Schmitz 1997.

Methods	Randomised clinical single‐centre trial. Generation of allocation: unclear. Allocation concealment: adequate. Blinding: not performed. Follow‐up: adequate. Drop‐outs: none; postoperative observation was extended to complete the investigation. Intention‐to‐treat: not mentioned. Sample size calculations: no.
Participants	Patients for elective cholecystectomy. In‐ and exclusion criteria: not very well described. Comparability groups: well matched.
Interventions	SIC versus OC. SIC: 6 cm subcostal transverse incision with diathermy transsection of the right rectus abdominis muscle. OC: a 13 cm subcostal incision with additional partial extension into the muscle spaces of the right lateral epigastric region. Antibiotic prophylaxis: not mentioned. Intra‐operative cholangiography: not mentioned.
Outcomes	Primary and secondary outcome: not mentioned. Outcome measures: operating times, level of subjective pain, analgesic intake, complications. Duration of follow‐up: not mentioned.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Low risk	A ‐ Adequate
Blinding? All outcomes	High risk
Incomplete outcome data addressed? All outcomes	Low risk
Free of selective reporting?	High risk
Free of other bias?	High risk	unclear duration of follow‐up