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Abstract:With the in-depth understanding of biomechanics and mechanobiology mechanisms, there is a significantly increasing interest in the applications of mechanical principles to the treatment of diseases, resulting in the emerging field of mechanotherapy. Meanwhile, the combination of biomaterials and mechanotherapy provides diverse and sophisticated methods for therapeutic intervention. In this review, with the focus on recent advancements in biomaterial applications within mechanotherapy in 2022, a comprehensive summary of various multiscale mechanotherapy techniques was provided, namely, at organ and tissue, micro-tissue, cellular and sub-cellular, and molecular scales. By exploring how biomaterials can serve for mechanotherapy applications, the review aims to inspire interdisciplinary research and accelerate the translation of mechanotherapy concepts into clinical practice

Abstract:Hydrogel is an important biomaterial and a hot research topic in biomedical area. However, the micro environment and regulation mechanism of cells and tissue in human body are very complex, there are still some unsolved questions during the application of hydrogel in regeneration and repair area. Along with the development of biomechanics, more and more researchers have found that the biomechanical properties of hydrogel are also one of the key factors in regulating cell function and affecting tissue regeneration and repair, in addition to the material and biological properties. Therefore, we summarized the biomechanical research progress of hydrogel materials, and prospects the future research.

Abstract:Objective To explore the prone site of pressure injuries in buttock in sitting position and the biomechanical response of different soft tissues, so as to provide references for effective prevention of deep tissue pressure injury. Methods Based on CT scan data of the buttock, the finite element model of the buttock in sitting position was established, including the bone, muscle, fat, skin tissues and cushion model. Tissue injury was simulated using life-death elements. The pressure measurement data of the experimental cushion interface were compared with the finite element simulation results to verify validity of the model. The mechanical state of the sitting position was simulated, the stress and strain of soft tissues were studied, and the compressive stress in different soft tissues and the possible damage after exceeding the limit values were analyzed. Results By comparing the simulation results of the cushion model with the experimental interface pressure measurement results, the model was proved to be effective. Stress concentration occurred in soft tissues below the ischial tuberosity in sitting position. The peak transverse compressive stress and peak shear stress in gluteus maximus were 38 kPa and 3. 4 MPa, respectively. The maximum compressive stress and peak shear stress in adipose tissues were 22 kPa and 4. 5 MPa, respectively, which did not appear directly below the ischial tuberosity. Conclusions Deep tissue injury may occur when soft tissues are subjected to a certain magnitude of pressure load within a certain time period. When the sitting position is maintained for a certain period of time, the position

Abstract:Objective To explore the coordination and coordination variability of lower limbs in patients with functional ankle instability (FAI) during level ground walking. Methods Fifteen male subjects with right FAI (FAI group) and 15 healthy male subjects (control group) were recruited to walk on the ground at a self-selected speed. The kinematic data of 5-minute walking were collected using Qualisys infrared high-speed optical motion capture system. The coupling angle and the standard deviation of the coupling angle between the lower limb joints were calculated by using Matlab software to write codes. Circular distribution data were used for coupling angle statistics, and an independent sample t-test was used for the standard deviation of coupling angle. Cohen’s d was used to evaluate the effect size. Results The coupling angle of the hip-knee joint at sagittal plane in FAI group was larger than that in control group in the first half of the middle stance and the last quarter of the swing phase. The coupling angle of the hip-ankle joint at sagittal plane in FAI group was also larger than that in control group before the terminal stance. The coupling angle of the knee-ankle joint at sagittal plane in FAI group was lower than that in control group in the second half of middle stance and the first half of the terminal stance. The coupling angle of the hip-ankle joint at coronal plane in FAI group was smaller than that in control group in the loading response stance and the last quarter of the swing stance. The standard deviations for coupling angles of the hip-ankle joint at coronal and sagittal plane in FAI group were higher than those in control group at the terminal and pre-swing stances. Conclusions The gait pattern of FAI patients differs from that of healthy people. The mode of coordination shows a compensatory protection strategy. The greater coordination variability in the terminal stance and pre-swing suggests that the changes in ankle sensory perception in FAI patients lead to adaptive changes in motor control of the hip, knee, and ankle joints.

Abstract:Objective To explore the correlation between plantar pressure distributions and arch structural features in different standing positions. Methods Plantar pressures of 13 healthy adult males were tested, and foot CT scan and foot bone model reconstruction were then performed to establish arch digital characterization. On this basis, the correlation between plantar pressure measurement indexes and arch characteristics measurement parameters was analyzed. Results Forefoot peak pressure ( FPP) was positively correlated with the medial lateral longitudinal arch height, the medial / lateral longitudinal arch index and body weight, and negatively correlated with the medial / lateral longitudinal arch angle during standing with foot at 0°; it was positively correlated with the medial / lateral longitudinal arch length, the medial longitudinal arch height, the plantar triangle area and body weight during standing with foot at 30°; it was positively correlated with the medial / lateral longitudinal arch height and the medial longitudinal arch index, and negatively correlated with the medial longitudinal arch angle during standing with foot at 60°. Midfoot peak pressure (MPP) was positively correlated with the medial / lateral longitudinal arch length and the plantar triangle area during standing with foot at 0°; it was positively correlated with the medial / lateral longitudinal arch length, the medial / lateral longitudinal arch angle and the plantar triangle area, and negatively correlated with the medial / lateral longitudinal arch index during standing with foot at 30°; it was positively correlated with the medial / lateral longitudinal arch length, the plantar triangle area and body weight during standing with foot at 60°. Rearfoot peak pressure ( RPP) was positively correlated with the medial / lateral longitudinal arch height, the medial / lateral longitudinal arch index and body weight, and negatively correlated with the medial / lateral longitudinal arch angle during standing with foot at 0°; it was only positively correlated with body weight, but not with characteristic parameters of foot arch during standing with foot at 30° and 60°. Conclusions There is a different correlation between plantar pressure distributions and arch characteristics in different standing positions. The results can provide theoretical basis for clinical diagnosis, treatment and prevention of foot pathology caused by different standing positions.

Abstract:Objective To analyze the differences of activity sequence, muscle force performance and muscle activation in lower limb joints between Tai Chi lunge and twist movement, so as to to reveal the characteristics of Tai Chi twist movement. Methods Twenty healthy Tai Chi practitioners who have practiced Tai Chi for more than 3 years were recruited. The kinematic, kinetic and muscle activation of two movements were collected simultaneously using a three-dimensional ( 3D ) motion capture system, force platform and surface electromyography, and the lower limb muscle force was obtained by OpenSim simulation software. Results Compared with lunge movement, there was a significant increase in lateral rotation amplitude of hip and ankle joint in twist movement. The knee abduction and external rotation torque increased significantly. The peak muscle strength of biceps femoris, semitendinosus and medial and lateral gastrocnemius increased, and the time of peak muscle strength of biceps femoris and medial and lateral gastrocnemius was significantly advanced, while the peak muscle strength of vastus medialis, vastus lateralis and tibial anterior muscles decreased, the tibialis anterior muscle strength reached its earliest peak. The average activation levels and activation time of biceps femoris, vastus medialis, vastus lateralis, and medial and lateral gastrocnemius significantly increased. Conclusions Tai Chi twist movement is composed of ankle and hip joint rotation in turn. The uniqueness o fmuscle strength lies in that the center of gravity is shifted twice, which makes muscle strength curve of the vastus medialis and vastus lateralis of the supporting leg to be bimodal. The activation sequence and average activation level of gastrocnemius and quadriceps femoris are changed due to the delay of full foot landing. The results indicate that the full foot landing delay mode has the effect of regulating the sequence of muscle activation, and rational use is helpful to improve the clinical rehabilitation effect

Abstract:Objective Through the simultaneous measurement on gait kinematics and dynamics of older adults with and without a history of falling, the biomechanical characteristics of gait were compared, so as to provide theoretical and practical basis for the prevention of falling in older adults. Methods A total of 284 older adults over 60 years old were recruited in residential communities and apartments for the elderly. According to the inclusion and exclusion criteria, the subjects were divided into falling group ( with a falling history) and non-falling group (without a falling history) according to their falling history in the past 12 months. The kinematics and dynamics parameters of the subjects ' natural walking gait were obtained by three-dimensional ( 3D) video analysis and dynamic plantar pressure measurement. The test data were analyzed by independent sample t-test for the differences of various factors between groups. Results The dynamic parameters of left foot first metatarsal peak force, lateral heel impulse, right toe impulse in falling group were significantly different from those in non-falling group (P<0. 05). The force bearing area of the 2nd metatarsal bone of the right foot, the contact time of the left foot in buffer period, the contact time of the right front foot, the right foot transverse COP (center of pressure) track, the left foot contact hip angle, the displacement of the peak pressure point COM (center of mass) of both feet were significantly different from those of non-falling group (P<0. 05). Conclusions Compared with the older adults without a history of falling, the force area of the 2nd metatarsal bone decreases during walking, the time of foot touching the ground lengthens, the support stability decreases during the transition period, the latera displacement of COP increases, and the displacement of the center of gravity in the direction of walking decreases, indicating that muscle strength of the lower limb of the older adults decreases, the lateral swing of the foot increases, and the walking propulsion decreases, which may lead to compensatory changes in posture control strategy, with the the potential falling risk increasing. In clinical evaluation, the plantar pressure and kinematics characteristics of the gait of the older adults with a history of falling should be focused on.

Abstract:Objective To compare the difference of gait parameter and symmetry between single task walking and double-task walking with different types and different loads in community stroke patients. Methods The gait parameters of 20 community stroke patients in chronic convalescence during single task walking, cognitive double-task walking and motor double-task walking with different loads were collected by Simi Motion threedimensional (3D) motion analysis system, and the symmetry index (SI) was calculated indirectly. The singlefactor repeated measure variance analysis was used to compare gait parameters and symmetry differences between single task walking and walking with different double tasks. Results Compared with single task walking, the walking speed, step length of affected leg side and the swing phase proportion of healthy leg side in community stroke patients during intervention of high-low load cognitive tasks were decreased (P<0. 05), while step width of healthy side and the support phase proportion of healthy side and affected side was increased during intervention of difficult cognitive tasks, stride length of healthy leg side and the swing phase proportion of affected leg side swing was decreased, and the SI of the swing phase proportion decreased (P< 0. 05). Conclusions Community stroke patients mainly deal with cognitive task interference by reducing walking speed, reducing step length, reducing swing phase proportion, increasing step width and support phase proportion, and changing gait patterns. For gait stability, the intervention of high-load cognitive tasks will increase the asymmetry degree of swing proportion of community stroke patients and reduce their gait stability.

Abstract:Objective To evaluate the comfort and safety of footwear for the elderly males wearing experimentally modified shoes during fast walking, so as to provide data references for footwear of the elderly. Methods A total of 16 male subjects aged 55-65 years old were required to wear three different types of sports shoes. The visual analogue scale (VAS) and plantar pressure parameters were used to comprehensively evaluate the sports shoes in terms of subjective comfort and biomechanics. Vertical ground reaction force ( vGRF), center of pressure (COP) displacement and friction coefficient were used to evaluate the safety of sports shoes in terms of attenuation characteristics, gait stability and slip resistance. Results In the 2nd-5th phalangeal region, the average and peak pressures of B shoes were significantly lower than those of A shoes. In the 2nd-4th metatarsal region, the peak pressure of B shoes was lower than that of C shoes. In the 5th metatarsal region, the average and peak pressures of C shoes were significantly lower than those of A shoes and B shoes. In the medial area of foot arch, the average pressure of C shoes was significantly higher than that of A shoes and B shoes. On the outside of the arch area, the average pressure of B shoes was significantly lower than that of C shoes, and the peak pressure was significantly lower than that of A shoes. The 1st peak of vGRF between three pairs of shoes was significantly different. The 2nd peak of vGRF of B shoes was significantly lower than that of C shoes. COPX-LR displacement of C shoes was significantly larger than that of A shoes and B shoes, COPXD displacement of C shoes was significantly larger than that of B shoes. The peak friction coefficient of B shoes during push-off stage of the foot was significantly higher than that of A shoes and C shoes, and the peak time of C shoes at landing stage was significantly slower than that of B shoes. Conclusions B shoes have good safety performance. However, further improvement is needed to reduce plantar pressure in the 5th phalangeal region. In designing footwear for the elderly, if the thick sole design is merely adopted to achieve the effect of shock absorption and cushioning, it may bring negative influences on gait stability of the elderly.

Abstract:Objective To quantify biomechanical characteristics of knee joints for athletes after anterior cruciate ligament reconstruction (ACLR) surgery during side cutting under unanticipated conditions, and to investigate the potential risk of anterior cruciate ligament (ACL) injury in athletes. Methods The infrared motion capture system and three-dimensional (3D) force platform were used to collect the kinematic and kinetic data of lower limbs of 30 male athletes with ACLR during side cutting under anticipated and unanticipated conditions. The angle, moment, ground reaction force (GRF) and other test parameters were analyzed statistically by using two-way ANOVA with repeated measures. Results The knee flexion angle, valgus moment and flexion moment of the affected limb were significantly lower than those of the healthy limb. The internal rotation moment and tibial anterior shear force of the affected limb were significantly higher than those of the healthy limb. Compared with the anticipated conditions, the knee flexion angle, internal rotation moment and tibial anterior shear force significantly increased under unanticipated conditions. The knee external rotation angle of the affected limb was significantly larger than that of the healthy limb under both anticipated and unanticipated conditions. Under unanticipated conditions, the lateral GRF and anterior-posterior GRF of the unaffected limb were significantly lower than those under anticipated conditions, and the lateral GRF of the affected limb was significantly higher than that under anticipated conditions. Conclusions Compared with the healthy limb, the affected limb of athletes with ACLR showed biomechanical characteristics of smaller knee flexion angle, larger knee internal rotation moment and anterior tibial shear force during side cutting, indicating that the affected limb might have a greate potential risk of ACL injury. Under unanticipated conditions, both lower limbs of athletes with ACLR showed biomechanical characteristics of increased knee internal rotation moment, lateral GRF and anterior tibial shear force, indicating that the potential risk of ACL injury is not limited to the affected limb, and ACL injury prevention should also be strengthened in healthy lower limb during side cutting.

Abstract:Objective To quantitatively analyze the in-vivo kinematics of the tibiofemoral joint in patients with arthrofibrosis after anterior cruciate ligament reconstruction ( ACLR) surgery. Methods Fifteen patients with arthrofibrosis after ACLR and 15 healthy subjects were included in the study. The tibiofemoral motion trajectories relative to the femur during weightbearing and non-weightbearing knee flexion of the subjects were collected by using a portable three-dimensional (3D) knee motion analysis system, and kinematic data of the tibiofemoral joint with 6 degrees of freedom (6 DOF) were obtained. Results Compared with healthy subjects, the internal tibiarotation was significantly decreased in patients with arthrofibrosis under 30°, 45°, 60° and 75° weightbearing knee flexion (P<0. 001), and the tibial valgus was significantly decreased in patients with arthrofibrosis under 30° and 45° weightbearing knee flexion (P<0. 05). The internal tibial displacement in patients with arthrofibrosis was significantly smaller than that in healthy subjects under 75° non-weightbearing knee flexion (P<0. 05). Conclusions Knee arthrofibrosis limits the rotation and internal displacement of the tibia, but has little impact on the anterior and posterior displacement of the tibia relative to the femur. Therefore, in clinical practice, various treatments should be used to release the adhesion in the medial and lateral femoral grooves and the contracturof the lateral collateral ligaments, address the limitation in rotation and displacement movement, so as to restore knee function to the fullest extent.

Abstract:Objective To analyze the changes in parameters such as center of pressure area (COPA) and center of pressure speed (COPS) under the influence of visual factors in patients at early stage after anterior cruciate ligament reconstruction (ACLR) and 1 year after the surgery. Methods A total of 17 patients with ACLR were included and tested for data such as COPA and COPS in early postoperative period and 1 year after the surgery, and 17 healthy subjects were matched as control group. The standing balance test with different visual states of open and closed eyes was performed and correlation analysis was conducted for each measurement state. Results During the double-foot standing test, there were significantly difference in COPA and COPS between the eyes-open and eyes-closed states in short-term group (P<0. 05). There were statistically differences in COPS between the eyes-open and eyes-closed states in long-term group (P<0. 001). The difference between the groups was statistically significant during standing on the healthy side (P<0. 05), and the difference between the groups was not statistically significant during standing on the injured side (P<0. 05). During standing on the healthy side with eyes open, COPA was higher in long-term group than that in the short-term and control groups, and COPS was lower in control group than that in short-term and long-term groups (P<0. 01). During standing on the healthy side with eyes closed, COPA was lower in control group than that in short-term and long-term groups, and COPS was lower in control group than that in long-term group (P< 0. 01). Positive correlations in COPA and COPS were found between eyes-open and eyes-closed states during double-foot standing, between injured side and double-foot standing with eyes open, between healthy side and injured side during standing with eyes open, and between healthy side and injured side during standing with eyes closed. Conclusions The analysis on COP-related data for patients with ACLR in standing position indicates that the vision has an important influence on postural stability control. The patients at 1 year after ACLR surgery show greater fluctuation in stability during double-foot and single feet standing compared with normal people. In clinical practice, it is suggested that long-term postoperative training should be strengthened to consolidate the rehabilitation effect, which also has a certain guiding role in carrying out long-term assessments and developing precise training plans, so as to prevent prolonged functional deterioration and reduce the risk of reinjury after surgery.

Abstract:Objective To develop a method for modeling spinal kinematics and dynamics of patients with adolescent idiopathic scoliosis (AIS) and verify its accuracy, so as to provide a tool for analyzing the mechanism and evaluating the effect of non-surgical orthopaedic treatment on scoliosis. Methods The skeletal and muscular parameters of the OpenSim adolescent spinal model developed by Schmid were calculated and adjusted based on imaging data to match the model with specific patients. Based on the literature data, the intervertebral stiffness was added in each vertebral joint, and modified in the scoliosis segments to make the model conform to mechanical characteristics of the vertebral joints in patients with scoliosis, and then a personalized kinematics and dynamics simulation analysis spinal model for patients with scoliosis was established. Inverse kinematics was used based on motion capture data and muscle activation was calculated using static optimization method. The calculated results were compared with imaging and electromyogram (EMG) data. Results The average angle error for the coronal plane of each vertebra was 0. 164°, which met the kinematic error requirements. The ratios of muscle activation rates for convex and concave paraspinal muscles of thoracic and lumbar segments in standing state were 0. 489 and 0. 631, respectively, which were consistent with the EMG data. Muscle activation was closer to EMG data in the modified model for intervertebral stiffness during lateral flexion than that in the unmodified model. Conclusions The model established by the method in this study meets the accuracy requirements of kinematics and muscle force.

Abstract:Objective To establish the finite element model of scoliosis considering trapezius muscle, and explore the effect of trapezius muscle on mechanical properties of the spine. Methods The finite element models of thoracolumbar vertebrae and sacrum were established, and the validity of the models was verified. Scapula and trapezius muscle units were added, and the mechanical influence of trapezius muscle on various parts of the Lenke 1 scoliosis spine under different working conditions was simulated and analyzed. Results The range of motion (ROM) of the spine-muscle model under lateral flexion was 0. 23% less than that of the spine model, and the axial rotation of the intervertebral disc under rotation was reduced by 0. 078° on average. The stress in soft tissues was more evenly distributed on facet joints, and the stress changes in soft tissues were more stable. Under six working conditions, 87. 5% of the lumbar facet joints had reduced stress. Conclusions Trapezius muscle can improve the spine’ s ability to resist deformation, while it also aligns the stress on the spine with gradual distributions. The less stress on lumbar spine, the more external loads human body can bear. The spinemuscle model established in this study is more practical, with certain reference values in clinic practice

Abstract:Objective To explore kinematic characteristics of the spine and pelvis for adolescent idiopathic scoliosis ( AIS) patients with different scoliosis curves during standing and walking, and provide reference suggestions for body training in rehabilitation. Methods The thoracic and lumbar angles, as well as pelvic rotation and pelvic tilt parameters of 45 patients with single curve, 45 patients with double-curve and 27 healthy adolescents were measured in standing position and during walking by using Diers 4D motion module. Results The thoracic angle (40. 67°) and lumbar angle (39. 68°) in healthy group in standing position were the largest, the thoracic enlargement angle (6. 1°) in double-curve group was the largest, and the thoracic enlargement angle (-10. 37°) in healthy group was the smallest. The rotation direction of the pelvis in scoliosis group was the same as that of the main curve, and the direction of the pelvis in single curve group was the same as the main curve. Conclusions Compared with the standing position, the motion trend of the thoracic angle in three groups during walking was mainly reduced, and affected by the scoliosis curve. The lumbar angle decreased in three groups. The three-dimensional (3D) pelvic morphology of scoliosis groups in standing position was affected by compensatory curve of the lumbar, and the dynamic rotation function of the pelvis was related to compensatory curve of the lumbar and initial position of the pelvis during walking. It is suggested that therapists should fully consider the potential impact of scoliosis curves on the results when evaluating and training the patient’ s pelvic function, and provide targeted relaxation and functional training on the side with insufficient pelvic mobility to improve the symmetry of pelvic motor function.

Abstract:Objective To study the effects of different marking line preparation techniques on fatigue properties ofrod and compression fatigue properties of posterior spine internal fixation system. Methods According to YY/ T 0119. 4—2014 standard, four-point flexural fatigue test was performed on the spinal rod. According to YY/ T0857—2011, systematic compression fatigue tests under certain stress were carried out on laser marking line rod and dual-color anodized marking line rod. Results Under 715 MPa stress, the fatigue life of the self-made laser marking line rod and the competitor’s laser marking line rod is reduced by 95% and 98% respectively compared with the unmarked rod, and the fatigue strength of the laser marking line rod decreased by 54% from 742 MPa to 342 MPa, compared with unmarked rod. The fatigue life and strength of the dual-color anodized marking line rod are similar to that of the unmarked rod. The compression fatigue strength of the dual-color anodized marking line rod system was 20% higher than that of the laser marking rod. Conclusions Laser preparation of marking line significantly reduces the fatigue performance of the spinal rod and the compressive fatigue strength of the system. The improved dual-color anodized marking line technology has no effects on the fatigue performance,and can effectively reduce the risk of clinical fracture, providing a reference for the performance improvement and process development of the spinal rod.

Abstract:Objective To compare the effects of different fixation methods on stability of pediatric humeral proximal unstable fractures at different heights by using the finite element method. Methods Different pediatric humeral transverse fracture models at varying heights were created and fixed by elastic stable intramedullary nailing (ESIN) and Kirschner wire with different configurations. These models were imported into ANSYS 2019 to simulate seven working conditions, namely, the upper limb gravity, anterior flexion, posterior extension, adduction, extension, internal rotation and external rotation. The mean maximum displacement of the distal humerus and the mean maximum stress of the internal fixation were analyzed. Results The mean maximum displacement of the distal humerus was lowest in four-pin group at each height, while the average maximum stress on internal fixation was the smallest for ESIN at P1 and P4 heights. For P2 and P3 heights, the four-pin group had the lowest stress levels. Conclusions ESIN is superior to 3-pin fixation in lower fracture planes, while 4-pin Kirschner wires are more effective than ESIN at all heights.

Abstract:Objective To establish a mathematical model for fracture suture load relationship of C1 _1, C2 _1, C3_1 type distal radius fractures fixed by the splint with different pad thicknesses by using static analysis, design of experiment (DOE) and cuckoo-support vector machine prediction. Methods The shape of each tissue in the forearm was obtained from CT images, the corresponding solid models were established, and the modeling was achieved by noise reduction, assembly processes. The mechanical situation of bone tissues under one condition was obtained by applying load to the model according to load data measured by the Workbench. Then through the DOE method, the mechanical conditions of bone tissues under various conditions of the applied load were simulated. Finally, the mathematical models for various fracture types were obtained by cuckoo search-support vector regression (CS-SVR) prediction. Results The load was applied to the fixed position of 12 pressure pads divided by the B surface, and 460 samples were solved in DOE module in Workbench by the DOE method, and 400 of the 460 samples were randomly selected as the training set to obtain the mathematical model. The remaining 60 samples were used as the test set for comparison with prediction result of the mathematical model. The high precision mathematical models for different loads on the fixed position of the splint and the load at fracture suture could be established. The highest prediction accuracy of the model was 99. 659% , and the lowest was 95. 653% . From the accuracy analysis, there was a fuzzy mathematical relationship between the pad load and fracture suture load, indicating that the support vector machine prediction model was effective. Conclusions The study on the effect of pressure splint fixation mode and pressure splint stress on fracture suture is beneficial for the combination of traditional fixation splint and modern science and technology, and it can provide references for the selection of fixators and the design of external fixation devices in clinical treatment of distal radius fractures.

Abstract:Objective To investigate the effects of three different modelling approaches on biomechanical properties of the hip finite element model, and to investigate a more realistic method for assigning material properties to the hip joint. Methods The hip joint model was reconstructed in three dimensions, and the material parameters were assigned using the cortial bone and cancellous bone assignment method, the homogeneous assignment method and the gray value assignment method, respectively. The same boundary conditions and loads were set, the stress on hip joint during standing on one leg was simulated, and the stress and deformation of hip joint in three groups of models were compared. Results The hip stresses were concentrated in the medial femoral neck under three different modelling approaches, and the peak von Mises stresses were 11. 04, 3. 91 and 4. 25 MPa under the cortical bone and cancellous bone assignment method, the homogeneous assignment method and the gray value assignment method, respectively. The maximum deformation in hip model under cortical bone and cancellous assignment was at the upper part of the greater trochanter, with the maximum deformation value of 0. 27 mm at the acetabulum and femoral head. The maximum deformation in hip model under the homogeneous material assignment method and the gray value assignment model was at the acetabulum and femoral head, with the maximum deformation values of 0. 11 mm and 0. 12 mm, respectively. Conclusions The gradient assignment based on gray value of the hip CT data makes material property distributions of the hip model closer to real material properties of the bone.

Abstract:Objective To develop a remote self-mutual-aid functional assessment system based on the knee society score (KSS), and to verify its effectiveness for patients after total knee arthroplasty (TKA). Methods Ten TKA patients were selected, and their functional status was recorded preoperatively, on the day of surgery (0 d), on postoperative 4th and 30th day using the functional assessment system. The system automatically calculated the patient data including KSS score, total range of flexion, flexion contracture, extension lag, knee alignment, pain, and knee stability. Results The results of manual KSS scores by physicians based on experience were compared with the result of KSS scores assessed by the system, and there was no statistically significant difference between the scores, indicating an agreement. Conclusions The KSS scores collected by the remote self-mutual-aid functional assessment system are consistent with the results assessed by clinicians, and the system provides a reliable and convenient method for home assessment and remote rehabilitation guidance for patients after TKA.

Abstract:Objective Based on the design of a novel hip prosthesis stem, the stress distribution differences during standing, walking, running and in sitting posture were analyzed. Methods Based on human CT data,seven groups of hips joint models implanted with different stems were established, and stresses of the prosthetic stem and femur under different working conditions were calculated by using the finite element analysis method.Results Compared with the traditional prosthetic stem, the peak stress of the novel prosthetic stem during standing was reduced by 23% , and the femoral stress was reduced by 72%. The results of seven models showed that the prosthetic stem with the height of 86. 5 mm was the most suitable for patients’ needs. The multi-working condition results showed that when the patient was in sitting posture, the stem had the least stress and a longer service life. Conclusions The novel prosthetic stem helps to prolong the life of the prosthesis and reduce the risk of bone damage. This hip prosthesis model provides scientific theoretical support for post-design of the stem and postoperative rehabilitation of patients.

Abstract:Objective To study the anti-migration mechanical behavior of balloon-expanded aortic valve stent afteimplantation. Methods The mechanical model of anti-migration of balloon-expanded valve stent after interventional treatment of aortic valve was established. The effects of different valve ring ellipticity, friction coefficient, valve stent material and calcification of autogenous valve leaflet on anti-migration of valve stent were studied by numerical simulation method. Results When the ellipticity of aortic valve ring was 0. 2, 0. 3, 0. 4 and 0. 5, the corresponding maximum anti-migration force was 12. 37, 10. 94, 8. 50 and 4. 75 N, respectively. When the friction coefficient was 0. 1, 0. 2 and 0. 3, the maximum anti-migration force of valve stent was 8. 98, 11. 00 and 13. 10 N, respectively. The anchoring performance of valve stent made of L605 cobalt-chromium alloy was better than that made of 316L stainless steel, and its corresponding maximum anti-migration force was 13. 10, 9. 82 N, respectively. When the autogenous valve was calcified, the maximum anti-migration force was 13. 1 N. When the autogenous valve was not calcified, the maximum anti-migration force was only 5. 51 N, decreased by 57. 9% . Conclusions With the increase in ellipticity of aortic valve ring, the anchoring of valve stent decreases gradually. As the friction coefficient between the valve stent and the tissue increases, the maximum anti-migration force also increases. The anchoring performance of valve stent made of L605 cobalt-chromium alloy is superior to that made of 316L stainless steel. The anchoring of valve stent with calcification is better than that without calcification. The results in this study provide an important scientific basis for structural design and clinical selection of anti-migration valve stent.

Abstract:Objective To analyze the adaptability of different materials based on a defined coronary stent design, and to establish an evaluation method for stent design-material selection. Methods Using finite element numerical simulation method, the expansion performance of the stent in blood vessel were analyzed, and the safety and usability of the stent design and materials were investigated for five potential applicable materials. For non-degradable materials, the focus was on the fatigue resistance performance after long-term implantation; while for degradable materials, the changes of support force during degradation were analyzed to clarify the rules of support force provided by the stent. Results For the specific coronary stent design, the simulation showed that for 316L stainless steel and L605 cobalt-chromium alloy stents, the radial recoils were 26% and 19% , the axial foreshortening were 0. 22% and 0. 28% , the maximum equivalent stresses were 551. 2 MPa and 829. 1 MPa, and the fatigue dynamic safety factors were 1. 36 and 1. 67, respectively. For degradable materials AZ31 magnesium alloy, iron and poly (L-lactic acid) (PLLA), the simulated damage time of the stents based on this design was 30h and 180 d, 270 d respectively. Conclusions Based on stent design in this study, the L605 cobalt-chromium alloy exhibited the best expansion performance and fatigue resistance to match the clinical requirements. Compared with the rapid degradation damage of AZ31, the mechanical properties of iron stent and PLLA stent were close but still needed structural optimization. The finite element numerical simulation, especially analysis on expansion performance and fatigue resistance, can effectively simulate mechanical behavior of the stent and provide references for the selections of stent materials and the design optimization.

Abstract:Objective To explore the changes of hemodynamic parameters in septic shock patients before and after volume stress test, and their predictive value to the volume response of patients. Methods A total of 98 septic shock patients were selected for clinical research. According to the stroke volume change ( ΔSV) of patients before and after rehydration treatment, the patients were divided into 53 cases of volume load positive group ( ΔSV≥15% ) and 45 cases of volume load negative group ( ΔSV< 15% ) . The pulseindicated continuous cardiac output ( PICCO ) and echocardiogram related indexes for two groups of patients before and after the volume load test were compared, and the receiver operating curve ( ROC) was used to analyze the value of statistically significant indexes for septic shock to the patient’ s response to the volume load test. A logistics regression model was used to analyze the relationship between various parameters and the volume load test response. Results Before the volume load test, the measured cardiac output ( CO) , cardiac index ( CI) , stroke volume variation ( SVV) , central venous pressure ( CVP) , heart rate ( HR ) values of patients in two groups were compared, and the difference was not statistically significant ( P>0. 05) . After the test, the CO, CI, and CVP values of volume load positive group were all higher than those of volume load negative group ( P<0. 05) , and the HR and SVV values were lower than those of volume load negative group ( P < 0. 05 ) . Before the volume load test, there was no significant difference in measured left ventricular outflow tract inner diameter velocity-time integral ( LVOT VTI) , LVOT peak flow velocity respiratory variability, and VEpeak values of patients between two groups ( P> 0. 05 ) . After the test, the LVOT VTI measurement value of the positive volume load group was higher than that of the negative volume load group ( P< 0. 05) , LVOT peak flow velocity respiratory variability was lower than volume load negative group ( P<0. 05) . ROC curve result showed that for HR, CO, CI, CVP, SVV, LVOT peak flow velocity respiratory variability, LVOT VTI index prediction, the positive area under the curve( AUC) values of the volume load response were 0. 515, 0. 560, 0. 556, 0. 499, 0. 898, 0. 912, 0. 922, respectively. Logistic regression model result showed that the higher the APACHEⅡ score, the higher the SOFA score, the lower the CO, the lower the CI, and the lower the CVP, the higher the SVV, the lower the LVOT VTI, and the greater LVOT peak flow velocity respiratory variability, these were independent risk factors for the negative volume load test in septic shock patients ( P< 0. 05) . Conclusions Closely monitoring the relevant hemodynamic parameters of patients with septic shock has a clinical value for predicting the patient ’ s volume load response, and it can guide patients in clinical fluid resuscitation.

Abstract:Objective To investigate the biomechanical characteristics of lower extremities of competitive taekwondo athletes during double roundhouse kick ( DRK) with the use of electronic body protector ( EBP). Methods Fourteen competitive taekwondo athletes were recruited, and their kinematic, kinetic and surface electromyogram (sEMG) data of lower limb joints during DRK with effective scoring were collected by electronic guard scoring system, sEMG testing equipment, three-dimensional (3D) motion capture equipment and 3D force plate. The motion time, center of gravity ( COG) displacement, range of motion ( ROM) and velocity of lower limb joints, ground reaction force (GRF) and other parameters were calculated by Visual 3D software. Results The total time for two strikes of DRK was 0. 583 s and the attacking period of both dominant and non-dominant sides was the same. The shift of COG was smaller during the kick, and both dominant and non-dominant sides had good balance control ability. The trends of changes in hip, knee, and ankle joint motion angles and angular velocities of the two limb sides were consistent. In knee flexion phase before striking, the deficiency of knee flexion angle of the attacking leg could be achieved by increasing the extension angular velocity in extension phase. In knee flexion and extension phases before striking, the medial head of the lower extremities gastrocnemius muscle generated the most power on two limb sides. Conclusions The DRK technique has good continuity and left-right symmetry, and it can contribute to scoring by reducing the time of attack during the second striking. Athletes should strengthen the ankle joint flexibility, as well as gastrocnemius and gluteus maximus in training process of DRK movement, so as to avoid unnecessary sports injuries and be more adaptable to game mode with the use of EBP.

Abstract:Objective To investigate the effect of different aspect ratios on uniaxial tensile mechanical properties of skin strip specimens from the perspective of experimental methodology. Methods The abdominal skin of New Zealand rabbits was taken as the research object. Strip specimens with aspect ratios ranging from 2 ∶ 1 to 6 ∶ 1 were obtained in the direction from the head to the foot (0°) and in the direction perpendicular to it (90°), and uniaxial tensile tests were performed until the specimens were damaged. After experimental data processing, Kirchhoff stress-Green strain data from uniaxial stretch on the abdominal skin of rabbits were obtained and fitted using a one-dimensional Fung model S= cEexp(αE2), so as to obtain the corresponding material parameters c and α, and statistical analysis of the parameters was performed. Results The differences in c values in two directions were not significant (P = 0. 151), and the differences in α values were relatively large ( P = 0. 001). There was no significant difference in parameters c and α between rabbit abdominal specimens with different aspect ratios in both directions ( P > 0. 05 ). Conclusions Different aspect ratios of rabbit abdominal skin specimens in the range from 2 ∶1 to 6 ∶1 had no effects on their uniaxial tensile mechanical properties.

Abstract:Objective To study the effect of autonomous emergency braking (AEB) on brain injury of pediatric occupants in buses. Methods The bus AEB test scene was developed by using Prescan software. The deceleration curve under the bus AEB condition at initial speed of 60 km / h was obtained by the simulation method. Based on the validated finite element (FE) bus model and the mixed FE model of a 6-year-old child with detailed anatomic head structure, four typical seating positions in the bus were selected, and the head injury of pediatric occupants seated in these positions with and without AEB conditions was simulated with LS-DYNA software. The craniocerebral injury of pediatric occupants was analyzed by using HIC15 of pediatric occupants, pressure at gray matter of the brain, von Mises stress and shear stress of brain tissues as the injury evaluation indicators. Results In simulation test of each group, when the baffle was set in front of Positions 1 and 2, the pressure at gray matter of the brain for pediatric occupants exceeded its injury threshold, while various injury indicators of pediatric occupants at other positions were far smaller than the corresponding injury thresholds. Conclusions The AEB can effectively reduce head impact injury severity of pediatric occupants in buses. The pediatric occupants at Position 3 in the bus are prone to a higher impact head injury risk. The billboard baffle set at Positions 1 and 2 in the bus can increase the head injury risk of pediatric occupants

Abstract:In the nasal cavity, nitric oxide (NO) is involved in many physiological functions, including antibacterial and antiviral activity, promotion of nasal mucociliary clearance, and regulation of blood vessel expansion in the nasal mucosa. The abnormal concentration of NO will lead to the occurrence of various nasal diseases, and NO concentration has become a biological indicator for routine clinical detection of airway inflammation. With the indepth intersection of medicine and mechanics and other fields, the use of numerical research methods, combined with traditional experimental methods, the distribution of NO concentration in nasal cavity can be analyzed, and NO concentration in various parts of nasal cavity can be quantified, so as to obtain the distribution patterns of NO in nasal cavity, assist the clinical diagnosis and treatment of related nasal diseases, and help promote the development of precision medicine. In this review, the progress of experimental and numerical studies on the distribution of NO concentration in nasal cavity was summarized, and the future research direction was prospected.

Abstract:Shoulder arthroplasty surgery is one of the most effective method for treating shoulder joint diseases. In short term, the survival rate of the artificial shoulder joint is high, and the recovery effect of the patient is good, but in long term, the aseptic loosening caused by the wear and tear of the artificial shoulder joint will greatly increase the chance of surgical failure. Due to the complex structure and unclear typical motion of the shoulder joint, the wear test standards for artificial shoulder joints have not yet been published internationally. Therefore, it is necessary to study, analyze and summarize the biomechanical environment of the shoulder joint and establish corresponding motion curves, so as to provide references for the development of artificial shoulder joint wear test scheme and standards. Based on human shoulder joint activity rules, the shoulder joint activity ability can be divided into basic or physical activity of daily living ( BADL or PADL) and instrumental activity of daily living (IADL) by using the activities of daily living (ADL) scale. In this study, shoulder joint motion curves for several specific motion rules were established. The results lay foundation for the establishment of wear test scheme and standard of artificial shoulder joint.

Abstract:Nonspecific chronic low back pain ( NSCLBP) is a common disease that has generated widespread attention, yet its pathogenesis remains unclear. In recent years, more and more attention has been paid to biomechanical mechanism of the occurrence and development of NSCLBP aided by relevant equipment. This review focused on core function of lumbar spine, i. e. flexion and extension movements, and summarized the progress on biomechanical characteristics of NSCLBP during lumbar flexion and extension both domestically and internationally. Through an in-depth discussion and summary of specific research methods and observationindexes, anomalous signs of kinematics, kinetics, surface electromyography were found in patients with NSCLBP, which opened up new ideas for exploring pathogenesis of NSCLBP and its scientific prevention and treatment.

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