Abstract：
The role of bore and trunnion surface topography on the failure rate of total hip joint replacements due to trunnionosis is not clear despite significant variations in the design of taper components between manufacturers. Taper surface topography, along with other taper design parameters such as clearance, diameter, and assembly force, determine the initial interlock of the contacting surfaces after assembly; this has been related to relative motions that can cause fretting and corrosion at the taper interface. However, in most in-silico parametrical taper studies associated with taper micromotions, the bore and trunnion surfaces have been simplified using a flat surface and/or sinusoidal functions to mimic the surface roughness. The current study tests the hypothesis that the use of simple geometrical functions for the taper surface topography can predict the surface mechanics developed in assembled tapers. Measured and simulated surfaces of bores and trunnions were characterised using common roughness parameters and spectral density estimations. Using the same characterised surface profiles, 2D Finite Element (FE) models of CoCr alloy femoral heads and Ti alloy trunnions were developed. Models simulated assembly conditions at different resultant forces ranging from 0.5 to 4.0 kN, contact conditions were determined and associated with their topographical characteristics. Measured surfaces of bore and trunnion components comprise up to seven dominant spatial frequencies. Flattening of the trunnion microgrooved peaks was observed during the assembly of the taper. When the femoral head bore and trunnion topography were both considered a reduced number of microgrooved peaks were in contact, from 51 in an idealised taper surfaces to 35 in measured surfaces using an assembly reaction force of 4 kN. The contact points in the models developed high plastic strains, which were greater than that associated with failure of the material. Results showed that line and sine wave functions over estimate contact points at the taper interface compared to those surfaces that consider roughness and peak variation. These findings highlight the important role of modelling the full surface topography on the taper contact mechanics, as surface variations in the roughness and waviness change the performance of tapers.
摘要：
尽管制造商之间锥度组件的设计存在显着差异，但孔和耳轴表面形貌对由于耳廓病引起的全髋关节置换的故障率的作用尚不清楚。锥形表面形貌,连同其他锥度设计参数，如间隙，直径,和装配力，确定装配后接触表面的初始互锁；这与可能导致锥形界面处的微动和腐蚀的相对运动有关。然而,在大多数与锥度微运动相关的计算机参数锥度研究中，例如,已经使用平坦表面和/或正弦函数来模拟表面粗糙度来简化孔和耳轴表面。当前的研究检验了以下假设：对锥形表面形貌使用简单的几何函数可以预测组装的锥形表面力学。使用常见的粗糙度参数和光谱密度估计对钻孔和耳轴的测量和模拟表面进行了表征。使用相同的特征表面轮廓，建立了CoCr合金股骨头和Ti合金耳轴的2D有限元（FE）模型。在0.5至4.0kN的不同合力下模拟装配条件，确定了接触条件，并将其与地形特征相关联。孔和耳轴部件的测量表面包括多达七个主空间频率。在锥形的组装过程中观察到耳轴微槽峰的变平。当股骨头孔和耳轴形貌都被认为是减少数量的微槽峰接触，使用4kN的组装反作用力，从理想化的锥形表面中的51到测量表面中的35。模型中的接触点产生了高塑性应变，大于与材料失效相关的值。结果表明，与考虑粗糙度和峰值变化的那些表面相比，线和正弦波函数超过了锥形界面处的估计接触点。这些发现强调了在锥形接触力学上对完整表面形貌建模的重要作用，随着表面粗糙度和波纹度的变化，锥度的性能会发生变化。
