β-Tricalcium phosphate (β-TCP) combined with recombinant human bone morphogenetic protein-2 (BMP-2) was examined as a substitute for autograft for packing into interbody fusion cages in the canine lumbar spine model. Discectomy and interbody cage fusion were performed at three disc spaces in eight dogs. Examination of microradiographs and histological sections of the lumbar spine at 16 weeks postsurgery revealed three fusions in the autograft cages (Group A), three in the β-TCP cages (Group B), and five in the β-TCP-BMP-2 cages (Group 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. Mean percentage of trabecular bone formation and mechanical stiffness were highest in the cages filled with β-TCP and BMP-2. Combination of BMP to β-TCP may act as an osteoconductive and osteoinductive bone graft substitute in clinical spine surgery.
