Macroporous biphasic calcium phosphate ceramics versus injectable bone substitute: a comparative study 3 and 8 weeks after implantation in rabbit bone

Macroporous biphasic calcium phosphate ceramics (MBCP) and a calcium phosph ate injectable bone substitute (IBS), obtained by the association of biphas ic calcium phosphate (BCP) ceramic granules and an aqueous solution of a ce llulosic polymer, were compared in the same animal model. The two tested bi omaterials were implanted in distal femoral osseous defects in rabbits. Qua litative and quantitative histological evaluation was performed three and e ight weeks after implantation to investigate bone colonization and ceramic biodegradation associated with the two bone substitutes. Both biomaterials expressed osteoconduction properties and supported the ap position of a well-mineralized lamellar newly-formed bone. Bone colonizatio n occurred much earlier and faster for IBS than for MBCP implants, although the respective rates of newly-formed bone after eight weeks of implantatio n did not differ significantly. For both biomaterials, ceramic resorption o ccurred regularly throughout the implantation period, though to a greater e xtent with IBS than with MBCP implants. The associated polymer in IBS produced intergranular spaces allowing body f luids to reach each BCP ceramic granule immediately after implantation, whi ch may have favored osteoblastic activity, new bone formation and ceramic r esorption. This completely interconnected open macroporosity could account for the earlier and more satisfactory bone substitution achieved with IBS. (C) 2001 Kluwer Academic Publishers.