Pseudarthrosis (Nonunion of a Fusion)

What it is

When two vertebrae are fused, the goal is for them to grow together into one solid block of bone. Pseudarthrosis (“false joint”) means that bone did not fully knit — the fusion did not completely take, leaving a small amount of motion where there should be none. It is one of the recognized risks of any fusion surgery, and several things make it more likely, including smoking, multiple levels fused at once, and certain medical conditions.

What it feels like

Some people with a pseudarthrosis have no symptoms at all and never need anything done. Others notice a return of neck pain, sometimes pain that eases with rest and worsens with activity, or symptoms related to the hardware. The fact that a fusion has not fully healed does not by itself mean you need more surgery.

How we diagnose it

Flexion–extension X-rays can show motion across a level that should be solid, and a CT scan gives the clearest picture of whether bone has bridged the gap. I pair those findings with how you actually feel, because the two do not always go together.

How we treat it

A pseudarthrosis that is not causing symptoms is often simply watched — and addressing the things that impair healing, especially stopping smoking, can help it firm up over time. When it is genuinely causing pain or instability, a revision procedure to help the level finish healing may be worthwhile. We make that decision based on your symptoms, not on the X-ray alone.

The science — for the curious

Healing a fusion is a biological process, not just a mechanical one: the body has to lay down new bone across the gap, and anything that starves that process — tobacco above all, which markedly lowers fusion rates — works against it. That is also why a pseudarthrosis is not automatically a problem to fix: if the level is stable enough and you feel well, leaving it alone is often the wiser choice than another operation.

Learn more

OrthoInfo — Cervical Spondylosis (Arthritis of the Neck): orthoinfo.aaos.org

OrthoInfo — Neck Pain: orthoinfo.aaos.org

This handout is general education about a common condition and does not replace the personalized advice we discuss in clinic. If anything here does not match what we talked about, what we talked about wins — please ask me.