Lung function asymmetry in children with congenital and infantile scoliosis

Abstract

Background context Progressive scoliosis alters lung function by reducing chest wall compliance and excursion and rotating intrathoracic contents, producing an increasingly asymmetric lung size. The effect of this distortion on regional lung perfusion and ventilation has not been described in children with congenital and infantile forms of scoliosis. The severity of scoliosis is often described by the Cobb angle of the spine, but the relationship between Cobb angle and lung function asymmetry between concave and convex lungs has not been described in this group of children. Purpose To describe the frequency of asymmetric lung perfusion and ventilation among children with congenital or infantile thoracic scoliosis before surgical treatment and the relationship between Cobb angle and asymmetry of lung function. Study design/setting Prospective comparison of lung perfusion scans and spine film findings in children evaluated in two pediatric spine referral clinics for expansion thoracoplasty and vertical expandable prosthetic titanium rib (VEPTR) implantation. Patient sample Thirty-nine children, aged 1 year 8 months to 15 years 6 months, with congenital or infantile forms of scoliosis who are clinically stable outpatients and have neither primary pulmonary disease nor neuromuscular weakness. Outcome measures 1) Cobb angle measurements from weightbearing spine films and 2) right and left contributions to total lung perfusion and total lung ventilation compared with normal values. Methods Lung perfusion scans using technetium-labeled albumin macroaggregates were performed in all children; 15 of the children also underwent ventilation lung scans using aerosolized technecium-labeled diethylenetriaminepentaacetic acid (DTPA). The degree of asymmetry between right and left lung function from the normal right-to-left lung distribution was correlated with the Cobb angle of the spine. Ventilation and perfusion asymmetry between right and left lungs was also compared. Results Sixteen of the 25 children with congenital scoliosis had fused ribs; 13 additional children had infantile scoliosis. Cobb angles ranged from 30° to 112° in the group (median=71°), with the concave lung being the left lung in 61% of cases. Lung function relations between the right and left lungs were abnormal (>5% deviation from the normal 55% right [R]/45% left [L]) in 21 (54%) patients. Right-left contributions to lung perfusion ranged from 86% R/14% L to 26% R/74% L among the 39 children. Lung function in the concave lung was reduced below the normal proportion in only 20 children (51%). Lung function asymmetry, measured as the deviation from the normal contributions of the right and left lungs, did not correlate with Cobb angle values (r=.14, p=.4). Ventilation asymmetry and perfusion asymmetry were concordant and correlated closely (r=.93, p<.0001). Conclusions Asymmetric ventilation and perfusion between the right and left lungs occurs in more than half of the children with severe congenital and infantile thoracic scoliosis. However, the severity of lung function asymmetry does not relate to Cobb angle measurements. Asymmetry in lung function is influenced by deformity of the chest wall in multiple dimensions, and cannot be ascertained by chest radiographs alone.