Ring fracture of the base of the skull and atlanto-occipital avulsion due to anteroflexion on motorcycle riders in a head-on collision accident.

This report concerns a head-on collision accident of a motorcycle at a very high speed (c. 80-100 Km/h) against a bonnet-type automobile, in which both the motorcyclist and pillion rider were injured at the base of the skull by violent anteroflexion of the head due to the force of inertia. A difference in their injuries was: the motorcyclist sustained a 'ring' fracture and the pillion rider an atlanto-occipital avulsion; dural tear. Anteroflexion without impact on the occiput such as described above seems to be a rare causal mechanism of the 'ring' fracture. In addition, the mode of action of the accelerating forces to the heads of the victims along with their physiques may explain the mechanism which caused the different injuries in this accident.