BACKGROUND: The authors have studied the porosity, pore size, mechanical strength, in vitro biological activity,ectopic osteogenic activity of porous biphasic calcium phosphate enhanced by recombinant bone morphogenetic protein-2/silk fibroin sustained-release microsphere (BCP/rBMP-2/SF). However, further investigation on the osteogenic ability of the composite bone graft material is warranted based on a reliable animal model, which will provide experimental data for the clinical application of the composite material in the spinal fusion.OBJECTIVE: To investigate the osteogenic efficacy of BCP/rBMP-2/SF in a sheep lumbar interbody fusion model.METHODS: Sixteen healthy adult sheep were divided into two groups randomly. All sheep were operated on the left extraperitoneal approach and intervertebral discs of L1/2, L3/4, and L5/6 were exposed respectively. Three of the following four materials were randomly implanted into the L1/2, L3/4, and L5/6 of each animal: autologous iliac, BCP/rhBMP-2/SF,BCP/rhBMP-2 or BCP/SF.RESULTS AND CONCLUSION: The group of BCP/SF/rhBMP-2 achieved a similar fusion rate compared with the group of autologous iliac at 12 and 24 weeks after operation, and they were significantly better than the other two groups. These findings indicate that the novel new artificial bone, BCP/rhBMP-2/SF, can obtain similar lumbar fusion results compared with the autologous iliac. It is expected to be applied to clinical practice in the future by further improving its properties.