Gammelgaard 1983.

Methods	RCT Methods to control for contributory patient factors: none
Participants	Age: Group 1 (median): 34 Group 2 (median): 38 Gender: Group 1: 63% female Group 2: 60% female Type of incision: Group 1: angular 13.9%, longitudinal 43.0%, transverse/oblique 43.0% Group 2: angular 10.1%, longitudinal 46.5%, transverse/oblique 40.9% Type of surgery: Group 1: emergency 29.0%; biliary 22.5%, gastric/duodenal 20.5%, intestinal 11.3%, appendectomy 24.5%, internal genitalia 21.2% Group 2: emergency 34.2%; biliary 20.1%, gastric/duodenal 19.5%, intestinal 10.1%, appendectomy 25.8%, internal genitalia 22.0% Contamination classification of included participants: not described Pre‐operative antibiotic use: not reported Prognostic patient factors: Group 1: obesity 34.4%, malignancy 15.2% Group 2: obesity 28.4%, malignancy 12.2% Inclusion criteria: consecutive abdominal incisions, either emergency or elective, for operations of the gastrointestinal tract or internal genital organs Exclusion criteria: hernioplasties, McBurney incisions, re‐operations within the follow‐up period, incisions in preparation for stoma operations, patients receiving steroids and non‐Danish patients
Interventions	Comparisons reported: Group 1 Suture: polyglactin‐910 (multifilament, fast absorbable) Suturing technique: peritoneum ‐ continuous, fascia ‐ interrupted Closure method: layered Group 2: Sutures: PGA (multifilament, fast absorbable) Suturing technique: peritoneum ‐ continuous, fascia ‐ interrupted Closure method: layered Characteristics of surgeons: not reported
Outcomes	Incisional hernia: no definition provided Follow‐up duration: 6 months Wound infection: defined as "wound abscess" Wound dehiscence: not defined Sinus or fistula tract: not defined
Notes	Hernia data excluded from analysis due to inadequate follow‐up duration
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	Outcomes assessors blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants accounted for and analysed
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