Forensic expertise of thoracic aorta, heart and pericardial injuries in car-occupant fatalities

Introduction. Forensic expertise has not specified with certainty any specific injury among fatally injured frontal car-occupants in frontal car collisions. Objective. To establish if blunt injuries of thoracic aorta, heart, and pericardium could be used as predictors where the fatally injured car-occupant was at the moment of car-collision. Methods. A retrospective autopsy study was performed. The subjects were fatally injured car-drivers, front-seat and rearseat passengers in head-on car collisions. In each of them we analyzed the injuries of thoracic aorta, heart and pericardium. Results. 492 subjects were analyzed (378 male and 104 female): 239 car-drivers, 194 front-seat and 49 rear-seat passengers. The isthmus of aorta was the commonest site of simple blunt rupture among car-drivers and front-seat passengers. Among more than half of the observed subject, there was aortic blunt rupture as concomitant injury with heart and pericardium injuries. Heart and pericardium ruptures were most common among fatally injured car-drivers. Most frequently injured part of the heart was the right atrium. Injuries of thoracic aorta, heart and pericardium indicated a higher probability that the fatally injured would be the car-driver (λ=0.818; df=2; p=0.011, λ=0.906; df=2; p=0.000, and λ=0.951; df=2; p=0.000); this was also pointed out by the rupture of the right atrium and multiple ruptures of the thoracic aorta (λ=0.966; df=2; p=0.000 and λ=0.918; df=2; p=0.009). The concomitant injuries of the thoracic aorta with thoracic spine, sternum and heart pointed out that the injured person was the car-driver (λ=0.971; df=4; p=0.007, λ=0.974; df=4; p=0.013 and λ=0.958; df=4; p=0.000), as well as the concomitant injuries of heart and sternal fracture (λ=0.960; df=4; p=0.001). The probability of about 80% that the fatally injured person in head-on collisions was a car-driver was pointed out by concomitant blunt thoracic aorta rupture with fractured sternum and ribs (Wald. coeff.=8.611; df=1; p=0.003, and Wald. coeff.=3.875; df=1; p=0.049). Conclusion. The basic mechanism of the injury of thoracic organs is deceleration, as well as anteroposterior compression with caudorostral hyperextension. That is why thoracic organ injuries are mostly concomitant. Fatally injured car-drivers suffered more often of these injuries than other car-occupants. The probability that the fatally injured was the car-driver rises with the number of concomitant injuries of thoracic aorta, heart and pericardium, as well as with the fractured thoracic-cage bones.