Retrieval analysis of a hydroxyapatite-coated hip prosthesis.

A 61-year-old woman fitted with a hydroxyapatite (HA)-coated macrotexture all-purpose hip prosthesis died three weeks after implantation. The retrieved femoral and acetabular components were examined using contact roentgenograms, the back-scattered mode of the scanning electron microscope, and light microscopy. Newly formed bone was observed in the marrow spaces and along the morselized autograft bone chips, which had been surgically placed in the medullary canal at the time of implantation. New bone was observed along 10% of the HA surface of the femoral component and 20% of the acetabular component. Some bone was also observed connecting the surrounding bone chips to the HA coating. Light microscopy showed the presence of osteoid on 20% of the femoral component and on 40% of the acetabular component. HA coating on total hip prostheses appears to enhance early skeletal attachment, which may be attributed to the osteoconductive properties of the composite.