WEAR AND FRICTION CHARACTERIZATION OF MATERIALS FOR HIP PROSTHESIS

摘要

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 the wear and the friction of different materials used for the friction parts of hip prosthesis. Currently, the materials used are metallic alloys (stainless steel or cobalt-chromium alloys), ultra-high molecular weight polyethylene (UHMWPE) and ceramics (based on alumina or zirconia). In this study, we carried out tribological tests with different bearing pairs (metallic alloys/UHMWPE, ceramics/UHMWPE and ceramics/ceramics) and we compared their behavior in terms of friction, wear scars morphology and wear debris. 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. This versatility concerns the motion, which can be set between alternative rotation (minimum stroke of +/- 0.5°) to continuous rotation, the temperature which can be controlled between room temperature up to 500°C, and the contact pressure which can be adjusted, by modifying the specimens' geometry, from MPa to some GPa ranges. The normal load is applied by two pneumatic jacks in the range 1000N-5000N. The two samples are immersed in a biological environment (calf serum) maintained at 37°C.