A long-term study of implanted artificial hydroxyapatite particles surrounding the carotid artery in adult dogs.

In this long-term study, we implanted HAP into adult dogs using a silicone chamber attached to the carotid artery to clarify tissue reaction to HAP implantation over a long period. We designed chambers and both hemispheres of the chambers were filled with HAP particles, and were placed around both carotid arteries of seven adult dogs. The implants were removed after 150, 300, 380 days, and histological and ultrastructual examination was undertaken. We observed bone-like tissue which was formed where HAP particles were implanted. Immunohistochemical findings showed that osteocalcin and osteonectin were as positive in the bone-like tissue as in normal bone. This study suggests that biological factors from the arterial wall might play an important role in new bone-like tissue forming, and that HAP has a strong osteoconductive ability even at heterogeneous sites.