Aging Resistant Ceramics for Total Hip Arthroplasty

DESCRIPTION (provided by applicant): Zirconia bio-ceramics (e.g. Prozyr) have the highest toughness and strength compared to other bio-ceramics such as alumina (e.g. Biolox) or zirconia-toughened alumina (Biolox-Delta). However, as highlighted by the recent recall of St. Gobain zirconia heads, a critical need remains to develop bio-ceramics with both significantly reduced wear characteristics and reduced fracture risk in-vivo. Theoretical calculations and practical demonstration show that damage resistance in many ceramic systems has been significantly improved by imparting insurface compression. This mechanism will be employed by providing a layered composite structure to make ceramics with significantly enhanced wear resistance. A novel doping strategy will be used to improve aging resistance of zirconia. By these enhancements the investigators propose to demonstrate feasibility and merits of advanced zirconia toughened alumina (ZTA) composites as a replacement for CoCr femoral heads and currently used alumina and zirconia femoral heads. This should lead to a simultaneous dramatic reduction in wear and catastrophic failure risk, thereby addressing and eliminating one of the most important clinical problems in total-hip arthroplasty (THA). In this phase I project, the aging resistance of the zirconia will be improved by adding suitable dopants to shift the martensitic start temperature far below in-vivo temperatures. Amount of monoclinic content in the matrix measured using XRD, after autoclaving will be the indicator of the aging resistance. The strength of this aging resistant zirconia is further improved by a suitable choice of the matrix. In addition by careful design of surface compression further improvement in strength and fracture toughness can be attained. The strength and fracture toughness will be measured using ASTM protocols C-1161 and E-399. Finally, wear performance will be evaluated using pin-on-disk wear tester and compared to the performance of currently available zirconia and alumina materials used for femoral heads. The three-step characterization will establish the superior performance of ACe-TZP materials over the currently existing alumina and zirconia materials for THA.