Surgery for Scheuermann Kyphosis Normalizes Lumbar Lordosis but Not Cervical Alignment When Compared With Asymptomatic Individuals: A Pelvic-Matched Comparative Study

Retrospective, case-control study. To examine and compare preoperative and postoperative sagittal alignment between Scheuermann Kyphosis (SK) patients and an asymptomatic, normative population. SK is a rigid spinal deformity seen in adolescents and young adults, characterized by hyperkyphosis and associated compensatory changes in spinal alignment. Although compensatory mechanisms in adjacent spinal segments are known to maintain global sagittal balance, limited data exist on the extent of baseline and postoperative alignment differences in SK patients. An SK cohort, composed of patients from the Harms Study Group (HSG) database and our local institution, was compared with young asymptomatic individuals from the prospectively enrolled Multi-Ethnic Alignment Normative Study (MEANS). An optimal propensity score match (PSM) was conducted to control for preoperative pelvic incidence (PI) and tilt (PT) between cohorts. Wilcoxon rank sum and McNemar tests were utilized. Of the 65 SK and 254 MEANS individuals, PSM generated 65 matched pairs; PI and PT did not differ between cohorts. All preoperative SK parameters, including cervical sagittal angle (CSA, C2-C7), T1 slope (T1S), and T1-T12 thoracic kyphosis (TK1), as well as lumbar lordosis (LL, L1-S1), proximal LL (pLL, L1-L4), and distal LL (dLL, L4-S1), were greater in SK than MEANS ( P <0.05). At 2 years postoperative, CSA, T1S, and TK1 remained significantly higher in the postoperative SK cohort. In contrast, all lumbar parameters, including LL, pLL, and dLL, normalized and did not differ from the MEANS cohort. Preoperative cervical and lumbar SK parameters were significantly different from asymptomatic volunteers, reflecting compensation for extreme thoracic kyphosis. Postoperatively, SK TK remained significantly higher. Compensatory CSA and T1S remained significantly higher as well, whereas postoperative lumbar parameters normalized and did not differ from asymptomatic patients, suggesting that partial TK improvement can lead to normalization of lumbar hyperlordosis but a remnant high T1 slope continues to require compensatory cervical hyperlordosis.