Investigation of Risk Factors Contributing to the Occurrence of Posterior Rib Fractures

Abstract

Posterior rib fractures are clinically important because they are associated with severe thoracic trauma and increased risk of intrathoracic complications, yet their biomechanical etiology remains incompletely understood. This study investigated factors contributing to posterior rib fractures by combining three complementary data sources: selected real-world crash cases from RASSI and CIREN, computed tomography analyses of four PMHS that sustained posterior rib fractures in frontal impacts, and a parametric simulation study using the VIVA+ human body model. The real-world cases showed that posterior rib fractures may occur both after direct posterior loading and in crashes dominated by distributed thoracic compression without clear posterior contact. In the PMHS analyses, Hounsfield unit measurements at the costovertebral and costotransverse joints were generally higher than those of vertebral cancellous bone, and elevated values often coincided with fractured levels. In the simulations, increased stiffness at the rib-spine connections and intervertebral joints shifted strain toward rib regions closer to the spine and increased model-predicted rib fracture risk. These findings support the hypothesis that local thoracic stiffening may contribute to posterior rib fractures under compressive loading. The results are exploratory and support further validation using larger datasets and subject-specific modeling.