Study Design.An atlantoaxial fixation using bilateral C1-2 transarticular screws and C1 laminar hooks was employed in 64 consecutive patients with atlantoaxial instability, who were then followed for 12 to 17 months to evaluate the technique.Objective: To describe a modified posterior C1-2 fixation technique and preliminary clinical and radiographic results in the 64 consecutive patients.Summary and Background Data.The atlantoaxial instability caused by fractures, rheumatoid arthritis, congenital deformity or traumatic lesions of the transverse ligamentl often result in acute or chronic spinal cord compression.Even though conservative management could be appropriate for many patients, surgical intervention is usually necessary for these patients who suffer from serious atlantoaxial dislocations.Conventional posterior atlantoaxial fixations, such as Gallie and Brooks techniques, are frequently associated with high rates ofpseudoarthrosis and implant failure.The C1-2 transarticular screw fixation has been shown to be effective in treatment of atlantoaxial instability; however, this two-point fixation merely stabilizes the atlantoaxial motion segment laterally.A three-point fixation, composed with bilateral C1-2 transarticular screws and C1 laminar hooks, has been developed.Methods:From October, 2004 to October, 2007, 64 patients with atlantoaxial instability including 55 males and 9 female, ages 6 to 76 (average 53.9) years, underwent atlantoaxial fixation using bilateral C1-2 transarticular screws and C1 laminar hooks.The surgical technique and treatment procedures were intensively reviewed and clinical symptoms and imaging appearance were retrospectively evaluated.Results: Clinical follow-ups were obtained on 12 to 24 months (average 17 months) for all patients.At 3, 6, 12 months after surgery, all patients underwent the lateral flexion-extension view radiography and 3-D reconstruction CT images to confirm position of screws, atlantoaxial stability and fusion healing.(Fig.3).Of 128 C1-2 transarticular screws related to 64 patients, 6 (4.7%) screws cut out dorsally in the isthmus of C2; the malpositioned 6 screws are related to 3(4.5%) patients; fortunately, no signs of neurovascular injury and atlantoaxial instability occurred in the 3 patients during the follow-up term; as well as theit bone grafts were well fused at 3 months postoperatively.For the rest 122(95.3%) screws related to 61 patients, satisfactory positions were achieved; there were no unstable appearances in the atlantoaxial articulation (see Fig.3) in follow-up term; and the graft bone blocks were well fused at 3 mouths postoperatively.The neck pains were completely disappeared at 3 months postoperatively; the 9 patients suffering form neurological deficits achieved a significant relief at 3 months postoperatively.There were no cases of neurovascular impairments related to the procedure at follow-up No instance of dural laceration or vertebral artery injury was observed; and there were no wound infections and cases of implant failure.Conclusions:Fixation of the atlantoaxial articulation using bilateral C 1-2 transarticular screws and C1 laminar hooks appears to be a reliable technique for treatment of atlantoaxial instability.