Evaluation of human bone morphogenetic protein 2 in a canine spinal fusion model

The efficacy of purified recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in a porous biodegradable copolymer, poly [D,L (lactide--coglycide)] (PLGA) was evaluated using a canine posterior segmental spinal fusion model. rhBMP-2/PLGA was compared to autogenous cancellous bone and to PLGA alone. Thirty three fusion sites in 11 beagle dogs were evaluated at 12 weeks for union and mechanical strength. Union score and mechanical testing showed no difference between autogenous cancellous bone and rhBMP-2/PLGA. Union scores for autogenous cancellous bone and rhBMP-2/PLGA sites were superior to those with PLGA alone (p = 0.001 and p = 0.0007, respectively). These findings suggest that synthetic bone graft substitute materials delivering purified rhBMP-2 may be suitable for posterior spinal fusions. The use of such materials may provide efficacy equivalent to autogenous cancellous bone and avoid the morbidity associated with the harvest of autogenous graft.