[Specific aspects of mobility and changes in the shape of the dural sac in functional lumbosacral myelography].

The purpose of the work was an analysis of lateral myelograms of the lumbosacral spine in the neutral position, in anteflexion and retroflexion from the aspect of the mobility of the dural sac and its relationship to the spinal canal. The group comprised 50 patients with clinically obvious discopathies and other vertebrogenic syndromes. The areas of the dural sac were measured planimetrically and evaluated by means of a computer. It was revealed: 1. The Soinal canal and dural sac are not static variables but dynamic ones. By movements of the lumbosacral spine the size of the dural sac changes and so does its shape. These phenomena can be evaluated not only qualitatively but also quantitatively. 2. The anteroposterior diameter of the dural sac on the myelograms in anteflexion and in retroflexion changes significantly, as compared with the neutral position, it increases during anteflexion and diminishes during retroflexion. 3. The area of the dural sac increases during anteflexion and diminishes in retroflexion, as compared with the neutral position. 4. Changes in the shape of the dorsal portion of the dural sac revealed in the segment of the discopathy are considered to be due to hypertrophy of the yellow ligaments.