Experience of posterior surgery in atlanto-axial instability.

Twenty patients with atlanto-axial instability treated by posterior spinal fusion were reviewed. Patients with atlanto-axial instability due to congenital causes usually presented late with chronic myelopathy and treatment in these patients was associated with poor surgical results. Atlanto-axial fusion for fracture non-unions offers immediate stability, reliability, few complications, and good range of neck movement after surgery. Occipito-cervical fusion is indicated whenever atlanto-axial fusion is surgically not feasible.