Sagittal morphology of the cervical spine in adolescent idiopathic scoliosis: a retrospective case-control study.

Background: To investigate the relationship between sagittal alignment and coronal deformity in patients with adolescent idiopathic scoliosis (AIS) through analysis of the spinal imaging data.

Methods: Four hundred and fifty-four AIS patients who underwent anteroposterior and lateral radiography of the while spine were enrolled, and the spinal parameters of Cobb angle, cervical lordosis, C1-C2 angle, T1 slope, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt (PT), pelvic incidence (PI), cervical sagittal vertical axis (SVA), and spinal SVA were analyzed.

Results: The patients were divided into two groups according to the size of the Cobb angle: group A (Cobb angle ≤45°, n=414) and group B (Cobb angle >45°, n=40). In group A, the Cobb angle was in a medium negative correlation with the cervical lordosis angle (r=-0.637, P<0.001), a weak positive correlation (|r|<0.3, P<0.05) with C1-C2 angle, T1 slope and thoracic kyphosis. In group B, the Cobb angle was in a mild positive correlation (P<0.05) with PT (r=0.398) and PI (r=0.360). The cervical lordosis angle was significantly (P<0.05) different between male and female patients in both groups. In Group A, the cervical lordosis angle was in a significantly (P<0.01) positive correlation with the T1 slope (r=0.586), thoracic kyphosis (r=0.490), and sagittal vertical axis (r=0.135), and a significantly (P<0.01) negative correlation with cervical sagittal vertical axis (r=-0.128) and C1-C2 angle (r=-0.155). In group B, the cervical lordosis angle was in a significantly (P<0.05) positive correlation with T1 slope (r=0.661), thoracic kyphosis (r=0.608), lumbar lordosis (r=0.425), sacral slope (r=0.434), and sagittal vertical axis (r=0.335).

Conclusions: In AIS patients with the Cobb angle ≤45º, a significant negative correlation exists between the cervical lordosis and the Cobb angle. The sagittal morphology of the cervical spine in AIS patients is affected by the spinal coronal deformity, which plays an important role in the treatment of AIS.