Knee Implant Wear Evaluation-An Integrated Approach

描述（由申请人提供）：植入物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设计改进和引入新的关节面材料。然而，由于对磨损机制以及材料和植入物设计变量如何影响磨损缺乏了解，这些努力受到阻碍。三个相关的，但迄今为止主要是独立的方法已被用于研究磨损：检索分析，磨损模拟器和计算模拟。这三个国家都提供了宝贵的信息，但都受到限制。从回收的部件中进行的观察有限，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导致磨损的复杂体内环境，并且不测量聚乙烯中的应力和应变状态。使用有限元分析（FEA）进行的计算模拟也有局限性-仅通过单一应力或应变测量评估了磨损性能，并且必要的分析复杂性使研究减少到仅几种载荷条件或植入物组件的相对位置。为了克服这些单独方法的局限性，我们已经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FEA、在膝关节模拟器上进行的磨损测量以及对取出的部件进行的观察相结合，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，以提供对磨损机制的深入了解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，我们必须满足三个特定目标：（1）完善计算模型，以改进描述膝关节模拟器前后和扭转约束的方式，并纳入UHMWPE的改进材料模型，以允许在材料中产生残余应变和应力;（2）校准模型，以准确预测用于一系列模拟器条件和植入物设计的力、运动学和接触面积和位置;（3）通过使用数值模拟、模拟器数据和回收分析，优化膝关节模拟器，以再现与膝关节设计一致的回收模式。实现我们的目标将提供聚乙烯膝关节植入物中的应力和应变与磨损和临床前试验方案之间的有效联系，通过使用我们的计算模拟来最大限度地减少评估磨损性能所需的模拟器试验次数，从而最大限度地提高膝关节模拟器的效率。

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.