Mettler 2008.

Study characteristics
Methods	Truly randomised trial (sequentially numbered sealed envelopes) Time of randomisation: intraoperatively Single‐blind: participant Power calculation: yes ITT: yes Location: multi‐centre—6 centres (Germany, Canada, Netherlands, Antilles) Timing and duration: July 2003 to Jan 2005; 1 year 7 months
Participants	Females, 18 years of age and older, undergoing myomectomy by laparoscopy or laparotomy Number randomly assigned: 72 Number undergoing second‐look laparoscopy: 58 (13 lost to follow‐up, 1 excluded intraoperatively) Timing second‐look laparoscopy: 6 to 8 weeks postoperative Blinding at second‐look laparoscopy: yes Exclusion criteria: uterine incision not > 2 cm or on posterior surface, pelvic inflammatory disease, malignancy, pregnancy, immune‐compromised condition, use of corticosteroids intraoperatively or postoperatively
Interventions	Hyaluronic acid versus Ringer's lactate Hyaluronic acid applied before closure to uterine sutures and surgically‐treated areas. 300 mL to 500 mL Ringer's lactate instilled at end, if in control group
Outcomes	Analysed in review Adhesions at second‐look laparoscopy Number of women with adhesions at SLL Mean adhesion score at SLL Other outcomes Adhesions at second‐look laparoscopy Mean AFS score change Subanalyses based on whether laparoscopy or laparotomy, no or previous abdominal surgery, removal of 1 or multiple myomas
Notes	mAFS score used at 15 sites, but during study, to restrict to posterior uterus score Funded by Angiotech Pharmaceuticals
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomly‐generated list of sequential numbers used
Allocation concealment (selection bias)	Low risk	Allocation concealed in sealed envelopes, opened during surgery, after initial surgical assessment performed
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	women blinded; surgeons and study personnel not blinded
Blinding of outcome assessment (detection bias) All outcomes	High risk	Surgeons performing outcome assessments at initial surgery and SLL not blinded to allocation
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	One woman mistakenly randomised and withdrawn prior to treatment. 13 other women withdrew consent before SLL
Selective reporting (reporting bias)	High risk	mAFS score was to have been calculated by averaging the scores from women at each of 15 sites treated for adhesions, according to the original study protocol; mAFS score at posterior uterus used "In hindsight it became apparent that use of this score would have biased interpretation of the results...for hydrogel subjects, the composite score would have been calculated as the average of the individual mAFS scores from the 2 or 3 sites treated with hydrogel; whereas, for control subjects, the composite score would have been calculated as the average of all 15 sites....it became apparent that the posterior uterus was the one anatomical site at which all women were at risk for adhesion formation...in keeping with these findings, it was determined that the mAFS score at the posterior uterus was the outcome best suited to serve as the primary measure of performance"
Other bias	Low risk