First described over 50 years ago, the Mason classification remains the standard classification system for radial head fractures. This study attempts to determine the intraobserver and interobserver reliability of the Mason classification system using plain radiographs. A total of 50 radial head fractures were identified. Half had frontal and lateral radiographs, while the remaining half had an additional external rotation oblique view. Four orthopaedic surgeons reviewed each set of radiographs on two separate occasions at least two months apart. Two surgeons were fifth year residents, and the other two observers were fellowship trained upper extremity surgeons.
Interobserver reliability was found to be moderate to fair, with a trend toward improved interobserver agreement when an external rotation oblique view was included. Significant intraobserver reliability was noted in three of the four readers, which were noted to be higher when the additional view was included.
While only moderate interobserver and intraobserver reliability for the Mason classification system was noted in this study, it is important to note that reproducibility improved with the external rotational oblique view. The acquisition of this radiograph may help in the diagnostic workup of a radial head fracture. The limitation of plain radiographs to image the radial head is well recognized. When in question, advanced imaging with three-dimensional reconstruction can be quite helpful in understanding the true nature of the injury and degree of joint involvement, comminution and displacement.