The change of cervical sagittal alignment after surgery for adolescent idiopathic scoliosis

The postoperative change in cervical sagittal alignment has an impact on health-related quality of life in adolescent idiopathic scoliosis (AIS) patients who have undergone deformity correction. However, the effect of deformity correction on sagittal cervical profile is still controversial in the literatures. The objective of this study was to investigate the postoperative change in the cervical sagittal alignment of patients with AIS.

A total of 46 AIS patients treated by posterior instrumentation and fusion with pedicle screw constructs were included in the study. Radiographs were collected preoperatively, immediate postoperatively and at the final follow-up. The C2-C7 Cobb angle and C2-C7 sagittal vertical axis (cSVA) were used to assess the cervical sagittal alignment. Spinopelvic alignment parameters, such as thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), and sagittal vertical axis (SVA), were also measured. The correlations between the cervical sagittal parameters and spinopelvic parameters were analyzed.

The incidence of cervical kyphosis was 67.4% preoperatively but increased to 87% postoperatively and 69.5% at the final follow-up. The C2-C7 Cobb angle significantly increased from pre-operation (-1.5° ± 15°) to post-operation (-5.4° ± 7.3°; P < 0.05) and spontaneously decreased to -2.9° ± 10.5° at the final follow up. The cSVA was 18.1 ± 13 mm preoperatively, 17 ± 12.3 mm after surgery and 18.5 ± 9.5 mm at the last follow-up, but the change was not statistically significant (P > 0.05). TK decreased significantly from pre-operation (17.7° ± 14.4°) to post-operation (14.2° ± 7.6°) and spontaneously improved to 16.9° ± 8.2° at the final follow-up. TK showed a significant correlation with the C2-C7 Cobb angle, but not with cSVA, in the preoperative (r = 0.709, P < 0.01), postoperative (r = 0.472, P < 0.01), and last follow-up measurements(r = 0.505, P < 0.01). Compared with patients with preoperative thoracic hypokyphosis or hyperkyphosis, patients with a normal thoracic spine had more significant postoperative changes in the C2-C7 Cobb angle and TK.

Cervical sagittal alignment after deformity correction is altered in AIS patients. An increase in cervical kyphosis after surgery is correlated with a loss of thoracic kyphosis. The change in the cervical sagittal profile may be a compensatory mechanism in response to an abnormal thoracic sagittal profile.