Differential Effects of Lower Extremity Length Discrepancy on Functional and Structural Scoliosis: Coronal and Sagittal Plane Analysis.

Background: Lower extremity length discrepancy (LELD) is closely associated with spinal imbalances such as pelvic tilt and functional scoliosis. While existing studies have focused on LELD-induced coronal compensations, its impact on sagittal spinal balance remains poorly understood. The aim of the current study was to investigate the differential effects of LELD on coronal and sagittal spinal balance in adolescents with functional versus structural scoliosis.

Methods: A retrospective analysis of 211 patients was conducted. Participants were stratified into functional (n=165) or structural scoliosis (n=46) groups based on pelvic and lumbar correction with limb elevation. Radiographic parameters included coronal and sagittal measures. Statistical analyses compared groups and assessed correlations.

Results: Structural scoliosis exhibited significantly worse coronal imbalance (higher sacral obliquity, lumbar Cobb angle, and coronal balance distance; P<0.001) and greater sagittal vertical axis (SVA; P<0.05). LELD correlated with coronal parameters in functional scoliosis (P<0.05) but not structural cases. Sagittal balance parameters (pelvic tilt, sacral slope) showed no LELD association, though SVA correlated with coronal imbalance only in functional scoliosis (P<0.05). Roussouly's sagittal classification did not differ between groups.

Conclusions: LELD primarily drives compensatory coronal changes, with minimal sagittal impact. Structural scoliosis demonstrates worse coronal imbalance and elevated SVA, suggesting distinct compensatory mechanisms. Functional cases may benefit from LELD correction, while structural scoliosis requires sagittal evaluation during surgical planning. These findings highlight the importance of prioritizing coronal alignment in LELD-related scoliosis management.

Level of evidence: Level III.