Intervertebral disk extensions into the adjacent vertebral bodies or into the spinal canal have until recently been unknown. Schmorl,1 in 1926, was the first to direct attention to this pathologic condition. On removal and sagittal sectioning of the vertebral column in routine postmortem examinations, he found one or more intervertebral disk extensions in the vertebral bodies in 38 per cent of the spines examined. Schmorl named these areas of disk invasions of the bodies cartilage nodes (Knorpel Knötchens). In 1929, both Andrae2 and Schmorl3 described similar disk extensions into the spinal canal.
Since Schmorl's first description of the pathologic picture of the intervertebral disk extensions into the vertebral bodies, a number of papers dealing with the clinical phase of this subject have appeared in the German literature. Schanz,4 in a paper on the vertebral column and trauma, suggested the possibility of a direct causal relationship between