Predictors of change in postoperative pulmonary function in adolescent idiopathic scoliosis - A prospective study of 254 patients

Study Design. A multicenter study of prospectively collected pulmonary function testing and radiographic measures in patients surgically treated for adolescent idiopathic scoliosis (AIS). Objective. The objectives of this study were 1) to identify the factors that determine pulmonary function more than 2 years after surgery for AIS; and 2) to determine what factors, if any, can predict an increase or decrease in the percent predicted 2-year pulmonary function. Summary of Background Data. Thoracic spinal deformity can lead to significant pulmonary impairment. Studies have shown that patients with AIS experienced a significantly greater improvement in pulmonary function at 2 years after surgery when treated with a posterior approach compared to an anterior approach. Methods. Pulmonary function testing (PFT) and radiographic examination of 254 patients with AIS were completed prospectively. Demographic data, associations between radiographic measurements of spinal deformity, and the results of spirometry underwent correlation analysis and subsequent step-wise multiple regression analysis. Results. The variables found to be significant predictors of 2-year pulmonary function (FVC, FEV1, TLC) include: preop PFT (R-2 = 0.20-0.39), having an open thoracotomy (as opposed to thoracoscopic or posterior) (R-2 = 0.07-0.09), surgical time (R-2 = 0.03-0.07), and thoracoplasty (R2 = 0.02-0.04). These models explain 40 to 51% of the variance in 2-year PFT. For patients undergoing open thoracotomy with a thoracoplasty, approximately 54% had a 15% decrease, or more, in percent predicted PFT. This compared with 11% and 15%, respectively of patients who either had posterior or thoracoscopic procedures with no thoracoplasty that had a 15% decrease or more in percent predicted PFT. Conclusion. Aside from preoperative PFT values, open anterior approaches predict the largest percent of variance in 2-year PFT. Additionally, a clinically significant reduction in the predicted 2-year pulmonary function is more likely when performing a thoracoplasty. The magnitude of the effects for both these variables, however, is modest. This may facilitate the decision-making process as regards to operative intervention.