Department of Materials Science and Engineering, The University of Sheffield, Sheffield, UK.
Acta Biomater. 2012 Jul;8(6):2348-59. doi: 10.1016/j.actbio.2011.12.037. Epub 2012 Feb 13.
The performance of total hip-joint replacements depends strongly on the state of lubrication in vivo. In order to test candidate prosthetic materials, in vitro wear testing requires a lubricant that behaves in the same manner as synovial fluid. The current study investigated three lubricants and looked in detail at the lubrication conditions and the consequent effect on ball-on-flat reciprocating wear mechanisms of Biolox®delta against alumina. Biolox®delta, the latest commercial material for artificial hip-joint replacements, is an alumina-matrix composite with improved mechanical properties through the addition of zirconia and other mixed oxides. Three commonly used laboratory lubricants, ultra pure water, 25 vol.% new-born calf serum solution and 1 wt.% carboxymethyl cellulose sodium salt (CMC-Na) solution, were used for the investigation. The lubrication regimes were defined by constructing Stribeck curves. Full fluid-film lubrication was observed for the serum solution whereas full fluid-film and mixed lubrications were observed in both water and the CMC-Na solution. The wear rates in the CMC-Na and new-born calf serum were similar, but were an order of magnitude higher in water. The worn surfaces all exhibited pitting, which is consistent with the transition from mild wear to severe or "stripe" wear. The extent of pitting was greatest in the serum solution, but least in the water. On all worn surfaces, the zirconia appeared to have fully transformed from tetragonal to monoclinic symmetry. However, there was no evidence of microcracking associated with the transformed zirconia. Nevertheless, AFM indicated that zirconia was lost preferentially to the alumina grains during sliding. Thus, the current study has shown conclusively that the wear mechanisms for Biolox®delta clearly depend on the lubricant used, even where wear rates were similar.
全髋关节置换的性能在很大程度上取决于体内的润滑状态。为了测试候选假体材料，体外磨损测试需要一种具有与滑液相同行为的润滑剂。本研究调查了三种润滑剂，并详细研究了 Biolox®delta 对氧化铝的球盘往复式磨损机制的润滑条件和随之而来的影响。Biolox®delta 是最新的人工髋关节置换商业材料，是一种氧化铝基复合材料，通过添加氧化锆和其他混合氧化物来提高机械性能。三种常用的实验室润滑剂，超纯水、25vol.%新生小牛血清溶液和 1wt.%羧甲基纤维素钠盐（CMC-Na）溶液，用于该研究。通过构建 Stribeck 曲线来定义润滑状态。血清溶液中观察到全流体膜润滑，而在水和 CMC-Na 溶液中观察到全流体膜和混合润滑。在 CMC-Na 和新生小牛血清中的磨损率相似，但在水中要高一个数量级。所有磨损表面都显示出点蚀，这与从轻度磨损到严重磨损或“条纹”磨损的转变一致。血清溶液中点蚀的程度最大，但在水中最小。在所有磨损表面上，氧化锆似乎已经完全从四方相转变为单斜相。然而，没有证据表明与转化的氧化锆相关的微裂纹。尽管如此，AFM 表明，在滑动过程中，氧化锆优先从氧化铝晶粒中丢失。因此，本研究明确表明，即使磨损率相似，Biolox®delta 的磨损机制也明显取决于所使用的润滑剂。
