Estimation of vertebral rotation and the spinal and rib cage deformity in scoliosis by computer tomography.

Computer tomography (CT) presents a method of determining longitudinal axis vertebral rotation and vertebral, spinal, and rib case deformity. Different rotation angles, distances, and indexes are defined and discussed. Radiation risks were evaluated and considered exceedingly small when compared to the ordinary spinal anteroposterior radiograph. In a model study the mean difference between actual vertebral rotation and measured rotation was 0.3 degrees if the vertebrae were tilted up to 20 degrees in either the frontal or sagittal plane. This accuracy was lost if the vertebrae were tilted 20 degrees in both the frontal and the sagittal plane. Computer tomography can be used for evaluation of the vertebral rotation in the frontal plane.