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Abstract:Objective To evaluate the biomechanical properties of 3D printed individualized titanium alloy pelvic prosthesis in static and gait states by the method of finite element analysis. Methods Three patients with different types of pelvic tumors were treated by hemi-pelvic arthroplasty with resection of hemi-pelvis. CT and MRI were performed before the surgery, and the corresponding individualized titanium alloy pelvic prostheses were designed. The pelvic models were reconstructed with 3D reconstruction technique, and then assembled with the individualized pelvic prostheses. The human skeletal muscle model was established by AnyBody software to perform gait dynamics analysis. The stress distribution and stress concentration areas of 3 reconstructed pelvic models in static and gait states were obtained by ABAQUS. Results Under both static and gait conditions, the maximum stress of the 3 pelvic prostheses was smaller than the yield strength of the titanium alloy. The pelvic ring of the reconstructed pelvis could meet the rule of stress conduction. The patients’ daily life returned to normal condition after the surgery. Conclusions The effect of 3D prosthetic titanium prosthesis on recovery of pelvic ring is satisfactory, and its effectiveness and stability can meet the requirement of human biomechanics. The analytic results can provide references for clinicians and prosthesis designers.

Abstract:Objective To perform finite element analysis on a type of newly designed total knee prosthesis, and investigate the influence from changing twist angle of the lateral condyle surface on mechanical environment of the knee joint. Methods Based on CT measurement data from a volunteer, 3 artificial knee prostheses with the same medial condyle were established. In Model 1, the twist angle of lateral condyle surface was 0°, while 10° and 20° in Model 2 and Model 3, respectively. The prosthesis models were imported into finite element software and applied with gait cycle data to simulate the motion of knee prosthesis during the gait cycle. The simulated stress results in the knee joint were then compared with the calculated results, which were obtained from theoretical formula of contact mechanics. Results The maximum stress of 3 models appeared at 13% of the gait cycle, when the axial force (2.6 kN) was also the maximum. The maximum stresses of medial and lateral condyle in Model 1, Model 2 and Model 3 were 35.5 and 30.6 MPa, 38.4 and 32.6 MPa, 38.3 and 43.1 MPa, respectively. The stress curves of Model 2 and Model 3 during the gait cycle were relatively smooth compared with those of Model 1. The simulated stress trend was basically similar to the theoretical calculation, except at a few moments in the gait cycle. Conclusions The mechanical environment of the total knee prosthesis can be improved by twist angle of the lateral condyle surface. This newly designed prosthesis can preserve implants from abrupt change of the stress during the gait cycle and prolong the service life of prostheses.

Abstract:Objective To construct a three-dimensional (3D) solid model of the cortical bone including osteons, verify the stress concentration effect of osteons, simulate and predict the stress concentration location under fatigue using finite element analysis (FEA). Methods The 3D solid model of the cortical bone including osteons was constructed in Pro/E wildfire 5.0, and local stress and strain distributions in the cortical bone under different axial compression were calculated and analyzed in ANSYS 12.0. Fatigue simulation on the selected locations was conducted to evaluate fatigue status of the model subjected to different fatigue loading intensities. Results Obvious stress concentration at the junction of osteon and the interstitical bone appeared under axial compressive loads, and the percentage of pathological local strain in the cortical bone increased with the axial compression increasing. Fatigue simulation on the selected locations demonstrated that bone fatigue risk during physiological or daily activities was very low, while a high fatigue or fracture risk might occur during high-intensity exercises or training. Conclusions The 3D solid model of the cortical bone including osteons is successfully established, the stress concentration effect of osteons is verified, and the location of bone fatigue damage under strenuous exercise and its risk are predicted. These experimental results can provide references for training management and athletic fatigue damage prevention in military recruits and long distance running athletes.

Abstract:Objective To investigate the effect of different calcification patterns on the outcome of transcatheter aortic valve implantation (TAVI) by the finite element method. Methods Three calcified human aortic root models (coaptation line calcification model, attachment line calcification model and circular calcification model) were developed according to the location of calcified plaques on the aortic valve leaflets. The processes of self-expanding transcatheter aortic valve implanted into the 3 calcified models were simulated by ABAQUS software. The effects of different calcification patterns on the aortic root stresses, valve frame distortions and paravalvular gaps were analyzed. Results Circular calcification model had the largest maximum principal stress on calcified plaques (18.42 MPa), which might result in a higher risk of stroke after implantation; the circular calcification model also had the greatest distortion of the valve frame, which might lead to worse prosthetic durability; the paravalvular gaps area of the attachment line calcification model was 37.2 mm2, which was more than twice that of the other 2 models, causing more serious paravalvular regurgitation. Conclusions Different aortic valve calcification patterns are related to aortic root stresses, valve frame distortions and paravalvular gaps after TAVI, which will have an impact on postoperative complications and prothesis durability. The research findings provide references for the prediction of clinical outcome after TAVI.

Abstract:Objective To study the dynamic growth of adsorption films on solid surfaces in point contacts with aqueous protein aqueous solutions and investigate the dominating factors. Methods The formation of the adsorption films within a ball-on-disc contact was measured using optical interference technique. The effects of impact loads, impact times and surface properties of the materials on the adsorption of BSA aqueous solution were also studied. Results Under dynamic conditions, the thickness of the adsorption film was much higher than that under static condition. The adsorption film was growing with increasing impact times and finally the stable thickness could be achieved. Small loads and hydrophobic materials were favorable for the growth of the adsorption film. The BSA adsorption film was easy to grow on the steel surface, but on the ceramic surface the adsorption film thickness was low. Conclusions The research about adsorbed lubricating films evolution of protein aqueous solution under impact loads is of clinical significance for treating and preventing of artificial prosthesis.

Abstract:Objective To investigate the variations of elastic modulus and hardness of human dentin with aging and location. Methods The non-carious third molars were collected and divided into youth group, middle-aged group and elderly group. Nanoidentation test was conducted on the dentin specimens from multiple regions to test their mechanical properties. Results The elastic modulus and hardness in outer and middle dentin were greater than those in inner dentin; the elastic modulus and hardness increased with the aging in each region of the dentin. Conclusions The dentin shows a gradient mechanical property. The stiffness and hardness in middle and outer dentin are greater than those in inner dentin. The deformation resistance in middle and outer dentin is stronger than that in inner dentin. Meanwhile, elastic modulus and hardness of the dentin increase with the aging.

Abstract:Objective To study the effect of lateral wedge insoles with different stiffness on the knee adduction moment (KAM) under walking condition. Methods The gait of 15 healthy males wearing lateral wedge insoles with different stiffness was tested. The kinetics and kinematics data were collected by optical motion capture system and ground reaction force platform. The KAM and its peak values were calculated by Visual 3D software. The differences in peak KAM under 3 walking conditions (shoes only, shoes with softer or harder lateral wedge insoles) were analyzed. Results Compared with walking with the softer lateral wedge insoles, walking with the harder lateral wedge insoles could reduce the 1st and 2nd peak KAM by 9.3% and 9.7%, respectively, with significant statistic differences. Conclusions Increasing some stiffness of lateral wedge insoles can further reduce the pressure and wear on medial compartment of the knee joint, which may relieve the symptom of knee osteoarthritis.

Abstract:Objective To explore the effects of intensive therapy program on gross motor function of children with spastic cerebral palsy. Methods Thirty 3-15 year old children with spastic cerebral palsy and level I-III in gross motor function classification system (GMFCS) were randomly divide into 2 groups. The trial group adopted intensive therapy program for treatment, including functional dynamic suit and universal exercise unit combined with functional movement training. The control group adopted core stability training for treatment. Children in two groups took a 1-month training program for 3 hours per day and 5 days per week. The pediatric evaluation of gross motor function measure (GMFM-66) and peabody developmental motor scale (PDMS-2) were administered before and after treatment. Results The scores of GMFM-66 as well as the stationary and locomotion scores of PDMS-2 in both groups showed significant differences within group (P<0.01) after treatment. For the scores of GMFM and PDMS-2 between two groups, no significant differences were found. Conclusions The intensive therapy program can improve the gross motor function of children with spastic cerebral palsy and gain the same effects as core stability training, which can provide a novel and effective intervention for children with cerebral palsy.

Abstract:Objective To study the intrinsic relationship between hemiplegic gait features and abnormal muscle strength of lower limbs, so as to elucidate the muscle strength causes of hemiplegic gait and provide recommendations for its clinical treatment. Methods Models of hemiplegic gait and normal gait were established for simulation, and the validity of the models was verified by comparing the simulation model with measured data of the normal gait. The differences in kinetic data, ground reaction force (GRF) and muscle force between the two models were analyzed to explore the different dynamic characteristic of hemiplegic gait and normal gait. Results The complex correlation coefficient between LifeMOD simulation results and measured data was 0.922, indicating that the established dynamic model was reasonable and effective. Hemiplegic patient with low tibialis anterior muscle strength led to ankle dorsiflexion inadequacy during initial ground period, and low gastrocnemius muscle could not achieve the promoting effect from ground during preswing period. Conclusions The strength weakness of tibialis anterior muscle and gastrocnemius are the main reasons for foot drooping and other hemiplegic gait characteristics. LifeMOD modeling and simulation can assist the diagnosis of abnormal muscle strength in hemiplegia patients.

Abstract:Objective To compare the differences in gait characteristics and stability of women walking with or without sports bra. Methods Twelve women with C cup breast were required to walk on the treadmill (at the speed of 6 km/h) with and without sports bras, respectively. Their gait parameters were collected by using Qualisys Track Manager high-speed infrared motion capture system. Results Compared with the bare-breasted condition, the maximum and minimum angles of the upper trunk were significantly smaller when subjects wearing the sports bra, the range of trunk flexion angles and trunk torsion angles were also relatively smaller, and the standard deviation of hip flexion angles during 10 gait cycles was obviously smaller. However, no differences were found in stride frequency between two breast support conditions. Conclusions Different breast support conditions have a significant influence on the upper trunk angle, trunk flexion angle and trunk torsion angle. Walking without bra will increase the range of trunk angle and deteriorate the walking stability. The stride frequencies under different breast support conditions have individual differences.

Abstract:Objective To explore the activate process of lymphocyte function-associated antigen 1 (LFA-1) triggered by chemokine under shear stresses. Methods Jurkat cells were perfused over ICAM-1 in the parallel-plate flow under 10-30 mPa shear stresses. The effects of soluble and immobilized Chemokines on transient adhesion behavior of Jurkat cells were observed and analyzed to obtain their tether characteristics. Results The immobilized CXCL12 could mediate brief tether (0.13-0.2 s) of Jurkat cells under flow. Only immobilized CXCL12 could effectively activate LFA-1 on Jurkat cells to bind ICAM-1, and then enhance cell adhesion fraction and greatly prolong the tether time (0.8-1.2 s). Two distinct activation states of LFA-1/ICAM-1 were reflected by their dissociation rate k1 (1.09-1.24 s-1) and k2 (0.28-0.7 s-1), respectively. The shear stress would affect the transient adhesion behavior of cells through regulation of k2 and β (the contribution ratio of high affinity to total tether time). Conclusions Shear stress can rapidly trigger LFA-1 activation in 0.2 s through G protein coupled receptors induced by chemokine CXCL12, and further regulate the whole adhesion process of leukocyte. These research findings will contribute to further understanding the integrin activation mechanism of chemokine-force cooperative regulation.

Abstract:Objective To reveal the biomechanical mechanism of suspension exercise therapy (SET) for treating cervical spondylosis. Methods From August 2015 to December 2016, 72 patients with cervical spondylosis were divided into experimental group (SET treatment group) and control group (traction treatment group) based on simple random sampling methods. For experimental group: 9 males and 27 females, the average age (45.19±10.09) years old, the average disease course (24.94±18.07) months. For control group: 11 males and 25 females, the average age (44.08±8.88) years old, the average disease course (22.17±14.96) months. The mechanical properties of neck muscles before treatment and at the end of disease course were tested by Biodex Ⅲ Isokinetic Testing System. Results Before treatment, there were no significant differences in the peak torque (PT), average power (AP), peak torque of flexor/extensor peak torque ratio (F/E) for both groups; after treatment, PT, AP, F/E in experimental group was improved compared with those in control group (P<0.05). Significant differences in PT, AP, F/E were found for experimental group before and after SET treatment(P<0.05). There were no significant differences in visual analogue scale (VAS) of neck pain for both groups before treatment (P＞0.05)，while the VAS of experimental group was better than that of control group(P<0.05). Significant differences in the VAS were found for experimental group before and after SET treatment(P<0.05). Conclusion sSET can improve the contraction forces and work efficiency of neck muscles for patients with cervical spondylosis, as well as the coordination ability of flexors and extensors muscles, which will contribute to restoring biomechanical properties of the patients with cervical spodylosis.

Abstract:The finite element method (FEM) is a technology for numerical analysis which based on the development of the electronic computer, and also a more advanced biomechanical research method. Early FEM was applied in the fields of engineering science and technology. In recent years, FEM has been widely used for brain research in biomedical engineering. With the rapid development of traffic and transportation, the high incident of craniocerebral injury has become a serious threat to human health year by year. The biomechanical mechanism of craniocerebral injury can be well researched by establishing the finite element model of human head. In this review, establishment, development and application of human head finite element model are summarized, and the future research direction is discussed as well.

Abstract:High flexion squat is extremely common in the daily activities of Asian countries and certain occupations. In this paper, different types of deep squats and their motion characteristics were summarized, and recent research progress of squat biomechanics was reviewed. Different research methods on squats such as in vitro experiment, in vivo test and computer simulation were also classified and represented. Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training, prevention of sports risks as well as provide some references for optimization of knee prosthesis design.