Restrictive pattern of pulmonary functions in idiopathic and congenital scoliosis following spinal fusion

Summary This paper presents the results of pulmonary function analysis in 141 subjects. Thirty-five of these were patients with adolescent idiopathic scoliosis, 36 had congenital scoliosis, and the remaining 70 were age-, sex-, height-, weight- and arm-span-matched normal subjects used as controls for adolescent idiopathic scoliosis. The patients with adolescent idiopathic scoliosis had their pulmonary function evaluated pre- and post-operatively. At pre-operative evaluation the mean age was 13.7 years and the mean cobb angle 48°; at post-operative evaluation the figures were 17.1 years and 36° respectively. In the congenital scoliosis group the mean age was 14.5 years and the mean Cobb angle 42°, and pulmonary functions were evaluated at a minimum of 3 years after surgery. The results are as follows: Adolescent idiopathic scoliosis: (i) Marked disproportion was found in the pulmonary volumes following spinal surgery. After taking growth of the thoracic cage into account, the total lung capacity remained unchanged whilst the vital capacity was significantly reduced and there was a significant increase in residual volume. (ii) This disproportionate increase in residual volume was further confirmed by very highly significantly increased residual volume/vital capacity and residual volume/total lung capacity ratios at post-operative evaluation compared to pre-operative ratios (Mann-Whitney test, P=0.001). (iii) The residual volume was 48% of vital capacity pre-operatively compared to 35% in normal controls. The percentages increased to 70% post-operatively, whilst it was unchanged in the matched controls. Congenital scoliosis: (i) The mean residual volume was markedly increased (154% of predicted value). (ii) Vital capacity was significantly reduced in surgically treated patients (68% of predicted values). (iii) This pattern of reduced vital capacity was more marked in those patients who had multiple thoracic anomalies and were treated surgically (46% of predicted value). However, those patients with multiple thoracic anomalies who did not require surgery did not show such reduction of vital capacity. Comparison between idiopathic and congenital scoliosis: (i) In unoperated patients, the percentages of predicted values of total lung capacity, vital capacity and residual volume were significantly greater in congenital scoliosis than in adolescent idiopathic scoliosis. (ii) Post-operatively there was no significant difference in the percentages of predicted values of total lung capacity, vital capacity and residual volume between patients with congenital scoliosis and those with adolescent idiopathic scoliosis, despite the difference in pathogenesis. These findings have relevance to scoliotic patients treated with spinal fusion with regard to their capability to perform strenuous physical activities.