Shoulder Balance After Vertebral Body Tethering Versus Posterior Spinal Fusion in Adolescent Idiopathic Scoliosis: The Role of Correction Pattern

Objectives To compare postoperative shoulder balance between vertebral body tethering (VBT) and posterior spinal fusion (PSF) in adolescent idiopathic scoliosis over two years. Methods A multicenter retrospective comparative study was performed including AIS patients who underwent either VBT or PSF with a minimum of two years of follow-up. Radiographic parameters of shoulder balance, including clavicle angle, T1 tilt, and shoulder height difference, were measured preoperatively and at two years. Changes over time and between-group differences were analyzed using unadjusted tests and multivariable regression adjusting for 11 baseline differences. Results The final cohort consisted of 99 patients: 49 VBT and 50 PSF. Groups differed only in Risser score, with VBT patients less skeletally mature. The VBT cohort had more thoracolumbar curves, while the PSF cohort had more thoracic curves. At baseline, PSF patients demonstrated greater T1 tilt (6.49+-10.36? vs -1.01+-5.18?, p<0.001), whereas VBT patients had greater clavicle angle (1.72+-2.8? vs -0.45+-3.2?, p=0.001). Unadjusted differences were attenuated after adjustment for baseline characteristics. In multivariable analyses, absolute postoperative T1 tilt and clavicle angle were no longer significantly different between groups. However, differences in change over time remained significant, with VBT demonstrating less change in T1 tilt, greater improvement in clavicle angle, and greater increase in shoulder height difference. Conclusions Differences in shoulder balance between VBT and PSF appear to be driven by differences in correction pattern rather than absolute postoperative alignment. These findings suggest that both baseline deformity and surgical correction strategy contribute to postoperative shoulder balance.