Long-Term Risks of Spinal Fusion

What Is Adjacent Segment Disease (ASD)?

Years after lumbar fusion surgery, some patients develop new pain or nerve compression at the levels immediately above or below the fused segment. This is called adjacent segment disease, or ASD for short.

How It Happens

  • Fusion surgery locks the vertebrae together with screws and rods, making them immovable
  • Because the fused segment can no longer move, the levels above and below must compensate by moving more
  • Over years of extra stress:
    • The disc (cushion) at those neighboring levels wears down faster
    • The nerve pathway may narrow again
    • The vertebrae may begin to slip (spondylolisthesis)

Adjacent segment disease: healthy disc above fusion degenerates over time due to extra stress

Think of it this way: Imagine a three-drawer dresser where the middle drawer has been nailed shut. Now the top and bottom drawers get pulled open and pushed closed more than before. Over time, the rails and frames of those remaining drawers wear out faster — because they're doing extra work.