Purpose: Waistline asymmetry is a major cosmetic concern for patients with adolescent idiopathic scoliosis (AIS) and may persist even after surgery. However, differences in radiographic factors and postoperative impact according to waistline asymmetry pattern have not been fully elucidated. The aim of this study is to examine radiographic correlates, related factors for postoperative waistline asymmetry, and its impact on clinical outcomes according to waistline asymmetry type in patients with AIS.

Methods: This retrospective study included patients with AIS who underwent posterior spinal fusion with a minimum 2-year follow-up. Radiographic parameters and clinical outcome were evaluated preoperatively and 2 years postoperatively. Waistline asymmetry was assessed using digital photographs, and waistline depth (WLD) was measured bilaterally. Patients were classified into Type R or Type L according to the side of deeper waistline. Severe waistline asymmetry (SWA) was defined as a ≥2-fold difference in WLD between sides. Statistical analyses were performed to identify determinants of postoperative waistline asymmetry.

Results: A total of 236 patients were included. The WLD ratio in Type R correlated primarily with lumbar parameters, whereas in Type L it correlated with both thoracic and lumbar parameters. Postoperative SWA was observed in 26 patients (11%). In Type R, postoperative SWA was associated with lower preoperative lumbar flexibility of the curves and greater residual lumbar curve postoperatively, and was significantly associated with worse postoperative self-image scores. In Type L, postoperative SWA was associated with greater residual lumbar curve, but showed no significant association with self-image.

Conclusions: Waistline asymmetry in AIS has pattern-specific determinants and clinical implications. Residual lumbar curves could affect the postoperative asymmetry and negatively affect self-image.