Amano 2019.

Study characteristics
Methods	Design: parallel‐group RCT Study period: November 2007–September 2016
Participants	Setting: elective general or colorectal surgery Type of stoma: ileostomy or colostomy Inclusion criteria Age ≥ 18 years Elective stoma reversal Ability to provide voluntary informed consent for participation Exclusion criteria Parastomal hernia requiring intensive repair Double stomas located close to each other Refusal to provide consent for participation in the trial
Interventions	PSSC using subcuticular absorbable suture (n = 89) versus LSC using interrupted non‐absorbable suture plus use of wound drain (n = 79). Wound drain was used in the LSC group but no mesh was used during closure in either group.
Outcomes	Wound healing 30 days after surgery SSI at the stoma site 30 days after surgery (diagnosed by the presence of erythema, pain, swelling or discharge at or around the stoma site
Notes	The 2 groups were comparable in terms of baseline demographics (age, sex, BMI) and comorbidities. The length of follow‐up was 1 month. The study received no external funding, and the protocol had been registered with University Hospital Medical Information Network (registration number: UMIN000030772). The study authors declared no conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Method and type of randomisation described appropriately.
Allocation concealment (selection bias)	Low risk	Method used for randomisation supports allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel were not blinded (blinding may not be practical in this setting).
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcome assessment was not blinded (blinding may not be practical in this setting).
Incomplete outcome data (attrition bias) All outcomes	Low risk	Complete outcome data for all participants.
Selective reporting (reporting bias)	Low risk	No selective reporting detected.
Other bias	Low risk	No other sources of bias detected.