Abstract: Objective: A well-known method for treating atlantoaxial instability is posterior screw fixation using a C1 lateral mass screw and a C2 pedicle screw. Yet, due to the intricate anatomical anatomy of this area, screw malposition might happen. This study used a preoperative computed tomography (CT)-based navigation system with a single-level vertebral registration approach to assess the accuracy and risk factors of cortical breach following the insertion of the C1 lateral mass and/or C2 pedicle screw.
Methods: Patients who had preoperative CT-based navigation for the implantation of a C2 pedicle screw and/or a C1 lateral mass at the university hospital between January 2013 and March 2020 were included in this retrospective cohort analysis. Inside the pedicle (grade 0), out of the pedicle 2 mm (grade I), from 2 to 4 mm (grade II), and > 4 mm were the classifications for screw deviation (grade III). Using the use of multivariate analysis, the risk of cortical breach was assessed.
Results: 42 patients had 78 C1 lateral masses and 71 C2 pedicle screws implanted. 133 grade 0 screws (89.3%) were placed accurately, followed by 14 grade I screws (9.4%) and two grade II screws (1.3%). No vertebral artery damage or neurological impairment was connected to this method, and no screws needed to be repositioned. The multivariate analysis also revealed that the cortical rupture had a diameter of less than 5 mm.
Conclusions: A preoperative CT-based navigation system with a single-level registration approach might be used to insert C1 lateral mass securely and successfully and C2 pedicle screws. The C1 lateral mass and C2 pedicle diameters are risk factors for cortical rupture.
