Evaluation of Correction of Radiologic Parameters (Angulation and Displacement) and Accuracy of C2 Pedicle Screw Placement in Unstable Hangman's Fracture with Intraoperative Computed Tomography-Based Navigation

BACKGROUND: Opinions vary regarding optimal treatment of unstable hangman's fractures, including rigid orthosis and internal fixation. The anatomy of upper cervical spine is complex. The advent of intraoperative 3-dimensional navigation systems facilitates safe and accurate instrumentation. OBJECTIVE: To evaluate radiologic parameters of fracture morphology in unstable hangman's fracture in preoperative and postoperative period and accuracy of inserting axis pedicle screws by using intraoperative computed tomography-based navigation. METHODS: Fifteen patients with unstable hangman's fractures with age ranging from 17 years to 81 years were operated using computed tomography-based navigation from September 2011 to march 2016. Patient's age, sex, mechanism of injury, associated injuries, and neurologic status were noted. Clinical outcome, accuracy of screw insertion, preoperative and postoperative displacement, and angulation of C2 over C3 and bony fusion were assessed. RESULTS: Overall, 76 screws were inserted including 30 screws in C2 pedicle with 2 (2/60; 6.7%) malplaced screws in C2 pedicle. Mean follow-up period was 34 +/- 18 months (range 7-80 months). Mean hospital stay was 12.8 +/- 2.4 days. Mean preoperative and postoperative displacements were 4.09 mm +/- 1.78 mm and 1.82 mm +/- 1.14 mm respectively with a mean reduction of 2.27 mm +/- 1.49 mm. Mean preoperative angulation was 7.23 degrees +/- 11.96 degrees and postoperative angulation was 2.32 degrees +/- 4.77 degrees with a mean reduction of 5.11 degrees +/- 11.96 degrees. Bony fusion was achieved and rotation was preserved at C1-C2 joint in all cases. CONCLUSIONS: Intraoperative O-arm-based navigation is a safe, accurate, and effective tool for screw placement in patients with unstable hangman fracture and achieves good anatomical reduction.