ObjectiveTo investigate the changes and relationship of cervical spine sagittal alignment and other spinal-pelvic sagittal parameters in adolescent idiopathic scoliosis. MethodsBetween July 2011 and July 2014, 35 patients with idiopathic scoliosis who met the inclusion criteria underwent posterior pedicle screw instrumentation and fusion. There were 12 males and 23 females with a mean age of 16.2 years (range, 13-20 years), including 16 cases of Lenke type 1, 7 cases of Lenke type 2, 4 cases of Lenke type 3, 3 cases of Lenke type 4, 4 cases of Lenke type 5, and 1 case of Lenke type 6. The average follow-up time was 10.9 months (range, 5-36 months). The pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), cervical lordosis (CL), T1 slope, C2 slope, C7 sagittal vertical axis (C7 SVA), C2-7 plumbline (cSVA) were measured on pre-and post-operative standing lateral X-ray film. Based on preoperative CL, the patients were divided into kyphosis group (CL>0°) and lordosis group (CL < 0°); after operation, the patients were divided into restored lordosis (group A), decreased kyphosis (group B), and increased lordosis (group C) after operation. All data about sagittal profile changes were analyzed. The relations between CL and other spinal-pelvic parameters in the kyphosis and lordosis groups before operation were determined via Spearman correlation coefficient. ResultsStatistically significant changes were observed in PT, PI, SS, and LL between at pre-and post-operation (P < 0.05), but no significant difference was found in the other parameters (P>0.05). There were 17 patients in lordosis group and 18 in kyphosis group before operation. Intra-group comparisons showed significant changes in PT, PI, SS, C2 slope, and C7 SVA in lordosis group, and in PT, PI, SS, LL, CL, TK, T1 slope, and C2 slope in kyphosis group (P < 0.05). Subgroup comparisons showed significant changes in CL, TK, C2 slope, C7 SVA, and T1 slope before operation (P < 0.05) and T1 slope at last follow-up between 2 groups (P < 0.05). In kyphosis group, 7 cases (group A) had restored lordosis, 7 cases (group B) had decreased kyphosis, and 4 cases had increased lordosis. In lordosis group, 9 cases (group C) had increased lordosis, 3 cases had decreased lordosis, and 5 cases had kyphotic cervical alignment after operation. Significant difference was found in LL, CL, T1 slope, C2 slope, and C7 SVA of group A, in TK and CL of group B, and in CL and cSVA of group C between pre-and post-operation (P < 0.05). There were significant differences in pre-and post-operative LL between groups A and B (P < 0.05). In lordosis group, there was a strong correlation between CL and C2 slope (P < 0.05) at pre-operation. CL had strong correlation with C2 slope and T1 slope (P < 0.05) at pre-operation in kyphosis group, and CL had moderate correlation with cSVA (P < 0.05). ConclusionCervical sagittal alignment plays an important role in the balance of the spine and pelvis. The change of cervical sagittal alignment has a certain correlation with the change of thoracic kyphosis. Attention to properly maintaining or restoring cervical sagittal lordosis alignment should be considered in preoperative evaluation of adolescent indiopathic scoliosis.