Assessing Injury Prediction with Human Body Models: Application to Rib Fracture Risk Prediction Using SAFER HBM

As a consequence of the introduction of mathematical human body models (HBMs) in consumer information programs, there is an increased need for reliable methods that can demonstrate and build trust in the capability of HBMs to predict human response and injury risk in crashes. Therefore, a framework for validation of strain-based injury prediction is proposed. The framework comprises stepwise validation with the final step to validate the utility of risk predictions by means of the area under the curve (AUC) combined with Brier scores. SAFER HBM V11.1.0 previously validated at component and body part levels was selected for the demonstration of the final step of the framework to validate the capability to predict fracture risk in frontal, oblique, and lateral loading. For frontal loading, five postmortem human surrogate (PMHS) test series with 43 PMHS (age range: 19–88 years) were reconstructed. The predicted rib fracture risk for 2+ and 3+ fractured ribs was compared to the number of fractured ribs sustained by the PMHS. Using the framework, the SAFER HBM was for frontal impact analysis found capable of predicting 2+ fractured ribs with an AUC of 0.90 and 3+ fractured ribs with an AUC of 0.89. For oblique and lateral impacts, three PMHS test series including 47 PMHS (23 with 0, 22 with 2+, and 20 with 3+ fractures) were reconstructed, and SAFER HBM rib fracture risk predictions obtained AUC values of 0.84 and 0.87 for 2+ and 3+ fractured ribs, respectively. In the frontal load case, the Brier score was 0.14 for the Number of Fractured Ribs (NFR) 2+ model and 0.17 for the NFR 3+ model. In the lateral/oblique load case, Brier scores were 0.20 and 0.18 for the NFR 2+ and NFR 3+ models, respectively. The proposed framework is a suitable method to objectively assess the utility of HBM injury predictions, demonstrated with the SAFER HBMs capability to predict rib fracture risk.