I had a spinal fusion about 10 years ago. The surgeon took out the disc and used bone chips from my hip to fuse the two bones together. Now I need another fusion. This time they want to put screws and a cage filled with bone chips. Why is this necessary? The last fusion was much simpler and worked just fine.
Surgeons have tried to improve spinal fusion over the last 10 years. The goal is to reduce problems and improve fusion results. Using extra hardware helps stabilize the spine while it's healing.
You were lucky to have a good result. Many patients with bone graft fusions ended up with a failed fusion. Motion at the fusion site caused problems with spinal instability and back pain.
A bone graft is still used today. Bone removed during the operation is shaved or ground up and placed inside the cage. Bone grows around the cage giving a good, solid fusion. At the same time the cage holds the bones apart like the disc used to do.
Overall results are better in the short- and long-run. Now researchers are trying smaller incisions for spinal surgery. The goal is less damage to the soft tissues and nerves.