The posterior surface of the lumbar vertebral bodies. Part 2: An anatomic investigation concerning the curvatures in the horizontal plane.

The horizontal curvatures of the posterior surfaces of the lumbar vertebral bodies have been quantitatively evaluated by means of a simple measuring device. The measurements have been done near the superior and inferior vertebral margins. The aims of the study were: to obtain exact information on the degrees of curvatures and their interindividual variations and further compare the information obtained with current knowledge of the relevant embryologic and mechanical factors involved to explain the curvatures and to use the results as a basis for a theory on the development of some of the forms of lumbar canal stenosis. A horizontal concavity was always found in L1-L3, in L5 a posterior convexity was prevailing, and L4 occupied an intermediate position. The degree of medullary ascent and its relationship in time to vertebral development are probably important and are, together with the three first mentioned factors discussed, determinants in the evolution of lumbar canal stenosis. The results are discussed in light of a possible influence on moulding of the vertebrae caused by the contents of the spinal canal and the vertical load of the body weight.