Comparison of the AO/OTA 1996/2007 and 2018 pelvic ring fracture classifications

Pelvic ring fractures may present with relevant mechanical and haemodynamic instability. Classifications of the bony or ligamentous injuries of the pelvic ring are well established. The most common classifications used analyse the injury mechanisms and the resulting instability of the pelvic ring structure. Fracture classifications should be simple and easy to use, comprehensive, and radiographically and anatomically based, resulting in a hierarchical alphanumeric order of types and subtypes and thereby allow adequate treatment decisions based on a high degree of inter- and intraobserver reliability. In 2018 a new AO/OTA pelvic ring fracture and dislocation classification was published that combined the most commonly used "historical" classification schemes, e.g. the Tile/AO classification and the classification according to Young and Burgess. Compared with these older classifications, several relevant changes were integrated in the 2018 edition. The changes between the AO/OTA 1996/2007 and 2018 classifications were analysed in detail. Overall, several problems were identified regarding the type-B pelvic ring injury classification. These changes may result in difficulties in classifying pelvic ring injuries and thereby prevent relevant comparisons between former and future clinical studies on pelvic injuries.Level of Evidence: V.