Richards 1983.

Methods	RCT Methods to control for contributory patient factors: none
Participants	Age: unknown Gender: unknown Types of incisions: Group 1: midline 85.3%; oblique 13.6%; paramedian 1.1% Group 2: midline 80.3%; oblique 17.5%; paramedian 2.1% Types of surgery: unknown Contamination classification of included participants: Group 1: clean 38.8%; clean‐contaminated 53.8%; contaminated 7.3% Group 2: clean 31.9%; clean‐contaminated 59.3%; contaminated 8.8% Preoperative antibiotic use: unknown Prognostic patient factors: not described Inclusion criteria: abdominal incision > 5 cm, excluding major trauma and heavily contaminated wounds
Interventions	Comparisons reported: Group 1: Sutures: polypropylene (monofilament, non‐absorbable) Suture technique: continuous Closure method: mass Group 2: Sutures: PGA (multifilament, fast absorbable) for anterior sheath, polypropylene (monofilament, non‐absorbable) for posterior sheath Suture technique: interrupted Smead Jones for anterior, continuous for posterior/transverse/oblique Closure method: layered Characteristics of surgeons: unknown
Outcomes	Hernia: no definition Follow‐up duration: 12 months Wound infection: no definition Dehiscence: no definition Sinus/fistula: no definition
Notes	Not included in absorbable versus non‐absorbable analysis as polypropylene was used on the fascia for both groups
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Method of closure determined by drawing a sealed card from 1 of 3 boxes
Allocation concealment (selection bias)	Low risk	Sealed card
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants accounted for and dropouts explained
Selective reporting (reporting bias)	Low risk	Hernia follow‐up at least 1 year; dehiscence and wound infection reported
Other bias	Low risk	The study appears to be free of other sources of bias