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Abstract:Sports biomechanics is a multidisciplinary applied discipline that studies the mechanics of human movement and plays a crucial role in scientific research and technological support in competitive sports. This paper reviews the research methods in competitive sports biomechanics and focuses on research progress in the year 2023 in three key areas: improving sports performance, preventing sports injuries, and developing sports equipment. The goal is to provide new insights to further advance the application of sports biomechanics in competitive sports.

Abstract:This review systematically polled the latest advancements in biomechanics research in competitive swimming during the Paris Olympic period together. By analyzing the application of biomechanics in competitive swimming, it reveals the key factors in performance improvement and injury prevention, mainly encompassing technique analysis and optimization, research methods and equipment, performance evaluation and enhancement, and injury prevention and rehabilitation. Research related to biomechanics in competitive swimming for the Paris Olympic period highlights the significant role of biomechanics in optimizing swimming techniques, assessing athletic performance, and preventing injuries. Particularly, the advancement of sophisticated data collection and analysis equipment, such as high-precision sensors, artificial intelligence, and deep learning technologies, has made the analysis of swimming techniques more comprehensive and precise. Future research should further integrate multi-dimensional data technologies, employing high-precision motion capture, fluid mechanics measurement, and intelligent analysis to delve deeper into the pathways for optimizing swimming techniques.

Abstract:Objective To conduct a simulation study of the kicking process using the finite element method and investigate the effects of shoe upper stiffness on foot force and ball motion. Methods Solid models of bones, soft tissues, football shoes, and balls were established, and the kinematic parameters of the dorsal medial foot during ball striking were tested using an infrared high-speed motion capture system. The foot velocity and positional relationship between the foot and ball were loaded into the finite element model to complete the striking simulation. Results Different shoe upper stiffness affected the rotational speed of the ball, but had no significant effect on its translational speed. As the shoe upper stiffness increased, the pressure on the foot instep gradually increased and stabilized, with a maximum pressure difference of 200 N. The 1st and 5th metatarsal stress increased by 40.07% and 16.2%, respectively, and the 3rd and 4th metatarsal stress decreased by 22.96% and 4.64%, respectively. Conclusions Different shoe upper stiffness have a significant impact on the motion state of the ball. Compared to shoe materials with higher upper stiffness, shoe materials with lower upper stiffness effectively reduced pressure on the foot instep and helped to reduce the impact on bone stress, thus reducing the injury risks that may result from long-term wear.

Abstract:Objective To investigate the biomechanical factors of the lower limbs that affect the mechanical energy of baseball batting. Methods C3D data were collected using a motion capture system and imported into Visual 3D to establish a Hanavan multi-rigid-body human model and a rigid-body model of the bat. Using a prepared pipeline command, the angular velocities and joint torques of the hip, knee, ankle joints, and trunk around the X, Y, and Z axes were calculated and exported. Stepwise multiple linear regression analysis was performed between independent and dependent variables using SPSS, and the factors and dependent variables were incorporated into the regression model. Results The top four independent variables that had the greatest impact on the mechanical energy of the bat were as follows: x19 right ankle joint plantar flexion/dorsiflexion torque (β=91.97), x2 left ankle joint inversion/eversion torque (β=91.74), x25 right hip joint flexion/extension torque (β=91.58), and x3 left ankle joint internal rotation/external rotation torque (β=91.50). Conclusions There was a strong correlation between the right hip joint flexion/extension torque and mechanical work of the bat. The batter transmits energy to the upper limbs by producing a right hip joint extension torque to rotate the trunk and pelvis. There is a close relationship between the adduction and abduction torques of the left ankle joint and mechanical work of the bat, which are used for body braking in the early stages of batting and body rotation in later stages. It is necessary to conduct specific strength training for the adductors of the left ankle joint, extensors of the right hip joint, and plantar flexors of the right ankle joint to enhance batting power.

Abstract:Objective To investigate the distribution of cell membrane tension in a gradient fluid shear stress (FSS) field. Methods A gradient plate flow chamber model was constructed. Fluid-solid coupling numerical simulations were conducted to analyze the distribution of membrane tension with different FSS gradients and FSS amplitudes under varying hydrostatic pressures. Results With an increase in the flow rate at the inlet of the flow chamber, the FSS gradient exhibited a proportionally positive increase. Under the gradient FSS field, the cell membrane tension initially decreased and then increased from the bottom to the top of the cell. Under normal blood pressure, higher hydrostatic pressure was correlated with increased membrane tension. Larger FSS amplitudes resulted in higher membrane tension. When the FSS amplitude was constant, the average difference in membrane tension between the high- and low-FSS regions increased with the FSS gradient. Similarly, with a constant FSS gradient, the average difference in membrane tension between the high- and low-FSS regions increased with the FSS amplitude. Conclusions Local variation in cell membrane tension induced by gradient FSS was a crucial factor influencing the directional migration of osteoclast precursors in a gradient FSS field.

Abstract:Objective To explore the effects of disuse-induced architectural changes in the osteocytic lacunar-canalicular system (LCS) on the fluid dynamic microenvironment of osteocytes under mechanical stimulus. Methods First, taking the axially loaded mice tibia as the object, a multi-scale model of ‘whole bone-single osteocyte LCS’ was established. Subsequently, pressure gradients and other results obtained from the whole-bone poroelastic finite element model were used as boundary conditions for the single-osteocyte LCS model to calculate the flow velocity and shear stress around osteocytes. Finally, a design of experiment (DOE) method was used to determine the individual and interactive effects of the LCS architectural parameters (lacunar volume, lacunar shape, and canalicular diameter) on the osteocytic fluid dynamic microenvironment within the LCS. Results When the lacunar volume, lacunar shape, and canalicular diameter changed from normal to disused, the flow velocity increased by 5.3%, 39.3%, and 37.0%, respectively. The DOE results showed that the lacunar shape and canalicular diameter had a significant effect on fluid velocity and shear stress (P<0.05), with a contribution ratio of 0.38︰0.62, whereas the lacunar volume and interaction of architectural parameters had no significant effects. Conclusions Disuse-induced changes in canalicular diameter and lacunar shape were the main factors affecting the osteocytic fluid dynamic environment within the LCS under mechanical stimulus. Appropriate exercise methods are expected to prevent disuse bone loss caused by space weightlessness and other conditions.

Abstract:Objective To investigate the effects of insulin therapy on the mechanical behavior of solids, characteristics of fluid flow, and bone marrow stromal cell (BMSCs) differentiation in the distal femoral cancellous bone of type 2 diabetic rats under normal activity and vigorous exercise conditions. Methods The Finite element models of cancellous bones and fluids in the distal femurs of rats in the control, diabetes, treatment, and placebo groups in 4-week and 8-week insulin treatment experiments under normal activity and vigorous exercise conditions were established based on micro-CT scanning images. The mechanical and cell differentiation parameters of the models in each group were analyzed using the fluid-solid interaction numerical simulation method. Correlations between mechanical, cell differentiation, and microstructural morphology parameters were also analyzed. Results Insulin therapy under normal activity and vigorous exercise conditions improved the solid and fluid mechanical parameters and BMSC differentiation parameters in type 2 diabetic rats. In the 4-week experiment, insulin treatment under normal activity and vigorous exercise conditions increased the differentiation areas of bone in type 2 diabetic rats from 64.024% to 69.372% and from 73.225% to 75.336%, respectively; in the 8-week experiment, insulin treatment under normal activity and vigorous exercise conditions increased the differentiation areas of bone in type 2 diabetic rats from 67.239% to 72.910% and from 76.147% to 78.291%, respectively. Morphological parameters BV/TV, Tb.N, Tb.Th, Tb.Sp, and structure model index were significantly correlated with the differentiation areas of the bone and cartilage (P<0.05). Conclusions Under vigorous exercise conditions, BMSCs on the surface of cancellous bone in the 8-week insulin treatment group were more likely to differentiate into bone tissue. This study is of great significance for further understanding the effects of insulin on the bone under normal activity and vigorous exercise conditions, and provides theoretical guidance for the selection of the insulin therapy cycle and exercise mode in the clinical treatment of type 2 diabetes.

Abstract:Objective To investigate the role of miR-194-3p in regulating functional changes in osteoblasts in a simulated microgravity environment and to provide a theoretical foundation for understanding the mechanical response mechanisms of osteoblasts in extreme mechanical environments. Methods The effects of microgravity on osteoblasts were simulated by using a rotary cell culture system. MC3T3-E1 osteoblasts were transfected with an miR-194-3p inhibitor and changes in proliferation, differentiation, apoptosis, and mineralization were assessed using MTT assay, RT-PCR, western blotting, double fluorescence staining, and alizarin red staining. Results Elevated expression of miR-194-3p under simulated microgravity conditions led to the suppression of osteoblast proliferation, differentiation, and mineralization to a certain extent, while promoting osteoblast apoptosis. However, transfection with the miR-194-3p inhibitor significantly downregulated miR-194-3p expression and partially reversed the reduced osteoblast proliferation, decreased expression of osteogenic differentiation markers such as ALP, OCN, and COL-I genes and proteins, decreased bone mineralization nodules, and increased osteoblast apoptosis induced by microgravity exposure. These findings indicated that miR-194-3p effectively ameliorates abnormal osteoblast function under microgravity conditions. Conclusions MiR-194-3p acted as a negative regulatory factor in the mechanical responses of osteoblasts under simulated microgravity.

Abstract:Objective To predict the micro-level energy release rate in the rat femoral cortical bone and investigate the variation in the micro-level energy release rate with age. Methods Based on previous experimental data and numerical simulation of fracture modes for cortical bone, load-displacement curves and fracture modes measured by simulation and experiment were compared, and the micro-level energy release rates of rat femoral cortical bone at different months were predicted by back-calculation. Results It was predicted that the micro-level energy release rate of rat femoral cortical bone at 1-, 3-, 5-, 7-, 9-, 11-, and 15-month age was 0.08–0.12, 0.12–0.14, 0.15–0.19, 0.25–0.28, 0.23–0.25, 0.19–0.22, and 0.13–0.16 N/mm, respectively. Conclusions The decrease in the microlevel energy release rate with increasing age led to a decreasing failure load, indicating that the microlevel energy release rate is one of the main factors determining fracture occurrence; however, no significant decrease was observed at the time of fracture, indicating that the microlevel energy release rate was not linearly proportional to the fracture time. These results can help explain the mechanism of cortical bone fractures at the clinical level.

Abstract:Objective To investigate the biomechanical effects of the backside design of tibial trays on the bone-prosthesis fixation interfaces in unicompartmental knee arthroplasty (UKA). Methods Finite element models of medial knee arthroplasty were constructed using a fixed UKA prosthesis. The knee joint load and joint motion under walking motion were considered as boundary conditions, and the differences in tibial von Mises stress, contact stress, and micromotion of the bone-prosthesis fixation interface of the UKA tibial trays with big keel, small keel, two-peg with fin, three-oblique peg, and three-upright peg types were compared. Results At the maximum medical knee force moment, compared to the two-peg with fin type, the tibial von Mises stress, contact stress, and micromotion of the bone-prosthesis fixation interface decreased by 8% and 15.9% and increased by 9.9% for the big keel type; decreased by 12.3% and increased by 7.5% and 0.9% for the small keel type; decreased by 10%, 10.5%, and increased by 1.2% for the three-oblique peg type; and decreased by 7.7%, 14.7%, and 1.6% for the three-upright peg type, respectively. However, the maximum micromotion of the bone-prosthesis fixation interface occurred at 21% of the gait cycle. Compared to the two-peg with fin type, the micromotion of the bone-prosthesis fixation interface increased by 11.6% for the big keel type, increased by 1.6% for the small keel type, decreased by 0.4% for the three-oblique peg type, and decreased by 2.3% for the three-upright peg type. Conclusions To improve the long-term fixation effects of tibial prostheses, it is recommended to focus on a two-upright peg with fin or small keel designs when UKA tibial trays are designed, which can effectively balance the stress transfer and interface micromotion, thereby ensuring prosthesis stability and reducing the risk of aseptic loosening.

Abstract:Objective To analyze the influence of shaping on the bending strength of bone plates and the influence of different locking nail distributions on plate force to provide biomechanical references for shaping plates and selecting different locking nail distributions. Methods Finite element simulation analysis of the four-point bending strength of a plate was performed according to the YY/T 0342—2020 standard. Theoretical analysis and finite element simulation methods were used to analyze the force on prosthesis models with different lock-nail distributions. Results At 30° bending, the 3.7 mm-thick plate had 28% higher equivalent plastic strain than the 2.7 mm-thick plate. The 3.7 and 2.7 mm-thick plates had ultimate bending angles of 55° and 67°, respectively. The crease had little impact on the plate stress. The four-point bending strength and equivalent bending stiffness of the unshapeed structure were 2.64 N?m and 1.12 N?m2, respectively. The four-point bending strength and equivalent bending stiffness with the crease were 2.63 N?m and 1.10 N?m2, respectively. After forward and backward bending, the four-point bending strength of the plate decreased from 2.64 to 2.45 N?m by approximately 7.72%,and the equivalent bending stiffness decreased from 1.12 to 0.98 N?m2 by approximately 12%. The impact was obvious. After implantation of tamponade screws, the four-point bending strength of the single-hole plate improved significantly from 2.64 to 3.15 N?m, by approximately 19.32% and the equivalent bending stiffness increased from 1.12 to 1.14 N?m2, by approximately 2.1%. At least two locking holes were reserved on both sides of the fracture line. Not inserting the locking screw reduced the stress by approximately 50% compared with the full insertion of the locking screw. During 15-week postoperative walking without bone callus formation, the material stress of TC4 reached 852.7 MPa and yielding occurred. Conclusions In a clinical scenario where larger shaping is required, it is not suitable for plates with larger thicknesses and plate fractures are more likely to occur after large-thickness shaping. This can guide the clinical selection of plates with appropriate thickness based on the shaping angle, and tamponade screws can be implanted in extreme cases. Fixing locking screws clinically is recommended; however, a method of fixing the locking screws with full screws is not recommended. The biomechanical effect was best when two locking holes at both ends of the fracture line were maintained without fixing the locking screws.

Abstract:Objective To compare the stability of different Kirschner wire configurations for treating SH-2 type epiphyseal injury and damage to the epiphyseal plate in children. Methods The CT scanning data of a healthy femur from an eight-year-old child were collected; the image data were imported into Mimics 21.0 to establish a rough femoral and epiphyseal model, which was then imported into Geomagic 2013 to construct a surface model. The surface model was assembled in SolidWorks 2018 with three configurations (dispersed, double-crossed, and single-crossed K-wires) and then imported into ANSYS Workbench 2019. Various motion modes in reality were simulated through different mechanical loadings on the assembly. The maximum displacement of the fracture fragment, von Mises stress distribution, and maximum stress on the K-wire, epiphyseal plate, and fracture fragment were analyzed. Results The maximum displacements of the dispersed, double-crossed, and single-crossed K-wire groups occurred during abduction (2.39 mm), adduction (2.12 mm), and abduction (2.21 mm), and the maximum stress on the epiphyseal plate occurred during abduction (1.22 MPa), anterior flexion (0.20 MPa), and posterior extension (0.29 MPa), respectively. Conclusions The stability of the double-crossed K-wire configuration was superior to that of the dispersed and single-crossed K-wire configurations, with minimal damage to the epiphysis.

Abstract:Abstract: Objective To establish a bone knife deformation prediction model for periacetabular osteotomy and quickly and accurately predict bone knife deformation. Methods A finite element numerical model of a pelvic bone knife containing both cortical and cancellous bones was established, and the correlation between nodal strain and deformation was analyzed. The strains of 5 nodes with the strongest integrated correlation were selected as the inputs, and the displacement increments of the nodes on the blade part were established as the outputs. After training the model with the dataset, a deep learning neural network regression model based on the finite element dataset was used to establish a prediction model for the strain deformation of the bone knife. After the model prediction was completed, a binocular visual localization system was used to determine the spatially accurate position of the bone knife during the osteotomy procedure as a means of intraoperative tracking of the bone knife. Results The R2 value of the prediction model was 0.987 81 and the average deformation error after discretizing the bone knife into nodes was 0.07 mm. The prediction model quickly and accurately acquired bone knife deformation and showed great potential for reducing PAO surgical accidents. Conclusions The bone knife deformation prediction model developed in this study rapidly predicted bone knife deformation from strain information. Thus, it can avoid injuring tissues, such as nerves and blood vessels around the tissue, reduce the difficulty and risk of periacetabular osteotomy, and provide theoretical support for clinical application.

Abstract:Objective To explore proprioceptive changes in patients with knee osteoarthritis (KOA) before and after total knee arthroplasty (TKA). Methods Thirty-four KOA patients were selected as the experimental group and divided into posterior-cruciate-retaining TKA (CR-TKA) and posterior-stabilized TKA (PS-TKA) groups according to the surgical method and followed up for three months after the surgery. Twenty healthy individuals were included as the control group. The proprioception (position sense, kinesthesia, and force sense) of healthy individuals and KOA patients before and after surgery was assessed using the Biodex system III isokinetic training system, self-designed force sense test equipment, and surface electromyography test system, and the data were processed and analyzed. Results Compared with healthy individuals, KOA patients had significantly worse position sense at 30°, 45°, and 60°, kinesthesia, and semitendinosus force sense in the affected and unaffected knees (P<0.05). Three months after surgery, there were significant differences in the force sense of the affected biceps femoris and contralateral semitendinosus forces in the CR-TKA group compared with healthy individuals (P<0.05). There were no statistically significant differences in deviation for preoperative and 3-month preoperative position sense, kinesthetic sense, and force sense on the affected and contralateral knee joints between the CR-TKA and PS-TKA groups (P>0.05). Conclusions Knee proprioception in KOA patients was significantly impaired compared with that in healthy individuals. No significant improvement in proprioception was found three months after TKA in the CR-TKA and PS-TKA groups. There was no difference in proprioception among the different surgical methods. The results can provide data support for clinical diagnosis and treatment, as well as determine a direction for subsequent rehabilitation programs.

Abstract:Objective To explore the clinical efficacy of single unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) for the treatment of knee osteoarthritis. Methods A total of 21 patients who underwent TKA and 15 who underwent UKA were randomly recruited. Biomechanical tests were performed before surgery and at 6th and 12th month after surgery. A Vicon infrared motion capture system and Kistler three-dimensional force plate were used to simultaneously acquire the kinematic and kinetic data of the patients during stair walking. Results During stair ascent, the peak knee flexion moment in the TKA group was significantly lower than that in the UKA group; the time to peak knee flexion/adduction moment, knee flexion moment impulse, and load rate of the peak knee adduction moment in the UKA group were significantly lower than those in the UKA group. During stair descent, the peak knee extension power in the UKA group was significantly lower before surgery and at 6th month after surgery; the load rate of the peak vertical ground reaction force was significantly higher before surgery and the peak knee extension moment was significantly greater at 6th month after surgery; at 12th month after surgery, there was no significant difference in the biomechanical characteristics during stair ascent and descent. Conclusions The TKA and UKA groups showed similar knee joint function after surgery; however, compared with the UKA group, the TKA group may adopt a different lower extremity biomechanical pattern. The UKA group showed better quadriceps control after surgery and improved postural control during stair descent, whereas the TKA group adopted a conservative stair gait strategy to reduce the knee load. Compared with the peak moment, the time to peak moment and load rate of the peak moment were more sensitive indicators for determining the difference in the knee load.

Abstract:Objective To investigate the effects of electrical stimulation combined with muscle strength training on knee joint biomechanical characteristics in patients with patellofemoral pain (PFP). Methods Forty-six patients with PFP were recruited and randomly assigned to the muscle strength training (MST) and electrical muscle stimulation with strength training (EMS) groups. The intervention was performed three times a week for six weeks. The anterior knee pain scale (AKPS) was used to measure the knee pain degree. Knee kinematics, dynamics, and surface electromyography (sEMG) data were collected using an infrared motion capture system, force platform, and sEMG system during drop jumps before and after the intervention. Two-way analysis of variance with repeated measures was applied to determine the differences between the dependent variables of the two groups before and after the intervention. Results Compared with pre-intervention, the AKPS score, vastus medialis oblique (VMO)activation, VMO/vastus lateralis (VMO/VL) activation, maximum knee flexion angle, and peak knee extension moment increased significantly in the EMS group; the maximum knee abduction, external rotation angle, and peak knee external rotation moment decreased significantly in the EMS group after intervention. Compared with pre-intervention, the AKPS score, maximum knee flexion angle, and peak knee extension moment increased significantly in the MST group after intervention, the peak knee abduction and external rotation moment significantly decreased in the MST group after intervention. Post-hoc comparisons indicated that compared with the MST group, the AKPS score, VMO activation, VMO/VL activation were significantly higher and the maximum knee abduction angle was significantly lower in the EMS group. Conclusions EMS helped in the better balance muscle activation of the VMO and VL and corrected the excessive knee abduction angle during jump landing, which may be helpful in relieving pain and improving lower limb function in patients with PFP.

Abstract:Objective To study the effects of different implantation angles of bi-leaflet mechanical heart valve (BMHV) on swirling flow in the aorta. Methods Based on the aortic CT images of a healthy volunteer, the effects of 4 different valve implantation angles (0° , 45° , 90° and 135°) on the aortic rotational flow under constant flow conditions were studied by computational simulation. Results The implantation of BMHV could seriously interfere with the aortic rotational flow, affecting the structure and helicity distributions of the rotational flow in ascending aorta, thus resulting in disturbed blood flows distal to the valve. The 135° implantation angle caused the most disruption to the swirling flow, leading to the largest areas of reversed rotational flows, while the 0° and 45° implantation angles caused relatively smaller damage to the swirling flow. The areas with low wall shear stress (<0.5 Pa) were the smallest when the implantation angle of BMHV was 0°. Conclusions At the implantation angle of 0°–45°, the disruption of BMHV to the swirling flow in ascending aorta was relatively small. Therefore, for different patients, the selection of implantation angle should be individualized according to the spatial geometry of their aorta (including the aortic sinuses), and the implantation angle can be determined between 0°–45°.

Abstract:Objective To elucidate the influence of two procedures aortic root remodeling using a straight tubular artificial vessel while preserving the aortic valve and the Florida sleeve procedure on the biomechanics of the aortic root. Methods Five finite element models of the aortic root were reconstructed using computed tomography angiography images, including two cases of aortic root remodeling (A1 and A2), two cases of the Florida sleeve procedure (B1 and B2), and one control group without aortic root pathology (C). Numerical simulations were performed to obtain the blood flow and pressure distribution results to assess the differences in the hemodynamics of the aortic root. Results There were no significant differences in the peak systolic velocity between the two procedures and the control. However, the flow velocity after aortic root remodeling was smoother, similar to the model of the control group, with a more stable average aortic pressure and wall shear stress. In the Florida sleeve procedure, high-speed blood flow affected the vessel wall, leading to various degrees of wall shear stress and pressure concentrations along the aortic wall. Conclusions After aortic root replacement with valve preservation, blood flow patterns in the reconstructed aortic root depended on postoperative changes in sinus geometry. Both surgical procedures showed favorable blood flow patterns; however, the flow pattern after aortic root remodeling was more stable than that after the Florida sleeve procedure.

Abstract:Objective To study the mechanical properties and changes in the carotid vessels of cystic tumors during periodic blood flow to explore the specific mechanism of the development of cystic tumors and the effects of tumors on blood flow. Methods Finite element numerical simulation of the interaction between cystic tumors and blood in the carotid artery was conducted using a two-way fluid-structure coupling method. The deformation of blood vessels, blood velocity, mechanical properties in key areas, and influence of the tumor on blood vessels were analyzed. Results At the boundary between the tumor and blood vessels, the tumor showed a large deformation and low pressure on the tumor wall. The pressure on the opposite vascular wall and triangular area around the vascular bifurcation of the tumor was high, and it could easily stretch or rupture. The blood velocity inside the tumor was lower than that in normal blood vessels, indicating that the internal space of the tumor was not fully utilized. The wall shear force on the tumor during the pulsation period was always small, which lead to the deposition of impurities that form atherosclerotic plaque. Conclusions Cystic tumors interfered with normal blood flow in the blood vessels and promoted the production of mirror tumors. This study provides a theoretical reference for the treatment and prevention of cystic tumors. By understanding the mechanical properties of cystic tumors and their effects on blood vessels, doctors can develop personalized treatment plans and improve treatment outcomes.

Abstract:Objective To noninvasively assess the cerebral ischemic status using the velocity profile of the carotid and vertebral arteries measured by Doppler ultrasound and a neural network model. Methods Imaging data were collected from patients who underwent computed tomography perfusion (CTP) and Doppler ultrasound. Hemodynamic parameters were extracted from the ultrasound images. These parameters were used to train a fully connected neural network model. The resulting model was validated using the CTP results. Results Sixty-two eligible patients were included; 44 were randomly selected as the training dataset and 18 were designated for validation. In the training set, the area under the curve (AUC) of the receiver operating characteristic, sensitivity, specificity, and accuracy were 0.95, 0.833, 0.923, and 0.886, respectively. In the test set, the AUC, sensitivity, specificity, and accuracy were 0.860, 0.714, 1.000, and 0.889, respectively. Conclusions The model based on Doppler ultrasound and neural network was clinically verified and had good accuracy for assessing cerebral ischemia, showing its clinical potential for the early screening of cerebral ischemia.

Abstract:Objective To investigate the influence of changes in blood flow parameters on pulse rate characteristics by taking the advantage of controllable parameters in an experimental cardiopulmonary bypass system. Methods A set of human circulatory system equipped with an in vitro wrist model was established. By changing parameters such as the heart rate, wrist flow, pressure, and system compliance, a photoplethysmography pulse wave signal was obtained from the wrist model, and the time- and frequency-domain indices of pulse rate variability were extracted. Results Changes in heart rate, pressure, and system compliance caused a change in pulse shape, but the time domain indices NN50 and PNN50, which indicate pulse rate variability, were zero, and the other indices and frequency domain indices were in the very low value category. Conclusions In the absence of heart rate variability, hemodynamic changes in heart rate, wrist flow, blood pressure, and system compliance did not produce significant pulse rate variability. This study can provide a reference for studies on pulse rate variability and heart rate using more convenient wrist acquisition equipment.

Abstract:Objective To investigate the dynamic mechanical responses and damage characteristics of peri-implant bone structures subjected to impact load. Methods A finite element model of the peri-implant bone microstructure was established, and an initial velocity was applied to the rigid body to simulate the impact load. A stress failure criterion was employed and a user-material subroutine was developed to assess failure. Subsequently, bone damage after the impact load was analyzed according to the material subroutine. Results After the impact load, the stress on the cortical bone increased rapidly, reaching a peak value (5.92 MPa) immediately. In contrast, the stress on the trabecular bone at the bottom of the implant reached its peak value (5.85 MPa) at 0.1μs. The impact load resulted in stress waves that propagated and diffused within the bone structure, causing changes in the bone structure damage over time. The generated impact energy could be absorbed and dissipated by the trabecular bone through deformation. The deformed trabecular bone experienced damage and failure upon reaching the yield limit, whereas the cortical bone did not experience damage or failure under an impact load. Conclusions Structural changes in the trabecular bone should be considered in patients with impact damage. The numerical model established in this study can effectively predict bone impact damage by combining the structural mechanical properties and geometric characteristics of the bones. These findings can serve as a reference for assessing bone damage and post-damage treatment in patients subjected to impact loads in clinical practice.

Abstract:Objective To analyze the stress distributions of two root canal preparation shapes of oval root canals with micro-crack. Methods Twenty single-canal mandibular premolars with oval canals were expanded to create micro-cracks. Roots were sectioned after staining. The generation and distribution of dentin micro-cracks were observed under microscope. Then a finite element (FE) model of sectioned enlarged oval canal roots with micro-cracks was established. The stress distribution of micro-crack and root were analyzed under lateral loading. Results Cracks always appeared in the buccolingual sides of oval canal roots and extended from the intracanal wall to the root surface. This was consistent with the stress concentration on the buccolingual side of the root canal wall shown by FE analysis. When micro-cracks occurred, stresses were transferred to the crack tip and the peak values increased sharply nearly 5 times. This made the cracks propagate easily along this direction, especially in the long axis direction of the tooth. Conclusions The presence of micro-cracks does not change the general stress concentration on root with two preparation morphologies of oval canals. However, the micro-crack causes an extreme stress concentration in the crack tip. This may be the mechanism of rapid propagation of microcracks into vertical root fracture, and dentists need to pay high attention.

Abstract:Objective To investigate the equivalent conversion of head injury criterion (HIC) under anterior-posterior (AP) and lateral-medial (LM) craniocerebral impact for mild craniocerebral injury in rats using motor evoked potential (MEP) and β-amyloid precursor protein (β-APP) immunohistochemistry (IHC). Methods Sixty healthy adult male SD rats were randomly divided into 0 m control group, 0.5 m-AP and 0.5 m-LM injury groups, and 1 m-AP and 1 m-LM injury groups (12 rats in each group). The control group did not undergo any impact injury experiment. After the impact injury experiment, the injury and control groups were subjected to excessive anesthesia to produce β-APP immunohistochemical stained slices, and the percentage of positive area and integral optical density (IOD) in the brainstem pyramidal tract area of the slices were determined. The MEP groups were divided in the same manner as the IHC groups and the MEP amplitudes of the MEP and control groups were measured after the impact injury experiment. Results With an increase in the degree of injury, the decrease in MEP amplitude, percentage of positive areas, and IOD in the injury groups significantly increased. When the degree of injury was low, the sensitivity of IHC was higher than that of MEP. When the degree of injury was the same, the HIC in the LM direction was lower than that in the AP direction. When the HIC was the same, the degree of injury in the LM direction was greater than that in the AP direction. Conclusions The joint evaluation of MEP and β-APP can provide experimental references for the study of HIC equivalent conversion in AP-LM craniocerebral impact injury.

Abstract:Objective To study the effects of vaginal delivery on the biomechanical properties of uterosacral ligaments (USLs) and cardinal ligaments (CLs) and to further explore the effects of vaginal delivery on pelvic organ prolapse (POP). Methods Adult sows (five parous and five nulliparous) were selected as animal models. The passive mechanical behavior of USLs and CLs in vitro was determined using uniaxial tensile experiments, and the effects of delivery on the biomechanical properties of USLs and CLs were analyzed. Results The passive mechanical behavior of the sow uterine ligaments was nonlinear. Regardless of delivery, the maximum stress of the right USLs was greater than that of the left USLs (P<0.05). After delivery, the mechanical properties of the right and left USLs differed significantly. The maximum stress of the left CLs in nulliparous sows was slightly greater than that of the right CLs (P<0.05), and the difference between the left and right CLs was reduced after delivery (P>0.05). The maximum stress of USLs was greater than that of CLs, indicating that USLs could be subjected to more tension than CLs and that USLs played a key role in POP. Conclusions This study provides a reference for understanding the mechanical properties of USLs and CLs, guidance for the development of better treatments such as reconstructive POP surgery, and a theoretical basis for preventing POP.

Abstract:Objective To investigate corneal biomechanical differences in different geometric design parameters of orthokeratology lenses (OK lenses) and to further reveal the corneal shaping mechanism of OK lenses. Methods A coupled finite element model of the aspheric OK lens corneosclera was established for various geometric design parameters of the OK lens, corresponding to different degrees of myopia correction. The distribution trends of the profile and curvature of the corneal anterior surface, as well as the von Mises stress (VMS) and eye axis displacement on both the corneal anterior surface and superior corneal stroma surface were analyzed numerically. Results The stress concentration of the corneal anterior surface was observed in the mid-peripheral and peripheral zones, whereas that of the superior corneal stroma surface appeared in the mid-peripheral zones. The sagittal height of the base curve of the OK lens decreased with increasing degree of myopia correction. At myopia correction degrees of -2.0, -3.0, -4.0, -5.0, and -6.0 D, the maximum corneal VMS increased by 0.81%, 1.86%, 2.84%, 3.81%, and 7.04%, respectively, compared with that at -1.0 D; the curvature of the corneal central zone was reduced by an average of 2.59, 3.78, 4.51, 4.99, 5.33, and 6.41 D compared with that without OK lenses. Conclusions The sagittal height of the base curve of the OK lens decreased with increasing degree of myopia correction, resulting in a flatter central curvature of the cornea. The base curve of the OK lens plays a crucial role in both correction and control of myopia.

Abstract:Objective Airway resistance (R) and lung compliance (C) under non-invasive positive pressure ventilation (NPPV) conditions were measured using a brief pressure release at the end of expiration, and the measurement accuracy was also evaluated. Methods An NPPV respirator was developed by programming a method for calculating R and C. An experimental platform based on the active servo lung ASL5000 was designed. By simulating a healthy adult (R=5 cmH2O and C=50 mL/cmH2O), an adult patient with acute respiratory distress syndrome (R=10 cmH2O and C=30 mL/cmH2O), and an adult patient with chronic obstructive pulmonary disease (R=20 cmH2O and C=50 mL/cmH2O), a series of experiments for calculating the R and C were conducted. Results The maximum relative error of R was -12.67%, which occurred in calculating the R of an average adult. The maximum relative error of C was 17.37%, which occurred when calculating the C values of patients with acute respiratory distress syndrome. Each group of data was analyzed using a paired t-test, which showed statistically significant differences (P>0.05). Conclusions The calculation method for R and C at the end of expiration during NPPV is feasible, and its realization and application will be beneficial for achieving precise and personalized respiratory ventilation.

Abstract:Soft tissue and organ defects or degeneration, caused by trauma, disease, and aging, lead to a great burden on human health, and soft tissue regeneration technology has shown great promise for addressing these challenges. In recent years, interdisciplinary efforts in the fields of biomechanics, mechanobiology and regenerative medicine have highlighted the critical roles of mechanical cues in microenvironment in regulating soft tissue regeneration. Despite these advances, there is still a lack of comprehensive understanding regarding the mechanical features of soft tissues in clinical practice, and the full potential of such mechanical features for diagnosing and treating soft tissue diseases has not been fully known. In this review, the concept of ‘mechanomedicine for soft tissue regeneration’ is proposed. Subsequently, the possible influence mechanisms of mechanical cues on soft tissue development and regeneration are systematically described from four distinct aspects, i.e., multi-scale biomechanics of soft tissues, mechanobiology of soft tissue regeneration, mechanomedicine techniques for soft tissue regeneration, and applications of mechanomedicine for soft tissue regeneration. Finally, the potential of mechanomedicine in clinical diagnosis of soft tissue diseases and soft tissue defect repair is discussed, thereby providing a new direction for the development of mechanomedicine for soft tissue regeneration.

Abstract:The impact of various anterior cervical surgeries on biomechanical properties of cervical vertebrae varies depending on the specific surgical techniques employed. However, accurately measuring the mechanical characteristics of individual parts of the cervical vertebrae or implants within them in a clinical setting can be challenging. As a result, the finite element method is commonly utilized in studies on anterior cervical surgery, allowing for the precise analysis of stress and strain distributions in different areas of interest through computer simulations. This method facilitates the study of biomechanical properties associated with different anterior cervical surgical approaches. This review discusses the progress of finite element analysis in anterior cervical surgery, summarizes current research findings on fusion and non-fusion procedures, hybrid surgeries, and minimally invasive techniques, so as to provide theoretical references for the selection of different anterior cervical surgical interventions from a biomechanical perspective.

Abstract:The main types of bone tissue cells include osteoblasts, osteoclasts, and osteocytes, which work together with the extracellular matrix to maintain the structural integrity and functionality of the bone. Osteoclasts are specifically responsible for bone resorption, degrading the bone matrix through the release of acidic substances and proteolytic enzymes. Osteoclasts coordinate with osteoblasts to maintain bone homeostasis. An increased number of osteoclasts leads to an increased bone resorption, which can cause osteoporosis and other skeletal diseases; deficiency in osteoclast generation can lead to a weakened bone resorption and related diseases, such as osteopetrosis. Therefore, a precise regulation of osteoclast function plays a crucial role in maintaining the balance of bone homeostasis. Previous studies have mostly explained and elaborated on the regulation of osteoclasts by various biological factors from a bio-chemical perspective. However, more and more studies have confirmed that mechanical stimulation plays an important role in the differentiation process of osteoclasts. This review focuses on the impact of mechanical stimulation on osteoclast differentiation, discusses the possible roles it may play, and explores the new discoveries and future development in this field.