Re-evaluation of the biocompatibility of bioinert ceramics in vivo.

The affinity of bone for bioinert ceramics and stainless steel was compared using calcified bone specimens. We implanted cylinders of alumina ceramics (Al2O3), zirconia ceramics (ZrO2) and SUS-316 L stainless steel into the distal femoral epiphyses of dogs and then made observations from 4 to 96 wk post-operatively. Irregularities in the histological specimens suggested the presence of artefacts due to the insertion technique. We subsequently used screws inserted into holes tapped with a tap that had a diameter identical to the screws, and observed these implants from 4 to 96 wk after insertion. There was no detectable difference in the affinity index for all three materials from 4 to 96 wk after implantation. The affinity index was calculated as the ratio of the new bone directly adjoining the implant without any intervening fibrous membrane or bone marrow to the total length of the bone-implant interface x 100%.