THE NORMAL AND PATHOLOGICAL PHYSIOLOGY OF THE NUCLEUS PULPOSUS OF THE INTERVERTEBRAL DISC

An Anatomical, Clinical, and Experimental Study

¹ The Department of Surgery, Division of Orthopaedic Surgery, The University of Chicago Medical School

1. The assumption of von Luschka and of later embryologists that the intervertebral nucleus pulposus is a vestigial remnant of the notochord has been disproved. It is a highly specialized structure.

2. The nucleus pulposus is not formed from degeneration of the annulus fibrosus fibers as postulated by Virchow and Dursy.

3. This anatomical entity is formed by the proliferation and mucoid degeneration of the notochord cells, followed by a fibrocartilaginous invasion derived from the original mesenchymal intervertebral cells, which form a fibrocartilage envelope.

4. The cartilage plate and the epiphyseal ring are genetically one structure and are comparable to the epiphyses of the long bones.

5. The nuclei pulposi are essential for the normal physiological functions of the spine.

6. Loss of nucleus pulposus material as a result of trauma or disease is probably one of the frequent etiological factors associated with pain in the back and disability.

7. Clinical and experimental evidence has been presented to indicate that degenerative, hypertrophic arthritis of the spine may result from the loss of the intervertebral shock absorber and hydrodynamic ball bearing of the spine, the nucleus pulposus.

8. If the cartilage plate of the intervertebral disc of a dog is injured by a scalpel or drill, nuclear material prolapses into spongiosa and a cartilage nodule forms.

9. If the nuclear material is allowed to escape, the rest of the disc becomes thinned out and the margins of the adjacent vertebrae become sclerosed with subsequent marginal lipping.

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