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A Norwegian registry study of 2,252 patients found no statistically significant difference in disability one year after decompression surgery with spinal fusion versus decompression alone. Fusion was associated with longer operations, longer hospital stays and a higher overall complication risk, though the study cannot rule out longer-term benefits.
A study using Norwegian national registry data found no statistically significant difference in disability one year after patients with degenerative spondylolisthesis had spinal decompression with fusion or decompression alone. The analysis included 2,252 patients and adds to evidence questioning whether fusion improves outcomes enough to justify its additional surgical burden.
Researchers compared outcomes for 1,446 patients treated with decompression alone and 806 who also received fusion. Decompression relieves pressure on spinal nerves; fusion joins vertebrae to limit movement between them. The study focused on degenerative spondylolisthesis, in which one vertebra shifts forward relative to the vertebra below it, a condition that can occur alongside spinal stenosis.
The main outcome was the Oswestry Disability Index (ODI), a measure of pain-related disability on which higher scores indicate worse symptoms. Average scores fell from 38.9 before surgery to 22.3 at 12 months for the decompression-only group, and from 41.4 to 20.0 for the fusion group. The estimated difference between groups was 2.2 points, with a 95% confidence interval from -1.6 to 6.1; it was not statistically significant.
The researchers also looked for patient characteristics that might identify a group more likely to benefit from fusion, including age, sex, body mass index and symptom severity. They found no significant differences in ODI improvement across those subgroups. Men with obesity had worse outcomes than men with lower body mass index, but that finding does not establish that fusion would improve their results.
Fusion Adds Burden Without Clear Gain
The findings matter because fusion remains a common addition to decompression surgery, despite mixed evidence about its added benefit. In this analysis, patients receiving fusion did not show a statistically significant advantage on the study’s main disability measure at one year, while their treatment involved more time in surgery and in hospital.
On average, fusion added 85 minutes of operating time and 1.9 days in hospital. The study reported that the overall risk of any complication was doubled with fusion, although no particular complication was identified as more common. The risk of further surgery because of complications was also higher. These associations do not prove that fusion caused every additional complication, but they add to the trade-offs clinicians and patients may weigh when discussing surgery.
The results do not mean fusion is inappropriate for every patient or that surgery itself is ineffective. They address the additional value of fusion compared with decompression alone in the studied population. Decisions for an individual patient depend on clinical details not fully captured by these group averages.
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A Registry Test of Earlier Findings
The study was designed as a target trial emulation: researchers used observational health records to compare treatment groups in a way intended to resemble a clinical trial. The registry identified about 3,900 people who underwent surgery for degenerative spondylolisthesis between 2007 and 2021. After exclusions, including some very elderly patients and people with prior surgery in the same spinal region, 2,252 were included in the main analysis. Data from 236 participants in the earlier NORDSTEN-DS trial were also present in the registry and analyzed again.
Earlier prospective trials in Sweden and Norway also found no improvement in disability from adding fusion, according to the report. A smaller U.S. study likewise found no disability improvement, although it reported better quality of life with fusion. The studies also reported greater operative burden with fusion, including longer procedures and more complications.
Use of fusion has nevertheless been widespread in some countries. A 2023 analysis cited by the researchers reported that 90% of U.S. surgeries for degenerative spondylolisthesis in 2019 included fusion, 23 percentage points higher than three years earlier. The Norwegian study authors said they could not explain the increase. The 2023 analysis pointed to possible influences including financial incentives, limited guidelines or regulation, and delays in spreading evidence through medical education and professional societies.
“This study calls into question the highly prevalent management of pain from lumbar degenerative spondylolisthesis with fusion.”
— James H. McAuley and colleagues
Long-Term Effects Remain Unknown
The analysis relies on administrative registry records, rather than random assignment to surgery types. The researchers said unmeasured differences between patients could have influenced which procedure they received and their subsequent outcomes. A target trial emulation can help structure an observational comparison, but it cannot eliminate all possible confounding.
The study assessed outcomes at 12 months, so it does not establish whether fusion could offer benefits or disadvantages over a longer period. The reported 2.2-point difference was not statistically significant, but the confidence interval ranged from a small advantage for fusion to a larger one. The available material does not establish which individual patients, if any, might benefit based on factors not captured in the analysis.
Guidelines and Longer Follow-Up
The researchers said their findings should prompt a review of guidance on treating lumbar degenerative spondylolisthesis. The report describes current recommendations as limited and conflicting, but it does not identify a specific guideline revision or timeline. Any changes would require further consideration by clinical and professional bodies.
Longer follow-up and additional research may help clarify whether outcomes diverge beyond the first year and whether specific patient groups benefit from fusion. For now, the registry findings add to prior trials but do not resolve every question about surgical choice. Patients and clinicians will need to consider the evidence alongside individual symptoms, imaging and health circumstances.
Key Questions
What did the Norwegian study find?
It found no statistically significant difference in disability 12 months after decompression surgery with fusion versus decompression alone among 2,252 analyzed patients.
Does the study show that spinal fusion never helps?
No. The study compared average outcomes for the groups it analyzed and did not rule out benefit for every individual or possible effects beyond its 12-month follow-up.
What additional burdens were associated with fusion?
Fusion was associated with an average of 85 more minutes in surgery and 1.9 additional hospital days. The study also reported a higher overall risk of complications, though registry data cannot by itself prove that fusion caused each complication.
What is degenerative spondylolisthesis?
It is a condition in which one vertebra shifts forward in relation to the vertebra below it. It can occur with spinal stenosis, a narrowing that may put pressure on spinal nerves.
What are the study’s main limitations?
The researchers relied on observational administrative records, so unmeasured differences between patients may have affected the comparison. The study also assessed outcomes for only one year, leaving longer-term results uncertain.
Source: medpagetoday.com
