Increased proximal vertebral rotation is associated with shoulder imbalance after posterior spinal fusion for severe adolescent idiopathic scoliosis

Purpose Residual shoulder imbalance is associated with suboptimal outcomes following the surgical correction of adolescent idiopathic scoliosis (AIS) including poor patient satisfaction. In this retrospective study, we evaluate the radiographic parameters and the relationship between the global and local indices of spinal alignment with shoulder balance pre- and postoperatively utilizing EOS imaging and 3D reconstruction. Methods A retrospective radiographic analysis was performed on patients with AIS, treated with posterior spinal fusion. Postoperative radiographs were obtained immediately following surgery, at 6 months and final follow-up over 2 years postoperatively. 3D Radiographic measurements included in the coronal plane radiographic shoulder height difference (RSHD), proximal thoracic Cobb angle (PT) and main thoracic Cobb (MT), in the sagittal plane T4-T12 kyphosis, T12-L5 lordosis, in the axial plane proximal thoracic (PT AVR) and main thoracic apical vertebral rotation (MT AVR). Results Sixty-six patients were included (63 females) with an average main thoracic curvature of 76 degrees. RSHD averaged 14 mm +/- 14 preoperatively, -15 mm +/- 12 postoperatively, -8.5 mm +/- 11 at 6 months, and -8.3 mm +/- 8.7 at final follow-up, respectively. Statistical analysis revealed a significant correlation between RSHD and proximal thoracic Cobb angle, between RSHD and proximal thoracic apical vertebral rotation (PTAVR) (r > 0.20, p < 0.05). Conclusion The significant correlation presented in this study suggests that PT Cobb angle and PT AVR are involved in postoperative shoulder imbalance.