Knee Implant Wear Evaluation-An Integrated Approach

描述(申请人提供)：种植体磨损是限制现代全关节置换术寿命的主要问题。对抗植入物磨损的努力包括改进设计和引入新的轴承材料。然而，由于缺乏对磨损机制以及材料和植入物设计变量如何影响磨损的了解，这些努力受到了阻碍。到目前为止，研究磨损的方法有三种：恢复分析、磨损模拟和计算模拟。这三家公司都提供了有价值的信息，但都受到了限制。从回收的部件上进行的观察受到限制，因为造成损坏的载荷和运动学在很大程度上是未知的。磨损模拟器连接捕捉导致磨损的体内复杂环境，而不测量聚乙烯中的应力和应变状态。使用有限元分析(FEA)的计算模拟也有局限性，因为磨损性能只能通过单一的应力或应变测量来评估，而且必要的分析复杂性使研究仅限于少数几个加载条件或种植体部件的相对位置。为了克服这些单独方法的局限性，我们启动了一个项目，将所有三种方法合并在一起。在前期工作中，我们将膝关节模拟器的计算模型与胫骨组件的有限元分析相结合，在膝关节模拟器上进行磨损测量，并对回收的组件进行观察，以确定在模拟器中测试的胫骨组件的应力和应变历史。我们的目标是开发一种综合的方法，结合每种方法的优点，提供对磨损机制的洞察，并提供一种评估全膝关节置换临床前性能的工具。为了达到这一目标，我们必须达到三个具体目标：(1)改进计算模型，以改进描述膝关节模拟器前后和扭转约束的方式，并采用改进的UHMWPE材料模型，使材料中能够产生残余应变和应力；(2)校准模型，以准确预测力、运动学以及接触区域和位置，以适应各种模拟器条件和假体设计；(3)通过使用数值模拟、模拟器数据和检索分析，优化膝关节模拟器，以再现与膝关节设计一致的检索模式。实现我们的目标将在聚乙烯膝关节植入物的应力和应变与磨损和临床前测试方案之间提供经过验证的联系，通过使用我们的计算模拟来最大限度地提高膝关节模拟器的效率，从而最大限度地减少评估磨损性能所需的模拟器测试数量。

DESCRIPTION (provided by applicant): Implant wear is the major problem limiting the longevity of modern total joint replacements. Efforts to combat implant wear have included design improvements and the introduction of new bearing materials. These efforts are hampered, however, by lack of understanding of wear mechanisms and of how material and implant design variables influence wear. Three related but heretofore primarily separate approaches have been employed in studying wear: retrieval analysis, wear simulators and computational simulations. All three have provided valuable information, but all suffer from limitations. Observations made from retrieved components limited in that the loads and kinematics responsible for the damage are largely unknown. Wear simulators connect capture the complex in vivo environment that leads to wear and do not measure the stress and strain state in the polyethylene. Computational simulations using finite element analysis (FEA) have limitations as well - wear performance has been assessed only from singular stress or strain measures and the necessary analytical complexity has reduced studies to only a few loading conditions or relative positions of the implant components. To overcome limitations in these individual methods, we have embarked on a project to merge all three approaches. In preliminary work, we have combined a computational model of a knee simulator with FEA of the tibial component, wear measurements performed on the knee simulator, and observations made on retrieved components to determine the stress and strain histories in tibial components tested in the simulator. Our goal is to develop an integrated approach that combines the strengths of each methodology to provide insight into wear mechanisms and a tool for assessing the preclinical performance of total knee replacements. To reach this goal, we must meet three Specific Aims: (1) refine the computational model to improve the way in which anteroposterior and torsional constraints to the knee simulator are described and to incorporate an improved material model for UHMWPE that will allow residual strains and stresses to develop in the material; (2) calibrate the model to accurately predict forces, kinematics, and contact areas and locations for a range of simulator conditions and implant designs; (3) optimize the knee simulator to reproduce retrieval patterns that are consistent within knee designs by using numerical simulation, simulator data, and retrieval analysis. Achieving our goal will provide a validated link between stresses and strains in polyethylene knee implants and wear and preclinical testing protocols that maximize knee simulator efficiency by using our computational simulation to minimize the number of simulator tests required to assess wear performance.