Porous cups with and without hydroxylapatite-tricalcium phosphate coating - 23 matched pairs evaluated with radiostereometry

Migration wear, and presence of radiolucencies were studied in 23 marched p airs of patients operated with porous-coated acetabular cups with additiona l screw fixation. All implants had the same type of titanium fiber mesh. In each pair, one of the cups was plasma-sprayed with a coating consisting of 70% hydroxylapatite (HA) and 30% tricalcium phosphate (TCP). Radiostereome tric analysis up to 2 years after the operation revealed smaller rotations around the horizontal axis in cups with HA/TCP coating. The migration of th e cup center was not significantly influenced. Evaluation of femoral head p enetration in 12 of the matched pairs did not reveal any significant differ ence. Immediately after operation, implants with HA/TCP coating had more ce ntral radiolucencies, which, despite minimal migration, disappeared during the follow-up. The clinical results did not differ between the 2 groups. Th e findings of less tilting and diminishing radiolucencies in the cups with HA/TCP coating suggest a more complete ingrowth of bone and a better sealin g of the interface.