Spinal fusion is a surgical procedure used to link together vertebrae, often because of a severely damaged disc. Discs can be damaged from rupturing, slipping, natural degeneration or injury. The damaged disc can cause severe leg and back pain and may require surgery if the pain is not relieved by conservative treatment. Pt with spondylolisthesis and spinal instability also require fusion During spinal fusion surgery, bone growth is stimulated and then used to link the vertebrae together to stop the painful movement in the area. Titanium metal screws or a titanium metal cage can be used to fuse the bone together.