Interaction between living bone particles and rhBMP-2 in large segmental defect healing in the rat femur.

Orthopedic surgeons sometimes combine recombinant, human BMP-2 with autograft bone when dealing with problematic osseous fractures. Although some case reports indicate success with this off-label strategy, there have been no randomized controlled trials. Moreover, a literature search revealed only one pre-clinical study and this was in a cranial defect model. The present project examined the consequences of combining BMP-2 with particles of living bone in a rat femoral defect model. Human bone particles were recovered with a reamer-irrigator-aspirator (RIA). To allow acceptance of the xenograft as surrogate autograft, rats were administered an immunosuppressive cocktail that does not interfere with bone healing. Implantation of 200 mu g living bone particles generated a small amount of new bone and defects did not heal. Graded amounts of BMP-2 that alone provoked no healing (1.1 mu g), borderline healing (5.5 mu g), or full healing (11 mu g) were added to this amount of bone particles. Addition of BMP-2 (1.1 mu g) increased osteogenesis, and produced bridging in 2 of 7 defects. The combination of BMP-2 (5.5 mu g) and bone particles made healing more reliable and advanced the maturation of the regenerate. Bone formation with BMP-2 (11 mu g) and bone particles showed improved maturation. Thus, the combination of autograft and BMP-2 may be helpful clinically under conditions where the healing response is suboptimal. (c) 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2137-2145, 2016. Clinical significance These data support the clinical use of recombinant, human BMP-2 with autograft bone when treating large segmental osseous defects. The combination leads to greater bone formation and accelerates the maturation of the regenerate.