Spinal Navigation: Intraoperative CT (AIRO) versus Cone-Beam CT (O-Arm). Preliminary Results of a Single Center Experience

Aim: Spinal navigation with intraoperative cone-beam CT (O-arm) has been used in our center since 2008, on ∼1,200 cases. We have previously shown that screw placement accuracy has increased. In October 2014, we added the CT (AIRO) in the aim to further increase image quality and versatility in intraoperative use. We report our preliminary experience with this new modality and compare it with the previous O-arm-guided technique. Methods: We retrospectively analyzed a series of 25 cases operated with screw positioning at cervical, thoracic, lumbar, and sacroiliac levels. Indications, number of operated levels, screws, and their precision were retrospectively analyzed. Further repositioning, duration of surgery, and radiation exposure were also analyzed. Data were then compared with previous data obtained with O-arm-guided navigation for same cases. Results: Our series includes 14 females and 11 men. Mean age was 67 years (range 42–86). Indications for surgery were degenerative (n = 21), traumatic, or neoplastic disease (n = 4). Two cases were operated with percutaneous technique. Mean number of operated levels was 3.6. Mean duration of surgery was 335 minutes (vs. 276 minutes in our previous O-arm series). In total, 188 pedicular screws were positioned. A total of 179 screws (95%) were correctly positioned in the pedicle (vs. 92% in our previous O-arm series), while 9 screws (5%) were incorrect (vs. 8% in our previous O-arm series). Of these, five were Grade 1 (3%), two were Grade 2 (1%), and two were Grade 3 (1%). All incorrect screws were at cervical or thoracic level. Six screws (3%) were repositioned during surgery, after intraoperative CT. Reason for reposition the screws were lateral positioning (three screws), medial (one screw), or too deep (one screw). Mean equivalent dose was 16.56 mSv. Conclusions: Results of this study compare favorably with our previous experience with O-arm. For two reasons, 100% was not obtained. First, in one case a second intraoperative CT after screw repositioning was not performed as to lessen radiation exposure. Second, in other cases surgeon decided to leave the screw with an incorrect position, because the screw was judged as stable and the risk of repositioning was high. Positioning of the screws with navigation was, however, highly accurate, as shown by the low number of repositioned screws during.