All surgical procedures have a risk, and having worked in healthcare for many years it would take a lot to get me to have a procedure unless it was really, really necessary. I quote an actual example: a woman goes to hospital and has an operation to correct something wrong with her big toes and dies. It turned out that post-operative, she was given the incorrect dose of a medicine (20mg rather than 2mg).
Beyond those sorts of mix-ups, there is the ever-present problem of post-operative infection, which cannot be prevented 100% of the time. Some of the bugs in hospitals are really nasty, anti-biotic resistant things too.