Scoliosis Surgery in Patients With Adolescent Idiopathic Scoliosis Does Not Alter Lung Volume
Study Design. Retrospective study of surgically treated patients with adolescent idiopathic scoliosis. Objective. To determine the change in lung volume after the surgical correction of scoliosis using a volumetric reconstruction of lung volume from computed tomographic (CT) scans. Summary of Background Data. Previously published studies have shown that pulmonary function tests improve after scoliosis correction; however, these results are not consistent. CT-based volumetric studies in patients with scoliosis have previously shown differences in lung volume and lung volume ratio when compared with a normal population. To date, no study exists that analyzes changes in these parameters after scoliosis surgery. Methods. A total of 29 patients with adolescent idiopathic scoliosis who had pre-and postoperative CT scans on file were included in this study. Three-dimensional lung volume reconstruction was performed (TeraRecon software, TeraRecon, Inc., Foster City, CA). Appropriate masking methods were used to isolate the lung tissue. Total lung volumes, left and right lung volumes, and left/right lung volume ratio were obtained from the pre-and postoperative CT scans. Hemithoracic symmetry, pre-and postoperative Cobb angle, and kyphosis were also calculated. Results. Neither total lung volume nor left/right lung volume ratio changed significantly postoperatively. Surgery did not significantly change total lung volume (P = 0.87), right lung volume (P = 0.69), left lung volume (P = 0.70), or the ratio between right and left lung volumes (P = 0.87). Hemithoracic asymmetry was significantly improved (P < 0.001). Median preoperative major Cobb angle was 53.2 degrees and median preoperative kyphosis was 32.8 degrees. Postoperatively, the median major Cobb angle was 15.0 degrees, resulting in a 70% Cobb correction, and mean postoperative kyphosis was 31.1 degrees. Conclusion. Corrective scoliosis surgery does not alter total lung volume or the ratio of right-to-left lung volume. Deformity correction leads to an improvement in the symmetry of the thoracic architecture and costovertebral joint mechanics, as evidenced by the improved hemithoracic asymmetry. Thus, the change in pulmonary function tests, which has been previously documented, may be a dynamic rather than a static phenomenon.