Correlation of Preoperative Deformity Magnitude and Pulmonary Function Tests in Adolescent Idiopathic Scoliosis

STUDY DESIGN: Clinical study correlating preoperative pulmonary function tests (PFTs) to radiographic measures of thoracic deformity severity in adolescent idiopathic scoliosis (AIS) patients. OBJECTIVE: To determine (1) the incidence of clinically relevant (<65% predicted value) pulmonary impairment in AIS patients; (2) if patients with more severe deformity have greater impairment of PFTs than those with lesser deformity; (3) the effect, if any, of juvenile onset deformity (onset 65%. Patients with MT curves>70°, and especially >80°; proximal thoracic (PT) curves which were >30° or structural; or T5-T12 kyphosis<10° had significantly (P≤0.001) lower FEV1 or FVC compared to those with less deformity. Axial plane deformity did not correlate with PFT impairment. Juvenile-onset patients had greater PFT impairment than AIS patients, along with slightly larger MT curves. Patients who were braced before surgery had worse PFTs than those had no treatment before surgery. CONCLUSION: Preoperative PFTs are clinically impaired in 19% of AIS patients, and correlate significantly with the MT and sagittal plane deformity severity, and with PT curve severity to a lesser degree. PFTs do not correlate with degree of axial deformity. From a purely pulmonary standpoint, attention directed to coronal and sagittal plane deformity correction appears warranted, to address the specific deformities which are associated with PFT impairment.