Testing to rank orthopaedic hip implant materials for their resistance to squeaki

描述（由申请人提供）：轴承表面的磨损可能是髋关节置换部件寿命的最大限制。正常节点荷载下的轴承应力可以得到很好的研究；然而，涉及边缘载荷的载荷情况不太清楚，尽管它们似乎与重要的失效模式密切相关，如聚乙烯衬垫的边缘开裂和陶瓷轴承的条纹磨损和吱吱声。本文提出的研究将阐明在涉及聚乙烯和陶瓷轴承的边缘加载情况下的轴承应力。此外，它将在为成品部件和研究材料样品开发的磨损测试中诱发这些应力。更换磨损的植入物不仅对患者造成创伤，而且也是国家医疗保健预算中的一项重大费用。减轻这些问题取决于提高种植体承载材料的耐用性，因为减少磨损及其产生的碎片对于最大限度地延长种植体寿命至关重要。这项提出的研究将通过关注轴承载荷和应力情况来解决这些重要的健康需求，这些情况人们知之甚少，但它们是造成严重和当前基于磨损的失效模式的原因。该项目将研究两个边缘加载的例子。第一种是一种相对静态的情况，称为轻微半脱位，第二种是一种更动态的情况，涉及微分离和冲击。对于这两种情况，第一个目标是在实验室接触研究中模拟载荷情况，然后对载荷情况进行解析建模，以计算不可测量的量，如接触应力。将对赫兹分析模型和有限元分析模型进行评估，并通过将计算的接触面积与实验结果进行比较来验证模型的有效性。随着接触应力的确定，将为每个负载情况开发两种不同的磨损试验。第一个测试将应用于真实的组件，它将赋予类似于第一个目标的单实例负载的重复负载。第二个测试，也是重复载荷磨损测试，将适用于比成品部件形状更简单的替代测试样品。第二次测试作为第一次测试的简单代理的有效性将基于在两种测试方法之间建立紧密等效的接触应力场，并将通过经验结果的比较来评估。公共卫生相关性：修复手术替代失效或磨损的人工关节对患者是创伤性的，并且是卫生保健资源的重大消耗。聚乙烯髋臼衬垫的边缘开裂和陶瓷部件的吱吱声是髋关节植入物的两种重要的潜在失效模式，但导致这种失效的载荷和应力尚未得到很好的了解。该研究项目将分析髋关节植入物在最坏载荷条件下的接触应力，并将开发新的磨损测试方法，以改进下一代植入物及其材料的临床前评估。

DESCRIPTION (provided by applicant): Wear of bearing surfaces is possibly the greatest limitation to the longevity of hip joint replacement components. The bearing stresses from normal joint loading may be well studied; however, load cases involving edge loading are less well understood, though they appear to be closely linked to important failure modes such as rim cracking in polyethylene liners and stripe wear and squeaking in ceramic bearings. This proposed research will elucidate the bearing stresses in cases of edge loading involving both polyethylene and ceramic bearings. Further, it will induce these stresses in wear tests developed for finished components and for research material samples. Replacement of worn implants is not only traumatic for patients, but is also a significant cost in the nation's healthcare budget. Mitigating these problems hinges upon improving the durability of implant bearing materials, because reducing wear and its resulting debris is essential to maximizing implant longevity. This proposed research will address these important health needs by its attention to bearing load and stress cases that are poorly understood but which are responsible for serious and current wear- based failure modes. The project will examine two examples of edge loading. The first is a relatively static case called subtle subluxation, and the second is a more dynamic case involving microseparation and impact. For both cases, the first aim is simulate the load case in a laboratory contact study, and then to analytically model the load case to calculate immeasurable quantities such as the contact stress. Both Hertzian and finite element analytic models will be evaluated, and the models will be validated by comparing the calculated contact area with the experimental results. With the contact stresses identified, two different wear tests will be developed for each load case. The first test will apply to real components, and it will impart repetitive loads similar to the single-instance load from the first aim. The second test, also a repetitive-load wear test, will apply to surrogate test samples that are more simply shaped than finished components. The validity of the second test as a simpler proxy for the first test will be predicated upon establishing closely equivalent contact stress fields between the two test methods, and will be evaluated by comparison of empirical results. PUBLIC HEALTH RELEVANCE: Revision surgery to replace failed or worn-out artificial joints is traumatic to patients and is a significant drain on heath-care resources. Rim cracking of polyethylene acetabular liners and squeaking in ceramic components are two important potential failure modes of hip implants, but the loads and stresses that cause such failures are not well understood. This research project will analyze contact stresses in hip implants under worst case load conditions and will develop new wear test methods to improve the pre-clinical evaluation of next-generation implants and their materials.