Calcium-deficient apatite: a first in vivo study concerning bone ingrowth

Biphasic calcium phosphate (BCP) materials are increasingly used to restore bone loss in surgery. Calcium-deficient apatites (CDA), the precursors of BCP, are closer in structure to biological apatites and can be associated with therapeutic agents to form drug-delivery systems. The purpose of this first in vivo study of CDA was to evaluate the osteoconductive properties of two composites, consisting of 40-80 microm granules carried by a cellulose-derived polymer, used to fill critical size bone defects in rabbit femoral ends. Animals were sacrificed 2 or 3 weeks after implantation. Histomorphometric analysis of scanning electron microscopy implant surface files was performed using gray level threshold that distinguish between bone or materials (white) and noncalcified tissue (black). Quantitative results for new bone formation showed no significant differences between the composites or the implantation periods. However, nearly all of the CDA disappeared early while supporting more extensive bone colonization than biphasic calcium phosphates implanted in the same conditions.