Inter- and intra-observer agreement of the AO classification for operatively treated distal radius fractures

The reproducibility of the AO classification for distal radius fractures remains a topic of debate. Previous studies showed variable reproducibility results. Important treatment decisions depend on correct classification, especially in comminuted, intra-articular fractures. Therefore, reliable reproducibility results need to be undisputedly determined. Hence, the study objective was to assess inter- and intra-observer agreement of the AO classification for operatively treated distal radius fractures. A database of 54 radiographs of all AO types (A, B and C) and groups (A2-3, B1-3, and C1-3) of distal radius fractures was assessed in twofold. Likewise, a subset of 152 radiographs of solely C-type groups (C1-3) was assessed. All fractures were classified by six observers with different experience levels: three consultant trauma surgeons, one sixth-year trauma surgery resident, a consultant trauma radiologist, and an intern with limited experienced. The inter-observer agreement of both main types and groups was moderate (κ = 0.49 resp. κ = 0.48) in combination with a good intra-observer agreement (κ = 0.68 resp. κ = 0.70). The inter-observer agreement of the subset C-type fractures group was fair (κ = 0.27) with moderate intra-observer agreement (κ = 0.43). According to these results, the reproducibility of the AO classification of main types and groups of distal radius fractures based on conventional radiographs is insufficient (κ < 0.50), especially at group level of C-type fractures.