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Spine·2026·Retrospective cohort
Adjacent Segment Disease
Accelerated degeneration at spine levels adjacent to a prior fusion
ICD-10: M47.816 · systemic condition
Adjacent segment disease (ASD) occurs when the disc, facet joints, or other structures at the spinal levels immediately above or below a prior fusion undergo accelerated degeneration. Spinal fusion eliminates motion at the fused segment, transferring increased mechanical stress to the adjacent unfused levels — a process that can gradually damage those levels. ASD is an increasingly recognized long-term complication of lumbar and cervical fusion, with radiographic evidence appearing in 30–50% of patients at 5 years, though clinically symptomatic ASD is less common. The condition may cause new or recurrent pain, radiculopathy, or myelopathy years after a successful initial fusion.
30–50%
Radiographic adjacent segment degeneration occurs in approximately 30–50% of patients within 5 years of lumbar fusion, though clinically symptomatic ASD requiring treatment affects roughly 15–25% over 10 years.
Park P et al., Spine (2004)9%
The annual incidence of symptomatic adjacent segment disease after lumbar fusion is approximately 2.5–3.9% per year.
Ghiselli G et al., Journal of Bone and Joint Surgery (2004)Symptoms
- New or recurrent back or neck pain emerging months to years after a prior fusion
- Radiculopathy (arm or leg pain/numbness/weakness) at a different level than the original fusion
- Cervical myelopathy symptoms (clumsiness, gait disturbance) if above a cervical fusion
- Decreased walking tolerance or neurogenic claudication
- Mechanical pain that worsens with movement and improves with rest
Causes & Risk Factors
- Biomechanical stress transfer — fusion eliminates motion, forcing adjacent levels to absorb increased load
- Pre-existing degeneration at adjacent levels accelerated by altered mechanics
- Disruption of posterior ligamentous complex during original surgery
- Long fusion constructs — more levels fused = higher adjacent segment stress
- Patient factors: age, BMI, osteoporosis, and pre-operative disc health
Imaging Findings
Imaging studies are commonly used to identify findings associated with this condition. Results vary by individual; a qualified spine specialist interprets findings in the context of a full clinical evaluation.
MRI
- Disc desiccation and signal loss at levels immediately above or below the fusion mass
- Disc herniation or protrusion at the adjacent segment compressing nerve roots
- Facet joint hypertrophy and ligamentum flavum thickening contributing to new stenosis
- End-plate signal changes (Modic changes) adjacent to fusion hardware
- Note: Radiographic adjacent segment changes are far more common than symptomatic disease
CT Scan
- Osteophyte formation at the endplate margins of the unfused level
- Facet joint arthrosis with joint space narrowing at adjacent levels
- Hardware integrity assessment — loosening or pseudarthrosis can accelerate adjacent degeneration
- Foraminal narrowing from combined osteophyte and disc height loss
X-Ray
- Disc space height reduction at levels adjacent to the fusion
- Anterior osteophytes bridging toward the fused segment
- Dynamic flexion-extension views may reveal hypermobility at the adjacent level as the fused level is immobilized
- Sagittal alignment assessment — flat-back or kyphotic deformity increases adjacent segment stress
Who Is Commonly Affected
The following patterns are commonly associated with this condition based on published population studies. Individual presentation varies; these figures are informational only.
Peak Age Range
Varies with original surgery age; symptomatic ASD typically 50–70 years
Gender Distribution
Roughly equal; slightly higher in males who undergo more trauma-related fusions
Estimated Prevalence
Approximately 25–30% of cervical fusion patients develop symptomatic ASD within 10 years; lumbar rates vary by fusion length
Treatment Options
Conservative
- Physical therapy to strengthen core and reduce adjacent segment load
- NSAIDs and analgesics for pain management
- Epidural steroid injections or selective nerve root blocks for radiculopathy
- Activity modification to reduce mechanical stress
Surgical
- Extension of fusion — adding adjacent levels to the existing construct
- Decompression alone (laminectomy or foraminotomy) if instability is not present
- Disc replacement at the adjacent level — preserves motion and may reduce further ASD risk
When to see a spine specialist
Return to your spine surgeon if you experience new or worsening pain, arm or leg symptoms, or functional decline after a prior spinal fusion. Adjacent segment disease is best evaluated by the surgeon who performed the original procedure — imaging (MRI and flexion-extension X-rays) is used to compare with baseline post-operative studies and plan any intervention.
Specialists Who Treat Adjacent Segment Disease
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Questions to Ask Your Doctor
Bring these questions to your next appointment about adjacent segment disease.
- 1
Which levels were fused and which adjacent levels are now showing degeneration on my MRI?
- 2
Is my pain or weakness coming from the adjacent segment, or could it be related to the original fusion?
- 3
What is my risk of needing revision surgery, and how long do most patients manage with conservative treatment?
- 4
Are there specific activities I should avoid to reduce stress on the segments above and below my fusion?
- 5
Would a selective nerve root or facet injection help confirm whether the adjacent level is the pain generator?
Clinical Evidence
Frequently Asked Questions
How common is adjacent segment disease after lumbar fusion?
Radiographic evidence of adjacent segment degeneration (changes visible on imaging) appears in approximately 30–50% of patients within 5 years of lumbar fusion. However, clinically symptomatic ASD requiring treatment is less common — affecting roughly 15–25% of patients over a 10-year period. Longer fusion constructs, fusion to the sacrum, and pre-existing adjacent level degeneration at the time of the original surgery increase the risk.
Can adjacent segment disease be prevented?
Completely preventing ASD is not always possible, but risk can be reduced. Minimizing fusion length (fusing only the pathological levels), preserving the adjacent facet joints during surgery, maintaining proper sagittal alignment in the construct, and using motion-preserving technologies (disc replacement, dynamic stabilization) at the index level are strategies that reduce but do not eliminate adjacent segment stress. Postoperative core strengthening also helps distribute load more evenly.
Does adjacent segment disease always require surgery?
No. Many patients with radiographic ASD are asymptomatic or have mild symptoms that respond well to conservative treatment (physical therapy, injections, pain management). Surgery is reserved for patients who have failed comprehensive conservative care and have clinically significant radiculopathy, myelopathy, or mechanical instability confirmed by imaging. The decision to extend a fusion is not taken lightly, as each additional surgery carries incremental risk.