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Abstract:Objective To study the effect of neck restrain on traumatic brain injury during airbag inflation in traffic accidents. Methods Based on the previously validated 3-year-old child head finite element (FE) model, the impact on out-of-position (OOP) child occupant during airbag inflation was simulated by FE method, so as to investigate the effects of neck restraint on intracranial response and injury mechanism in traffic accidents. Results The head kinematics with neck restrain was different from that without neck restrain under the impact of airbag inflation. The neck restraint would obviously decrease the maximum Von Mises stress of pediatric brain. When airbag-head distance was 20 cm or 25 cm, the neck restraint would obviously decrease the maximum intracranial pressure. Conclusions Neck restraint had a relatively large influence on pediatric intracranial response. When the FE method is used to predict pediatric craniocerebral injury, consideration of neck restrain on child brain response is necessary.

Abstract:Objective To analyze the influence of different geometric parameters on flexibility of the commonly used Z-shaped stent-grafts for treating thoracic aortic aneurysm, as well as the primary and secondary order of such influence. Methods The three-dimensional models of the stent-grafts with different strut numbers, wire diameters, crest height, bending radius were established by SolidWorks and imported to ANSYS software for finite element analysis．The 60° rotation of X-axis was applied to the stent-grafts, and the flexibility of the stent-grafts was evaluated according to 3 evaluation parameters (Von Mises stress, reaction force and bending torque)． Results After bending of the stent-grafts, the maximum stress was concentrated on the inside of the bend；reducing the wire diameter, crest height and strut number of the stent-grafts, the flexibility of the stent-grafts would increase; increasing the bending radius， the flexibility of the stent grafts would increase; the effect of the wire diameter and strut number on flexibility of the stent-grafts was stronger than that from the bending radius and crest height． Conclusions The strut number, wire diameter, crest height, bending radius had a significant impact on flexibility of the stent-grafts. The research findings can provide theoretical references for the selection and optimal design of the stent-grafts in clinic, and have a positive influence on reducing the incidence rate of complications such as new entry.

Abstract:Objective To conduct simulation analysis on support performance of the stent by using finite element method, and optimize structure parameters of the stent by using Kriging surrogate model, so as to provide more scientific guidance for clinical treatment with design and development of the stent. Methods The contact model was established by penalty function method. The generalized variational principle was selected as theoretical basis of the numerical simulation, and the theory of Kriging surrogate model was used for finite element optimization on support stiffness of the stent, so as to study the effect from the number of circumferential support, the length of the support and the initial diameter on support performance of the stent. Results With the increase of the number of circumferential support or the length of the support, the support performance showed the decreasing tendency; with the increase of the initial diameter, the support performance showed the increasing tendency. From seven stents by using the theory of Kriging surrogate model, it was concluded that structural parameters of the optimal stent were: the number of circumferential support was six, the length of the support was 1.15 mm, and the initial diameter was 1.65 mm. Conclusions The numerical result agreed well with the experimental data and the error was smaller than 5%, and the error rate of experimental repeatability was within 0.5%, which verified effectiveness and rationality of the finite element analysis. The optimization of support performance provides an important reference for design and exploration of new magnesium alloy stent.

Abstract:Objective To investigate the mechanical behavior of bovine pericardium with different orientations after compression and evaluate its effects on the duration of transcatheter aortic valve. Methods According to the fiber directions, the pericardial strips were divided into 12 groups of transverse, longitudinal and oblique pericardial strips, and each group included 3 strips of pericardium. One strip maintained the original state, and the other two strips were under 12.5 N and 25 N compression, respectively for 1 h. The mechanical properties of compressed samples were tested and analyzed subsequently in uniaxial tension test. Results The samples with different orientations showed obvious anisotropy before and after compression. The secant modulus, elastic modulus and ultimate tensile strength of the longitudinal pericardium were generally greater than those of the oblique pericardium, while the oblique pericardium was larger than the transverse pericardium. For longitudinal and oblique bovine pericardium under 25 N compression, the average tensile strength ratio was 0.92 and 0.87, respectively, and the ratio of tensile strength before and after compression had a significant difference (P＜0.05). The average tensile strength ratio of transverse bovine pericardium after 25 N compression was 0.97, and there was no significant difference in the ratio of tensile strength before and after compression (P＞0.05). Conclusions The compressive damage of the pericardia with different fiber orientations was very small under low stresses at transitory time. For design and production of transcatheter aortic valves, the orientations of the pericardium and the changes of strength after compression should be taken into consideration.

Abstract:Objective Based on OpenSim platform, an improved musculoskeletal model was developed to analyze the force of lumbar muscle groups under forward flexion. Methods The existing lumbar musculoskeletal model was improved via modifying constraints of lumbar vertebrae to restore them into 6 degrees of freedom (DOF). The 30 year-old and 70 year-old muscle models were established respectively by adjusting muscle parameters according to Thelen’s model, adding stiffness matrixes and abdominal pressure (AP) characterized by concentrated force to investigate the effects of arm swing, movement velocity, varying AP and muscle aging on the force distribution of 9 lumbar muscle groups during forward flexion. Results A multi-body musculoskeletal model with 9 lumbar muscle groups was developed. Based on the computations of 0°-70° flexion, the results showed that arm swing reduced the force of psoas and external oblique abdominis, while under the movement of forward flexing to 70° and returning up-right, the force of psoas, erector spinae, rectus and external oblique abdominis obviously increased, when the time of flexing-returning process was reduced from 5 s to 2.5 s, and in the 5 s case, increasing AP reduced the force of psoas but increased the force of transversus, internal and external oblique abdominis. In the 2.5 s case, there was no obvious difference between the 30 year-old and 70 year-old muscle models under different conditions. Conclusions The developed model provides an effective method to analyze the force of lumbar spine and muscles, and it certainly shows a potential application in the fields of kinematic mechanics and rehabilitation engineering with further development of basic theory.

Abstract:Objective To evaluate the influence of facet joint arthroplasty at different positions under lumbar percutaneous endoscopy on range of motion (ROM) of vertebral bodies by using the three-dimensional (3D) finite element method. Methods The 3D finite element model of normal L3-5 segment was established, and lumbar percutaneous endoscopy was simulated by doing cylindrical excision of bone with diameter of 7.5 mm on the tip or basement of L5 facet joint, so as to obtain normal lumbar vertebra model, L5 facet joint model with shaped tip, L5 facet joint model with shaped basement, respectively. Given specific loading conditions, the ROMs of adjacent vertebral bodies for the 3 models under flexion, extension, left and right lateral flexion, left and right rotation were compared. Results When L5 facet joint tip was shaped, the ROMs of L4-5 under extension，left lateral flexion, right lateral flexion, left rotation and right rotation were obviously larger than those of the normal model, especially under left rotation. When the L5 facet joint basement was shaped, the ROMS of L4-5 under left and right rotation increased slightly compared with those of the normal model. However, the ROMs of L3-4 for both tip-shaped and basement-shaped L5 facet joint model showed no obvious changes under six different motions. Conclusions The influence of L5 facet joint with shaped tip on ROMs of L4-5 was relatively larger than that of L5 facet joint with shaped basement under lumber percutaneous endoscopy. There was no significant effect on the ROMs of L3-4 with L5 facet joint arthroplasty.

Abstract:Objective The current manipulator with double parallel quadrilateral mechanism should be connected in series with a flexible degree of freedom (DOF) mechanism, which increases the volume of the manipulator, decreases the motion flexibility and creates the interference between the mechanical arms that hold the mirror and the device. Aimed at solving this problem, a novel mechanical arm was put forward to enhance the motion flexibility and reduce the volume of the manipulator. Methods The mechanical arm was designed by using the mechanism of five-link, slider and slide rail lower pair and wire transmission to realize the telescopic movement of the end effector. The kinematics model of the manipulator was established, and the MATLAB was used as the simulation tool to verify the correctness of the D-H parameters under the specific zero joint angle, and the motion equation of the manipulator was solved. Meanwhile, the three-dimensional workspace of the end effector was obtained by using Monte Carlo algorithm, and the preoperative plan of animal experiment for 3 arms was performed. Finally, cholecystectomy and other operations were acted in pigs, to verify the rationality and maneuverability of the design of double 5-link 2-DOF manipulator. Results The working space of Monte Carlo algorithm under MATLAB environment was -650.4 mm＜x＜649 mm, 163.8 mm＜y＜1 202 mm and -254.6 mm＜z＜829.8 mm. Sixteen cases of pig cholecystectomy were successfully completed, with an average operation time of 51 minutes. Conclusions The novel double 5-link 2-DOF manipulator could successfully complete cholecystectomy and other operations in pigs, which had no other symptoms after the operation. There was no interference between the mechanical arms, which fully verified the feasibility of the design scheme of the robot manipulator for minimally invasive surgery.

Abstract:Objective To construct a new biomechanical testing system of in vitro spine based on LabVIEW and six-axis robot arm and conduct preliminary reliability studies, so as to make preparation for further studies on coupled motion testing. Methods By programming on LabVIEW platform, using Ethernet and Profibus to communicate the data of the robot arm with PC in real time, the displacement control and load control were realized, and the end position and rotation angle of the robot arm were read in real time. Through the force/torque sensor and data acquisition (DAQ), board DAQ, processing, storage and other functions were acquired. Using the digital micrometer and special stationary fixture, the 6-direction translation accuracy test was completed, and the data were analyzed. The flexion, extension, lateral flexion and rotation were applied on sheep spine specimen to draw the load-displacement curve, analyze and compare the experimental result, and verify the effectiveness of the biomechanical platform. Results A biomechanical test system with high precision for spine in vitro based on LabVIEW and 6-axis robot arm was developed and established, of which the average translational precision was 8.1 μm and the average translational accuracy was 56.7 μm. The program of control, data acquisition, data processing and storage were written, and the biomechanical test of the sheep spine was completed effectively. Conclusions This biomechanical test system based on Labview and 6-axis robot arm could complete the conventional three-dimensional spinal motion test with high precision and be used to conduct coupled motion test research in the next step.

Abstract:Objective To investigate the effects of rounding on the prediction of flow field and hemolysis for FDA benchmark blood pumps by using the method of computational fluid dynamics（CFD）. Methods Key properties such as hydraulic characteristics, mean velocity distributions and hemolysis index of FDA benchmark blood pump under three operating conditions were simulated, and the influence of the above simulation result was further compared when the impeller was equipped with or without rounding. Results The rounding of blood pump impeller had impacts on pump head (the maximum percentage difference between the impeller with rounding and without rounding was 57.38%), velocity distributions, which led to a considerable impact on predicted hemolysis levels (the maximum error between the impeller with rounding and without rounding was more than one order of magnitude). Conclusions Impeller with rounding was beneficial for optimization of blood pump performance. The research findings are of great importance for better use of CFD to aid the hemocompatibility design of blood pump.

Abstract:Objective To investigate the effect of different fluid shear stress (FSS) on the regulation of planar cell polarity (PCP) signaling, and further to explore the relationship among FSS, PCP signaling pathway and ciliogenesis. Methods The hydrodynamic cell model of adjustable FSS was established. qPCR and immunofluorescence were used to detect the mRNA expression of PCP signaling pathway core protein Dvl2 and cilia assembly protein IFT88, cell targeting and co-localization under different FSS. Western blot (WB) was used to detect the protein expression of Dvl2 at 18 h under different FSS. Results The qPCR result showed that compared with 1.5 Pa FSS, under 0.1 Pa FSS, the mRNA expression of Dvl2 was higher at 6 h and 18 h (P＜0.05), significantly higher at 12 h (P＜0.01); the mRNA expression of IFT88 was significantly higher at 18 h (P＜0.01). The WB result showed that compared with 0 h, under 0.1 Pa FSS, the protein expression of Dvl2 was higher at 18 h (P＜0.05), significantly lower under 1.5 Pa FSS (P＜0.01); compared with 1.5 Pa FSS, the protein expression of Dvl2 was higher at 18 h under 0.1 Pa FSS (P＜0.05). The immunofluorescence result showed that the positive expression of Dvl2 increased with the loading time on FSS increasing, and gradually aggregated at a point around the nucleus; the positive expression of IFT88 was gradually transferred from the nucleus to the cytoplasm and aggregated at a point under 0.1 Pa FSS, and gradually decreased and depolymerized under 1.5 Pa FSS. Protein Dvl2 and IFT88 were located in the same position in cells under 0.1 Pa FSS and before 18 h under 1.5 Pa FSS, and colocalization of proteins Dvl2 and IFT88 was not observed after 18 h under 1.5 Pa FSS due to IFT88 depolymerization. Conclusions Laminar FSS played an inhibition on the transduction of PCP signaling pathway and a hindrance on the process of ciliogenesis, while low FSS played a promotion on the transduction. PCP signaling pathway might regulate FSS-induced ciliogenesis by Dvl2.

Abstract:Objective To investigate the role of microRNA-214-3p (miR-214-3p) in differentiation and proliferation of endothelial progenitor cells (EPCs) induced by cyclic stretch. Methods EPCs were exposed to cyclic stretch at physiological level (with the magnitude of 5%, at a constant frequency of 1.25 Hz) for 24 h by FX-5000T Strain Unit. miRNAs array was performed to identify the expression profiling of miRNAs. Real-time PCR was used to examine the expression levels of miRs. The expression of vascular smooth muscle cells (VSMCs) markers in EPCs was detected by real-time PCR. EPC proliferation was detected by BrdU ELISA assay. After EPCs were transfected with miR-214-3p inhibitor (IN) to knockdown expression of miR-214-3p, the level of VSMC markers expression and EPC proliferation was detected. Results Cyclic stretch significantly decreased miR-214-3p expression, depressed EPC differentiation toward VSMCs, and increased EPCs proliferation. Similarly, transfection with the miR-214-3p inhibitor led to the decreased expression of VSMC markers under static station. Meanwhile, miR-214-3p down-regulation promoted EPC proliferation significantly. Conclusions Physiological cyclic stretch could down-regulate the expression of miR-214-3p in EPCs, depress EPC differentiation towards VSMC and promote EPC proliferation eventually. Therefore, the research findings provide a potential therapeutic strategy for treating vessel injuries.

Abstract:Objective To compare the in vivo degradation rates of two different kinds of high purity magnesium bone screws by animal experiments, so as to make some suggestions on structural design of high purity magnesium bone screws. Methods High purity magnesium bone screws with threads and without threads were implanted into femoral condyles of New Zealand rabbits separately. Twenty-four rabbits were randomly divided into 3 groups. They were euthanized at 8, 12 and 16 weeks after operation, respectively. The in vivo degradation rates of bone screws with two different shapes were compared through micro-CT scanning and Skyscan CT-analyser software, and the stress changes during the progress of bone screw degradation were analyzed. Results The initial surface area of threaded screws ［(31.70±0.06) mm2］ was significantly greater than that of the non-threaded ones ［(29.56±0.22) mm2］. After 8, 12 and 16 weeks, the volume loss ratios of the threaded screws were (26.01±3.44)%, (33.35±5.05)%, (36.84±6.99)%, respectively, and the volume loss ratios of the non-threaded screws were (22.53±4.78)%, (31.12±6.59)%, (43.22±9.31)%, respectively. At the same time point, there were no significant differences in the volume loss ratio between two kinds of screws. The relationship between the volume reduction and the implantation time was linear for non-threaded screws and gradually decreasing for threaded screws. Conclusions Under the low-bearing condition, different structural design for high purity magnesium screws has no obvious effect on their degradation rate in vivo.

Abstract:Objective To investigate the shear rate and VWF-A1-mediated platelets calcium response. Methods Flou-4 AM was used as the fluorescent indicator of intracellular calcium, and the intracellular calcium concentrations of adherent platelets on VWF-A1 with different concentrations at different shear rates were detected by parallel plate flow chamber system combined with fluorescence microscope. The effect of shear stress and chemical signaling on intensity and speed of calcium response was also analyzed. Results VWF-A1 specifically mediated platelet adhesion and calcium response under flow. The shear rate and molecular concentrations had positive regulation of platelets activation ratio and negative regulation of delay time of calcium response. Compared with static conditions, the activation ratio was increased by 37 times at shear rate of 500 s-1. When the concentration of VWF-A1 was increased from 60 mg/L to 240 mg/L, the delay time of calcium response was shortened by 10 s. Conclusions The shear rate could modulate the calcium response of platelets in cooperation with VWF-A1. The result of this study will be helpful to deepen the understanding about the process of hemostatic reaction of platelet coagulation in bloodstream.

Abstract:Objective To analyze human gait stability by acceleration signal at the head and lumbar under different walking conditions, and make comparison with parameters by the traditional COM (center of mass)-COP(center of pressure) method, so as to discuss the reliability of applying wearable sensors to analyze human gait stability. Methods The harmonic ratio (HR) parameter at the head and lumbar based on acceleration signal was applied to analyze gait stability of 18 healthy young adults under 3 walking conditions (footwear normal walking, barefoot normal walking and barefoot walking at different velocities), and the results were compared with the assessment results from the COM-COP method. Results Walking at normal velocity was most stable, with the maximum HR parameter. Compared with footwear walking, HR parameters were significantly decreased (P＜0.05) during barefoot walking, indicating that gait stability was reduced. The results were consistent with the assessment results from the COM-COP method. Considering the factors of walking velocity and footwear, the gait stability parameters obtained by the two methods showed a significant negative linear correlation (R2＞0.50). Lumbar HR parameter and COM-COP parameters showed a stronger linear correlation (R2＞0.65). Conclusions The application of acceleration signal-based analysis algorithm could effectively and reliably evaluate the stability of human gait, and acceleration at the lumbar was more sensitive than the head signal for analyzing gait stability.

Abstract:Objective To observe the analgesia efficacy of continuous fascia iliaca compartment block (FICB) and adductor canal block (ACB) on elderly patients undergoing total knee arthroplasty (TKA) with multimodal analgesia and their early rehabilitation. Methods Sixty TKA patients (26 female and 34 male, 60-75 years old) were randomly divided into two groups and received ultrasound-guided either continuous FICB (n=30) or continuous ACB (n=30) using 0.25% ropivacaine for controlled analgesia. All the patients had no previous experiences of knee surgery. Quality of analgesia was assessed by dynamic and static visual analogue scale (VAS) based on pain intensity. In addition, rehabilitation training compliance, range of motion (ROM) and knee function were assessed at different times after rehabilitation training. Results No significant differences were found in VAS scores during resting and passive functional exercise at 6, 12, 24, 48 h after TKA surgery (P>0.05); ACB group had significant differences in rehabilitation training compliance, knee ROM and HSS scores in comparison with FICB group (P<0.05). Conclusions Ultrasound-guided continuous ACB with multimodal analgesia could promote early rehabilitation after TKA．

Abstract:Achilles tendon is the key structure to connect the heel and foot plantar flexors and transmit the force from the leg triceps muscle, which is the key to storing and releasing energy storage during running and jumping. At present, the primary causes of Achilles tendon injury are non-homologous loading during stance phase and deficient recovery after overload. However, the relevant measures to prevent Achilles tendon injury cannot achieve full recovery. This paper reviewed the research progress of Achilles tendon’s motor function and its application in biomechanics domestically and internationally, reconsidering the role of Achilles tendon in human running and jumping which included anatomical structure of the Achilles tendon, the relationship between internal force and external force, and the effective training program. The key for future research on motor function of Achilles tendon is to improve its mechanical properties, keep the increased load in a better range and ultimately improve motion performance and reduce sports injury from the source.

Abstract:Vena cava filter was widely used in clinic to prevent pulmonary embolism in treating lower extremity deep venous thrombosis（DVT）. In this paper, application status of vena cava filter was reviewed, including the way of vena cava filter implantation, filter classification, indications of filter implantation and existing problems (contraindications and complications). The frontier issues concerning study on novel filters, such as the degradation filter and drug coated filter was also analyzed, and the hemodynamic research progress from domestic scholars in recent years about filter structure was briefly summarized. The research findings provide references for further optimization of filter structure and clinical application of vena cava filter.