by using the three-dimensional (3D) finite element method. Methods Based on CBCT image data from a patient with maxillary transverse deficiency, the finite element models of TMJ before maxillary expansion and with maxillary expander were reconstructed. The same muscle force and boundary constraint were applied on the two models, and then the von Mises stress, the maximum and the minimum principal stresse on mandibular condylar, joint disc and glenoid fossa were evaluated. Results The von Mises stress of TMJ model before maxillary expansion was mainly distributed in the anterior of mandibular ramus, the anterior of condyle, the middle of articular disc and the top of articular fossa. The pattern of stress distribution on TMJ with maxillary expander was basically consistent with that before maxillary expansion. The TMJ stress was significantly increased, but the stress concentration areas were more evenly distributed. The stress distribution of mandibular condyle and disc moved more laterally and forward. The posterior of mandibular condyle showed a wider distribution of the maximum principal stress. Conclusions The orthopedic force generated by maxillary expander can increase the TMJ stress, stimulate tissue reconstruction of mandibular condyle, and coordinate the condyle and disc. In clinical practice, the patients with maxillary transverse deficiency should be treated with appropriate means of maxillary expansion.

Abstract:Objective Based on the existing pneumoperitoneum device, a new suspension system for minimally invasive surgery was designed under the condition of low pressure, ao as to expose more surgical vision and facilitate the smooth operation.Methods Structure design of the suspension system was completed with Solidworks software. Based on the finite element simulation analysis technology, the effects of four different clamp materials, i.e. medical stainless steel, Ti6Al4V, Ti6Al7Nb and pure titanium, and three different mid-plane structure materials, i.e. nylon (PA6), polyester and polypropylene (PP), on performance of the suspension system were studied. Results In the process of clamping tissue by clamps with four different materials, the tissue deformation was lower. The gripped tissue did not slip out of the clamp. The stress of the clamp and its holding tissues were the lowest when the medical stainless steel material was selected. For the material of the mid-plane structure, when polyester was selected, the mid-plane structure would be destroyed under external loading in working process of the suspension system. When PP material was selected, the mid-plane structure would have the largest deformation, which was not conducive to the clinical operation.Conclusions The best material for clamp is medical stainless steel. It is not suitable to choose polyester as the material of the mid-plane structure, and choosing PA6 as the material of the mid-plane structure is the best.

Abstract:Objective In term of the issue that external fixator for distal radius fractures was lack of phased functional exercise of the wrist, a method for optimizing the design of external fixator structures based on transient analysis was proposed, so as to provide theoretical references for the design of external fixator structure. Methods Three working modes, namely, fixation, traction and flexibility were determined. Transient dynamic analysis was carried out targeting at the traction and flexibility mode of external fixator, so as to judge its stress and displacement changes under traction and flexibility loads. The key dimensions of external fixator were selected by sensitivity analysis, so as to screen out the important dimensions, and mass and maximum displacement were selected as target variables. Orthogonal test method and fuzzy optimization method were used to establish the mathematical model to change the multi-objective problem into a single objective problem, and then genetic algorithm was used to optimize the solution. Results The design of external fixator met design requirements in both traction and flexibility modes, with a stronger rigidity. The dimensional optimization has result ed in a 5% reduction in mass and an 8% reduction in maximum deformation compared to the original model. Conclusions This study achieves the goal of lightweight design and lays the foundation for improved design and research of external fixator for distal radius fractures.

Abstract:Objective To determine mechanical parameter differences in different partitions of parietal bone fragments and their relationship with the thickness. MethodsThe left parietal bones were divided into three partitions, i.e., upper parietal bone (UPB), lateral parietal bone (LPB) and posterior parietal bone (PPB), and the fragments from each partition were intercepted. The ultimate load of the fragments, deformation under ultimate load, bending strength and elastic modulus under ultimate load were detected by quasi-static three-point bending test, and the differences in material mechanical parameters of parietal bones in different partitions were analyzed, as well as the correlation between bone thickness and the parameters above. Results The thickness was as follows: UPB>PPB>LPB (F=21.298, P<0.05). There were significant differences in ultimate load, bending strength and elastic modulus among the UPB (F=7.082), LPB (F=5.206) and PPB (F=7.748, P<0.05). The ultimate load was as follows: UPB>PPB>LPB. The bending strength and elastic modulus were as follows: LPB>PPB>UPB. There were significant differences in deformation between the UPB and the LPB (P<0.05). The ultimate load was positively correlated with the thickness (r=0.683, P<0.05), while the bending strength (r=-0.467) and elastic modulus (r=-0.646) were negatively correlated with the thickness (P<0.05). Conclusions The mechanical parameters and the thickness of materials in different partitions of parietal bone fragments are different. The ultimate load has a positive correlation with the thickness, while the bending strength and elastic modulus have a negative correlation with the thickness.

Abstract:Diastasis recti abdominis (DRA) is one of postpartum complications, and abdominis muscles training is often used for the rehabilitation of DRA, but universally acceptable training modes and support of corresponding theories are not available now. In this paper, the mechanism of DRA and rehabilitation effects were reviewed from biomechanical view of the abdominal wall. Meanwhile, the main reasons for the controversy were also analyzed. The measurement method and measurement sites of inter-rectus distance (IRD) and rectus abdominis muscle thickness are inconsistent; the mechanism of DRA was not studied by biomechanical method. Therefore, in the future, the prediction for training effect of DRA should be standardized, the mechanical characteristics of abdominal muscles and their aponeurosis in the status of DRA should be studied, so as to provide references for abdominal muscle training

Abstract:With the rapid development of computer science and technology, the concept of digital medicine emerges, and digital technique is increasingly used in the field of orthopedics. Finite element analysis (FEA) is a powerful and highly effective method to simulate real experiments, and it is often employed to study the medical issues of biomechanics, biomaterials, surgery simulation, etc. In particular, the application of FEA in the field of foot and ankle is growing as well. At present, the finite element model-based biomechanical analysis of foot and ankle has been widely used in mechanism analysis of the diabetic foot, plantar fascia diseases, foot and ankle fracture and osteoarthritis, as well as in prosthetic design, surgical simulation, shoe and insole design, etc. which significantly enhances the knowledge of surgeons in the aspect of foot biomechanics, and provides new thoughts to investigate and diagnose the ankle-related diseases. However, FEA studies of hallux valgus are relatively limited. In this paper, the biomechanical analysis and modeling of hallux valgus and secondary flatfoot and metatarsal pain were summarized, including the current situation of FEA method in clinical applications, the advantages and disadvantages, as well as its future prospects.

Abstract:Three-dimensional ( 3D) printing technology has become the focus of researches in various fields,including 3D scanning anatomical structure or surface, 3D digital reconstruction, computer-aided modeling, STL format conversion, product printing and other steps. Because of its low production cost, high production efficiency, individualized design and other advantages, 3D printing is widely used in various fields of medicine. In recent years, 3D printing technology has been gradually applied in the production of orthopedic orthotics, which plays an important role in the treatment and rehabilitation of joint, trauma and spinal-related diseases. In thisreview, the manufacturing method, classification and application of 3D printed-orthosis were summarized.