An Observational Retrospective and Prospective Study to Evaluate the Treatment Outcomes of Atlantoaxial Osteoarthritis.

Background Atlantoaxial osteoarthritis (AAOA) is a degenerative disorder of the C1-C2 articulation that causes occipitocervical pain, restricted head rotation, and functional limitation. Treatment ranges from nonoperative care to image-guided intra-articular injection and surgical stabilization in selected patients with persistent symptoms or structural compromise. This study evaluated the clinical and radiographic outcomes of patients with AAOA managed through a defined institutional treatment protocol. Methods This single-center observational cohort study included 232 patients with AAOA treated at a tertiary spine center. The cohort included retrospectively identified patients treated from January 2020 to March 2021 and prospectively followed patients treated from April 2021 to December 2025. All patients underwent initial nonoperative treatment according to an institutional protocol. Patients with persistent symptoms despite conservative care were offered image-guided intra-articular C1-C2 injection, and patients with refractory pain or structural compromise underwent posterior C1-C2 fusion. For analysis, patients were categorized according to definitive treatment into a nonoperative cohort and a surgical cohort. The nonoperative cohort included patients who improved with conservative treatment alone or with injection-based treatment and did not undergo surgery. Clinical outcomes were assessed using the Visual Analog Scale (VAS) and Neck Disability Index (NDI). Radiographic variables included laterality, joint type, osteoarthritis grade, periarticular ossicles, joint destruction, subluxation, instability, and fusion status in operated patients. Results A total of 232 patients were included, with 200 patients in the nonoperative cohort and 32 patients in the surgical cohort. All patients received initial conservative treatment, and 32 patients progressed to C1-C2 fusion. The surgical cohort was significantly younger than the nonoperative cohort, with a mean age of 50.0 ± 17.5 years compared with 65.7 ± 9.9 years, respectively. Bilateral involvement and mixed joint disease were the most common radiographic patterns in both cohorts. The surgical cohort showed greater radiographic severity, with higher rates of Grades 3 and 4 disease, joint destruction, subluxation, and instability. In the nonoperative cohort, the mean VAS score improved from 6.23 ± 1.68 at baseline to 1.61 ± 1.04 at final follow-up, and the mean NDI improved from 0.32 ± 0.11 to 0.06 ± 0.05. In the surgical cohort, the mean VAS score improved from 7.41 ± 1.19 to 1.97 ± 1.45, and the mean NDI improved from 0.60 ± 0.14 to 0.11 ± 0.10. Radiographic fusion was documented in 30 of 32 operated patients. Conclusions AAOA is a clinically important cause of occipitocervical pain and disability. In this single-center cohort managed through a defined institutional treatment protocol, most patients remained in the nonoperative pathway and demonstrated clinical improvement, while posterior C1-C2 fusion was associated with meaningful improvement in selected patients with refractory symptoms or structural compromise. Further prospective studies using standardized imaging, treatment protocols, and follow-up schedules are needed to refine management pathways for this condition.