A new technique for the surgical treatment of atlantoaxial instability: C1 lateral mass and C2-3 transfacet screwing

Abstract

Atlantoaxial instability is a special entity that may be caused by many disorders such as trauma, tumor, arthritis, congenital malformation and infection. Atlantoaxial fixation is needed to provide stability, prevent neurological deficits and correct deformity. The aim of this report is to introduce an alternative technique for the treatment of atlantoaxial instability in patients who have vertebral artery anomaly, anomalous C2 or osteoporosis. C1-2-3 fixation was performed in a 50-year-old male patient with atlantoaxial instability due to os odontoideum. C1 lateral masses were identified and screw placement was performed. C2 facet joints were identified bilaterally. The superior margin of the junction of pedicle and the lamina was used as the entry point and 3.5x22 mm screws were inserted from C2 facet joint to the C3 facet joint in the mediolateral and craniocaudal direction under fluoroscopic guidance with caution. The posterior fixation screws were interconnected with two rods. Finally, autologous grafts were placed posterolaterally to encourage the fusion. The patient"s complaints were relieved after the surgery. C1-C2 instability was not seen in the postoperative radiological examinations. In the surgical treatment of C1-2 instability, our technique could help reduce the possibility of vertebral artery injury in patients who have a vertebral artery course anomaly or when it is difficult to place C2 pedicle screws due to anomalous C2 pedicles and osteoporosis. High fusion rate could be achieved with this technique due to passing through the four cortical surfaces. No wire or allograft was required. Thus, the instrumentation cost could be reduced.