Wear and friction characterization of materials for hip prosthesis

Many problems which lead to the loosening of a prosthesis are due to the wear of materials used for the substitution of the articulation. Wear reduces the lifetime of a prosthesis, induces the formation of potentially harmful debris and involves the risks of a new surgical operation. The goal of this study, carried out in the laboratory, is to quantify wear and friction of different materials used for the friction parts of hip prosthesis. Currently, the materials used are metallic alloys, ultra-high molecular weight polyethylene (UHMWPE) and ceramics. In this study, we carried out tribological tests with different couples (metallic alloys/UHMWPE, ceramics/UHMWPE and ceramics/ceramics) and we compared their behavior in terms of friction and wear scars morphology. The used ceramics are composed of alumina and zirconia which are produced by an original process. To carry out the tribological tests whose conditions are defined by international standards, a versatile tribometer has been developed. The results show a lower friction coefficient in the case of ceramics/ceramics couples than in the case of metallic alloys/UHMWPE couples. We also studied the wear surfaces by profilometry and electron microscopy. The wear of UHMWPE is very low when in contact with ceramics, low with Co–Cr alloy and high with stainless steel. Our ceramics/ceramics couples show no wear.