Jones E, Scholes S C, Burgess I C, Ash H E, Unsworth A
Stryker Orthopaedics, Limerick, Co. Limerick, Ireland.
Proc Inst Mech Eng H. 2009 Jan;223(1):1-12. doi: 10.1243/09544119JEIM446.
Artificial joints have been much improved since their introduction but they still have a limited lifetime. In an attempt to increase their life by improving the lubrication acting within these prostheses, compliant layered polyurethane (PU) joints have been devised. These joints mimic the natural synovial joint more closely by promoting fluid film lubrication. In this study, tests were performed on compliant layer joints to determine their ability to function under a range of conditions. Both static and dynamic compression tests were undertaken on compliant artificial hip joints of two different radial clearances. Friction tests were also performed before and after static loading. In addition to this, knee wear tests were conducted to determine the suitability of a compliant layer in these applications. In the knee tests, variations in experimental testing conditions were investigated using both active and passive rotation and severe malalignment of the tibial inserts. The static compression tests together with the friction studies suggest that a small radial clearance is likely to result in 'grabbing' contact between the head and cup. The larger radial clearance (0.33 microm) did not exhibit these problems. The importance of the design of the compliant layer joints was highlighted with delamination occurring on the lateral bearings during the knee wear studies. The bearings with a layer 2 mm thick performed better than the bearings with a layer 3 mm thick. Tests conducted on flat PU bearings resulted in no delamination; therefore, it was concluded that the layer separation was caused by design issues rather than by material issues. It was found that, with careful material choice, consideration of design, and effective manufacturing techniques, the compliant layer joint functioned well and demonstrated durability of the union between the hard and soft layers. These results give encouragement for the suitability of these joints for clinical use.
自人工关节问世以来已有了很大改进，但它们的使用寿命仍然有限。为了通过改善这些假体内部的润滑作用来延长其使用寿命，人们设计了柔顺层状聚氨酯（PU）关节。这些关节通过促进液膜润滑更紧密地模拟天然滑膜关节。在本研究中，对柔顺层关节进行了测试，以确定它们在一系列条件下的功能。对两种不同径向间隙的柔顺人工髋关节进行了静态和动态压缩测试。还在静态加载前后进行了摩擦测试。除此之外，还进行了膝关节磨损测试，以确定柔顺层在这些应用中的适用性。在膝关节测试中，使用主动和被动旋转以及胫骨植入物的严重排列不齐来研究实验测试条件的变化。静态压缩测试和摩擦研究表明，较小的径向间隙可能会导致股骨头与髋臼杯之间出现“卡紧”接触。较大的径向间隙（0.33微米）没有出现这些问题。在膝关节磨损研究中，外侧轴承出现分层，突出了柔顺层关节设计的重要性。2毫米厚层的轴承比3毫米厚层的轴承表现更好。对扁平PU轴承进行的测试没有导致分层；因此，得出的结论是，层分离是由设计问题而非材料问题引起的。研究发现，通过仔细选择材料、考虑设计和采用有效的制造技术，柔顺层关节功能良好，并证明了硬层和软层之间结合的耐久性。这些结果为这些关节适用于临床应用提供了鼓励。
