Hydroxyapatite ceramic as middle ear implant material: animal experimental results.

Hydroxyapatite is the main constituent of the mineral matrix of bone. The behavior of porous and dense hydroxyapatite ceramic implants was studied in normal rat middle ears, after induced infection, and in an in vitro assay by light and electron microscopic techniques. All implants were integrated into the middle ears without signs of extrusion, and their mucosal coverings did not appear to differ fundamentally from those of normal ears. The porous hydroxyapatite became filled with fibrous tissue and bone that showed normal morphology, and there was direct bonding of the bone to the implants. Minor biodegradation was established for the porous implants. Hydroxyapatite did not affect cultured middle ear mucosa significantly in vitro. Induced infection failed to show any adverse effect on the behavior of the implants. These observations suggest that hydroxyapatite is very useful for reconstructive ear surgery.