Which of the following injuries would MOST likely occur as a direct result of the third collision in a motor vehicle crash?

• A. Extremity fractures
• B. Forehead lacerations
• C. Flail chest
• D. Aortic rupture

Answer: (D)

In a crash, three collisions can occur: the vehicle hits something, the occupant hits the inside of the vehicle, and then the internal organs collide with solid structures inside the body during rapid deceleration. The third collision involves these internal organs being forced against the body’s structures, and the aorta is particularly vulnerable because it is tethered and experiences strong shear forces during sudden stop. This makes aortic rupture the most likely direct injury from that final collision.

The other injuries listed tend to arise from the second collision, when the body itself strikes the interior of the car—like the head hitting the windshield causing forehead lacerations, or the chest being driven against the seat or steering wheel producing a flail chest, or the limbs absorbing impacts and fracturing—rather than from the internal deceleration of the third collision.