Should Postoperative Pulmonary Function Be a Criterion That Affects Upper Instrumented Vertebra Selection in Adolescent Idiopathic Scoliosis Surgery?

Abstract

A multicenter, prospective evaluation of pulmonary function testing (PFT) and radiographical measures in patients surgically treated for adolescent idiopathic scoliosis (AIS). The objective of this study was to evaluate pulmonary function to determine whether a more proximal upper instrumented vertebra (UIV) negatively impacts pulmonary function in patients surgically treated for AIS. There seems to be increasing concern that a more proximal extent of posterior thoracic spinal instrumentation and fusion reduces postoperative pulmonary function. However, there are few reports that analyze the relation between the selection of UIV and pulmonary function in AIS. PFT and radiographical examination of 154 patients with major thoracic AIS (Lenke type 1-4) undergoing posterior thoracic spinal instrumentation and fusion without thoracoplasty were completed prospectively. Patients were divided into groups based on UIV (T1-T3 vs. T4-T5) and Lenke curve type (2 and 4 vs. 1 and 3) and analyzed respectively. Demographic, radiographical measurements, and PFT data from preoperative and 2-year time points were analyzed. Patients with a structural upper thoracic curve (Lenke 2 and 4) had significantly lower preoperative PFT values than those without a structural upper thoracic curve (Lenke 1 and 3). Lenke 2 and 4 patients were also more likely to be fused proximally (82%, T1-T3) than those in the Lenke 1 and 3 groups (42%, T1-T3, P< 0.05). Preoperatively, those with UIV from T1 to T3 tended to have lower PFT values than those with UIV from T4-T5; however, only percent total lung capacity was statistically different (P< 0.05). Both UIV groups showed significant increases in all absolute values (forced vital capacity, forced expiratory volume in 1s, total lung capacity) at 2-year follow-up (P< 0.05) as expected with growth, and the percent predicted values (% forced vital capacity, % forced expiratory volume in 1s, % total lung capacity) remained stable. Although patients with UIV: T1-T3 showed slightly lower PFT values than UIV: T4-T5, the presence of a double thoracic curve was the primary cause of PFT reduction in these patients. Including the upper thoracic spine in the fusion had no significant effect on pulmonary function 2 years after surgical correction of AIS. 3.