Reliability of the AO/ASIF classification for pertrochanteric femoral fractures.

20 radiographs of pertrochanteric femoral fractures were classified as to fracture "group" and "sub-group" according to the AO/ASIF Fracture Classification (type 31A) by 15 observers. 3 months later, the same radiographs were reviewed by the same observers. Mean agreement of the observers with the final consensus ranged from 53% (with subgroup classification) to 81% (without subgroup). The mean kappa value for interobserver reliability was 0.33 and 0.34 for classification with subgroup in both observer sessions, respectively. Omission of the subgroup classification resulted in better mean kappa values (0.67 and 0.63, respectively). Mean intraobserver reliability was 0.48 in the fracture "subgroup" and 0.78 in the "group" classification. In conclusion, the results show that the AO/ASIF classification for pertrochanteric fractures is reliable for fracture subgroups 31A1, A2 or A3. The group classification should be used to compare scientific data and determine the best treatment. Further classification of fracture subgroups leads to poor reproducibility of results.