Analysis of factors that affect shoulder balance after correction surgery in scoliosis: a global analysis of all the curvature types

To identify factors that can affect postoperative shoulder balance in AIS. 89 adolescent idiopathic scoliosis patients with six types of curvatures who underwent surgery were included in this study. Whole spine antero-posterior and lateral radiographs were obtained pre- and postoperatively. In radiograms, shape and changes in curvatures were analyzed. In addition, four shoulder parameters and coronal balance were analyzed in an effort to identify factors significantly related to postoperative shoulder balance. In general, all the four shoulder parameters (CHD, CA, CRID, RSH) were slightly increased at final follow up (t test, P < 0.05), although there was a decrease in Lenke type II and IV curvatures. However, pre- and postoperative shoulder parameters were not significantly different between each curvature types (ANOVA, P > 0.05). Moreover, no significant differences of pre- and postoperative shoulder level between different level of proximal fusion groups (ANOVA, P > 0.05) existed. In the analysis of coronal curvature changes, no difference was observed in every individual coronal curvatures between improved shoulder balance and aggravated groups (P > 0.05). However, the middle to distal curve change ratio was significantly lower in patients with aggravated shoulder balance (P < 0.05). In addition, patients with smaller preoperative shoulder imbalance showed the higher chance of aggravation after surgery with similar postoperative changes (P < 0.05). Significant relations were found between correction rate of middle, and distal curvature, and postoperative shoulder balance. In addition, preoperative shoulder level difference can be a determinant of postoperative shoulder balance.