Postoperative shoulder imbalance in adolescent idiopathic scoliosis: risk factors and predictive index

Postoperative shoulder imbalance (PSI) is a common complication of adolescent idiopathic scoliosis (AIS). However, results regarding risk factors for PSI are contradictory. This study was performed to explore the risk factors associated with PSI in AIS and determine whether PSI could be predicted.

Medical records of AIS patients receiving correction surgery from January 2012 to January 2015 were reviewed. Anteroposterior films were evaluated before and after the surgery and at the 2-year follow-up. Patients were divided into two groups according to whether PSI was observed at 2-year follow-up. Risk factors for PSI were analyzed, and a PSI index was proposed and verified.

A total of 114 AIS patients (PSI/non-PSI: 60/54) were included. The univariate analysis showed that PTC (proximal thoracic curve), preoperative PTC-to-MTC (main thoracic curve) ratio, preoperative bending Cobb angle of PTC, preoperative bending Cobb angle of the lumbar curve, postoperative PTC, postoperative AVT (apical vertebral translation) of PTC, AVT of PTC at follow-up, and adding-on angle were significantly different between two groups. Adjusted logistic regression analysis showed that postoperative AVT of PTC and adding-on angle were the primary contributors to PSI in patients with AIS. The PSI index was defined as 1.2 × postoperative AVT of PTC + 1.1 × adding-on angle. According to the receiver operating characteristic curve, the cutoff point for the PSI index in predicting the development of PSI was 15. The positive and negative predictive values were 80% and 87%, respectively.

To prevent PSI, we recommend sufficient correction of AVT of PTC and prevention of adding-on. These slides can be retrieved under Electronic Supplementary Material.