Moojen 2013.

Methods	Multi‐centre double blinded RCT Setting: 5 neurosurgical centres in the Netherlands Country: Netherlands Period: October 2008 to September 2011
Participants	Number: 159 patients (79/80) Diagnosis: clinical diagnosis of neurogenic claudication by a neurologist with MRI findings of spinal canal stenosis Included: patients between 40 and 85 years; 3 months of neurogenic claudication; single or 2‐level degenerative lumbar canal stenosis; indication for surgery Excluded: cauda equina syndrome; herniated disc needing discectomy; history of surgery; significant scoliosis Age (years): mean 64/66 BMI (kg/m²): mean (range) 28 (20‐37)/27 (20‐48) Lumbar stenosis duration (years): mean (range) 1.9 (0.1‐17)
Interventions	Group 1: decompression (laminotomy, flavectomy, facetectomy). In the decompression group, a partial resection of the adjacent laminas was executed, followed by a flavectomy with bilateral opening of the lateral recess and, if necessary, a medial facetectomy was done Group 2: interspinous process spacer device (Paradigm Spine, USA). In the experimental group, no bony decompression was done and the interspinous process device was implanted by a posterior midline approach. Follow‐up: 12 months
Outcomes	Pain: 100 mm VAS leg pain Disability: RMDQ Function: ZCQ (physical function) Costs Operation time Perioperative blood loss Complications Reoperations Length of hospital stay
Notes	Surgeon's experience: not reported Funding: "Paradigm Spine funded this trial. Paradigm Spine had no role in data collection, design of the study, data analysis, interpretation of data, or writing the report and had no influence over whether to submit the manuscript. All the researchers were individually independent from funders"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomized design with variable block sizes, with allocations stratified according to center."
Allocation concealment (selection bias)	Low risk	Quote: "opaque, coded and sealed envelopes". "After induction of anaesthesia, the prepared envelope was opened and the patient allocated to one of the treatment arms."
Blinding of participants (performance bias) All outcomes	Low risk	Quote: "patients, nurses on the hospital wards, and research nurses remained blind to the allocated treatment during the follow‐up period of one year."
Bliding of personnel/ care providers (performance bias)	High risk	The surgeon could not have been blinded to the intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "all caregivers blind to the allocated treatment."
Incomplete outcome data (attrition bias) All outcomes	Low risk	151/159 = 95% of the patients completed the follow‐up. The number of drop‐outs is unlikely to affect the results.
Intention‐to‐treat analysis (attrition bias)	Low risk	Quote: "we compared groups on the basis of an intention to treat analysis."
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported.
Group similarity at baseline (selection bias)	Low risk	Patients did not differ in their baseline characteristics, based on Table 1.
Co‐interventions (performance bias)	Low risk	Only the surgical technique differed between treatment groups. All participants received the same postoperative care.
Compliance (performance bias)	Low risk	Compliance in both treatment groups: 100% (surgery).
Timing of outcome assessment (detection bias)	Low risk	All important outcome assessments for both groups were measured at the same time.
Other bias	Low risk	Quote: "Paradigm Spine funded this trial. Paradigm Spine had no role in data collection, design of the study, data analysis, interpretation of data, or writing the report and had no influence over whether to submit the manuscript. All the researchers were individually independent from funders."