My surgeon has warned me that a spinal fusion can lead to degenerative changes in the rest of the spine. What does this amount to anyway?
The term adjacent segment degeneration (ASD) is used to describe changes that occur at the next vertebral level. There are any number of changes observed on X-rays. These can include disc herniation and/or a faster breakdown of the disc.

Sometimes a tiny fracture occurs in the column that supports the vertebra. This causes a condition called spondylolysis and spinal instability. Arthritic changes are also seen in the facet (spinal) joints.

Any of these changes can be referred to as signs of ASD. Studies show that increased disc pressure and load on the spine occur with fusion. The more segments fused, the greater the risk of ASD. And a more recent study from Korea also showed that pain increases and function declines when ASD occurs.

Fusion in the low back alters the axis of motion. This shift in the load placement leads to deforming forces in the spine. Disc height decreases putting more pressure on the facet joints. The joints start to thicken and form the bone spurs mentioned.

These are all degenerative changes normally seen with the aging process. But ASD accelerates or speeds up those changes. The end result can be disabling. The final outcome may be another surgery.