Static coefficient of friction between Ti-6Al-4V and PMMA for cemented hip and knee implants.

The static coefficient of friction between Ti-6Al-4V and PMMA was determined experimentally. A microtopographic surface analysis of the Ti-6Al-4V and PMMA specimens used in the experiments was performed to characterize the surfaces. The coefficient of friction between Ti-6Al-4V and PMMA in both dry and wet conditions, using both Ringer's solution and bovine serum, was determined by the standard inclined plane test, following the ASTM 4516-91 method, and by a prototype computerized sliding friction tester. The effects of surface roughness and of contact pressure on the coefficient of friction also have been investigated. Tests were performed at 26 degrees C and at body temperature of 37 degrees C. Considering all the tests, the overall range of the mean coefficients of friction varied between 0.17 and 0.32 in dry or wet conditions. For the same surface roughness in contact, in general the coefficient of friction using Ringer's solution was slightly lower than it was in dry conditions whereas bovine serum had a very high surface tension, which significantly increased the static coefficient of friction.