There are 2 parts:

1. Presumably, the surgeon has determined that this specific intervention is the best possible intervention of all the possible ones (fewest downsides, best outcome, etc). There are always alternatives - including #wontfix.

2. Once this decision has been made, I don't want them second guessing, I want them 100% confident in the decision and their abilities. If there's any lingering doubt - then return to step 1 and re-evaluate.