Application of a stereoradiographic method for the study of intervertebral motion.

A technique of three-dimensional reconstruction along with a method of adjusting anatomic landmarks were used to evaluate movements of the lumbar vertebrae of living subjects. Altogether, 16 subjects took part in the experiment. Each subject was radiographed in an upright standing position, and in each of the following positions: flexion, extension, axial rotation, and lateral bending. The results of the three-dimensional reconstruction procedures and the correction of anatomic landmarks show an adequate level of accuracy for experimentation with living subjects. The mean relative displacements of lumbar vertebrae in rotation are 10 degrees of flexion, 3 degrees of extension, 5 degrees of lateral bending, and 1 degree of axial rotation.