Validation of the modified AO sternum classification system.

INTRODUCTION: The Arbeitsgemeinschaft für Osteosynthesefragen (AO) foundation along with the Orthopaedic. Trauma Association (OTA) introduced a new classification for sternal fractures in 2018 aiming to provide greater uniformity and clinical utility for the surgical community. A previous validation study identified some critical issues such as the differentiation between type A and B fractures and localization of the fracture either in the manubrium or in the body. Due to the moderate agreement in inter- and intra-observer variability, some modifications were proposed in order to improve the performance of the classification. The aim of this study was to re-assess the inter- and intra-observer variability after adding modifications to the classification. Our hypothesis was that a significative improvement of inter- and intra-observer variability could be achieved. MATERIAL AND METHODS: Twenty computed tomography (CT) scans of patients with sternal fractures were analyzed by six. Junior and six senior surgeons independently. Two assessments were performed with an interval of 6 weeks. The kappa (K) value was calculated in order to assess inter- and intra-observer variability. RESULTS: The overall mean kappa value for inter-observer variability improved from 0.364 to 0.468 (p < 0.001). Inter-observer variability mean for location was 0.573 (SD 0.221) and for type was 0.441 (SD: 0.181). Intra-observer variability showed a mean of 0.703 (SD: 0.153) with a statistic significant improvement when compared to the previous study (mean 0.414, SD: 0.256, p < 0.001). CONCLUSIONS: By modifying the AO/OTA classification of sternal fractures, the inter- and intra-observer variability improved and now shows moderate to substantial agreement.