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

We used a commercially available computer-assisted image-guidance system for cervical pedicle screw insertion in both the laboratory and in a preliminary clinical setting. Nine plastic cervical spine models (C2-C7) were used in the laboratory test. The StealthStation was used to create the preoperative plan for each screw such that it would be inserted down the center of the pedicle, parallel to the long axis. Using a light-emitting diode-equipped drill guide, 2-mm holes were drilled in 108 pedicles. A total of 108 pedicle holes were drilled. The mean trajectory deviation from the surgical plan in the axial plane was 1.7+/-1.7 degrees (range, 0 to 8 degrees), and the 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 pedicles, whereas partial cortical perforation was noted in 25 pedicles (23.1%). In the clinical setting, 36 cervical pedicle screws were inserted in nine patients using the image-guided system. Within the limits of imaging artifact, all 36 pedicle screws appear to have been inserted accurately by postoperative computed tomographic examination. No neurologic or vascular complications were encountered.