My daughter broke her arm (cracked the humerus into two pieces), had to have several surgeries, pins the whole 9 yards. She was out completely for for about 2.5 months, and then was on restricted activity/conditioning only for another 6 weeks after the last cast came off.
In terms of gymnastics, I would say that the biggest thing was the introduction of real fear. She used to be completely fearless, and she definitely is way more aware that she can can get hurt now. This happened 2 years ago, and she still struggles with fear a bit. Plus, it happened right at the time girls start having vestibular issues, plus she had a growth spurt while she was out, so I think it was just kind of a perfect storm for fear to creep in.