Cervical pedicle screw insertion: Assessment of safety and accuracy with computer-assisted image guidance

We used a commercially available computer-assisted image-guidance system fo r cervical pedicle screw insertion in both the laboratory and in a prelimin ary clinical setting. Nine plastic cervical spine models (C2-C7) were used in the laboratory test. The StealthStation was used to create the preoperat ive plan for each screw such that it would be inserted down the center of t he pedicle, parallel to the long axis. Using a light-emitting diode-equippe d drill guide, 2-mm holes were drilled in 108 pedicles. A total of 108 pedi cle holes were drilled. The mean trajectory deviation from the surgical pla n in the axial plane was 1.7 +/- 1.7 degrees (range, 0 to 8 degrees), and t he mean deviation of the position of the hole was 1.7 +/- 0.6 mm (range, 0. 1 to 2.9 mm). Eighty-three drill holes (76.9%) were contained within the pe dicles, whereas partial cortical perforation was noted in 25 pedicles (23.1 %). In the clinical setting, 36 cervical pedicle screws were inserted in ni ne patients using the image-guided system. Within the limits of imaging art ifact, all 36 pedicle screws appear to have been inserted accurately by pos toperative computed tomographic examination. No neurologic or vascular comp lications were encountered.