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Abstract:The research about physiological changes caused by special mechanical environment in aerospace activities have always been important parts of mechanobiology researches. This review summarizes the progress of aerospace mechanobiology researches in 2023, primarily focusing on the biological effects of weightlessness, including results obtained at the cellular, model animal, and human levels under both real space and ground-based simulated weightlessness, so as to assist the development of aerospace mechanobiology, as well as health protection or countermeasures for astronauts and relevant populations on the ground.

Abstract:On the earth, the majority of cellular functions are regulated by mechanical loads. The effects of cell response to mechanical loads under microgravity on the adaptive changes of physiological functions in space cannot be ignored. The cytoskeleton is widely considered as one of the key structures through which cells sense gravity variation and respond to mechanical loads. In this review, the research progress on the changes and mechanisms of the ‘ cytoskeleton-LINC complex-nuclear lamina’ pathway in cellular mechanoperception and mechanotransmission under microgravity is summarized, and the future research is prospected.

Abstract:Objective To study the effects of intramedullary pressure on the fluid flow behavior in bones. Methods Multi-scale models of macro bone tissue and macro-meso osteon groups were established using The COMSOL Multiphysics software. Considering the interrelationship of different pore scales, such as the bone marrow cavity, Haversia canal, and bone lacunar-canaliculus, the pore pressure and flow rate of hollow bone tissues and bone tissues with intramedullary pressure were compared, and the effects of the amplitude and frequency of intramedullary pressure on the pressure and flow velocity of the liquid in the bone were analyzed. Results When intramedullary pressure was considered, the pore pressure in bone tissues with intramedullary pressure was 6.4 kPa higher than that in hollow bone tissues. The flow pressure increased significantly with an increase in the intramedullary pressure amplitude, but the flow velocity remained unchanged. The frequency of intramedullary pressure had little effect on pore pressure and flow velocity. Conclusions The multi-scale pore model established in this study can accurately analyze bone fluid flow behavior. These results are of great significance for an in-depth understanding of force conduction in the bone.

Abstract:Objective To investigate the effect of facet joint resection at different ranges under endoscopy on the stability of the cervical spine and provide a biomechanical theoretical basis for clinical surgery. Methods A normal finite element model of The cervical spine C5-6 was established based on CT data, and unilateral facetectomy models with different ranges (0, 25%, 50%, 75%, and 100%) of laminectomy were obtained (Models 1-5) by simulating cervical endoscopic surgery. The ranges of motion (ROMs) of C5-6 and the von Mises stresses of the discs for the models in each group were compared and analyzed. Results Except for flexion, Models 1 and 2 showed insignificant changes in ROMs and disc von Mises stresses in each direction compared with those of the normal model. Model 3 showed a noticeable increase in ROMs and disc von Mises stresses in each direction compared with those of the normal model: ROMs under flexion, extension, left lateral bending, right lateral bending, left rotation, and right rotation increased by 27%, 4%, 3%, 13%, 5%, and 16%, respectively, and von Mises stresses increased by 32%, 4%, 2%, 5%, 9%, and 5%, respectively. Models 4 and 5 exhibited a significant increase in the ROMs and disc von Mises stresses in each direction compared to the normal model. For Model 4, ROMs were increased by 27%, 14%, 6%, 24%, 7%, 167%, and von Mises stress were increased by 33%, 13%, 3%, 32%, 10%, 130%. For Model 5, ROMs were increased by 27%, 17%, 6%, 25%, 7%, 167%, and von Mises stresses were increased by 33%, 29%, 8%, 33%, 12%, 138%. Conclusions As the range of unilateral facetectomy increased, cervical ROM and disc von Mises stress extremum gradually increased. The cervical spine shows a significant ROM increase and stress changes when facet joint resection on one side exceeds 1/2. More than 1/2 of the facet joint should be preserved during surgery to avoid medical instability.

Abstract:Objective To compare the stability of multi-rod structures with double-headed screws and traditional connectors in posterior three-column osteotomy of the spine using finite element analysis. Methods A finite element model of the T3-L4 thoracolumbar spine was constructed based on postoperative computed tomography (CT) data of patients with severe kyphosis. Based on the patient’s standard two-rod model (2R), a double-headed screw multi-rod structure model (4R-DHS) and a traditional connector multi-rod structure model (4R-TC) were constructed. The two models were evaluated under 300 N follower load and 7.5 N·m moment load, and the stability, maximum von Mises stresses on the main rods, and stress distributions of the two multi-rod structures were analyzed. Results There was little difference in the stability between the two multi-rod structures. Compared with 4R-TC, 4R-DHS showed a decrease in the maximum von Mises stresses on the main rods during all motions (the stress decreased by 7.2%, 8.8%, 8.7%, 18.5%, and 16.9% during flexion, left lateral bending, right lateral bending, left axial rotation, and right axial rotation, respectively) and more uniform stress distribution, except for a slight increase in the maximum von Mises stresses on the main rods during post-extension. Conclusions The double-headed screw multi-rod structure can reduce the maximum stress on the main rod compared with the traditional connector multi-rod structure, and there is no problem with stress concentration on the main rod near the connector, which can more effectively reduce the risk of internal fixation failure.

Abstract:Objective To explore the mechanical properties of modified cortical bone trajectory (MCBT) and cortical bone trajectory (CBT) in lumbar revision surgery using finite element analysis and to analyze the advantages of MCBT over CBT in lumbar revision. Methods A three-dimensional (3D) model of the L1-5 vertebral body, endplate, annulus fibrosus, and nucleus pulposus was established based on CT tomography data. The traditional trajectory (TT) was used for pedicle screw placement in the vertebral body model; then, the TT screws were removed, retaining the TT screw path, and revision screws were placed on the vertebral body with MCBT and CBT screws. The mechanical properties of the MCBT and CBT during revision surgery were analyzed using finite element analysis. Results Under flexion, extension, lateral bending, and axial rotation, the range of motion (ROM) in the CBT revision group decreased by 12.07%, 19.60%, 8.72%, and 7.66%, respectively; the annulus stress of L3-4 segment increased by 11.27%, 30.43%, 35.52%, and 25.36%, respectively; and the annulus stress of L4-5 segment decreased by 39.84%, 52.64%, 23.91%, and 15.77%, respectively, compared with the control group. The ROM in the MCBT revision group decreased by 13.18%, 20.27%, 25.63%, and 8.59%, respectively; the annulus stress of the L3-4 segment increased by 10.41%, 21.60%, 15.83%, and 18.41%, respectively; and the annulus stress of the L4-5 segment decreased by 37.14%, 61.94%, 39.46%, and 35.23%, respectively, compared with the control group. The ROM of the MCBT revision group decreased by 1.26%, 0.83%, 18.53%, and 1.00%, respectively. The annulus stress of the L3-4 segment decreased by 0.77%, 6.77%, 14.53%, and 5.54%, respectively, whereas that of the L4-5 segment decreased by 2.82%, 15.91%, 19.79%, and 8.75%, respectively, compared to the CBT revision group. Compared with the CBT revision group, the annulus stress of the L4-5 segment in the MCBT revision group increased by 4.49% under flexion and decreased by 19.65%, 20.44%, and 23.11% under extension, lateral bending, and axial rotation, respectively. Conclusions Both MCBT and CBT can provide mechanical properties that meet the requirements of vertebral fixation, and the fixation performance and safety of MCBT are comparable to those of CBT. This study provides a reference for using the MCBT and CBT techniques in revision surgery in clinical practice.

Abstract:Objective To investigate the biomechanical effects of the medial protrusio technique on the acetabular cup in adult patients with developmental hip (DDH) after total hip arthroplasty. Methods The CT scanning data of bilateral hips from an adult patient with unilateral DDH were obtained further to develop a finite element model of the affected hemipelvis. The medial protrusio technique with various levels of medial protrusio was simulated, and the biomechanical differences between the medial protrusio and non-protrusio groups were evaluated. Results In the simulated pull-out test, the maximum anti-pull-out load strength of the non-protrusio group was 1 166 N. Compared with the non-protrusio group, the anti-pull-out load strength of the 4 mm and 8 mm medial protrusio groups increased by 45.8% and 57.1%, respectively. The peak micromotion at the cup-bone interface for the non-protrusio group was 166.4 μm in the standing phase of the gait cycle, and that of the 4 mm and 8 mm medial protrusio groups was decreased by 46.2% and 62.1%, respectively. Regarding the immediate stress distributions of periacetabular bone tissues following cup implantation, the differences between the groups were not significant. Under the loading condition of the standing phase, the non-protrusio group yielded the lowest average and peak stresses. The average stress increased with the level of medial protrusio, and the highest peak stress was observed in the 4 mm medial protrusio group. Conclusions The medial protrusio technique can improve the initial stability of the acetabular cup, and the initial stability is positively proportional to the protrusio level. However, owing to the concentration of marginal stress at the cup-bone interface, a minor medial protrusio cup with insufficient bone coverage might increase the risk of various prosthesis-related complications.

Abstract:Objective To analyze the differences in the initial stability of an acetabular cup with a Voronoi polyhedral porous structure and a solid acetabular cup and to explore the impact of the Voronoi polyhedral porous layer on the initial stability of the acetabular cup, as well as its role in preventing loosening and dislocation. Methods Voronoi polyhedral porous scaffold structures with 60% and 70% porosities were designed using the Grasshopper software. Specimens of solid and porous acetabular cups with 60% and 70% porosities were manufactured using selective laser melting technology. Lever tests on the acetabular cups were conducted using polyurethane block models under identical conditions, and the maximum lever-out moment, angular displacement, and interface stiffness of the three groups of specimens were analyzed and compared. Results Under the condition of no significant differences in the compression force, for porous acetabular cups with porosities of 60% and 70%, the maximum lever-out moment increased by 278.82% and 320.56%, the angular displacement increased by 194.04% and 269.23%, respectively, and the interface stiffness increased by 18.58% and 7.88%, respectively, compared with that of solid acetabular cups. After the lever-out tests were completed, significant wear was observed within the polyurethane block hemisphere cavity using the porous acetabular cups. Conclusions The initial stability indicators of acetabular cups with a Voronoi polyhedral porous structure were higher than those of solid acetabular cups, indicating that the Voronoi polyhedral porous layer can enhance the initial stability of the acetabular cup. These results provide a reference for designing and selecting acetabular components.

Abstract:Objective To investigate the effects of three-dimensional (3D) screws and circular plates on the biomechanical stability of Sanders ABⅢ calcaneal fractures. Methods Calcaneal computed tomography (CT) and magnetic resonance imaging (MRI) data from a 26-year-old volunteer were collected to establish a 3D finite element model of a Sanders IIIAB calcaneal fracture fixed with 3D screws and circular plates. A longitudinal load of 700 N was applied to compare the variations in the stress, displacement of the bone block, and internal fixation in the different models. Results Under 700 N longitudinal loads, the maximum displacement of the bone block and the maximum stress of the bone block and internal fixation were concentrated at the intersection of the posterior talar articular plane internal fixation and fracture line. The overall displacements of the bone blocks in the 3D screw and circular plate models were similar. Compared with the circular plate model, the maximum and average stresses of the bone block and internal fixation in the 3D screw model were lower, and the displacement and stress changes of the 3D screw model were closer to those of the complete calcaneal bone model. Conclusions In the fixation of Sanders IIIAB calcaneal fractures, both 3D screw and circular plate fixation methods can provide good stability. The biomechanical properties of the 3D screws were better than those of the circular plates, which is consistent with the biomechanical characteristics.

Abstract:Objective To propose a topology-optimized design method for bone plates that effectively reduces stress concentration and improves bone healing compared with traditional topology-optimized methods. Methods Based on the load constraints of a bone plate in a broken bone-splint system, an improved topology optimization method based on the load path is used to optimize the design of the bone plate structure. Subsequently, a bone regeneration simulation model based on bias strain was used to simulate the transverse fracture of the tibial tuberosity, and the force state, fixation stability, and healing performance of the optimized plate were evaluated based on data from the bone regeneration process. Results Using the optimized bone plate based on the load path optimization method, the maximum stresses of the bone plate were 55.68 MPa and 42.23 MPa at volume fractions f=0.55 and 0.65, respectively, which were reduced by 32.96% and 29.95%, respectively, compared with the optimized bone plate using the traditional topology optimization method. The average elastic moduli of the callus after the bone-healing process were 1 439.47 MPa and 1 355.71 MPa, respectively. These values were 145.86% and 131.06% higher than those of traditional bone plates, respectively. Conclusions In this study, the proposed improved topology optimization method based on the load path was used to optimize bone-plate structures. Compared to the bone plate obtained using the traditional topology optimization method, the optimized bone plate was more uniformly loaded and safer. The bone-healing performance was significantly improved compared to the traditional bone plate. These results provide a new method for the optimal design of internal fixation implants for fractures.

Abstract:Objective To estimate the flexion and extension torques of the hip, knee, and ankle joints during straight-line walking using depth cameras and neural networks. Methods Gait information was collected from 20 individuals using an optical motion capture system, force plates, and an Azure Kinect depth camera. The subjects were asked to walk straight at their preferred speed while stepping on the force plates. The joint torques were obtained using visual 3D simulation as a reference value, and an artificial neural network (ANN) and long short-term memory (LSTM) network were trained to estimate the joint torques. Results The relative root mean square errors (rRMSEs) of the ANN model for estimating the joint torques of hip, knee, and ankle were 15.87%－17.32%, 18.36%－25.34%, and 14.11%－16.82%, respectively, and the correlation coefficients were 0.81–0.85, 0.69–0.74 and 0.76–0.82, respectively. The LSTM model had a better estimation effect, with rRMSEs of 8.53%－12.18%, 14.32%－18.78%, and 6.51%－11.83%, and correlation coefficients of 0.89－0.95, 0.85－0.91 and 0.90－0.97, respectively. Conclusions This study confirms The feasibility of using a depth camera and neural network for noncontact estimation of lower limb joint torques, and LSTM has a better performance. Compared with existing studies, the joint torque estimation results have better accuracy, and the potential application scenarios include telemedicine, personalized rehabilitation program development, and orthosis-assisted design.

Abstract:Objective To investigate the effect of sustained fatigue on the passive and active biomechanical characteristics of the knee. Methods Twenty-seven healthy university students were recruited to perform A fatigue experiment using an isokinetic dynamometer. The fatigue experiment included three fatigue cycles with more than 30 sustained quadriceps submaximal voluntary isometric contractions per cycle. The maximum passive torque, mean maximum voluntary contraction (MVC) torque, integrated electromyography of the vastus lateralis and biceps femoris, and co-contraction index (CI) at different fatigue cycles were compared. Results The maximum passive torque decreased significantly only after the 3rd fatigue cycle (P<0.05). The mean MVC torque and integrated electromyography of the vastus lateralis and biceps femoris decreased significantly during the 1st, 2nd, and 3rd fatigue cycles (P<0.05). However, the CI did not change significantly (P>0.05). Conclusions Sustained fatigue intervention with 90-fold isometric contraction training of The quadriceps significantly affected the active and passive biomechanical properties of the knee. After fatigue intervention, the resistance of the knee joint to passive flexion and extension decreased. With fatigue intervention, the active contraction ability of the quadriceps decreased, and the activation of the quadriceps femoris and hamstring muscles also decreased; however, the co-contraction level of the two muscle groups remained unchanged. This mild muscle group co-contraction pattern is beneficial for maintaining a benign mechanical loading environment in the knee joints. These results help us understand the active and passive biomechanical properties of knee joints after fatigue.

Abstract:Objective To study changes in the kinematics and joint coordination of the shoulder, elbow, and wrist joints during rolling manipulation performed by Tuina doctors. Methods The kinematic data of 10 beginners and 10 proficient Tuina doctors performing rolling manipulation were collected using a Vicon three-dimensional (3D) motion capture system, and the differences in movement patterns of the shoulder, elbow, and wrist joints between the two groups during Tuina rolling manipulation were compared. Results There was no difference in the elbow joint activity angle between the beginner group and proficient group during rolling manipulation (P>0.05), and the main differences were in the angles of wrist flexion/extension and shoulder adduction/abduction. The proficient group had a smaller shoulder adduction/abduction angle (P<0.05), and the maximum angle of palmar flexion of the wrist joint in the proficient group was significantly greater than that of the beginner group (P<0.05). Conclusions The main kinematic characteristics of rolling manipulation are flexion/extension of the wrist and rotation of the elbow and shoulders. Rolling manipulation is mainly the composite movement of forearm rotation and wrist flexion/extension. The essential ‘sinking shoulder’ operation was better mastered by the proficient group.

Abstract:Objective To investigate the biomechanical effects of lateral wedge insole (LWI) on internal tissues of the foot and ankle (including foot bones, joints, and ligaments). Methods A three-dimensional finite element model of the foot-insole-ground was developed and validated, and the plantar pressure distributions, contact pressures on joints, and peak stresses on metatarsals and major ligaments in barefoot model and insole intervention models at three key gait instants were explored. Results The 5° LWI model reduced the peak plantar pressure by 65. 8% compared to the barefoot model. Insole interventions decreased the peak contact pressure at the cuneonavicular joint, but increased the peak contact pressure at the subtalar joint and peak stress at the 4th and 5th metatarsals. Conclusions This study quantitatively assesses the biomechanical effects of LWI on various parts of the foot and ankle, and suggests a design that can appropriately reduce the inclination angle of LWI at the 4th and 5th metatarsals.

Abstract:Objective To predict the constitutive parameters of a superelastic model of plantar soft tissues based on random forest (RF) and backpropagation (BP) neural network algorithms to improve the efficiency and accuracy of the method for obtaining constitutive parameters. Methods First, a finite element model for a spherical indentation experiment of plantar soft tissues was established, and the spherical indentation experiment process was simulated to obtain a dataset of nonlinear displacement and indentation force, divided into training and testing sets. The established RF and BP neural network (BPNN) models were trained separately. The constitutive parameters of plantar soft tissues were predicted using experimental data. Finally, the mean square error (MSE) and coefficient of determination (R2) were introduced to evaluate the accuracy of the model prediction, and the effectiveness of the model was verified by comparison with the experimental curves. Results Combining the RF and BPNN models with finite element simulation was an effective and accurate method for determining the superelastic constitutive parameters of plantar soft tissues. After training, the MSE of the RF model reached 1.370 2×10-3, and R2 was 0.982 9, whereas the MSE of the BPNN model reached 4.858 1×10-5, and R2 was 0.999 3. The inverse-determined constitutive parameters of the plantar soft tissues suitable for simulation were obtained. The calculated response curves for the two predicted sets of constitutive parameters are in good agreement with the experimental curves. Conclusions The prediction accuracy for the superelastic constitutive parameters of plantar soft tissues based on an artificial intelligence algorithm model is high, and the relevant research results can be applied to study other mechanical properties of plantar soft tissues. This study provides a new method for obtaining the constitutive parameters of plantar soft tissues and helps to quickly diagnose clinical problems, such as plantar soft tissue lesions.

Abstract:Objective To investigate the relationship between upper limb joint angles and muscle fatigue in overhead tasks and develop a muscle fatigue prediction model based on residual neural networks (ResNet). Methods Through the simulation of drilling experiments performed with different working postures and on different operating surfaces, the maximum voluntary contraction, maximum endurance time, maximum residual muscle force, and subjective fatigue ratings were measured. The collected data were processed and used as input for the ResNet prediction model, which was constructed to predict muscle fatigue levels. Results The ResNet model exhibited outstanding predictive accuracy, with a root mean square error (RMSE) of 0.028. Compared with traditional backpropagation neural networks (RMSE=0.053) and multilayer perceptron neural networks (RMSE=0.059), they displayed smaller errors and better fitting. Conclusions The proposed residual neural network muscle fatigue prediction model can effectively and accurately predict muscle fatigue, providing strong support for improving work efficiency and reducing the risk of work-related musculoskeletal disorders.

Abstract:Objective To predict the torque on the affected side of the hip, knee, and ankle joints in stroke patients during walking using principal component analysis (PCA) and backpropagation (BP) neural networks. Methods Kinematic and dynamic data from 30 stroke patients were synchronously collected using an 8-lens Qualisys infrared point high-speed motion capture system and Kistler three-dimensional (3D) force measurement platform. The torques of the hip, knee, and ankle joints in the stroke patients were calculated using OpenSim, and the initial variables with a cumulative contribution rate of 99% were screened using PCA. The normalized root mean square error (NRMSE), root mean square error (RMSE), mean absolute percentage error (MAPE), mean absolute error (MAE), and R2 were used as evaluation indicators for the PCA-BP model. The consistency between the calculated joint torque and predicted torque was evaluated using Kendall's W coefficient. Results PCA data showed that the trunk, pelvis, and affected sides of the hip, knee, and ankle joints had a significant impact on the torque of the affected sides of the hip, knee, and ankle joints on the x, y, and z axes (sagittal, coronal, and vertical axes, respectively). The NRMSE between predicted and measured values was 5.14%―8.86%, RMSE was 0.184―0.371, MAPE was 3.5%―4.0%, MAE was 0.143―0.248, and R2 was 0.998―0.999. Conclusions The established PCA-BP model can accurately predict the torque of the hip, knee, and ankle joints in stroke patients during walking, with a significantly shortened measurement time. This model can replace traditional joint torque calculation in the gait analysis of stroke patients, provides a new approach to obtaining biomechanical data of stroke patients, and is an effective method for the clinical treatment of stroke patients.

Abstract:Objective Biomechanical analyses of straight techniques for Chinese male skaters during the 1500-m race were conducted to determine the influence of motion techniques on sports performance. Methods Thirty-four male skaters participating in the 1500-m National Speed Skating Championship race were selected as research subjects. Kinematic characteristics were collected using three-dimensional fixed-point video analysis. The correlations between the periodic characteristics, motion phase characteristics, moment characteristics, and periodic velocity were analyzed. Results The period distance (r=0.560), gliding distance (r=0.554), and push-off distance (r=0.512) showed strong positive correlations with the periodic velocity. The trunk angle (r=0.651), mean ankle angle (r=0.434), and ankle angle (r=0.446) showed moderate or high positive correlations with the gliding velocity. The mean trunk angle (r=-0.427) showed a moderate negative correlation with gliding velocity. Additionally, the mean trunk angle (r=0.673), hip extension angle (r=0.804), abduction angle (r=0.560), and abduction angle speed (r=0.566) were highly positively correlated with the push-off velocity. The mean push-off angle (r=-0.605) showed high negative correlations with push-off velocity. Conclusions The velocity of a straight line in 1 500-m speed skating depends on the dancing distance. Greater gliding and push-off distances result in higher velocities. The trunk and ankle angles significantly influence the gliding velocity, and appropriately increasing the range of the trunk angle can effectively improve the gliding velocity. The trunk, hip, and push-off angles are key determinants affecting push-off velocity, and actively extending the hip and pushing-off can effectively enhance push-off velocity.

Abstract:Objective To establish an ideal model of the mitral valve, including the left heart and blood, and study the motion characteristics of the mitral valve in blood flow using the fluid-structure interaction (FSI) simulation. Methods Based on anatomical parameters, models of the mitral valve, left heart, and blood were established. The finite-element combined immersed boundary method was used for FSI to simulate the motion of the mitral valve using the LS-DYNA software. Morphological, mechanical, and hemodynamic parameters were compared with those obtained from structural simulations. Results The morphological results of the mitral valve from the two simulations differed significantly, and the FSI results matched the ultrasound images. The stress distributions of the leaflets in the FSI and structural simulations were consistent. The maximum first principal stresses calculated by FSI and structural simulations were 1.48 MPa and 1.53 MPa, respectively, with a relative error of 3.27%. The fluid field in the left heart was complex with vortex structures, and the maximum mitral flow velocity was 1.02 m/s during diastole, consistent with the physiological data of healthy humans (0.89±0.15 m/s). Conclusions The morphological results of the mitral valve obtained from the FSI simulation were closer to those in the physiological state. FSI simulations can provide flow patterns that are indispensable for clinical diagnosis. Structural simulations are more efficient for studying leaflet stress distribution.

Abstract:Objective To calculate the pre-stretching of the microscopic components of the aortic wall under physiological homeostasis by considering a three-dimensional (3D) residual stress field. Methods The aortic wall was simplified into a double-layer ideal circular tube, and the 3D residual stress field of the vascular wall was calculated based on a 3D expansion angle experiment. Then, the in vivo stress distribution characteristics under mean blood pressure and the pre-stretching of each microscopic constituent of the vascular wall under a physiologically steady state were obtained. The inverse problem was constructed according to the internal pressure-radius relationship measured in vivo. Physiological homeostasis of the aorta was considered the reference state, and inversion identification of the material parameters of the aorta in vivo was realized while integrating the three residual stress fields. Results When the residual stress was not considered, the mean stress of the middle membrane was greater than that of the outer membrane. When residual stress was considered, the outer membrane bore more stress than the middle membrane, and the outer membrane protected the middle membrane. The pre-stretching of the middle film with residual stress is lower than that without residual stress, whereas the pre-stretching of the outer film is higher than that without residual stress. Moreover, the pre-stretching of the outer membrane collagen fibers was greater than that of the middle membrane collagen fibers. The in vivo calculations of the material parameters of the aorta were performed using physiological homeostasis as the reference configuration, and the proportion of each component was consistent with the experimental results. However, the proportion of elastin in the outer membrane was significantly overestimated when the non-stress configuration was used as the initial configuration, which was inconsistent with the experimental results. Conclusions Residual stress significantly influences the pre-stretching and physiologically steady mechanical states of the microscopic components of the aortic wall. Therefore, it is necessary to fully consider the influence of residual stress to establish the physiologically steady state of the aortic wall accurately. Furthermore, it is also necessary to fully consider the 3D characteristics and layer specificity of residual stress in the in vivo identification of material parameters.

Abstract:Objective To improve the efficiency and quality of end-to-end anastomosis, a novel degradable vascular anastomosis device was designed, and the relationship between pressure distance and biomechanical properties of the anastomotic stoma was explored. Methods A three-dimensional (3D) structure of The vascular anastomosis device was designed and a prototype was fabricated with extruded high-purity magnesium. A finite element model of the end-to-end vascular anastomosis was established to study the stress distributions of the anastomosis end face under different pressure distances (0.4, 0.5, 0.6, 0.7, and 0.8 mm) and their change rules. In vitro experiments were conducted to verify the rationality of the finite element results as well as the feasibility and effectiveness of the vascular anastomosis device. Results When the pressure distance was 0.6 mm, the anastomosis tensile force, and burst pressure could reach (11.79±0.64) N and (39.32±2.99) kPa, respectively, meeting the clinical requirement for the strength of vascular anastomosis, and with the minimal mechanical damages to tissues. Conclusions The device designed in this study can be used for vascular anastomosis by adjusting the pressure distance, and it can improve operation efficiency, reduce mechanical damage to tissues, and further improve the quality of anastomosis. These results provide an essential reference for the design of degradable vascular anastomosis devices.

Abstract:Objective To explore the biomechanical responses of the cupula of the human semicircular canal to three basic rotational perception processes. Methods A one-dimensional visual semicircular canal model was successfully fabricated using three-dimensional printing and hydrogel physical cross-linking technologies, and the response deformation of the cupula was explored by applying constant angular velocity, constant angular acceleration, and sinusoidal oscillation stimulations. Results The time constant of the biomimetic semicircular canal model was stable at approximately 3 s and close to the human time constant. The displacement deformation of the ampullary cupula was proportional to the angular acceleration applied. Under sinusoidal oscillation stimulation of 0.07–5.00 Hz, the gain of the semicircular canal increased from 1.54 μm/° rises to 42.34 μm/°, but the phase difference decreased from 109.72° to 11.27°. Conclusions The biomimetic semicircular canal model prepared in this study can accurately simulate the working mechanism of the human semicircular canal and is expected to play a role in mechanism research and disease diagnosis of the human vestibular semicircular canal.

Abstract:Objective To investigate the biomechanical effects of lingual metal-reinforced denture bases on edentulous implant-supported prostheses by three-dimensional finite element analysis, and provide references for the treatment of edentulous jaws. Methods Two implant-supported Locator-type overdenture models with lingual metal-reinforced and non-reinforced denture bases were constructed. A 150 N vertical load on the fovea of the posterior teeth, a 150 N oblique load on the fovea of the posterior teeth, and a 150 N vertical load on the anterior teeth were applied to simulate the centric occlusion, left and right lateral chewing, and anterior teeth cutting, and stresses on the tissues of two models were analyzed. Results When the posterior and anterior teeth were loaded vertically, the stress distribution on each organization was similar between the two denture base designs. The maximum stress difference was between 0 and 0.16 MPa. Under unilateral masticatory chewing, the range of stress concentration on denture base, implant and mucoperiosteum, and the maximum stress of the implant and peri-implant bone without metal reinforcement were significantly greater than those with metal reinforcement, and the maximum stress difference was between 0.59 MPa and 2.99 MPa. Conclusions Lingual metal-reinforced denture base can play a role in stress dispersion, or reduce the risk of bone resorption and denture base fracture to a certain extent.

Abstract:Objective To study the stress distributions of the surrounding bone during the dynamic implantation of micro-implants, a finite element model of self-attacking micro-implant dynamic implantation was proposed and established. Methods A three-dimensional (3D) oral model was constructed using CBCT data. The local model around the implant and the 3D finite element model of the micro-implant were established using ABAQUS software. The micro-implant was implanted into the jaw with an axial propulsion force of 40 N at a constant speed of 0.5 r/s. Results A 3D finite element model was successfully established to simulate dynamic self-attacking orthodontic microimplant implantation in The jaw bone. The implantation stage and thread position affected the jawbone stress. The maximum stress on the cortical bone was 167 MPa, and the maximum stress at the stable stage was approximately 50 MPa. The maximum stress on cancellous bone was 30 MPa. Conclusions The implantation stage and thread position have apparent influences on stress distribution. The stress difference between the cortical and cancellous bones was evident. The stress characteristics can judge the bone type, and whether the jaw is in a suitable implantation state can be judged by the bone stress distributions around the implant.

Abstract:Mitochondria are highly dynamic organelles, which not only provide energy and material basis for cells, but also regulate cell proliferation, migration, differentiation, and apoptosis. Cell fate is regulated by mechanical cues from the microenvironment. Recent studies have shown that energy metabolism is regulated by mechanical cues. Mitochondria can act as mechanical sensors and hubs that connect the mechanics and metabolism to regulate cell fate. A deep understanding of the relationship between the mechanical microenvironment and mitochondrial metabolism provides sufficient guidance for promoting tissue regeneration and treating diseases. In this review, the progression in mitochondrial mechanobiology is mainly introduced and its potential applications in tissue regeneration and disease treatment are explored.

Abstract:Artificial hearts (blood pumps) exhibit excellent hydraulic performance and compatibility with blood. Improvement in blood pump performance depends on the design and optimization methods. This review summarizes relevant work on designing and optimizing centrifugal blood pumps. First, the progress of numerical simulation methods was reviewed. High-fidelity flow field numerical simulations are prerequisites for design and optimization. The parameter sensitivity studies are summarized mainly from the aspects of the impeller, volute, and clearances. Several commonly used design and optimization methods have been summarized, including parameter sensitivity research, orthogonal optimization, machine learning/genetic algorithms, and topology optimization. Finally, the prospects and challenges for designing and optimizing blood pumps are discussed. This review provides valuable references and guidance for the future design and optimization of blood pumps.