Determinants of Pre-Operative Shoulder Imbalance in Patients with Adolescent Idiopathic Scoliosis

Background Disfiguring complications of adolescent idiopathic scoliosis (AIS) could significantly affect the patients’ satisfaction. In this regard, shoulder imbalance has recently received much attention in spite of its poorly understood challenge. Objectives While the majority of previous studies have attempted to explore preoperative determinants of postoperative shoulder imbalance, in this study we aimed to investigate the factors correlated with the preoperative shoulder imbalance. Methods A total of 72 AIS patients with no previous history of corrective surgery took part in this study. The study sample comprised 63 females and 9 males with the mean age of 15.72 ± 3.08 years, ranging from 11 to 26 years. Shoulder imbalance parameters including T1 tilt, first rib angle (FRA), and clavicle angle (CA) were assessed and their correlation with radiographic characteristics of the curves and patients’ demographic data including age and sex was evaluated. Results T1 tilt was more severe in males (mean -8.2°) than females (mean -2.8°) (P = 0.04). Moreover, a significant correlation was found between age and FRA (P = 0.04). A significant correlation was also observed between main thoracic (MT) curve size and all the three parameters of shoulder imbalance (P < 0.001). The reverse correlation of T5 - T12 kyphosis angle with FRA was also significant (P = 0.04). Conclusions According to our results, in AIS, pre-operative radiographic shoulder imbalance could be affected by some curve parameters including MT and kyphosis size and demographic characteristics of patients including age and gender.