LAUSR

OBJECTIVE This study aimed to report the technical advancement to improve the accuracy of cervical pedicle screw (CPS) placement using O-arm-based 3D navigation (O-arm). METHODS Sixty-four patients who underwent CPS using O-arm in the spine level of C2 to C7 between June 2013 and February 2020 were involved. In the first phase, a reference frame was placed onto the spinous process of the cranial vertebrae and used it at a maximum of 3 vertebral levels. The navigation guide sleeve was used to drill a screw hole. In the second phase, a reference frame that can hold 3 vertebrae was introduced. In the third phase, a drill guide sleeve to minimize bending of the drill tip was developed. In the fourth phase, navigated surgical drill (Stealth-Midas®, Medtronic) was introduced. Screw accuracy was assessed using Neo's classification: grade (G) 0, no perforation; G1, perforation <2 mm; G2, perforation 2-4 mm; G3, perforation >4 mm. RESULTS Mean age at surgery was 67 (19-88) years. A total of 317 CPS was inserted. In total, 83 screws were inserted in the first phase, 60 in the second phase, 87 in the third phase, and 87 in the fourth phase. The total proportion of malpositioning was 3.8% (12/317 screws) and all were G1; 6.0% (5/83 screws) in the first phase, 8.3% (5/60 screws) in the second phase, 1.2% (1/87 screws) in the third phase, and 1.2%(1/87 screws) in the fourth phase (p<0.05). CONCLUSION O-arm use improved CPS placement accuracy with the advancement of techniques and instruments.