In vitro wear testing of Metal on Polymer artificial hip components under intermittent motion conditions.

全髋关节置换术(THR)于2007年在《柳叶刀》杂志上被称为世纪手术，是目前世界上最常用的关节置换手术[1，2]。虽然这种手术有良好的成功率，但可能会出现并发症，导致一系列需要重新手术的临床问题[1]。最常见的失效原因是从关节表面释放的磨屑的不利影响。这在金属对金属植入物的设计中尤其有问题，这种植入物的佩戴量比预期的要多，并释放出破坏性的金属碎片，对患者造成有害的副作用[3，4]。因此，金属对聚合物(MOP)连接设计是目前最常用的设计[1]。部件的临床前磨损测试是避免此类问题的关键。同样重要的是，这些测试要准确地模拟组件植入后可能遇到的条件。目前，根据国际标准ISO14242[5]，人工髋关节部件的模拟器测试大多采用连续步行周期，速度为每秒一个周期(频率为1赫兹)。这一标准还意味着一个人在停下来之前要走50万步，这与人们的生活方式是不准确的。人们倾向于走一小段时间，然后站着，病人往往走得比建议的慢得多[6，7]。因此，在间歇运动或“行走-站立-行走”负荷和运动方案下进行模拟器测试更具临床意义。有证据表明，在这些条件下，部件将经历更多的磨损，但涉及MOP部件的研究很少[8-11]。目的研究临床相关间歇运动和载荷条件下聚合物髋关节假体上金属的磨损特性。目的*开发临床相关的测试方案*更新模拟器编程以应用间歇运动条件*比较在ISO标准和间歇运动条件下获得的部件的磨损结果。方法纽卡斯尔大学最新开发的髋关节模拟器(图2)将用于在ISO标准条件下和不同频率的间歇行走条件下对最常见的THR假体进行磨损测试。然后将对所获得的结果进行比较分析。测试将按如下方式进行：*1赫兹的ISO 14242条件*1赫兹的站立行走条件*0.5赫兹的ISO 14242条件*0.5赫兹的站立行走条件所有测试将运行500,000个循环，每500,000个循环暂停以进行磨损测量。将进行重量测量和表面粗糙度分析，以评估部件磨损。还将分析磨屑。未进行评估的测试条件将保持在ISO标准指南中，以确保适当地建立可变影响。影响仅在英国，2018年就进行了近10万例髋关节置换[1]。在植入前对人工关节进行更好的测试将确保患者能够尽可能地无痛地生活，使他们能够过上更幸福和更有成效的生活。预计这项研究的结果可能有助于改变目前的临床前磨损测试人工髋关节的标准，以包括更多与临床相关的测试条件。参考文献[1]W.英格兰、北爱尔兰和马恩岛国家联合登记处，“第16次年度报告”，2019年，2054-183X期。[在线]。参考文献：《柳叶刀》，第370卷，第9597期，第1508-1519页，2007年，DOI：10.1016/S0140-6736(07)60457-7。

BackgroundTotal hip replacement (THR) was described as 'the operation of the century' in The Lancet in 2007, and is currently the most commonly implemented joint replacement procedure world-wide [1, 2]. Although this procedure has reputable success rates, complications can arise leading to a range of clinical issues which require revision surgery [1]. The most prevalent causes for failure are the adverse effects of wear debris released from articulating surfaces. This was particularly problematic in metal-on-metal implant designs, which wore more than expected and released damaging metal debris, causing detrimental side effects in patients [3, 4]. Subsequently, metal on polymer (MoP) joint designs are currently the most commonly implemented [1]. Pre-clinical wear testing of components is essential in avoiding such issues. It is also of high importance that these tests accurately simulate the conditions components are likely to encounter once they are implanted. Currently, simulator testing of artificial hip components mostly apply a continuous walking cycle, at a speed of one cycle per second (frequency of 1Hz), as per the international standard ISO14242 [5]. This standard also implies that a person walks for 500,000 steps before stopping, which is inaccurate to how people live. People tend to walk for short periods and then stand, with patients tending to walk much slower than is suggested [6, 7]. Thus, simulator testing under an intermittent motion or "walk-stand-walk" loading and motion protocol makes more clinical sense. Evidence suggests that, under these conditions, components will experience more wear, however research is minimal where MoP components are concerned [8-11].AimTo investigate wear characteristics of metal on polymer hip replacement components under clinically relevant intermittent motion and load conditions.Objectives* Develop clinically relevant testing protocol * Update simulator programming to apply intermittent motion conditions* Compare wear results from components obtained under ISO standard and intermittent motion conditions.MethodologyA newly developed hip simulator (figure 2), at Newcastle University, will be utilised to conduct wear tests on the most common type of THR implant under ISO standard conditions and intermittent walking conditions at varied frequencies. A comparative analysis will then be conducted of results obtained. Tests will take place as follows:* ISO 14242 condition at 1Hz* Walk-stand-walk condition at 1Hz* ISO 14242 condition at 0.5Hz* Walk-stand-walk condition at 0.5HzAll tests will run for 5 million cycles, pausing every 500,000 cycles to take wear measurements. Gravimetric measurements will be taken as well as analysis of surface roughness, to assess component wear. Wear debris will also be analysed.Test conditions which aren't being assessed will be maintained to ISO standard guidelines to ensure proper establishment of variable effects. ImpactAlmost 100,000 total hip replacements were conducted in 2018 in the UK alone [1]. Better testing of artificial joints prior to implantation will ensure that patients are able to live pain-free with as much mobility as possible, enabling them to live happier and more productive lives. It is envisaged that the results of this research could contribute to changes to the current standards for pre-clinical wear testing artificial hip joints to include more clinically relevant test conditions. References[1] W. National Joint Registry for England, Northern Ireland and the Isle of Man, "16th Annual Report," 2019, issue 2054-183X. [Online]. Available: www.njrcentre.org.uk[2] I. D. Learmonth, C. Young, and C. Rorabeck, "The operation of the century: total hip replacement," The Lancet, vol. 370, no. 9597, pp. 1508-1519, 2007, doi: 10.1016/S0140-6736(07)60457-7.[3] "REF Impact Case Study Supporting national and international policy development on the