Volumetric determination of the wear of ceramics for hip joints

Osteolysis relating to the reaction cascade to wear debris is the main cause of the failure of arthroprostheses. New materials are still under development to minimise the wear of joints and to improve in this way the performance of total joint replacements. Testing the wear performance of very low wear materials is a rather sophisticated technique. Currently, the worn volume is calculated from the weight variations of the sample, observed from wear testing. This method may be limited especially when very low weight differences are to be evaluated on high hardness, high-density materials like CoCr alloys or ceramics like alumina or zirconia. In the present work, the tribological behaviour of ceramic biomaterials like alumina, Y-TZP and alumina-zirconia composites was evaluated by a pin-on-disc apparatus under different testing conditions. The worn volume was calculated by the use of 3-D (three-dimensional) optical profilometry data. Comparison between 3-D optical profilometry and gravimetric wear data shows the better accuracy of the profilometric method in the determination of wear rate in the range of 10(-7) mm3 (mN(-1)) or lower.