• Changwei Yang, Yanming Li, Mingyuan Yang, Yunfei Zhao, Xiaodong Zhu, Ming Li, and Gabriel Liu.
• *Department of Orthopedics, Changhai Hospital of the Second Military Medical University, Shanghai, China †The Second Military Medical University, the National University of Singapore Joint Research Center for Spinal Deformity ‡Department of Orthopaedic Surgery Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
• Spine. 2016 Apr 1; 41 (8): 698-704.

Study DesignA retrospective study.ObjectiveThe aim of this study was to detect risk factors for Adding-on after posterior correction surgery in patients with Lenke 1 or 2 AIS, and to explore whether Adding-on Index could be used to predict Adding-on effectively.Summary Of Background DataAdding-on phenomenon is a common complication in Lenke 1 or 2 AIS patients after correction surgery. However, whether it can be predicted after surgery remains unknown.MethodsLenke 1 or 2 AIS patients receiving correction surgery in our center from January 2009 to July 2013 were analyzed. Antero-posterior and lateral films were evaluated before surgery, at 2 weeks' and 2 years' follow-up. Patients were divided into 2 groups according to whether Adding-on occurred at the 2 years' follow-up. Risk factors of Adding-on were analyzed, and Adding-on Index was proposed and verified.ResultsSixteen patients (16.3%) suffered from distal Adding-on at 2-year follow-up. Several parameters were found to be significantly different between 2 groups, including Risser's sign, postoperative Cobb angle of main thoracic, postoperative Cobb angle of main thoracic curve at 2-year follow-up, preoperative and postoperative Cobb angle of lumbar curve, postoperative Cobb angle of lumbar curve at 2-year follow-up, LIV-EV, LIV-SV, LIV-CSVL, LAV-CSVL, LAV-LIV, DnfS, and postoperative TJK. No significant differences in SRS-22 scores were observed. Binary logistic regression analysis showed that DnfS and postoperative residual Cobb angle of lumbar curve were primary factors for occurrence of Adding-on. According to the regression equation, Adding-on Index was defined as 4 × DnfS-postoperative lumbar curves Cobb angle. On the basis of ROC curve, if Adding-on Index was more than 12, the occurrence rate of Adding-on was 88%. On the contrary, the rate of no Adding-on phenomenon was 80%.ConclusionDnfS and posterior Cobb angle of lumbar curve were 2 important factors for Adding-on in Lenke 1, 2 AIS patients. Adding-on Index can be used to predict the occurrence of Adding-on effectively.Level Of Evidence4.

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