Loss of hydroxyapatite coating on retrieved, total hip components.

The goal of this study was to examine the early retrievals of hydroxyapatite-(HA) coated hip prostheses to assess evidence of osteoconductivity, resorption of HA, and the integrity of the HA/implant bond. Six retrieved HA-coated hip prostheses (3 femoral hip stems, 3 acetabular cups) were analyzed for the amount of bone ongrowth or ingrowth of the HA-coated surface and the extent to which the coating was still present after in vivo service. The examination of these six HA-coated prostheses indicates that HA appeared to be osteoconductive. There was evidence of debonding of HA from the smooth-surfaced femoral prosthesis, although that may have been a result of the extraction process. The five plasma-spray surfaced, HA-coated prostheses showed evidence of considerable loss of the HA coating at the time of receipt in the authors' laboratory, although it is was not possible to determine the cause of the loss of coating.