Effects of binary decision making on the classification of fractures of the ankle

Objective: To evaluate the effect of binary decision making on interobserver reliability in the classification of fractures of the ankle. Design: Radiographic review study. Patients/Participants : Observers: two PGY-2 orthopaedic residents, two PGY-5 residents, and two orthopaedic attending surgeons. Intervention: Radiographs of fifty ankle fractures were classified. Each observer classified the radiographs by using the original AO/ASIF system and its recent binary modification. Main Outcome Measurements: Interobserver reliability was assessed by using a kappa coefficient and compared for the two classification methods. Results: The mean kappa value for interobserver reliability for type only and for type and group classification when using the original AO/ASIF system was 0.77 and 0.61, respectively. Using binary decision making, the mean kappa values for type only and for type and group were 0.78 and 0.62, respectively. There was no statistically significant difference in reliability between the original and binary classification systems. Conclusion: The interobserver reliability of both the original AO/ASIF classification system and its binary modification is substantial. The results of the present study, however, cast doubt on the effectiveness of binary decision making in improving interobserver reliability in the classification of fractures. To our knowledge, this study is the first to compare the original AO/ASIF classification system with its binary modification. Additional study of other fractures may help elucidate the effectiveness of binary decision making in improving interobserver reliability in the classification of all fractures.