Study design: A retrospective clinical and radiographic study.
Objective: The aim of this study was to analyze the radiographic change in cervical sagittal alignment (CSA) and identify the possible factors influencing the postoperative CSA in selective posterior thoracolumbar/lumbar (TL/L) curve correction.
Summary of background data: The correlation between the CSA and thoracic sagittal alignment (TSA) is a well-recognized phenomenon in patients with thoracic idiopathic scoliosis. However, little has been published about the influence of TL/L curve instrumentation on CSA.
Methods: Thirty patients with Lenke type 5C adolescent idiopathic scoliosis (AIS) received the selective posterior TL/L curves fusion by pedicle screws. Preoperative and postoperative radiographic and clinical parameters were analyzed. C2-C7 lordosis less than 0 was considered a lordotic cervical spine (LCS), whereas more than 0 was considered a kyphotic cervical spine (KCS).
Results: Preoperatively, 43% of patients showed a KCS, whereas the remaining 57% showed a LCS. C2-C7 lordosis was correlated with T1-slope, thoracic kyphosis (TK), and global-TK (Gl-TK) (P < 0.05). The patients in the KCS group showed a smaller T1-slope, TK, and Gl-TK than those in the LCS group. Logistic regression analysis revealed that the T1-slope [odds ratio (OR) = 0.86, P = 0.008] and Gl-TK (OR = 0.90, P = 0.019) were risk factors for developing KCS. In the LCS group, 5 of 12 patients with LCS exhibited KCS after surgery. The T1-slope and Gl-TK in the changed group were considerably smaller than those in the maintained group (P = 0.004 and 0.035, respectively). In the KCS group, 6 of 13 patients with KCS unrecovered to LCS after the operation. The T1-slope in the unrecovered group was smaller than that in the recovered group (P = 0.045).
Conclusion: C2-C7 lordosis was strongly correlated with the T1-slope. C2-C7 lordosis of Lenke 5C AIS was related to the global TSA rather than TK and proximal TK. As time progresses, spontaneous adjustment of CSA is limited because of the inherent rigidity of the cervical spine.
Level of evidence: 4.