Pinzur 1996.

Methods	Double‐, possibly triple‐blind (participant, provider and possibly outcome assessor), placebo/sham‐controlled randomized clinical trial Sequence generation "with use of a table of random numbers" Follow‐up: 6 months
Participants	Participants: 21 adults, at a university setting, Chicago, Illinois, USA Operation: lower limb amputation because of ischaemic necrosis secondary to peripheral vascular disease 2 groups, size: 11/10 Age: 68.3 years (SD ± 12.96) Men/women: 10/11 Comorbidities: diabetes mellitus in 9 participants
Interventions	Group 1 (treatment): GA or spinal, post‐op nerve sheath irrigation (bupivacaine 0.5%, 1 mL/h) and PCA (morphine, no basal rate, demand 2 mg, lockout 15 min, max 30 mg/4 h) for 72 h Group 2 (placebo): GA or spinal, post‐op nerve sheath irrigation (normal saline, 1 mL/h) and PCA (morphine, no basal rate, demand 2 mg, lockout 15 min, max 30 mg/4 h) for 72 h Adjuvants: none Immediate post‐op pain control: significantly improved analgesic consumption
Outcomes	Dichotomous: pain at 6 months Continuous: McGill Pain Questionnaire at 6 months Secondary: none
Notes	Reported data not allocated to groups. No graphics that reported data. We contacted the study author for missing information and outcome data. He responded that the data were not accessible. Hence, outcome data could not be included. Funding sources: "no benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study." Conflicts of interest: no conflicts of interest statement given
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were 'divided into two groups with use of a table of random numbers."
Allocation concealment (selection bias)	Unclear risk	Concealment of allocation not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "the patients and the staff were blinded to the contents of the bag, which were known only to the research pharmacist."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Outcome assessor blinding was not described, but (quote:) "the patients and the staff were blinded to the contents of the bag, which were known only to the research pharmacist."
Incomplete outcome data (attrition bias) All outcomes	High risk	The study authors report on attrition, (2 participants died, 5 did not participate in the questionnaire), but patients lost to follow up were neither allocated to groups nor considered for an ITT analysis. The authors found no statistically meaningful difference in phantom pain, but it remains unclear which participant numbers were taken as the basis for their analysis. An ITT analysis would likely only have confirmed the lack of significance, however.
Selective reporting (reporting bias)	Low risk	Primary outcomes appropriately reported on
Null bias	Low risk	Quote: "the patients in Group A used significantly less morphine during the first and second days after the operation than did those in Group B"