Biotribological Layers in Metal-on-Metal Hip Replacement

描述(申请人提供)：由于体积磨损量较小(与传统的金属对超高分子质量聚乙烯相比)和使用大股骨头的能力，用于髋关节置换的金属对金属(MOM)轴承在过去几年中越来越受欢迎，从而降低了脱位的风险，脱位是髋关节置换需要翻修手术的常见并发症。大的股骨头也为外科医生提供了一种选择，即在不破坏股骨干干端或干骨干端的情况下重新铺设股骨头(髋关节表面置换术)，从而保留股骨的骨量。然而，MOM关节重建引起关注的一个原因，最近出现了越来越多的关于早期不良局部组织反应损害这些重建的功能和存活率的报道。这些不良反应包括假体周围骨丢失(骨溶解)、迟发性超敏反应和软组织肿块(所谓的假瘤)，是由局部细胞对颗粒和离子磨损和腐蚀性碎屑的反应引起的。越来越多的证据表明，局部细胞的反应与这些轴承对产生的碎片数量有关。因此，临床上迫切需要描述碎片产生的机制，以便将这些不利的局部组织反应降至最低。不幸的是，人们对这对轴承的摩擦学知之甚少。我们的实验室进行了一项新的观察，发现金属对金属轴承在铰接过程中会发生微观结构变化和与关节环境的摩擦化学反应。这一行为导致了上表面的冶金变化，并导致了纳米晶金属(氧化物)和有机成分的机械混合区的产生。这种区域-也称为摩擦材料-有利地影响摩擦学性能以及摩擦磨损行为，如机械和汽车工程中相关的边界润滑应用所显示的那样。在本提案中，我们将解决中心假设，即金属颗粒和变性蛋白质的结合在金属轴承上形成一层生物摩擦学层，在减少磨损和腐蚀方面具有协同效应。我们已经组建了一个多学科的调查小组，他们将解决以下可能对MoM轴承在髋关节置换中的性能产生重大影响的具体目标：1)使用磨损模拟加速测试来确定生物摩擦层成分在金属近表面区域演变中的作用，并将这些与从MOM髋关节或表面置换患者那里获得的设备回收进行比较；2)确定回收和体外样本的机械混合区的相关特性，并演示嵌入有机成分的效果；以及3)证明机械混合区的存在将有益地影响钴铬合金的(摩擦)腐蚀行为

DESCRIPTION (provided by applicant): Metal-on-metal (MoM) bearings for hip replacement have surged in popularity over the last several years due to lower volumetric wear (compared to conventional metal-on-ultrahigh molecular weight polyethylene) and the ability to use large femoral heads, reducing the risk of dislocation, a common complication of hip replacement necessitating revision surgery. Large femoral heads also provide the surgeon with the option of resurfacing the femoral head without breaching the femoral metaphysis or diaphysis (hip resurfacing arthroplasty) thereby preserving femoral bone stock. However, a cause for concern with MoM joint reconstruction, has recently emerged with increasing reports of early adverse local tissue responses compromising the functionality and survivorship of these reconstructions. These adverse responses, which include periprosthetic bone loss (osteolysis), delayed-type hypersensitivity and soft tissue masses (so-called pseudotumors) are governed by the local cellular reaction to particulate and ionic wear and corrosion debris. There is growing evidence that the local cell response is related to the amount of debris generated by these bearing couples. Thus, there is an urgent clinical need to delineate the mechanisms of debris generation in order to minimize these adverse local tissue responses. Unfortunately, the tribology of this bearing couple is little understood. Our laboratory has made the novel observation that metal-on-metal bearings undergo microstructural changes and tribochemical reactions with the joint environment during articulation. This behavior causes changes in the metallurgy of the upper surface and brings about the generation of a mechanically mixed zone of nanocrystalline metal (oxide) and organic constituents. Such a zone - also called tribomaterial - favorably influences the tribological properties as well as the tribocorrosive behavior, as has been shown for related boundary lubricated applications in mechanical and automotive engineering. In the present proposal, we will address the central hypothesis that the combination of metal particles and denatured proteins form a biotribological layer in metal on metal bearings that has synergistic effects in reducing wear and corrosion. We have assembled a multidisciplinary investigative team that will address the following specific aims that will likely have a significant impact of the performance of MoM bearings in hip replacement: 1) to determine the role of the biotribological layer constituents in the evolution of the near-surface region of the metal using wear simulations for accelerated testing and compare these to device retrievals obtained from patients undergoing MoM hip or surface replacement; 2) to determine the relevant properties of the mechanically mixed zone of retrievals and in-vitro samples and demonstrate the effect of embedded organic constituents; and 3) to demonstrate that the presence of a mechanically mixed zone will beneficially effect the (tribo-)corrosion behavior of the cobalt-chromium alloy