I'm not sure if this qualifies as a "mess up" but it was the worst experience of my life.

I tore my ACL senior year of high school, and went to one of the best orthopedic surgeons in the area. He had a spotless record, and ensured me the procedure would be quick and easy since I was young. So after the surgery, I'm not recovering as quickly as I should have been, and they do some tests and find out that I have an infection in my knee, which was pretty regular, they would give me some medication and it would be taken care of. So a couple more days pass and its getting worse, so they take more aggressive action, and decide to do a 'washout' of my knee joint, which is essentially circulating antibacterial fluid through the joint which should take care of the infection. They did that 3 times, while I was taking some oral medication, and it still didn't get better. At that point they set me up with a Pic-line, which is a permanent IV that they stick in you, so you can take intraveneous medication, which is much more potent that oral medication. I was prescribed vancomycin which is one of the strongest anti-bacterial, and I was taking that daily while doing some wash outs. After 5 failed attempts with washouts combined with the intraveneous medication, they opted to remove my ACL graft and attempt the reconstruction a year later, because they couldn't find where the infection was, and assumed it was in the graft or in the screws. So a year passes, and I get my ACL reconstruction which recovers much quicker than the first time, and goes off without any hitches. Aside from wasting a good year of my life unable to play sports, which was the thing I loved most. I lost a lot of muscle mass in my bad knee, which despite lots of physical therapy, is no where near as strong as it should be. The doctor apologized, and we considered a lawsuit, but it would be impossible to prove malpractice given my situation, and there was nothing I could do to prove he was at fault any step along the way.