Does Spinal Fusion Cause Problems at Adjacent Levels?

Research-informed explainer — last updated April 12, 2026

Yes — and the risk is larger than most patients are told before surgery. Research tracking patients for up to ten years after spinal fusion found that more than one in four developed significant new problems at the vertebral levels immediately bordering the fused segment. Understanding this risk, and knowing what questions to ask your surgeon beforehand, is one of the most important things you can do before agreeing to fusion.

This article draws on research from three spine surgeons in the Convene directory. Gregory Carlson at Providence Mission Hospital co-authored the landmark 1999 study in the Journal of Bone and Joint Surgery that tracked cervical fusion patients for a decade and documented symptomatic adjacent-segment disease in more than 25% of cases — one of the most widely cited findings in spine surgery, with over 1,600 citations. He also published research on lumbar adjacent-segment stenosis and the technical challenges of fusing a segment next to a prior fusion. Jourdan Cancienne has published extensively on revision surgery rates following spinal deformity surgery in older patients, drawing on large national databases. Adam Shimer at UVA Health is a tenured professor of orthopaedic surgery and spine fellowship director whose research on patient-reported outcome measures and long-construct fusion failures informs how surgeons track whether these operations are actually succeeding.

What is adjacent-segment disease?

When surgeons fuse two vertebrae together, they eliminate motion at that spinal level. The hardware and bone graft hold those vertebrae rigid — which is exactly the point. But the discs and joints above and below the fused segment must now absorb all the load and movement that used to be shared across a longer span of spine.

Over time, that extra mechanical stress accelerates wear at the neighboring levels. This process is called adjacent-segment degeneration when it shows up on imaging, and adjacent-segment disease (ASD) when it produces actual symptoms — pain, nerve compression, weakness, or difficulty walking.

The distinction matters. Many patients will develop new radiographic changes at adjacent levels without ever feeling them. ASD refers specifically to the subset who develop clinical problems serious enough to affect their lives or require further treatment.

What the research shows

The Carlson study, published in the Journal of Bone and Joint Surgery in 1999, followed patients who had undergone anterior cervical fusion — a common surgery to treat neck pain, arm pain, or weakness caused by a compressed nerve or spinal cord [1]. The findings were stark: symptomatic adjacent-segment disease developed in more than one-fourth of all patients within ten years of their cervical fusion. These weren't minor imaging findings — the patients developed radiculopathy (radiating arm pain and nerve symptoms) or myelopathy (spinal cord compression affecting balance, coordination, and strength) at the levels next to their original fusion.

For lumbar spine, Carlson's subsequent research tracked 33 consecutive patients who needed surgery for spinal stenosis at lumbar segments adjacent to a previous lumbar fusion [3]. The mean interval between the original fusion and the adjacent-segment surgery was 94 months — nearly eight years. Of those patients who were followed long-term, only about half rated their second operation as completely satisfactory. This is an important finding: once adjacent-segment disease progresses to the point of needing reoperation, the surgical outcomes are more uncertain than the original procedure.

Why it happens: the biomechanics

The spine is engineered to distribute load across multiple levels simultaneously. Each disc acts as a shock absorber, and each facet joint guides motion. When you fuse one segment, you're essentially removing a link from the chain.

The segment immediately above and below a fusion must now move more — compensating for what the fused level used to do. Over years, that increased motion and load accelerates the normal aging process at those neighboring discs and joints. The more levels fused, the greater the biomechanical disruption, and the higher the stress placed on the adjacent levels.

This isn't a surgical complication in the traditional sense — the fusion itself may be technically perfect. It's a downstream consequence of the mechanical changes the surgery creates. Some degree of adjacent-level stress is essentially unavoidable after fusion.

Cervical versus lumbar: different risk profiles

Cervical spine (neck): The 1999 Carlson data focused on cervical fusion and documented the highest rates of symptomatic adjacent-segment disease — more than 25% at ten years. Single-level fusions at C5-C6 (the level where most cervical disc disease occurs) and pre-existing degeneration at neighboring levels were identified as the strongest risk factors for future adjacent-level problems.

Lumbar spine (lower back): Lumbar ASD is also well-documented, though the timeline can be longer because lumbar discs are larger and more load-bearing. The additional complication in the lumbar spine is that extending a fusion — adding levels to address adjacent-segment disease — is technically demanding. Research by Carlson and others has shown that fusion adjacent to a prior fusion has lower success rates and a higher reoperation risk than the original surgery [2].

For patients with adult spinal deformity requiring fusions of eight or more levels, Cancienne's research using large national databases found that revision surgery rates in elderly patients are substantial, with multiple comorbid conditions and deformity severity independently predicting reoperation [4].

Who is at highest risk

Not every fusion patient develops adjacent-segment disease. The research identifies several factors that increase the odds:

• More levels fused. The more segments included in the fusion construct, the greater the biomechanical burden on the levels at each end. Long fusions for deformity carry higher adjacent-level stress than single-level fusions.
• Pre-existing degeneration at neighboring levels. If the disc above or below your planned fusion already shows wear on MRI before surgery, it has less reserve capacity to handle the added load. The Carlson data identified this as one of the two strongest predictors of future ASD.
• Single-level fusion at a high-motion segment. C5-C6 in the cervical spine is the most mobile level in the neck; fusing there shifts stress to C4-C5 and C6-C7, both of which are already common sites for disc disease.
• Older age at time of fusion. Patients who are older when they undergo fusion have less biological capacity to remodel and adapt to changed load distribution. Cancienne's work on elderly spinal deformity patients documents how revision rates climb with age [4].
• Obesity and osteoporosis. Both increase mechanical stress on hardware and adjacent structures, accelerating the degeneration process.

The reoperation burden

One reason adjacent-segment disease matters so much is where it leads. When ASD becomes symptomatic enough — nerve pain, weakness, difficulty walking — many patients end up needing a second operation to decompress or fuse the adjacent level. That second operation is technically harder than the first, carries its own risks, and often has less predictable outcomes.

The practical implication is that fusion isn't always a one-time event. For a subset of patients — the data suggests at least one in four over a decade — spinal fusion sets in motion a process that leads to further surgery at a neighboring level years later.

Motion-preservation surgery: is it an option for you?

One of the most important developments in spine surgery over the past two decades is the availability of motion-preserving alternatives to fusion — specifically, artificial disc replacement (ADR), also called cervical disc arthroplasty in the neck or lumbar total disc replacement in the lower back.

Instead of eliminating motion at a diseased segment, artificial disc replacement preserves it. The degenerated disc is removed and replaced with a prosthetic device that continues to allow movement. Because the segment remains mobile, it doesn't shift excess load to the adjacent levels in the same way a fusion does.

Studies comparing cervical disc replacement to anterior cervical fusion have shown lower rates of adjacent-segment reoperation in the disc replacement group at medium-term follow-up. ADR is not appropriate for every patient — it requires sufficient bone quality, no significant deformity, and an appropriate pattern of disc disease — but for eligible patients with single or two-level cervical or lumbar disc disease, it is worth asking about explicitly.

Questions to ask before agreeing to fusion

• Is artificial disc replacement an option for my specific problem? Ask your surgeon directly, and if they don't perform ADR, ask whether a second opinion from a surgeon who does is worth getting.
• How many levels are being fused? More levels means higher adjacent-segment stress. If multiple levels are being proposed, ask why all of them are necessary.
• What does my imaging show at the levels adjacent to the proposed fusion? If those discs are already showing degeneration, your risk of symptomatic ASD is higher, and that should factor into the decision.
• What is your experience with revision surgery for adjacent-segment disease? If you do develop ASD and need further surgery, will this surgeon be able to handle it?
• What would happen if I delayed or avoided surgery? For some patients, symptoms can be managed with physical therapy, injections, or activity modification. Understanding the natural history of your condition without surgery is essential context for weighing the long-term risks of fusion.

The bottom line

Adjacent-segment disease is real, it is not rare, and the decision to undergo spinal fusion should include an honest conversation about it. The landmark research tracking cervical fusion patients for a decade found symptomatic problems at adjacent levels in more than one in four patients — a finding that has been replicated and extended to the lumbar spine as well. The biomechanical reason is straightforward: fusing one segment forces the neighboring levels to compensate, accelerating their wear over time. Risk is higher with more levels fused, pre-existing degeneration at adjacent levels, and older age. For appropriate patients, motion-preserving alternatives like artificial disc replacement may reduce this downstream risk. Before agreeing to any spinal fusion, ask your surgeon directly about adjacent-segment disease, what your personal risk factors are, and whether you are a candidate for motion-preservation surgery.