Santavirta Seppo
Biomedical Technology Group, Department of Applied Physics, University of Kuopio, Finland.
Acta Orthop Scand Suppl. 2003 Dec;74(310):1-19. doi: 10.1080/00016470310018108.
Particulate wear debris in totally replaced hips causes adverse local host reactions. The extreme form of such a reaction, aggressive granulomatosis, was found to be a distinct condition and different from simple aseptic loosening. Reactive and adaptive tissues around the totally replaced hip were made of proliferation of local fibroblast like cells and activated macrophages. Methylmethacrylate and high-molecular-weight polyethylene were shown to be essentially immunologically inert implant materials, but in small particulate form functioned as cellular irritants initiating local biological reactions leading to loosening of the implants. Chromium-cobalt-molybdenum is the most popular metallic implant material; it is hard and tough, and the bearings of this metal are partially self-polishing. In total hip implants, prerequisites for longevity of the replaced hip are good biocompatibility of the materials and sufficient tribological properties of the bearings. The third key issue is that the bearing must minimize frictional shear at the prosthetic bone-implant interface to be compatible with long-term survival. Some of the approaches to meet these demands are alumina-on-alumina and metal-on-metal designs, as well as the use of highly crosslinked polyethylene for the acetabular component. In order to avoid the wear-based deleterious properties of the conventional total hip prosthesis materials or coatings, the present work included biological and tribological testing of amorphous diamond. Previous experiments had demonstrated that a high adhesion of tetrahedral amorphous carbon coatings to a substrate can be achieved by using mixing layers or interlayers. Amorphous diamond was found to be biologically inert, and simulator testing indicated excellent wear properties for conventional total hip prostheses, in which either the ball or both bearing surfaces were coated with hydrogen-free tetrahedral amorphous diamond films. Simulator testing with such total hip prostheses showed no measurable wear or detectable delamination after 15,000,000 test cycles corresponding to 15 years of clinical use. The present work clearly shows that wear is one of the basic problems with totally replaced hips. Diamond coating of the bearing surfaces appears to be an attractive solution to improve longevity of the totally replaced hip.
全髋关节置换术中的颗粒状磨损碎屑会引起局部宿主不良反应。这种反应的极端形式，侵袭性肉芽肿病，被发现是一种独特的病症，与单纯的无菌性松动不同。全髋关节置换周围的反应性和适应性组织由局部成纤维细胞样细胞和活化巨噬细胞的增殖构成。甲基丙烯酸甲酯和高分子量聚乙烯被证明基本上是免疫惰性的植入材料，但呈小颗粒形式时可作为细胞刺激物引发局部生物反应，导致植入物松动。铬 - 钴 - 钼是最常用的金属植入材料；它坚硬且坚韧，这种金属的轴承具有部分自抛光性能。在全髋关节置换中，置换髋关节长期使用的前提是材料具有良好的生物相容性以及轴承具有足够的摩擦学性能。第三个关键问题是，轴承必须使假体 - 骨植入界面处的摩擦剪切力最小化，以适应长期存活。满足这些要求的一些方法包括氧化铝对氧化铝和金属对金属设计，以及在髋臼部件中使用高度交联的聚乙烯。为了避免传统全髋关节假体材料或涂层基于磨损的有害特性，本研究包括对非晶金刚石进行生物学和摩擦学测试。先前的实验表明，通过使用混合层或中间层可以实现四面体非晶碳涂层与基材的高附着力。发现非晶金刚石具有生物惰性，模拟器测试表明，对于传统全髋关节假体，当球或两个轴承表面都涂有无氢四面体非晶金刚石薄膜时，具有优异的磨损性能。使用这种全髋关节假体的模拟器测试表明，在相当于15年临床使用的15,000,000次测试循环后，没有可测量的磨损或可检测到的分层。本研究清楚地表明，磨损是全髋关节置换的基本问题之一。轴承表面的金刚石涂层似乎是提高全髋关节置换使用寿命的一种有吸引力的解决方案。
