Bartel D L, Bicknell V L, Wright T M
J Bone Joint Surg Am. 1986 Sep;68(7):1041-51.
Debris resulting from damage to the surface of polyethylene components of total joint replacements has previously been shown to contribute to long-term problems such as loosening and infection. Surface damage has been associated with fatigue processes due to stresses arising from contact between the metal and polyethylene components in these prostheses. In the present study, we used elasticity and finite-element solutions to determine these stresses for total hip replacements with head diameters of twenty-two and twenty-eight millimeters and for a condylar total knee replacement. We also examined the effect on these stresses of using carbon-fiber-reinforced polyethylene instead of plain polyethylene. Stresses associated with surface damage in the tibial component of the total knee replacement were much larger than those in the hip replacements. The analysis of contact stress as a function of thickness of the polyethylene insert for tibial components showed that a thickness of more than eight to ten millimeters should be maintained when possible. The contact stress in the tibial components was reduced most when the articulating surfaces were more conforming in the medial-lateral direction. Contact stresses were much less sensitive to changes in geometry in the anterior-posterior direction. For the hip components, the stresses were lower in the acetabular component of the twenty-eight-millimeter hip replacement than in the twenty-two-millimeter replacement. The use of carbon-fiber-reinforced polyethylene resulted in stresses that were higher by as much as 40 per cent. Because the contact area between articulating surfaces moves during flexion, portions of the surface will be subjected to cyclic stresses. The contact area for the knee replacements in flexion was smaller than for the hip replacements, and the range of the maximum principal stress was larger. Consequently, the combination of the higher stress and the moving contact area is more likely to cause surface damage due to fatigue in tibial components than in acetabular components, which is consistent with clinical observations.
全关节置换中聚乙烯部件表面损伤产生的碎屑先前已被证明会导致诸如松动和感染等长期问题。表面损伤与疲劳过程有关，这是由于这些假体中金属和聚乙烯部件之间的接触产生的应力所致。在本研究中，我们使用弹性和有限元解决方案来确定头部直径为22毫米和28毫米的全髋关节置换以及髁型全膝关节置换的这些应力。我们还研究了使用碳纤维增强聚乙烯而非普通聚乙烯对这些应力的影响。全膝关节置换胫骨部件中与表面损伤相关的应力远大于髋关节置换中的应力。对胫骨部件聚乙烯衬垫厚度与接触应力关系的分析表明，应尽可能保持厚度超过8至10毫米。当关节面在内外侧方向上更贴合时，胫骨部件中的接触应力降低最多。接触应力对前后方向几何形状变化的敏感度要低得多。对于髋关节部件，28毫米髋关节置换髋臼部件中的应力低于22毫米置换中的应力。使用碳纤维增强聚乙烯导致应力高达40%。由于关节面之间的接触面积在屈曲过程中会移动，表面的某些部分将承受循环应力。膝关节置换屈曲时的接触面积小于髋关节置换，最大主应力范围更大。因此，较高的应力和移动的接触面积相结合，比髋臼部件更有可能导致胫骨部件因疲劳而出现表面损伤，这与临床观察结果一致。
