Navigated odontoid screw placement using the O-arm: technical note and case series.

OBJECTIVE As odontoid process fractures become increasingly common in the aging population, a technical understanding of treatment approaches is critical. 3D image guidance can improve the safety of posterior cervical hardware placement, but few studies have explored its utility in anterior approaches. The authors present in a stepwise fashion the technique of odontoid screw placement using the Medtronic O-arm navigation system and describe their initial institutional experience with this surgical approach. METHODS The authors retrospectively reviewed all cases of anterior odontoid screw fixation for Type II fractures at an academic medical center between 2006 and 2015. Patients were identified from a prospectively collected institutional database of patients who had suffered spine trauma. A standardized protocol for navigated odontoid screw placement was generated from the collective experience at the authors' institution. Secondarily, the authors compared collected variables, including presenting symptoms, injury mechanism, surgical complications, blood loss, operative time, radiographically demonstrated nonunion rate, and clinical outcome at most recent follow-up, between navigated and nonnavigated cases. RESULTS Ten patients (three female; mean age 61) underwent odontoid screw placement. Most patients presented with neck pain without a neurological deficit after a fall. O-arm navigation was used in 8 patients. An acute neck hematoma and screw retraction, each requiring surgery, occurred in 2 patients in whom navigation was used. Partial vocal cord paralysis occurred after surgery in one patient in whom no navigation was used. There was no difference in blood loss or operative time with or without navigation. One patient from each group had radiographic nonunion. No patient reported a worsening of symptoms at follow-up (mean duration 9 months). CONCLUSIONS The authors provide a detailed step-by-step guide to the navigated placement of an odontoid screw. Their surgical experience suggests that O-arm-assisted odontoid screw fixation is a viable approach. Future studies will be needed to rigorously compare the accuracy and efficiency of navigated versus nonnavigated odontoid screw placement.