gms | German Medical Science

Objective: Analogue to cranial surgery, spinal navigation is becoming a common applied tool in spinal instrumentation surgery. Current literature demonstrates a rapidly increasing usage of navigational systems thus leading to high accuracy rates of pedicle screw placements. Widespread appliances include intraoperative mobile or stationary CTs and 2D or 3D fluoroscopy. We evaluated the accuracy of over 500 navigated pedicle screw placements with a more unique technology thus being an intraoperatively obtained robotic 3D C-arm Dyna-CT.

Methods: After fixation of a reference array on the spinous process, an intraoperative Dyna-CT was conducted followed by an automated registration process. All pedicle screws were then placed with the image-guided neuronavigation. Interbody cages were placed under fluoroscopic view with the same robotic 3D C-arm system. Postoperative CT scans were performed to evaluate pedicle screw positioning and compared to intraoperative Dyna-CTs. The grade of pedicle screw accuracy was classified into four groups: screws fully contained into the pedicle, perforated screws up to 2 mm displacement (Grade A), 2–4 mm (Grade B), and greater than 4 mm displacement (Grade C).

Results: A total of 557 navigated pedicle screws were placed with this robotic 3D flat panel C-arm CT system within a time period of 14 Months at our institute. Intraoperative Dyna-CT evaluation revealed that 551 of the 557 screws were fully contained into the pedicles leading to an accuracy of 98.9%. 6 screws being 1.1% showed a Grade C displacement and were corrected intraoperatively. Surgery times were increased in mean by merely 12min. No significant discrepancies were distinguishable between the intraoperative Dyna-CT and postoperative standard scans.

Conclusion: Neuronavigational placement of pedicle screws with this unique robotic 3D C-arm Dyna-CT shows equivalent accuracies to other high resolution intraoperative spinal navigation systems whilst simultaneously offering the benefits of conventional fluoroscopy e.g. for interbody cage placement or pedicle screw augmentation. Furthermore, the intraoperative Dyna-CT is revealed to be accurate for evaluation of screw positioning so that postoperative scans are no longer needed.