[Post-traumatic instability between the atlas and the axis in children. Apropos of 5 cases].

The authors have observed 5 cases of atlanto-axial instability in children aged from 18 months to 8 years. All the cases were seen after severe trauma and presented with abnormal neurological signs. All patients were first treated conservatively and were operated on secondarily by atlanto-axial fusion using graft and wiring for persistent radiological instability between the atlas and axis. In two cases instability was due to an atlanto-axial subluxation with rupture of the transverse ligament; one of these was reduced by traction. In one case there was an anterior subluxation without fracture. In one case there was a fracture of the odontoid process in which instability persisted in spite of bony union of the fracture. In the last case, the odontoid process was intact shortly after the trauma but its central portion disappeared secondarily. The cause of this disappearance is discussed.