How common is it to fracture the same bone?

Repeat fractures: Unfortunately, a bone that has been fractured once is weakened, and is prone to fracture again. This is particularly true the more recent your initial fracture is.

Depends: The fracture of a bone generally depends on the force directed to the bone. Thus, the refracture of a bone is certainly possible if a force is directed at the same location as the previous break. The site of a previous fracture is no more or less likely to fracture than any other site.