Prevalence and Key Radiographic Spinal Malalignment Parameters Associated with the Risk of Pulmonary Function Impairment in Patients Treated Surgically to Correct Adult Spinal Deformity

INTRODUCTION: There is a significant relationship between pulmonary function and degree of spinal deformity, location of apical vertebrae, and coronal imbalance in patients with childhood spinal deformity. By contrast, the pathophysiology, epidemiology, and influence of deformity on respiratory dysfunction in patients with adult spinal deformity (ASD) remain largely unknown. We sought to clarify and compare the prevalence of pulmonary function impairment in patients with ASD with that in patients with lumbar spinal stenosis (LSS), to determine radiographically which spinal malalignment parameters are associated with a risk of respiratory dysfunction, and to determine the association of respiratory dysfunction with corrective surgery. METHODS: We conducted a prospective study of consecutive patients with a diagnosis of ASD or LSS who underwent spinal surgery. We included data from 122 consecutive patients with ASD and 121 consecutive patients with LSS. Parameters were obtained from full-length lateral radiographs taken with the patients standing and in supine and prone positions. We compared respiratory dysfunction between a group of patients with ASD and LSS and determined correlations between respiratory dysfunction and spinopelvic parameters. RESULTS: Preoperative % forced vital capacity (FVC) of patients with ASD was significantly lower than that of patients with LSS, and the frequency of restrictive ventilatory impairment was significantly higher in those with ASD (15.7%) than those with LSS (7.4%). Thoracolumbar kyphotic curvature (TK) while the patients were in supine position was significantly greater in the group with restrictive ventilatory impairment, and a significant negative correlation was found between %FVC and TK with the patients in supine position. We found no significant improvement of respiratory dysfunction 1 year after surgery. CONCLUSIONS: Spinal deformity is a potential risk factor for restrictive ventilatory impairment in the elderly. We propose that radiographs obtained when patients are in supine position are valuable for evaluating the flexibility of the TK. Rigid TK might be an etiology of restrictive ventilatory impairment in patients with ASD.