Risk factors for the development of persistent shoulder imbalance after surgical correction of idiopathic scoliosis

Objective . To assess risk factors for the imbalance of the shoulder girdle and to identify reproducible X-ray criteria for persistent shoulder imbalance after correction of idiopathic scoliosis. Material  and Methods . A total of 94 patients with idiopathic scoliosis were  included in the  retrospective study. All patients underwent primary posterior correction of the  deformity using pedicle screw instrumentation. Radiography of the  spine throughout its length was performed before surgery, in the  early  postoperative and in the  long-term (at least 12 months after surgery) periods. The  shoulder imbalance was considered clinically significant with radiographic shoulder height difference more than 2 cm. Results . A significant decrease in the  magnitude of all curves after surgery and in the  long-term period was noted. The  magnitude of the proximal curve decreased from  25.38° ± 15.89° to 14.51° ± 8.17° (p < 0.0001) and  to 14.29° ± 8.25° (p = 0.24); the  main  thoracic curve from  59.33° ± 20.76° to 20.096° ± 9.89° (p < 0.0001) and  to 20.87° ± 9.48° (p = 0.19); and  thoracolumbar curve from  47,20° ± 15,99° to 15.69° ± 8.66° (p < 0.0001) and to 16.98° ± 7.6° (p = 0.01), respectively. The  shoulder imbalance was recorded in 27 patients (28.72 %) after surgery and in 13 (13.83 %) – in the long-term period. In these patients, various Lenke types of deformity were presented. A correlation of the distal adding-on phenomenon with self-correction of the shoulder balance is revealed (r = 0.56; p < 0.005). Persistent shoulder imbalance correlated with presence of a structural proximal thoracic curve (p = 0.041642), residual proximal curve magnitude after surgery (r = 0.22; p = 0.03), and presence of a symptom of double rib hump on radiographs after surgery (r = 0.75; p ≤ 0.005). Conclusion . The  most characteristic pattern of persistent shoulder imbalance is the  presence of asymmetry in the  proximal and main  regions of the  chest. This sign can be detected by intraoperative lateral radiography of the  spine, which will allow the  surgeon to take measures to eliminate this phenomenon and reduce the  probability of persistent shoulder imbalance development.