21u-M/3   Ulna, complete

These fractures may be simple (M/3.1) or multifragmentary (M/3.2).

In these fractures the periosteum is ruptured, the elbow joint may be involved and radial head subluxation or dislocation may occur (Monteggia lesion) especially when the fracture line is distal to the coronoid.

Note: To rule out a Monteggia lesion or equivalent fracture, check for the stability/fracture of the radial head/neck.