Evaluation of diamond-like carbon-coated orthopaedic implants

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