Short- and long-term animal studies with a plasma-sprayed calcium phosphate-coated implant.

A commercially available hydroxyapatite (HA)-coating was investigated in a 4- and 24-week animal study. HA-coated and uncoated commercially pure (c.p.) titanium threaded implants were inserted in rabbit tibia and femur. Qualitative histology showed giant cells and macrophages around both types of implants. Histomorphometry demonstrated significantly more bone in contact to the HA-coated specimens at both follow-up periods. In contrast, bone area measurements (the amount of bone inside and/or outside the threads) revealed significantly higher percentages of bone around the uncoated c.p. titanium controls after 6 months of follow-up. The inferior amount of bone around the HA-coated implants in the longer-term perspective may relate to macrophage-induced resorption.