System used to describe ulnar fractures with radial head dislocation. Type 1, ulnar diaphysis with anterior angulation and dislocation of head of radius; type 2, ulnar diaphysis with posterior angulation and dislocation of head of radius; type 3, ulnar metaphysis with anterolateral or lateral dislocation of head of radius; type 4, proximal radius and ulnar fracture with anterior dislocation of head of radius.