 A total of 284 DLS patients were recruited into this two-stage study, among which 69 patients were treated by posterior-only correction and the remaining 215 patients received conservative treatment. Using pre-operative long-cassette X-ray films, all patients were classified based on coronal balance distance CBD defined as the horizontal distance between C7 plumb line and central sacral vertical line: Type A, CBD 3cm; Type B, CBD 3cm and C7PL shifts to the concave side of curve; Type C, CBD 3cm and C7PL shifts to the convex side of curve. The prevalence of pre-operative coronal imbalance was calculated for stage I study. Post-operative CBD in patients who received surgery was measured to evaluate clinical outcomes for stage II study. 