Is it possible that a finger/thumb bone fracture is so superficial, that the doctor does not need to realign (re-set) the bone before applying the cast? Or does it always require for even a finger/thumb broken bone to be put back in place before applying the cast?
Yes. You can figure that yourself if you look a bit at the types of fractures on Wikipedia, the Bone Fracture page:
Other considerations in fracture care are displacement (fracture gap) and angulation. If angulation or displacement is large, reduction (manipulation) of the bone may be required and, in adults, frequently requires surgical care.
Other types of fracture are:
- Complete fracture: A fracture in which bone fragments separate completely.
- Incomplete fracture: A fracture in which the bone fragments are still partially joined. In such cases, there is a crack in the osseous tissue that does not completely traverse the width of the bone.
Incomplete fractures and fractures with less or no displacement may heal correctly in some situations without needing realignment.
Most finger fractures (including the thumb) and, for that matter, hand fractures will not need to be "reset" before applying a cast, as most fractures are simple and non-displaced. More serious fractures (displaced, involving an articular surface, and many comminuted fractures) will need manipulation and possibly pinning.
But to answer your question, the fracture need not be incomplete to be casted/immobilized without manipulation. It is not rare, but common.