Influence of hip joint simulator design and mechanics on the wear and creep of metal-on-polyethylene bearings.

Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing.

髋关节模拟器被广泛用于髋关节置换的临床前测试。全球范围内模拟器设计和测试条件的差异会影响聚乙烯的摩擦学性能。本研究的目的是评估模拟器的力学和设计对超高分子量聚乙烯磨损和蠕变的影响。在本研究的第一部分，使用一个机电模拟器和一个气动模拟器在相同的标准步态条件下比较金属对聚乙烯部件的磨损和蠕变。在研究的第二部分，使用同一个机电髋关节模拟器来研究运动学对磨损的影响。与气动模拟器相比，机电模拟器观察到更高的磨损率和穿透深度。当在步态周期中引入内收/外展时，其磨损与没有内收/外展的步态周期条件下获得的磨损没有显著差异。本研究证实了髋关节模拟器设计和加载条件对聚乙烯磨损的影响，因此应避免直接比较不同髋关节模拟器之间的绝对磨损率。本研究还证实，产生的磨损路径是获得临床相关磨损率的关键因素，并且这可以通过两轴或三轴旋转来实现。然而，三轴旋转（包括内收/外展）更接近地模拟临床条件，因此应该是用于临床前测试的新开发髋关节模拟器的设计方法。