Spinal Fusion Surgery
When Is Fusion Necessary?
Decompression surgery (which widens the nerve pathway) is often enough on its own. However, fusion may be added when:
- Your vertebrae have slipped forward or backward (spondylolisthesis)
- X-rays show that your bones move excessively when you bend forward and backward
- So much bone needs to be removed for decompression that the spine would become unstable afterward
- Your spine has a significant curvature or deformity that throws off your balance
In other words, fusion is considered when "just widening the pathway isn't enough because the bones themselves are unstable (or would become unstable after surgery)."
Guideline Criteria for Fusion
| Criterion | Specific Threshold |
|---|---|
| Slippage | 5 mm or more |
| Rotational instability | 10 degrees or more |
| Facet joint angle | Greater than 50 degrees |
| Disc height | 6.5 mm or more |
| Back pain as the main symptom | Back pain more prominent than leg pain |
| Extensive decompression needed | Bilateral decompression through a bilateral approach |
On the other hand, if none of these criteria apply (meaning instability is minimal), decompression alone typically produces good results — and you can avoid the added risks and costs of fusion.