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 (A SF) with instrumentation for thoracic AIS. Summary of Background Data. Anterior spinal fusion with instrumentation is currently undergoing evaluation as an alternative to posterior spinal fusio n (PSF) for thoracic adolescent idiopathic scoliosis (AIS). However, the ef fect of an open thoracotomy on pulmonary function in these patients is unkn own. 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, a nd 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 le vels ranged from T4 (most proximal) to L1 (most distal). The average preope rative thoracic coronal Cobb measurement was 53 degrees (range 38 degrees t o 80 degrees), and the average postoperative coronal measurement was 24 deg rees (range 7 degrees to 49 degrees). The average preoperative thoracic sag itta I kyphosis (T5-T12) averaged 22 degrees (range 10 degrees to 58 degree s), and the average postoperative sagittal kyphosis measured 29 degrees (ra nge 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 post operatively with subsequent improvement and no statistical difference betwe en preoperative and 2-year postoperative values. When evaluating percent pr edicted 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 follo w-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 instrum entation demonstrated a significant decline of 3-month postoperative PFT va lues, but returned to preoperative baseline absolute values (L) by the 2-ye ar follow-up visit. The percent predicted values returned to within 95% of baseline 2 years postoperatively. Scoliosis surgeons should be aware of the se findings when deciding upon the approach (anterior versus posterior) uti lized for thoracic AIS.