Transitional lumbosacral discs. probability of herniation.

The charts and roentgenograms of 200 patients operated upon for lumbar disc herniations were reviews. Among them, there were 42 persons in whom a lumbosacral transitional vertebra existed. The discs beneath these vertebra varied in appearance. A descriptive classification for the four disc types is proposed. In none of the 42 patients were there myelographic evidence of herniation of such a disc. In five instances, such disc were surgically inspected, and no protrusion was uncovered. Before transitional discs are operated upon, the proof of herniation should be incontrovertible.