According to statistics there are around 4,000 surgical errors that occur every year.
However while that seems like a lot of surgical errors which it is it's still not too bad and rare that surgical errors or any other issues occur when surgery is done.
There are more than 4,000 surgeries happening every year around the world so that 4,000 surgical errors when compared to the amount of properly done surgeries and successful surgeries is small.
Over 100,000 to 500,000 people and more go through surgery every year just fine without any surgical errors being done.
But since the surgeon is human even the most highly qualified surgeon can make mistakes which they try to avoid the best they can.
But it is understandable since a surgeons job is really stressful as it is.