Thoracic volume changes in scoliosis surgery.

Study Design: Eighteen patients with adolescent idiopathic scoliosis treated with ISOLA instrumentation and 13 treated with Cotrel-Dubousset instrumentation were studied before and after surgery with computed tomography scans.
Objectives: To analyze and compare the immediate change in chest volume of patients treated with the derotation method of Cotrel-Dubousset versus the sublaminar wire translational technique of ISOLA.
Summary of Background Data: Previous literature suggests a small but variable improvement in pulmonary function with the use of Harrington instrumentation when treating adolescent idiopathic scoliosis. The effect of modern instrumentation techniques on chest volume and ultimately 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-sectional area at each level was computed, and from the height measured, the volume of the thoracic cage was computed.
Results: Single thoracic curves (King-Moe Type III) managed with ISOLA sublaminar instrumentation showed a statistically significant increase in chest volume when compared with other curve types and when compared with all curves managed with Cotrel-Dubousset. Seventeen of 18 patients treated with ISOLA instrumentation gained chest volume, whereas half of those treated with Cotrel-Dubousset actually lost volume.
Conclusions: ISOLA instrumentation and sublaminar wiring appears to increase the chest volume in patients with adolescent idiopathic scoliosis. Its clinical significance remains to be determined.