Zirconia-alumina: An alternative bearing for hip arthroplasty

The ZrO2-TZP BIO-HIP (R) /Al2O3 BIO-HIP (R) articulation has been investigated by wear tests and hip simulator experiments in comparison to the Al2O3 BIO-HIP (R) /Al2O3 BIG-HIP" articulation. The wear of the heads was monitored by measurement of weight, roughness, and sphericity. The measurement of sphericity deviation appears to be the most accurate method, but requires an extremely high precision of the starting product. It could be shown that the wear of the zirconia-alumina bearing is at least as low as that of the alumina-alumina bearing. A new zirconia material with better hydrothermal stability has been developed. The hydrothermal stability was investigated by observing the t -->m phase transformation by Time Resolved X-Ray Diffraction (TRXRD) in humid environment at 140 degreesC under pressure. With this material further decrease of wear especially in hard-hard articulations can be achieved.