Abstract
PURPOSE: To explore the relationship between lumbosacral curve vertebral body tilt correction and postoperative coronal balance in adult degenerative scoliosis to determine the ideal target values for the tilt correction. METHODS: We conducted a retrospective analysis of 144 patients who underwent surgery between January 2017 and December 2023. Patients were classified based on the preoperative Obeid classification and fixation segment length into Concave Long Segment (Concave-L, n = 41), Concave Short Segment (Concave-S, n = 33), Convex Long Segment (Convex-L, n = 39), and Convex Short Segment (Convex-S, n = 31). Changes in coronal and sagittal radiographic parameters and the correlation between the correction percentage of the most tilted vertebra (L4 or L5) and postoperative coronal balance distance (CBD) were assessed. RESULTS: Significant postoperative improvements in CBD, maximum coronal tilt, and Cobb angle were observed in the Concave-L, Convex-L, and Convex-S groups. The Concave-S group exhibited significant changes only in Cobb angle and maximum coronal tilt, but not CBD. A significant negative correlation existed between postoperative CBD and the correction ratio of maximum coronal tilt in the convex malalignment (r=-0.629, P < 0.001), with the regression equation: Postoperative CBD = 32.99 - (28.82 × Correction Ratio of Coronal Tilt). A correction ratio exceeding 45% at L4 or L5 tilt predicted a postoperative CBD within 20 mm. CONCLUSION: Both short and long segment fusions effectively correct convex coronal malalignment, but concave malalignment requires long segment fusion for adequate correction. Optimal coronal balance in convex malalignment is achieved when the maximum tilt correction ratio exceeds 45%.