O'Neill 2014.

Methods	Double‐blinded (participant/outcome assessor), placebo‐controlled, randomized clinical trial Sequence generation unclear Follow‐up: 4‐6 months
Participants	Participants: 40 adults in a university setting, Nashville, TN, USA Operation: ICBG for spinal fusion Groups, size: 20/20 Age (± SD), group 1, 2: 66 (± 12), 62 (± 8) Men/women (group 1, 2): 13/7, 13/7 Comorbidities: tobacco use, group 1, 2 (18, 16); alcohol use, group 1, 2 (7, 6)
Interventions	Group 1 (bupivacaine): intra‐op: rectangular window of approximately 4 × 1 cm was created in the cortex of the posterior superior iliac spine using osteotomes and was then hinged open to allow access to cancellous bone. After graft harvest, a gel foam soaked in 10 mL 0.25% bupivacaine was packed into the wound. The cortical bone window was replaced and the wound closed. Group 2 (saline): intra‐op: same method of gel‐foam packing into cortex of posterior superior iliac spine. Gel was soaked in 10 mL 0.9% saline. Adjuvants: none Immediate post‐op pain control: not reported
Outcomes	Continuous: VAS at 4‐6 months Dichotomus: none Other reported: surgical data included the type of surgery, surgical indication, number of levels fused, the use of instrumentation, and the operative time. Health outcomes were back and neck pain, satisfaction with surgical results, and mental/physical states as determined by the Short Form‐12. Adverse events: 1 participant in the saline group had infection
Notes	The reported continuous data were insufficient for inclusion in the additional Bayesian inclusive analysis. Funding sources: "the authors have no relevant financial relationships to disclose." Conflicts of interest: conflicts of interest statement not provided
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "a block randomization scheme was used," but the method of randomization was not described.
Allocation concealment (selection bias)	Low risk	Quote: "a sealed envelope containing the group assignment was opened and the appropriate intervention was performed"
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Participants and surgeons were blinded, but knowledge of anaesthesia team not described
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "all forms were administered and collected by a research nurse without knowledge of the assigned group"
Incomplete outcome data (attrition bias) All outcomes	Low risk	19/20 in the treatment group and 17/20 in the control group completed the final evaluation. Quote: "this met the goal of 17 patients per group as determined from the sample size calculation."
Selective reporting (reporting bias)	Unclear risk	The protocol defined the VAS at 3 months as the primary outcome, but it remained unclear from the manuscript if the pain was recorded at rest or at movement and if the current or the average pain was the initial primary outcome.
Null bias	Low risk	Experimental treatment was effective in improving immediate postoperative pain control for some outcome measures at least.