Residual L4 Tilt and Five-Year Self-Image After L3 Fusion for Adolescent-Onset Idiopathic Scoliosis

Abstract Purpose. To characterize L4/L5 alignment after L3 fusion and test whether residual L4 tilt is associated with 5-year self-image. Methods. This two-center cohort included adolescent-onset idiopathic scoliosis with Lenke 5/6 lumbar major curves treated by posterior fusion to L3. Absolute L4/L5 tilt, L3/4 disc wedge, thoracolumbar/lumbar (TL/L) Cobb, clavicle angle, and C7-central sacral vertical line offset were assessed at 1 week, 2 years, and 5 years. Robust models evaluated correction transfer, change correlates, and Scoliosis Research Society-22r Self-image. Results. Of 117 patients, 81 had complete L4/L5 trajectories. Per 5° greater lowest-instrumented-vertebra correction, initial L4 and L5 leveling increased by 1.99° (95% CI, 1.02–2.95; P<.001) and 0.95° (95% CI, 0.14–1.75; P=.022), respectively. L4 remained stable from 1 week to 5 years, whereas L5 leveled by 1.17° (95% CI, 0.52–1.82; P<.001). L3/4 disc wedge was stable (− 0.06°; P=.825), while TL/L Cobb increased by 2.91° (P<.001). Five-year L4 tilt correlated with worse Self-image (ρ=−0.405; q=.008); each 5° greater tilt was associated with 0.22-point lower fully adjusted Self-image (95% CI, − 0.42 to − 0.02; P=.032). Age was unrelated to distal change. Conclusion. L3 leveling was associated with immediate L4/L5 leveling. Later L5 leveling despite stable L3/4 disc geometry and TL/L correction loss supports segment-specific alignment redistribution, not generalized distal remodeling. Residual L4 tilt remained associated with long-term Self-image.