Two-year outcome of hydroxyapatite-coated prostheses. Two femoral prostheses retrieved at autopsy.

We performed a histological study of the bone-implant interface on 2 human femurs implanted with a hydroxyapatite-coated self-locking stem for 2 years. Extensive bone formation with no intervening fibrous tissue was noted around the entire circumference of the 2 prostheses. The newly-formed bone had 2 morphotypes: an alveolar disposition with a continuous contact between bone and hydroxyapatite, and a digitiform one where distinct bony trabeculae were in contact with the ceramic coating or with the bone marrow. Partial or even total resorption of the hydroxyapatite coating was clearly identified, these areas showing bone in contact with the metal.