I believe mistakes are made more often than most of us realize. I read an article this morning about another surgery mistake--the patient has cancer of the kidney, and the healthy kidney was removed instead of the cancerous one.
Doctors remove wrong kidney during surgery
http://www.thatsfit.com/2008/03/20/doctors-remove-wrong-kidney-during-surgery/
Doctors remove wrong kidney during surgery
http://www.thatsfit.com/2008/03/20/doctors-remove-wrong-kidney-during-surgery/