Sorry it has taken me so long to respond. This is a complicated question and as a doctor it is not always easy to tell when someone needs an operation. Sometimes it is because they had an accident that caused damage to their organs or perhaps cancer is the reason. There are actually many types of doctors that do many different kinds of surgeries.
In my research we have never had a study where we looked at surgery as an experimental part of a study.
Great question though. Ask me if you have a follow-up question.