A Simple Intraoperative Method for Assessment of Pedicle Screw Trajectory Using Contrast Medium Injection

Abstract

Retrospective radiologic study. To introduce a novel method for intraoperative verification of the pedicle screw pathway using contrast medium injection. Various surgical techniques and equipments, such as, mechanical probing, intraoperative fluoroscopy, computer-assisted navigation system, and neurophysiological monitoring have been devised to assist accurate pedicle screw placement. However, pedicle screw misplacement remains of considerable concern, even to experienced spine surgeons. Fifty pedicle screws placed using the devised contrast medium technique in 39 consecutive patients were included. The authors used a contrast medium injection to verify pedicle screw tracts when pedicle wall violation was doubtful with conventional methods. Contrast medium (Iopamidol) was injected through the prepared screw path under fluoroscopic view. The screw path preparation was deemed successful when contrast medium was contained within the prepared screw tract. Pedicle screw placements were interpreted by postoperative computed tomography. Intraoperative verifications of pedicle screw paths using contrast medium technique showed that 6 of the 50 (12%) screw paths were disrupted, and these paths were redirected. Posteoperative computed tomography evaluations showed that 39 of the 50 (78%) screws were correctly placed. Of the 11 misplaced screws, 9 (18%) were interpreted as exhibiting cortical encroachment, and 2 (4%) as exhibiting mild frank penetration. The intraoperative injection of contrast medium provides a simple, fast, safe, and reliable means of verifying pedicle screw tract, when pedicle wall violation is doubtful.