The posterior surface of the lumbar vertebral bodies. Part I.

The degree of concavity (ie, the scalloping) on the posterior surface of the lumbar vertebral bodies has been evaluated quantitatively by means of a simple measuring device. The scalloping in the median sagittal plane was found to differ from that in the lateral plane, near the pedicular attachments. In the medial plane, an increase in scalloping from L1-L4 was noted, with a subsequent decrease at L5. Laterally, the concavity deepened from L1-L5, the values here being larger than those medially at all levels. The results are discussed with respect to the anatomy of the dural sac and its contents, and the spinal nerves. Scalloping in the lateral sagittal plane is, especially at the fourth and the fifth lumbar levels, presumed to be caused mainly by pressure exerted by the spinal nerves. The medial scalloping is presumed to be partially due to hydrostatic pressure of the cerebrospinal fluid in the dural sac. This pressure will, at the edges of the superior and inferior end-plates, be counteracted by the tractional stresses of the fibers of the discal annulus fibrosus that are inserted at the vertebral margins. This effect contributes to the final shape of the vertebral bodies. The posterior vertebral surface constitutes part of the anterior wall of spinal canal. Therefore its shape has relevance in cases of spinal stenosis, and some aspects of this relationship are discussed.