X-RAY-DIFFRACTION OF NEWLY FORMED BONE CLOSE TO ALUMINA-COATED OR HYDROXYAPATITE-COATED FEMORAL STEM

The study was focused on the bone tissue response to two types of ceramic coating [alumina and hydroxyapatite (HA)] obtained with a plasma-spray technique. The HA coating was performed on titanium stems, while the alumina coating was on chromium-cobalt-molybdenum stems. The investigation was carried out by means of micro-area X-ray diffractometric analyses and microdiffractometric analyses at the bone-implant interface. Moreover, the coating before and after implantation was analysed by means of the conventional powder X-ray diffractometric technique. This study demonstrated that 1 yr after implantation in animals the newly formed bone adjacent to the HA-coated hip prosthesis stems was mineralized as much as the pre-existing bone, while 24-64 months after surgery in humans the newly formed bone close to the alumina-coated hip prosthesis stems showed a lamellar and Haversian structure strongly demineralized, probably due to the release of aluminium ions from the alumina covering. The authors conclude that the X-ray diffraction allows the evaluation of the structural modifications of the ceramic coating, the bone formation rate close to the coating and the chemical nature of the particles released from the coating.