Phase Stability of Zirconia and Alumina/Zirconia Composite Heads against UHMWPE Liners in a Temperature-Controlled Hip Simulation Study
This study evaluated the wear performance of cobalt-chromium, zirconia and alumina/zirconia composite heads against moderately crosslinked ultra-high-molecular-weight polyethylene liners under different temperature conditions. A temperature control unit was utilized to allow direct cooling/heating the head components at 4, 20, 37 and 45 °C in addition to the conventional no temperature control method. Results showed that the polyethylene wear was affected by the coolant temperature. The CoCrMo and the alumina/zirconia groups had similar wear rate without temperature control, however, the CoCrMo group generated 50% more wear than the alumina/zirconia group did when the coolant temperatures were above 20 °C. The zirconia group had the lowest wear rate of the three groups in all temperature conditions. The monoclinic phase content of the zirconia heads were about 0.2 M% before the test and 6.0 M% after the test, while the X-ray diffraction remained similar before and after the test in alumina/zirconia composite heads. The current study was able to reproduce the phase transformation of zirconia ceramics as reported in some clinical retrieval reports. A temperature control feature is recommended in a wear study in order to better simulate implant wear performance under the physiological condition in human body.
Panjian Li, Kai Zhang and Clifford W. Colwell, Jr.
Y. S. Liao et al., "Phase Stability of Zirconia and Alumina/Zirconia Composite Heads against UHMWPE Liners in a Temperature-Controlled Hip Simulation Study ", Key Engineering Materials, Vols. 284-286, pp. 991-994, 2005