VEXLPE friction studied with a multidirectional hip joint simulator using contact temperature control

Frictional torque of VEXLPE and UHMWPE acetabular liners against CoCr and ZTA femoral heads was measured with a multidirectional hip joint simulator for a wide range of diameters. Measured frictional torque varied from 1 Nm to 7 Nm. The contact temperature was estimated with a subsurface thermocouple within the liner, located near the contact surface. When the estimated contact temperature was 37 °C, the lubricant bulk temperature was 30.1 ± 1.1 °C. When the lubricant bulk temperature was 37 °C, the estimated contact temperature was 43.4 ± 1.1 °C. The custom to use 37 °C as the lubricant bulk temperature in wear testing may lead to overheating of the contact and unrealistically low wear rates, as indicated by recent studies.