Long-Term Influence of C<sub>1</sub>-C<sub>2</sub> Pedicle Screw Fixation on Occipitoatlantal Angle and Subaxial Cervical Spine in the Pediatric Population

<b><i>Objective:</i></b> The goal of this study was to evaluate the impact of C₁-C₂ pedicle screw fixation on the occipitoatlantal angle and subaxial cervical spine for a pediatric population, and the clinical efficacy and adjacent-segment degeneration after C₁-C₂ pedicle screw fixation with a minimum of 2 years of follow-up. <b><i>Methods:</i></b> Twenty-two pediatric patients with atlantoaxial dislocation who were enrolled in this study underwent atlantoaxial pedicle screw fixation. The correlation between C₀-C₁, C₂-C₇, and C₁-C₂ pre- and postoperative sagittal angles was assessed using plain radiographs, and adjacent-segment degeneration (ASD) and JOA scores (Japanese Orthopaedic Association scores) were evaluated after atlantoaxial pedicle screw fixation. <b><i>Results:</i></b> The C₁-C₂ angle increased from 16.1 ± 13.37 to 28.1 ± 5.1° (<i>p</i> < 0.01). The pre- and postoperative C₁-C₂ angles were negatively correlated with the pre- and postoperative C₀-C₁ and C₂-C₇ angles, respectively. In accordance with the optimal atlantoaxial fusion angle (25-30°) obtained from the literature, postoperative JOA scores were greater in the groups with angles of more than 30° and less than 25°, although the difference in ASD was not statistically significant. Postoperative JOA scores were not relevant to the postoperative C₁-C₂ angle; however, there was a positive correlation between JOA improvement rate and the change of the C₁-C₂ angle postoperatively. <b><i>Conclusion:</i></b> Atlantoaxial pedicle screw fixation can be used easily to reduce atlantoaxial dislocation in the pediatric population; however, outside the range of the optimal atlantoaxial fusion angle it can change the occipitoatlantal angle and subaxial alignment, which induces ASD and influences the clinical efficacy. It is necessary to achieve an optimal atlantoaxial angle when using atlantoaxial pedicle screw fixation.