Intra- and inter-rater reliability of a three-dimensional classification system for intertrochanteric fracture using computed tomography

Abstract Introduction : Intertrochanteric fractures are common fragility fractures in elderly patients. The importance of a reliable classification system for these fractures has been increasingly recognized. The aim of this study was to test the hypothesis that three-dimensional classification by CT has better intra- and inter-observer reliability than conventional two-dimensional classification. Material and Methods : Two hundred and three consecutive patients (39 male, 164 female; mean age 84.5 years) with intertrochanteric fracture were included in the study. In each case, the fracture was classified using the two-dimensional Evans-Jensen and AO/OTA systems that rely on plain radiographs and using a three-dimensional fragment-based CT system. The second evaluation was performed 1 month after the first evaluation by the same examiner to determine intra-observer reliability. Another blinded examiner also classified each case to assess inter-observer reliability. The kappa coefficient was used for determination of intra- and inter-observer reliability. Results : The kappa values for the two-dimensional Evans-Jensen and AO/OTA classification systems showed moderate intra-observer reliability (κ=0.65 and κ=0.61, respectively) and slight inter-observer reliability (κ=0.20 and κ=0.19). The intra-observer kappa value for the three-dimensional classification system was 0.88, indicating almost perfect reliability; the inter-observer kappa value was 0.70, indicating substantial reliability. Conclusion : The findings of this study confirm that the fragment-based classification system has high reliability. Surgeons should be aware that the three-dimensional fragment-based CT system for classification of intertrochanteric fractures has better intra-observer and inter-observer reliability than the conventional two-dimensional systems.