Accuracy of the WSES classification system for pelvic ring disruptions: an international validation study

Background: In 2017, a novel classification for pelvic injuries was established by the World Society of Emergency Surgery (WSES). We validated its effectiveness using nationwide real-world data. The roles of associated vascular injury and open fracture in this system were also evaluated. Methods: Patients with pelvic fractures in the National Trauma Data Bank 2015 dataset were retrospectively studied. First, the mortality rates were compared by WSES classification. Second, independent predictors of mortality were evaluated using a multivariate logistic regression model. Patients with and without associated vascular injuries and the same hemodynamic and pelvic ring stability statuses were compared. Patients with associated vascular injuries were compared to the proportion of nonsurvivors and survivors with unstable pelvic ring injuries. Third, the outcomes were compared between patients with open pelvic fracture and closed pelvic fracture in the mild, moderate and severe WSES classes. Results: During the 12-month study period, 44,163 blunt pelvic fracture patients were included. The mortality rates were 1.8%, 3.8% and 10.6% for the mild, moderate and severe WSES classes, respectively (p < 0.001). MLR analysis showed that unstable pelvic ring injury did not significantly affect mortality (p = 0.549), whereas open pelvic fracture and associated vascular injury were independent predictors of mortality (odds of mortality: open pelvic fracture 1.630, p < 0.001; associated vascular injury 1.602, p < 0.001). Patients with associated vascular injuries showed that there was no significant difference in the proportion of patients with unstable pelvic ring injuries between survivors and nonsurvivors (37.2% vs. 32.7%, p = 0.323). In all three classes, patients with open pelvic fractures had significantly higher mortality rates and infection rates than patients with closed fractures (mortality rates: minor 3.5% vs. 1.8%, p = 0.009, moderate 11.2% vs. 3.3%, p < 0.001, severe 23.8% vs. 9.8%, p < 0.001; infection rates: minor 3.3% vs. 0.7%, p < 0.001, moderate 6.7% vs. 2.1%, p < 0.001, severe 7.9% vs. 2.8%, p < 0.001). Conclusions: Based on this nationwide study, the WSES guideline provides an accurate and reproducible classification of pelvic fractures. It is recommended that open/closed fractures and associated vascular injuries be evaluated as supplements of the WSES classification.