Interobserver Reliability of Schatzker, AO Foundation-Orthopaedic Trauma Association, and Luo Classifications for...

Objective To assess the interobserver agreement of the most widely used classification systems (Schatzker, AO Foundation-Orthopaedic Trauma Association (AO-OTA), and Luo) and investigate the impact of multiplane CT scans on their reliability. Methods Twelve raters (seven consultants and five senior trainees) were invited to classify 25 cases of tibial plateau fracture randomly selected out of a large database. Initially, they were asked to classify the fracture according to Schatzker, AO-OTA, and Luo based on plain anteroposterior (AP) X-ray and axial CT images. This procedure was applied for 25 cases consecutively. Next, the raters are given access to the multiplanar CT views of the same cases and were requested to reclassify each case. The interobserver agreement was calculated using the Fleiss kappa coefficient. Results An overall fair inter-rater agreement was observed for the Schatzker classification based on the plain AP X-ray (k=0.361) with a slight improvement after three-dimensional (3D) plane CT views (X-ray: k=0.361; 3D CT: k=0.364). For the AO-OTA classification, the relevant values were 0.204 and 0.231 based on plain X-ray and multiplanar CT, respectively. Finally, the Luo classification achieved the highest scores among the three classification systems (k=0.498), but its inter-rater agreement can still be characterized as moderate. No statistically significant improvement in the interobserver agreement was found for any classification even if only the consultants' subgroup was included in the data analysis. Conclusion All three classification systems failed to achieve a substantial agreement among the raters, with only a nonsignificant improvement after providing advanced imaging. This finding reflects the intrinsic weaknesses of the classification systems themselves rather than the disagreement on the fracture pattern due to unsatisfactory imaging.