Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomly allocated
Allocation concealment (selection bias)	Unclear risk	Unclear
Blinding of participants and personnel (performance bias)	High risk	Unlikely
Blinding of outcome assessment (detection bias)	Unclear risk	Not reported
Incomplete outcome data (attrition bias)	High risk	Four participants withdrawn from results in the GA group
Selective reporting (reporting bias)	High risk	Not in intention‐to‐treat. Four failed psoas blocks withdrawn from the study
Other bias	Low risk	Groups well balanced for age and ASA physical status