Bone response to hydroxyapatite-coated and commercially pure titanium implants in the human arthritic knee.

Rough and smooth commercially pure (c.p.) titanium implants and hydroxyapatite-coated (HA-C) implants were inserted in arthritic human knees and left in situ in order to compare the response of bone to these three implants. Radiographic examination alone could not determine if bone apposition had occurred. After 3 and 6 months, histomorphometric analyses of undecalcified sections, 10 microns thick, revealed a statistical significance in the amount of bone apposition to rough-surfaced and HA-C implants as compared with smooth uncoated implants. Most of the rough-surfaced c.p. titanium implants and the HA-C implants had achieved bone apposition on the order of 50%. No statistically significant differences in apposition were seen between the rough-surfaced and HA-C implants. The smooth c.p. titanium implants were mostly encapsulated in fibrous tissue.