Liu Feng, Fisher John, Jin Zhongmin
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK.
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK ; School of Mechanical Engineering, Xi'an Jiaotong University, PR China.
Tribol Int. 2013 Jul;63:105-114. doi: 10.1016/j.triboint.2012.05.029.
Hip joint simulators have been largely used to assess the wear performance of joint implants. Due to the complexity of joint movement, the motion mechanism adopted in simulators varies. The motion condition is particularly important for ultra-high molecular weight polyethylene (UHMWPE) since polyethylene wear can be substantially increased by the bearing cross-shear motion. Computational wear modelling has been improved recently for the conventional UHMWPE used in total hip joint replacements. A new polyethylene wear law is an explicit function of the contact area of the bearing and the sliding distance, and the effect of multidirectional motion on wear has been quantified by a factor, cross-shear ratio. In this study, the full simulated walking cycle condition based on a walking measurement and two simplified motions, including the ISO standard motion and a simplified ProSim hip simulator motion, were considered as the inputs for wear modelling based on the improved wear model. Both the full simulation and simplified motions generated the comparable multidirectional motion required to reproduce the physiological wear of the bearing . The predicted volumetric wear of the ProSim simulator motion and the ISO motion conditions for the walking cycle were 13% and 4% lower, respectively, than that of the measured walking condition. The maximum linear wear depths were almost the same, and the areas of the wear depth distribution were 13% and 7% lower for the ProSim simulator and the ISO condition, respectively, compared with that of the measured walking cycle motion condition.
髋关节模拟器已被广泛用于评估关节植入物的磨损性能。由于关节运动的复杂性，模拟器采用的运动机制各不相同。运动条件对超高分子量聚乙烯（UHMWPE）尤为重要，因为聚乙烯磨损会因轴承交叉剪切运动而大幅增加。近年来，用于全髋关节置换的传统UHMWPE的计算磨损建模有所改进。一种新的聚乙烯磨损定律是轴承接触面积和滑动距离的显式函数，多向运动对磨损的影响已通过一个因子——交叉剪切比进行了量化。在本研究中，基于步行测量的完整模拟步行周期条件以及包括ISO标准运动和简化的ProSim髋关节模拟器运动在内的两种简化运动，被视为基于改进磨损模型的磨损建模输入。完整模拟和简化运动都产生了重现轴承生理磨损所需的可比多向运动。步行周期中ProSim模拟器运动和ISO运动条件下预测的体积磨损分别比实测步行条件下低13%和4%。最大线性磨损深度几乎相同，与实测步行周期运动条件相比，ProSim模拟器和ISO条件下磨损深度分布面积分别低13%和7%。
