Celik 2007.

Study characteristics
Methods	RCT
Participants	789 people undergoing spinal surgery in Turkey between January 2000 and September 2004
Interventions	Group 1: surgical site shaved with a razor immediately prior to surgery (n = 371) Group 2: no hair removal (n = 418) Product details: no details are given for the razor. Timing of hair removal: immediately before surgery. Hair removed by: theatre staff. Venue for hair removal: on the operating table.
Outcomes	Primary outcome: SSI defined by pus, pain, tenderness or redness, plus haematological evidence. Secondary outcome: meningitis and abscess defined by haematological evidence. Data regarding the wound and presence of infection were collected continuously (wounds were assessed at 1‐ and 3‐month follow‐up visits, though it is not known who carried out the follow‐up ‐ personal communication).
Notes	No funds were received to support the study. No details of conflict of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were randomly allocated on a 1:1 ratio on a randomisation sheet" Comment: method of generation of randomisation sequence unclear.
Allocation concealment (selection bias)	Unclear risk	Not reported. Comment: not clear whether the person responsible for allocation to groups would have been able to predict to which group a potential participant would be allocated.
Blinding (performance bias and detection bias) Care providers blinded	Unclear risk	Not reported. Comment: unclear whether care providers were blinded to intervention allocation.
Blinding (performance bias and detection bias) Participants blinded	High risk	Not reported. Comment: participants would have been aware of hair removal method.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported. Comment: unclear whether assessors were blinded to intervention allocation.
Incomplete outcome data (attrition bias) ITT analysis undertaken	Unclear risk	Not reported. Comment: insufficient detail provided to enable a judgement regarding whether there was full analysis of all participants in their randomised groups.
Incomplete outcome data (attrition bias) Drop out rate acceptable	High risk	Personal communication with the author revealed that the dropout rate for the non‐shaved group was unknown, participants not evenly distributed across groups. Comment: participants were not evenly distributed across groups.
Selective reporting (reporting bias)	Low risk	Main outcomes reported. Comment: unlikely to be affected by reporting bias.
Other bias	High risk	Comment: a higher number of complex operations were reported for 1 group.