Is it time to revisit the AO classification of fractures of the distal radius? Inter- and intra-observer reliability of the AO classification.

We conducted an observational radiographic study to determine the inter- and intra-observer reliability of the AO classification of fractures of the distal radius. Plain posteroanterior and lateral radiographs of 456 patients with an acute fracture of the distal radius were classified by a consultant orthopaedic hand specialist and two specialist trainees, and the k coefficient for the inter- and intra-observer reliability of the type, group and subgroup classification was calculated. Only the type of fracture (A, B or C) was found to provide substantial intra-observer reliability (k type 0.65). The inclusion of 'group' and 'subgroup' into the classification reduced the inter-observer reliability to fair (kgroup 0.29, ksubgroup = 0.28) and the intra-observer reliability to moderate (kgroup 0.53, ksubgroup 0.49). Disagreement was found to arise between specific subgroups, which may be amenable to clarification.