Kind of a spinoff from another thread... How many people have learned techniques that are supposed to break someone's arm, either while standing or on the way to the ground.

The fact is, you will almost never be able to purposely break someone's arm in this manner if they are even somewhat skilled and/or strong and providing resistance. While these types of breaks do occasionally occur, they are almost always accidental.

Any breaks that one can perform "on purpose" will be those that one can do while controlling the opponent on the ground, rather than when standing or throwing.