The adjunctive effect of a binding peptide on bone morphogenetic protein enhanced bone healing in a rodent model of spinal fusion

Study Design. A prospective 8-week interventional trial employing a rat model of spinal fusion to test the effect on bone morphogenetic protein binding peptide (BBP) on rhBMP-2 induced bone healing. Objectives. To determine if the addition of BBP to the collagen sponges used as a carrier for rhBMP-2 reduces the amount of rhBMP-2 required to achieve a satisfactory clinical outcome. Summary of Background Data. Bone morphogenetic proteins (BMPs) although effective in promoting osseous growth and spinal fusion have limitations in their extensive use because of higher costs and possible adverse effects including ectopic bone formation and local inflammatory reaction, particularly in the cervical spine. Methods. Posterolateral intertransverse process spinal fusion at L4-L5 was performed in Lewis rats. Two doses of BBP (500 mu g, and 1000 mu g) were tested with or without "low dose" (1 mu g) rhBMP-2 and the results were compared with the low dose (1 mu g) rhBMP-2. Fusion was evaluated by radiology, histology, and manual palpation tests. Results. Radiology revealed significant earlier fusion with 1000 mu g BBP + 1 mu g BMP-2 combination when compared with low dose BMP-2 (1 mu g) only (P < 0.05). Manual palpation and histology at eighth week revealed higher rate of fusion with the same combination with a nearly significant difference (P = 0.057). Conclusion. Specific growth factor binding agents, such as BBP, can be compounded into carriers used in fusion procedures to decrease the dosage of BMP and possibly decrease the side effects which are most likely dose-related. This may also decrease costs and improve clinical outcomes.