Subaxial sagittal shifts postatlantoaxial fusion - Radiological assessment and clinical analysis

The maintenance of spinal anatomy and posture is a dynamic process governed by vertebral bodies, intervertebral discs, facet joints, ligaments, and paraspinal musculature. This flexibility allows the spine to compensate for deformities and maintain sagittal balance. Surgical correction of atlantoaxial dislocation involves rigid fixation of the atlas and axis (C1-C2) and disruption of posterior extensor muscles, which may induce compensatory changes in the subaxial cervical spine.

This study aims to analyze changes in the sagittal alignment of the subaxial cervical spine in patients with craniovertebral junction (CVJ) anomalies following posterior atlantoaxial fusion, and to examine the progression of these changes in relation to neurological outcomes.

Thirty patients with CVJ anomalies who underwent posterior C1-C2 fixation were analyzed. Clinical parameters, including age, gender, etiology, tone, power, and modified Japanese Orthopaedic Association Score, were assessed. Radiological evaluation focused on the C2-C7 Cobb angle measured on lateral cervical spine radiographs preoperatively, immediately postoperatively, and 6 months follow up.

Atlantoaxial fixation resulted in a significant reduction in subaxial cervical lordosis. The mean preoperative C2-C7 angle was 16.96°° ± 4.07°, which decreased to 12.22°° ± 4.8°° immediate postoperatively. At 6 months, the angle further reduced to 11.03° ± 4.3°°. Despite radiological changes, no clinical deterioration was observed.

Posterior atlantoaxial fixation offers robust clinical and radiological outcomes in CVJ anomalies. While a reduction in subaxial lordosis is observed postoperatively, it does not correlate with adverse neurological outcomes in the short term.