Objective Two different venous models,one with and one without a venous sinus,each containing two pairs of adjacent orthogonal venous valves,were constructed.Using fluid-structure interaction(FSI)simulations,the influence of the venous sinus structure on blood flow in the lower limb venous system was studied,and the role of the venous sinus structure in the process of venous valve opening and closing was analyzed.Methods Based on ultrasound images and anatomical images of animals,two distinct three-dimensional(3D)geometric models of the venous system were constructed using modeling software.Using the immersed boundary method,FSI simulations of venous valves were performed to obtain hemodynamic parameters,such as changes in valve morphology,flow streamline distribution,wall shear stress(WSS)distribution,and Q-criterion intensity distribution.Results The geometric opening area of the valve in the model with sinuses was larger than that in the model without sinuses.The distribution of blood streamlines demonstrated the existence of vortices in the sinus region and helical flow within the vessel.The same venous valve pair exhibited an asymmetric distribution of WSS,with the region of high WSS behind the venous valve and the Q-criterion intensity between the far and near end valves being smaller in the sinus model compared to the non-sinus model.Conclusions The blood flow between two adjacent pairs of orthogonal venous valves exhibits a helical flow characteristics.The venous sinus structure facilitates the opening of the venous valve and the generation of vortices in the sinus region.However,the venous sinus structure may somewhat weaken the helical flow produced by the orthogonal venous valves.The venous sinus has a critical influence on the hemodynamics of the venous system,and in the study of venous valves,the venous sinus structure should be considered as an indispensable component.

Objective To investigate the impact of variations in volute cross-sectional area on the flow characteristics and hemolytic performance of centrifugal blood pumps by designing six volute structures.Methods Computational fluid dynamics and the Lagrangian method were used to analyze flow characteristics and predict hemolysis in blood pumps with different volute designs.Results The annular volute pump showed the poorest hydraulic performance,while the hydraulic performance of the S-shaped volute was the best,which was improved by 35.29％compared to that of the annular volute.Some volutes experienced stagnation zones at the helical inlet(0°-90°)and significant backflow at the outlet(270°-360°).The downward concave-shaped volute had the highest hemolysis index(HI),i.e.,9.59×10-4.Meanwhile,the HI of the annular volute was the lowest,which was 71.85％less than the concave-shaped volute.Conclusions Reducing the gradient of the area variation at the helical inlet and outlet can prevent flow stagnation and backflow.A higher HI arises due to the prolonged exposure of red blood cells to high shear stress.This study provides a theoretical basis for designing and optimizing volute structures of centrifugal blood pumps.

Objective To investigate the correlation between the change of muscle tissues and bone mineral density(BMD)in elderly women with hip fracture,with consideration of the impact of muscle mechanics on bone mass changes.Methods A total of 79 elderly patients with hip fracture were selected as the fracture group,and 45 physical examination personnel as the control group.The differences in total muscle mass,total body fat,trunk muscle mass,trunk fat mass,arm muscle mass,arm fat mass,leg muscle mass,leg fat mass,as well as BMD at the lumbar spine(L1-4),femoral neck,hip joint,and whole body were analyzed.Results Muscle content and fat content of the whole body,upper limb and lower limb,fat content of the trunk,relative skeletal muscle index(SMI)and BMD of the whole body in fracture group were significantly lower than those in control group(P＜0.05).The incidence rate of sarcopenia for elderly women in fracture group was higher than that in control group.BMD of femoral neck of the affected side was significantly lower than that of the intact side in women with intertrochanteric fractures.Logistic regression analysis found that SMI in elderly women with hip fracture was negatively correlated with age,and positively correlated with body mass index(BMI),BMD of the femoral neck and whole body.Conclusions The rate of sarcopenia was significantly higher in elderly patients with hip fracture,and SMI was closely related to BMD of the femoral neck and whole body.Therefore,sarcopenia should be highly emphasized in the prevention and treatment of osteoporotic fracture in elderly people.

Objective To evaluate the safety and therapeutic efficacy of three-dimensional(3D)-printed personalized cervical correction pillows for treating cervical spondylotic radiculopathy.Methods A finite element model was established to simulate and analyze the biomechanical changes in cervical spine before and after using the pillow.Additionally,20 patients with chronic neck pain were included to analyze changes in visual analogue scale(VAS)scores,neck disability index(NDI),pressure pain threshold(PPT),Borden value,cervical lordosis,T1 slope,cervical slope,and thoracic inlet angle before and after using the pillow.Results Finite element analysis indicated that the maximum stress on vertebral bodies increased by 64.35％and the maximum stress on cartilage tissues by 5.09％after using the pillow.The Borden value improved by 45.75％.Clinical studies showed a significant reduction in VAS scores,NDI,and PPT after treatment(P＜0.05),while PPT,Borden value,cervical lordosis,T1 slope,and thoracic inlet angle significantly increased(P＜0.05).Conclusions The 3D-printed personalized cervical correction pillow is safe and effective in alleviating neck pain and improving cervical curvature,and it provides a new and effective non-surgical treatment option for cervical spondylotic radiculopathy,with significant clinical implications.

Objective Two neural network algorithm models were constructed to estimate the three-dimensional(3D)ground reaction force(GRF)and center of pressure(COP)during walking,and the estimation results of two algorithm models were compared,so as to provide a solution for the acquisition of gait dynamics data without force plate.Methods A total of 1 384 gait data were selected.Multi-layer perceptron(MLP)and convolutional neural network(CNN)were applid to construct models for estimating GRF and COP components based on the 3D trajectories of whole-body markers.100 samples were randomly selected as the test set,and the estimation performance was evaluated by the correlation coefficient(r),relative root mean square error(rRMSE).Paired-sample t-tests were used to compare the estimation performance of the two neural network models.Results The r values of each components of GRF estimated by MLP were 0.954-0.993,and the rRMSEs were 4.36％-9.83％.The rvalues of each component of GRF estimated by CNN were 0.979-0.994,and the rRMSEs were 3.06％-6.69％.The rvalues of each component of COP estimated by MLP were 0.888-0.992,and the rRMSEs were 4.78％-16.63％.The rvalues of each component of COP estimated by CNN were 0.944-0.995,and rRMSEs were 3.06％-10.85％.The RMSEs of CNN in estimating the medio-lateral component of GRF,the medio-lateral and antero-posterior components of COP during right stance phase,as well as the medio-lateral and antero-posterior components of COP during left stance phase were all lower than those of MLP(P＜0.01).The RMSEs of MLP in estimating the anterior-posterior component of GRF during right stance phase,as well as the anterior-posterior component of COP and the vertical direction of GRF during left stance phase were lower than those of CNN(P＜0.01).Conclusions Both MLP and CNN achieved good estimation accuracy in estimating GRF and COP during walking based on the trajectories of whole-body markers.The estimation accuracy of MLP in estimating the anterior-posterior components and vertical component of GRF was better than that of CNN,while the estimation accuracy of CNN in estimating the medio-lateral component of GRF,the anterior-posterior and medio-lateral components of COP were better than that of MLP.

Objective To investigate the effects of wearing high-heeled shoes at different heel heights on ankle joint motion control during walking in women with chronic ankle instability(CAI).Methods The Vicon infrared motion capture system and a three-dimensional force plate were used to synchronously collect kinematic and kinetic parameters within 200 ms before and after foot contact for 20 healthy females and 20 CAI females while walking on flat ground wearing high-heeled shoes at different heel heights(1,3,5,and 7 cm).Two-way repeated measures ANOVA was applied to analyze the data statistically.Results There was an interaction effect between group and heel height on the peak inversion angular velocity and peak inversion angle during foot strike.Post-hoc tests revealed that within the healthy group,compared to a 1 cm heel,the 5 cm(P=0.002)and 7 cm(P=0.002)heels had significantly greater peak inversion angular velocity within 200 ms before and after foot strike;there were significant differences in peak inversion angle between the 1 cm and 5 cm(P=0.018),7 cm(P＜0.001)heels.In the CAI group,compared to a 1 cm heel,the 5 cm(P=0.002)and 7 cm(P=0.002)heels had significantly greater peak inversion angular velocity within 200 ms before and after foot strike;there were significant differences in peak inversion angle between the 1 cm and 3 cm(P＜0.001),5 cm(P＜0.001),7 cm(P＜0.001)heels.There was a significant main effect of height on peak plantarflexion angle(P＜0.001),peak external rotation angle(P＜0.001),peak external rotation angular velocity(P＜0.001),and peak plantarflexion torque(P=0.048)within 200 ms before and after foot strike;there was a significant main effect of group on peak eversion torque(P＜0.001).Conclusions Compared to healthy individuals,women with CAI have reduced ankle joint control while walking with high-heeled shoes.As heel height increases,the ankle stability decreases.It is recomended that women with CAI should wear high-heeled shoes with a heel height of 3 cm or below.

Objective To explore limb coordination patterns and energy flow strategies during the sit-to-stand(STS)transition in individuals with patellofemoral pain(PFP),so as to provide a theoretical evidence for the pathogenesis of PFP and subsequent formulation of treatment and rehabilitation strategies for PFP patients.Methods A totoal of 36 participants was recruited for the STS test.They were divided into the unilateral PFP group(unilateral group),bilateral PFP group(bilateral group),and control group,based on the number of limbs affected by PFP.An infrared motion capture system and a three-dimensioanl force plate were used for motion capture.Visual 3D and Matlab software were used to calculate the trunk and pelvis angles,angular velocities,linear velocities,and proximal and distal joint forces.Additionally,the angles,torques,and joint forces of the hip,knee,and ankle joints,along with the angular and linear velocities of the thigh and shank,were computed.Coupling angles was used to represent coordination patterns via vector coding;the segmental net energy integration method was used to calculate energy flow within segments at each stage.Results For the coordination pattern at frontal plane,the proximal coordination mode frequency of the pelvis-hip coordination in the flexion momentum phase(FMP)was higher in unilateral group than that in bilateral group(P=0.024).In the momentum transfer phase(MTP),the frequency of in-phase coordination in the trunk-pelvis coordination was higher in unilateral group than that in bilateral group(P=0.023),while the frequency of distal coordination was higher in control group than in that in unilateral group(P=0.032).For the knee-ankle coordination pattern,the frequency of distal coordination in control group was lower than that in unilateral and bilateral groups(P=0.025,P=0.005).In segmental energy flow,during the FMP,the energy output from the pelvis during extension phase(MP)was higher in bilateral group than that in control group(P=0.021).Conclusions PFP affects energy flow patterns and coordination patterns at frontal plane during the STS transition.Individuals in unilateral group may engage in lateral pelvic and ankle movements as a dynamic compensation for patellofemoral joint pressure,whereas individuals in bilateral group appear to increase pelvic region energy output and employ a more complex whole-body coordination pattern to compensate for functional deficits in the knee caused by PFP.

Objective To study the variations in lower limb muscle strength and gait after long-distance load marching in soldiers and to investigate the effects of muscle fatigue of the lower limbs on the walking and running gait.Methods Fifteen male soldiers completed a 15 km march with a 17.5 kg load carriage.The isometric muscle strength of the hip,knee,and ankle joints under flexion and extension were tested.The walking and running gait parameters were collected with a Vicon motion capture system and AMTI force platform.Results After load marching,the peak moment of the hip decreased significantly(P＜0.05),the mean power of the right knee decreased significantly(P＜0.05),and the relative peak moment and mean power of the ankle plantar flexion decreased significantly(P＜0.05).During walking,the left hip flexion,knee flexion and extension,ankle dorsiflexion,and inversion angles(P＜0.05)decreased significantly in conjunction with a significant increase in the knee inversion angle(P＜0.05).Additionally,the moments of left hip flexion,knee flexion,ankle plantar flexion,and bilateral knee inversion(P＜0.05)decreased significantly,coupled with a significant increase in the moments of right hip extension and vertical ground reaction forces(P＜0.05).During running,the step frequency decreased significantly(P＜0.01),and the left step width increased(P＜0.05).Both left and right ankle dorsiflexion angles decreased significantly(P＜0.05),whereas the knee adduction angle increased significantly(P＜0.05).Additionally,the moment of bilateral hip flexion,left knee flexion,right ankle dorsiflexion,and knee adduction decreased significantly(P＜0.05),and the ground reaction force on the right side increased significantly(P＜0.05).Conclusions The lower limb muscle strength decreased after long-distance marching.This was particularly so in the hip joint.The hip drive mechanism was used in the walking gait after marching.However,knee hyperextension and valgus occurred owing to the decreased muscle strength.The ankle joint was used more frequently during running.This increased the risk of ankle injury.It is necessary to strengthen the hip and hamstring muscle groups to optimize the gait,increase the load capacity,and prevent injury.

Objective The finite element pelvis model with detailed anatomical structures which meets the Chinese human 95th percentile characteristics is developed,and the influence of cortical bone modeling method on the biomechanical response of the real pelvis is explored.Methods Based on the pelvic medical images of a 95th percentile male volunteer,two finite element pelvis models with real hip bone cortical bone thickness(REA-M)and 2 mm uniform cortical bone thickness(CON-M)dominated by hexahedral elements were constructed.Using the simulation method to reconstruct the loading conditions of cadaver experiments,the validation of models was verified by comparing the cadaver experimental results and simulation results,and biomechanical response differences of two models under different working conditions were discussed.Results The simulation data showed that there was a strong correlation between the overall biomechanical responses of two pelvic models and the cadaver experiment,and the mechanical response difference between two models was mostly within 8％,and the correlation score difference between two models was smaller than 2％.Conclusions The validation of two pelvic models established in this study is verified by rebuilding multiple simulation experiments.Although the biomechanical responses of CON-M and REA-M models were different,the difference was small.From the perspective of model simplification,the CON-M model can be used to study the biomechanical response of the pelvis.

Knee adduction moment(KAM)is a key biomechanical index in knee joint biomechanics research,which is closely related to the occurrence and development of knee osteoarthritis(KOA).Therefore,understanding the factors influencing KAM is important for the diagnosis and treatment of KOA diseases.This review summarizes the factors that may affect KAM based on relevant research.