What factors predict cervical sagittal alignment restoration after correction of thoracic adolescent idiopathic scoliosis with severe thoracic hypokyphosis? A multicenter retrospective study of 57 patients

Purpose: to evaluate changes in cervical sagittal alignment after correction of AIS with severe thoracic hypokyphosis (< 10°); to assess radiographical parameters predicting postoperative cervical sagittal alignment through multivariate regression analysis. Methods: A multicenter retrospective study included AIS patients with severe thoracic hypokyphosis. Treatment involved posterior spinal fusion with pedicle screws, Ponte osteotomies, differential rod contouring and DVR. Radiographic analysis was conducted preoperatively and at a minimum 2-year follow-up. Results: Among 57 patients, a significant improvement in T5-T12 thoracic kyphosis was noted at the last follow-up. Cervical Lordosis (CL) also significantly increased, with a remaining mismatch between ideal and actual postoperative CL. Correlation analyses revealed associations between thoracic kyphosis and postoperative CL. In patients with preoperative neutral or kyphotic CL, additional factors, such as TK apex-SVA, C5-T2° Change, and TK apex-scoliosis apex distance, correlated with CL changes. Conclusion: Posterior correction of hypokyphotic AIS demonstrated significant CL improvement, yet a mismatch between ideal and achieved alignment persisted. The degree of thoracic and cervicothoracic alignment restoration correlated with spontaneous CL improvement. Overall, the study highlights the complexities of sagittal alignment in AIS.