Modelling and optimization of biotribological testing parameters on frictional heating of vitamin E blended UHMWPE with the help of statistical techniques

Abstract

It is known from previous studies that frictional temperature rise on the surfaces of artificial joints could reach high levels that make hazardous effects on surrounding tissue and lubricant around the artificial joint. For enhancement the tribological behavior of the joints, new material combinations have been tried. In this study vitamin E blended ultra-high molecular weight polyethylene (VE-UHMWPE), which is one of the new generation material, was used for acetabular inserts. These inserts were paired with CoCrMo femoral heads. For reduction of the frictional heating, testing parameters and their effects were investigated by using Taguchi method and analysis of variance. The results were analyzed by using Statistical Package for Social Science (SPSS 15.0). Also mathematical model for the temperature rise (ΔT) was developed with the help of statistical techniques.In vitro frictional heating measurements were carried out on a custom made hip joint friction experimental set-up. 0.3–0.5mm in diameter surface dimples were machined on the inner surface of acetabular insert samples. Different static loads, representing different body weights, were applied with different walking duration. Bovine calf serum was used as lubricant and different amount of bone cement (PMMA) was added in the lubricant as third body abrasive particles. Temperature rises were recorded with embedded thermocouples. The experimental results demonstrated that the surface dimples were the major factor on frictional heating, followed by applied load, amount of third body particles and time.