Abstract:Mechanical loosening of orthopaedic implants can be predicted by measuring the progressive micromotion of the implant with respect to the bone in the first two years after surgery.The most accurate Roentgen technique for three-dimensional assessment of micromotion is Roentgen Stereophotogrammetric Analysis(RSA).The reported accuracy of RSA ranges between 0.05 and 0.5 mm for translations and between 0.15 and 1.15 deg for rotations.RSA is used to study the effect on prosthetic fixation due to changes in implant design,addition of coatings,or new bone cements.The advantages of RSA are that small patient groups(i.e.25 patients) and short-term(i.e.2 years) clinical studies are in general sufficient to predict the likelihood of long-term(i.e.10 years) mechanical loosening of the prosthesis.This makes RSA an important measurement tool to study new developments in prosthetic design in order to prevent large patient groups from being exposed to potentially inferior designs.In this paper,the basics of the RSA technique will be explained,and some examples of clinical RSA studies will be presented to illustrate the clinical relevance of RSA.

Abstract:Objective To evaluate the disparity of compressive biomechanical properties and the histological structures between the repaired cartilage and the normal ones were examine 12 weeks after autologous osteochondral transplantation.Methods 18 New Zealand white rabbits were selected and a full-thickness cylindrical osteochondral defect was made on the right knee femoral trochlea of each by using Osteochondral Autograft Transfer System(OATS).The defect was repaired with the osteochondral plug with the same diameter and depth taken from the proximal femoral trochlea using the OATS.The contralateral femoral trochlea was treated as normal control.The repaired cartilage and the contralateral,normal cartilage were evaluated in 12 weeks postoperative.The cartilage specimens of 12 rabbits were tested under unconfined compression,the linear elastic model and the linear biphasic model were applied and Young’s modulus the equilibrium compressive modulus the stress relaxation time and creep time were obtained.The paired t test was used to estimate the disparity between the repaired cartilage and the normal control.The other cartilage specimens were stained with hematoxylin and eorin、toluidine blue to examine the histological structure under light microscopy.Results The biomechanical properties of two groups did not show statistically difference(P<0.001).The repaired cartilaginous structures under light microscopy were the same as the normal cartilage.Conclusions The short-term effects of repaired cartilage employing OATS are satisfying,but the long-term results need further more investigating.

Abstract:Objective To establish a three-dimensional finite element model of knee joint with tibial and femoral tunnels as a foundation for finite element analysis in anterior cruciate ligament reconstruction .Methods Based on the MRI images,the 3D finite element model of a healthy knee joint was constructed by using the Geomagic and ANSYS 9.0 software.Results The established 3D finite element model consisted of tibia,femur,cartilage of tibia and femur,tibial tunel,femoral tunnel and the ligaments surrounding the knees.The ideal geometry shape met the need of finite element analysis.Conclusion It is a reliable way to construct knee 3D finite element model with MRI images.The finite element model can reflect the geometry structure of knee joint and bone tunnels vividly.

Abstract:Objective Design a new kind of titanium alloy artificial lumbar intervertebral disc and evaluate its biomechanical features.Methods The new designed artificial lumbar intervertebral disc with ball and socket joint was made of new titanium alloy with low stiffness(50GPa).The tests for compressive stiffness,torsional stiffness and fatigue strength of the artificial disc were made by the material testing machine.Results The new artificial lumbar intervertebral disc has had the functions for flexion,extension,lateral bending when tested with the mechanical tests to show its compressive stiffness as 50～66.7GPa,which is 1/3 of stainless steel.And its torsion stiffness is 388.54Nm/°.No obvious damage appeared after 1 07 fatigue strength tests.Compared with the stiffness before testing,it showed that 1,2,5 and 10 million cycles made no significant difference.Conclusion The new artificial lumbar intervertebral disc showed similar mechanical characteristics to that of the normal human lumbar disc.

Abstract:Objectives To evaluate the effect of sagittal fixation angle on the stresses of adjacent segments in lumbar fusion in vitro.Methods Lumbar spine(L1-S2) specimens from nine fresh human cadavers were used.After intact tests of the original normal spines,fixations with three different sagittal angles(1) in situ(lordosis 10 degrees),(2) kyphotic(kyphosis 5 degrees) and(3) hyper-lordotic(lordosis 25 degrees) at L3,4 and 5 were randomly conducted using pedicle screws on each specimen.Subsequently,biomechanical tests were performed under flexion,extension and lateral bending modes.Stresses of the facet joints and intervertebral disks at L2/3 and L5/S1 were measured and compared.Results In flexion tests,all the three fixation strategies resulted in higher stresses within the adjacent segments than that of the intact spine,the highest being the kyphotic fixation group.In extension tests,stresses of the kyphotic group were significantly higher than that of the other two fixation groups.However,there was no statistical difference among the in situ and hyper-lordotic fixation group.The results of bilateral bending were similar to that in extension.Conclusions Spinal fixation can cause stress increase within adjacent segments.Lumbar fixations with abnormal angles may further deteriorate the associated biomechanical condition.Therefore,for lumbar reconstruction,it is crucial to keep the lumbar alignment to its normal orientation.

Abstract:Objective To design and optimize the artificial cervical joint complexity.Methods A three-dimension model of the artificial cervical joint complexity was constructed;we meshed the model based on the finite element method.The feature dimension of bone graft cavity in the model was set in a specified varied range.Under the physical load,we operated a simulation to optimize the feature dimension.We analyzed the stress,strain,and had an evaluation on the systematic safety factor.Result The simulation showed that the maximum stress appeared in the central area of the inferior of bone graft cavity,the minimum safety factor appeared in the contact area between the superior disc implant and the pad.As the feature dimension got bigger,the maximum strain increased,the graph of minimum safety factor is a Para-curve.Conclusion Taking the consideration of the systematic constancy and bone graft cavity,the optimal feature dimension of the bone graft cavity is supposed to be 3mm,because the maximum stress becomes the smallest and the systematic safety factor becomes the biggest when the feature dimension is 3mm.

Abstract:Objective To measure and compare the stresses along the screws in three-segment and two-segment posterior internal fixation in spondylolishesis.Method Six fresh samples of human lumbar vertebras were used in the study.The spondylolishesis model was made by Panjabi method,and was placed with the universal spine system of SINO.By strain measurement and biomechanical measurement,the samples were tested in 5 different directions with INSTRON 5567.Stress along the screws for two-segment(group A) and three-segment(group B) were measured respectively.Result The draw-screw in group A shared more stress than that in group B(P<0.05);The fixed-screw in group B shared more stress than in group A(P<0.05)?.Conclusion The three-segment internal fixation can effectively decrease the stress along the draw-screw,and depress the probability of breakage of the screw due to the system fatigue.

Abstract:Objective The purpose of this experimental study was to find the important factors affecting the stability of cannulated cancellous screws in femoral head and provide experimental basis in clinical use on femoral neck fracture using internal fixation with cannulated cancellous screws.Methods 31 femoral heads were from the patients of femoral neck fracture,then cannulated cancellous screws were embedded into them by the method for the treatment of femoral neck fracture.We recorded the ages of the patients,the diameters of the femoral heads,the BMDs of the femoral head,the distances from the tips of the screws to the articular surfaces of femoral heads.we fixed up femoral head and screw extremity into the mechanical experimental apparatus and carried out the tests.We got the stress-strain curves and the maximal pullout stresses of the screws.The data were analysed by multiple regression of SPSS for windows 11.5.Results The difference of the femoral head's BMDs and the depths of the screws which were embedded into the femoral heads brought about the difference of the maximal pullout stresses.By multiple regression,we found that the maximal pullout stresses of the screws were correlated with the femoral head's BMDs and the distances from the tips of the screws to the articular surfaces of femoral heads,the maximal stresses positively were correlated with the fore(P=0.002) and negatively correlated with the latter(P=0).Conclusions We should choose the higher BMD's patients of femoral neck fracture to treat them with cannulated cancellous screws and embed cannulated screws into the special depth of femoral head.

Abstract:Objective To study the asymmetry of velocity profile under steady flow condition in the curved common carotid artery(CCA) in vitro.Methods The PIV is used to measure velocity profiles on vertical and horizontal planes of CCA in different localities under physiological average,peak and limited Reynolds numbers of CCA models of 1:20 and 1:60 curvatures.Result The skewed parabolic profile is observed in CCA under 1:60 curvature and physiological average Reynolds number.As curvature and Reynolds number increase,the middle of horizontal profile appears sunken and the vertical profile is M-shaped.There are different profile shapes in different localities along the curved pipe.Conclusion The experimental data were provided for the asymmetric inlet velocity profile condition of carotid bifurcation,and for understanding the changes of velocity profiles shapes along with Reynolds numbers,curvature and localities of the curved pipe.

Abstract:Objective check if mechanical properties of Nano-apatite(HA)/ Poly(D,L-lactide)(PDLLA) biocomposite is improved by solution-coblending and hot-pressing techniques.Methods HA particles and PDLLA polymer,as two basic compositions of the biocomposite,were firstly dispersed in dimethyl formamide(DMF) dispersant,then the DMF was by inches cleaned out by intensively stirring in 45 oC.The resultant mixture including HA and PDLLA was fallen to pieces,and then pressed at 100oC in hot-pressing machine,finally,thin film of HA/PDLLA composite biomaterials was prepared.Results These results from Transmission Electron Microscopy(TEM) observation showed that HA well-proportioned distribution in PDLLA-matrix bio-composite was obvious with HA contents rising,which suggested that solution co-blending method by DMF dispersant was beneficial to HA decentralization in PDLLA matrix and exhibited symmetrical microstructure in composite films.Mechanical property testing illuminated that tensile modulus,yield ...更多stress and tensile stress of HA/PDLLA composite were improved,which implied that the bonding strength of interface between HA and PDLLA was enhanced.Conclusion These results suggested that technical route of composite preparation employed by us helped to improve mechanical properties of HA/PDLLA bio-composite

Abstract:Objective To investigate and evaluate the biomechanical property of adult excised porcine trachea in order to provide the experimental methods and evidence for biomedical engineering artificial trachea.Methods TY8000 servo-handle tension test machine was used to measure the biomechanical index such as bending stiffness,radial pedestal force and stress-straining of the excised porcine trachea.The residual stress and bursting strength were also evaluated.Results The results showed that residual stress was remained in the adult excised porcine trachea.The force of radial pedestal was measured to be about 10N when the diameter of trachea was compressed to 50%.The bursting strength from pharyngeal portion to eminence of the trachea gradually dropped off with the data of 180mmHg at the pharyngeal portion while 110 mmHg at the eminence.The curve of stress-straining was described to be 0.296N～0.131N、0.254N～0.150N,respectively according to the date.Conclusion The residual stress was remained in the excised porcine trachea and the membrane of the porcine trachea will disrupt as the endospore pressure increases.It shows that the excised porcine trachea has perfect radial pedestal force,bending and elongation properties.

Abstract:Objective To study the effect of different high-heel shoes on the gait of young females and provide some theoretical basis in quantity scientifically the design of the high-heel shoes.Methods Normal digital video camera and footscanUSB system were combined and the gaits of 10 young women(average age is 19.2 .42) walking on the flat ground with normal speed with barefoot and wearing four pairs of varying high-heel shoes were tested in order to make comparative analysis on their kinematic and kinetic parameters.Results(1) when the heel height of shoes increases,the stride velocity,the stride length,the stride frequency and the joint angles of the lower limb grow smaller in order to obtain the safe and stable gait;(2) the higher the shoe heel,the larger Percentage of support phase and double support phase accounting for gait cycle,the smaller Percentage of swing accounting for gait cycle;(3) the value of the peak force of forefoot,the percentage of impulse on the forefoot and mid-foot become larger,when the subjects walk wearing the higher heel shoes.(4) The thickness of shoes heel also influences the gait characteristics.Conclusion Walking with the high-heel shoes could cause the foot fatigue,pain and injuries easily or the abnormality of foot growth.

Abstract:Bone can adapt to external mechanical loading,forming or resorbing bone tissue at the specific site in order to increase the efficiency of its mechanical function.Additionally,bone has ability to repair micro-cracks timely,which occur as a result of daily loading activities,to prevent fracture and prolong bone's life.This is termed the Bone Functional Adaptation.Compared to traditional experiments,computational simulations embody many advantages in controllable,feasibility and predictability,being paid extensive attention.Because of the significance of theoretics of mechanobiology and practice of clinical medicine,the purpose of this article is to review the progress that has been made in simulating the mechanisms of bone functional adaptation.

Abstract:Hemodynamics is closely associated with arterial diseases.The studies on blood flow in arteries are very significant to explain and find the reasons of the diseases from the viewpoint of mechanics.Fluid-structure interaction in arteries is a hot and difficult point in hemodynamics.The existent problems are pointed out when the advances in the field are reviewed.In addition,according to the requirement of clinical diagnosis and treatment,the problems that need solving in the future and the direction of the corresponding numerical calculation are proposed.

Abstract:Total hip arthroplasty(THA) has come into the clinical practice for more than 30 years.Because of acetabulum has more complex structure than that of the femur,biomechanical and anatomical studies on THA have been long time focused on the femoral component.More recently,acetabular component loosing has been identified as the important limiting factor affected THA.The biomechanics and anatomy of acetabulum have become to be investigated using various advanced methods.This paper has reviewed the recently advanced researches by focusing on the biomechanics and anatomy of acetabulum.