BIOLOGICAL EFFECTS OF ALUMINUM DIFFUSION FROM PLASMA-SPRAYED ALUMINA COATINGS

Plasma-sprayed alumina (Al2O3) coatings on metal stems of hip prosthes es are used to favour bone apposition on the stem without fibrous inte rposition. We tested both in vitro and in vivo in rabbits, alumina coa tings in order to evaluate the biological effect of this material on b one. Mice fibroblasts were grown on Al2O3-coated discs and time course of aluminium concentration was recorded in two phosphate and citrate buffers (pH 4 and 7) bathing the alumina coated discs. Alumina-coated cylinders were implanted into femur condyles of ten rabbits for period s of time from 1-6 months. Then, they were histologically analysed usi ng light and scanning electron microscopy, and X-ray microanalysis. Ce ll proliferation was not affected on alumina coatings compared to cont rols. In pH 4 buffer, aluminium was released from the coatings. From a period of implantation of 4-6 months an increasing demineralization p rocess took place in the bone at the coating contact. Aurine staining showed the presence of aluminium at the interface between the non-mine ralized and the mineralized bone. These results suggest that aluminium is released from alumina coatings and leads to bone demineralization at the coating contact.