国内全髋关节置换磨损测试及数值模拟研究进展

髋关节假体磨损及磨损颗粒所导致的无菌性松动是髋关节置换失败的重要原因. 本文作者对国内髋关节磨损研究时采用的运动学与力学曲线以及针对国人测绘的相应曲线进行了差异性分析,并对国内发表的全髋关节磨损体外模拟机测试试验及结果,数值模拟模型及结果进行了总结、对比和分析. 结果显示:1) 国人测绘的运动学与力学曲线不能直接用于全髋关节磨损评估的加载条件,国内关节力的测量方法仍有待进一步改进;2) 国内体外磨损测试的研究结论与国外发表的结论相似,但不同机构间的测试结果存在一定差异;3) 国内髋关节磨损仿真研究还处于起步阶段,仿真计算得到的磨损率普遍低于体外测试结果. 因此,建立基于国人行为力学的磨损评估标准、对磨损模型进行合理优化并采用有限元和骨肌多体动力学相耦合的分析方法对髋关节假体临床前磨损性能进行评估是未来的研究方向.      

人工膝关节置换中的生物力学研究进展

膝关节是人全身最大最复杂的关节, 它的任何一个主要组成部分的损坏都会引起膝关 节的反常运动, 久之软骨和半月板发生磨损、变性而形成骨性关节病, 从而影响人的日常生 活. 通常采用的方法是进行膝关节矫形或置换, 对严重病变的膝关节, 则采用全膝置换手术. 随着人工膝关节置换成为非常普遍的外科手术, 与膝关节假体相关的研究也越来越多的被人 所关注. 从生物力学角度对人工膝关节假体的类型和材料、假体生物力学性能的理论和 实验研究、骨重建的理论模型、骨整合的理论和实验、与理论和实验相关的有限元分析模型 等几个主要方面进行了详尽的综述. 同时, 指出了人工膝关节置换和目前研究中存在的问题, 并对其未来的发展方向进行了一定的预测.     

股骨纵向受压时的应力分布特征分析

股骨是支撑人体的重要组成部分,其纵向受压是主要的外力作用形式.过大的荷载、意外的冲击、疲劳等可能造成股骨的断裂损伤,股骨颈开裂与折断是一种典型、高发的损伤形式,此时需要用人工假体代替损坏的部分股骨.为使假体与股骨结合性能接近于原股骨,必需研究掌握股骨的应力分布特征.股骨特别是两端因几何构造的复杂性,相应的应力情况也比较复杂.因受活体股骨及其实验技术的限制,有限元数值计算分析成为一种普遍采用的方法.但股骨上端部构造复杂、尺寸相对较小,往往缺乏可靠的计算结果,且股骨颈附近的有效测试数据相对较少.因此,需要进行全股骨纵向受压的应力分布特征特别是股骨颈附近应力特征的进一步研究.此外,假体植入后股骨的应力分布变化与假体的无菌性松动是一个切实的重要问题.论文基于股骨标本和假体植入鲜股骨纵向受压的多点应力测量结果,进行其有限元建模并计算分析.先基于股骨的CT扫描数据,利用MIMICS软件重建股骨的三维几何精确模型,再转入ANSYS软件划分单元,计算得到全股骨的应力分布结果,说明其分布特征及关键点的应力,并与实验结果比较说明结果的可靠性.然后,考虑股骨颈断裂损伤后的生物型金属假体植入情况,基于假体松动前的股骨实验结果,对于假体与股骨结合体计算分析其应力分布,说明假体植入对于股骨干应力分布的影响、及假体松动与应力遮挡现象.     

损伤因素对单层平面索网静力性能影响研究：有限元分析与试验验证

运用通用有限元软件ANSYS建立三维有限元模型,对横索与竖索连接节点失效、索预应力损失和锚固端失效这三种损伤因素的不同损伤工况下,单层平面索网结构的受力性能进行了非线性有限元分析,并与相应的试验结果进行了全面对比分析。结果表明：本文的有限元模型能够准确地分析计算上述三种损伤因素对单层平面索网结构受力性能的影响,包括结构...     

Crowe IV型发育性髋关节发育不良在全髋关节置换术中横行截骨最佳位置的有限元分析

Crowe IV型髋关节发育不良（developmental dysplasia of the hip,DDH）的全髋关节置换术（total hip arthroplasty, THA）中，多数患者需要截骨保证复位，目前横行截骨是运用最广泛的术式，但截骨的最佳高度仍存在争议。本文通过建立Crowe IV型DDH患者的有限元模型，分析了在不同载荷下，不同截骨高度模型的应力分布与位移情况。结果表明：在多项指标下，小转子下0 cm的截骨高度均表现出了较优性能。在不影响假体安放和断端对合情况允许的情况下，推荐在手术中使用0 cm的截骨高度。     

摩擦热对髋关节假体服役寿命影响机制的研究进展

髋关节假体服役过程中会产生高于天然关节的摩擦热,引起假体与滑液温度上升进而改变髋关节假体的松动失效机制.研究摩擦热作用下假体摩擦特性、滑液润滑特性及相关细胞生物学特性,对提高假体体内使用寿命具有重要意义.本文中重点阐述摩擦热对髋关节假体服役寿命影响机制的研究进展,并对其发展趋势进行展望.     

基于子模型法的大跨斜拉桥扁平钢箱梁应力分析

为了掌握扁平流线型钢箱梁应力水平及其分布,本文以润扬斜拉桥为工程背景,建立了整体有限元模型和局部有限元子模型。在对整体有限元模型进行分析的基础上,应用子模型法对润扬斜拉桥主梁各关键截面进行了有限元受力分析,运用试验结果验证了有限元结果的可靠性。在此基础上研究了主梁各关键截面的应力水平及其分布特点,并进一步总结了试验荷载下润扬斜拉桥扁平钢箱梁的受力特点。结果表明了子模型法应用于扁平钢箱梁局部应力分析的有效性和可靠性,其结果可为润扬斜拉桥扁平钢箱梁的安全监测提供科学依据。     

福建省第十届大学生结构设计竞赛结构优化分析1)

以增加结构模型承载自重比与实现结构鲁棒性为目标,通过力学计算、有限元分析和实体模型试验,从材料性质、结构选型、杆件截面设计和制作工艺等方面,对结构模型进行了优化分析,提出了准确掌握材料性能和结构受力特点是结构模型优化的前提条件。     

股骨形态及应力应变的三维有限元分析

建立了一个针对高危女性人群股骨结构的三维有限元模型,分析了运动荷载作用下此类股骨的应力和应变分布以及股骨破坏的可能部位.结果表明:运动荷载使股骨产生较大的横向位移和弯曲变形;股骨颈处的应力和应变最大,容易在股骨颈处以及大转子与股骨干的连接部位附近发生破坏.模拟结果为研制适用于此类人群的高性能人工股骨提供了参考.     

钢板-混凝土组合加固钢筋混凝土梁的非线性有限元分析

以10根采用钢板-混凝土组合加固技术加固的钢筋混凝土梁的试验为基础,建立了钢板-混凝土组合加固钢筋混凝土梁的非线性有限元模型.沿用了钢板-混凝土组合梁有限元分析中栓钉的荷载-滑移曲线及断裂模型,提出了新老混凝土界面的剪切-滑移模型,可以较好地模拟界面受力性能.采用有限元软件ABAQUS,模拟了一次加固、不同损伤加固及持载加固等加载情况下加固构件受力全过程和受弯破坏以及新老混凝土剥离破坏等破坏形态下加固试件的受力性能.在验证了有限元模型的准确性后,分析了钢板厚度、加固部分高度及长度等参数对加固构件承载能力及刚度的影响.最后提出了几点对钢板-混凝土组合加固RC梁的设计建议.     

Plated and Intact Femur Strains in Fracture Fixation Using Fiber Bragg Gratings and Strain Gauges

This paper presents an experimental methodology to determine plated and intact femur strains using fiber Bragg gratings and strain gauges. A plated and an intact synthetic femur were used and loaded under a simplistic static load of 600 N. A stainless steel (316L) plate was used to fixate a simulated 45° fracture on one femur. Strains were recoded at the same sites on both femurs. Strain shielding is shown to be more pronounced at the distal region of the plated femur. The experimental methodology based on fiber Bragg grating sensors is a novel approach to assess bone plate strains, which could also be used to obtain biologic tissue and implant surface strains in locations where conventional strain gauge use is not technically feasible.     

Nonlinear vibration and dynamics of ceramic on ceramic artificial hip joints: a spatial multibody modelling

The present study investigates nonlinear vibration and dynamic behaviour of a ceramic-on-ceramic hip implant. The aim of this research is to firstly gain a better understanding of hip squeaking and vibration and secondly to investigate the effect of friction on contact point path during normal gait. For this purpose, a spatial multibody dynamic hip model was developed, using a friction-velocity constitutive law combined with a Hertzian contact model. Furthermore, the physiological three-dimensional rotation angles and forces are taken into account to calculate tangential and normal contact forces, respectively. Comparing the outcomes with that available in the literature allowed for the validation of our approach. It was shown that the cause of hip squeaking is friction-induced vibration owing to different phenomena such as stick–slip friction, negative-sloping friction and contact force changes. Moreover, friction-induced vibration does significantly change contact point path during the gait when compared to non-friction analysis.     

A predictive mechano-biological model of the bone-implant healing

The quality of the fixation orthopaedic implant to its surrounding bone determines its clinical longevity. Up to 20% of hip replacement operations are currently revisions for aseptic loosening. While this fixation quality is determined primarily by the bone and tissue anchoring the implant, conditions influencing bone growth in the early post-operative period include the surgical technique and coupled mechanical and biochemical factors. The aim of the study was to propose an original mechano-biological formulation of the healing process of periprosthetic tissue. The multiphasic porous model involved the solid osseous matrix, the extracellular fluid phase, the osteoblastic cellular phase responsible from the bone formation and the growth factor phase promoting the cellular activity. To derive the non-linear convective-diffuse governing equations, mass balance was associated to cell active haptotactic and chemotactic migration, growth factor diffusion, cell proliferation (logistic law) and bone formation (reactive medium). The in-vivo application concerned a canine axisymmetric implant which was stable and mechanically unloaded. Predictive numerical results were compared to ex-vivo data from a histologic study. The generic healing pattern involving two main oscillations of the radial bone formation was well predicted. In the future, the model could assist in evaluating the role of growth factor concentrations and their temporal delivering as far as the role of pertinent sources such as bioactive coating or additional biomaterials.     

Comparison of uniaxial and triaxial rosette gages for strain measurement in the femur

A major problem of hip prostheses and other bone fixation devices is that they alter the stress distribution in the femur. This phenomenon is named stress shielding, and derives from the bigger stiffness of the implant when compared to the bone. Strain gages are the most common tool used in in vitro stress-shielding investigations. There is a lack of agreement in the literature about which gage type is to be preferred (uniaxial grid, biaxial or triaxial rosette). Rosettes are required when complete information is needed. However, uniaxial gages can be advantageous because they reduce the number of measurement channels required. The aim of this work is to verify if (and under which hypothesis) uniaxial gages can replace triaxial rosettes.     

Experimental modal analysis of a synthetic composite femur

In this paper we describe the experimental characterization of the modal parameters of a synthetic composite femur model widely used in biomechanical research studies. The objective of the experimental procedure was to identify the natural frequencies and mode shapes of an unconstrained (free-free) femur. The experimental data were compared with the same obtained in an analog study performed with a fresh cadaveric femur bone. Other objective of the study was to investigate modal analysis as a technique to validate a finite element model of a composite femur with isotropic material properties.     

Development of an Internal Bone Remodelling Theory and Applications to Some Problems in Orthopaedic Biomechanics*

Bone tissue is a porous, heterogeneous and anisotropic material, which adapts its mechanical properties depending of the local stress level. This evolutive behaviour of the bone is normally known as bone remodelling. In this work, a bone-remodelling theory, based on the principles of continuum damage mechanics, is presented. The corresponding mathematical formulation has been implemented in a finite element code in order to predict the bone response after implantation of a prosthesis or fixation. Although the present model is not based on experimental verification, the model predicts important qualitative experimental results, being still necessary to test against experimental/clinical work. The main aim of this paper has been, therefore, the qualitative study of the long-term bone evolution, especially of the human femur when different types of implants are employed. A comparative analysis between two widely used hip prostheses (the Exeter and the SHP), has been performed. We have also studied the treatment of proximal femoral fractures by means of extramedullary and intramedullary implants.     

埋地管道的横向静力分析耦合模型及其解耦条件

现有埋地管道横向静力分析中的刚性管假设可以实现横向分析与纵向分析的解耦,但往往与实际情况不符.为此,本文根据埋地管道的受力特点,建立了考虑纵向内力影响的横向静力分析耦合模型.基于此耦合模型,结合挠曲线方程与纵向内力的关系,推导出横向分析和纵向分析的解耦条件,为建立解耦模型提供了理论基础.与此同时,一方面为便于实用,另一方面为检验解耦模型的误差,文中针对圆环形管道导出了其横截面剪应力分布规律,给出了埋地管道横向静力分析的实用耦合模型,并结合弹性中心法,建议和提出了耦合模型的实现算法.最后,采用耦合模型对两端固定的埋地给水管道进行了横向内力分析及解耦模型的误差探讨.结果表明,管道两端处纵向剪力对横向内力影响显著,解耦模型误差很大；但随着与管端距离的增加纵向剪力的影响急剧减小,近跨中区域解耦误差几乎可忽略不计.     

结构-地基系统静-动力联合分析模型

以有限区域模拟无限区域的动力计算必须考虑边界上波的传播效应,应不使波在边界上发生反射再返回到计算域中,并且应考虑初始静力场对其动力反应的影响。因此,基于无限元的静、动力特性提出静-动力统一无限元,通过算例验证无限元静-动力统一人工边界在静-动力联合分析模型中的精度和稳定性。结果表明:无限元静-动力统一人工边界在静力、动力及静-动力联合分析模型中具有很高的精度和良好的稳定性,突破了传统动力人工边界不能兼顾静力效应的局限。     

Experimental Measurement and Numerical Validation of Bone Cement Mantle Strains of an In Vitro Hip Replacement Using Optical FBG Sensors

Experimental pre-clinical tests associated with numeric models of cemented implants are important for screening of new implants in the market. The aim of this study was to measure strain profiles and maximum temperature polymerization inside a cement mantle of an in vitro cemented hip reconstruction using optical fiber Bragg grating (FBG) sensors. For this purpose, a hip femoral prosthesis was instrumented with 12 FBG sensors, three in each aspect of the femur, anterior, posterior, medial and lateral. These were positioned at the proximal, middle and distal part of the cement mantle relatively to the stem. Another sensor was placed in the lateral-proximal region of the mantle to measure the maximum temperature of cement polymerization. The strains measured were compared with those obtained with a Finite Element model, both for quaistatic mechanical loading. The results show that the experimental technique used can measure strains inside the cement mantle with good correlation, R²?=?0.970, with the numerical model results. The results present a maximum temperature of polymerization around 110°C inside of cement at proximal region. It was also observed strain concentration in lateral aspect of the femur in polymerization process. The procedure hereby explained can be used to improve experimental pre-clinical tests to measure the strain distribution inside the cement mantle as well as residual strain and temperature variation along with time, as a result of the curing process of cement.     

A two-phase computational biomechanics model for successful rehabilitation after hip and knee surgery

Nonlinear Dynamics - We propose a two-phase computational biomechanical model for a successful rehabilitation after hip and/or knee replacement surgery. The first phase, conducted before the...