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Abstract:Cells are in complicated mechanical and physical microenvironment in vivo. The former mainly includes flow shear, tension, compression or torsion, and the latter covers stiffness and topography of extracellular matrix, spatial location, volume constraint or osmotic pressure, featured with various types, patterns, and parameters of mechanical or physical loading. Cell biomechanics mainly focuses on the alteration of mechanical properties of cells and the mechanical remodeling of subcellular components, the cell development, growth, proliferation, differentiation, and apoptosis under distinct mechanical stimuli, and the cellular sensation, transmission, transduction, and responses to external forces. This review summarized the major progresses in cell biomechanics in 2021, including studies on cardiomyocytes, endothelial cells, osteoblasts, immune cells, cancer cells and stem cells, as well as the related new techniques.

Abstract:Objective To study the wear condition of rotating hinge knee prosthesis (RHKP) during horizontal walking gait, and provide technical references for wear prediction and clinical application of this kind of prosthesis. Methods A finite element wear model of RHKP was established based on the standard ISO 14243, and the simulation results including the wear distribution and mass wear rate of tibiofemoral joint surface were compared with the results from in vitro experiments on the same type of prosthesis. Results The mass wear rate of the polyethylene insert was 26.01 mg/MC (million cycle)from finite element analysis (FEA) and (30.06±1.21） mg/MC from in vitro experiments, and the mass wear rate of the upper surface of polyethene insert from FEA was about 3.3 times that of the lower surface. The wear area obtained by FEA was basically consistent with that obtained by in vitro wear measurement. The main wear area was symmetrically distributed in the middle and back of the upper surface. Conclusions The mass wear rate of RHKP, as a semi-restrictive prosthesis, is obviously higher than that of primary total knee joint prosthesis. More attention should be paid to wear test and evaluation of RHKP.

Abstract:Objective To systematically explore the change of fixator stiffness (0.05-7.50 kN/mm) on healing effects of seven different types of fractures (A1: simple spiral, A2: simple oblique, A3: simple transverse; B2: wedge spiral, B3: wedge fragmented; C2: complex segment, C3: complex irregular) under the OTA/AO fracture classification. Methods Taking intramedullary nail fixation of long bone fracture as research objective, based on strain-regulated tissue differentiation theory, and combined with fuzzy logic algorithm and finite element analysis, the process of fracture healing was numerically simulated. Results Moderate fixator stiffness (1.5-2.5 kN/mm) shortened the healing time while ensuring recovery of biomechanical performance of the fractured bone. However, the appropriate fixator stiffness corresponding to each fracture type was different. The sensitivity of healing effects to change of fixator stiffness was also different. For type A fracture, when fixator stiffness was 1.5 kN/mm, optimal biomechanical recovery of the fractured site could be obtained, while the change in fixator stiffness had a large impact on healing effect. For type B and C fractures, when fixator stiffness was above 1.5 kN/mm, the change in fixator stiffness had no significant effects on recovery of biomechanical performance. Conclusions Fracture healing is affected by both fixator stiffness and fracture types. For treating fractures in clinic, the selection of fixators should carefully take fracture types into account.

Abstract:Objective To study distributions of stiffness and stress of each component in internal fixation system for long bone fractures composed of fractured bones (including callus) and bone plates，and propose a method for determining bending stiffness of fracture internal fixation implants. Methods Based on the linear bending theory and composite beam theory, the mechanical model of femoral shaft internal fracture fixing system composed of fractured bones and bone plate was constructed and verified with the finite element model based on artificial femur CT data. The relationship between stress and stiffness of the internal fixation system for long bone fractures was established. Results The three stages (slow-rapid-steady growth) for variation of fractured bone bending stiffness with callus elastic modulus obtained by calculation and analysis were consistent with the three stages of actual bone healing process, which proved accuracy of the theoretical calculation method. Changing patterns for the neutral axis position of internal fracture fixing system composed of fractured bones and bone plate were further obtained, namely, the neutral axis position was close to (away from) the central axis of bone plate when stiffness of bone plate increased (decreased). According to the stress required for fracture healing (0.72-0.80 MPa), the reasonable range for bending stiffness of bone plate was 0.99-4.20 kN·mm2. Conclusions When elastic modulus of the callus was 0.037.00 GPa, bending stiffness of the fractured bones increased rapidly, which was at the stage of bone bridge formation. When elastic modulus of the callus was above 7 GPa, the callus tended to mature. Based on the femur model in this study, when thickness of bone plate was 3.6-6.0 mm and elastic modulus of fractured bones was 3.013.5 GPa, the entire fractured bone section could be effectively stimulated. In this study, when bending stiffness of bone plate was 0.99-4.20 kN·mm2 during the generation stage of bone bridge, it was conducive to bone healing.

Abstract:Objective To study stress distributions of the cartilage around the hip joint in stress environment of complete gait cycle, and explore the optimal correction angle of bone block in curved periacetabular osteotomy (CPO), so as to provide theoretical references for clinical operation. Methods Based on CT scans from a healthy volunteer and a patient with development dysplasia of hip (DDH), the three-dimensional (3D) model including pelvis and proximal femur was reconstructed. The cortical bone and cancellous bone were distinguished by dividing the masks, and the material attributes were assigned to the finite element model. A total of 100 different postoperative models were obtained by simulating CPO in DDH model, by adjusting lateral center edge angle (LCEA) and anterior center edge angle (ACEA). According to hip joint stresses in complete gait cycle, the model was loaded respectively, and stress changes of normal, preoperative and postoperative acetabular cartilage were analyzed and compared. ResultsThe minimum peak contact stresses of acetabular cartilage of DDH patient at heel landing phase, start phase of single leg support, mid phase of single leg support, end phase of single leg support and double support phase after simulated CPO operation were 5.273, 6.128, 7.463, 6.347, 6.582 MPa, which were decreased by 2.159, 2.724, 2.249, 2.164, 2.119 MPa,respectively, compared with those before operation. The contact area between femoral head and acetabulum was significantly increased after operation, but it was still smaller than that of normal volunteers. Conclusions The optimal correction angle of LCEA and ACEA can be obtained by using finite element method, and the simulation of CPO surgery on different patients is of great significance to improve surgical accuracy and efficiency.

Abstract:Objective To study the effect of interlocking intramedullary nail on fixing transverse olecranon fracture. Methods Nine pairs of fresh ulna specimens were collected and the transverse fracture model of olecranon was established. Kirschner wire tension band and interlocking intramedullary nail were used to repair the fracture. Cyclic dynamic tension loads with amplitude of 25 N, mean value of 45 N and frequency of 05 Hz were applied to the triceps tendon under simulated elbow flexion conditions of 30°, 45° and 60°, respectively. The fracture displacements of specimens within 300 cycles were recorded in three groups. ResultsAt 30° flexion angle, the fracture displacement of interlocking intramedullary nail group and Kirschner wire tension band group was (1.831±0.333) mm and (3.723±2.390) mm, respectively. At 45° flexion angle, the fracture displacement of interlocking intramedullary nail group and Kirschner wire tension band group was (1.167±0.374) mm and (2.455±0.609) mm, respectively. At 60° flexion angle, the fracture displacement of interlocking intramedullary nail group and Kirschner wire tension band group was (1.407±0.342) mm and (3.112±1.025) mm, respectively. The fracture displacement of interlocking intramedullary nail was smaller. Conclusions The mechanical properties of interlocking intramedullary nail are better than those of Kirschner wire tension band, and the interlocking intramedullary nail is more stable and firmer for fixing transverse olecranon fracture. Moreover, the interlocking intramedullary nail is installed with the operating tool, thus the operation is more accurate and faster, and the operation efficiency is greatly improved.

Abstract:Objective To study the bone disuse behavior with electric field under low load stimulation frequency. Methods A disuse model was proposed to describe the effects of mechanical and electrical stimulation on bone remodeling through the activation frequency. By establishing the finite element model of proximal femur and using the finite element method， the process of bone remodeling under low load stimulation frequency coupled with electrical stimulation was simulated, and the loss of bone density was analyzed. Results The density was significantly decreased by decreasing the frequency of daily load stimulation frequency. The electrical stimulation could resist density loss caused by the low load stimulation frequency to a certain degree, and its main influence areas were distributed in the femoral head and femoral neck. The duration of electrical stimulation significantly affected density loss of the cortical bone and cancellous bone. Conclusions The model can simulate the process of disuse caused by the decrease of daily load stimulation frequency. Meanwhile, the effect of electric field is taken into account to show the resistance to bone density loss.

Abstract:Objective Aiming at solving the problem of poor accuracy for numerical solution of traditional finite element method (FEM) in numerical analysis on piezoelectric effects of bone remodelling, a model with an edge-based smoothed FEM (ES-FEM) was proposed. Methods The bone model was discretized by triangular elements, and the smoothing domain was constructed based on edges of the existing mesh element. Based on gradient smoothing technique, the smoothed strain gradient and the smoothed electric field gradient were obtained, and the discrete equations of the system were constructed under the framework of smoothed Galerkin weakform. Results The changes of bone mineral density (BMD) and the distributions of electric potential under piezoelectric effects in the process of bone remodelling were reflected by using the above model. Compared with FEM, ES-FEM could improve the accuracy of simulation result for bone remodelling to a certain extent. Conclusions The proposed ES-FEM can simulate the process of bone remodelling more accurately. The accurate prediction for piezoelectric effect of bone reconstruction by this method provides an effective theoretical basis for clinical research of bone diseases.

Abstract:Objective To investigate dynamic response of the finite element model of Lenke3 type scoliosis. Methods The finite element model was established based on CT scanning images from a patient with Lenke3 type scoliosis, and validation of the model was also conducted. Modal analysis, harmonic response analysis and transient dynamic analysis were carried out on the model. Results The first order natural frequency of this model was only 1-2 Hz.The amplitude of the finite element model was the largest at the first natural frequency. At the same resonance frequency, the amplitude of the thoracic curved vertebra was larger than that of the lumbar curved vertebra.The amplitude from T6 vertebra to L2 vertebra decreased successively. Conclusions The degree of spinal deformity may affect the perception of spine vibration, and the higher the degree of spinal deformity, the higher the sensitivity to vibration. The first natural frequency is most harmful to Lenke3 type scoliosis patients. Under cyclic loading, the thoracic curved vertebra is more prone to deformation than the lumbar curved vertebra. The closer to T1 segment, the greater the amplitude of the vibration is.

Abstract:Objective Based on computational fluid dynamics (CFD) method, the air and aerosol transport in a single alveolus were simulated to study the characteristics of airflow and aerosol transport in deep alveolus. Methods A long straight duct with a hemispherical wall at one end which had periodic expansion/contraction were regarded as simplified approximation of a single alveolus. Based on this, a two-dimensional (2D) mathematical model was established.The Euler-Euler method was used to solve the transport equations of airflow and aerosol particles in the alveolus considering air diffusion along the hemisphere boundary. Results The composition ratio of the air in the duct changed in a stable periodic way during the whole breathing process.The aerosol transport in the duct mainly depended on the particle diffusion coefficient. The advection transport had only a small effect on it. The diffusion velocity and depth of aerosol increased when the particle size decreased, especially when the particle size was smaller than 4 μm. The increase of respiratory frequency and amplitude could significantly improved the transport capacity of aerosol particles. Conclusions In atomization treatment, aerosol particles with smaller particle size have better transportation and curative efficacy. Deep breathing should be encouraged to improve particle transport.

Abstract:Objective T o analyze the influence of high flow nasal cannula (HFNC) on trespiratory mechanical parameters of the patient with acute respiratory distress syndrome (ARDS) based on ventilation experiment, and investigate the therapeutic and side effects of the HFNC. Methods The HFNC ventilation system model based on MATLAB and the physical experiment platform based on active simulated lung ASL5000 were developed to simulate the respiratory movement of ARDS patients with different lung compliance, and a series of the HFNC ventilation experiments were carried out. Both experimental results in MATLAB and physical platform were compared and analyzed. Results The results from the Matlab model-based simulation experiment and physical platform based-physical experiment uniformly showed that increasing the output flow of HFNC would decrease the relevant respiratory mechanical parameters of respiratory flow and tidal volume, but increase the intrapulmonary pressure and the functional residual capacity (FRC). Under the condition of small flow, the output flow from HFNC might be smaller than the inspiratory flow required by the patient, and an inspiratory compensation flow was necessary to make up for the inspiratory flow. Conclusions The necessary reliable compensation flow in inspiration will promote the security of HFNC. Understanding the changes in respiratory mechanical parameters of ARDS patient will be beneficial to pre-evaluate the HFNC, improve the ventilation effect and reduce the ventilation risks.

Abstract:Objective To study influencing factors of renal blunt impact injury by using finite element (FE) method. Methods Based on CT images of the kidney, the kidney FE models for different age groups were constructed. The renal blunt impact test was reconstructed, and the influence of kidney material constitutive parameters, kidney tissue structure, kidney size, impact position and impact velocity on injury severity were analyzed. Results Under the same impact condition, the stress of renal cortex decreased with the kidney mass increasing, and increased with the impact velocity of the hammer increasing. The renal capsule had a certain energy absorption effect, so as to reduce the kidney stress. When the kidney was impacted, the stress of renal cortex under side impact was significantly higher than that under frontal impact. Conclusions Compared with viscoelastic constitutive model, Mooney Rivlin material constitutive model is more suitable for FE evaluation on renal injury severity. The renal injury decreases with the kidney mass increasing. The increase of impact velocity will intensify the renal injury severity. Renal capsule will reduce renal injury to a certain extent, so the existence of renal capsule structure must be considered in FE modeling of the kidney. Compared with frontal and rear impact, the renal injury severity is greater when the kidney is impacted from the lateral side.

Abstract:Objective To study stress distributions of lower dentition distally moved with miniscrews in external oblique line area when the traction hooks with different lengths were placed at different positions by the three-dimensional (3D) finite element method. Methods Based on cone beam computed tomography (CBCT) data from a patient, traction hooks with the heights of 2 mm and 7 mm were constructed and fixed between the lateral incisors and the canine brackets, as well as between the canines and the first premolar brackets. Four kinds of 3D finite element models of full dentition distally moved with miniscrews were constructed. The 3 N traction force was loaded between the traction hook and the miniscrews. The maximum von Mises stress and initial displacement of the mandibular teeth and dentition under four working conditions were analyzed. ResultsWhen the traction hook with 7 mm-height was placed between the lateral incisor and the canine, the lower central incisor rotated clockwisely, with the crown moving labially and the root moving lingually. But under the other three working conditions, the central incisor rotated counterclockwisely, and the crown and root moved lingually. When the traction hook with 7 mm-height was placed between the canine and the first premolar, the lower canine crown moved proximally. But under the other three working conditions, both the crown and root moved distally. Under four working conditions, the mandibular molars all rotated counterclockwisely,with the crown and root moving distally. Conclusions Through 3D finite element analysis, biomechanical mechanism of the effect of different traction hooks on mandibular tooth movement during distalization of the lower dentition was elucidated.With full understanding of the biomechanical mechanism, proper selection for length and placement of the traction hook can achieve distal movement of the entire mandibular dentition more efficiently.

Abstract:Objective To compare the corneal biomechanical parameters identified from uniaxial tensile test under fast and slow loading. Methods The stress-strain and stress relaxation data were obtained from uniaxial tensile tests on corneal strips from 15 healthy adult rabbits at average loading rate of 0.16 mm/s and 0.02 mm/s, respectively. A visco-hyperelastic model was applied to analyze the loading and unloading data from the fast tensile tests, where the model parameter set was denoted by Gvh. The first-order Ogden model and second-order Prony series model were used to fit stress-strain and stress relaxation data from the slow tensile tests, respectively, in which the model parameter set was denoted by Gvh. Correlation analysis was used to compare the correlation of parameters between Gvh and GOP. Results All the goodness-of-fits to the three data sets were greater than 0.95. There were significant differences in 5 (μ, A1, A2, τ1, τ2,) of the 6 parameters between Gvh and GOP (P<0.05), and the Ogden model parameters was positively correlated between the two groups. Conclusions There are differences in corneal biomechanical parameters identified by data from uniaxial tensile tests under fast and slow loading. The results provide a preliminary research basis for further exploring the use of clinical data to identify corneal biomechanical properties.

Abstract:Objective To analyze the influence of plaque classification and bifurcation angle on hemodynamics in coronary artery, so as to further discuss the influence on vulnerable atherosclerotic plaques. Methods Based on average geometric parameters of human coronary bifurcation vessels, the model of fluid-solid interaction for coronary bifurcation vessels with different plaque classifications and vessel bifurcation angles was constructed, and the distributions of blood flow velocity, pressure and shear stress at critical positions were investigated. Results The upstream shoulder of the plaque was the site with the highest shear stress on plaque surface, which was prone to ulceration or rupture with further growth. When there were plaques on one side of the bifurcation vessels, the shear stress at the carina of bifurcations was greater than that at the bilateral plaques. The pressure and shear stress at the carina of bifurcations gradually increased as the bifurcation angle decreased. Conclusions When there are plaques on one side of the bifurcation vessels, the probability of ulceration or rupture is greater. The presence of plaque in main vessels can promote formation and growth of the plaque at bifurcations. The inner wall of blood vessels at the carina of bifurcations is more easily damaged in the case of small angle vessels. The results can provide theoretical references for the design and optimization of vulnerable atherosclerotic plaque treatment.

Abstract:Objective To evaluate the rupture risk of carotid atherosclerotic plaque under cervical rotatory manipulation. Methods The fluid-structure interaction (FSI) model of carotid atherosclerotic plaque was established, and tensile deformation of the plaque and lumen under cervical rotatory manipulation was simulated.Mechanical parameters such as the maximum flow shear stress(FSS), the maximum wall shear stress (WSS), the maximum plaque wall stress (PWS), wall tensile stress (WTS) and wall pressure (WP) of the plaque and lumen were recorded. Results Under 16% carotid tensile deformation, the maximum WSS of the plaque was 40.54 Pa. The maximum PWS was 66.16 kPa, which was far smaller than the threshold of plaque rupture.The maximum WTS of fiber cap and the maximum strain were 156.75 kPa and 0.56, which were larger than the fracture strain range. The maximum WTS of the lumen was 1 040.30 kPa, which approached the threshold of medial membrane rupture and might cause vascular injury. Conclusions When the cervical spine rotates to the end range of motion, large carotid artery stretch may cause damage to epidermal tissues of the plaque, leading to abscission. Lesions, ulcers, bleeding and vascular damage may form inside the plaque, which will affect stability of the plaque. Cervical rotatory manipulation should be performed cautiously in patients with cervical diseases who also have carotid atherosclerotic plaques.The finite element assessment of plaques before manipulation may be an effective safety screening method.

Abstract:Objective To study mechanical properties of polyethylene terephthalate (PET)-based textile valves woven with nickel-titanium (NiTi) wires by finite element method, and combined with in vitro hemodynamic testing, to analyze the effect of wire quantity and woven position on hemodynamic performance of PET textile valve. Methods The three-dimensional (3D) geometric models of PET valves without wires and models of PET valves with wires by different numbers and distributions in radial direction were constructed using modeling software. Material properties of PET valves and wires were given based on the literature and experimental data. The transvalvular pressure difference curves of PET valves obtained from in vitro pulsatile flow experiments were used as boundary conditions. Stress distributions of the valve during peak systole and diastole were studied by finite element analysis software. Hydrodynamic performance of the valve with wires was evaluated by in vitro pulsatile flow experiments. ResultsThe finite element analysis results showed that the radially woven NiTi wires could enhance support for the PET textile valve, and support force and area of the valve in belly region of the valve leaflet with evenly distributed metal wires increased with the number of metal wires. The situation of support force was similar for silk distributions on both sides of the belly. The weaving of wires reduced stress concentration on the PET textile valve to a certain extent. The pulsatile flow experiment results showed that the stability of opening and closing shapes, effective opening area (EOA), regurgitation fraction (RF) and transvalvular pressure differences for two kinds of the PET valves with woven wires were better than those of the PET valves without wires. Conclusions Weaving metal wires in radial direction of the PET textile valve can effectively reduce stress concentrations on the PET textile valve during the cardiac cycle, and reduce tearing possibility of the valve leaflet. The woven metal wires can improve opening and closing stability of PET textile valve in in vitro hydrodynamic test, increase EOA and reduce RF and transvalvular pressure difference of the PET valve.

Abstract:Objective To study von Willebrand factor(VWF) damage based on a novel Maglev Taylor-Couette blood-shearing device. Methods The magnetic levitation (maglev) Taylor-Couette blood-shearing device was designed, and the blood-shearing platform was built. Fresh porcine blood was tested in circulation loop for 1 hour at laminar flow state. VWF damage was assessed by analyzing sample through Western blot and enzyme-linked immunosorbent assay. Results With the increase of exposure time and shear stress, a large number of high molecular weight VWF multimers were degraded into low molecular weight VWF. The maximum rate of degradation was 569%. When the shear stress increased from 18 Pa to 55 Pa, the ratio of VWF-Rco to VWF-Ag decreased from 45.7% to 32.8%. ConclusionsCompared with initial sample, the VWF damage was mainly manifested by the decrease of high molecular weight VWF and the decrease of VWF activity, and VWF-Ag did not change significantly. The novel maglev Taylor-Couette blood-shearing device can quantitatively control the flow parameters (exposure time and shear stress), and be used for blood damage research in vitro, thus providing references for the design and optimization of extracorporeal membrane oxygenation and blood pump.

Abstract:Objective To establish the method of predicting the vertical ground reaction force (vGRF) during treadmill running based on principal component analysis and wavelet neural network (PCA-WNN). Methods Nine rearfoot strikers were selected and participated in running experiment on an instrumented treadmill at the speed of 12, 14 and 16 km/h. The kinematics data and vGRF were collected using infrared motion capture system and dynamometer treadmill. A three-layer neural network framework was constructed, in which the activation function of the hidden layers was the Morlet function. Velocities of mass center of the thigh, shank and foot as well as joint angles of the hip, knee and ankle were input into the WNN model. The prediction accuracy of the model was evaluated by the coefficient of multiple correlation (CMC) and error. The consistencies between predicted and measured peak GRF were analyzed by Bland-Altman method. Results The CMC between the predicted and measured GRF at different speeds were all greater than 0.99; the root mean square error （RMSE） between the predicted and measured vGRF was 0.18-0.28 BW; and the normalized root mean square error (NRMSE) was 6.20%-8.42%; the NRMSE between the predicted and measured impact forces and propulsive forces were all smaller than 15%. Bland-Altman results showed that the predicted peak errors of propulsive force at 12 km/h and that of impact force and propulsive force at 14 km/h were within the 95% agreement interval. Conclusions The PCA-WNN model constructed in this study can accurately predict the vGRF during treadmill running. The results provide a new method to obtain kinetic data and perform real-time monitoring on a treadmill, which is of great significance for studying running injuries and rehabilitation treatment.

Abstract:Objective To study changes in kinematics and joint coordination of the waist and hips during sit-to-stand and stand-to-sit tasks in patients with lumbar disc herniation (LDH). Methods The Vicon 3D motion capture system was used to collect the kinematics data from 20 healthy controls and 20 LDH subjects, and differences in movement patterns of the lumbar spine and hip joints during sitting and standing tasks were compared between two groups through statistical parametric mapping (SPM). Results During sit-to-stand task, the lumbar spine flexion and extension range and hip joint abduction angle of LDH subjects were significantly limited, and the hip flexion angle increased. SPM analysis showed that for both groups at initial stage of sit-to-stand (10%-13%), there was a statistically significant difference in flexion angle of the lumbar spine, and lumbar flexion angle of LDH subjects was significantly reduced, while hip flexion angle at 2%-14% phase was significantly increased. During stand-to-sit phase (65%-69%), LDH subjects showed increased hip abduction angle. Conclusions LDH subjects have limited lumbar flexion and hip abduction functions during sitting and standing, and they need to be compensated with increased hip flexion activities to complete functional tasks. In clinical evaluation, changes in motor function of the spine and hips should be focused on.

Abstract:Objective To analyze the changes in morphology of intervertebral foramina in patients with cervical spondylotic radiculopathy (CSR) treated with fixedpoint lateral flexion and rotation manipulation based on three-dimensional (3D) reconstruction technology, so as to provide references for the effectiveness of manipulation treatment. MethodsForty patients with CSR were treated with fixed point lateral flexion and rotation manipulation once every other day for a total of 7 times and 2 weeks as a course of treatment. CT data of the patients before and after treatment were analyzed by using multifunctional CT, Mimics 21.0, Geomagic and SolidWorks 2017. The area of the intervertebral foramen, anterior and posterior diameter of the intervertebral foramen, upper and lower diameter of the intervertebral foramen were measured before and after treatment, as well as the infrared thermal imaging temperature differences of the bilateral neck and shoulder, front and back of the upper limb, and the VAS scores of the patients were observed before treatment, 7 d after treatment, 14 d after treatment and 1 month follow-up. Results Foraminal area, anterior and posterior diameters, upper and lower diameters of 40 patients were improved after treatment, and the temperature differences of infrared thermal imaging of patients before and after treatment were statistically significant. The VAS score of the patients decreased progressively. Conclusions Fixed point lateral flexion manipulation can significantly improve the shape of the intervertebral foramen in patients with CSR, so as to achieve the treatment purpose of relieving nerve compression.

Abstract:Objective To analyze and assess the postoperative motor function in children with spastic cerebral palsy (SCP) by surface electromyography (sEMG) and joint angle. Methods Sixteen children with SCP were involved in this study. The sEMG of rectus femoris, biceps femoris, semitendinosus, tibialis anterior, lateral gastrocnemius and medial gastrocnemius muscles and joint angles of the hip, knee and ankle during straight walking were collected preoperatively and postoperatively. In every gait phase, the mean values of joint angles, root mean square and integrated electromyography of sEMG were calculated, to evaluate muscle strength and muscular tension quantitatively. Results The muscle tension of lower limbs was significantly decreased (P＜0.05). The muscle strength of rectus femoris and biceps femoris was decreased in the swing phase. At the midswing and terminal swing phase, the strength of tibialis anterior increased significantly (P＜0.05). The flexion angle of hip and knee decreased significantly (P＜0.05). The dorsiflexion angle of ankle increased significantly (P＜0.05), and the varus angle decreased significantly (P＜0.05). Conclusions After operation, the crouching gait and clubfoot were improved positively. Therefore, the motor function of children was improved. Combining sEMG and joint angle can evaluate the muscle function of patients quantitatively, and it also can provide references for clinical diagnosis.

Abstract:Objective Taking three-dimensional (3D) motion capture system (MoCap) as the gold standard, a deep learning fusion model based on bi-lateral long short-term memory (BiLSTM) recurrent neural network and linear regression algorithm was developed to reduce system error of the Kinect sensor in lower limb kinematics measurement. Methods Ten healthy male college students were recruited for gait analysis. The 3D coordinates of the reflective markers and the lower limb joint centers were simultaneously collected using the MoCap system and the Kinect V2 sensor, respectively. The joint angles of lower limbs were calculated using the Cleveland clinic kinematic model and the Kinect kinematic model, respectively. The dataset was constructed using the MoCap system as the target and the angles via the Kinect system as the input. A BiLSTM network and a linear regression model for all lower limb angles were developed to obtain the refined angles. A leave-one subject-out cross-validation method was employed to study the performance of the models. The coefficient of multiple correlations (CMC) and root mean square error (RMSE) were used to investigate the similarity and the mean deviation between the joint angle waveforms via the MoCap and the Kinect system. ResultsIn comparison with the linear regression algorithm, the BiLSTM had better performance in the aspect of dealing highly nonlinear regression problems, especially for hip flexion/extension, hip adduction/abduction, and ankle dorsi/plantar flexion angles. The deep learning refined model significantly reduced the system error of Kinect. The mean RMSEs for all joint angles were mainly smaller than 10°, and the RMSEs of the hip joint were smaller than 5°. The joint angle waveforms presented very good similarity with the golden standard. The CMCs of joint angles were greater than 0.7 except for hip rotation angle. Conclusions The markerless gait analysis system based on deep learning fusion model developed in this study can accurately assess lower limb kinematics, joint mobility, walking functions, and has good prospect to be applied in clinical and home rehabilitation.

Abstract:Objective To explore dynamic characteristics of the gait for the elderly with different fall risks before and after obstacle crossing. Methods Twenty-seven elderly people in community were graded as fall risk by using the time up and go test and five-time sit to stand test. The plantar pressure parameters of the elderly before and after obstacle crossing were measured and analyzed by foot pressure measurement system. Results There was no significant difference in the characteristic value of bimodal curve of overall plantar pressure between the high and low fall risk groups before and after obstacle crossing(P>0.05). The center of pressure (COP) trajectory in X direction of high fall risk group after obstacle crossing was significantly greater than that of low fall risk group (P<0.05). Before obstacle crossing, the peak pressure of the 3rd metatarsal of supporting foot was higher in high fall risk group than that in low fall risk group (P<0.05). After obstacle crossing, the peak pressure of the 1st phalanx of supporting foot was significantly lower than that in high fall risk group (P<0.05), while the lateral heel impulse in high fall risk group was significantly larger than that in low fall risk group (P<0.05).The distribution patterns of contact area of the foot for the elderly in two groups before and after obstacle crossing were basically the same, and there was no significant difference in contact area of each plantar region (P>0.05). Conclusions The support time of the elderly with high fall risk is longer than that of the elderly with low fall risk during obstacle crossing, the peak pressure of plantar metatarsal region of the crossing leg increases, and the plantar COP curve shows asymmetry, with an increase in transverse range of the coronal plane. In clinical evaluation, plantar pressure characteristics of people with fall risks during obstacle crossing should be focused on.

Abstract:Objective To develop plantar force model of patellofemoral pain (PFP), so as to provide theoretical references for the assessment of PFP rehabilitation. Methods The case-control study was conducted, and a total of 126 patients with PFP and 126 healthy controls matched by gender and age were enrolled in the study. The participants were tested for plantar force and pressure during level walking, and twelve plantar regions were divided and recorded. Whether the participants suffered PFP was analyzed as dependent variable, meanwhile the peak force and peak pressure in 12 plantar regions of participants at selected speed during level walking were analyzed as independent variables. Conditional logistic regression (CLR) equations of peak force and peak pressure with PFP were established, respectively. The receiver-operating characteristic (ROC) curve of the corresponding equations was derived, and the area under ROC curve was calculated to analyzed the validity of different equations on PFP assessment. Results The CLC equation of peak force in 12 plantar regions of the participants with FFP was constructed, and only peak force of lateral heel was in the equation. The CLC equation of peak pressure in each plantar region included medial heel, midfoot, 1st and 2nd metatarsals. Meanwhile, the area under ROC curve of the pressure equation was larger than that of the force equation. Conclusions Peak force and pressure at different plantar regions can be used to assess PFP during level walking, and peak pressure is more effective for assessment.

Abstract:Objective To analyze the impact of soldiers’ single-leg landing with load carriage on knee joint, and investigate its relationship with muscle strength, so as to provide references for daily load carriage training. Methods A total of 12 soldiers were required to perform single-leg landing from the 30 cm height without load carriage and with 15 kg load carriage,respectively.The kinematic and kinetic parameters were collected using Vicon motion capture system and AMTI force platform. The surface electromyography (sEMG) of anterior and posterior thigh muscles were also collected simultaneously, and the isokinetic strength during knee flexion and extension was tested. Results Compared with landing without load carriage, knee flexion angle and joint reaction force significantly increased during landing with 15 kg load carriage (P<0.05).The maximum sEMG of rectus femoris, lateral and medial femoral, biceps femoris increased significantly(P<0.05), but there were no significant differences in other indexes without and with load carriage(P>0.05). There was a significant negative correlation between peak moment of knee extension and vertical ground reaction force during single-leg landing without load carriage (P<0.05), while other indexes had no significant correlations (P>0.05). Conclusions Knee flexion angle and joint reaction force significantly increase during single-leg landing with 15 kg load carriage, the activation of anterior and posterior thigh muscles can relieved the ground reaction force during landing, and muscle strength plays some role in preventing landing injury.

Abstract:Older adults have decreased control of body balance with aging and are prone to fall. As the primary point of contact between human body and ground, footwear is critical for stability of older adults. The relationship between shoe characteristics and stability of older adults was systematically reviewed to determine the effect of footwear characteristics on stability of older adults. The results show that wearing shoes with shoelaces or velcro, low heels, wide outsole and appropriate soles， or using vibrating insoles and arch support insoles can help older adults improve their stability. Excessive sole spring and low sole hardness may have adverse effects on stability of older adults. This study can provide theoretical references for older adults to choose shoes reasonably and for the manufacturers to design and make shoes to prevent falls.

Abstract:Finite element method (FEM) has become an effective tool for biomechanical researches because of its high efficiency, accuracy and repeatability. Due to the complex anatomical structure and motion characteristics of foot and ankle, FEM can solve the problems that are difficult to be solved in real experiments with the help of powerful simulation modeling and data calculation ability, which has unique advantages and has been widely used. In this paper, the literatures on foot and ankle biomechanics using FEM at home and abroad in recent five years were summarized, and the following 4 aspects were reviewed: biomechanical analysis of foot and ankle under different motion states, researches on tissue characteristics, clinical treatment analysis, and researches on orthosis and shoes, so as to provide theoretical references for the study of foot and ankle biomechanics, as well as new ideas for the application and development of FEM in the field of foot and ankle biomechanics in the future.

Abstract:According to its location and function, the oral mucosa can be divided into masticatory mucosa, coated mucosa and special mucosa. Oral masticatory mucosa, including hard palate and gingival mucosa, bears the chewing pressure and friction, and plays an important role in denture restoration. The study on biomechanics of oral masticatory mucosa is helpful to better understand and solve clinical problems related to oral masticatory mucosa. In this review, the progress of biomechanical researches on oral masticatory mucosa was summaried from three aspects: anatomical and physiological analysis, biomechanical characteristics (stress-strain curve, Poisson’s ratio, friction coefficient) and clinical significance, in order to provide further theoretical basis for the researches in oral prosthodontics-related areas.