Assessment of Change of Shoulder Balance in Patients with Adolescent Idiopathic Scoliosis after Correctional Surgery

Abstract

Objective: To identify factors that influence shoulder balance and to determine whether a model can be made to predict shoulder balance after corrective surgery. Methods: This is a retrospective study in which we examined the records of with adolescent idiopathic scoliosis (AIS) patients who underwent single posterior spinal correction and fusion using all pedicle screws with derotation in our institution between January 2008 and June 2010. For the radiographic outcome measurement, we measured the preoperative lumbar curve, the main thoracic curve, and their difference (L_TH_D), and the degree of correction of the lumbar curve, the main thoracic curve, and their difference (c_L_TH_D) to evaluate their influence on postoperative shoulder balance. The preoperative flexibility of the proximal non-fusion curve on the immediate postoperative tilt of the upper endplate of the uppermost vertebra of fusion segments (Up_FuS) was used to evaluate and predict the shoulder balance at follow-up. Results: For patients who had shoulder balance at follow-up, the average balance time was 7.1 months, and in most of them, balance was detected within 12 months. The main thoracic curve has the greatest influence on preoperative shoulder tilt and correction of the main thoracic curve has the greatest influence on the postoperative alteration in shoulder balance. To evaluate the influence on the preoperative shoulder tilt, the lumbar curve must be larger than the main thoracic curve both pre operatively and postoperatively. If the preoperative flexibility of the proximal non-fusion curve on the immediate postoperative Up_FuS includes the horizontal line (With Horizontal group), shoulder balance can be ensured. The postoperative Up_FuS can be evaluated based on the preoperative Up_FuS and the degree of correction of the lumbar and main thoracic curves. Conclusion: Shoulder balance can be ensured in patients in the With Horizontal group after surgery. If the preoperative Up_FuS and the degree of correction of the main thoracic curve and the lumbar curve are considered in the preoperative plan, the desired postoperative Up_FuS can be achieved, ensuring shoulder balance at follow-up.