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A Norwegian registry analysis found no statistically significant difference in disability one year after spinal decompression surgery, whether or not spinal fusion was added. Fusion was associated with longer operations and hospital stays, and a higher overall risk of complications; the observational study cannot rule out longer-term benefits or effects from unmeasured differences between patients.
A Norwegian analysis of 2,252 patients undergoing surgery for spinal stenosis with degenerative spondylolisthesis found no statistically significant improvement in disability one year after surgery when spinal fusion was added to decompression, compared with decompression alone. The registry-based study, reported by MedPage Today on Nov. 2 and published in Annals of Internal Medicine, also found fusion involved longer operations and hospital stays and a higher overall risk of complications.
The researchers compared outcomes for 1,446 patients who had decompression alone and 806 who also had fusion. Decompression surgery relieves pressure on nerves; fusion joins vertebrae to limit movement between them. The analysis used Norwegian national registry records for people treated between 2007 and 2021 and applied a method called target trial emulation to compare the two approaches. After exclusions, the study included 2,252 patients, with an average age of about 65; roughly 70% were women.
At 12 months, mean Oswestry Disability Index scores were 20.0 for the fusion group and 22.3 for the decompression-only group. The scale runs to 50, with higher scores indicating greater disability. The estimated mean difference was 2.2 points, with a 95% confidence interval from -1.6 to 6.1; the researchers reported that this did not reach statistical significance. Baseline scores averaged 41.4 in the fusion group and 38.9 in the decompression-only group.
The study also found that fusion added an average of 85 minutes of operating time and 1.9 days in hospital. No single type of complication stood out as more common, but the overall risk of any complication was doubled in the fusion group, and the risk of further surgery because of complications was higher still, according to the report. Subgroup analyses did not identify a patient group, based on characteristics such as age, sex, body mass index or symptom severity, with a significant disability benefit from fusion. Men with obesity had worse outcomes than men with lower body mass index, a separate finding that does not establish that fusion caused the difference.
Fusion Adds Burden Without Clear Benefit
The results matter because adding fusion can make an operation longer and more demanding, with more time in hospital and a higher overall complication risk in this analysis. If it does not improve disability for the typical patient at one year, patients and clinicians may need to weigh those added burdens against a benefit that the study did not detect. The findings do not prove that fusion never helps an individual patient, but they add to evidence that its routine use deserves scrutiny.
The question also concerns practice patterns. MedPage Today reported that fusion is common in some countries, particularly the United States and Australia. A 2023 analysis cited in its report found that 90% of U.S. operations for degenerative spondylolisthesis in 2019 included fusion, 23 percentage points higher than three years earlier. That figure is a reported share of operations, not evidence that the Norwegian results directly describe U.S. practice or outcomes.
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A Registry Test of Fusion Practice
Degenerative spondylolisthesis occurs when one vertebra shifts forward relative to the vertebra below it and can accompany spinal stenosis, a narrowing that may put pressure on nerves. Some surgeons have treated the vertebral shift as a sign of instability that fusion should correct. The current analysis tested whether adding fusion was associated with better outcomes in routine care, rather than relying only on a randomized trial.
The researchers revisited data from Norway’s NORDSTEN-DS trial within the national registry, alongside records for other eligible patients. MedPage Today noted that earlier prospective studies in Sweden and Norway also found no disability improvement from fusion over decompression alone; a smaller U.S. study did not find better disability outcomes, though it did report better quality of life with fusion. Those earlier studies also reported greater burdens, including more bleeding, longer operations and higher costs. The current analysis adds a larger registry-based comparison, but its design has different limits from a randomized trial.
The researchers, led by James H. McAuley of Neuroscience Research Australia, said in their report that the findings add to existing evidence and should prompt a review of guidance. They also noted that recommendations are sparse and conflict with one another. A 2023 analysis, as described by MedPage Today, proposed possible reasons for rising fusion use, including financial incentives, gaps in guidelines and slow dissemination of evidence; these were explanations offered by that analysis, not causes established by the Norwegian study.
“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 study
Longer-Term Effects Remain Unknown
The analysis does not establish that fusion and decompression alone produce identical outcomes for every patient. It used administrative registry records rather than random assignment, so unmeasured differences between patients could have influenced which operation they received and how they fared. The researchers identified confounding as a limitation.
The follow-up covered 12 months, leaving open whether fusion offers benefits or disadvantages over a longer period. The study also did not identify a subgroup with a statistically significant disability benefit, but that result cannot rule out benefits for particular patients that the available data or analyses did not detect. The report does not settle which individual clinical features should guide a decision to fuse.
Guidelines and Longer Follow-Up
The researchers said the results should prompt a reevaluation of current guidelines for treating lumbar degenerative spondylolisthesis. The study report does not specify a timetable for such a review, and no guideline change is confirmed in the source material. Clinicians and patients will continue to face decisions based on the available evidence and individual circumstances.
Further research with longer follow-up could help clarify whether fusion has benefits beyond the first year or for specific patient groups. Until then, the Norwegian findings support discussion of the uncertain disability benefit alongside the additional operating time, hospital stay and complication risk reported in the study. The registry analysis provides evidence for that discussion, but does not by itself dictate an operation for an individual patient.
Key Questions
What did the Norwegian study find?
In a comparison of 2,252 patients, researchers found no statistically significant difference in disability at 12 months between patients who had decompression surgery alone and those who also had spinal fusion.
Did spinal fusion improve disability scores?
The mean 12-month score was 20.0 in the fusion group and 22.3 in the decompression-only group. The estimated 2.2-point difference was not statistically significant; the study does not establish that fusion has no benefit for any individual.
What additional burdens were linked with fusion?
Fusion was associated with an average of 85 extra minutes in surgery and 1.9 additional hospital days. The study also reported a doubled overall risk of any complication, although no single complication type stood out as more common.
Can the findings be applied to every patient?
No. This was a registry-based analysis, not a randomized trial, and unmeasured differences between patients may have affected the results. The findings also cover only the first 12 months after surgery and do not rule out longer-term effects.
What happens after this report?
The researchers called for current guidelines to be reevaluated, but the source report does not describe a scheduled review or confirmed change. Longer follow-up and further research may help clarify whether some patients benefit from fusion over time.
Source: medpagetoday.com
