gms | German Medical Science

Objective: Recent studies and meta-analysis have evidenced the superior accuracy of navigated spinal instrumentation compared to non-navigated techniques with further improvement through additional implementation of intraoperative computed tomography (iCT). However, current solutions for navigated spine surgery remain hampered by restrictions in surgical workflow as well as a limited versatility and applicability. Against this background, we report the first experience of navigated spinal instrumentation with the mobile AIRO^® iCT scanner.

Method: From May 2014 until August 2014, AIRO^® iCT was used for navigated posterior spinal instrumentation of 170 screws in 23 patients (11 female, 12 male; median age: 68, range 31 to 83 years). The surgical indications were degenerative disease (10/23; 43%), tumors (8/23; 35%) and trauma (5/23; 22%). The indications for AIRO^® were anatomically complex deformities, revision cases, regions of the spine that are typically difficult to visualize with conventional iso-C 3D C-arm navigated fluoroscopy, or cases that required multilevel (>3 segments) instrumentation. Following navigated screw insertion, screw positions were confirmed intraoperatively by a second iCT scan. CT data on screw placement accuracy was retrospectively reviewed and analyzed by an independent observer. Further, a systematic description of the authors' approach, setup in the OR and workflow integration of the AIRO^® was developed.

Results: AIRO^®-based spinal navigation was easy to implement and successfully accomplished in all patients, adding around 18-34 minutes to the net surgery time. The large gantry diameter permitted iCT in obese patients and in patients who were positioned in a Mayfield clamp. The high image quality and resolution permitted radiographic visualization of all levels of the spine and ist surrounding structures without difficulties. There was no need for a repeat iCT scan due to faulty co-registration or a wrong-level scan. Analysis of screw placement accuracy revealed 9 (5.3%) screws with minor pedicle breaches (<2mm). A total of 7 screws (4.1%) were misplaced >2mm, resulting in an accuracy rate of 95.9%.

Conclusions: The AIRO^® system is an easy-to-use and versatile iCT for navigated spinal instrumentation and provides high pedicle screw accuracy rates. Although the authors' experience suggests that the learning curve associated with AIRO^®-based spinal navigation is steep, a systematic user-based approach to the technology is required.