Lubrication of metal-on-metal hip joints: The effect of protein content and load on film formation and wear
Lubrication of metal-on-metal hip joints: The effect of protein content and load on film formation and wear
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DOI：
10.1016/j.jmbbm.2011.09.008
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发表时间：
2012-02-01
影响因子：
3.9
通讯作者：
Cann, P. M.
中科院分区：
文献类型：
--
作者：
Myant, C.;Underwood, R.;Cann, P. M.
对一系列牛血清和含蛋白（白蛋白、球蛋白）盐水溶液的润滑膜进行测量，以使CoCrMo股骨组件滑动到玻璃盘上。中心膜厚度通过光学干涉测量作为时间（恒定平均速度：0和10 mm/s）和可变平均速度（0-50 mm/s）的函数。研究了负载（5 ~ 20 N）对膜厚的影响。在膜厚测试中，通过测量接触区宽度来监测CoCrMo表面磨损痕的发展。结果表明，在静态和滑动试验中，薄膜厚度随时间的增加而增加。在静态负载测试中形成的薄膜通常在3-40 nm的范围内。含有球蛋白的溶液形成了最厚的薄膜。在滑动试验中，牛血清和白蛋白液在植入体组件上迅速形成磨损疤痕，而球蛋白溶液的磨损可以忽略不计。所有测试溶液的膜厚都随着滑动时间的增加而增加，并且比等粘性EHL模型预测的要大得多。发现膜的增加与磨损疤痕尺寸的增加有关，从而降低了接触压力。提出了一种新的润滑机制，即在滑动过程中流体经历体相分离流变，从而在入口区形成升高的蛋白质相。这种蛋白质相是一种高粘度的双相基质，它周期性地进入接触面，形成一层厚厚的保护性水凝胶膜。本研究的主要发现之一是薄膜厚度对载荷非常敏感；比EHL模型预测的要大得多。因此，MoM髋关节的膜形成非常容易受到高接触压力的影响，这可能是由于植入物的错位和边缘负荷。(C) 2011 Elsevier Ltd.版权所有。
Lubricant films were measured for a series of bovine serum and protein containing (albumin, globulin) saline solutions for CoCrMo femoral component sliding against a glass disc. Central film thickness was measured by optical interferometry as a function of time (constant mean speed: 0 and 10 mm/s) and variable mean speed (0-50 mm/s). The effect of load (5-20 N) on film thickness was also studied. The development of the wear scar on the CoCrMo surface was monitored by measuring the width of the contact zone during the film thickness tests. The results showed film thickness increased with time for both the static and sliding tests. Films formed in the static, loaded test were typically in the range of 3-40 nm. The globulin containing solutions formed the thickest films. In the sliding tests a wear scar rapidly formed on the implant component for the bovine serum and albumin fluids, negligible wear was observed for the globulin solutions. Film thickness increased with sliding time for all test solutions and was much greater than predicted by isoviscous EHL models. The film increase was found to correlate with increasing wear scar size and thus decreasing contact pressure. A new lubricating mechanism is proposed whereby during sliding the fluid undergoes bulk phase separation rheology, so that an elevated protein phase forms in the inlet zone. This protein phase is a high-viscosity biphasic matrix, which is periodically entrained into the contact forming a thick protective hydro-gel film. One of the main findings of this study is that film thickness was very sensitive to load; to a much greater extent than predicted by EHL models. Thus film formation in MoM hip joints is very susceptible to high contact pressures which might be due to implant misalignment and edge-loading. (C) 2011 Elsevier Ltd. All rights reserved.