Stromqvist 2013.

Methods	Multi‐centre RCT Setting: 3 Swedish spine centres Country: Sweden Period: not reported
Participants	Number: 100 patients (50/50) Diagnosis: MRI verified spinal stenosis on 1 or 2 levels in the lumbar spine Included: symptoms of neurogenic claudication for minimum 6 months elicited by walking and relieved by flexion of the spine or sitting down; age 40 years or more was required; spinal stenosis was allowed to be present at maximum 2 levels and minor spondylolisthesis (Meyerding, grade 1) was accepted Excluded: Previous spine surgery (except for successful disc surgery); infection or malignant disorder; osteoporosis diagnosed before referral for surgery and subjected to medical treatment; stenosis of the L5–S1‐level due to the small spinous process of S1 Age (years): mean (range) 69 (49‐89)
Interventions	Group 1: decompression alone. The decompressive procedures were performed using laminectomy or laminotomies with facet‐joint sparing techniques Group 2: interspinous process spacer device (X‐Stop) All operations included open procedures Follow‐up: 24 months
Outcomes	Pain: 100 mm VAS leg pain Disability: ZCQ (physical function) Operation time Complications Reoperations
Notes	Surgeon's experience: not reported Funding: "no funds were received in support of this work"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "randomization was performed by using envelopes."
Allocation concealment (selection bias)	Unclear risk	Quote: "randomization was performed by using envelopes."
Blinding of participants (performance bias) All outcomes	Unclear risk	No mention of any attempts to blind the participants.
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	Unclear risk	No mention of any attempts to blind the assessors.
Incomplete outcome data (attrition bias) All outcomes	Low risk	96/100 = 96% 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: "in the main evaluation, not only was intention‐to‐treat analysis used, but also as‐treated analysis was performed."
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.
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: "no funds were received in support of this work."