Biotribological engineering design for upper limb arthroplasty

使用交联聚乙烯(XLPE)作为轴承材料的髋关节置换植入物已经实现了低磨损。使用非XLPE时出现的磨损颗粒导致骨死亡、种植体松动和翻修手术等先前显著的临床问题已基本消除。此外，在膝关节成形术中，超过一半的新手术使用XLPE植入物。*在上肢关节成形术中，日益流行的反向全肩关节成形术(RTSA)经常用于治疗严重的骨关节炎。它反转了自然的路肩几何图形，并可以使用非XLPE作为轴承材料。一些实验室测试表明，使用XLPE可以大大降低磨损率，但出现的其他问题往往会掩盖所报告的临床故障中的任何磨损原因。因此，XLPE的需求仍然不确定。*为了解决上述问题，现有的模拟器测试机将对许多RTSA植入物进行尽可能接近体内发生的条件。建议将XLPE和非XLPE的磨损率进行比较，以符合它们在体内最初几年的性能。然后，对各种种植体设计参数的影响进行了研究。其目的是利用这些发现来设计RTSA植入物，以减少磨损，从而降低临床失败率。*另一种日益流行的上肢手术(通常在肘部骨折后需要)是放射头半关节置换术(RHH)。它只涉及用金属部件替换肘部的径向表面，然后金属部件滑动到相对的自然关节表面。这里出现的问题是自然关节表面的渐进性磨损和损坏，导致临床失败并需要翻修手术。*一种可能的解决方案是使用一种顺应性的、损伤较小的材料作为植入物表面。众所周知，这可以改善润滑性和降低接触应力，但必须研究柔顺材料表面的长期疲劳，以确定它是否能在体内存活。有人建议对一种名为生物体的弹性材料的一些试件进行表面疲劳试验。一旦研究了表面疲劳，就有可能改进RHH的设计。目前一些针对自然表面的实验室测试也将继续进行，以确保仿生表面不会造成明显的伤害，当然，最终将需要临床试验，但它们不是这项提议的一部分。*因此，拟议的研究计划涉及两个规模相当大的项目，它们都涉及上肢关节置换，并试图设计植入物设计，以降低临床失败率。

Hip joint replacement implants have achieved low wear using crosslinked polyethylene (XLPE) as a bearing material. The previously significant clinical problem of wear particles causing bone death, implant loosening and revision surgeries that occurred with non-XLPE has been essentially eliminated. Also, in knee arthroplasty, more than half of the new procedures use implants with XLPE.***In upper limb arthroplasty, the increasingly popular reverse total shoulder arthroplasty (RTSA) is often used to treat severe osteoarthritis. It reverses the natural shoulder geometry and may use non-XLPE as a bearing material. Some laboratory testing has suggested that wear rates can be much reduced by using XLPE but other problems occur that tend to obscure any wear causation in the reported clinical failures. Thus, the need for XLPE remains uncertain.***To address the above issues, an existing simulator test machine will subject a number of RTSA implants to conditions as close as possible to those occurring in the body. A comparison of XLPE with non-XLPE wear rates is proposed that would correspond to their performance for the first few years in the body. Then, the influences of various implant design parameters will be investigated. The intent is to use these findings to engineer the design of RTSA implants to reduce wear and thus the clinical failure rates.***Another increasingly popular upper limb procedure (often needed after elbow fractures) is radial head hemiarthroplasty (RHH). It involves replacing only the radial surface of the elbow with a metal component which then slides against the opposing natural joint surface. The problem that arises here is one of progressive wear and damage to the natural joint surface that causes clinical failure and requires revision surgery.***A possible solution is to use a compliant, less damaging material for the implant surface. This is known to improve lubrication and reduce contact stress but the long term fatigue of the compliant material surface must be investigated to determine whether it will survive in the body. It is proposed to subject a number of specimens of an elastomeric material known as Bionate to surface fatigue. Once the surface fatigue has been explored, an improved design for RHH may be possible. Some current laboratory testing against natural surfaces will also be continued to ensure that the Bionate surfaces do not cause them overt harm and, of course, eventually clinical trials would be needed but they are not part of this proposal.***Thus, the proposed research program involves two projects of considerable scope that have the commonality that they both involve upper limb joint replacement and attempt to engineer the implant designs to reduce clinical failure rates.