Decompression alone or with fusion for degenerative lumbar spondylolisthesis (Nordsten-DS): five year follow-up of a randomised, multicentre, non-inferiority trial.
Kgomotso EL, Hellum C, Fagerland MW, Solberg T, Brox JI, Storheim K, Hermansen E, Franssen E, Weber C, Brisby H, Algaard KRH, Furunes H, Banitalebi H, Ljøstad I, Indrekvam K, Austevoll IM, Nordsten collaborators
- DOI
- 10.1136/bmj-2024-079771
- Record issued
- 2026-08-16
- Engine
- 7.39.0
- Exported
- 2026-09-22
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How this rating was calculated
- IntegrityIntegrity concern ×3−1.5★
- ClaimsEfficacy rests on an unvalidated surrogate endpoint−0.5★
- ClaimsTreatment effect not shown to be clinically meaningful−0.5★
- ReportingData & code availability partially met−0.25★
- No data or code availability links were detected to verify.
- 01Efficacy rests on an unvalidated surrogate endpoint
The primary outcome is a 30% or more reduction in the Oswestry Disability Index (ODI), a patient-reported functional disability scale. This is a surrogate for clinical benefit. The paper does not demonstrate target engagement at the tested dose (not applicable for surgical intervention) nor does it cite validated evidence linking a 30% ODI reduction to hard clinical outcomes. The ODI is a validated instrument, but the claim of non-inferiority is based on this surrogate without establishing a direct link to clinical outcomes such as mortality or major morbidity.
“The primary outcome was a reduction in the Oswestry disability index (version 2.0) of 30% or more from baseline to five year follow-up, defined as a clinically important outcome.”
- 02Treatment effect not shown to be clinically meaningful
The primary outcome is a between-group difference of 0.4 percentage points (95% CI -11.2 to 11.9) in the proportion achieving a 30% ODI reduction. This difference is small and not anchored to a minimal clinically important difference for the between-group difference. The non-inferiority margin of -15 percentage points is predefined, but the observed difference is not explicitly shown to be clinically meaningful. The mean ODI change from baseline is -17.8 in both groups, but the clinical meaningfulness of this change is not discussed in terms of MCID.
“84 (63%) of 133 people in the decompression alone group and 81 (63%) of 129 people in the fusion group had a at least a 30% reduction in Oswestry disability index, a difference of 0.4 percentage points. (95% confidence interval (CI) −11.2 to 11.9).”
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This is a well-conducted and well-reported randomized non-inferiority trial with rigorous design, appropriate statistical methods, and transparent reporting. The main weakness is the vague data availability statement, which lacks a concrete access mechanism or timeframe.
Both independent reviewers agreed on all dimension statuses and study type (interventional). The statistics verification component checked 3 tests (all consistent); coverage is limited to tests with a test statistic and df or an effect estimate with CI. No retracted or non-existent references were found. The copyedit pass flagged 4 minor issues (typos, consistency).
Numerical inconsistencies
1 finding · worst lowValues that contradict each other or are impossible for the stated sample: recomputed p-values and test statistics, GRIM/GRIMMER checks on summary numbers, percentages against their own counts, totals against their parts, and estimates against their own confidence intervals.
- Internal contradictions in the reported numbersAssessed
Recomputed 3 tests: 3 consistent, 0 inconsistent; 3 via agent-written checks.
- CONSISTENTreported p = .947 · recomputed p = .946Reviewer 2Primary outcome difference in mITT with imputation: 0.4 percentage points (95% CI -11.2 to 11.9).
“The difference between the groups was 0.4 percentage points (95% CI −11.2 to 11.9).”
Taken as given: The estimate is the difference in percentages (0.4 percentage points).; The 95% CI is symmetric on the percentage-point scale.; The p-value is two-tailed.Method: Recomputed p-value from the estimate and 95% CI using the normal approximation.How we recomputed it: pCI(0.4, -11.2, 11.9, 0) - CONSISTENTreported p = .850 · recomputed p = .849Reviewer 2Per-protocol primary outcome difference: -1.3 percentage points (95% CI -14.5 to 12.2).
“The respective results of the per protocol analysis were 65 (65%) of 100 in the decompression alone group and 59 (66%) of 89 in the fusion group, a difference of −1.3 percentage points (95% CI −14.5 to 12.2).”
Taken as given: The estimate is the difference in percentages (-1.3 percentage points).; The 95% CI is symmetric on the percentage-point scale.; The p-value is two-tailed.Method: Recomputed p-value from the estimate and 95% CI using the normal approximation.How we recomputed it: pCI(-1.3, -14.5, 12.2, 0) - CONSISTENTreported p = .992 · recomputed p = .992Reviewer 2Mean change in ODI difference: -0.02 (95% CI -3.9 to 3.8).
“The mean change in Oswestry disability index from baseline to five years was −17.8 in the decompression group and −17.8 in the fusion group (mean difference −0.02 (95% CI −3.9 to 3.8)).”
Taken as given: The estimate is the mean difference (-0.02).; The 95% CI is symmetric.; The p-value is two-tailed.Method: Recomputed p-value from the estimate and 95% CI using the normal approximation.How we recomputed it: pCI(-0.02, -3.9, 3.8, 0)
- lowinternal contradictionThe abstract reports 84 (63%) of 133 in the decompression group and 81 (63%) of 129 in the fusion group, but the results section states 84/133 (63%) and 81/129 (63%) - consistent. However, the abstract says '84 (63%) of 133 people' while the results say '84/133 (63%)' - no contradiction.
“84 (63%) of 133 people in the decompression alone group and 81 (63%) of 129 people in the fusion group”
AbstractFind in source - lowinternal contradictionThe abstract reports a mean difference in ODI change of 0.02 (95% CI -3.8 to 3.9), while the results section reports -0.02 (95% CI -3.9 to 3.8). The sign and CI bounds are reversed, which could be a typographical error.
Abstract: 'mean difference 0.02 (95% CI −3.8 to 3.9)' vs Results: 'mean difference −0.02 (95% CI −3.9 to 3.8)'
Abstractreviewer’s wording - lowinternal contradictionThe abstract reports a difference of 0.4 percentage points (95% CI −11.2 to 11.9) for the primary outcome, but the results section reports the same. No contradiction.
“a difference of 0.4 percentage points. (95% confidence interval (CI) −11.2 to 11.9)”
AbstractFind in source
Overstated conclusions
3 findings · worst highConclusions that reach past what the paper's own results support — including a significance claim that no longer holds when the statistic is recomputed, and efficacy resting on an unvalidated surrogate endpoint.
- Efficacy rests on an unvalidated surrogate endpointAssessed
- Treatment effect not shown to be clinically meaningfulAssessed
- Conclusions only partially backed by the presented evidenceAssessed
3 major claims checked against the paper's own evidence: 1 only partially supported (evidence backs part of the claim; gaps or caveats remain); the rest adequately supported.
- partialReviewers 1, 2The results expand on the current evidence that, for most of these patients, fusion surgery is superfluous.The trial shows non-inferiority, but the claim that fusion is 'superfluous' for most patients is a broader generalization beyond the trial's direct evidence, though supported by the non-inferiority result.Evidence: Non-inferiority of decompression alone on primary outcome and similar reoperation rates.
“The results expand on the current evidence that, for most of these patients, fusion surgery is superfluous.”
ConclusionFind in source - supportedReviewers 1, 2Decompression alone is non-inferior to decompression with instrumented fusion at five years.The primary outcome analysis shows the 95% CI for the difference in responders lies above the non-inferiority margin in both mITT and per-protocol analyses.Evidence: Primary outcome results: mITT difference 0.4 (95% CI -11.2 to 11.9); per-protocol difference -1.3 (95% CI -14.5 to 12.2), both above -15%.
“In participants with degenerative spondylolisthesis, decompression alone was non-inferior to decompression with instrumented fusion five years after primary surgery.”
ConclusionFind in source - supportedReviewers 1, 2Proportions of subsequent surgeries at the index level or an adjacent lumbar level were no different between the groups.The reoperation rates were 16% vs 18% with overlapping confidence intervals, supporting no significant difference.Evidence: Reoperation rates: 21/129 (16%) vs 23/125 (18%), difference -2 (95% CI -12 to 7).
“Proportions of subsequent surgeries at the index level or an adjacent lumbar level were no different between the groups.”
ConclusionFind in source
Premise concern: surrogate not validated for clinical benefit; effect size not shown to be clinically meaningful.
- INADEQUATESurrogate endpointThe primary outcome is a 30% or more reduction in the Oswestry Disability Index (ODI), a patient-reported functional disability scale. This is a surrogate for clinical benefit. The paper does not demonstrate target engagement at the tested dose (not applicable for surgical intervention) nor does it cite validated evidence linking a 30% ODI reduction to hard clinical outcomes. The ODI is a validated instrument, but the claim of non-inferiority is based on this surrogate without establishing a direct link to clinical outcomes such as mortality or major morbidity.
“The primary outcome was a reduction in the Oswestry disability index (version 2.0) of 30% or more from baseline to five year follow-up, defined as a clinically important outcome.”
- INADEQUATEEffect sizeThe primary outcome is a between-group difference of 0.4 percentage points (95% CI -11.2 to 11.9) in the proportion achieving a 30% ODI reduction. This difference is small and not anchored to a minimal clinically important difference for the between-group difference. The non-inferiority margin of -15 percentage points is predefined, but the observed difference is not explicitly shown to be clinically meaningful. The mean ODI change from baseline is -17.8 in both groups, but the clinical meaningfulness of this change is not discussed in terms of MCID.
“84 (63%) of 133 people in the decompression alone group and 81 (63%) of 129 people in the fusion group had a at least a 30% reduction in Oswestry disability index, a difference of 0.4 percentage points. (95% confidence interval (CI) −11.2 to 11.9).”
Data authenticity concerns
None foundAn adversarial read for patterns associated with data that may not be genuine: results that look too clean, implausibly large effects, duplicated data or images, and methods that do not match the results reported.
Checked — nothing surfaced.
Reporting gaps
1 finding · worst mediumRequired detail the manuscript never states — study design, biological variables, ethics approval and consent, key resources, statistical reporting, data and code availability, and overall transparency.
- Data/code availability incompleteAssessed
The introduction cites prior randomized trials and meta-analyses indicating decompression alone is sufficient up to two years, but notes contradictory longer-term results. The rationale for the trial is to assess non-inferiority at five years, addressing the gap in longer-term evidence. Limitations of prior research (sparse and contradictory outcomes beyond two years) are explicitly acknowledged.
“More recently, evidence from randomised controlled trials and meta-analyses have indicated that decompression alone is sufficient for up to two years of follow-up. By contrast, one randomised controlled trial found that additional instrumented fusion gave superior results to decompression alone. Results from randomised controlled trials that include outcomes from more than two years after surgery are sparse and contradictory.”
“In this study, we present the five year results of the Norwegian degenerative spondylolisthesis and spinal stenosis (Nordsten-DS) trial to assess whether decompression alone is non-inferior to decompression with instrumented fusion.”
“More recently, evidence from randomised controlled trials and meta-analyses have indicated that decompression alone is sufficient for up to two years of follow-up.”
“Results from randomised controlled trials that include outcomes from more than two years after surgery are sparse and contradictory.”
“In this study, we present the five year results of the Norwegian degenerative spondylolisthesis and spinal stenosis (Nordsten-DS) trial to assess whether decompression alone is non-inferior to decompression with instrumented fusion.”
Randomization method (computer-generated, 1:1, random block sizes) and unit (individual participant) are clearly described. Blinding is open-label with a stated rationale (surgical nature), and the data analyst was masked. Power analysis is reported with effect size, alpha, and power. Inclusion/exclusion criteria are pre-specified and referenced. Outlier handling is addressed through the pre-specified analysis populations (mITT, per-protocol) and multiple imputation for missing data. Controls are inherent in the comparator arm. Independent replication is not applicable for a single pivotal trial.
“The Medinsight database hosted by the clinical trial unit at Oslo University Hospital allowed for the computer generated random assignment of the eligible participants in a 1:1 ratio to undergo either decompression alone or decompression with instrumented fusion. The sequence was concealed from the investigators and stratified according to site using random block sizes of four and six participants.”
“To reject H 0 , 116 participants were required in each group to be 80% certain (power) that the lower limit of a 95% confidence interval (CI) of the difference (decompression alone minus decompression with instrumented fusion) in the percentage of participants with a successful outcome on Oswestry disability index was above −15 percentage points.”
“Individual participants and their surgeons were not masked to the treatment assignment.”
“The Medinsight database hosted by the clinical trial unit at Oslo University Hospital allowed for the computer generated random assignment of the eligible participants in a 1:1 ratio to undergo either decompression alone or decompression with instrumented fusion. The sequence was concealed from the investigators and stratified according to site using random block sizes of four and six participants.”
“Individual participants and their surgeons were not masked to the treatment assignment.”
“To reject H 0 , 116 participants were required in each group to be 80% certain (power) that the lower limit of a 95% confidence interval (CI) of the difference (decompression alone minus decompression with instrumented fusion) in the percentage of participants with a successful outcome on Oswestry disability index was above −15 percentage points. Considering a possible dropout of 10%, 128 participants were required in each group.”
Sex is reported (69% women overall) and both sexes are included, so sex_justified is not applicable. Age, weight (BMI), and health status (comorbidities, ASA scores) are reported. Demographics include age, sex, education, marital status, and smoking. Species/strain and housing conditions are not applicable for a human trial.
“Mean age at baseline was 66.2 years (SD 7.6), and 69% were women.”
“Female sex | 92/133 (69) | 88/129 (68)”
“Female sex | 92/133 (69) | 88/129 (68)”
“Age, years (SD) | 66.0 (7.4) | 66.5 (7.9)”
“Hypertension | 46/133 (35) | 44/129 (34)”
The Regional Committee for Medical and Health Research Ethics of Central Norway (project identifier 2013/366) approved the trial, and written informed consent was obtained from all participants. Regulatory compliance is implied through adherence to CONSORT and Norwegian regulations.
“The Regional Committee for Medical and Health Research Ethics of Central Norway (project identifier 2013/366) approved the trial.”
“All patients who accepted trial participation gave written consent before randomisation.”
“The Regional Committee for Medical and Health Research Ethics of Central Norway (project identifier 2013/366) approved the trial.”
“All patients who accepted trial participation gave written consent before randomisation.”
“The trial reporting follows the consolidated standards of reporting trials (CONSORT) guidelines.”
The surgical interventions are described in detail (decompression technique, fusion with pedicle screws and rods). No specific drug, biologic, or device is named, but the surgical procedures are the investigational product. Statistical software (Stata/SE version 17.0) is identified. Other bench resources are not applicable.
“For the participants assigned to decompression with instrumented fusion, a posterior decompression (with or without preserving midline structures, at the surgeon’s discretion) was followed by implantation of pedicle screws with rods and bone grafting across the level of spondylolisthesis, and optional use of an intervertebral fusion device.”
“The analyses were done using Stata/SE software, version 17.0.”
“For the participants assigned to decompression with instrumented fusion, a posterior decompression (with or without preserving midline structures, at the surgeon’s discretion) was followed by implantation of pedicle screws with rods and bone grafting across the level of spondylolisthesis, and optional use of an intervertebral fusion device.”
“The analyses were done using Stata/SE software, version 17.0.”
Tests are named (Newcombe hybrid score CIs, linear mixed models). Assumptions are checked (visual inspection of histograms). Exact p-values are not reported; instead, effect estimates with 95% CIs are provided, which is appropriate for a non-inferiority trial. Software is identified. Data presentation includes per-group n and CIs. Mathematical plausibility checks were not performed due to continuous outcomes and large N.
“The primary outcome and all categorical secondary outcomes were analysed with Newcombe hybrid score confidence intervals.”
“The difference between the groups was 0.4 percentage points (95% CI −11.2 to 11.9).”
“The primary outcome and all categorical secondary outcomes were analysed with Newcombe hybrid score confidence intervals.”
“The difference between the groups was 0.4 percentage points (95% CI −11.2 to 11.9).”
“The assumption of normally distributed data was assessed with visual inspection of histograms and descriptive statistics, and no major deviations were observed.”
The data availability statement says requests should be submitted to an email for consideration, with the scientific board possibly granting access. This is a managed-access route but lacks details on conditions or timeframe, making it 'reported_but_inadequate'. No repository deposit or accession numbers are provided, and no custom code is mentioned.
“All data requests should be submitted to ivar.magne.austevoll@helse-bergen.no for consideration. The NORDSTEN scientific board may grant access to anonymised data following a research protocol”
“All data requests should be submitted to ivar.magne.austevoll@helse-bergen.no for consideration. The NORDSTEN scientific board may grant access to anonymised data following a research protocol”
Trial registration number is provided (NCT02051374). CONSORT guidelines are followed. All pre-specified outcomes are reported, including secondary and adverse events. Limitations are discussed (open-label, per-protocol sample size). Conclusions are proportional to the evidence. Funding sources and competing interests are declared.
“Trial registration ClinicalTrials.gov NCT02051374”
“Another limitation was the absence of double blinding; only the data analyst was masked to treatment assignments.”
“Trial registration ClinicalTrials.gov NCT02051374”
“The trial reporting follows the consolidated standards of reporting trials (CONSORT) guidelines.”
“Another limitation was the absence of double blinding; only the data analyst was masked to treatment assignments.”
Registered (1 ID: ClinicalTrials.gov). Reporting guideline cited: CONSORT.
Broken references and links
None found · partly checkedReferences checked against Crossref, OpenAlex and Retraction Watch for retractions and resolvability, plus declared data and code links probed for whether they resolve to content matching the paper.
Nothing surfaced — but not everything feeding this category ran (missing: data/code link verification), so read this as a partial clean bill.
Checked 50 references by DOI: 45 verified — 5 no DOI (shown, not verified).
- NO DOIDegenerative spondylolisthesis: surgical treatmentNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIThe NORDSTEN study—degenerative spondylolisthesis (NORDSTEN/DS)No DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIThe Oswestry low back pain disability questionnaireNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOISwespine Annual Report 2022No DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIThe Norwegian Registry for Spinal Surgery. Annual ReportNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
Copyediting
4 minorWording, consistency and formatting errors that need correcting before submission.
No major wording or formatting errors. 4 minor suggestions below.
4 copyedit issues flagged: mostly consistency, typo.
- MINORtypoAbstract, Results“had a at least a 30% reduction”→ had at least a 30% reductionDuplicate article 'a'.
- MINORconsistencyResults, Primary outcome“numbers needed to treat of 8.9 (100/11.2) in the in the modified intention-to-treat set”→ numbers needed to treat of 8.9 (100/11.2) in the modified intention-to-treat setDuplicate 'in the'.
- MINORconsistencyTable 2, EQ-5D-3L row“0.68 (0.63 to 073)”→ 0.68 (0.63 to 0.73)Missing leading zero in '073'.
- MINORconsistencyMethods, Statistical analysis“number needed to treat was 100/15=6.67”→ number needed to treat was 100/15 = 6.67Spacing around equals sign for consistency.
The published paper is methodologically robust and transparent; an informed reader should weigh the vague data availability statement as a minor limitation. No erratum or correction is warranted based on the rigor checks, though the copyedit issues (typos, missing leading zero) could be corrected in a minor revision.
- 1.HIGHdata codeIn the Data availability statement, specify the mechanism for data access (e.g., a data access committee, review process, and expected timeframe) to meet the 'reported_and_adequate' standard.The current vague statement may deter researchers from requesting data and does not meet journal requirements for data availability.
- 2.HIGHdata codeAdd a statement about code sharing if any custom analysis code was used; otherwise, explicitly state that no custom code was used.Transparency about code availability is essential for reproducibility.
- 3.HIGHreportingIn the Data availability section, consider providing a link to the full trial protocol and statistical analysis plan.This would enhance transparency and allow readers to verify that the analysis followed the pre-specified plan.
- 4.MEDIUMcopyeditIn the Abstract, Results, change 'had a at least a 30% reduction' to 'had at least a 30% reduction'.Duplicate article 'a' is a typo.
- 5.MEDIUMcopyeditIn the Results, Primary outcome, change 'in the in the modified intention-to-treat set' to 'in the modified intention-to-treat set'.Duplicate phrase 'in the' is a consistency error.
- 6.MEDIUMcopyeditIn Table 2, EQ-5D-3L row, change '0.68 (0.63 to 073)' to '0.68 (0.63 to 0.73)'.Missing leading zero in '073' is a typo.
- 7.MEDIUMcopyeditIn Methods, Statistical analysis, change 'number needed to treat was 100/15=6.67' to 'number needed to treat was 100/15 = 6.67' for consistent spacing around the equals sign.Consistency in formatting improves readability.
- 8.MEDIUMreportingIn the Discussion, expand on the per-protocol sample size shortfall and its potential impact on the non-inferiority conclusion.The per-protocol sample size was below the a priori required sample size, which could affect the robustness of the non-inferiority claim.
- 9.MEDIUMreportingClarify the role of the data monitoring committee and any interim analysis results in the Methods to enhance transparency.This information is often expected in trial reports and would improve completeness.
- 10.LOWreportingConsider reporting exact p-values for secondary outcomes where feasible, or explicitly state that CIs are used for inference.While CIs are appropriate for a non-inferiority trial, some readers may expect p-values for secondary outcomes.
- 11.LOWreportingInclude a CONSORT flow diagram in the main text (currently referenced as Fig 1) to improve reporting completeness.A flow diagram is a standard element of CONSORT reporting and is already referenced, but should be included in the main text.
The star rating is the report’s one-glance summary. Every paper starts at 5★ and loses stars for the concrete problems the review finds — so a rating is never a vague average, it’s a running total you can read line by line under “How this rating was calculated.”
- Reporting — 8 dimensionseach dimension that fully fails−½★
- each dimension partially met−¼★
- Statistics · Integrity · Claimseach serious problem−1★
- each medium problem−½★
- Citationseach retracted or unverifiable reference−¼★
- Copyeditonly when the manuscript needs a full edit−½★
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