Prospective pulmonary function evaluation following open thoracotomy for anterior spinal fusion in adolescent idiopathic scoliosis

Study Design. Prospective study. Objectives. To prospectively evaluate sequential pulmonary function tests (PFTs) at a minimum 2-year follow-up after an open anterior spinal fusion (ASF) with instrumentation for thoracic AIS. Summary of Background Data. Anterior spinal fusion with instrumentation is currently undergoing evaluation as an alternative to posterior spinal fusion (PSF) for thoracic adolescent idiopathic scoliosis (AIS). However, the effect of an open thoracotomy on pulmonary function in these patients is unknown. Methods. Fifty-one patients with thoracic AIS with an average age of 15 + 0 (range 11 + 2 to 20 + 5) had PFTs consisting of volume (FVC), flow (FEV-1), and total lung capacity (TLC). Parameters were obtained preoperatively, and at 3 months, 1 year, and a minimum 2-year follow-up. All patients had a single or double open thoracotomy with the diaphragm kept intact. Fusion levels ranged from T4 (most proximal) to L1 (most distal). The average preoperative thoracic coronal Cobb measurement was 53 degrees (range 38 degrees to 80 degrees), and the average postoperative coronal measurement was 24 degrees (range 7 degrees to 49 degrees). The average preoperative thoracic sagitta I kyphosis (T5-T12) averaged 22 degrees (range 10 degrees to 58 degrees), and the average postoperative sagittal kyphosis measured 29 degrees (range 7 degrees to 67 degrees). Results. There was a significant decline (P less than or equal to 0.05) in PFT absolute values (L) of 19%-FVC, 15%-FEV-1, and 11%-TLC at 3 months postoperatively with subsequent improvement and no statistical difference between preoperative and 2-year postoperative values. When evaluating percent predicted values, there was a statistical decline (P less than or equal to 0.05) at 3 months postoperatively averaging 19% FVC, 14% FEV-1. and 12% TLC. These va rues returned to within 94% to 96% of baseline by the 2-year follow-up visit, but were still statistically less than the preoperative values (P less than or equal to 0.05). Conclusions. Pulmonary function following thoracotomy with ASF with instrumentation demonstrated a significant decline of 3-month postoperative PFT values, but returned to preoperative baseline absolute values (L) by the 2-year follow-up visit. The percent predicted values returned to within 95% of baseline 2 years postoperatively. Scoliosis surgeons should be aware of these findings when deciding upon the approach (anterior versus posterior) utilized for thoracic AIS.