An interventional study of Decompression alone and Decompression with extended fusion in Lumbar Adjacent Spinal Stenosis and Chronic Low Back and Leg Pain, sponsored by Oslo University Hospital. Not yet recruiting at 3 sites in Norway. Open to participants aged 18 Years to 80 Years. Per ClinicalTrials.gov, last updated 2026-06-26.
Sponsored by Oslo University Hospital · Not applicable, Interventional, and Treatment
The goal of this clinical trial is to learn if there are differences in the effectiveness of decompression surgery alone versus decompression combined with extended fusion in patients with a previous lumbar spinal fusion who now present with symptoms of lumbar adjacent segment stenosis (LASS). The main questions it aims to answer are:
Researchers will compare decompression surgery alone versus decompression combined with extended fusion to see if there are any differences in treatment effect.
Participants will:
Globally, musculoskeletal disorders are the leading causes of years lived with disability, with spinal disorders contributing to 70% of this burden. The consequences for patients, their families and society are significant.
Lumbar spinal stenosis is a common condition with an increasing prevalence, largely due to an aging population. It is caused by degenerative changes in the supporting structures of the lumbar spine leading to symptoms like low-back pain and radiating pain to the lower extremities as well as numbness and weakness causing walking restrictions. Annually, about 200,000 to 250,000 new cases are diagnosed in the United States alone and this condition is the most frequent indication for spinal surgery in patients older than 65 years of age. Approximately 10% of the population over 50 years suffer from symptomatic lumbar spinal stenosis.
Lumbar surgery may be indicated in patients with various degenerative spinal conditions when non-surgical treatment has failed, and radiological findings are consistent with clinical symptoms. Decompression (removal of stenotic structures to relieve nerve pressure) and spinal fusion (the use of screws, rods, plates, or other devices to assist in achieving fusion between vertebral bodies) remain the cornerstone of operative treatment. The volume of lumbar spine surgery has increased considerably over the past decades, particularly for more complex procedures such as instrumented fusion, and especially among the elderly. In the United States, the hospital costs of lumbar instrumented fusion procedures is reported to be higher than for any other surgical procedure such as percutaneous coronary angioplasty and knee- and hip arthroplasty. In Norway, approximately 700 lumbar spinal fusions are performed every year, with about half of them being reoperations.
Lumbar spinal fusion has the highest complication rates among all spinal surgeries. Complications involving either the segment above or below (=adjacent to) a previously fused segment can arise years after the initial fusion. An annual incidence of 2,5-4% for new subsequent surgery after initial lumbar fusion is reported, 13.6% and 22.2% were re-operated within 5 and 10 years respectively. The majority of reoperations following an initial fusion are due to spinal stenosis adjacent to a previously fused segment (Lumbar Adjacent Segment Stenosis - LASS), and these patients constitute a substantial subgroup within the extensive and growing patient population with spinal stenosis.
At present, there are no guidelines or prospective studies that can advise clinicians on how patients with LASS should be treated, and this issue is emerging as one of the most relevant and debated questions within degenerative spine surgery. According to register data, the most common treatments are either extending the fusion beyond the symptomatic adjacent stenotic segment or just decompression of the stenotic structures, with a tendency of performing just decompression in patients with cranial LASS and decompression with extended fusion in patients with caudal LASS. However, there is large variation in surgical practices both between and even within hospitals. Considering the increasing prevalence of LASS, costs, and risks associated with spinal fusions, there is need for randomized trials to evaluate surgical practice and the relative efficacy of the two most common surgical treatments.
Statistical Hypothesis: The primary objective is to evaluate the effect of Decompression alone versus Decompression with extended Fusion at two-year FU. Thus, the null hypothesis to be tested in relation to the primary endpoint is as follows:
Patients will be randomly assigned in a 1:1 ratio to undergo decompression surgery alone or decompression combined with extended instrumented fusion. Procedure for decompression will be mid-line preserving technique, and with the use of vision-enhancing aid (microscope magnifying glasses). The procedure for extended fusion will involve bilateral pedicle screws and with an aim to transplant a minimal amount of bone volume. All surgeons need to have at least senior surgeon experience.
Statistical analysis: The effect measure for the primary endpoint will be the difference between the treatment groups in the probability of reaching a minimum 30% ODI improvement from baseline to one-year FU. It will be estimated by the difference in observed proportions with a 95% Newcombe hybrid score confidence interval. A two-sided P-value for the null hypothesis of a zero difference will also be calculated with the Fisher mid-P test. Safety endpoints will be tabulated and presented with descriptive statistics.
Further details of the statistical methods will be provided in the SAP. The SAP will be finalized before the database lock and will include a more technical and detailed description of the statistical analyses.
Interim analysis: An interim analysis for safety will be performed when 50% of the patients in each group have completed the 12-month FU. If one of the proposed stop criteria is fulfilled the study will be terminated:
An independent statistician blinded for treatment adherence will perform the interim analysis. Only data on reoperations and on NRS for leg pain will be available to the statistician. Following the analysis, the statistician will inform the steering committee, via the central monitor (at Clinical Trial Unit, Oslo University Hospital) whether the study can continue. Further information about the analysis will not be disclosed or available by anyone else than the independent statistician until the main analysis at 2-year FU.
Sample Size Determination: This study is powered for the main outcome (ODI) to be able to detect at least a 20% absolute difference between the proportions of responders (ODI improvement of minimum 30% from baseline) assessed at two-year follow-up between the two treatment groups. For the sample size determination, we anticipated that 55% from the decompression with extended fusion arm and 35% from the decompression alone arm will reach the primary outcome. The statistical power selected is 80%, and the accepted type I error rate 5% (β =0.2, α = 0.05). Considering these assumptions with a superiority two-sided test, 96 patients are required in each group (192 total). The significance level will be set at 0.05 and all estimates will be reported with 95% CI and the exact p-value.
458 studies on the registry are indexed under Spinal Stenosis; 105 are open to participants now.
This study's planned enrollment of 192 is above the median of 80 across 281 interventional studies indexed under Spinal Stenosis.
Browse Spinal Stenosis studies →Oslo University Hospital is the lead sponsor of 834 studies on the registry; 149 are open to participants now.
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Participants must meet all the following criteria to be eligible for the study:
Exclusion Criteria:
Participants will be excluded if any of the following criteria are met:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
ASA physical status
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients allocated to decompression alone will be offered mid-line preserving decompression technique
Procedure: Decompression alone
Patients allocated to decompression with extended fusion will be offered decompression with the use of vision enhancement, in addition to the procedure for the extended fusion involving bilateral pedicle screws with autologous bone transplant and/or bone substitutes.
Procedure: Decompression with extended fusion
Patients allocated to decompression alone will be offered mid-line preserving decompression technique with the use of a vision-enhancing aid (microscope or magnifying glasses).
Patients allocated to decompression with extended fusion will be offered decompression with the use of vision enhancement (microscope or magnifying glasses). The procedure for the extended fusion will involve bilateral pedicle screws with autologous bone transplant and/or bone substitutes. The use of an interbody device (cage) or not and decompression technique will be at the discretion of the surgeon. Bone grafts should be placed in the interbody device and either posteriorly and/or anteriorly to the interbody device. Autologous bone can be placed in the intervertebral space without a cage if it is not feasible e.g., due to a too narrow intervertebral disc space. Alternatively a posterior or posterolateral bone grafting can be performed.
Oswestry Disability Index (ODI): Change in percent
Improvement in the ODI score of a minimum of 30% from baseline (dichotomized variable: yes / no (yes = improved 30% or more, no = improved less than 30%)). The ODI is a questionnaire examin the level of disability based on 10 everyday activities of daily living. Each item consists of 6 statements which are scored from 0 to 5, with 0 indicating the least disability and 5 the highest level of disability. The total score is calculated as a percentage, with 0% indicating no disability and 100% indicating the highest level of disability.
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but ODI will also be assessed before surgery, 3 months, one- and five years postoperatively)
Oswestry Disability Index (ODI): Continuous
Change in ODI from baseline (continuous variable)
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but ODI will also be assessed before surgery, 3 months, one- and five years postoperatively)
Numeric Rating Scale leg pain (NRS leg pain)
Change in NRS leg pain from baseline. The NRS is a 11-point numeric scale (patient reported) ranging from '0' (e.g. "no pain") to '10' (e.g. "worst possible pain")
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but NRS leg pain will also be assessed before surgery, 3 months, one- and five years postoperatively)
Numeric Rating Scale back pain (NRS back pain)
Change in NRS back pain from baseline. The NRS is a 11-point numeric scale (patient reported) ranging from '0' (e.g. "no pain") to '10' (e.g. "worst possible pain").
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but NRS back pain will also be assessed before surgery, 3 months, one- and five years postoperatively)
Global perceived effect (GPE)
The GPE scale asks the participant to rate, on a 7 point Likert scale, how much their condition has improved or deteriorated. GPE 1-2 defined as success (completely recovered (1), much better (2)), GPE 3-5 defined as no change (somewhat better (3), no change (4), somewhat worse (5)), GPE 6-7 defined as worsening (much worse (6), worse than ever (7))
Time frame: From three months after surgery to five years postoperatively (main endpoint is two years after surgery, but GPE will also be assessed 3 months, one- and five years postoperatively)
Oswestry Disability Index (ODI): Change in percent
Less than 20% improvement in ODI defined as failure. Dichotomized variable: yes / no (yes = less than 20% improvement from baseline, no = improved 20% or more from baseline).
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but ODI will also be assessed before surgery, 3 months, one- and five years postoperatively)
EuroQol-5 dimensions-5 levels (EQ-5D-5L)
Change in EQ-5D-5L from baseline. The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each EQ-5D-5L dimension has 5 levels: no problems, slight problems, moderate problems, severe problems and extreme problems. The participant is asked to indicate his/her health state by ticking the box next to the most appropriate statement in each of the five dimensions. This decision results in a 1-digit number that expresses the level selected for that dimension. The digits for the five dimensions can be combined into a 5-digit number that describes the patient's health state. Index scores range from -0.59 to 1, where1 is the best possible health state.
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but EQ-5D-5L will also be assessed before surgery, 3 months, one- and five years postoperatively)
Occupational status and return to work
To evaluate the effect of decompression alone versus decompression combined with extended fusion on ability to work, the participants will be asked about their occupational status and return to work
Time frame: From enrollment to five years postoperatively (main endpoint is two years after surgery, but participants will also be asked about their occupational status before surgery, 3 months, one- and five years postoperatively)
Radiology
A- Total lumbar lordosis on standing radiograph, B- Sagittal imbalance (difference between pelvic incidence and lumbar lordosis \> 10 °) on standing radiograph, and C- Fusion (evaluated on CT in patients undergoing decompression combined with extended fusion). Standing X-ray is taken six times, CT-scan one time.
Time frame: From enrollment to five years postoperatively. Standing X-ray is taken six times (before surgery, postoperatively before discharge from hospital, and 3 months, 1 year, 2 years, and 5 years after surgery). CT 2 years after surgery (extended fusions only)
Reoperations
The incidence, type and number of reoperations
Time frame: During the whole study period (five years)
Adverse Events of special interest (AESI) and Serious Adverse Events (SAEs)
Safety assessments: Incidence of adverse events of special interest (AESI) and serious AE (SAEs)
Time frame: During the whole study period (five years)
Cost-effectiveness
Change in the EQ-5D-5L, hospital costs, community costs including sick leave, co-interventions (pharmacological and non-pharmacological).
Time frame: During the whole study period (five years)
Plan to share: No
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