[New bone formation following implantation of various hydroxyapatite ceramics. Animal experiment with bore hole models of the sheep tibia].

The aim of this study was to measure new bone formation after implantation of hydroxylapatite ceramic materials compared with autogenous and allogenous cancellous bone implantations. Eight standardised bore holes, each 6 mm in diameter, were drilled in the left medial tibia of each of seven merino sheep. Seven of these holes were filled with hydroxylapatite ceramic materials: Bio-Oss, Pyrost, autogenous and deep frozen allogenous spongiosa in various sequences. The empty hole was used for comparison. Results were evaluated after fluorescent marking with calcein green 6 weeks postoperatively. The extent of new bone formation was determined by means of fluorescence microscopy, microradiography and histological sections and quantified by means of an automatic surface-measuring programme. Whilst implantation of autogenous spongiosa resulted in almost complete slicing of the defect, the holes filled with hydroxylapatite ceramic materials showed no significant difference from the empty defect. We conclude that this purely inorganic material cannot stimulate new bone formation.