Knee Implant Wear Evaluation-An Integrated Approach

描述（由申请人提供）：种植体磨损是限制现代全关节置换术寿命的主要问题。对抗种植体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理解，这些努力受到阻碍。三种相关但迄今为止主要独立的方法被用于研究磨损：检索分析，磨损模拟器和计算模拟。这三种方法都提供了有价值的信息，但都存在局限性。从回收的部件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。磨损模拟器连接捕获复杂的体内环境，导致磨损，不测量聚乙烯的应力和应变状态。使用有限元分析（FEA）的计算模拟具有局限性，因为仅通过单一应力或应变测量来评估磨损性能，并且必要的分析复杂性已将研究减少到仅针对几种加载条件或植入部件的相对位置。为了克服这些单独方法的局限性，我们开始了一个合并所有三种方法的项目。在初步工作中，我们将膝关节模拟器的计算模型与胫骨部件的有限元分析结合起来，在膝关节模拟器上进行磨损测量，并对回收的部件进行观察，以确定在模拟器中测试的胫骨部件的应力和应变历史。我们的目标是开发一种综合方法，结合每种方法的优势，以深入了解磨损机制和评估全膝关节置换术临床前性能的工具。为了实现这一目标，我们必须满足三个具体目标：(1)改进计算模型，以改进描述膝关节模拟器的前后和扭转约束的方式，并将改进的UHMWPE材料模型纳入其中，该模型将允许残余应变和应力在材料中发展；(2)校准模型，以准确预测各种模拟器条件和植入物设计的力、运动学、接触区域和位置；(3)通过数值模拟、模拟器数据和检索分析，优化膝关节模拟器，重现与膝关节设计一致的检索模式。实现我们的目标将提供聚乙烯膝关节植入物的应力和应变与磨损之间的有效联系，以及临床前测试方案，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，以减少评估磨损性能所需的模拟器测试次数。

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.