The Impact of Adult Scoliosis Surgical Correction on Thoracolumbar Rotational Kyphosis

Objective: Adult scoliosis (AS) is often associated with rotational thoracolumbar (TL) kyphosis. The impact of surgical correction on lumbar sagittal distribution, ideal sagittal plane matching, and mechanical complications is still underexplored. Methods: In this retrospective study, prospectively collected data were analyzed from a multicenter adult deformity database. Inclusion criteria were surgical patients with AS and TL/L curves > 30°, T10-L2 sagittal kyphosis (TLK) > 20°, and at least a 2-year follow-up. We analyzed preoperative and postoperative variables and studied the consequences of TL sagittal change on ideal type mismatch and on mechanical complications using univariate and multivariate logistic regression analyses, and compared patients with high pelvic incidence (PI > 50°) versus those with low PI (PI < 50°). Results: A total of 171 patients were included. The TLK segment flattened by a mean of 20° after surgery. The residual TLK kyphosis matched that expected by PI. The TL sagittal change was not directly associated with complications or ideal shape mismatch. Mechanical complications were associated only with older age and pelvic instrumentation. Patients with low and high PI were found to have similar Cobb angle correction, TLK correction, and rate of mechanical complications. However, it was more challenging to restore an ideal sagittal profile in patients with high PI and in patients fused to the pelvis. Conclusions: Surgical correction of adult TL scoliosis flattens the TL segment by about 20°, automatically adjusting to the ideal parameters dictated by patients’ PI. The TL segment change lengthens the upper lumbar arc by one segment, shifting the inflection point cranially. However, this change has no direct impact on mechanical complications or final sagittal shape matching.