Corman 1981.

Methods	RCT Methods to control for contributory patient factors: "Patients were further classified according to septic or contaminated status and whether or not steroids were required."
Participants	Age: no information provided Gender: no information provided Type of incision: no information provided Type of surgery: overall: sigmoid colectomy 25%, right colectomy 20%, proctocolectomy 11%, low anterior resection 4%, Hartmann resection 3%, transverse colectomy 3%, other 11% Contamination classification of included participants: no information provided Pre‐operative antibiotic use: no information provided Prognostic patient factors: a total of 86 participants (53%) were operated for malignancy Sepsis: 8.9% in group 1, 9.4% in group 2 and 6.8% in group 3 Inclusion criteria: consecutive patients having a bowel operation employing a midline incision Exclusion criteria: none described
Interventions	Comparisons reported: Group 1 Suture: nylon (multifilament, non‐absorbable) Suturing technique: interrupted, simple Closure method: mass Group 2: Suture: polypropylene (monofilament, non‐absorbable) Suturing technique: interrupted, simple Closure method: mass Group 3: Suture: polyglactin‐910 (multifilament, fast absorbable). Suturing technique: interrupted, simple Closure method: mass Surgeon characteristics: no clear information; "All procedures were performed by or under the direction of one of the three authors"
Outcomes	Wound infection: no definition provided Follow‐up duration: mean follow‐up was 19 months overall; no group‐wise data available Incisional hernia: no definition provided Wound dehiscence: no definition provided Suture sinus or fistula: no definition provided
Notes	Hernia data excluded from analysis due to unclear follow‐up duration Groups 1 and 2 combined for analysis of absorbable versus non‐absorbable sutures Groups 1 and 3 combined for analysis of monofilament versus multifilament sutures
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"...the suture material to be used was randomly selected using a computer."
Allocation concealment (selection bias)	Unclear risk	"...the suture material to be used was randomly selected using a computer."
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information provided
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants analysed in the group they were assigned
Selective reporting (reporting bias)	Unclear risk	Unclear length of follow‐up for incisional hernia outcomes
Other bias	Low risk	The study appears to be free of other sources of bias