Accuracy of atlantoaxial transarticular screw insertion

Study Design. The accuracy and safety of atlantoaxial transarticular screw insertion were evaluated in clinical cases. Objectives. To evaluate the accuracy and safety of :atlantoaxial transartic ular screw insertion under lateral fluoroscopic monitoring without opening the joint. Summary of Background Data. Atlantoaxial transarticular screw fixation has been reported to be biomechanically superior to posterior atlantoaxial wiri ng techniques. Several clinical series have been reported in the literature . In some reports, the risk of screw insertion in this technique has been p ointed out. Materials and Methods. Fifty-six consecutive patients with atlantoaxial ins tability were treated by transarticular screw fixation. One hundred twelve screw insertions in these 56 patients were assessed by surgical record and computed tomographic examination. One screw could not be inserted because o f the difficulty of adequate placement during operation; 111 screws were th erefore inserted. Adequate position was defined as when the screw perforate d the lateral atlantoaxial joint. Results. In this series, neither vertebral artery injury nor spinal cord in jury was experienced clinically. One guide wire was broken during drilling with a cannulated drill. Computed tomographic examination demonstrated that 106 screws perforated the atlantoaxial joint. Therefore, 95.5% of screws w ere adequately positioned. There were two screws positioned lateral to the joint, two medially, and one anteroinferiorly to the joint. Conclusions. Atlantoaxial transarticular screw insertion using image intens ifier without opening the lateral joint was performed safely, but not accur ately, in all cases.