THORACIC VOLUME CHANGES IN SCOLIOSIS SURGERY

Study Design. Eighteen patients with adolescent idiopathic scoliosis t reated with ISOLA instrumentation and 13 treated with Cotrel-Dubousset instrumentation were studied before and after surgery with computed t omography scans. Objectives, To analyze and compare the immediate chan ge in chest volume of patients treated with the derotation method of C otrel-Dubousset versus the sublaminar wire translational technique of ISOLA. Summary of Background Data. Previous literature suggests a smal l but variable improvement in pulmonary function with the use of Harri ngton instrumentation when treating adolescent idiopathic scoliosis. T he effect of modern instrumentation techniques on chest volume and ult imately pulmonary function has not been determined. Methods. An axial computed tomography slice was made through each vertebral body from T3 to T10. Using a technique of spine curve measurements, the cross-sect ional area at each level was computed, and from the height measured, t he volume of the thoracic cage was computed. Results. Single thoracic curves (King-Moe Type III) managed with ISOLA sublaminar instrumentati on showed a statistically significant increase in chest volume when co mpared with other curve types and when compared with all curves manage d with Cotrel-Dubousset. Seventeen of 18 patients treated with ISOLA i nstrumentation gained chest volume, whereas half of those treated with Cotrel-Dubousset actually lost volume. Conclusions. ISOLA instrumenta tion and sublaminar wiring appears to increase the chest volume in pat ients with adolescent idiopathic scoliosis. Its clinical significance remains to be determined.