Evaluation of postoperative change in lung volume in adolescent idiopathic scoliosis Measured by computed tomography

Background: Change in total lung volume after surgical correction in adolescent idiopathic scoliosis (AIS), measured by computed tomography (CT), has not been studied previously. The primary objective of this study was to measure the change in lung volume between pre and postoperative AIS using low-dose CT and secondary objective was to investigate its relationship to postoperative pulmonary complications. Materials and Methods: 55 AIS patients underwent surgery for correction and fusion using a posterior only approach and pedicle screws. Pre and postoperative lung volumes were measured using a 3-dimensional (3D) whole spine CT (low dose protocol: Tube current, 60 mA; tube voltage 120 kV). Postoperative low dose CT was undertaken at 4 weeks after operation to evaluate the acute changes of postoperative lung volumes and pulmonary complications. The software that was used recognizes the "air density shade" of the lung and the volume of every section of the lung. The software then automatically calculates total lung volume by summation of all section volumes. The relationships between postoperative pulmonary complications and changes in lung volume on low dose CT as well as preoperative forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV ₁ ) were calculated using logistic regression analysis. Results: There was a decrease of 12% ± 23.2% in total lung volume postoperatively on 3D low dose CT (P < 0.001). Thirteen patients had increased lung volume while 42 had decreased lung volume postoperatively. Pulmonary complications were treated without severe sequale. Lung volume increased by 19.65% ± 19.84% in 13 patients and decreased by 21.85% ± 13.32% in 42 patients (P = 0.647). Lung volume was increased in patients whose preoperative lung volume, FEV ₁ and FVC were lower than in patients whose values were higher (r =-0.273,-0.291 and-0.348; P = 0.044, 0.045 and 0.015, respectively). Postoperative lung volume was also increased when intraoperative fluid administration was larger and operative time was longer (r = 0.354, 0.417 and P = 0.008, 0.002, respectively). There was a statistically significant negative correlation in the change of lung volume in female patients when compared with male patients (r =-0.294, P = 0.03). Conclusion: Patients with AIS who have preoperative reduced lung volumes or lung functions can achieve further increased lung volume after surgical correction. Pulmonary complications during perioperative period were mostly treated with proper management without severe sequale. Therefore, although surgery for AIS is considered to be a high risk procedure, we can recommend to correct spine deformity in patients with severe AIS in order to improve lung function and long term prognosis.