A lot of how a child’s bone heals depends on the age of the child, how he broke the bone, how bad the break is, if there are other injuries, and the type of treatment chosen. In this case, it’s very difficult to say if a shortened leg is normal after a break, but it’s not abnormal either.
Researchers have been studying ways to adapt treatments to minimize the chances of leaving a bone shorter when it heals, but it still happens, depending on the circumstances.