Morphological Changes of the Cervical Spine in Adolescent Idiopathic Scoliosis and Correlation Analysis

Background To investigate the morphological changes of the cervical spine in patients with adolescent idiopathic scoliosis (AIS) and to analyze their correlation with other coronal and sagittal plane parameters of the spine. Methods A retrospective collection of full-length spinal radiographs was conducted for 199 patients with AIS who were treated at and 77 adolescents without scoliosis (control group) the Third Affiliated Hospital of Zhejiang Chinese Medical University between January 2019 and February 2025. Patients with AIS were classified into two groups based on the physiological curvature of their cervical spine: a non-kyphotic group and a cervical kyphosis (CK) group. The following radiographic parameters were measured: coronal main curve Cobb angle, C2-C7 angle, T1 slope (T1S), T1 coronal tilt, apical vertebra translation (AVT), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), cervical sagittal vertical axis (cSVA), and sagittal vertical axis (SVA). Intergroup comparisons and correlation analyses of these parameters were subsequently performed. Results The incidence of CK among patients with AIS was 60.3%, which was significantly higher than the 46.8% observed in the control group. Compared to patients with mild scoliosis, those with moderate scoliosis exhibited a significant reduction in the C2–C7 angle (P < 0.05), while the CSVA showed a significant increase (P < 0.05). No significant differences were observed in the C2-C7 angle, cSVA, or CK rates among the lumbar, thoracolumbar, and thoracic main curve groups (P > 0.05). In the thoracic main curve group, patients with a left convex curve had a significantly lower rate of CK compared to those with a right convex curve (P = 0.039). Correlation analysis revealed that CK was positively correlated with the Cobb angle (r = 0.282, P < 0.001), PT (r = 0.184, P = 0.009), and PI (r = 0.154, P = 0.029), while it showed a negative correlation with TK (r = -0.459, P < 0.001) and T1S (r = -0.505, P < 0.001). Conclusion Cervical kyphosis is a prevalent morphological change observed in patients with AIS, and it may be associated with the severity of scoliosis. Furthermore, the occurrence of cervical kyphosis is correlated with spinopelvic parameters including the Cobb angle, PT, PI, TK, and T1S. In the context of conservative treatment for AIS, restoring the physiological curvature of the cervical spine may be beneficial for correcting scoliosis, serving as a potential adjunctive therapeutic strategy.