Bucknall 1981.

Methods	RCT Methods to control for contributory patient factors: none described
Participants	Age: Group 1 (mean): 53.3 years Group 2 (mean): 50.5 years Gender: Group 1: 53.8% female Group 2: 61.5% female Type of incision: Group 1: midline 37.7%, paramedian 62.3% Group 2: midline 41.3%, paramedian 58.6% Type of surgery: Group 1: emergent 18.8%; "bowel surgery" 43.4%; malignancy 26.4% Group 2: emergent 17.3%; "bowel surgery" 39.4%; malignancy 20.2% Contamination classification of included participants: information not provided Pre‐operative antibiotic use: information not provided Prognostic patient factors: information not provided Inclusion criteria: all adult patients admitted to 1 hospital who underwent laparotomy through vertical incisions in the year 1979 Exclusion criteria: none described
Interventions	Comparisons reported: Group 1 Suture: nylon (monofilament, non‐absorbable) Suturing technique: continuous Closure method: mass Group 2: Suture: PGA (multifilament, fast absorbable) Suturing technique: continuous Closure method: mass Surgeon characteristics: Group 1: consultant 32.1%; senior resident 44.3%; other resident 23.6% Group 2: consultant 26.0%; senior resident 49.0%; other resident 25.0%
Outcomes	Incisional hernia: no definition provided Follow‐up duration: 8.3 months in nylon group, 8.5 months in PGA group Wound infection: no definition provided Wound dehiscence: "total wound disruption" Suture sinus or fistula: no definition provided
Notes	Hernia data not included in analysis due to inadequate follow‐up duration; other outcomes included
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"In 1979, all adult patients in the Professorial Surgical Unit at Westminster Hospital who underwent laparotomy through vertical incisions were randomised, by means of random number cards, into two groups."
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information provided
Incomplete outcome data (attrition bias) All outcomes	Low risk	< 10% loss to follow‐up (4/110 in group 1, 2/106 in group 2)
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