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 cera mic coating [alumina and hydroxyapatite (HA)] obtained with a plasma-s pray technique. The HA coating was performed on titanium stems, while the alumina coating was on chromium-cobalt-molybdenum stems. The inves tigation was carried out by means of micro-area X-ray diffractometric analyses and microdiffractometric analyses at the bone-implant interfa ce. Moreover, the coating before and after implantation was analysed b y means of the conventional powder X-ray diffractometric technique. Th is study demonstrated that 1 yr after implantation in animals the newl y formed bone adjacent to the HA-coated hip prosthesis stems was miner alized as much as the pre-existing bone, while 24-64 months after surg ery in humans the newly formed bone close to the alumina-coated hip pr osthesis stems showed a lamellar and Haversian structure strongly demi neralized, probably due to the release of aluminium ions from the alum ina covering. The authors conclude that the X-ray diffraction allows t he evaluation of the structural modifications of the ceramic coating, the bone formation rate close to the coating and the chemical nature o f the particles released from the coating.