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

描述（由申请人提供）：关节面磨损可能是髋关节置换部件寿命的最大限制。可以很好地研究正常关节载荷的关节面应力;然而，涉及边缘载荷的载荷情况还不太清楚，尽管它们似乎与重要的失效模式密切相关，如聚乙烯内衬的边缘开裂和陶瓷关节面的条纹磨损和吱吱声。这项拟议的研究将阐明涉及聚乙烯和陶瓷关节面的边缘载荷情况下的关节面应力。此外，它将在为成品部件和研究材料样品开发的磨损试验中引起这些应力。更换磨损的植入物不仅对患者造成创伤，而且也是国家医疗预算中的一项重大成本。缓解这些问题取决于提高种植体承载材料的耐久性，因为减少磨损及其产生的碎屑对于最大限度地延长种植体寿命至关重要。这项拟议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，这些情况目前知之甚少，但会导致严重的和当前的基于磨损的故障模式。该项目将研究两个边缘加载的例子。第一种是相对静态的情况，称为轻微半脱位，第二种是涉及微分离和撞击的动态情况。对于这两种情况，第一个目标是在实验室接触研究中模拟负载情况，然后对负载情况进行分析建模，以计算不可测量的量，例如接触应力。将评估赫兹和有限元分析模型，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。确定接触应力后，将为每个载荷工况开发两种不同的磨损试验。第一个测试将应用于真实的构件，并且它将赋予与第一个目标的单实例载荷类似的重复载荷。第二项试验也是重复载荷磨损试验，将适用于比成品部件形状更简单的替代试验样品。第二次试验作为第一次试验的简单替代的有效性将在两种试验方法之间建立密切等效的接触应力场后进行预测，并将通过比较经验结果进行评估。公共卫生相关性：翻修手术以替换失效或磨损的人工关节对患者来说是创伤性的，并且是医疗保健资源的重大消耗。聚乙烯髋臼内衬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潜在失效模式，但导致此类失效的载荷和应力尚未得到充分了解。本研究项目将分析髋关节植入物在最差载荷条件下的接触应力，并将开发新的磨损试验方法，以改善下一代植入物及其材料的临床前评价。

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.