Modification of C1-C2 transarticular screw fixation by image-guided surgery

Study Design. This is a feasibility study of image-guided surgery for C1-C2 transarticular screw fixation comparing postoperative screw position in a nonrandomized prospective cohort with a historic control group-in which flu oroscopic guidance was used alone. Objectives. To evaluate the potential benefits and disadvantages of image-g uided surgery for C1-C2 screw placement. Summary of Background Data. C1-C2 transarticular screw fixation is biomecha nically superior to of her current surgical stabilization procedures. The o riginal technique for C1-C2 screw placement relies on anatomic landmarks an d intraoperative fluoroscopy. Screw misplacement or anatomic variations can result in vertebral artery injury. image-guided surgery involves using com puted tomography (CTI data to plan the optimal screw trajectory before surg ery and then use this data to guide screw placement during the actual surge ry. Promising results of this technique are reported in the literature, but no direct comparison between image-guided surgery and conventional surgica l techniques has been previously reported. Methods. The image-guided surgery group consisted of 37 prospective patient s. The historic control group included 78 patients who had similar surgerie s performed using only fluoroscopic guidance. For the image-guided surgery group, subluxation was reduced by positioning at the time of CT examination . The CT data were transferred to a StealthStation (Sofamor-Danek, Memphis, TN) surgical planning and guidance computer system, and an optimal screw t rajectory was determined for the right and left transarticular screws. Afte r matching the surgical field to the virtual computer field, C2 was drilled according to the planned screw trajectory, and screws were placed. Plain r adiographs and CT were used for postoperative evaluation of the image-guide d surgery group. Results. Image-guided surgery reduced but did not eliminate the risk of scr ew misplacement. Surgical time was not increased overall. Conclusions. Image-guided surgery is an effective tool for the achievement of correct: screw placement in C1-C2 transarticular screw fixation procedur es. The procedure remains technically demanding.