Reconstruction of large bone defects with calcium phosphate ceramics--an experimental study.

The aim of the present study is to evaluate the bone-defect-repairing capacity of dense hydroxyapatite compared with 40% macroporous hydroxyapatite in a weight-bearing model. The experiment consisted of the production of a relatively large mid-diaphysary defect in the left femur of 18 mongrel dogs. Cylindrical and semicylindrical hydroxyapatite implants were placed in these bone defects in order to restore continuity. The biocompatibility of implanted material has been studied physiologically, by radiographs and scintigraphs, by histology and finally by biomechanical tests. The normal weight-bearing of the operated limb restored in three weeks time. There were two mechanical failures in dense cylindric implants and two in porous cylindric implants. Radiographically, no evidence was found of degradation of porous or dense implants. Radionuclide bone imaging to assess osseous changes at the site of implants, showed intense radionuclide accumulation in all recordings of porous implants up to two years after implantation, in contrast to dense implant recordings. Histologically, there was no evidence of bioresorption. The implants were in direct contact with normal bone tissue. The pores were filled by calcified bone. There were no differences between porous and dense implants concerning the biocompatibility of hydroxyapatite.(ABSTRACT TRUNCATED AT 250 WORDS)