Changes of Upper Thoracic Curve and Shoulder Balance in Thoracic Adolescent Idiopathic Scoliosis Treated by Anterior Selective Thoracic Fusion Using VATS

Abstract

A retrospective radiographic analysis. To evaluate changes of upper thoracic curve and shoulder balance in thoracic adolescent idiopathic scoliosis patients treated by anterior selective thoracic fusion using video-assisted thoracoscopic surgery and to identify adequacy of earlier criteria of double thoracic (DT) curve for anterior correction. Although anterior and posterior scoliosis correction show many differences in correction mechanisms, fusion levels, loss of correction etc., the criteria of DT curve was applied without differences. There are no reports about these differences. Forty patients were followed for a minimum of 3 years (range, 3-8 y). The magnitude and flexibility of upper thoracic, lower thoracic, and the superior portion of the lower thoracic curve were measured using full length standing and side-bending radiographs before surgery, at 1 week postoperatively, and at last follow-up. The correction rate and loss of correction of these curves were calculated and preoperative and postoperative radiographic shoulder heights (RSHs) were measured. RSH was defined as balanced (shoulder height difference <10 mm), mildly imbalanced (10-20 mm), or moderately imbalanced (>20 mm). T1 tilt and coronal balance were also evaluated. Patients were divided into groups based on these factors and postoperative RSH was compared. Flexibility of the upper thoracic curve was 46% and magnitude of the upper thoracic curve was corrected spontaneously from 28.6±7.8 degrees to 17.9±7.0 degrees with a 37.4% correction rate that did not change during follow-up. On average, preoperative left shoulder was 6.3±10.5 mm lower than right shoulder and this changed to 10.4±11.8 mm and 6.0±8.2 mm higher than right shoulder at 1 week postoperatively and at last follow-up, respectively. The group with an upper thoracic curve of ≥30 degrees or a superior portion of the lower thoracic curve of ≥30 degrees preoperatively had a higher left shoulder postoperatively (P=0.016, 0.040). Of the 12 patients with a symmetric or higher left shoulder (≥0 mm) preoperatively, 9 patients had a balanced shoulder (-10-10 mm) and 3 patients showed mild shoulder imbalance (<20 mm) at last follow-up. Among patients who have DT curve, patients with mild left shoulder elevation (<20 mm) can be treated by anterior correction unless the magnitude of upper thoracic curve or superior portion of lower thoracic curve are ≥30 degrees. For anterior correction, criteria of DT curve might be applied less strictly.