Spinal fusion is a surgical technique in which one or more of the vertebrae of the spine are joined together (fused) to stop them from moving against each other. This is done by placing bone grafts or bone graft substitutes between the affected vertebral bone. The graft material acts as a binding medium and also helps to maintain normal disc height – as the body heals, the vertebral bone and bone graft eventually grow together to join the vertebrae and stabilize the spine.