Leaper 1985.

Methods	RCT Methods to control for contributory patient factors:
Participants	Age (SD): Group 1 mean 57.4 years (1.8), Group 2 mean 57.9 years (1.7) Gender: Group 1 female 64%, Group 2 female 60% Types of incisions: Group 1: midline 77.3%, transverse 22.7% Group 2: midline 72%, transverse 28% Types of surgery: Group 1: oesophageal 14.4%, pancreaticobiliary 49.5%, small bowel 4.1%, colon 23.7%, unopened viscus 8.2% Group 2: oesophageal 17.7%, pancreaticobiliary 41.1%, small bowel 4.7%, colon 27.1%, unopened viscus 9.3% Contamination classification of included participants: Preoperative antibiotic use: single intravenous dose of third generation cephalosporin at induction for oesophago‐duodeno‐gastric, biliary and pancreatic operations; either the same or a combination with metronidazole at induction and at 6 and 12 h postoperatively for small bowel and colorectal operations Prognostic patient factors: Malignancy: Group 1 25.8%, Group 2 29% Jaundice: Group 1 25.8%, Group 2 16.3% Inclusion criteria: midline and transverse incisions Exclusion criteria: incisions through scar
Interventions	Comparisons reported: Group 1: Sutures: nylon (monofilament, non‐absorbable) Suture technique: continuous Closure method: mass Group 2: Sutures: PDS (monofilament, slowly absorbable) Suture technique: continuous Closure method: mass Characteristics of surgeons: Group 1 consultants 33%, Group 2 consultants 37.4%
Outcomes	Hernia: not defined Follow‐up duration: 6 months Wound infection: not defined Dehiscence: not defined
Notes	Hernia data excluded due to inadequate follow‐up duration
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated
Allocation concealment (selection bias)	Unclear risk	Not explicitly described
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not explicitly described
Incomplete outcome data (attrition bias) All outcomes	High risk	Not an intention‐to‐treat analysis
Selective reporting (reporting bias)	Low risk	There was no evidence of selective reporting
Other bias	Low risk	The study appears to be free of other sources of bias