Nanocomposite Therapy as a More Efficacious and Less Inflammatory Alternative to Bone Morphogenetic Protein-2 in a Rodent Arthrodesis Model

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in spine fusion has led to concerns regarding a potential accompanying inflammatory response. This study evaluates a combination therapy (TrioMatrix (R); Pioneer Surgical, Inc., Marquette, MI) comprised of a demineralized bone matrix (DBM), hydroxyapatite, and a nanofiber-based collagen scaffold in a rodent spine fusion model. Thirty-six athymic rats that underwent a posterolateral intertransverse spinal fusion were randomly assigned to 1 of 5 treatment groups: absorbable collagen sponge alone (ACS, negative control), 10 mu g rhBMP-2 on ACS (positive control), TrioMatrix (R), Grafton (R) (Osteotech, Inc., Eatontown, NJ), and DBX (R) (Synthes, Inc., West Chester, PA). Both TrioMatrix (R) and rhBMP-2-treated animals demonstrated 100% fusion rates as graded by manual palpation scores 8 weeks after implantation. This rate was significantly greater than those of the ACS, Grafton (R), and DBX (R) groups. Notably, the use of TrioMatrix (R) as evaluated by microCT quantification led to a greater fusion mass volume when compared to all other groups, including the rhBMP-2 group. T2-weighted axial MRI images of the fusion bed demonstrated a significant host response associated with a large fluid collection with the use of rhBMP-2; this response was significantly reduced with the use of TrioMatrix (R). Our results therefore demonstrate that a nanocomposite therapy represents a promising, cost-effective bone graft substitute that could be useful in spine fusions where BMP-2 is contraindicated. (C) 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29: 1812-1819, 2011