General Session: Cervical Degenerative

Presented by: D. Yin - View Audio/Video Presentation (Members Only)

Author(s):

D. Yin(1), G. Oh(1), S. Neckrysh(1)

(1) University of Illinois at Chicago, Neurosurgery, Chicago, IL, United States

Abstract

Objective: Cervical 2 (C2) pedicle screw fixation is often used during posterior cervical fusion. C2 pedicle diameter and feasibility of screw placement are always considered during cervical instrumentation. We believe that C2 pedicle diameter and its relationship with the vertebral artery is often miscalculated and underestimated based on the preoperative CT scan images, as the axial CT cuts are performed in the plane parallel to the disc space and tangential to the pedicle. The goal of this study was to determine C2 pedicle diameter on axial images and images parallel to the C2 pedicle using intraoperative O-arm reconstruction.

Methods: In this study, there were 20 patients, including 15 males and 5 females. Age ranged from 44 to 71 yr with mean age of 60.1 yr. All patients underwent C2 pedicle screw placement between January 2015 and August 2016. Images of C2 pedicles were obtained using O-arm with try-planar reconstruction. The axial images were not manipulated but were assessed as provided and C2 pedicle diameters were measured. After that the axial plane was positoned parallel to the C2 using plane rotation function of the O-arm and new measurements were performed. The axial and oblique widths of C2 pedicle on the screen were measured on the axial and oblique images using a regular ruler, and therefore called “screen width of C2 pedicle”. O-arm software at this point does not provide the measurement tool.

Results: The axial width of C2 pedicles ranged from 6 to 15 mm with mean of 11.10 ± 2.07 mm on the right side, and from 7 to 14 mm with mean of 10.83 ± 1.63 mm on the left side. The oblique width of C2 pedicles ranged from 10 to 19 mm with mean of 14.68 ± 1.96 mm on the right side, and from 12 to 19 mm with mean of 15.30 ± 2.0 mm on the left side. These measurements yielded significantly higher oblique screen width of C2 pedicles than axial screen width.

Conclusions: The axial and oblique images of O-arm provide valuable assessment of C2 pedicle width. The oblique screen width of C2 pedicles is better to be used for predicting the feasibility of C2 pedicle screw placement than its axial screen width. Since this assessment may help in surgical decision-making at no added cost or radiation exposure, we suggest obtaining screen width of C2 pedicle whenever considering C2 pedicle screw inserting.