Radiographic evaluation of partial articular radial head fractures: assessment of reliability

Historically, treatment of partial articular radial head fractures has hinged on radiographic assessment and application of the Mason classification. The inter- and intra-rater reliability of radiographic assessment and classification of radial head fractures may be lower than previously reported. We hypothesized that radiographic assessment leads to an underestimation of the number of fragments, percentage of articular surface involved, and displacement in millimeters.

We performed a retrospective review of all Mason II radial head fractures treated at our institution. Four independent observers performed radiographic assessment of the cohort. An independent observer performed these measurements on high-resolution computed tomography (CT) imaging, the reference standard. Radiographic assessments were then correlated with the CT findings using Pearson's correlation coefficient and Kappa statistic, where indicated.

Fifty-nine Mason II radial head fractures were reviewed. These results were not impressive, with all comparisons showing a Kappa statistic less than 0.5 (ie, weak agreement). Intra-rater reliability was similar: displacement (measured by Pearson's correlation coefficient) was 0.58, percent articular involvement was 0.74, and the number of fragments (measured by the Kappa statistic) was 0.28. Fracture displacement was generally underestimated on radiographic measurements when compared to CT scan. Nearly half (45%) of all cases demonstrated inaccurate fragment number assessment when compared to the reference standard.

Radiographs show poor inter- and intra-observer reliability for determining radial head fracture morphology. Assessment of the number of fragments was particularly inaccurate. High-resolution CT should be considered for patients with Mason II radial head fractures, especially in cases of poorly visualized fracture characteristics or borderline amounts of displacement, in an effort to appropriately indicate patients for the variety of treatment options available today.