β-tricalcium phosphate combined with recombinant human bone morphogenetic protein-2: A substitute for autograft, used for packing interbody fusion cages in the canine lumbar spine

Abstract

The use of β-tricnlcium phosphate (β-TCP) as osteoconductive and bone morphogenetic protein-2 (BMP-2) as osteoinductive bone graft substitutes has recently gained considerable research interest in spine surgery. However, whether the combination can be extrapolated to a successful interbody spinal arthrodesis remains uncertain. In this study, β-TCP combined with recombinant human BMP-2 was examined in the canine lumbar spine model as a substitute for autograft used for packing interbody fusion cages. The discectomy and interbody cage fusion were performed at three disc spaces in 8 dogs. The examination of microradiographs and histological sections of the lumbar spine at 16 weeks postsurgery revealed three fusions in autograft group (A), three β-TCP group (B), and five in β-TCP-BMP-2 (C). The mean percentage of trabecular bone area in the cages was 51.9% in group A, 48.8% in group B and 65.6% in group C. Statistical analyses of the results could not give significance. The young animal model used in this study might suppress difference between the groups. As mentioned, however, actual data of mean percentage of trabecular bone formation and of mechanical stiffness were largest in the cages filled with β-TCP and BMP-2. In clinical settings, we expect that a cage filled with β-TCP and BMP gives beneficial effects especially for patients with poor fusion statuses.