LONG-TERM HISTOLOGICAL-EVALUATION OF HYDROXYAPATITE CERAMICS IN HUMANS

We have investigated the interface between bone and hydroxyapatite (HA ) chronically implanted in man. By light microscopy, HA appeared to bi nd directly to bone without intervening fibrous tissue. By transmissio n electron microscopy, two patterns were noted: (1) HA either bound di rectly to bone; or (2) electron-dense material intervened between HA a nd bone. The orientation of bone collagen fibres likewise showed two p atterns: (1) collagen fibres were oriented parallel to the HA; or (2) the fibres were aligned perpendicularly. We have observed similar bind ing properties of HA to the jaw bone of humans in vivo and in vitro.