Posterior spinal fusion was done on the patients with Atlanto-Axial instability. Total sixteen cases included six cases of fracture of the Dens, seven cases of Atlanto-Axial subluxation and three cases of Atlanto-Axial subluxation with Os odontoideum. Surgery was done with modified Brooks method on eleven cases and with McGraw method on five cases. Results are as followes.
1) Good solid fusion was achieved in all cases who underwent modified Brooks' method surgery and the synptom improved in all cases except for one case who claimed residual occipital neuralgia.
2) Recurrent anterior slip with residual synptom after removing the Halo-Brace was experienced in one case who underwent McGraw' method surgery.
3) Modified Brooks method is not indicated in the case with severe instability and high risk of intraoperative posterior slip.
4) Halo-Brace seemed to be necessary for Atlant-Axial fixation before, during and after the surgery.
