Verdonschot N, Vena P, Stolk J, Huiskes R
Orthopaedic Research Laboratory, University of Nijmegen, The Netherlands.
Clin Orthop Relat Res. 2002 Nov(404):353-61. doi: 10.1097/00003086-200211000-00052.
A way to prevent polyethylene wear in total hip replacements is to use metal-on-metal bearings. The cup design of these bearings may be a metal inlay in a polyethylene cup. However, these metal inlays are relatively thin and may deform on loading. The purpose of the current study was to determine whether these potential problems become actual for a realistic range of metal-inlay components having a thickness greater than 1 mm. For this purpose, the effects of thickness variation of a metal inlay in an ultrahigh molecular weight polyethylene cup were determined using three-dimensional finite element techniques. The results showed no indications for jamming of the bearing assuming a realistic inlay thickness (3-5 mm), even with a small clearance (25 microm). The metal inlay acted rigidly beyond a thickness of approximately 5 mm. Metal inlays thinner than 1.5 mm led to a considerable increase in contact area and a reduction in contact peak stress, which may be beneficial for the bearing performance. Currently, these thin liners have too many unknown characteristics and therefore the current authors recommend using rigid metal liners that have a thickness greater than 5 mm.
防止全髋关节置换中聚乙烯磨损的一种方法是使用金属对金属轴承。这些轴承的髋臼杯设计可能是聚乙烯杯中的金属镶嵌物。然而，这些金属镶嵌物相对较薄，在加载时可能会变形。本研究的目的是确定对于厚度大于1毫米的实际金属镶嵌部件范围，这些潜在问题是否会成为现实问题。为此，使用三维有限元技术确定了超高分子量聚乙烯杯中金属镶嵌物厚度变化的影响。结果表明，即使间隙很小（25微米），假设镶嵌物厚度实际（3 - 5毫米），也没有轴承卡滞的迹象。金属镶嵌物在厚度约为5毫米以上时表现出刚性。厚度小于1.5毫米的金属镶嵌物会导致接触面积显著增加和接触峰值应力降低，这可能对轴承性能有益。目前，这些薄衬垫有太多未知特性，因此本文作者建议使用厚度大于5毫米的刚性金属衬垫。
