The injuries in Group 1 nearly always involve a fracture of the radial head. Coronoid fractures are common as well and are almost always limited to less than 50% of the height of the coronoid ...

1a) structures are composed of the coronoid process of the ulna ... Restoring Elbow Stability After Fracture-Dislocation Part I: Elbow Anatomy and Patterns of Injury in Fracture-Dislocations.