Effect of motion inputs on the wear prediction of artificial hip joints

Feng Liu,John Fisher,Zhongmin Jin

doi:10.1016/j.triboint.2012.05.029

Feng Liu, John Fisher + Show 1 more

Open Access

https://doi.org/10.1016/j.triboint.2012.05.029

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Abstract

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 in vivo. 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.

Highlights

Artificial joint replacements are effective in providing normal function to many patients suffering from severe joint diseases [1]
All the rotation components given above were considered as Euler angles; the rotation transformation was performed following the sequence of flexion/ extension (FE), abduction/adduction (AA) and internal/external rotation (IER), and the rotation movements were performed on different bearing components for different cases [33]
The accumulated volumetric wear of the polyethylene cup bearings predicted with the three different motion inputs is compared in Fig. 4, as a function of the number of simulated cycles, with the wear rates being 14.0, 13.4 and 12.2 mm3 per million cycles, respectively, for the measured walking, ISO and ProSim simulator conditions

Summary

Introduction

Artificial joint replacements are effective in providing normal function to many patients suffering from severe joint diseases [1]. The joint replacement treatment has been continuously evolved, from hips and knees to other major synovial joints [2,3,4,5]. Wear debris generated mainly from the joint bearing surface accumulates in local tissues, causes adverse tissue reaction, and leads to implant fixation failure [6]. Wear-induced failure remains a major limiting factor affecting the long-term performance of the joint replacements, for younger and more active patients. Recognition of the wear issue has led to extensive wear studies to predict wear performance, understand wear mechanism and evaluate design factors [7,8,9,10]

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