Biotribological Layers in Metal-on-Metal Hip Replacement

描述（由申请人提供）：金属对金属（MoM）髋关节置换术轴承在过去几年中越来越受欢迎，因为体积磨损更小（与传统的金属对超高分子量聚乙烯相比），并且能够使用大股骨头，减少脱位的风险，脱位是髋关节置换术中需要翻修手术的常见并发症。大股骨头也为外科医生提供了在不破坏股骨干骺端或骨干（髋关节置换术）的情况下置换股骨头的选择，从而保护股骨。然而，最近出现了越来越多的早期不良局部组织反应损害这些重建功能和存活的报道，这引起了人们对MoM关节重建的关注。这些不良反应，包括假体周围骨丢失（骨溶解），延迟型超敏反应和软组织肿块（所谓的假肿瘤），是由局部细胞对颗粒和离子磨损和腐蚀碎片的反应控制的。越来越多的证据表明，局部细胞反应与这些轴承偶产生的碎片数量有关。因此，临床迫切需要描述碎片产生的机制，以尽量减少这些不良的局部组织反应。不幸的是，这种轴承对摩擦学知之甚少。我们的实验室进行了新的观察，金属对金属轴承经历微观结构变化和摩擦化学反应与关节环境在关节。这种行为导致上表面的冶金变化，并产生纳米晶金属（氧化物）和有机成分的机械混合区。这样一个区域——也被称为摩擦材料——对摩擦学性能和摩擦腐蚀行为有有利的影响，正如在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组合在金属轴承上形成金属生物摩擦学层，在减少磨损和腐蚀方面具有协同作用。我们组建了一个多学科的调查团队，将解决以下具体目标，这些目标可能会对髋关节置换中MoM轴承的性能产生重大影响：1)使用磨损模拟加速测试来确定生物摩擦学层成分在金属近表面区域演变中的作用，并将其与接受MoM髋关节或表面置换的患者获得的设备检索进行比较；2)确定回收物与体外样品机械混合区的相关性质，并论证包埋有机成分的影响；3)证明机械混合区的存在有利于钴铬合金的（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