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Abstract:Sports biomechanics is an interdisciplinary application science that studies human movement. The main purpose of sports biomechanical research is to improve competitive sports performance and prevent sports injuries. This review introduced methods commonly used in biomechanical research, and selected results in biomechanical research on sports performance, training method and sports equipment, so as to provide references for improving the quality of biomechanical research in China. It is hoped that more biomechanical studies will be conducted with the focus on sports performance improvement and injury prevention, using rigorous research design and new technologies to obtain more accurate biomechanical data in human movement, so as to increase the breadth and depth of sports biomechanical researches.

Abstract:Under the background of technological assistance to prepare for the Beijing Winter Olympics in China, the biomechanical research highlights and the latest achievements related to competitive performance of alpine skiers in recent years were systematically analyzed in this paper, so as to determine biomechanical factors affecting competitive performance of alpine skiers, including aerodynamic drag, frictional forces, ground reaction force (GRF), energy dissipation, turn radius, trajectory of the skis and/or center of mass (COM). In addition, biomechanical differences in turn techniques, multiple turns connections and abilities of individuals were also considered as important factors affecting the alpine skiing performance. In the case of slalom and giant slalom events, the earlier initiation of turns, longer path length and trajectory, earlier and smoother application of GRF, and carbene technique carving to reduce the ski-snow friction and thereby dissipate energy should be used to improve sports performance. During speed skiing, minimizing the exposed frontal area and positioning the arms close to the body can reduce the energy loss caused by aerodynamic drag, thereby improving sports performance. Top-level alpine skiers will always perform well on different courses, terrains and snow conditions during the race. Excellent alpine ski performance from a biomechanical perspective includes the efficient use of potential energy, minimizing ski-snow friction and aerodynamic drag, choosing optimal trajectory and maintaining high-speed skiing. Individual tactics and techniques should be valued in training and competition. For better results, the same performance on multiple sections and on different terrains is more important than excellence in individual sections and specific conditions.

Abstract:Objective To explore characteristics of flow field around the athletes, change of net flow force, and influences of hip flexion angles at the end of extension kick on the submerged dolphin kick stroke. Methods The body shape data of a swimmer were obtained by three-dimensional (3D) scanning, and the data were reversely reconstructed to obtain the swimmer model. The joints of the swimmer model were separated, and each segment of the athlete was divided into independent rigid body, and simulation of the submerged dolphin kick stroke was realized by controlling movement of each independent rigid body. The computational fluid dynamics (CFD) software package ANSYS Fluent was used as the solver for calculation and solution. Results The vortex structures were shed off from the surface of the swimmer’s body in the area with a large velocity gradient in flow field, and the shedding of vortex structures was different at the stage of extension kick and flexion kick. Propulsion was mainly generated during extension kick phase. At the end of extension kick, the drag decreased as the hip flexion angle increased from 20° to 30°. Conclusions To some extent, increasing flexion angle of the hip joint at the end of extension kick will reduce the drag force and increase the swimming speed in process of the submerged dolphin kick stroke.

Abstract:Objective To extract key parameters from a series of biomechanical parameters of rowing technique, so as to provide useful information for coach training. Methods Based on rowing performance of 16 rowers in national team, the factor analysis was used to extract reducing dimension of biomechanical parameters of rowing technique of 80 oxygen utilisation 2 （UT2） training pieces. Results The biomechanical parameters of rowing techniques were classified as technical characteristic factors (angle of 70% peak force, work portion of per 25% stroke length, drive start time, finish slip, position of peak force and angle of peak force), power factor (rower power, average of boat power, port swivel power and stroke swivel power), stroke length factor (catch angle and finish angle) and oar’s motion factor (recovery time, stroke rate and distance of per stroke). Conclusions Monitoring and analyzing these biomechanical factors would contribute coaches and scientific researchers to accurately judge the technical characteristics and shortcomings of rowers.

Abstract:Objective To investigate the effect from circumferential distribution angle of forwards wedge vortex generators on aerodynamic drag reduction during flow around a cylinder, so as to provide theoretical evidences for low drag sprint garment design. Methods Forwards wedge vortex generators were reconstructed based on the NIKE’s AeroBalde. Given that the individual parts of an athlete body can be treated as multiple cylinders with varied dimensions and positions, 48 forwards wedge vortex generators were distributed as four columns on windward side of the cylinder, which were symmetrical with the YOZ plane. When the air flowed through the cylinder at the speed of 32 km/h, large eddy simulation was carried out on the computational domains which were properly meshed with polyhedral mesh to investigate the drag force, flow filed and pressure distributions. Results It was effective for drag reduction of the cylinder induced by airflow when two columns of forwards wedge vortex generators were circumferential distributed in the range of 55°-75°and the circumferential internal angle between two columns was in the range of 10° or 15°. The pressure distribution on leeward side of the cylinder was apparently changed after surface modification, which minimized the pressure drag dominant in aerodynamic drag. The drag reduction mechanism was that micro-vortices were generated downstream after flow through the forwards wedge vortex generators, which resulted in an early transition to critical flow with low drag force. Conclusions Effective aerodynamic drag reduction is achieved if forwards wedge vortex generators are properly distributed. The research findings can provide guidance for wind tunnel test and low drag sprint garment design.

Abstract:Objective To compare rotational techniques used by Chinese and world elite men’s shot put athletes, so as to provide scientific references for Chinese male shot putters to improve their sports performance and results in international competitions. Methods Three-dimensional (3D) kinematics data from Chinese male shot putters in actual competitions were obtained, and kinematic parameters of Chinese and world elite men’s shot put athletes were calculated and compared. Namely, shot velocities and hip-shoulder separation angles at five critical instants of rotational techniques: right foot off, left foot off, right foot touchdown, left foot touchdown and release, as well as phase durations and shot travel distances during four critical phases: first single support, air-born flight, second single support and final delivery. ResultsCompared with world elite athletes, Chinese male shot putters using rotational techniques had significantly lower vertical release velocity, longer air-borne duration, smaller hip-shoulder separation angles at left foot off and touchdown instant, and longer shot travel distance during air-borne flight, but shorter shot travel distance during final shot delivery. Conclusions The difference in lower extremity strength is a primary casue leading to different sports performance between Chinese and world elite male shot putters. The technique differences in Chinese and world elite male shot putters mainly lie in different phase timing and shot travel distances during different techinique phases.

Abstract:Objective To make analysis and diagnosis on backhand twist technique used by player A, who is the leading men’s player of national table tennis team, so as to provide references for improving his backhand twist technique. Methods The three-dimensional kinematics test and analysis were used. The backhand twist techniques of player A and those of player B who has good backhand twist techniques were compared by quantitative data and picture analysis. Results At the stage of swinging racket backward, the racket swing amplitude, shoulder angle and wrist angle of player A were significantly smaller than those of player B. The roll angle of trunk of player A was significantly larger than that of player B. At the stage of swinging and hitting the ball, the shoulder angle, elbow angle of player A were significantly bigger than those of player B, while the increasing amplitude of shoulder angle and elbow angle, as well as the changing amplitude in roll angle of trunk of Lin Guoyuan were significantly smaller than those of player B. At the stage of swinging racket forward, the shoulder angle and elbow angle of player A were significantly bigger than those of player B. The increasing amplitude of shoulder angle and elbow angle, as well as the roll angle of trunk and its changing amplitude of player A were significantly smaller than those of player B. Conclusions The racket swing amplitude of player A was smaller, and the distance between the racket and the ball of player A was close at the end of swinging racket backward stage. During swinging and hitting the ball stage, the hitting point was far from the body, the shoulder joint was not stable enough to support, so that the wrist was used more. The center of gravity was not enough to force forward, and the outburst power was not concentrated. At swinging racket forward stage, player A’s braking was not active enough, which affected the stability of hitting the ball. At hitting the ball stage, the torsion of the trunk was smaller, and the waist power was not concentrated. On the basis of unaffecting the forehand outburst power, player A should slightly adjust his backhand twisting technique, or appropriately increase the the racket swing amplitude and torsion of the body. In the process of hitting the ball, the sequence of outburst power was the waist, the forearm and the wrist.

Abstract:Objective To determine the effects of javelin release parameters related to aerodynamics on aerodynamic distance and results in javelin throwing in actual competition environments. MethodsKinematic data from javelin throwing of 22 Chinese and American elite women javelin throwers were obtained using three-dimensional videographic method. The trial with the longest aerodynamic distance and the trial with the shortest aerodynamic distance for each thrower in the same competition were included in this study. Aerodynamics-related techinical parameters in long and short aerodynamic distance trials were compared. Results Compared with short aerodynamicdistance trials, the vacuum flight distances of long aerodynamic distance trials were significantly shorter, but the official distances were significantly longer. The release velocities of long aerodynamic distance trials were significantly lower, the attack angles and bending angles were significantly smaller. The horizontal direction angles at release of the long aerodynamic distance trials were more to the right side. The elevation angles and horizontal pointing angles during right/left foot landing in long aerodynamic distance trials were not significantly different from those in short aerodynamic distance trials. Conclusions Throwing javelin with submaximal effort beneficiates the control of aerodynamics-related release parameters and thus increased chances to obtain long aerodynamic distance and better result in women javelin throwing. Reducing attack angle and releasing javelin about 5°to the right will assist women javelin throwers to obtain longer aerodynamic distance.

Abstract:Objective By making biomechanical analysis of double poling (DP) technique on uphill terrain used by Chinese male cross-country (XC) skiers, to characterize biomechanical differences in DP for skiers at different levels, and determine the influence from motion techniques of skiers on their sports performance. Methods Twenty-four male XC skiers who participated in the 15 km classical race at the Beishan ski resort in Jilin, China, on Sept. 11-12, 2019 were selected in this study. On the basis of their race performance, they were divided into faster skiing group (n=12) and slower skiing group (n=12). The kinematic variables of the skiers were obtained by three-dimensional (3D) shooting, and the differences in cycle characteristics, action phases and key technique variables for skiers in two groups were analyzed. Results Faster skiers had a faster DP velocity. There was a positive correlation between swing distance and velocity. The swing distance was positively correlated with average angular velocity of elbow extension in poling phase, average angular velocity of shoulder extension in swing phase, and range of motion (ROM) of shoulder abduction. The swing distance was negatively correlated with extension of the elbow in poling phase. All the above variables showed statistical differences between faster and slower skiers. Conclusions For a long distance competition, the difference in DP velocity on uphill terrain was mainly casued by the difference in swing distance, which originated from the swing phase. Faster skier had a longer swing distance. The differences in the swing distance came mainly from the shoulder and elbow joints. Therefore, slower XC skiers in China should strengthen muscle strength of the upper limbs, especially the shoulder and elbow joint strength. More forward body leaning and larger hip and knee flexion angle at pole plant might help the skier to cover more distance.

Abstract:Objective To study the influence of skull thickness on intracranial biomechanical parameters by finite element method. Methods The female head at 5th percentile was selected for CT scanning to construct finite element model of the head with high biofidelity,and the model was verified by reconstructed cadaver test. The finite element model of the head with different skull thickness was established, and multiple groups of tests were carried out to compare the intracranial mechanical parameters. Results The negative value of intracranial pressure was significantly affected by the decrease in skull thickness under the same head size, while the negative value of intracranial pressure was slightly affected, with an increasing trend. The shear stress and von Mises stress of brain tissues were significantly increased with skull thickness increasing. Conclusions Under the same head size, the skull thickness will affect head injury to a certain extent, and people with small skull thickness are more likely to be injured than those with large skull thickness.

Abstract:Objective To study the accuracy of traditional basilar membrane displacement evaluation criteria for evaluating hearing compensation performance of round window-stimulated middle ear implant, so as to provide the theoretical basis for performance evaluation of round window-stimulated middle ear implant. Methods An acoustic microscopic finite element model of cochlea was constructed based on experimental data of the cochlea geometry. Reliability of this model was verified by comparison with experimental measurement values of inner hair cell, outer hair cell, tectorial membrane displacement. Based on this model, the displacement of basilar membrane and the stereocilia shear displacement of inner hair cells under forward stimulation and round-window stimulation were comparatively analyzed. Using the stereocilia shear displacement of inner hair cells as the criterion for sense of sound, the equivalent sound pressure level (SPL) deviation under round-window stimulation was studied when using traditional basilar membrane displacement as evaluation criterion. Results At 5 kHz characteristic frequency of the studied slice of cochlea, under sound pressures with the same amplitude, the displacement of basilar membrane and the stereocilia shear displacement of inner hair cells under round-window stimulation were lower than that under forward stimulation. Conclusions Under forward stimulation, the inner hair cells were more excited and the performance for sense of sound was better than that under round-window stimulation. Concurrently, using the displacement of basilar membrane under forward stimulation as the criterion of hearing compensation performance would overestimate hearing compensation performance of middle ear implant under round-window stimulation; but the deviation was relatively small, which was a relatively reliable evaluation method.

Abstract:Objective To analyze and compare pore characteristics and mechanical properties of models with solid and sheet triply periodic minimal surface (TPMS) structures, and build a porous structure with high specific surface area, low stiffness and high strength. Methods The solid TPMS and sheet TPMS models of D, G, and P units with the same porosity were established, and pore characteristics of the model such as pore diameter, rod diameter and specific surface area were compared; mechanical properties of the model were analyzed by finite element method. The porous titanium samples were made by additive manufacturing technology, pore characteristics of porous titanium were observed by microscope and scanning electron microscope, and mechanical properties of porous titanium were detected by compression test. Results The specific surface area of the sheet structure with the same unit was significantly higher than that of the solid structure; mechanical properties of the sheet structure with the same were significantly better than those of the solid structure. Among them, the D unit sheet TPMS model had the most significant advantages, with the specific surface area of 13.00 mm-1, and the elastic modulus, yield strength and compressive strength of the sheet porous titanium sample were (5.65±0.08) GPa, (181.03±1.30) MPa and (239.83±0.45) MPa, respectively, which were 43.87%, 55.08% and 67.21% higher than those of the solid porous titanium sample. Conclusions While retaining low rigidity of the porous structure, the sheet TPMS model of the same unit has a larger specific surface area, which is beneficial for cell adhesion and growth, and its low stiffness and high strength mechanical properties can effectively reduce stress shielding and provide sufficient mechanical support. It is an ideal pore structure model for bone defect repair substitutes.

Abstract:Objective To study the effect of different materials and porosities on bone formation in the scaffold after implantation of the degradable bone scaffold into human body. Methods According to natural reaction mechanism of fracture healing, the finite element method was used, combined with geometry of the scaffold, to establish a computationally coupled model based on material degradation curve and bone reconstruction control equation. Through this platform, representative volume elements of the scaffold with five kinds of materials and four types of porosities were selected for calculation and analysis, and dynamic process was reflected by bone mineral density (BMD) and maximum stress of the scaffold. Results The elastic modulus of the materials had a greater influence on growth of bone tissues in the scaffold. The smaller elastic modulus of the materials would lead to the greater amount of bone formation, but it would also have a greater impact on mechanical properties of the scaffold. The scaffold with higher porosity had lower rigidity, which could better promote formation of bone tissues, meanwhile it would also destroy mechanical stability of the scaffold. Conclusions According to performance requirements for different age, gender and location of bone tissues, personalized reference and calculation basis for selection of materials and porosity, structural design and clinical application of degradable porous bone scaffolds can be provided.

Abstract:Objective To simulate the process of thrombus removal from the open-type stent retrievers, so as to provide theoretical references for the design and clinical application of the open-type stent retrievers. Methods Finite element models of the open-type stent retrievers with 3,4,5 supporting units (K3,K4,K5), the crimping tools, simulated vessels and simulated thrombus (three types) were established. Radial displacement load was applied on the crimping tool until the stent was crimped to 0.5 mm, and the maximum principal strain (MPS) peak and radial force (RF)of the stent were analyzed. When displacement of the crimping tool was restored, the stent self-expanded and contacted with blood vessels, and MPS of the stent and von Mises stress (VMS) of blood vessels were analyzed. Axial displacement was applied to proximal end of the stents to allow the stent to drive the clots to migrate, and the blood vessel VMS and withdrawal force of the stents (the ability to capture thrombus) were analyzed. ResultsThe MPS peaks for 3 types of stent retrievers during crimping process were 6.94%, 8.30% and 5.48%, which were all smaller than the 12% fracture limit. When the outer diameter of the stent was 3 mm (equal to the inner diameter of blood vessels), the K4 stent had the largest RF. The results of self-expanding release process showed that the larger the number of support units, the greater the VMS of blood vessels. At the stage of thrombus migration and removal,the VMS of blood vessels was generally small and concentrated on the thrombus. The withdrawal force of the stent reached the maximum at the initial stage of thrombus migration and removal, then gradually decreased. The peak withdrawal force of the K4 stent was larger than that of the K5 and K3 stent. Conclusions Although the MPS and VMS for 3 types of open-type stent retrievers were within the safe range, the K4 stent showed better performance in RF and withdrawal force with the three types of thrombus. The research findings can provide the analysis methods and ideas for optimizing the open-type stent retrievers, to avoid clinical complications such as vascular injury and improve safety and effectiveness of the stent retrievers.

Abstract:Objective To establish a blast injury experimental model using a shock tube at lateral lying position of C57BL/6 mice, investigate biomechanical responses of macrophages/microglia cells in the heart, lung and brain tissues to mechanical damage by shock wave within 24 hours. Methods Shock tube was employed to generate a shock wave to C57BL/6 mice. Firstly, the weight changes of mice were measured at different time points after the shock. Then the cardiac, pulmonary and whole brain tissue samples were dissected after anesthesia. Pathological sections were stained with HE staining to detect structural damage; the TUNEL staining method was used to mark and count the proportion of dead cells in each tissue. Microglial cells were labeled with fluorescent antibody, while responses and changes of macrophages/microglia after shock loading were analyzed. Results The shock tube exerted 179 kPa overpressure shock wave upon sideway of the mouse, and lethal rate of the mouse was 3.33%. Compared with normal control group, the mice in experimental group had a significant weight loss within 24 hours after loading shock. Pathological sections showed rupture of lung tissues after shock, accompanied by alveolar protein deposition, pulmonary bulla and other diseases. Fluorescence staining showed that lung tissue was recruited and activated in a large amount within 24 hours. The proportion of dead cells cleared rebounded to normal level within 24 hours. The heart was highly tolerant to shock, and macrophages appeared near the large blood vessels. The brain showed unilateral aggregation of microglia due to the impact posture, mainly due to prolonged inflammation and a higher proportion of dead cells at the junction of gray and white matter. Conclusions A blast shock model at lateral lying position of the mouse was established. Within 24 hours, macrophages/microglia were recruited quickly to the injury site after being impacted, which mediated strong immune stress, and might participate in the immune response to trigger a second long-term inflammatory injury. The results of the study provide experimental basis for the evaluation of primary impact injury, such as dose-effect relationship and tissue damage difference.

Abstract:Objective To study the influence of cell-extracellular matrix (ECM) adhesion on migration of tumor cells regulated by ECM stiffness. Methods The cellular Potts model (CPM) was established to simulate tumor cell growth and cellular immune feedback system. The effects from mechanical behavior of cells on cell-ECM adhesion were observed, and the migration of tumor cells under different ECM was analyzed. Results The ECM stiffness could influence the migration rate of tumor cells. The change of ECM stiffness regulated the adhesion force between cells and ECM, and the change of adhesion force would influence the migration rate of cells. Conclusions The migration and distribution patterns of cells are closely related to the adhesion and stiffness of ECM. The increase in ECM stiffness can effectively promote the migration rate of tumor cells, and the further increase in ECM stiffness inhibits the migration of tumor cells. These findings may further reveal dynamic changes of ECM, adhesion and mechanical performance of tumor cell migration.

Abstract:Objective To investigate the effect of incremental load training on AMP-activated protein kinase (AMPK) phosphorylation in skeletal muscle satellite cells of aged mice. Methods Experimental mice were divided into 3 groups: young control group (YC group, n=12), old control group (OC group, n=12) and old training group (OT group, n=12). The mice in OT group received incremental load training, and CD45-/CD31-/Sca1-/VCAM (CD106) + cells were isolated by flow cytometry sorting. Desmin, Myod myogenic staining and myogenic differentiation culture were used for identification of muscle satellite cells, and the p-AMPK level of muscle satellite cells was detected by immunohistochemistry combined with Western blotting method. Results The expression levels of AMPK and p-AMPK in skeletal muscle satellite cells in YC group were significantly higher than those in OC group (P<0.05). AMPK expression in OT group and OC group did not change significantly (P>0.05), while p-AMPK expression level in OT group was significant higher than that in OC group (P<0.05). Conclusions Incremental load training can promote AMPK phosphorylation of skeletal muscle satellite cells in aged mice, and improve energy metabolism of skeletal muscle in aged mice.

Abstract:Objective To establish the three-dimensional (3D) finite element model of unicompartmental knee arthroplasty (UKA) with 3° and 7° posterior tibial slope at different knee flexion angles, and to study biomechanical properties and prosthetic wear of the knee joints with two types of posterior tibia slope and their effects on knee function. Methods Combining CT and MRI images of human knee joints with the 3rd-generation Oxford prosthesis, the finite element UKA model with 3° and 7° posterior tibia slope were established. The 1 kN load was applied to center point of the medial and lateral condyles of the femur to simulate the standing load of human body. The maximum stresses and distributions of the prosthesis and articular cartilage at different knee flexion angles were analyzed. ResultsThe maximum stress of the meniscus liner with 3° posterior tibia slope at 0°, 30°, 60°, 90°, 120° knee flexion angles increased by 28.06%, 68.99%, 19.45%, 21.06% and 53.38%, the distribution area was concentrated from the side of the meniscus liner to the central area, and the stress concentration was obvious at 120° knee flexion. The maximum stress of prosthesis with 3° posterior tibia slope was greater than that with 7 ° posterior tibia slope. The expansion of stress concentration area would cause wear and loosening of the prosthesis, contact stress and concentration area of the articular cartilage would subsequently increase with posterior tibia slope increasing, and stress concentration would be more obvious at high knee flexion angles. Conclusions Tibial prosthesis has the higher stress and greater wear under the condition of 3° posterior tibia slope than 7° posterior tibia slope. The research findings provide theoretical basis for the UKA design in clinic.

Abstract:Objective To analyze plantar pressure features of patients in injured and healthy sides of the lower limbs under different walking conditions after the trimalleolar fracture surgery, and compare these characteristics with healthy subjects. Methods Twelve Trimalleolar fracture patients and twenty-three healthy subjects were recruited and their plantar pressure characteristics under different walking conditions were tested, including peak pressure, contact area and contact time percentage. Results Comparison between injured and healthy sides: during level walking, peak pressure of the 3rd-5th toe in the injured feet were smaller than those in the healthy sides; in inversion position, peak pressure and contact area of the 3rd-5th toe area in the injured feet were smaller than those in the healthy side; in eversion position, peak pressure, contact area and contact time of the 3rd-5th toe in the injured feet were smaller than those in the healthy sides, and peak pressures of the hindfoot area were larger than those in the healthy sides. Comparison between patients and healthy subjects: under three kinds of walking conditions, peak pressures of the 2nd and 3rd metatarsus bones, the 2nd toe, the 3rd-5th toe, contact area of the 1st-5th toe and contact time percentage of the 2nd toe, the 3rd-5th toe area were all smaller than those of healthy subjects, while contact time of the hindfoot and mid-foot area were all smaller than those of healthy subjects. Conclusions The plantar pressure characteristics of Trimalleolar fracture patients were asymmetrical. Compared with healthy subjects, the plantar pressure features of patients were abnormal during stance phase. Compared with healthy subjects, the motor control ability and stability of patients in eversion positions were decreased. The plantar pressure characteristics at ankle eversion can be used to evaluate ankle joint function.

Abstract:Objective To investigate the effect of medial unicompartmental knee arthroplasty (UKA) surgery on knee biomechanics during stair ascent. Methods Nine osteoarthritis patients who received fixed-bearing medial UKA participated in this study. All patients completed pre-surgical (3 weeks before UKA surgery) and post-surgical ［(7±2) months after UKA surgery］ test. Their synchronized biplane radiographs during stair ascent were collected. Motion of the femur, tibia, and implants were tracked using an automated volumetric model-based tracking process that matched subject-specific 3D models of the bones and prostheses to the biplane radiographs with sub-millimeter accuracy. Anatomic coordinate systems were created within the femur and tibia and used to calculate tibiofemoral kinematics. Additional outcome measures included the center of contact in the medial and lateral compartments, and the lateral compartment dynamic joint space. Results The UKA knee was in 4.8° varus compared with the pre-surgical contralateral knee. The post-surgical UKA knee was in 3.1°valgus compared with the pre-surgical knee. The post-surgical UKA knee was 4.4° externally rotated compared with the pre-surgical contralateral knee. However, the medial tibia contact center of the UKA knee moved posteriorly 2.5 mm compared with that of the contralateral knee (P<0.05). No obvious changes were found in lateral compartment joint space before and after surgery (P>0.05). Conclusions UKA can effectively improve varus of the knee joint and restore biomechanical characteristics of UKA knee rotation, without affecting lateral compartment joint space. However, changes are found in contact center of the medial tibia compartment of the UKA knee after surgery.

Abstract:Objective By comparing the physical properties (cell area, volume and elastic modulus) of red blood cells (RBCs) between newborn infants and the elderly over 80 years old, and correlation with the physiological and biochemical parameters such as total cholesterol and glycosylated hemoglobin, the effects of different ages and biochemical parameters on RBC physical properties were analyzed. Methods The mcropipette aspiration was used to measure the surface area, volume and elastic modulus of erythrocytes in newborn infants and the elderly over 80 years old, and the data were analyzed by statistical distribution analysis, correlation analysis and regression analysis. Results The mean values of RBC volume, surface area and elastic modulus in the elderly over 80 years old were smaller than those in newborn infants, and the mean values of RBC mechanical parameters in the same age group were not significantly different. The erythrocytes geometric parameter distribution of newborn infants was more concentrated than that of the elderly, while the elastic modulus distribution of newborn infants was more dispersed than that of the elderly. The mechanical properties of RBCs in newborn infants were highly correlated with the total cholesterol and gestational week; the mechanical properties of RBCs in the elderly were highly correlated with diastolic blood pressure and glycated hemoglobin. Conclusions There are significant differences in physical properties of RBCs between newborn infants and the elderly over 80 years old, and the biochemical parameters that affect physical properties of RBCs at different ages are also different.

Abstract:Objective To evaluate the damage of von Willebrand factor (vWF) induced by shear stress in BPX-80 centrifugal blood pump, and determine whether it can be used as a reference pump for vWF damage research. Methods An in vitro hemolysis test platform was established according to the ASTM standards. The BPX-80 centrifugal blood pump was tested for 8 hours by using fresh porcine blood. The hemolysis level and vWF damage of hourly blood samples were then evaluated and compared with the static control group. ResultsThe hemolysis index of BPX-80 was stable and low during the test; vWF polymer with high molecular weight had a small amount of degradation, and showed no significant difference compared with the static control group; there was no significant change in the concentration of vWF antigen, which was basically consistent with the trend of the static control group. Conclusions BPX-80 centrifugal blood pump has good blood compatibility and can be used as the reference pump for vWF damage and hemolysis evaluation, thereby providing guidance for the design and optimization of new blood pumps.

Abstract:The important function of the endplate is to transmit stress and supply nutrition. Endplate degeneration might induce or promote degeneration of the intervertebral disc, causing a series of spine diseases that seriously impair people’s health and life quality. Endplate chondrocytes can respond to mechanical stimulation, which is an important factor affecting endplate degeneration. Inappropriate mechanical stimulation will accelerate endplate degeneration. This review summarized the effects of mechanical stimulation on vertebral endplate chondrocyte apoptosis, synthesis inhibition, calcification, and extracellular matrix degradation. The endplate degeneration induced by mechanical stimulation is regulated by a complex network of signal pathways composed of various signal transduction factors. The signal pathways involved in this review included NF-κB, Wnt, Hedgehog, MAPK, RhoA/Rock-1, AKT/mTOR, TGF-β signaling pathway and miRNA related signals. The interconnection of these pathways was highlighted and summarized. Multiple signaling pathways work together to regulate endplate chondrocyte metabolism, which ultimately leads to the endplate degeneration. This review might shed light on early diagnosis and precise treatment of cartilage endplate degeneration.

Abstract:In the process of tumor growth, with the proliferation and expansion of cancer cells, the reconstruction of extracellular matrix (ECM) of cancer tissues, the restriction of surrounding tissues and the flow of cancer tissue interstitial fluid, the special stress environment is formed in the tumor tissues. Significant differences are found in the mechanical environment and mechanical characteristics of different regions of tumor tissues, that is, mechanical heterogeneity. The reseach shows that the mechanical properties of tumor tissue invasion frontier areas are more significant and complex. In particular, the epithelial-mesenchymal transition (EMT) of tumor cells also prefers to concentrate on this area. The mechanical stress generated by the invasion front can induce EMT of tumor cells through TWIST1, TGF-β, WNT and other force signal transduction pathways, and promote tumor cell invasion. From the perspective of tumor biomechanics, this review focuses on the relationship between mechanical heterogeneity of tumor cells and EMT, so as to provide the theoretical basis for mechanoenvironment-targeted therapy of tumors.

Abstract:Patellar tracking disorder is recognized as one of the major causes of the pathophysiological mechanism in patellofemoral pain syndrome. This paper reviewed the results of patellofemoral kinematic analyses and summarized the motion characteristics of six-degrees-of-freedom (6DOF) of patellofemoral joints under different functional activities. Patella has a relatively unified trend in lateral, anterior and posterior translation, tilt and flexion. However, different measurements limit an in-depth comparison between studies. In the future, widely applying magnetic resonance(MRI) or/and dual fluoroscopic imaging system (DFIS), standardizing the establishment of coordinate system or definition and use of morphological parameters, and increasing sample size will contribute to explicating the 6DOF motion characteristics of patellofemroal joints in vivo and improve the clinical evaluation on kinematic function of patellofemroal joints.