Lozano‐Balderas 2017.

Methods	Study design: randomised controlled trial Ethics and informed consent: ethics approved Sample size calculation: no ITT analysis: yes number randomised: 81 number analysed: 81 Follow‐up period: healed (when in hospital) or in a 30‐day period after surgery (if discharged) Funding: non‐industry Pre‐registration: yes
Participants	Location: Mexico Intervention group: n = 25control group: n = 27 (3 arms: delayed primary closure group: n = 29) Median age (IQR): intervention group = 32 (22 to 46);control group = 30 (20 to 43) Inclusion criteria: minimum age of 18; a laparotomised wound with class III or IV (contaminated/dirty‐infected) surgical wounds Exclusion criteria: not specified
Interventions	Aim/s: to compare infection rates between primary, delayed primary, and vacuum‐assisted closures in contaminated/dirty‐infected surgical wounds Group 1 (NPWT) intervention: the VAC was used with routine changes of dressings every 48 hours until healthy granulation tissue was found and a surgeon decided to close it. Group 2 (control) intervention: subcutaneous tissue was approximated with polyglycolic acid, and polypropylene was used for the skin. Study date/s: January to July 2014
Outcomes	SSI Validity of measure/s: according to the CDC Surgical Wound Classification Time points: daily when in hospital or in a 30‐day period after surgery
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "patients were allocated to each group with the software Research Randomizer® (Urbaniak, G. C., & Plous, S., Version 4.0)"
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Evidence for participants: not possible Comment: unlikely to affect outcomes Evidence for personnel: not possible Comment: unlikely to affect outcomes
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcome assessors were aware of group allocation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	81 participants were enrolled and analysed.
Selective reporting (reporting bias)	Low risk	Expected outcomes reported. Protocol retrospectively registered on ClinicalTrials.gov (NCT02649543).
Other bias	Low risk	No other biases detected.