We asked surgeons participating in the randomised controlled trial of different strategies for nailing tibial fractures whether they thought a reamed procedure or non-reamed procedure was superior before participating in the randomised controlled trial and at the time of the survey (that is, when about 900 patients had been randomised).12 Surgeons rated their confidence about the superiority of the procedure they selected on a seven point scale, with 1 representing no confidence, 4 representing moderate confidence, and 7 representing extreme confidence. Before participating in the randomised controlled trial, 87% (95% confidence interval 77% to 94%) of respondents believed that a reamed procedure was superior and 86% of respondents indicated their confidence about the superiority of a reamed procedure was in the moderate to extreme range. After 900 patients were randomised, responses remained similar.

Differential expertise bias in a conventional randomised controlled trial in which 70% of surgeons are expert in procedure A and 30% in procedure B