Sagittal Profile Response of Cervical Spine After Posterior Correction in Thoracic and Lumbar Adolescent Idiopathic Scoliosis: Correlation with Thoracic Kyphosis?

OBJECTIVE: To analyze postoperative changes in cervical alignment in patients with adolescent idiopathic scoliosis (AIS) with different curve patterns. METHODS: Radiographic data were retrospectively reviewed in 43 patients with AIS with right thoracic major curve versus 39 with major lumbar curve with a minimum of 2 years' follow-up. Radiographic parameters analyzed in this study included cervical sagittal parameters (cervical lordosis [CL], T1 slope, T1 slope minus C2-C7 lordosis, T1-spine, T1 pelvic angle, and C2-C7 sagittal vertical axis) and spinopelvic sagittal parameters obtained from radiographs. Paired t tests were used for comparison with 0.05 as a statistically significant threshold. RESULTS: At baseline, larger CL (5.69 degrees vs. - 5.12 degrees, P = 0.002) and smaller T1 slope minus C2-C7 lordosis (9.26 degrees vs. 17.09 degrees , P = 0.001) was noted in patients with lumbar-curve adolescent idiopathic scoliosis (l-AIS), whereas preoperative thoracic kyphosis (TK) was not different between the 2 groups. When the immediate postoperative sagittal profiles were compared between the 2 groups, larger TK (23.72 degrees vs. 18.86 degrees, P = 0.009) and more obvious CL (7.26 degrees vs. -2.60 degrees, P = 0.001) were noticed in the L-AIS group. During the follow-up, larger TK and CL were still maintained in the L-AIS group. In addition, a significant correlation was found between the improvement of CL and TK restoration in patients with L-AIS (r = - 0.473, P = 0.002). CONCLUSIONS: Correlations between the improvement of CL and TK highlight the importance of restoration of patients with normal TK or AIS. Reciprocal changes in cervical alignment may happen if the TK was also simultaneously restored in patients with AIS. For patients with different curve patterns, the cervical sagittal parameters tend to be similar during follow-up.