Coronoid Fracture Height in Terrible-Triad Injuries

PurposeThe coronoid fractures that occur in the terrible-triad pattern of traumatic elbow instability (posterior dislocation with fractures of the radial head and coronoid) usually are small transverse fragments. Attempts to classify these fragments according to height as suggested by Regan and Morrey have been inconsistent and contentious. The purpose of this study was to quantify coronoid fracture height in terrible-triad injuries.MethodsThe height of the coronoid process of the ulna and the coronoid fracture fragment were measured on computed tomography scans of 13 patients with terrible-triad–pattern elbow injuries. Two observers performed the measurements with excellent intraobserver and interobserver reliability.ResultsThe total height of the coronoid process of the ulna averaged 19 mm. The average height of the coronoid fracture fragment was 7 mm. This corresponds to an average of 35% of the total height of the coronoid process.ConclusionsThe transverse coronoid fractures associated with terrible-triad elbow injuries have a variable height that may not be easy to classify according to the system of Regan and Morrey. Classification of coronoid fractures according to fracture morphology and injury pattern may be preferable.