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A Norwegian registry analysis found no statistically significant difference in disability after 12 months between patients who had spinal decompression alone and those who also had fusion for degenerative spondylolisthesis. Fusion was associated with longer operations and hospital stays, and a higher overall risk of complications, though the observational study cannot rule out unmeasured differences between patients or benefits beyond one year.
A Norwegian national registry analysis found no statistically significant improvement in disability at 12 months when spinal fusion was added to decompression surgery for people with degenerative spondylolisthesis. The study compared outcomes for 2,252 patients and also found that fusion involved longer operations and hospital stays, with a higher overall risk of complications, adding to evidence that challenges routine use of the more extensive procedure.
The analysis included 1,446 people treated with decompression alone and 806 who had decompression with spinal fusion. Decompression relieves pressure on nerves; fusion joins vertebrae to limit movement between them. The patients had spinal stenosis associated with degenerative spondylolisthesis, in which one vertebra shifts forward relative to the vertebra below it. The study was led by James H. McAuley, PhD, of Neuroscience Research Australia and published in Annals of Internal Medicine, according to MedPage Today.
At 12 months, the average Oswestry Disability Index (ODI) score was 20.0 in the fusion group and 22.3 after decompression alone. ODI measures disability related to back pain, with higher scores indicating worse symptoms; the reported maximum is 50. The estimated difference was 2.2 points, with a 95% confidence interval from -1.6 to 6.1, and was not statistically significant. The researchers also found no significant difference in ODI improvement across the examined subgroups, which included characteristics such as age, sex, body mass index and symptom severity.
Fusion was associated with a mean of 85 additional minutes in surgery and 1.9 additional days in hospital. The researchers reported that the overall risk of any complication was doubled with fusion, although no single complication stood out as more common. The risk of further surgery because of complications was also higher. These findings describe associations in registry data; they do not establish that fusion itself caused every difference.
Fusion Adds Burden Without Clear Benefit
The findings matter because fusion is often added to decompression when vertebral slippage is taken as a sign of spinal instability. That approach entails a more extensive operation and, in this study, more time in surgery, a longer hospital stay and a higher overall complication risk. Yet the registry comparison found no statistically significant disability advantage at one year.
The results do not show that fusion can never help an individual patient. The analysis did not identify a subgroup, based on the characteristics it tested, with a clear disability benefit, but unmeasured clinical factors may still influence treatment decisions. For patients and clinicians weighing surgery, the study supports discussing the additional burdens of fusion alongside the uncertain evidence for extra benefit.
The authors said the findings should prompt a review of current guidance. This is relevant in countries where fusion is commonly used, but the study alone does not establish what practice should be in every health system or for every patient.
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Earlier Trials Also Question Routine Fusion
The new analysis was designed to extend earlier evidence, including the Norwegian NORDSTEN-DS trial. It used a target trial emulation, a method that applies a trial-like comparison to observational health records. Investigators identified about 3,900 people who had surgery for degenerative spondylolisthesis from 2007 to 2021, then excluded some patients, including very elderly people and those with previous surgery in the same spinal region. The final analysis included 236 people from NORDSTEN-DS, whose records were analyzed again as part of the registry study.
Previous prospective trials in Sweden and Norway, as well as a smaller U.S. study, had also reported no improvement in disability from adding fusion. MedPage Today reported that earlier trials found greater complication burdens, including bleeding, alongside longer operating times and higher costs. The U.S. study did report better quality of life with fusion, a difference that illustrates why the evidence has not been entirely uniform.
Despite the uncertainty, fusion has become common in some countries. A 2023 analysis cited by the study authors found that 90% of U.S. operations for degenerative spondylolisthesis in 2019 involved fusion, 23 percentage points higher than three years earlier. The source report says the researchers had no explanation for that increase; authors of the 2023 analysis proposed possible roles for financial incentives, limited guidelines or regulations, and delays in sharing evidence.
“This study calls into question the highly prevalent management of pain from lumbar degenerative spondylolisthesis with fusion.”
— James H. McAuley and colleagues, as quoted in their report
One-Year Data Leave Questions Open
The registry analysis was not a randomized trial. Although the researchers used a target trial emulation, unmeasured differences between patients could have affected which procedure they received and how they recovered. The authors also relied on administrative records, which may not capture every clinically relevant detail.
Follow-up for the reported comparison was 12 months. The study therefore cannot determine whether fusion might have a benefit or disadvantage over a longer period. The measured ODI difference was not statistically significant, but its confidence interval ranged from -1.6 to 6.1 points; the result should not be read as proof that the two procedures are identical in every respect.
The source report does not provide detailed absolute rates for specific complications or further operations, nor does it settle which individual patients, if any, might benefit from fusion. The subgroup analysis did not find significant differences in disability improvement, but it cannot resolve every treatment question.
Guidance and Longer Follow-Up
The authors called for a reevaluation of clinical guidance on fusion for lumbar degenerative spondylolisthesis. The report does not identify a scheduled guideline review or a specific policy change, so any effect on recommendations or surgical practice remains uncertain.
For now, the study adds Norwegian registry evidence to earlier trials questioning whether fusion routinely improves disability outcomes over decompression alone. Further research with longer follow-up and better control of patient differences could clarify whether any groups experience meaningful long-term benefits. Patients considering surgery should discuss the evidence, likely burdens and their own clinical circumstances with their care team.
Key Questions
What did the Norwegian study find?
In a registry analysis of 2,252 patients, adding spinal fusion to decompression was not linked to a statistically significant difference in disability scores 12 months after surgery.
What is the difference between decompression and fusion?
Decompression surgery relieves pressure on nerves in the spine. Fusion joins vertebrae to limit movement between them and may be added when a surgeon considers the spine unstable.
Did fusion have additional risks or burdens in the study?
Fusion was associated with an average of 85 more minutes in surgery, 1.9 more hospital days and a doubled overall risk of any complication. The registry comparison cannot prove that fusion caused every difference.
Does the study prove fusion never helps?
No. The findings show no statistically significant disability advantage at one year in this analysis. Its observational design and limited follow-up leave open questions about individual patients and longer-term outcomes.
What happens next?
The authors said current guidance should be reevaluated, but the report does not specify a review timetable or announced change. Longer-term studies may help clarify whether particular patients benefit from fusion.
Source: medpagetoday.com
