Postacchini 1993.

Methods	RCT Setting: not reported Country: Italy Period: not reported
Participants	Number: 67 patients (26/9/32) Diagnosis: all patients had plain and flexion‐extension radiographs of the lumbar spine with one or more of myelography, plain or contrast‐enhanced computed tomographic, and magnetic resonance imaging Included: patients with central lumbar stenosis who required surgery Excluded: not reported Age (years): mean (range) 57 (43‐79)
Interventions	Group 1: multiple laminotomies Group 2: scheduled multiple laminotomies converted to total laminectomy Group 3: total laminectomy. Disc excision was performed at a single level in four patients. A unilateral or bilateral intertransverse fusion was performed in four patients with degenerative spondylolisthesis Follow‐up: 3.7 years (2.2‐5.3)
Outcomes	Pain: 100 mm VAS leg pain (radicular symptoms) Operation time Perioperative blood loss Complications
Notes	Surgeon's experience: all the patients were operated on by the senior author. Funding: Conflict of interest and financial support were not reported in this study.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "we aimed to randomise the choice of surgical procedure, but had to allow the protocol to be broken when multiple laminotomy appeared to be inadequate to obtain sufficient decompression."
Allocation concealment (selection bias)	Unclear risk	Not mentioned.
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	Low risk	Quote: "at the latest follow‐up, each patient was interviewed and examined by one of the authors, who was unaware of the type of decompression performed."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	67/70 = 95.7% of the patients completed the follow‐up. The number of drop‐outs is unlikely to affect the results.
Intention‐to‐treat analysis (attrition bias)	Unclear risk	No information about intention‐to‐treat analysis.
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported.
Group similarity at baseline (selection bias)	Unclear risk	No information about patient characteristics at baseline.
Co‐interventions (performance bias)	High risk	Concomitant discectomy and fusion were performed at different rates between the groups.
Compliance (performance bias)	Low risk	Compliance in both treatment groups: 100% (surgery).
Timing of outcome assessment (detection bias)	High risk	Quote: "the mean follow‐up was 3.7 years (2.2 to 5.3)."
Other bias	Unclear risk	Conflict of interest and financial support were not reported in this study.