Morphological and Clinical Feasibility of C3 Pedicle Screw Instrumentation in Patients with Congenital C2-3 Fusion

Abstract

Introduction Incidence of C2 pedicle narrowing is high in patients with congenital C2-3 fusion (C2-3CF). An alternative would be C3 pedicle screw (PS) instrumentation, which will not sacrifice an additional motion segment; however, its feasibility has not yet been reported in the literature. Materials and Methods Twenty-eight patients with C2-3CF were enrolled to this study, including 22 atlantoaxial dislocations and 6 odontoid fractures. They underwent the procedures of occiput or C1 to caudal vertebrae fixation and fusion. The pedicle trajectories of C2 and C3 were evaluated using three-dimensional computed tomography (CT). The width, height, length, and medial and superior angle of the trajectories and the posterior projection of C3 pedicle were evaluated. Trajectory was considered narrow when the diameter was less than 4.0 mm. The clinical results were followed. There were no funding sources or potential conflicts of interest to disclose. Results The incidence of C2 and C3 pedicle narrowing were 53.6 and 21.4%, respectively. The mean dimension of C3 pedicle was 4.9 mm in width, 4.9 mm in height, and 28.5 mm in length; the mean inclination angle was 8 degrees superior and 35 degrees medial. Using the midline of the fused C2-3 lamina as the superior border of C3 articular mass, posterior projection of the C3 pedicle lied 3 mm inferior to the superior border and 3.2 mm medial to the lateral border of the articular mass. It was located roughly at the upper lateral quadrant of the articular mass. During the operation, the caudal spinal fixation patterns were 16 bilateral C3, 7 bilateral C2, 3 bilateral C4, and 2 contralateral C2/3. Postoperative CT revealed 3 C2 and 5 C3 pedicle trajectory breaches. No vertebral artery or spinal cord injury occurred. The mean follow-up time was 4 years and no implant failure developed. Conclusion The morphology of C3 pedicle is suitable for PS instrumentation in a large proportion of patients with C2-3CF. C3PS instrumentation is a feasible technique for selective patients with C2-3CF and may serve as another reliable choice for this condition. Disclosure of Interest None declared