Savolainen 1988.

Methods	RCT Methods to control for contributory patient factors: none
Participants	Age: no information given Gender: no information given Types of incisions: upper midline incision only Types of surgery: no information Contamination classification of included participants: no information Preoperative antibiotic use: no information Prognostic patient factors: no information Inclusion criteria: all upper midline incisions within 1 year
Interventions	Comparisons reported: Group 1: Sutures: PGA (multifilament, fast absorbable) Suture technique: interrupted, simple Closure method: mass Group 2: Sutures: polyglyconate (monofilament, slowly absorbable) Suture technique: continuous Closure method: mass Group 3: Sutures: polypropylene (monofilament, non‐absorbable) Suture technique: continuous Closure method: mass Characteristics of surgeons: not described
Outcomes	Wound infection: no definition Dehiscence: no definition
Notes	Hernia not an outcome of this study Group 1 compared with Group 2 in 'interrupted versus continuous' analysis and 'slow versus fast absorbable' analysis, Group 2 compared with Group 3 in 'absorbable versus non‐absorbable' analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Randomised according to birthday
Allocation concealment (selection bias)	High risk	Randomised according to birthday
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants accounted for/dropouts explained
Selective reporting (reporting bias)	Low risk	Dehiscence and wound infection reported
Other bias	Unclear risk	Duration of follow‐up not specified (in hospital only)