Inter- and intra-observer reliability of the new AO/OTA classification of proximal femur fractures

A B S T R A C T Introduction: Hip fractures are a global health burden, with an incidence that is projected to increase from 66,0 0 0/year currently in the United Kingdom to 10 0,0 0 0/year by 2033. The classification of intertrochanteric fractures is key to the treatment algorithms advising on their surgical management. The AO/OTA classification is the most commonly used system, initially published in 1990 and subsequently shown to have poor inter-and intra-observer reliability, it was revised in 2018 with the main aim of re-classifying and further defining the 31-A2 group. Methods: 150 plain film anteroposterior and lateral plain film radiographs of intertrochanteric fractures from three hospitals were classified using the 2018 AO/OTA classification of intertrochanteric fractures by six Orthopaedic Surgeons (2 Consultants, 4 Trainees), all were blinded to the definitive surgical treatment for patients. Radiographs were re-classified after a minimum of 3-months, Cohen's Kappa for inter observer reliability was calculated from first round classifications and intra-observer reliability from first and second classifications. Results: Mean Kappa for inter-observer reliability for AO group classification (e.g. 31-A1) was 0.479 (0.220 0.771, for sub-group classification (e.g. 31-A1.1) reliability reduced to 0.376 (0.276 0.613). Intraobserver reliability was comparable for both group and sub-group classifications, 0.661 and 0.587 respectively. Conclusions: The revised 2018 AO/OTA classification aimed to simply the classification of intertrochanteric fractures, however it remains unreliable with only a moderate inter-observer reliability at group level with this falling to fair when sub-group classifications are made. Identification of stable and unstable injuries using the new AO/OTA system remains fraught with difficulties and appears difficult to apply with consistent accuracy. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study measured the reliability of the 2018 AO/OTA classification for intertrochanteric fractures among observers. Results showed a moderate inter-observer reliability at the group level and fair reliability at the subgroup level, indicating uncertainty in the diagnosis of intertrochanteric fractures using this classification.