Bone formation and bioresorption after implantation of injectable beta-tricalcium phosphate granules-hyaluronate complex in rabbit bone defects.

The objective of this study was to evaluate the effects of a complex of beta-tricalcium phosphate (beta-TCP) granules and 3.5% hyaluronate (beta-TCP granules-HY complex) compared with a beta-TCP block, in terms of osteoconductivity and biodegradability, to determine whether this complex would be a good candidate for bone void filler. Both materials were implanted into cavities drilled in rabbit femoral condyles. New bone formation and mineral apposition rate were evaluated to analyze osteoconductivity, whereas residual beta-TCP within the defects and tartrate-resistant acid phosphatase (TRAP) cellular activity were studied for beta-TCP resorption. The results show that both the beta-TCP block and the beta-TCP granules-HY complex support bone ingrowth; however, bioresorption was rapid for beta-TCP granules-HY but weak for beta-TCP block. This biodegradation mechanism was considered to be a cell-mediated disintegration by numerous TRAP-positive giant cells. The time lag between the peak value of TRAP-positive giant cell population and that of new bone formation rate suggests that a coupling-like phenomenon could be occurring in the beta-TCP-filled bone defects. In addition, beta-TCP granules-HY complex, which is an injectable, pastelike material, has similar osteoconductive properties to beta-TCP block. Thus, this complex may be useful as a bone filler in clinical application.