Mechanics and Performance of Traceable UHMWPE Implants

描述（由申请人提供）：全髋关节置换术（THR）手术是美国晚期退行性关节疾病的标准治疗方法。2002年，估计有24.3万美国人从这种手术中受益。然而，18%的THR手术是翻修手术，与原发性THR相比，翻修手术的效果更差，经济负担更大。在美国，由于骨溶解和组织对聚乙烯磨损碎片的反应，髋关节植入物松动被认为是限制植入物寿命的主要问题。在过去的十年中，用于THR的聚乙烯材料在灭菌和配方方面发生了重大变化，因此一系列灭菌和辐射交联工艺现在应用于临床实践中使用的聚乙烯。然而，目前尚不清楚这些过程在多大程度上影响聚乙烯轴承组件在体内长期植入过程中的氧化降解倾向。目前尚不清楚体内聚乙烯氧化对当代髋关节置换术临床表现的影响程度。在这个为期五年的竞争延续中，我们建议扩展我们对可追溯的伽马空气灭菌聚乙烯髋关节轴承部件的研究，以涵盖用于髋关节置换术的回收伽马惰性灭菌和高度交联聚乙烯轴承。鉴于伽玛空气灭菌聚乙烯髋关节轴承组件在体内会发生氧化降解，从而显著降低其极限强度，本文提出了以下三个新的假设：(1)当代伽玛惰性灭菌聚乙烯髋关节轴承在体内使用过程中会发生{区域特异性}的力学性能降解；(2)含有残余自由基的退火高交联聚乙烯髋轴承在体内的机械性能会发生{区域特异性}降解，而经过淬火自由基处理的重熔高交联聚乙烯髋轴承在体内不会显著降解；(3)磨损和松动是高交联衬垫改型的原因，其发生率低于惰性灭菌衬垫。

DESCRIPTION (provided by applicant): Total hip replacement (THR) surgery is the standard of care for advanced degenerative joint disease in the US. In 2002, an estimated 243,000 Americans benefited from this procedure. However, 18% of all THR surgeries are revisions, which have poorer outcomes and greater economic burden than primary THRs. Loosening of hip implants, due to osteolysis and tissue reactions to polyethylene wear debris, is considered to be the main problem limiting implant longevity in the US. Within the past decade, polyethylene materials used for THR have undergone major changes in sterilization and formulation, so that a range of sterilization and radiation crosslinking processes are now applied to polyethylene used in clinical practice. However, it remains unclear to what extent these processes affect the tendency of polyethylene bearing components to oxidatively degrade during long-term implantation in the body. It is further unknown to what extent oxidation of polyethylene in the body impacts the clinical performance of contemporary hip replacements. In this five-year competing continuation, we propose to extend our study of traceable gamma-air sterilized polyethylene hip bearing components to encompass retrieved gamma-inert sterilized and highly crosslinked polyethylene bearings for hip arthroplasty. Knowing that gamma air-sterilized polyethylene hip bearing components undergo in vivo oxidative degradation with significant reduction of ultimate strength, the following three new hypotheses are proposed: (1) contemporary gamma inert sterilized polyethylene hip bearings will undergo {region-specific} degradation of mechanical properties during in vivo use; (2) annealed highly crosslinked, polyethylene hip bearings that contain residual free radicals will undergo {region-specific} degradation of mechanical properties in vivo and remelted highly crosslinked polyethylene hip bearings, that are processed to quench free radicals, will not degrade significantly in vivo; and (3) wear and loosening as reasons for revision of highly crosslinked liners will be lower in prevalence than in gamma inert sterilized liners.