Gys 1989.

Methods	RCT Methods to control for contributory patient factors: none
Participants	Age: Group 1 (mean): 64 years Group 2 (mean): 61 years Gender: Group 1: 48% female Group 2: 49% female Type of incision: Group 1: upper midline 30%, lower midline 39%, full midline 9%, subcostal 25%, other 7% Group 2: upper midline 30%, lower midline 34%, full midline 9%, subcostal 27%, other 0% Type of surgery: Group 1: emergency 24%; colorectal 34%, pancreaticobiliary 28%, oesophagogastric 22%, vascular 6%, other 10% Group 2: emergency 26%; colorectal 32%, pancreaticobiliary 34%, oesophagogastric 20%, vascular 3%, other 11% Contamination classification of included participants: Group 1: contaminated 9.0% Group 2: contaminated 4.6% Pre‐operative antibiotic use: not described Prognostic patient factors: Group 1: diabetes 9.0%, obesity 40.3%, malignancy 56.7%, respiratory failure 9.0%, jaundice 4.5% Group 2: diabetes 7.7%, obesity 30.8%, malignancy 44.6%, respiratory failure 9.2%, jaundice 7.7% Inclusion criteria: consecutive patients undergoing elective or emergency laparotomy Exclusion criteria: none described
Interventions	Comparisons reported: Group 1 Suture: nylon (monofilament, non‐absorbable) Suturing technique: continuous Closure method: layered ('0' for peritoneum, '1' for musculo‐aponeurotic layer) Group 2: Suture: polyglyconate (monofilament, slowly absorbable) Suturing technique: continuous Closure method: layered ('0' for peritoneum, '1' for musculo‐aponeurotic layer) Surgeon characteristics: not described
Outcomes	Incisional hernia: assessed by palpation with patient lying supine and with elevation of extended legs Follow‐up duration: 1 year Wound infection: postoperative purulent discharge with proven growth of a micro‐organism Dehiscence: "burst abdomen" Sinus or fistula: no definition provided
Notes	—
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	Unclear risk	Not described
Incomplete outcome data (attrition bias) All outcomes	High risk	Of the total of 132 participants, 13 (9.8%) died within 1 year and 22 (17.0%) were lost to follow‐up
Selective reporting (reporting bias)	Low risk	Hernia (at least 1 year); dehiscence and wound infection outcomes all reported
Other bias	Low risk	The study appears to be free of other sources of bias