The problem of roentgenographic evaluations of vertebral rotations has been studied using upper thoracic, thoracic, and lumbar segments of a normal spine which were marked with wires and which then had roentgenograms made in known increments of rotation. The results showed a definite difference between a grading system based upon the position of the spinous process and a system based on the position of the pedicle located on the convex side of the curve. The pedicle technique proved to have definite merit in its case of application over a wide range of rotation and its over-all consistecy of values evens when applied to the scoliotic spine.
As an additional part of the study, the approximate range of degrees of rotation represented by each grade of rotation was determined.
Finally, by combining the two parts of this study, we were able to propose a simplified method of describing vertebral rotation, which correlates the amount or percentage of convex pedicle displacement seen on roentgenograms with the approximate degrees of rotation present in that vertebra.