Fractures of the coronoid: morphology based upon computer tomography scanning

Coronoid fractures have traditionally been described by the Regan-Morrey classification system, based upon lateral plain film radiographs. However, use of computer tomography (CT) scans to determine fracture morphology, define associated injuries, and make treatment plans is now commonplace. In addition, it is increasingly recognized that classification systems based upon plain film imaging studies may not be adequate to describe complex fracture patterns. The purpose of the present investigation was to review CT scans obtained for elbow trauma to describe coronoid fracture morphology and determine inter- and intra-observer reliability.

CT scans performed for elbow trauma over a 2-year period were examined to identify coronoid fractures, and recurring patterns were sought. After patterns were identified, the scans were reviewed by 3 observers to determine inter- and intra-observer reliability.

Of 373 CT scans, 52 identified coronoid fractures were appropriate for review. Five common patterns were identified, including a tip type, mid-transverse type, basal type, anteromedial oblique fractures, and an anterolateral oblique type fracture that has not been well described previously. Inter- and intra-observer reliability ranged from good to very good in this series.

In this series, we describe anatomic patterns by which coronoid fractures break. Five common patterns were noted: a "tip" type fracture seen in 29% of the cases; a "mid-transverse" type fracture (24%); a "basal" type fracture (23); and 2 "oblique" type fracture patterns (24%), including an "anteromedial" type fracture (17%) and an "anterolateral" type (7%). There was a high rate of intra- and inter-observer reliability between and within 3 observers.