TL;DR
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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 versus without spinal fusion. Fusion was associated with longer operations and hospital stays, and a higher overall risk of complications; the observational analysis cannot rule out unmeasured differences or benefits beyond 12 months.
A Norwegian analysis of 2,252 patients with degenerative spondylolisthesis found no statistically significant disability advantage one year after spinal decompression when fusion was added, compared with decompression alone. The registry-based study also found that fusion involved longer operations and hospital stays and was associated with a higher overall complication risk, adding evidence to an ongoing debate about a common back-pain surgery.
The study, reported in Annals of Internal Medicine, used Norwegian national health registry records to compare 1,446 patients treated with decompression alone and 806 who also had spinal fusion. The investigators used a method called target trial emulation to compare outcomes in observational data. The analysis included patients who had surgery for degenerative spondylolisthesis, a condition in which one vertebra shifts forward relative to the vertebra below it.
At 12 months, average Oswestry Disability Index (ODI) scores were 20.0 in the fusion group and 22.3 after decompression alone. The estimated difference was 2.2 points, with a 95% confidence interval from -1.6 to 6.1; it did not meet the study’s threshold for statistical significance. ODI scores measure disability, with higher scores indicating worse symptoms. The report said subgroup analyses did not identify a group, based on characteristics including age, sex, body mass index or symptom severity, with a significant disability advantage from fusion.
Fusion added a mean of 85 minutes of operating time and 1.9 days in hospital. No particular complication was singled out as more common, but the overall risk of experiencing any complication was reported as doubled with fusion. The study also reported a larger increase in the risk of further surgery because of complications, though the supplied report does not give an absolute rate for that outcome. These findings describe associations in the registry analysis and do not establish that fusion caused every observed difference.
Added Fusion Brings Added Burden
The results matter to patients and clinicians weighing whether to add a more extensive procedure to decompression surgery. In this study, the added operation did not produce a statistically significant improvement in disability at one year, while it required more time in surgery and longer hospital stays. The reported increase in overall complication risk adds to the considerations patients may discuss with their surgical teams.
The findings do not mean fusion is inappropriate for every patient or that an individual cannot benefit. The analysis did not establish a subgroup with a significant advantage, but its methods and one-year follow-up limit what can be concluded about particular cases or longer-term outcomes. Decisions about surgery require assessment of the person’s condition and options by qualified clinicians; the study is evidence for discussion, not individual medical advice.
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Why Fusion Is Being Reconsidered
Degenerative spondylolisthesis can occur alongside spinal stenosis, a narrowing around the spinal canal. Decompression surgery aims to relieve pressure on nerves. Some surgeons have considered the forward shift of a vertebra a sign of instability and have added fusion to stabilize the affected area. The rationale has been debated because prior studies have not consistently shown improved disability outcomes from adding fusion.
The Norwegian registry analysis extends a previous Norwegian trial, NORDSTEN-DS, by examining a broader national dataset. It included records from 2007 to 2021; 236 people in the current analysis had also participated in NORDSTEN-DS. The report notes that earlier prospective trials in Sweden and Norway, as well as a smaller U.S. study, also did not find improved disability with fusion, although the U.S. study reported better quality of life. Earlier research cited by the report also associated fusion with greater operative burden and costs.
Despite the mixed evidence, fusion has been widely used in some countries. A 2023 analysis cited in the report found that 90% of U.S. surgeries for degenerative spondylolisthesis in 2019 involved fusion, 23 percentage points higher than three years earlier. That figure applies to the U.S. surgeries examined in that analysis, not to the Norwegian registry patients.
“This study calls into question the highly prevalent management of pain from lumbar degenerative spondylolisthesis with fusion.”
— James H. McAuley, PhD, and colleagues
Limits of the One-Year Comparison
The study relied on administrative registry records rather than random assignment, so differences between patients that were not captured in the data could have affected the comparison. The authors identified potential unmeasured confounding as a limitation. Although the analysis was designed to emulate a trial, it remains observational and cannot provide the same certainty as a randomized comparison.
The main outcome was assessed at 12 months. The findings therefore do not establish whether fusion might offer benefits or disadvantages over a longer period. Nor does the report establish which specific patients, if any, could gain a meaningful benefit that this analysis did not detect. The study also does not settle how clinicians should apply its results to individual decisions.
Guidelines and Longer Follow-Up
The authors said their findings should prompt a reevaluation of clinical guidelines, which they described as limited and conflicting. The report does not announce a guideline change, a new trial or a scheduled policy review. Any change in practice would depend on how clinicians, professional groups and health systems weigh this study alongside other evidence.
For patients considering surgery, the practical next step is a discussion with their clinician about the expected benefits and risks of decompression alone versus adding fusion, taking individual circumstances into account. Further research with longer follow-up could help clarify whether outcomes differ beyond the first year and whether particular patient groups benefit.
Key Questions
What did the Norwegian study find?
In a registry analysis of 2,252 patients, adding fusion to decompression was not linked to a statistically significant difference in disability scores at 12 months compared with decompression alone.
Did fusion take longer or involve more complications?
Fusion was associated with a mean of 85 additional minutes in surgery and 1.9 additional hospital days. The study reported a doubled overall risk of any complication, but its observational design means this association should not be treated as proof of cause.
Does this prove that no patient benefits from fusion?
No. The analysis did not find a subgroup with a significant disability advantage, but it cannot rule out individual benefits or differences the registry data did not capture. It also assessed outcomes at one year.
Could fusion have benefits after the first year?
The study does not answer that question. Its outcome comparison covered 12 months after surgery, and the authors noted that longer-term benefits remain possible.
Source: medpagetoday.com
