Adjacent Segment Disease

What it is

Adjacent segment disease means new degeneration — and new symptoms — at the spinal levels directly above or below a prior fusion. A fused segment no longer moves, so the neighboring discs and joints absorb more stress with every bend and twist. Over years, that extra load can accelerate wear at those adjacent levels. It is important to distinguish radiographic adjacent segment degeneration (wear visible on imaging without symptoms, which is common) from clinical adjacent segment disease (wear that actually causes pain, radiculopathy, or myelopathy).

After cervical fusion (ACDF)

The landmark study by Hilibrand and colleagues followed 374 patients for up to 21 years after anterior cervical fusion and found that symptomatic adjacent segment disease developed at a steady rate of about 2.9% per year — predicting that roughly one in four patients would develop new disease at a neighboring level within ten years of surgery. (Hilibrand AS, et al. J Bone Joint Surg Am. 1999;81:519–528.) Notably, the authors concluded that much of this may reflect the natural history of cervical spondylosis rather than the fusion itself — the disease was coming, and the fusion did not necessarily cause it.

After lumbar fusion

In the lumbar spine, Ghiselli, Wang, and colleagues followed 215 patients for an average of 6.7 years after posterior lumbar fusion and found that 27.4% developed adjacent degeneration severe enough to elect additional surgery — most often an extension of the fusion. Their survivorship analysis predicted about 84% of patients remaining free of adjacent disease at five years and 64% at ten years. (Ghiselli G, Wang JC, et al. J Bone Joint Surg Am. 2004;86:1497–1503.)

Symptoms

Symptoms depend on which level wears out and what it compresses. In the neck, adjacent segment disease typically causes new arm pain, numbness, or weakness (radiculopathy), or — less commonly — spinal cord compression (myelopathy) with hand clumsiness or gait changes. In the low back, it usually behaves like stenosis: leg pain, heaviness, or numbness with standing and walking that eases with sitting. The telling pattern is new symptoms, often years after the original surgery healed well.

Diagnosis

MRI is the key study, showing disc degeneration, stenosis, or nerve compression at the adjacent level. Flexion-extension X-rays assess whether the adjacent segment has become unstable, and a CT can clarify bony anatomy when revision surgery is being considered. Dr. Choi reviews your original operative history alongside fresh imaging — the details of the first fusion shape every decision about the next step.

What your first visit covers

Your visit centers on confirming that the adjacent level — not the old fusion, not a new problem elsewhere — is truly driving your symptoms. Dr. Choi correlates your new symptoms with imaging, examines you, and explains in plain language what changed since your last surgery and what your options are, including the option of careful observation.

Treatment options

Many patients with adjacent segment changes do well without surgery, especially when symptoms are mild — physical therapy, activity modification, and targeted nonoperative care come first. When symptoms are significant and clearly tied to the adjacent level, surgery typically means decompressing the affected nerves and, when instability is present, extending the fusion to include the worn level. In the cervical spine, disc replacement at the adjacent level is sometimes an option to preserve motion rather than extending a fusion — clinical trials have shown lower rates of adjacent-level reoperation after disc replacement compared with fusion, which is part of why motion preservation exists as a strategy.

When a second opinion can help

New symptoms after a prior fusion sit in a difficult gray zone: is it the adjacent level, a problem with the original surgery, or something unrelated? Patients are sometimes told the only option is a much bigger fusion, or that nothing can be done. A second opinion with fresh eyes on your imaging and operative history can clarify which level is actually responsible and whether a smaller, targeted operation would suffice. Dr. Choi regularly evaluates patients with new symptoms after prior fusions elsewhere.

When to seek care promptly

Seek prompt evaluation for new weakness, hand clumsiness, gait changes, or loss of bowel or bladder control after a prior fusion — these can signal spinal cord compression or severe nerve injury that should not wait.

Frequently asked questions

What is adjacent segment disease?

Adjacent segment disease is new degeneration and new symptoms at the spinal levels directly above or below a prior fusion. Because the fused segment no longer moves, neighboring levels absorb more stress, which can accelerate wear over years.

How common is adjacent segment disease after ACDF?

In the landmark Hilibrand study, about 2.9% of patients per year developed symptomatic adjacent disease after anterior cervical fusion — roughly one in four within ten years. The authors noted much of this may reflect natural aging of the spine rather than the fusion itself.

How common is it after lumbar fusion?

In the Ghiselli and Wang study of 215 lumbar fusion patients, 27.4% developed adjacent degeneration severe enough to choose additional surgery, most often extending the fusion. About 84% remained disease-free at five years and 64% at ten years.

Does spinal fusion cause adjacent segment disease?

The honest answer is debated. Fusion increases mechanical stress at neighboring levels, but those levels were often already aging — Hilibrand's data suggested adjacent disease may largely reflect natural history. Most surgeons view it as a combination of both.

Can disc replacement prevent adjacent segment disease?

Disc replacement preserves motion at the operated level, which in theory reduces stress on neighboring segments. Clinical trials have shown lower rates of adjacent-level reoperation after cervical disc replacement compared with fusion — one reason motion preservation is considered, when appropriate, instead of extending a fusion.

What are the treatment options for adjacent segment disease?

Mild cases often respond to nonoperative care. When symptoms are significant and tied to the adjacent level, surgery usually means decompressing the affected nerves, with or without extending the fusion — or, in select cervical cases, a disc replacement at the adjacent level to preserve motion.