Traumatic Rupture of Thoracic Aorta in Real-World Motor Vehicle Crashes

Abstract

Objective. Traumatic rupture of thoracic aorta (TRA) was reported in the literature to be a major cause of death in motor vehicle crashes. This study aims at evaluating the most relevant risk factors of TRA. It also aims at analyzing the types of TRA as a function of car crash conditions and rib cage fractures.

Methods. In-depth crash data collected from 1998 to 2006 as part of the Co-operative Crash Injury Study (CCIS) were retrospectively investigated to assess frontal, near-side, and far-side injury risks. This database includes 15,074 occupants with individual detailed autopsy reports. Multivariate statistical analyses were performed. The influence of the following variables on TRA occurrence was studied: gender and age of the involved occupant, ETS, compartment intrusion, and restraint system. Features of TRA and rib cage fractures were described thanks to autopsy data.

Results. Although TRA occurred in only 1.2% of all occupants, TRA victims accounted for 21.4% of all fatalities. The incidence of TRA was found twice higher in side impacts (2.4%) than in frontal ones (1.1%). TRA injury risk increased with ETS, intrusion, and age and decreased with the absence of intrusion regardless of the impact direction. It also decreased for belted occupants in frontal impacts.

Except for the site of injury, the TRA features were similar whatever the crash conditions. The multiple ribs fractures were the most common injuries associated with TRA (79.1%) and TRA victims with uninjured or slightly injured (AIS 1) rib cage were significantly younger (p < 0.0001) than other TRA victims. Whatever the impact type, the TRA victims sustained mostly bilateral rib fractures (68%). Results also emphasized a close relationship between the principal direction of force and the body side with more fractured ribs. However, whatever the impact type, the aortic injury site or the side of the thorax, fractures concerned mainly the 2nd up to the 7th ribs of TRA victims.

Conclusions. This study emphasized four main variables influencing the TRA occurrence: ETS, compartment intrusion, age, and seat belt use. The results suggested that the injury site may be different depending on the occupant or the impact type. However, the typical TRA, i.e., a partial or complete aorta transection within the peri-isthmic region, affected any occupant independently of age and impact type. The high frequency of bilateral rib cage fractures observed in TRA victims and the significant influence of intrusion on TRA occurrence emphasized that the aortic injury mechanism mainly involves a severe direct chest impact or compression.

Keywords:

• Thoracic Aorta
• Traumatic Rupture
• Equivalent Test Speed
• Age
• Intrusion
• Rib Fracture

ACKNOWLEDGMENTS

This study was funded by the French Centre National de la Recherche Scientifique (CNRS, National Center for Scientific Research). The authors would like to thank the Transport Research Laboratory, the Loughborough University, the University of Birmingham, and the Vehicle Inspectorate Agency who provided the in-depth crash data analyzed in the present study.

Notes

∗Incidence = n_{TRA victims}/n_Involved∗100.

^$t = 1.9606 for 3468-5 degrees of freedom.

^#P-value of chi-squared tests (H1: coefficient different from zero);

∗∗∗ < 0.001;

∗∗< 0.01;

∗ < 0.05.

^$ t = 1.9630 for 782-4 degrees of freedom.

^# P-value of Chi-squared tests (H1: coefficient different from zero);

∗∗∗ < 0.001;

∗∗ < 0.01;

∗ < 0.05.

^$ t = 1.9636 for 658-4 degrees of freedom.

^# P-value of chi-squared tests (H1: coefficient different from zero);

∗∗∗ < 0.001;

∗∗ < 0.01; ∗ < 0.05.