To our knowledge, there have been few reports on injuries in which the spine dissociated from the pelvis. Das De and McCreath identified eleven patients who had had a dislocation at the lumbosacral level in their review of the literature and then reported on four patients of their own. This report and another described unilateral facet dislocation, and others have reported bilateral facet dislocations with varying degrees of anteroinferior spondylolisthesis. The plane of injury may extend from the disc space into the sacrum, producing a fragment of the anterior aspect of the sacrum that remains attached to the disc and to the body of the fifth lumbar vertebra. There are similarities between these injuries and the transverse fractures of the upper part of the sacrum that were described by Roy-Camille et al. and also by Fountain et al. The present report describes a patient who had a displacement of the lumbar spine anteroinferiorly into the pelvic vault.