Biotribological engineering design for upper limb arthroplasty

使用交联聚乙烯（XLPE）作为承载材料的髋关节置换植入物实现了低磨损。以前在非xlpe中发生的磨损颗粒导致骨死亡、植入物松动和翻修手术的重大临床问题已经基本消除。同样，在膝关节置换术中，超过一半的新手术使用XLPE植入物。在上肢关节置换术中，越来越流行的反向全肩关节置换术（RTSA）常用于治疗严重的骨关节炎。它与自然的肩部几何形状相反，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，但在报告的临床失败中，会出现其他问题，这些问题往往会掩盖磨损的原因。因此，对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器将使许多RTSA植入物尽可能接近体内发生的条件。XLPE与非XLPE磨损率的比较被提出，这将对应于它们在体内最初几年的性能。然后，研究不同种植体设计参数的影响。目的是利用这些发现来设计RTSA植入物，以减少磨损，从而减少临床失败率。另一种日益流行的上肢手术（通常在肘部骨折后需要）是桡骨头半关节置换术（RHH）。它包括用金属部件替换肘关节的径向表面，然后在相对的自然关节表面滑动。这里出现的问题是自然关节表面的逐渐磨损和损伤，导致临床失败，需要翻修手术。一种可能的解决方案是使用一种柔顺的、损伤较小的材料作为植入体表面。众所周知，这可以改善润滑并减少接触应力，但必须研究柔顺材料表面的长期疲劳，以确定它是否会在体内存活。它被提议使许多被称为Bionate的弹性体材料试样经受表面疲劳。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Bionate表面不会对它们造成明显的伤害，当然，最终需要进行临床试验，但这不是本提案的一部分。因此，拟议的研究计划包括两个相当大范围的项目，它们都涉及上肢关节置换术，并试图设计植入物以降低临床失败率。

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.