Induced osteogenesis--the biological principle and clinical applications.

Complex orthopedic and craniofacial surgical procedures have stimulated renewed interest in the physiology of bone grafting. The experimental and clinical evidence that a nonvital implant can stimulate local host cells to become bone-forming cells (osteoinduction) is reviewed. Studies of induced osteogenesis were derived from old clinical observations of heterotopic ossification in scars and muscle. When demineralized bone is placed within soft tissues of a rat, a remarkable sequence of endochondral ossification occurs. In contrast, mineral-containing bone particles stimulate obligatory resorption by host mono- and multinucleated cells. The biochemical, endocrine, and physicochemical aspects of induced osteogenesis are actively being investigated. Present understanding of the mechanism of bone induction is discussed along with descriptions of preliminary clinical trials with allogeneic demineralized implants.