The clinical risk of vertebral artery injury from cervical pedicle screws inserted in degenerative vertebrae

Study Design. Postoperative outcomes of cervical pedicle screw (CPS) placement were evaluated. The screws were inserted in degenerative vertebrae using anatomic landmarks. Objective. To evaluate the risks of this procedure caused by misplacements and subsequent complications. Summary of Background Data. The CPS gives superior vertebral fixation but risks causing vertebral artery and spinal cord injury. However, few clinical reports have been published concerning CPS misplacement and subsequent complications. Therefore, the risk of this procedure is still unclear. Methods. There were 18 consecutive patients, who submitted to CPS fixation of degenerative vertebrae C2 - C6, evaluated using computerized tomography (CT). In 5 of 9 patients in whom the screw critically violated the transverse foramen, viability of the vertebral artery was evaluated using multi-detector row CT angiography. Results. There were no intraoperative vertebral artery or spinal cord injuries and no serious postoperative complications. A total of 86 screws were inserted, and 25 (29%) breached the pedicle cortex. Of them, 84% deviated laterally and violated the transverse foramen. There were 13 screws (15%) that deviated more than 2 mm. However, multi-detector row CT angiography showed the continuity of the vertebral artery in all cases. Conclusions. The deviation rate of CPS placement using anatomic landmarks was higher than anticipated, although no serious complications were encountered. Refinement of the technique ( e. g., using a computer-assisted navigation system) is strongly recommended.