[Isolated fracture of the lateral mass of the atlas: a case report].

Isolated fracture of the lateral mass of the atlas is extremely rare. The authors report such a case because of its rarity and to emphasize the usefulness of computed tomography (CT) for its diagnosis. The case was that of a 63-year-old male, who had been hit on his left parietal region by a board falling from behind, and which forced him to hyperflex his neck. He complained of neck pain on arrival at our hospital without any resulting neurological deficits. Routine plain cervical spine films were normal, but CT scan revealed a vertical fracture of the lateral mass of the atlas. He was placed in a Halo brace for several months, and after 3 months the fracture was seen, by CT scan, to have healed without complications. Fractures of the atlas are uncommon. They comprise 2-13% of all fractures of the cervical spine, and about 1.3% of the fractures of the entire spinal column. An isolated fracture of the lateral mass of the atlas has been reported only in seven cases including our case previously and this is the first case in which CT scan could make the diagnosis. We emphasize that CT scan is a most useful tool for the diagnosis of the fracture.