Mechanisms of aortic blunt rupture in fatally injured front-seat passengers in frontal car collisions: an autopsy study

We tried to explain the mechanisms of the aortic blunt ruptures in fatally injured drivers and front passengers, unrestrained by seatbelts, by analyzing the frequencies of both aortic ruptures and concomitant injuries to 12 organs and body regions. The sample consisted of 393 subjects: 251 drivers and 142 front passengers (325 male and 68 female passengers, the mean age 41.0 +/- 15.5). The total number of the complete blunt aortic ruptures in the sample was 116 (80 in the drivers and 36 in the front passengers). The weakest part of the aorta seems to be the isthmus (47 isthmus ruptures in the drivers and 27 in the front passengers). The statistically significant concomitant injured organs and body regions with the aortic ruptures were the liver, the sternum, and the diaphragm in the car drivers and the head and the neck in the front passengers. According to these results, the mechanisms of thoracic aorta rupture are different for fatally injured drivers and front passengers. For car drivers, they are associated and simultaneous with both thoracic and abdominal compression due to deceleration of the body at the moment when the driver's body slides forward and flexes across and against the steering wheel. For the front passengers, the mechanism is the caudorostral hyperextension of the thoracic aorta at the moment when the body is stopped by a dashboard, but the head continues forward with great velocity: the carotid vessels pull the aortic arch forward at the same time as the intercostal arteries fix the thoracic part of the aorta and pull it downwards.