Pollock 1979.

Methods	RCT Methods to control for contributory patient factors: none
Participants	Age: Group 1: 60.4% ≥ 60 Group 2: 61.6% ≥ 60 Group 3: 62.6% ≥ 60 Gender: Group 1: female 57.3% Group 2: female 58.6% Group 3: female 59.6% Types of incisions: Group 1: midline 56.3%; transverse 43.7% Group 1: midline 58.6%; transverse 41.4% Group 1: midline 55.6%; transverse 44.4% Types of surgery: Group 1: emergency 12.5% Group 2: emergency 21.2% Group 3: emergency 22.2% Contamination classification of included participants: not specified Preoperative antibiotic use: not specified Prognostic patient factors: Group 1: obesity 32.3%; jaundice 8.3% Group 2: obesity 41.4%; jaundice 6.1% Group 1: obesity 34.3%; jaundice 5.1% Inclusion criteria: consecutive patients undergoing emergency or elective major laparotomy Exclusion criteria: gridiron muscle‐splitting incision, Pfannenstiel for prostatectomy, lumbar and incisions through pre‐existing incisional hernias were excluded
Interventions	Comparisons reported: Group 1: Sutures: steel (monofilament, non‐absorbable) Suture technique: continuous Closure method: mass Group 2: Sutures: PGA (multifilament, fast absorbable) Suture technique: continuous Closure method: mass Group 3: Sutures: nylon (monofilament, non‐absorbable) Suture technique: continuous Closure method: mass Characteristics of surgeons: consultant (50.8%) and registrar closures (49.2%)
Outcomes	Hernia: visible bulge deep to the scar on straining, plus palpable defect in musculo‐aponeurosis Follow‐up duration: "Not less than 6 months" Wound infection: any discharge from wound within 1 month of surgery Sinus/fistula: no definition provided
Notes	Hernia data excluded from analysis due to inadequate follow‐up duration Group 1 and 3 analysed together as 'non‐absorbable' and 'monofilament'
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not specified
Allocation concealment (selection bias)	Unclear risk	Not specified
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not specified
Incomplete outcome data (attrition bias) All outcomes	Low risk	Participants accounted for; loss to follow‐up described by group
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