Safety and accuracy of freehand versus navigated C2 pars or pedicle screw placement

Background Context C2 pedicle and pars screws require accurate placement to avoid injury to nearby neurovascular structures. Freehand, fluoroscopically guided, and computed tomography (CT)–based navigation techniques have been described in the medical literature. Purpose The present study aims to compare the safety and accuracy of the freehand technique versus stereotactic navigation for the placement of C2 pedicle and pars screws. Study Design/Setting This study was a retrospective review of consecutive patients treated with posterior fixation constructs. Patient Sample A total of 220 consecutive patients were treated with posterior fixation constructs containing C2 pars or pedicle screws placed at our institution. Outcome Measures Computed tomography imaging was used to assess the accuracy of screw placement. Intraoperative complications and incidence of stroke or mortality within 30 days of the operation were analyzed. Methods A retrospective review was conducted of consecutive patients treated with posterior fixation constructs containing C2 pars or pedicle screws placed by spine surgeons between January 1, 2010, and August 31, 2016. Clinical and radiographic data were collected and analyzed. Screw accuracy was graded independently by two reviewers according to the following criteria: grade A (no breach), grades B–E (breach with transverse foramen obstruction of 1%–25%, 26%–50%, 51%–75%, or 76%–100%, respectively), and grade M (medial breach). Screws were divided into acceptable (grades A and B) and unacceptable (grades C–E and M). Results A total of 426 C2 pars or pedicle screws (312 freehand, 114 navigated) were placed in 220 patients (160 freehand, 60 navigated). Complications were similar between the groups: three vertebral artery injuries (two [1%] freehand, one [2%] navigated; p>.99), five deaths (four [3%] freehand, one [2%] navigated; p>.99), and one (2%) stroke in the navigated group (p=.61). Computed tomography imaging was available for accuracy grading of 182 screws (131 freehand, 51 navigated). No breaches (grade A) occurred in 113 of the freehand screws (86%) and in 34 of the navigated screws (67%) (p=.006). More screws had acceptable placement in the freehand group (123 of 131, 94%) than in the navigated group (42 of 51, 82%) (p=.02). Conclusions In patients with postoperative CT imaging (43%), the freehand technique was found to be more accurate than CT-based navigation for C2 pedicle or pars screw placement. Complication rates did not differ between the two techniques in this study.