Bone Morphogenetic Protein in Spinal Fusion

Bone Morphogenetic Protein in Spinal Fusion
The widespread use of fusion procedures in the management of spinal disorders has led investigators to explore the use of growth and differentiation factors in such procedures. As an adjuvant to allograft bone or as a replacement for harvested autograft, bone morphogenetic proteins (BMPs) appear to improve fusion rates after spinal arthrodesis in both animal models and humans, while reducing the donor-site morbidity previously associated with such procedures. The use of recombinant genetic technology in the production of BMP has improved the efficiency, cost effectiveness, and safety of producing and using such materials. Recombinant human BMP-2 (rhBMP-2), as one of the first factors identified in the process of endochondral bone formation, has been extensively researched over the past decade. The efficacy and dose profile of this differentiation factor in the context of various carrier substrates has been investigated. Based on the encouraging results of preliminary studies, the future role of rhBMP-2 may lie in its replacement of autologous bone grafting and, consequently, the reduced need for instrumented fixation, while concurrently improving over-all fusion rates. The authors provide an overview of BMP and review its use in clinical and laboratory settings.

Over 30 years ago, Marshall Urist and colleagues identified a group of protein extracts, derived from the ground substance of mature bovine bone, capable of inducing both cartilage and bone formation when implanted into the soft tissues of study animals. Aptly named BMPs by Urist, these glycoproteins comprise a subset of the transforming growth factor-family of related growth and differentiation factors. Of the more than 20 BMPs isolated to date, six appear to be structurally related to each other and capable of initiating the process of endochondral bone formation. The presence of such factors within the matrix of mature bone indicates a likely role in the regeneration and remodeling of bone structures after injury or repetitive stresses.