Axial loading with hyperflexion injury to the atlas resulting in crushed lateral masses.

A 40-year-old man was involved in an ATV accident, in which he landed on the top of his head. There was no neurological deficit. A plain radiograph showed prevertebral soft tissue swelling at the atlas and axis level.

Horizontal fracture of the anterior arch of the atlas associated with a congenital cleft of the anterior arch.

We report a rare combination of a horizontal fracture of the anterior arch of the atlas associated with a congenital cleft of the anterior arch. Sagittally reformatted computed tomography (CT) images demonstrated a fracture of the anterior arch of the atlas and a type II odontoid process fracture. There was also a smoothly marginated midline cleft of the anterior arch just above the fracture consistent with a congenital variant.