Raman spectroscopic analysis of phase-transformation and stress patterns in zirconia hip joints.

Confocal Raman piezo-spectroscopy has been used for the quantitative assessments of phase transformation and residual stresses in zirconia made artificial hip joints. This work can be considered to be a first step towards the development of a fully quantitative technique for the spectroscopic characterization of zirconia femoral heads and other zirconia parts for biomedical applications. After establishing reliable calibration procedures, Raman microprobe spectroscopy could be extended to provide quantitative assessments of zirconia metastability and microscopic stress fields along the z axis perpendicular to the joint surface. For the first time, we have directly visualized patterns of phase-transformation and related residual stresses on the very surface and along the subsurface of both in vitro tested and retrieved hip implants. These spectroscopic assessments may open a completely new perspective in understanding the micromechanical wear behavior of zirconia ceramics in biological environment and in developing new zirconia-based biomaterials with superior stability characteristics. (c) 2004 Society of Photo-Optical Instrumentation Engineers.