EVALUATION OF DIAMOND-LIKE CARBON-COATED ORTHOPEDIC IMPLANTS

Diamond-like carbon (DLC) coatings were deposited onto austenetic stai nless steel hip implants using a saddle field source deposition system . The DLC coatings with sp(3) contents in the range 40-50% had a refra ctive index of 2.4 (lambda = 675 nm). Both in vitro and in vivo studie s were carried out to evaluate the coatings' biocompatibility. In vitr o tests included cytotoxicity cell adhesion (human fibroblasts) and mu tagenicity studies, the in vivo tests were carried out by inserting 12 x 4-mm diameter DLC-coated stainless steel cylinders into both cortic al bone and muscular tissue of sheep. Both groups of tests demonstrate d the biocompatibility of the coatings. The wear resistance of 22-mm d iameter-coated stainless steel femoral heads were evaluated in a hip, simulator and measurements were made of the volume changes of ultrahig h molecular weight polyethylene cups against the femoral heads. The co ated implants exhibited a significantly lower level of wear after 6 mi llion cycles on the simulator compared with uncoated femoral heads. Th e wear observed was comparable to that obtained with ceramic (zirconia ) femoral heads. (C) 1997 Elsevier Science S.A.