Virtual Fluoroscopy for Cervical Spine Surgery
Y. Raja Rampersaud, MD (Toronto, Ontario)
David A.Simon, PhD (Broomfield, CO)
Thomas H. Jansen, MSc (Memphis, TN)
Introduction:
The purpose of this study was to evaluate the utility of virtual fluoroscopy for cervical spine surgery.
Methods:
The following procedures were performed on three fresh cadavers: 1) odontoid screw placement, 2) lateral mass screw placement (C3–C6, bilaterally), and 3) three–level anterior cervical corpectomy with plating. All procedures were done using standard surgical exposures and techniques. Procedural guidance was achieved using the FluoroNav virtual fluoroscopy system. The head was secured in a Mayfield apparatus equipped with a dynamic reference arc. True AP and lateral fluoroscopic images of the cervical spine were obtained using a standard OEC Model 9600 C–arm fitted with a calibration target. Each image was automatically calibrated and the C–arm was then removed from the surgical field. Locations of optically–tracked tools were graphically projected onto the pre–acquired fluoroscopic images in real–time. Following the procedures, AP and lateral radiographs and CT scans were obtained. Linear and angular measurements were made using these studies.
Results:
Anatomic correlation of real and virtual tool tips was excellent. AIl odontoid screws were placed properly on post–procedure axial CT images and on AP and lateral films. The average lateral angular deviation of lateral mass screws relative to the mid–sagittal plane was 30.5(. The average corpectomy trough width was 16.8 mm. Troughs were symmetric with regard to the midline and their sidewalls were parallel to the mid–sagittal plane. AII anterior cervical plates were midline.
Discussion:
Virtual fluoroscopy offers several advantages over conventional techniques. Multiplanar guidance is possible using a single C–arm. Tool position can be updated in real–time without acquiring new fluoroscopic images, minimizing radiation exposure and ergonomic challenges. We conclude that virtual fluoroscopy is feasible for cervical spine surgery.