Pulmonary function in adolescent idiopathic scoliosis: a 25 year follow up after surgery or start of brace treatment

BACKGROUND Pulmonary function in patients with adolescent idiopathic scoliosis many years after posterior spinal surgery or brace treatment has not been documented. METHODS A consecutive group of patients treated by posterior fusion or a brace at least 20 years previously was investigated. 90% attended a clinical follow up. Lung volumes were determined before treatment in 251 patients, 1.4 years after surgery in 141 patients, and 25 years after surgery or start of brace treatment in 110 patients. Vital capacity (VC) was calculated as percentage predicted according to height and age and the results were corrected for loss of height due to scoliosis. Scoliosis angles were measured and smoking habits were recorded. An age and sex matched control group was also examined with the same questionnaire and pulmonary function tests. RESULTS VC increased from 67% predicted immediately before surgery to 73% (p<0.001) after surgery and to 84% (p<0.001) at the present follow up, mean change 10.8% (95% CI 9.5 to 12.1). In the brace treated patients VC increased from 77% predicted before treatment to 89% (p<0.001) 25 years after start of treatment, mean change 12.3% (95% CI 10.5 to 14.1). The mean Cobb angle at the present follow up study was 40° in both surgically and brace treated patients. The present results of lung volumes did not correlate with pretreatment or post-treatment Cobb angles or smoking habits. CONCLUSIONS Patients treated by posterior fusion or a brace gradually increase their pulmonary function up to 25 years after treatment. Smoking and curve size are not risk factors for reduced pulmonary function.