Relation of spinal and thoracic cage deformities and their flexibilities with altered pulmonary functions in adolescent idiopathic scoliosis

Abstract

Study Design. Seventy patients (average age, 13.8 years) with adolescent idiopathic right thoracic scoliosis had full assessment of pulmonary functions and radiographic evaluation of spinal and thoracic cage deformities and their flexibilities. Objectives. To determine how measurements of spinal and thoracic cage deformities related to pulmonary function. Summary of Background Data. Pulmonary functions have been evaluated in relation to lateral curvature of the spine in most of the published studies. Scoliosis is a three-dimensional deformity. There is a need to evaluate these changes in pulmonary functions, reflecting not only spinal curvature but also rotational deformity, thoracic cage deformity, and their flexibilities. Methods. Radiographic measurements obtained from anteroposterior and lateral standing and anteroposterior supine bending radiographs included lateral curvature, vertebral rotation, kyphosis, maximum sternovertebral distance, and apical rib-vertebral angles. Using previous measurements, the flexibility of the curve, vertebral rotation, and rib-vertebral angle were calculated. A pulmonary function assessment was performed using a computerized pulmonary function system (5000V; Gould, Dayton, Ohio). We analyzed pulmonary functions in relation to deformity. Results. Measurements reflecting spinal deformities obtained from anteroposterior radiographs, such as Cobb angle, vertebral rotation, and vertebral rotation flexibility, were significantly correlated with the percent of predicted values of vital capacity and forced vital capacity, whereas kyphosis measured from lateral radiographs was significantly correlated with absolute values of residual volume, total lung capacity, functional residual capacity, and forced expiratory flow from 25- 75% of the forced vital capacity (FEF25-75). Of the measurements reflecting thoracic cage deformity obtained from anteroposterior radiographs, rib-vertebral angle asymmetry (measured from supine bending radiographs) showed significant correlation with the percent of predicted values of vital capacity, forced vital capacity, and functional residual capacity, whereas the sternovertebral distance that was measured from lateral radiographs correlated significantly with absolute values of vital capacity, total lung capacity, forced vital capacity, and FEF25-75. Conclusions. Deformities in coronal and transverse plane influence changes in pulmonary functions expressed as the percent of predicted values, whereas sagittal plane deformities influence mainly those absolute volumes in which residual volume is a component. It is suggested that rotational flexibility combined with other deformities could be evaluated in future studies on prediction of pulmonary function from the measurements of the deformity.