Predictive value of C0-C2 and C1-C2 angles for postoperative lower cervical alignment following posterior atlantoaxial fixation and fusion: a retrospective single-center study.

OBJECTIVE

To evaluate the relationship between occipitocervical (C0-C2) and atlantoaxial (C1-C2) angles and postoperative lower cervical curvature (C2-C7) following posterior atlantoaxial fixation and fusion, and to determine optimal fixation angles and predictive reliability.

METHODS

130 patients treated between 2016 and 2022 were retrospectively reviewed. The cohort included 32 patients with chronic odontoid fractures, 40 with os odontoideum combined with atlantoaxial dislocation, 12 with rheumatoid arthritis-related atlantoaxial dislocation, and 46 with other forms of atlantoaxial dislocation. Preoperative and final follow-up lateral cervical radiographs measured C0-C2, C1-C2, and C2-C7 angles. Clinical outcomes were assessed using VAS, JOA, and NDI. Correlations between radiographic parameters were analyzed using Pearson's correlation.

RESULTS

Mean follow-up 24 months (12-36). Postoperatively, C0-C2 and C1-C2 angles increased (both P < 0.001), while C2-C7 decreased (P < 0.001). Patients with C0-C2 < 20° had better lower cervical lordosis and clinical outcomes than those ≥ 20° (P < 0.05); similar for C1-C2 < 25° vs ≥ 25° (P < 0.001). C2-C7 angle showed no correlation with C0-C2 < 20° (P = 0.397, r = 0.112) or C1-C2 < 25° (P = 0.870, r = 0.022), but significant negative correlations with C0-C2 ≥ 20° (P < 0.001, r = - 0.822) and C1-C2 ≥ 25° (P = 0.004, r = - 0.337).

CONCLUSION

Postoperative C0-C2 ≥ 20° or C1-C2 ≥ 25° is associated with significant loss of lower cervical lordosis after posterior atlantoaxial fusion. Maintaining C0-C2 within 10°-20° and C1-C2 within 10°-25° may better preserves physiological alignment and outcomes. C0-C2 angle appears to be a more reliable intraoperative reference for sagittal balance.