Objectives The authors evaluated two bone substitutes in a posterolateral spinal arthrodesis (PSA) model in sheep: coral porites (99% calcium carbonate, Biocoral@, Inoteb, France) and a biphasic ceramic (BCP) (65% hydroxyapatite and 35% B tricalcium phosphate, Triosite@, Zimmer International). Summary of Background Data Bone substitutes would be of great interest for PSA. Previous trials began with two kinds of biomaterials: natural coralline calcium carbonate, and phosphate calcium ceramic, Methods A lumbar PSA was performed in 11 sheep (coral group) and in 9 sheep (BCP group). Sacrifice and biomechanical tests were performed after 1 year. Results A large decrease of flexibility in all directions was obtained with both coral PSA and BCP PSA similarly to autologous graft. No nonfusion case was observed. Conclusion In conditions close to the human surgery, a PSA can be obtained using either coral porites or BCP as bone substitutes.