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

Abstract

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.