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Abstract:The cardiovascular system plays a crucial role in the entire organism. It performs many important functions, such as providing organs and tissues with nutrients, hormones, delivering oxygen to cells, and maintaining physiological temperature. For a long time, accurately identifying the nonlinear and anisotropic mechanical properties of the vascular wall within the body has been regarded as a key challenge in cardiovascular biomechanics, as these properties are critical determinants of overall cardiac function. Currently, the roles of mechanical and tissue properties in cardiovascular diseases such as arterial aneurysms and atherosclerosis remain hot topics in both basic and clinical researches. This review aims to summarize the latest research advances in the field of cardiovascular biomechanics and mechanobiology in the year 2022. In terms of cardiovascular biomechanics, researchers focus on the structure, function, and pathophysiology of the cardiovascular system, and use experimental methods such as mechanical modeling to study these issues. These include studies about biomechanical properties of diseases such as atherosclerosis, arterial aneurysms, and myocardial infarction, as well as the development and testing of treatment methods based on dynamics of the cardiovascular system. In terms of mechanobiology, researchers explore mechanical properties of cardiovascular cells and extracellular matrix, including prediction of cell mechanical properties based on machine learning, studies of biological material mechanical properties, and the role of mechanical properties in cardiovascular cell phenotype changes. These research findings provide new ideas and methods for diagnosing and treating cardiovascular diseases and offer new insights into researches in biomechanics and mechanobiology fields.

Abstract:In view of fundamental challenges to the current life and medical researches, this paper analyzes the mechano-chemical coupling behaviors of living organisms at molecular, sub-cellular, cellular and tissue levels, attempting to explain the quantitative relationships in those mechano-chemical coupling behaviors at different scales. These quantitative relationships show that the structures of living organisms at various scales are closely related to their tensional homeostasis, i. e. , the structural changes will inevitably lead to the changes of tensional homeostasis; Conversely, the changes of the tensional homeostasis will inevitably lead to structural changes. The tensional homeostasis in living organisms stems from contractile force in actin cytoskeleton generated by the action of myosin II at molecular level, and the tensional homeostasis at higher structural levels is realized with the help of hierarchical structures of the living organisms. Therefore, the mechano-chemical coupling mechanisms and their corresponding quantitative relationships inspire scientists to develop a new way of understanding and dealing with diseases, called as mechanomedicine. Finally, the paper discusses possible ways / road maps of mechanomedicine to understand and treat diseases, in order to provide diagnostic and therapeutic ideas for this new medical paradigm.

Abstract:Dendritic cells (DCs) are now known as the most powerful antigen-presenting cells in vivo, with efficient antigen uptaking, and processing capabilities. They can present antigens to na?ve T cells in secondary lymphoid tissues, thereby induce immune response or tolerance, and play a key role in initiating and amplifying innate and adaptive immunity. DCs experience complex chemical and mechanical microenvironment changes and show different mechanophenotypes and immunophenotypes in the process of exerting their physiological functions. Deeply understanding the chemical and mechanical factors that regulate the mechanophenotypes and immunophenotypes of DCs is a prerequisite for using DCs to treat immune related diseases. In this review, the progress in the biomechanics and mechanobiology research of DCs was mainly introduced, and their potential applications and future development directions in the treatment of immune related diseases were explored.

Abstract:Objective To investigated the effect of stenosis characteristics (vascular elasticity and plaque properties) on myocardial ischemia. Methods An ideal geometric multi-scale coronary stenosis model based on fluid-structure interaction was established, and the fractional flow reserve (FFR) was simulated to evaluate myocardial ischemia. The effects of vascular elastic wall (elastic modulus of 1 MPa) and rigid wall, plaque types (lipid-rich plaque and calcified plaque) and plaque volume on myocardial ischemia were considered separately. Results The FFRCT simulation result of vessels with elastic wall was larger than that with rigid wall under all stenosis situations. The FFRCT of vessels in lipid-rich lesions was higher than that of calcified plaque (P=0.001). The trapezoidal plaque volume was larger than the cosine plaque volume, and the FFRCT of vessels in trapezoidal plaque was smaller than that of cosine plaque (P=0.001). Conclusions Vascular elasticity is a critical factor to simulate vascular hemodynamics. In moderate stenosis, calcified plaques are more likely to induce myocardial ischemia due to the larger luminal deformation and dilation of rich lipid plaque. When the stenosis is constant, the smaller the plaque volume, the higher the FFRCT and the smaller the possibility of myocardial ischemia.

Abstract:Objective To study the process of single stent and double-stent thrombectomy at the Y-shaped bifurcation of the ideal internal carotid artery by finite element simulation, analyze the stent-thrombus-vessel interaction during the thrombectomy process based on the simulation results, and provide guidance for improving the effect of stent thrombectomy at the bifurcation. Methods The CAD software was used to build the model and the finite element analysis software was used to simulate the process of single stent and double-stent thrombectomy. Results Thrombectomy was unsuccessful in single stent model and successful in double-stent model, and the maximum stress of thrombus during embolus retrieval was twice that of single stent, the maximum strain was 1.12 times that of single stent, and the maximum contact pressure on the surface of vessel was approximately twice that of single stent. Conclusions Double Solitaire stents can effectively prevent thrombus displacement at the bifurcation and successfully retrieve the thrombus, but there is a risk of fracture due to the high stress level in the middle section of the thrombus. The contact pressure of the vessel on the anterior artery side is higher during thrombectomy, and the risk of vessel damage is greater. Therefore, it is necessary to optimize the design of the stent-retriever to improve its flexibility.

Abstract:Objective To study the effects of aneurysmal neck angle on stent displacement after endovascular repair of abdominal aortic aneurysm (AAA). Methods The CT images of 28 patients were selected to establish preoperative AAA model, postoperative AAA model and covered stent model respectively, and the models were divided into non-severe angulation group ( n = 14) and severe angulation group ( n = 14) according to the preoperative angle of tumor neck. The geometric shape of each model was measured, and the changes of AAA geometric parameters and postoperative stent displacements before and after surgery were analyzed. The displacement force of the model during the first follow-up was calculated by hemodynamic simulation. Results Significant differences were found in tumor length, maximum diameter, displacement force, tumor neck length and tumor volume between two groups of patients (P<0. 05), while there was no significant difference between COG (the center of gravity) displacement and proximal displacement (P> 0. 05). For the incidence of internal leakage, there were 2 cases in non-severe angulation group and 4 cases in severe angulation group (P>0. 05).Conclusions Severe neck angulation can lead to a significant increase in support displacement force and decrease in proximal anchorage zone, and thus increase the possibility of support displacement. It is suggested that doctors should strengthen postoperative follow-up for patients with severe neck angulation and be vigilant of the occurrence of long-term internal leakage in clinic.

Abstract:Objective Based on interface damage, a numerical simulation method for in-plane propagation of false lumen (FL) was proposed to explore the regular pattern of in-plane propagation of the initial cavity. Methods Three interface damage modes were characterized by bi-linear traction separation law, and the damage parameters were calibrated by simulating peeling and shearing tests. The damage interface was introduced into the ideal double-layer cylindrical tube aortic model by means of cohesive zone model (CZM) to simulate the in-plane propagation of FL. The control variable method was used to establish several computational models to investigate the influence of cavity geometric parameters on propagation direction, critical pressure and interface damage mode. Results The interface damage was mainly opening mode (Mode I) in axial propagation and sliding mode (Mode II) in circumferential propagation. With radial depth of the initial cavity increasing, the propagation of the FL changed from circumferential direction to axial direction, the critical pressure decreased, and the axial damage tended to be pure opening mode. With circumferential angle and axial length of the initial cavity increasing, the critical pressure decreased and the circumferential damage tended to be pure sliding mode. The critical pressure of single damage was lower than that of mixed damage. Conclusions The CZM can effectively characterize interface damage behavior of elastic lamellae within the media, and it applies to numerical simulation of in-plane propagation of the FL. The results of this study is helpful to understand the complex pathophysiological process of dissection crack propagation.

Abstract:Objective To explore influences of the taper and connecting rib form on supporting performance of the stent, and provide an important scientific basis for structural design and clinical selection of the tapered stent. Methods A nonlinear finite element model for radial support performance of a novel balloon-expandable tapered stent was constructed, and the radial stiffness (RS) and stress distributions of the stent at different tapers (0°, 0.565°and 1.13°) and with different structural forms of stent linker (V-shape, I-shape, C-shape, S-shape, M-shape) were analyzed by plane compression. The relationship between structural design of the vascular stent and its radial support performance was studied. Results The RS of 0°stent, 0.565°stent, 1.13° stent was 2.51, 1.61, 0.85 N/mm, respectively. The RS of 0.565°stent and 1.13° stent was 35.86% and 66.14% lower than that of 0°stent (round straight stent), respectively. Except that the RS of C-shape linker stent was 1.48 N/mm, the RS of I, M, S and V-shape linker stents was not significantly different, which was 2.51, 2.61, 2.41, 2.52 N/mm, respectively, indicating that radial compression resistance of these four linker stents was almost the same. Conclusions Compared with traditional round straight stents, the RS of tapered stents will decrease, and the RS of stents will gradually decrease with the the taper increasing. Among all stent types in this study, except C-shape linker stents, the RS of other linker shapes has little effect on the RS of stents. The radial support performance of the stent can be improved by reducing the taper of the tapered stent, without changing the form of stent connecting ribs.

Abstract:Objective To investigate the effects of banding width on hemodynamic characteristics of pulmonary artery (PA) by constructing pulmonary artery banding (PAB) models with different widths. Methods Based on clinical practice, with the same banding position and degree, computer-aided design (CAD) was utilized to reconstruct three-dimensional PAB models with different banding widths (2, 3, 4, 5 mm). Hemodynamic characteristics of the models with different banding widths, including pressure, streamlines, energy loss, energy efficiency and blood flow distribution ratio, were compared and analyzed through computational fluid dynamics (CFD). Results The pressure of PA decreased significantly, while the change of banding width had no significant effects on the pressure drop level at banding position. With the increase of banding width, the energy loss decreased, and the energy efficiency showed an upward trend. The blood flow of the left PA raised, and the ratio of blood flow distribution between the left PA and right PA increased, with the maximum reaching up to 2.28 : 1. Conclusions The increase of banding width can reduce the energy loss of PA and improve the energy efficiency of blood flow, but it will lead to the imbalance of blood flow distributions between the left and right lungs. Both the balance of blood flow distribution and the energy loss should be considered in choice for banding width of PAB. The virtual design of PAB surgery based on CAD and CFD will assist individualized banding width selection in future.

Abstract:Objective To investigates the applicability of cutting balloon in the pretreatment of superficial coronary artery calcified lesions, so as to decrease the occurrence of serious consequences in the treatment of calcified lesions. Methods The effect of cutting balloon on calcified plaques with different curvatures, thickness, and length was analyzed using the finite element method, with normal balloon as a control. The thickness of calcified plaque was set to 0.3 mm and 0.4 mm, and the length was set to 2 mm and 4 mm. The calcification degree was set to 120°, 180°, 270°and 360° according to the intravenous ultrasound (IVUS) calcification severity grading, with a total of 16 types of calcified plaques. The brittle fracture module was used to simulate calcification fracture of calcified plaques, and virtual stent implantation was carried out based on pretreatment simulation. The effect of pretreatment was evaluated by calcification fracture condition and stent roundness. Results For superficial calcification lesions, in lesions less than 120°, the balloon could not remove the calcification plaque obstruction, and the stent roundness rate was 82.75%. In 180° calcified lesions with thickness of less than 0.3 mm, the calcification was broken by cutting balloon under 1 215.9 kPa expansion pressure, and the post-stent roundness rate was 74.42%; normal balloon could not cause calcification fracture under safe expansion pressure (1 418.55 kPa). In 270°calcified lesions with thickness less than 0.3 mm, the normal balloon produced 3 fractures under 1 013.25 kPa expansion pressure. The cutting balloon produced 2 fractures under 1 013.25 kPa expansion pressure, and the balloon could not fracture the circular calcified lesions with thickness of 0.3 mm. Conclusions Cutting balloon is recommended for 180°calcified lesions with thickness less than 0.3 mm, the normal balloon is recommended for 270°calcified lesions, and balloon pretreatment is not recommended for annular lesions with thickness greater than 0.3 mm.

Abstract:Objective To investigate effects of human postures on flow characteristics of iliac vein compression syndrome. Methods The numerical model of iliac vein was reconstructed from CT images of a typical patient with pelvic-type iliac vein compression syndrome with collateral veins. Based on the computational fluid dynamics method, the non-Newtonian model and the porous media model were adopted to describe effects of abnormal structures on blood flow and acquire the wall shear stress and pressure of iliac vein. The discrete phase model was used to study the residence conditions of erythrocytes under three human postures. Results The pressure gradient at two ends of the compressive region was lowest under lying state, while the iliac vein showed a high pressure under sitting and walking states. The local maximum wall shear stresses under three postures were found at narrow segment of the collateral vein and convergence region of two flows of right iliac vein. The maximum shear stress was largest under lying state and smallest under sitting state. The blood residence time of 52.2 s in the left iliac vein was the longest under sitting state. The residence time of 14.8 s was shortest under lying state. The blood residence time was 23.8 s under walking state. Conclusions Porous media model used to simulate the effect of abnormal structures was highly consistent with the angiography data. The venous hypertension under sitting and walking states was consistent with the clinical results, and the lying state could relieve the hypertensive condition. In terms of wall shear stress and blood residence time in iliac vein, the continual change between three human postures would cause endothelial damage and blood flow stasis alternately, thus increase the risk of thrombosis.

Abstract:Objective To study changes in bone microstructure of osteoporotic rats by multiscale analysis. Methods A total of 20 5-month-old female SD rats were randomly divided into two groups, i.e., ovariectomy (OVX) group (n=12) and the SHAM group (n=8), respectively. The rats in OVX group were subjected to bilateral ovariectomy and became osteoporosis models after 8 weeks, while sham operation was performed for the SHAM group. Changes in microstructure of cortical bone and cancellous bone at tissue scale, and osteocyte lacunar-canalicular network (LCN) and extracellular matrix (ECM) at cell scale were quantitatively analyzed using Micro-CT and SR-Nano-CT. Results At tissue scale, the cross-sectional area of cortical bone in OVX group was significantly higher than that in SHAM group (P<0.05), and the bone mineral density (BMD) and thickness of cortical bone were not significantly different from those in SHAM group. The trabecular BMD, bone volume fraction, trabecular thickness and trabecular number in OVX group were significantly decreased in comparison with SHAM group (P<0.01), while the trabecular separation was significantly increased (P<0.01). At cell scale, there was no significant difference in the semiaxes of lacunae between OVX group and SHAM group, but the thickness of lacunae and the diameter of canaliculi in OVX group were significantly increased in comparison with SHAM group (P<0.05). At the same time, the porosity of cortical bone in OVX group was significantly higher than that in SHAM group at cell scale (P<0.05). Conclusions The bone microstructure in OVX group varied to different extents at tissue and cell scales. At tissue scale, the cancellous bone loss was severe, while the cortical bone had fewer changes. At cell scale, porosity of the lacunar-canalicular network significantly increased, which directly affected the BMD and strength of cortical bone. Multiscale analysis on changes in bone microstructure of OP rats has potential application value for clinical diagnosis and pathological analysis of osteoporosis.

Abstract:Objective To investigate the difference of matrix stiffness in different regions of tibial plateau in osteoarthritis (OA) and its effects on morphology of the cartilage and mitochondria. Methods The tibial plateau cartilage specimens of OA were obtained for nanoindentation test, transmission electron microscopy and histological analysis. The stiffness of cartilage matrix in different regions of OA tibial plateau was detected by nano-indentation. The morphology of cartilage mitochondria in different regions was observed by transmission electron microscopy, and the changes of mitochondrial plane area, shape and ridge volume density were quantitatively analyzed. Cartilage injury in different regions of OA tibial plateau was observed by histological staining. Results The cartilage of OA tibial plateau showed regional heterogeneity, and the cartilage and mitochondria on medial side of varus knee OA were more severe, and the matrix stiffness was higher. The OA scores were positively correlated with matrix stiffness. There was also a significant correlation between OA scores and mitochondrial morphology: the higher OA scores, the larger and rounder mitochondrial plane area, and the lower cristae volume density. Conclusions The differences of tibial plateau revealed the correlation between cartilage matrix stiffness, OA scores and mitochondrial morphological parameters. The increased cartilage matrix stiffness may be the main cause of chondrocyte mitochondrial injury, and further aggravate the progression of OA.

Abstract:Objective To improve the performance of artificial joint at biological fixed interface by frettingmechanical stimulation. Methods Taking the bonding sample of active rat bone tissues and inactive titanium bead coating as the research object, by using the self-developed fretting mechanical stimulation test device, the effects of mechanical stimulation with different tangential fretting amplitudes on growth promotion and micro-injury of bone tissues at fixed interface were explored, and the mechanism of growth promotion and micro-injury of bone tissues on the surface of titanium bead coating under fretting stimulation was revealed. Results The mechanical stimulation group with 40 μm fretting amplitude showed the maximum interface bonding force between bone tissues and titanium bead coating. The tangential fraction force-displacement curves changed from elliptic shape to linear shape, and the bonding interface was in adhesion area, which was difficult to become loose. The bone tissues had the most complete structure, and the number of tissue cells adhering and growing on the surface of titanium bead coating was the largest, as well as the distribution range was the widest. With the increase of fretting amplitude, the promoting effect of fretting stimulation on bone growth weakened, the bonding strength between bone tissues and titanium bead coating interface gradually decreased, the internal cavity area increased, the number and proliferation activity of tissue cells decreased to varying degrees as well. Conclusions Fretting stimulation with different amplitudes can promote the growth of bone tissue and cause micro-injury at the same time, and the optimal fretting amplitude is 40 μm.

Abstract:Objective To study the short-term variation patterns of graft viscosity after anterior cruciate ligament reconstruction (ACLR) surgery. Methods Six male New Zealand rabbits were selected. The ACLR animal model of unilateral knee was made with Achilles tendon as the graft. The experimental rabbits were euthanized 15 days after ACLR surgery, with removal of the graft, healthy anterior cruciate ligament (ACL) and Achilles tendon. The cross-sectional area and viscosity coefficient of the graft were measured, and the creep experiments were carried out under equilibrium conditions of 0.1 MPa and 1 MPa, respectively. The viscosity coefficent was calculated. Variation patterns of graft viscosity were summarize. The grafts were compared with healthy ACL. Results The cross-sectional area of the graft increased slowly within 15 days after ACLR surgery. The viscosity of ACL and graft changed nonlinearly. The viscosity coefficient was quite different under different stresses. The viscosity coefficient of the graft decreased with the time after ACLR surgery, which was more obviously under the condition of low stress. Conclusions The results are helpful to guide the implementation of early postoperative rehabilitation plan after ACLR surgery .

Abstract:Objective To study the short-term variation patterns of graft viscosity after anterior cruciate ligament reconstruction (ACLR) surgery. Methods Six male New Zealand rabbits were selected. The ACLR animal model of unilateral knee was made with Achilles tendon as the graft. The experimental rabbits were euthanized 15 days after ACLR surgery, with removal of the graft, healthy anterior cruciate ligament (ACL) and Achilles tendon. The cross-sectional area and viscosity coefficient of the graft were measured, and the creep experiments were carried out under equilibrium conditions of 0.1 MPa and 1 MPa, respectively. The viscosity coefficent was calculated. Variation patterns of graft viscosity were summarize. The grafts were compared with healthy ACL. Results The cross-sectional area of the graft increased slowly within 15 days after ACLR surgery. The viscosity of ACL and graft changed nonlinearly. The viscosity coefficient was quite different under different stresses. The viscosity coefficient of the graft decreased with the time after ACLR surgery, which was more obviously under the condition of low stress. Conclusions The results are helpful to guide the implementation of early postoperative rehabilitation plan after ACLR surgery .

Abstract:Objective To explore the effect of mucle force on contact force, peak pressure and contact area of foot joint in in vitro biomechanical experiment of foot and ankle, so as to provide references for choosing appropriate loading modes. Methods In neutral position of the ankle joint, fresh calf and foot specimens were simulated with or without mucle force loading. The contact force, peak pressure and contact area of the 1st metatarsophalangeal joint, the 2nd metatarsophalangeal joint, the 1st tarsometatarsal joint, the 2nd tarsometatarsal joint, the medial cuneonavicular joint, the intermediate cuneonavicular joint, the talonavicular joint, the calcicocuboid joint, the subtalar joint ( posterior articular surface) and the tibiotalar joint of normal foot under loading were measured, the results are compared and analyzed. Results Under muscle force loading, the contact force of the 1st metatarsophalangeal joint, the 2nd metatarsophalangeal joint, the 1st tarsometatarsal joint,the 2nd tarsometatarsal joint, the medial cuneonavicular joint, the intermediate cuneonavicular joint, the talonavicular joint and the tibiotalar joint were significantly greater than those without muscle force loading (P<0. 05), and the change percentages were 719. 28% , 311. 37% , 128. 67% , 50. 82% , 54. 89% , 57. 63% ,79. 98% and 50. 34% , respectively. The peak pressures of the 1st metatarsophalangeal joint , the 1st tarsometatarsal joint and the talonavicular joint under muscle force loading were significantly higher than those without muscle force loading ( P < 0. 05), and the change percentages were 176. 14% , 62. 91% and 40. 07% ,respectively. The contact area of the 1st metatarsophalangeal joint, the 1st tarsometatarsal joint, the intermediate cuneonavicular joint and the subtalar joint ( posterior articular surface) under muscle force loading increased significantly (P<0. 05), and the change percentages were 132. 20% , 55. 41% , 30. 97% and 26. 87% , respectively. Conclusions In biomechanical experiment of foot and ankle specimens, muscle force loading has a significant effect on contact force, peak pressure and contact area of each foot joint, especially the forefoot.Therefore, it is necessary to consider the effect of muscle force loading on stress of foot and ankle in the study ofrelated in vitro specimens

Abstract:Objective By comparing the fatigue strength of type A and type B locking compression plates (LCP) in distal femoral plate, a theoretical evaluation method was provided for type selection of bone plate when testing its bending strength and fatigue performance. Methods Through bending strength performance test and fatigue performance test on bone plates with different types, combined with ANSYS Workbench, the finite element analysis on total deformation, von Mises stress and fatigue service life of bone plates were conducted. Results The fatigue strength of type A plate was 30.7% higher than that of type B plate, the stress of type A plate was lower than that of type B plate, and the minimum fatigue service life of type A plate was 17% higher than that of type B plate. Conclusions The fatigue performance of type A plate is better than that of type B plate, so the failure possibility of type A plate was lower than that of type B plate.The results provide references for assisting selection of different bone plates when testing the performance of two newly developed bone plates.

Abstract:Objective To compare the differences in kinematic parameters and plantar pressures for two types of knee varus with tibial and femoral origins in gait analysis, so as to provide biomechanical theoretical basis for different types of genu varus. Methods Twenty-six patients with unilateral knee osteoarthritis (KOA) varus genu were enrolled, with 13 from femoral and 13 from tibial sources. Using Noraxon MyoMotion three-dimensional (3D) motion capture system and Footscan plantar pressure test system, the gait of the subjects during natural walking was measured, the temporal and spatial parameters of the gait, the kinematics parameters of lower limb joints and plantar pressures were collected, to make comparative analysis between the two groups. Results The range of knee flexion and extension of tibial varus, the peak of hip abduction, the range of motion (ROM) of hip adduction and abduction and the peak of ankle pronation were larger than those of femoral lateral genu varus. The peak of knee flexion and hip adduction was smaller than that of femoral lateral genu varus. Compared with femoral varus, subjects with tibial varus had increased stress time and peak pressure on the plantar of the 4th and 5th metatarsals (P＜0.05). In the 3rd metatarsal region, the impulse of healthy femoral limb was greater than that of healthy limb with tibial deformity. While in the medial calcaneal region, the impulse of healthy femoral limb was smaller (P＜0.05). Conclusions There are some differences in kinematic parameters and plantar pressures between two different types of unilateral genu varus patients. The results of this study are helpful to understand the abnormal gait caused by genu varus, and provide reliable reference for postoperative rehabilitation and limb exercise for different types of genu varus.

Abstract:Objective A practical and highly accurate algorithm for dynamic monitoring of plantar pressure was proposed, the magnitude of vertical ground reaction force (vGRF) during walking was measured by a capacitive insole sensor, and reliability of the prediction accuracy was verified. Methods Four healthy male subjects were require to wear capacitive insole sensors, and their fast walking and slow walking data were collected by Kistler three-dimensional (3D) force platform. The data collected by the capacitive insole sensors were pixelated, and then the processed data were fed into a residual neural network, ResNet18, to obtain high-precision vGRF. Results Compared with analysis of the data collected from Kister force platform, the normalized root mean square error (NRMSE) for fast walking and slow walking were 8.40% and 6.54%, respectively, and the Pearman correlation coefficient was larger than 0.96. Conclusions This study provides a novel algorithm for dynamic measurement of GRF in mobile scenarios, which can be used for estimation of complete GRF outside the laboratory without being constrained by the number and location of force plates. Potential application areas include gait analysis and efficient capture of pathological gaits.

Abstract:Objective An X-shaped cushioning insole with variable stiffness was designed to explore its effects on plantar pressure and internal stress of diabetic patients with toe amputation. Methods Based on CT images, the feet-calf finite element model of diabetic patients with toe amputation was established, and the insole was divided into different areas according to distribution characteristics of the planter pressure. The three-dimensional (3D) printed cushioning insole with an X-shaped sandwich structure was designed. The modulus of the sandwich structure was changed by changing thickness of the sandwich structure panel. For simulation analysis, the divided area was filled with the X-shaped sandwich structure with different modulus. Results The peak plantar pressure of diabetic patients with toe amputation was in calcaneal region, and the combined insoles with 1. 2 mpanel thickness in toe area, 1. 4 mm panel thickness in metatarsal area, 2. 0 mm panel thickness in middle area and 1. 6 mm panel thickness in heel area had the best decompression effect. Compared with bare feet, the peak pressure in heel area of the insole, the peak pressure in phalangeal head area and the stress in plantar softissues were reduced by 40. 18% , 31. 7% , and 50. 44% , respectively. Conclusions The 3D printed insoles with variable stiffness can effectively reduce surface pressure and internal stress of the sole and reduce probability of the 2nd toe amputation

Abstract:Objective To analyze the influence of different backpack types and loads on kinematics and plantar pressure of college students during stair climbing, so as to provide references for choosing the appropriate backpack and carrying mode. Methods The Nokov infrared light point motion capture system and Podome plantar pressure system were used to analyze the differences in the range of motion ( ROM) of the trunk and lower limb joints, the kinematic parameters at the peak time, the peak pressure of each plantar partition, the contact time, the maximum pressure of the whole foot, the average pressure and the maximum contact area for 15 male college students during the support period of stair climbing. Results The 5% BW and 10% BW backpack loads reduced ROM of trunk rotation, increased ROM of ankle flexion/ extension and varus / valgus. The 10% BW backpack loads increased the peak pressure of the 1st and 3rd metatarsals bones and the maximum pressure of the whole foot ( P < 0. 05). Single-shoulder bag and handbag reduced ROM of trunk tilting and rotation, and increased ROM of ankle flexion and extension, hip flexion angle, peak pressure of foot arch and medial heel (P<0. 05). The double-shoulder bag loads increased peak pressure in the toe area (P<0. 05). Conclusions During walking on the stairs, the 5% BW and 10% BW backpack loads limited trunk rotation and increased ankle ROM. The 10% BW loads also increased the load in metatarsal area. The unilateral weight-bearing mode would make the trunk tilt to the unload side and rotate to the weight-bearing side. The pressure in toe area was higher when carrying double-shoulder bag, while single-shoulder bag and handbag mainly increased the pressure of arch foot and medial heel. It is suggested that college students choose symmetrical backpack scheme, and wisely allocate back weight to avoid the injury of foot area.

Abstract:国家自然科学基金项目(11932012、81400536),上海申康医院发展中心临床创新三年行动计划(SHDC2020CR3009A),上海交通大学 医工(理)交叉基金(JYJC202130)

Abstract:Objective To study the biomechanical effect of jumping distance on dental implants with socket-shield technique (SST), so as to provide references for clinical standards of jump distance. Methods Based on clinical characteristics, four groups of three-dimensional (3D) SST implant system models with 0, 0. 5, 1 and 1. 5 mm jumping distance were established, and the corresponding material parameters were assigned. The peak stress and stress distributions on models were simulated under specific occlusal condition. Results When the jumping distance was non-zero, namely, the implant was not in contact with the retained root fragment, the stress of the implant and abutment increased with the increase of jumping distance, and the peak stress in root fragment and periodontal membrane decreased with the increase of jumping distance. When the jumping distance was zero, the peak stress of the implant, abutment, root fragment and periodontal membrane reached the maximum, far exceeding that of the other groups. Conclusions The jumping distance has a significant effect on the SST implant system. It is recommended to take a larger jumping distance in clinical practices. The edge of the root fragment should be rounded, and the size of the lower edge should not be too small.

Abstract:Objective Aiming at improving biomechanical strength of the anastomotic stoma as well as reducing tissue thermal damage, a novel radiofrequency (RF) tissue welding electrode was developed. Methods A novel electrode with a hollow structure on the surface ( the plum electrode) was designed and the ring electrode was used as control group to conduct the welding of intestinal tissues based on RF energy. Biomechanical properties of anastomotic stoma were studied by shear test and burst pressure test. The tissue thermal damage during welding was investigated by finite element electro-thermal-mechanical multi-field coupling simulation analysis and thermocouple probe, and the tissue microstructures were also studied. Results Under 120 W RF energy, 8 s welding duration and 20 kPa compression pressure, the anastomotic stoma had the optimal biomechanical properties. Compared with the ring electrode group, biomechanical strength of the anastomotic stoma in plum electrode group was higher, with the shear strength and burst pressure increasing from (9. 7±1. 47) N, (84. 0±5. 99) mmHg to (11. 1±1. 71) N, (89. 4±6. 60) mmHg, respectively. There was a significant reduction in tissue thermal damage, and intact and fully fused stomas could be formed in anastomotic area. Conclusions The proposed novel electrode could improve biomechanical strength of the anastomosis as well as reduce tissue hermal damage, thus achieve better fusion. The research result provide references for realizing the seamless connection of human lumen tissues

Abstract:Objective To observe the inhibitory effect of Tirofiban on different shear-induced platelet aggregation, and to provide medication suggestions for the treatment of thrombosis in different hemodynamic environment. Methods Polydimethylsiloxane ( PDMS)-glass microchannel chips were fabricated by soft lithography. The whole blood of healthy volunteers anticoagulated with sodium citrate was collected and incubated with different concentrations of Tirofiban in vitro. The blood flowed through the straight microchannel or channel with 80% narrow for 150 seconds at the speed of 11 μL/ min and 52 μL/ min, respectively. The wall shear stress rates in straight channel at 11 μL/ min and 52 μL/ min were 300 s-1 and 1 500 s-1, respectively. The maximum wall shear rates in the channel with 80% occlusion at 11 μL/ min and 52 μL/ min were 1 600 s-1 and 7 500 s-1, respectively. The adhesion and aggregation images of fluorescent labeled platelets on glass surface were photographed with the microscope, and the fluorescent images were analyzed with Image J. The platelet surface coverage ratio was used as a quantitative index of platelet aggregation behavior, and the IC50 of Tirofiban for platelet inhibition was calculated under different shear rates. Flow cytometry was used to detect the platelet activation index (CD62P, PAC-1) in the whole blood at 52 μL/ min in channel with 80% occlusion. Results Tirofiban inhibited platelet aggregation in a dose-dependent manner, and the inhibitory effect was related to the shear rate. Under the shear rates of 11 μL/ min and 52 μL/ min, the aggregation was almost completely inhibited when the concentration in straight channel reached 100 nmol / L. When the concentration in channels with 80% occlusion reached 1 μmol / L, the aggregation was almost completely inhibited. IC50 values at 11 μL/ min and 52 μL/ min in straight channel were 2. 3 nmol / L and 0. 5 nmol / L, respectively. IC50 values at 11 μL/ min and 52 μL/ min in channels with 80% occlusion were 20. 73 nmol / L and 4. 5 nmol / L. Pathologically high shearforce induced an increase in platelet activation, which could be inhibited by Tirofiban. Conclusions Tirofiban can effectively inhibit shear-induced platelet aggregation, and different concentrations of Tirofiban should be given according to the thrombus formed in different shear force environment in clinic practice

Abstract:Carotid is in a high risk of atherosclerosis due to its special geometric features and complex flow characteristics. Various biomechanical parameters are practical tools for carotid risk assessment. It has beenwidely accepted that oscillatory low shear environment promotes plaque formation. Based on this, more and more biomechanical indexes have been proposed, such as time-average wall shear stress, oscillatory shear index, relative residence time and so on. In this paper, multiple biomechanical parameters were introduced from the perspectives of shear stress and its temporal and spatial variation, turbulence, platelet transport and activation, stress concentration in vascular wall, etc. The development trend of biomechanical parameters related to carotid artery risk assessment was also analyzed, so as to provide the theoretical basis for more comprehensive and rapid carotid risk assessment

Abstract:Osteoporosis is characterized by decreased bone strength and increased fracture risk. The most serious consequence of osteoporosis is fracture, which commonly occurs in vertebrae. Accurate assessment of fracture risk at an earlier stage is the key to identify high-risk population and further prevent osteoporotic fracture. Currently, clinical assessment of vertebral fracture risk mainly relies on measurement of bone mineral density (BMD) based on dual energy X-ray absorptiometry ( DXA) or quantitative computed tomography ( QCT). However, they cannot fully reflect bone strength and resistance to fracture, and it is hard to achieve an accurate assessment. Biomechanical CT (BCT) technology, based on CT digital modeling and finite element analysis, aims at non-invasive calculation of individual bone strength, bridging the gap between biomechanics and clinical evaluation of fracture risk. In vitro mechanical experiment of vertebrae has proved that BCT is more accurate than BMD in evaluating vertebral fracture strength. Clinical studies have also shown that BCT is superior to DXA in identifying existing fractures and predicting new fractures. In this article, the implementation process of the BCT technology was introduced, as well as critical parameters during each step affecting its result . The research progress of the BCT technique for in vitro validation and in vivo assessment of vertebral fracture risk was also summarized, with the aim to promote the application of BCT technology in clinical assessment of vertebral fracture risk for the Chinese people.

Abstract:Long-term exposure to risk factors will lead to coronary atherosclerosis, which will lead to the formation and progression of coronary plaque. Early identification of high-risk plaque characteristics will help prevent plaque rupture or erosion, thus avoiding the occurrence of acute cardiovascular events. Biomechanical stress plays an important role in progression and rupture of atherosclerotic plaques. In recent years, non-invasive coronary computed tomography angiography (CCTA) computational fluid dynamics (CFD) modeling has made it possible to acquire the corresponding biomechanical stress parameters. These coronary biomechanical stress parameters, especially wall shear stress (WSS), will aid in the development of a more accurate clinical model for predicting plaque progression and major adverse cardiovascular events ( MACE ). In this review, the biomechanical stress and the role of WSS from CCTA in atherosclerosis were introduced, and the researches on the relationship between biomechanical stress from CCTA and coronary artery diseases were discussed.