Non-union of fractures of the atlas.

Eighteen patients who had a fracture of the atlas were evaluated clinically and by computed axial tomography an average of forty-six months (range, two to 164 months) after injury. The purpose of the evaluation was to determine the effect of the pattern of the fracture, the quality of osseous healing, and the method of primary immobilization on the long-term outcome. Three (17 per cent) of the patients had a non-union, and two of them had a poor clinical result. These two patients had had a unilateral comminuted fracture--that is, one fracture that was anterior and one that was posterior to the lateral mass, with an associated osteoperiosteal avulsion of the transverse ligament on the same side of the ring of the atlas. Six (33 per cent) of the eighteen patients had an osteoperiosteal avulsion of the transverse ligament. The avulsions usually progressed to osseous union. Rupture of the mid-substance of the transverse ligament was uncommon. No patient had a neurological deficit or late neurological sequelae that were directly attributable to the fracture of the atlas.