Novel biomedical coatings for orthopaedic implant devices

Hydroxyapatite [Ca1o(PO)s(OH)z] is an integral part of the body found predominantly in bones and teeth which provide the main framework and structural support for vital organs. Hydroxyapatite is present in a variety of crystallinities and also substituted with small amounts of ions such as carbonate and magnesium which overall contributes to the mineral phase of bone and teeth [1 , 2]. The first biodegradable ceramic discovered and used was particulate hydroxyapatite in Paster of Paris [3] (CaS04.2HzO) followed by the discovery of hydroxyapatite in 1920's [4]. Commercialization of hydroxyapatite occurred in the 1970's [5]. Despite the resorbability of hydroxyapatite it failed to provide a load bearing function; hence titanium alloy was used as the preferred material. Titanium has since been used extensively in orthopaedic implants for knee and hip prosthesis. Commercial hydroxyapatite implants are produced by plasma spraying hydroxyapatite onto titanium alloy, TisAL4 V which fulfils the load bearing function of the implant.