By Marc Darrow, MD, JD

Patients sometimes contact our office after lumbar fusion because pain has returned or moved to a different part of the back or leg. Some have been told that a neighboring spinal level has deteriorated and another operation may be needed. This is called adjacent segment disease. It is a recognized potential complication of fusion, although a new symptom after surgery does not automatically mean that the neighboring level is responsible.

Fusion joins two or more vertebrae so that they no longer move independently. With an L3–L4 fusion, the immediately neighboring motion segments are L2–L3 above and L4–L5 below. A level number such as “L5” alone does not identify a disc or motion segment.

Degeneration on an MRI is different from adjacent segment disease

Adjacent segment degeneration describes changes seen on imaging, such as disc narrowing, arthritis of the small facet joints, or a change in alignment. Many such findings cause no symptoms. Adjacent segment disease means that a neighboring level has developed a clinical problem, such as painful stenosis or nerve compression, that fits the patient’s symptoms and examination. Some patients with symptomatic disease need surgery; others improve with nonsurgical care. A review of fusion studies reported pooled radiographic degeneration of 26.6% after lumbar fusion, with approximately one-quarter to one-third of those imaging cases progressing to symptomatic disease. That estimate comes from a 2019 review, combines studies with different follow-up periods, and is not an individual’s chance of requiring revision surgery. (1)

A separate systematic review estimated rates of imaging degeneration, symptomatic disease, and reoperation at 27.8%, 7.6%, and 4.6%, respectively, across the studies it analyzed. These are different outcomes and should never be used interchangeably. (2)

Why can the level next to a fusion become painful?

Fusion eliminates motion at the operated level. Neighboring levels may then bear altered loads or move differently. Their discs and facet joints may already have been degenerating before surgery, however, and ordinary aging continues afterward. Both the surgery and the patient’s existing anatomy can contribute; an MRI alone cannot prove that fusion caused the change. Reviews identify preexisting adjacent degeneration, higher body mass index, and features of the operation and alignment among possible risk factors, although the strength of evidence varies. (3) (4)

One study of people who underwent L4–L5 fusion linked the shape and distribution of lumbar lordosis—the spine’s inward curve—with later surgery for L3–L4 adjacent stenosis. This is an association, not proof that changing one measurement will prevent revision. (5)

How often does another operation follow fusion?

In a retrospective, single-center study of 1,233 patients who underwent decompression and fusion for lumbar stenosis, investigators reported 164 readmissions. Among those readmissions, 63 were associated with the original level, 72 with the level above, and 29 with the level below. The researchers identified adjacent degeneration as the most common reason for readmission. These counts describe where problems occurred among the readmitted patients; they do not establish that 62% of all fusion patients develop adjacent disease or that every readmission represents a revision operation. (6)

The risk also depends on why fusion was recommended in the first place. Fusion can be appropriate for selected patients, including some with instability or deformity. Yet stenosis does not automatically require fusion. In a randomized study of lumbar stenosis, adding fusion to decompression did not improve disability scores at five years. Another randomized trial in patients with stenosis and degenerative spondylolisthesis found decompression alone was noninferior to decompression plus fusion at five years; additional lumbar operations occurred in both groups. These trials inform a surgical discussion but do not settle the choice for every patient. (7) (8)

What should be checked when pain returns?

Recurrent pain can come from adjacent stenosis, but also from an incompletely healed fusion (pseudoarthrosis), recurrent nerve compression, hardware problems, sacroiliac or hip pain, and other causes. A clinician should compare the current symptoms and neurological examination with the original diagnosis and operative records. Imaging may include MRI and, when indicated, standing or motion X-rays or CT to assess the fusion and alignment. A report that says “degeneration” is only one piece of that assessment.

New bowel or bladder dysfunction, numbness around the groin, or rapidly progressive leg weakness warrants urgent medical evaluation.

Treatment options after adjacent segment disease is diagnosed

Treatment depends on the actual pain source, severity of nerve compression, and presence of instability. Options may include a tailored exercise and physical therapy program, medication, selected image-guided injections, or surgical evaluation. Progressive neurological deficit or severe, persistent nerve compression may change the balance toward surgery. A 2024 review describes approaches ranging from conservative care to decompression and extension of fusion, but emphasizes that treatment must fit the individual condition. (9)

Where do PRP and bone marrow treatments fit?

Platelet-rich plasma (PRP) and bone marrow-derived cell preparations are being studied for selected types of low back pain. They have not been shown to prevent adjacent segment disease, reverse established stenosis, reliably restore disc height, or replace an indicated decompression. Evidence about injections into a painful disc cannot be transferred automatically to adjacent-level disease after fusion. Nor is there sound evidence in the studies above that PRP improves fusion success or prevents pseudoarthrosis.

In our office, the first question is which structure is generating the patient’s pain. Any discussion of an injection should follow a careful review of the diagnosis, prior surgery, expected benefit, uncertainty, and procedural risks. A promising biological mechanism is not the same as proof of clinical benefit.

Questions to ask before a first or repeat fusion

  1. Which symptom is the proposed operation expected to improve: leg pain, walking tolerance, back pain, or weakness?
  2. Is there demonstrable instability or another specific reason to add fusion to decompression?
  3. What do the adjacent discs and facet joints look like now, and how will spinal alignment be addressed?
  4. What nonsurgical care is reasonable, and how long should it be tried?
  5. If pain returns after surgery, how will the cause be confirmed before recommending another operation?

Takeaway: Adjacent segment disease is a meaningful long-term risk of lumbar fusion, but most imaging changes do not mandate another surgery. A careful diagnosis and a clear reason for the initial or repeat fusion matter more than any single risk percentage.

References

  1. Hashimoto K, Aizawa T, Kanno H, Itoi E. Adjacent segment degeneration after fusion spinal surgery—a systematic review. International Orthopaedics. 2019;43(4):987–993.
  2. Donnally CJ, Patel PD, Canseco JA, et al. Current incidence of adjacent segment pathology following lumbar fusion versus motion-preserving procedures: a systematic review and meta-analysis of recent projections. The Spine Journal. 2020;20(10):1554–1565.
  3. Mesregah MK, Yoshida B, Lashkari N, et al. Demographic, clinical, and operative risk factors associated with postoperative adjacent segment disease in patients undergoing lumbar spine fusions: a systematic review and meta-analysis. The Spine Journal. 2022;22(6):1038–1069.
  4. Lau KKL, Samartzis D, To NSC, et al. Demographic, surgical, and radiographic risk factors for symptomatic adjacent segment disease after lumbar fusion: a systematic review and meta-analysis. Journal of Bone and Joint Surgery American Volume. 2021;103(15):1438–1450.
  5. Herrington BJ, Fernandes RR, Urquhart JC, Rasoulinejad P, Siddiqi F, Bailey CS. L3-L4 hyperlordosis and decreased lower lumbar lordosis following short-segment L4-L5 lumbar fusion surgery is associated with L3-L4 revision surgery for adjacent segment stenosis. Global Spine Journal. 2025;15(2):382–391.
  6. Lebedev VB, Epifanov DS, Osipov II, et al. Revision surgery after previous spinal decompression and fusion for lumbar spinal stenosis. Zhurnal Voprosy Neirokhirurgii Imeni N. N. Burdenko. 2023;87(1):70–76.
  7. Karlsson T, Försth P, Öhagen P, Michaëlsson K, Sandén B. Decompression alone or decompression with fusion for lumbar spinal stenosis: five-year clinical results from a randomized clinical trial. The Bone & Joint Journal. 2024;106-B(7):705–712.
  8. Kgomotso EL, Hellum C, Fagerland MW, et al. Decompression alone or with fusion for degenerative lumbar spondylolisthesis (Nordsten-DS): five year follow-up of a randomised, multicentre, non-inferiority trial. BMJ. 2024;386.
  9. Huang X, Cai Y, Chen K, et al. Risk factors and treatment strategies for adjacent segment disease following spinal fusion (review). Molecular Medicine Reports. 2025;31(2):33.

 

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