TRANSITION METAL IONS ACCELERATE POLYMORPHIC PHASE TRANSFORMATION IN ZIRCONIA-TOUGHENED ALUMINA ARTIFICIAL HIP JOINTS: AN IN VITRO STUDY

IntroductionFemoral heads made from zirconia-toughened alumina (ZTA) are the most advanced bioceramic available for total hip arthroplasty. ZTA's superior mechanical properties result from the polymorphic transformation of its zirconia (ZrO2) phase in the presence of a propagating crack. In vitro derived activation energies predict that several human lifetimes are needed to reach a state of significant transformation;1 but in vivo confirmation of material stability is still lacking. This investigation determined if transition metal ions might be responsible for triggering the tetragonal to monoclinic (t®m-ZrO2) phase transformation in this bioceramic.Materials and MethodsBIOLOX®delta femoral heads (CeramTec GmbH, Plochingen, Germany) were acquired and characterized for their surface monoclinic content, Vm, using Raman spectroscopy. Then they were physiologically scratched with different metals (i.e., Ti, CoCr, and Fe, n=3 each) to simulate in vivo staining as a result of acetabular shell impingement due t...