Objective:To evaluate the clinical value of posterior articular screwfixation in patients with atlantoaxial instability.Methods:From January 2005 to June 2009

43 patients in our hospital with atlantoaxial instability were treated by posterior screw fixation.The clinical values were accessed by radiographic imaging

JOA and VAS score in 5 years follow-up.Results:No intraoperative complication occurred in 43 patients.Postoperative X-ray film showed anatomical reduction in 39 patients

correction of most of dislocation in 4 patients

all the internal fixation were in good position.Spinal MRI showed spinal cord compression were back to normal.After 2 to 3 months

atlanto-axial were vertebraed.After 6 months

the patient’s cervical spine function(t=14.099

P=0.000)and pain conditions(t =19.335

P=0.000)were significantly improved compared with before surgery

the average improvement rate was 86.1%±5.2%.Conclusion:The posterior screw fixation in the treatment of atlantoaxial instability is effective and reliable

have less complications and can be used as an effective surgical procedure.