Bone morphogenetic protein-7: Review of signalling and efficacy in fracture healing

Bone morphogenetic proteins (BMPs) are a group of signalling molecules that belong to the transforming growth factor-β superfamily of proteins. Initially identified for their ability to induce bone formation, recent advances in the understanding of cellular and molecular mechanisms regarding BMPs have led to the use of the growth factor to accelerate bone healing. Recent clinical trials have demonstrated that BMPs, BMP-7 in particular, may present an alternative line of treatment other than the gold standard, autogenous bone grafting, in the treatment of fracture nonunion. We performed a literature search in September 2014 of PubMed and Embase using search terms, including "bone morphogenetic proteins", "BMP-7", "non-union", "fracture healing" and "cost-effectiveness", reviewing the efficacy, safety, and cost of treatment of nonunions with BMP-7. The authors further canvassed the reference lists of selected articles and used online search tools, such as Google Scholar. BMP-7 uses both the canonical and noncanonical signalling pathways. The treatment of fracture nonunion with recombinant human BMP-7 (rhBMP-7) has a comparable efficacy with that of autogenous bone grafting with an average union rate of 87% compared with 93% for bone grafting. Furthermore, fewer complications have been described with the use of rhBMP-7 compared with traditional bone grafting. We describe the signalling pathways that BMP-7 uses to exert its effect on bone. In nonunions, rhBMP-7 has been shown to have a similar efficacy to bone grafting with fewer complications.