[Osseous support in spondylolisthesis. A case report]

A true spondylolisthesis in a 14 year old boy was followed from grade II to maximal dislocation. The 5th lumbar vertebra slipped forward on the sacrum until the contact with the sacrum was lost. The 5th lumbar vertebra, which had in the meantime shrunk to a smaller sized wedge, then dropped without tilting in front of the 1st sacral vertebra. This kind of maximal dislocation is rare. In the course of many years a bony support for the spine developed in the shape of a second sacrum, lying ventrally to the anatomical sacrum. The vertebral arch of the forth lumbar vertebra was supported by the real sacrum. This biomechanical correction was unexpected. At the age of 33 years the patient suffers no pain, and there is no restriction of spine movement and no neurological deficit.