Improved friction and wear performance in polymeric components of orthopaedic bearings.

髋关节和膝关节置换术通常使用由金属(钴铬合金)和塑料(超高分子质量聚乙烯)制成的特殊部件设计。这些设备是治疗严重退行性关节疾病的首选，现在正被植入更年轻、更活跃的患者身上。因此，越来越需要提高它们的耐用性，特别是在塑料部件中的磨损方面。令人担忧的是骨溶解现象，即人工关节周围的骨骼对塑料磨损颗粒发生反应并死亡。因此，植入物松动，需要更换。用于髋关节的聚乙烯的设计已经有所改进，但对于膝盖等高应力关节却并非如此。*这个项目研究了一种处理塑料以减少磨损的新方法。人们认为，聚乙烯表面的凹痕会卷起关节液体，从而形成局部加压区域，从而降低塑料本身的应力。在之前由NSERC资助的一项研究中，人们发现，在这些系统中，特定的凹痕模式可以减少塑性应力，也可以减少摩擦。然而，其他实验室的研究表明，导致过度磨损的条件之一不是行走的连续运动，而是停止和启动的不连续运动。人们认为，在这些情况下，润滑表面的液体在停止时会渗出，因此当再次开始运动时，塑料没有受到保护而不会磨损。*本项目的目标是了解这种磨损机制，并确定纹理的初步积极发现是否会减少间歇性运动中的塑料磨损。塑料样品将在模拟停止-启动运动的设备中进行纹理和测试。如果成功，将在磨损模拟器中对人工关节的纹理过程进行评估，产生与现实生活中相同的载荷和运动。每年有近2.5万加拿大人和全球60万人植入人工膝关节。通过提高它们的耐用性，超过目前预期的15年，研究人员希望为越来越多的老年人口提供远远超过现在可能的终身活动。

Hip and knee replacements are most often designed using specialized components made of metal (cobalt chrome) and plastic (ultrahigh molecular weight polyethylene). These devices are the treatment of choice for severe degenerative joint disease, and they are now being implanted in younger more active patients. As a result, there is an increased need to improve their durability, particularly with respect to wear in the plastic component. Of concern is the phenomenon of osteolysis, in which the bone surrounding an artificial joint reacts to plastic wear particles and dies. Consequently, the implant loosens and needs to be replaced. There have been improvements in the design of polyethylene for use in hips, but this has not been the case for highly stressed joints such as the knee. ******This project examines a novel way of treating the plastic to reduce wear. It is thought that indentations in the polyethylene surface will entrain joint fluid, thus developing locally pressurized regions that reduce the stress on the plastic itself. In a previous NSERC-funded study, it was discovered that specific patterns of indentations reduce plastic stress and also reduce friction in these systems. However, research in other laboratories has shown that one of the conditions leading to excessive wear is not the continuous motion of walking, but the discontinuous motion of stopping and starting. It is thought that during these episodes, the fluid that lubricates the surfaces seeps out when stopping, thus leaving the plastic unprotected from wear when motion starts again. ******The objective of this project is to understand this mechanism of wear and to determine whether the initial positive findings of texturing will result in reduced plastic wear during intermittent motion. Samples of plastic will be textured and tested in a device that simulates the stop-start motion. If successful, the texturing process will be evaluated on artificial joints in a wear simulator that produces the same loads and motion that occur in real life.******Nearly 25,000 Canadians and 600,000 worldwide are implanted with an artificial knee each year. By improving their durability beyond the 15 years currently expected, researchers hope to provide a growing number of our aging population with a lifetime of activity well past what is now possible.