Abstract:

Abstract:

Abstract:

Abstract:Objective To describe the effects of axial loading, small-scale parameter, bioliquid density in a microtubule (MT) and constrained stiffness of surrounding biomedium on the coupling vibration frequency in the bioliquid-filled MT, and to provide references for ultrasonic inspection on nano-MT under axial loading and the clinical application of biological medicine. Methods The non-local elastic theory was utilized to describe the nano-scale characteristics of the MT, and the analytic solutions to the coupling vibration frequency of the bioliquid-filled MT under axial loading were given. Results The axial loading exerted on the bioliquid-filled MT made the couple vibration frequency drop rapidly, and as the small-scale effect increased, the couple vibration frequency of the bioliquid-filled MT was gradually decreased. The effect of axial loading on the couple vibration frequency of the bioliquid-filled MT was larger than that of the small-scale parameter. Conclusions When the density of bioliquid in MT increases, the first order frequency of the bioliquid-filled MT embedded in biomedium is decreased; when the initial axial loading exerted on the bioliquid-filled MT increases, the effect of bioliquid density in MT on the first order frequency of bioliquid-filled MT is reduced gradually.

Abstract:Objective To study distributions of the residual stresses on blood vessel, and to provide the biomechanical basis for the finite element research on stress changes in blood vessel. Methods The semi-inverse method was used for getting distributions of residual stresses on blood vessel and the result was compared with that from Commercial Software ABAQUS. On that basis, the interaction between the vessel and implanted stent was simulated to get the influence of residual stress on blood vessel. Results Distributions of three normal stresses on blood vessel obtained from the two methods were almost consistent. It is the residual stress that led to the change of vessel stress distributions, and the position of maximal stress was transformed from the inside to the outside of the vessel. Conclusions Assuming that the vessel has homogeneity and isotropic, both the semi-inverse method and the finite element method would get the similar residual stress distributions; significant differences existed between the stress states of vessel with or without considering residual stress. The stress at the inside of vessel was reduced obviously. Consideration of residual stress will be helpful for understanding the real stress state of vessel after stent deployment and providing references for the optimization design of stent.

Abstract:Objective To obtain elastic modulus through displacement of the ear structure. Methods The finite element model (FEM) of human ear structure based on Patran software was constructed and the neural network for inverse derivative of elastic modulus for the ear was established using Matlab software. The frequency response of the ear structure FEM was calculated to obtain the displacements of tympanic membrane and stapes. The displacements acting as input data of training samples and the corresponding elastic modulus acting as output data were used to train the neural network. Results The elastic modulus was inversely derived by adopting this mature neural network with relatively less error. Conclusions The viability of the proposed methods for inverse derivative of elastic modulus was demonstrated in this paper, which could provide a simple and effective method to obtain mechanical parameters for clinic work.

Abstract:Objective To investigate the feasibility of simulating the deformation and displacement of lung tumors by simulating the motion of lung tumors during respiration using finite element method (FEM). Methods The CAD (computer-aided design) surfaces of the lung at multiple inhalation phases were reconstructed from 4D CT images of a patient with lung tumor. The finite element model was established according to the surface at the beginning of inhalation. Distributed surface loads were defined by the differences between each individual surface and the surface at the beginning of inhalation, and applied to the surface of the model. The motion and deformation of lung tumors were then simulated using FEM within the inhalation cycle. Results The numerical simulation indicated that the estimated errors for the lung and the tumor’s motion and deformation were less than 2 mm and 1 mm, respectively. The use of linear elastic relationship for tumor with elastic modulus of 50 kPa could achieve higher precision in simulation. Conclusions The deformation of lung and the displacement of lung tumor are possible to be simulated accurately by FEM. This research provides references for the X-ray free lung tumor tracking method based on numerical simulation.

Abstract:Objective To study the failure tolerance in long bones of lower limbs under dynamic loads. Methods Based on the finite element (FE) model of lower limb for Chinese people, the dynamic three-point bending test on the femur, tibia, leg and thigh was conducted , and the FE model was validated against the cadaveric experiment. Results The force-displacement curves between FE simulation and cadaveric experimental results for bending tests were correlated. The contact forces on femur, tibia, thigh and leg with failure tolerance were 4.29, 3.94, 4.81 and 4.086 kN, respectively，and the displacements from the impactor were 17.78, 34, 52.1, and 47.06 mm, respectively. The simulation results were correlated well with those in dynamic cadaveric experiments. Conclusions This study validated the effectiveness of the FE model, which would lay a good foundation for the further research on validation of FE model of knee joint and whole lower limb, and provide the theoretical references for the protection of pedestrians in crashes.

Abstract:Objective To study the failure tolerance in long bones of lower limbs under dynamic loads. Methods Based on the finite element (FE) model of lower limb for Chinese people, the dynamic three-point bending test on the femur, tibia, leg and thigh was conducted , and the FE model was validated against the cadaveric experiment. Results The force-displacement curves between FE simulation and cadaveric experimental results for bending tests were correlated. The contact forces on femur, tibia, thigh and leg with failure tolerance were 4.29, 3.94, 4.81 and 4.086 kN, respectively，and the displacements from the impactor were 17.78, 34, 52.1, and 47.06 mm, respectively. The simulation results were correlated well with those in dynamic cadaveric experiments. Conclusions This study validated the effectiveness of the FE model, which would lay a good foundation for the further research on validation of FE model of knee joint and whole lower limb, and provide the theoretical references for the protection of pedestrians in crashes.

Abstract:Objective To investigate the mechanical effect of stents with different links on the treatment of vertebral artery stenosis, and provide scientific guidelines for the design of stent structure and clinical procedure of stenting intervention. Methods Models of three kinds of stents with different types of links (namely, L-stent, V-stent and S-stent according to the shape of links) and vertebral artery with stenosis were established by using Pro/Engineering, then the same boundary conditions were exerted on the three models to simulate the stent deployed in the vertebral artery by finite element analysis using ABAQUS. Results Compared with L-stent and V-stent, S-stent had a better compliance, generating smaller stress in the arterial wall, causing relatively weak vascular straightening. Due to smaller stress and axial shortening generated in the stent strut, S-stent made less lesion on the arterial wall. Conclusions The therapeutic effect of S-stent is the best among the three kinds of stents, which could reduce in-stent-restenosis, and has good prospect in clinical application.

Abstract:Objective To simulate the stress generated by contact with the femur during the assembly of novel semi-hip prosthesis, and discuss the operating limits and adaptive prosthesis profile in clinic. Methods CT scans were conducted on the proximal end of the femur in a male volunteer of 60 years old as a physical model. By transferring the CT data to finite element modeling software, the physical model was simplified, meshed, materialized and assembled with the model of prosthesis to establish the three-dimensional finite element model. Surface to surface contact relationship between the femur and the prosthesis was also constructed by utilizing contact elements. Relative sliding distance and stress distribution were solved while simulating the process of assembling the prosthesis. Results Additional stress was generated on the sudden change area of the contact surface when the prosthesis was seated. The greatest contact pressure came from the changing section of the ridge of the prothesis, and the maximum assembly stress and sliding distance range increased nonlinearly along with the pushing distance. The increase rate of additional stress was enhanced significantly while Δz≥0.5 mm. Conclusions Compared with the prosthesis without ridge, the prosthesis with ridge can be easily seated and obtain mechanical stabilization. However, the relevant clinical operating limits should be obeyed to avoid generating excessive additional stress during the implantation of prosthesis, which may cause treatment failure due to the damage in bone cortex.

Abstract:Objective To investigate the hemodynamic factors in internal carotid arteries (ICA) with different shapes, and analyze the relationship between the arterial geometry and atherosclerotic stenosis to provide the hemodyanmic basis for the risk prediction and early diagnosis of ICA stenosis. Methods The flow field in the most two common types of ICAs, U and V-shaped ICA, were investigated by numerical simulation and particle image velocimetry (PIV) experiment under the condition of steady flow. Results At the upstream bend of ICA, the hemodynamic factors were monotonically associated with the curvature of the bend. As a result, the risk for stenosis here was smaller in the V-shaped ICA, as compared to U-shaped ICA. But at the downstream bend, such monotonic relationship didn’t exist due to the synergistic effect of the two bends. ConclusionsThe curvature of the artery is positively related to the risk for stenosis, but the synergistic effect of bends needs to be considered for studying arteries with the serial bends. The research on the synergistic effect may explain why the stenosis is frequently observed in arteries with multiple bends.

Abstract:Objective Modified B-T shunt (MBTS) and central shunt (CS) are two common surgical procedures for the treatment of tetralogy of fallot (TOF). The purpose is to analyze and compare the hemodynamic features of MBTS and CS. Methods 3D anatomy was reconstructed by medical images obtained from a patient with TOF, and two computational models were generated through virtual operations. A lumped parameter model was constructed to predict the post-operational boundary conditions. Computational fluid dynamics (CFD) was performed for the two models. Results A persistent pulmonary blood perfusion was observed in each model both during the systolic phase and diastolic phase, but the maximum velocities in the shunt were different for the two models. The pressure drop of the shunt in CS model was higher than that in MBTS model. The wall shear stress of the shunt in the MBTS model ranged unevenly from 0.025 to 340 Pa, while the wall shear stress in CS model ranged relatively evenly from 32.2 to 72.6 Pa. Conclusions Pulmonary artery blood was increased effectively for both options. The blood perfusion of right upper extremity was decreased in the MBTS model. More blood was directed into the pulmonary artery in CS model. Attention should be paid to the fact that the pressure gradient was large at the proximal anastomosis in both models in clinic. This study provides important theoretical references for surgeons to make choice from the surgery options in the treatment with TOF.

Abstract:Objective To reconstruct the 3D motion of the knee joint after total knee arthroplasty (TKA) and measure the kinematics and the articular contacts between the posterior stabilized TKAs. Methods Sixteen knees undergoing TKAs were scanned by fluoroscopy. An algorithm of automatic registration was developed to match the 3D TKA models and 2D images. The kinematical parameters and articular contact of the tibiofemoral joint was investigated. ResultsThe time for a single image was less than 30 seconds. The in-plane repeatability was within 0.4 mm and 0.5 degree. The application of the high-flex insert didn’t obviously improve the ability of the flexion and the internal/external tibial rotation. When the knee flexed, the contact point on the lateral side moved more posteriorly than that on the medial side. The contact between the post-cam and the femoral prosthesis occurred with the flexion at about 30 degrees. The average range of the contact was within 9 mm. Conclusions The 3D kinematics of the in vivo TKA knee joint was accurately measured by using 2D-3D automatic registration technique. The result can provide references for the biomechanical study of TKA knees and the improvement of TKA prosthesis design.

Abstract:Objective To establish a three-dimensional (3D) dynamic model of temporomandibular joint (TMJ) based on data collected from the TMJ movement with multi-level two-dimensional (2D) dynamic magnetic resonance imaging (MRI) and make biomechanical analysis. Methods GE Signa 1.5T TwinSpeed superconductive magnetic resonance scanner was used. TMJs of 2 asymptomatic male volunteers were chosen to be examined with MRI. All the images were imported to the Mimics software. 3D dynamic model of the TMJ was built, and the relationship between the magnitude of mouth opening and the disc transverse diameter was analyzed using linear fitting. Results The 3D dynamic model of TMJ was successfully established. The disc-condyle relationship and the dynamic morphological change of the TMJ disc were showed clearly in this model. The linear fitting equations were y=-0.03x+14.44 (R2=0.591) and y=-0.061x+13.48 (R2=0.306) from volunteers 1 and 2, respectively. A linear trend was observed regarding the relationship between mouth opening position and articular disc transverse diameter. The contact of the condyle surrounded by the TMJ disc varied inversely with the magnitude of mouth opening; the longitudinal diameter of TMJ disc changed along with the magnitude of mouth opening. In the process of mouth opening, the thickest longitudinal diameter of the joint disc was at the middle part of post-zone. The most remarkable changes of the longitudinal diameter of TMJ disc were found at the outer part of the post-zone and the inner part of the mid-zone. Conclusions The 3D dynamic model of TMJ was built successfully to observe the TMJ movement dynamically with 2D dynamic MRI. The model showed the disc-condyle relationship intuitively and precisely, and could be used as an alternative method to make up for the shortage of the 2D static MRI.

Abstract:Objective To study mechanical properties of the medical water-jet scalpel when cutting parenchyma such as liver and verify its tissue-selective cutting characteristic. Methods The tension mechanical properties of porcine liver parenchyma and its vessels with different sizes were determined. Porcine and Wistar rat liver tissues were cut with arteriovenous vessels well reserved, and pathological section of the rats were analyzed by HE staining to explain the experimental phenomena. Results When the working pressure was set at 3 MPa, the incising and separating on the right lobe of porcine liver by medical water-jet scalpel in this experiment were done with minimal vessels of 0.8 mm in diameter left. Pathological sections from ordinary scalpel and medical water-jet scalpel showed that the medical water-jet scalpel caused smaller tissue damage. Conclusions The medical water-jet scalpel could cut heterogeneity soft tissue with highly-selective characteristics, which may effectively avoid the existing “one size fits all” phenomenon caused by ordinary scalpel.

Abstract:Objective To investigate the cause of differences in confluent growth between hepatic(L02) and hepatoma carcinoma(HCCLM3) cells by comparing responses of the two cells to different substrate stiffness (0.5, 4 kPa and glass). MethodsThe real-time photomicrography, immunofluorescence staining, flow cytometry, and Western Blotting techniques were respectively employed to observe the morphological characteristics, the cytoskeleton conformation and the distribution of E-cad of confluent L02 and HCCLM3 cells on different substrates, and test the changes in expression of E-cad, Integrinβ1 and p-Src. Results (1) Confluent L02 cells displayed a round or cubic shape, while HCCLM3 cells showed a polygon shape. The morphology of HCCLM3 cells were spread and polarized more obviously than that of L02 cells. With the increase of substrate stiffness, the variation of L02 cells with time was smaller than that of HCCLM3 cells. (2) The cytoskeleton of confluent L02 cells showed a ring-like conformation under the cortex, and E-cad was located at the cell-cell contact sites. However, the ring-like cytoskeleton of HCCLM3 cells was incomplete and distributed radially along the basement, while E-cad was dispersed in cytoplasm. (3) As the substrate stiffness increased, expression of E-cadherin in both L02 and HCCLM3 cells was significantly decreased (P<0.01), while the level of p-Src and integrinβ1 was increased significantly, with greater changes in HCCLM3 cells than in L02 cells. Conclusions The assembling of cortical ring-like cytoskeleton was positively correlated with the location of E-cad at the cell-cell contact sites. The substrate stiffness showed a more obvious impact on the balanced regulation between cadherin and integrin mediated adhesion system of hepatocarcinoma cells than that of hepatic cells.

Abstract:Objective To develop an improved DIC (digital image correlation) algorithm suitable for measuring large ROM (range of motion) of the cervical spine, as traditional DIC algorithm is not capable of accurately measuring ROM of the cervical spine due to its large rotation angles. Methods An algorithm which allowed rotation of the subset window was proposed to achieve robust correlation matching in the measurement. A new iterative variable, which represented the orientation of the subset, was introduced and incorporated in the Newton-Raphson iteration method together with the position variables (x,y). By assigning an initial guess to these variables individually, the precise location and rotation angle could be determined in the deformed image. The precision of the proposed method was evaluated by translation and rotation experiments. ResultsThe translation experiment confirmed that the proposed method had the same accuracy as the traditional DIC, and the displacement measurement accuracy was within 0.5%. While the rotation experiment indicated that the proposed method could measure the deformation at any angles with precision less than 0.5°. The method was then applied to the measurement of ROM of cervical spine subjected to compressive loads and received good results. Conclusions Compared with the traditional DIC algorithm, the proposed method can achieve accurate measurement with large ROM for cervical spine tests with different loads, and provide an effective means for assessing the stability and physiological activities of cervical spine.

Abstract:Objective To establish the three-dimensional finite element model of the cannulated screws for fixing the femoral neck fracture, and investigate stress distributions on three cannulated screws as well as determine whether internal fixation by a modified cannulated screw can provide sufficient stiffness and strength for the fixation. Methods The 3D finite element model was internal-fixed at the angle of 127°with femoral shaft under the inverted triangle mode to simulate loading on single legged standing condition. Stresses on three screws (No 1: the underneath screw, No 2: the anterosuperior screw, No 3: the posterosuperior screw) were calculated at different Pauwels angle (50°, 60°, 70°, 80°), respectively. A bore was drilled in the screw with the largest stress to study the effect of bore size and bore direction on the femoral neck fracture model with screw fixation. Results The stresses of three screws increased with the Pauwels angle increasing and reached the maximum value at 80°. The maximum stresses on No.1, No.2 and No.3 screw were 304, 515 and 154 MPa, respectively. When the No 2 screw had an opening bore with 1 mm in diameter, and the direction of the bore was not between 150°and 195°, the stresses on three screws were all within the safe limits. Conclusions From the mechanical point of view, three screws are subject to different stresses. The cannulated screws with side bore have good biomechanical properties for fixing the femoral neck fracture with safety and reliability, which can provide advantages for accelerating fracture healing by injecting drugs through the central and side bore into the fracture side.

Abstract:Objective To measure the hip anatomic parameters and explore the differences between the hip fracture group and the normal group, analyze their effect on the incidence of hip fractures and fracture types by using computer aided design (CAD) and three-dimensional reconstruction technique. Methods Through CT scan images from the lower-extremity of hip fracture patient, the 3D anatomic model was established by Mimics10.01 software, and the 3D anatomic parameters of the normal proximal femur, namely femoral neck anteversion angle (FNAA), neck-shaft angle (NSA), femoral head diameter (FHD), length of femoral neck axis (LFNA) in the lower-extremity were measured. Results The averages of FNAA, NSA, FHD, LFNA in femoral neck fracture group were (7.9±4.6)°, (128.6±4.6)°, (46.0±4.6) mm, (47.1±5.1) mm, and those parameters in intertrochanteric fracture group were (15.5±6.8)°, (134.7±6.9)°, (45.3±3.6) mm, (46.7±3.4) mm. The FNAA and NSA in intertrochanteric fracture group were significantly larger than those in femoral neck fracture group regardless of gender (P<0.01). The FNAA and NSA in both fracture groups showed significant differences as compared with the normal group. ConclusionsThe risk of femoral intertrochanteric fracture will increase when the FNAA is larger than the normal range in Chinese, while the risk of femoral neck fracture will increase when the FNAA is smaller than the normal range in Chinese. The NSA of hip fracture patients was larger as compared with normal Chinese. The larger NSA will lead to a higher risk of femoral intertrochanteric fracture. There exist some differences in anatomic parameters of the proximal femur between the fracture group and the normal group, especially in the angle parameter. The femoral intertrochanteric fractures are more prone to occur in the older people, while the femoral neck fractures are more prone to occur in the younger people.

Abstract:Culturing cells on planar substrate in vitro is a conventional cell biology method. However, each type of physiological tissues has its specific three-dimensional micro-structure, which provides various micro environment to regulate such biological processes as cell proliferation and differentiation. To date, a growing body of researches on the impacts of substrate micro-topography on cellular responses has been documented in the literature. It is found that micro-topograhical substrate can manipulate cell spreading, migrating, orientating, cytoskeleton remodeling, and stem cell differentiation, which are crucial to ex vivo tissue construction and surface modification of medical implanting materials. This review discusses the recent progresses of the effects of substrate micro-topography on cellular responses and the underlying mechanisms of mechano-biological coupling.

Abstract:Mechanical stimulation plays key roles in regulating the development and function of cells. With the rapid progress of space life science and space biotechnology, the biological behaviors of cells and the involved molecular mechanisms in space have gradually become a hot topic and frontier of the space biology. Bone marrow mesenchymal stem cells (MSCs) plays an important part in clinical cytotherapy and wound healing, due to its self renewal and multi-lineage differentiation potentials. In recent years, researchers have made significant achievements in biological behaviors of cells responding to microgravity environment by means of space simulation technology. In this review, some commonly used microgravity simulation devices were introduced, and changes in MSCs proliferation and differentiation under microgravity and its related molecular mechanisms were briefly summarized, so as to provide theoretical references for prevention and treatment of microgravity related diseases.