Image-guided spinal surgery: Technology, operative technique, and clinical practice

Abstract

The complications associated with misplaced pedicle screws are mostly neurological or vascular. Previous studies of surgical procedures have shown a significant rate of incorrect placement of pedicle screws, ranging from 15% to 40%. To increase the safety of screw placement, a technique that combines preoperative computed tomography (CT) imaging with intraoperative passive navigation is proposed. A combination of registration algorithms is used to match the preoperative model of the vertebra with intraoperative points that are obtained by using a pointer and a 3-dimensional optical localizer. Images and optimal trajectories are then reported in the intraoperative space. The tip and axis of any surgical tool or guide is visualized in real-time in the volume of preoperative CT images to perform the computer-assisted drilling procedure. Ninety-six pedicle screws have been inserted in lumbar and thoracic vertebrae (from T10 to L5) for various spine disorders with the computer-assisted system. Surgery was followed by postoperative radiographs and CT scans, on which measurements of screw position relative to pedicle could be performed. Nine percent to 12% penetration is obtained with the computer-assisted technique; 44% is obtained with the manual insertion. Preoperative errors from the CT scan data (image gap) and intraoperative errors that occur during the collecting of point coordinates may explain the computer-assisted technique failures. The results clearly show that the computer-assisted surgery technique provides much better safety and accuracy than manual insertion. This technology is evolving rapidly and many new extensions will occur in the years to come.