Use of an Osteoinductive Biomaterial (rhOP-l) in Healing Large Segmental Bone Defects

The use of osteoeonductive and osteoinductive biomaterials promises to become a clinically important alternative to autogenous bone grafts and allografts. Because 6 to 20 percent of patients have complaints of pain. hypersensitivity, or anesthesia related to the harvesting of iliac crest bone grafts, and three to nine percent suffer more seriolls problems (3,38,54), alternatives to autogenous bone grafting are desirable. The use of autogenous bone grafting can also be limited by lack of sufficient tissue, especially in children and patients in whom a previous graft excision has been performed. Allograft bone has been useful, but its lack of osteogenielty, greater resorption rate, and potential for immunogenicity can limit its effectiveness (l, 11.15). Transmission of the human immunodeliciency virus (HIV) in allograft bone has been reported.

Osteoconductive materials provide a scaffold for bone ingrowth, act as a space filler, and osteointegrate with surrounding bone, Calcium phosphate ceramics, in particular. have been shown to be biocompatible, nontoxic, and capable of direct bonding with bone because of the chemical similarity to components of natural bone mineral (16,17,42). The hydroxyapatite (HA) form of calcium phosphate closely resembles the bone mineral component of natural vertebrate hard tissue (9.17,27). Examples of commercially available ostroconductive bone graft substitutes include Collograft (hydroxyapatiteltricalcium phosphate particles combined with purified fibrillar collagen; Zimmer, Inc., Warsaw, IN, U.S.A.) and ProOsteon (a porous natural form of calcium phosphate derived from marine coral; Interpore Orthopaedics. Inc., Irvine, CA, U.S.A.). Osteoinductive materials provide growth factors such as bone morphogenic proteins (EMPs) and transforming growth factor-beta which promote bone formation. Recombinant bone morphogenetic proteins have been extensively proven in animal models to effectively heal large segmental defects (4,5,7,10,37), The purpose of this study was to assess the radiographic, histologic, and mechanical characteristics of new bone formation in large segmental bone defects treated with a new os.teoinductive material, recombinant human osteogenic protein..