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.

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,the step length(P=0.004)and cadence(P=0.001)of patients with PFP in the listening integration task were significantly reduced.Furthermore,both variables exhibited a negative correlation with PFJS(P<0.05).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(P<0.05).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)of patients with PFP in the visual integration task were increased.These biomechanical characteristics exhibited a positive correlation with PFJS(P<0.05).Conclusions The listening integration task decreases the step length and cadence of patients with PFP,and the tactile and visual integration tasks increase the hip and ankle internal rotation angles.On this basis,the visual integration task also increases the knee flexion angle and ankle plantarflexion angle during walking.Overall,the visual integration task has the greatest effect on gait biomechanics of female patients with PFP,and changes in these biomechanical characteristics are associated with elevated PFJS.

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 could 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 8.65×10-4.When the upper and lower axial clearance was 0.7 mm,the HI was the smallest,which was 4.51×10-4.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.

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 method,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's anatomical basis,measurement method,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.

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 suboptimal bone ingrowth within the scaffolds and subsequent prosthesis loosening and failure post-operation.Bone is a highly force-responsive organ,and its fate is regulated by biomechanical signals.Consequently,designing scaffolds with consideration of biomechanical principles to ensure mechanical compatibility between the scaffolds and the bone defect sites is a critical factor influencing the success of bone defects reconstruction.This review primarily 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.

Objective To observe the differences in dynamic stability and kinematic/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.

Objective To investigate the dynamic features of patients with patellofemoral pain(PFP)during running by using support vector machine(SVM)classifier and feature selection method,so as to provide a 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 method.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.

Objective To explore the immediate impact of acute vision changes in hemiplegic patients on their gait.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 affect the gait of hemiplegic patients,especially in individuals with high myopia presenting both a notable decrease in walking speed and an increased ankle range of motion,and an increase in walking speed with moderate myopia.Meanwhile,the symmetry of the COP decreases,indicating that acute vision changes lead to a higher risk of falls for patients.Reasonable vision assessment and corresponding intervention measures are expected to improve walking ability and life quality of the patients.

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 this orthosis.Results The orthosis would reduce the knee angles during level walking,as well as the knee 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 joints.During ascending and descending stairs,the knee angle change on the wearing side was opposite to that on the non-wearing side.The increase of the peak knee angle was(14.3±3.6)%on the non-wearing side during ascending stairs.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.

Objective By applying the long short-term memory(LSTM)neural network model and using lower body landmark coordinates obtained from a markerless motion capture system as inputs,to estimate ground reaction force(GRF)curves during running.Methods The video images and GRF data of 59 amateur runners during running were collected by the markerless motion capture system and three-dimensional(3D)force plates.The LSTM model was established,and the 3D coordinates of 11 lower body landmarks,obtained via the Theia3D markerless system,were used as inputs to estimate the 3D GRF curves during the stance of running.The estimation performance was evaluated using correlation coefficients r,root mean square error(RMSE),and normalized root mean square error(nRMSE)by comparing LSTM model estimation and force plate measurement.Statistical parametric mapping was used to analyze differences in GRF curves estimated by the LSTM model and measured by the force plate,while paired t-tests were used to assess differences in GRF characteristics between model estimation and actual measurement.Results A strong correlation(r＞0.85,P＜0.001)and lower error(RMSE＜0.3 body weight,nRMSE＜15％)was found between the LSTM model estimation and actual measurements.No significant difference was found in GRF curve intervals between LSTM model estimation and actual measurements.There was no significant difference in GRF characteristics between LSTM model estimation and actual measurements(P＞0.05).Conclusions Based on the LSTM model,the 3D GRF curves can be effectively estimated by lower body landmark coordinates obtained from the makerless motion capture system,thereby acquiring the highly accurate GRF characteristics.The LSTM model developed in this study can be used to monitor injury risks during running in outdoor environments.