Risk of Bias 2 Assessment: BoNT-A versus Placebo

The Risk of Bias 2 (RoB 2) tool was employed to assess the methodological quality of included studies for botulinum toxin A versus placebo. Judgments were supported by justification statements and direct quotes for each bias domain. Each study was independently assessed by at least two reviewers, with disagreements resolved by consensus. Bias was categorised as ‘high risk of bias’, ‘some concerns’ or ‘low risk of bias’ based on the responses to the signalling questions and the tool’s algorithms. An overall risk of bias rating was determined for each outcome. No studies achieved an overall low risk of bias for the primary outcomes of pain intensity, pain events, and function-disability. The majority of studies demonstrated a high overall risk of bias. Two domains, risk of bias arising from the randomisation process and risk of bias in the selection of reported results, were particularly influential in contributing to the high overall risk of bias for primary outcomes.