Incidence of and Factors Associated with Spontaneous Correction of Postoperative Shoulder Imbalance in Adolescent Idiopathic Scoliosis Patients: A Retrospective Cohort Study

Abstract

Background: As far as we know, no study has investigated spontaneous postoperative shoulder imbalance (PSI) correction in adolescent idiopathic scoliosis (AIS) patients. The objective is to assess the incidence of and associated factors for spontaneous PSI correction in AIS patients. Methods: The study evaluated 144 postoperative AIS patients with PSI aged 10–20 years between 2010 and 2018. An analysis included demographic data and radiographic measurements (Risser grading, Lenke type, upper instrumented vertebra [UIV], and lowest instrumented vertebra [LIV]). Preoperative, postoperative, and follow-up radiographs were evaluated for shoulder parameters: radiologic shoulder height (RSH); T1 tilt angle; clavicle angle (CA); proximal thoracic curve (PTC), main thoracic curve (MTC), and lumbar curve (LC) Cobb measurements; and apical vertebral translation (AVT) of the PTC, MTC, and LC. Results: Spontaneous PSI correction was observed in 99 (68.75%) patients. The spontaneous correction and nonspontaneous correction groups differed significantly in terms of Lenke-type preoperative LC (23° vs 26°; P = 0.091), postoperative LC (11° vs 8°; P = 0.013), LC at follow-up (13.5° vs 9°; P = 0.028), postoperative AVT of LC (− 0.8° vs − 0.4°; P = 0.033), AVT of LC at follow-up (− 0.7° vs − 0.1°; P = 0.091), PTC at follow-up (16° vs 20°; P = 0.019), and AVT of PTC at follow-up (0° vs -0.3°; P = 0.029). Multivariate analysis identified postoperative T1 tilt and postoperative LC as significantly associated with PSI correction. Conclusions: The incidence of spontaneous PSI correction is high. Postoperative T1 tilt and postoperative LC are significantly associated with spontaneous PSI correction.