The long-term stability of cemented total hip replacements critically depends on the lasting integrity of the bond between the cement and the bone, often referred to as fixation. In vitro assessment of fatigue behaviour of cemented acetabular, as opposed to femoral, replacements is of particular interest due to the more aggressive nature of late "loosening" found in acetabular replacements, reported to be three times that in femoral cases. Quantitative assessment of fatigue behaviour of cement fixation on acetabular side has been difficult due to the complexity of the pelvic bone geometry and the associated loading conditions.The purpose of this work was to develop a framework for in vitro assessment of fatigue integrity of cement fixation in acetabular replacements. To this end, a newly developed hip simulator was utilised, where the direction and the magnitude of the hip contact force (Bergmann et al., 2001) under typical physiological loading conditions including normal walking and stair climbing were simulated for the first time. Preliminary hip simulator experimental results seem to be consistent with those from constant amplitude fatigue tests, in that debonding at the bone-cement interface is identified as the main failure mechanism, although the numbers of cycles to failure are significantly reduced in samples tested in the hip simulator. Finite element analysis of implanted bone samples was carried out, where the effects of loading mode on the stress distribution in the cement mantle and at the bone-cement interface were evaluated. The effects of model geometry on the stress state and failure modes were also examined and discussed based on the results of the present and previously published work.

中文翻译：

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骨水泥髋臼置换术中的疲劳


骨水泥全髋关节置换术的长期稳定性关键取决于骨水泥和骨头之间粘合的持久完整性，通常称为固定。与股骨替代物相比，骨水泥髋臼疲劳行为的体外评估特别令人感兴趣，因为髋臼替代物中发现的晚期“松动”更具侵略性，据报道是股骨替代物的三倍。由于骨盆几何形状和相关负载条件的复杂性，对髋臼侧骨水泥固定的疲劳行为进行定量评估一直很困难。这项工作的目的是开发一个体外评估髋臼侧骨水泥固定疲劳完整性的框架。髋臼置换术。为此，采用了新开发的髋部模拟器，首次模拟了正常行走和爬楼梯等典型生理负荷条件下髋部接触力的方向和大小（Bergmann等，2001）。髋关节模拟器的初步实验结果似乎与恒幅疲劳测试的结果一致，骨水泥界面处的脱粘被认为是主要的失效机制，尽管在髋关节测试的样品中失效的循环次数显着减少模拟器。对植入骨样品进行有限元分析，评估加载模式对水泥罩和骨水泥界面应力分布的影响。还根据当前和之前发表的工作结果检查和讨论了模型几何形状对应力状态和失效模式的影响。