Introduction: C2 pedicle and pars screws require accurate placement to avoid injury to the nearby neurovascular structures. Freehand, fluoroscopically guided, and CT-based navigation techniques have been described in the literature. The purpose of this study is to compare the safety and accuracy of freehand versus navigated technique for c2 pedicle/pars screw placement.
Methods: Retrospective review of consecutive patients treated with posterior fixation constructs containing C2 pars or pedicle screws placed by spine surgeons from 2010 to 2016 at Barrow Neurological Institute. Basic demographic data, intraoperative and postoperative complications, screw diameter and length, method of screw placement (freehand vs. navigated), and incidence of stroke and all-cause mortality within 30 days of the operation were recorded. Accuracy of screw placement was assessed in those patients with intraoperative/postoperative CT imaging available. Screw accuracy was graded independently by two reviewers according to the following criteria: Grade A (no breach of the cortical surfaces), grade B-E (breach with transverse foramen obstruction of 1-25%, 26-50%, 51-75%, 76-100% respectively), Grade M (medial breach). Screws were then divided into acceptable placement (Grades A,B) and unacceptable placement (Grades C-E, M).
Results: A total of 426 c2 pedicle or pars screws (312 freehand, 114 navigated) were placed in 220 patients. Three vertebral artery injuries (2 freehand, 1 navigated; p=1), 5 deaths (4 freehand, 1 navigated; p=1), and 1 stroke in the navigated group (p=.6) occurred. CT imaging was available for accuracy grading of 182 screws (131 freehand, 51 navigated). No breaches (Grade A) occurred in 86% of the freehand screws and 67% of the navigated screws (p=.023). More screws had acceptable placement in the freehand group (94%) than the navigated group (82%) (p=.023).
Conclusions: Freehand is significantly more accurate than CT- based navigation for c2 pedicle/pars screw placement. There was no difference in complication rate between the two techniques.
Patient Care: Understanding the limitations of CT-based navigation in the cervical spine will lead to more accurate placement of C2 pedicle screws with freehand technique. Although this study did not identify a difference in complication rates between the two techniques, more accurate c2 pedicle screws could lead to fewer vertebral artery injuries on a larger scale.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the technique for freehand and navigated placement of c2 pedicle and pars screws. 2)Understand the limitations of CT-based navigation in the cervical spine 3) Understand the importance of direct visualization of the pedicle during c2 screw placement.
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