Bone graft extenders, substitutes, and osteogenic proteins.

A number of products that serve as a bone graft substitutes or graft extenders are currently available. Osteoconductive products provide a porous 3-dimensional structure that encourages bone ingrowth. These materials are readily resorbed by osteoclasts leading to turnover into host bone at variable rates. Some calcium phosphate products act as cements in that they are liquid upon preparation and harden at body temperature. These cements resist compressive forces but are not effective in resisting shear or torsion. Calcium sulfate resorbs more quickly than calcium phosphate and has the potential to serve as a carrier for drugs or growth factors. Preclinical studies have shown that the osteoinductive capacity of autograft and allograft bone can be improved substantially with the addition of osteogenic proteins. Although no detailed clinical studies have been reported to date, anecdotal reports of their use with and without bone graft indicate results consistent with those obtained in preclinical studies.