Evaluating Atlantoaxial Anatomy and Screw Placement with Three-Dimensional Cone-Beam Computed Tomography

Objective: Accurate imaging of atlantoaxial disorders is essential to patient selection, intraoperative management and postoperative assessment of screw placement. We describe the fi rst application of the C-arm mounted Siemens Multistar Image Intensifi er cone-beam computed tomography (CT) system in the surgical management of atlantoaxial disorders. Materials and Methods: Pre- and postoperative imaging using the Siemens Multistar system and conventional helical CT imaging was performed to evaluate six patients requiring either transarticular C1-2 or odontoid screw fi xation. The accuracy of the Siemens Multistar system was compared with conventional helical CT with respect to perioperative clinical utility. Results: Two odontoid and six transarticular screws were placed in six patients. Preoperative and postoperative cone-beam CT techniques allowed reconstruction of 3-D images for the evaluation of Type II odontoid fractures and the anatomic suitability of the atlantoaxial complex for transarticular screw fi xation. Postoperative cone-beam CT imaging demonstrated accuracy of screw placement and extent of fracture reduction. Radiation exposure for preoperative and postoperative imaging using cone-beam CT were 0.049 mSv (SD 0.026 mSv) and 0.098 mSv (SD 0.026 mSv), respectively. Conclusions: Three-dimensional fl uoroscopy using cone-beam 3-D CT techniques with the Siemens Multistar Intensifi er provided clinically useful images in the perioperative assessment of atlantoaxial disorders. Potential advantages of cone-beam CT include reduced radiation dose, rapid acquisition times and possible intra-operative applications, including real-time 3-D image guidance.