ULTRASTRUCTURAL INVESTIGATION OF LUMBAR INTERVERTEBRAL DISCELECTRON MICROSCOPIC OBSERVATION OF NORMAL, PROTRUDING AND RUPTURED DISCS

We studied normal lumbar intervertebral discsof rat, rabbit and man (fetus and adult) by transmis-sion electron microscope. It was found that althoughthe annulus fibrosus was composed of fibrocartilage,the cells in the lacunae of the fibrocartilage showedconfiguration transition from fibroblasts tonotochordal cells. Elastic fibers could be detectedin the annulus. Nucleus pulposus containednotochordal cells which may exist singly or in stacksin a loose matrix. In patients with protruding or ruptured lumbarintervertebral discs, the diseased disc materialoriginated from the nucleus pulposus, the superficialstratum of the annulus fibrosus, and the cartilaginous tissue. Both living and degenerate notochordalcells existed in the nucleus pulposus. In thecartilaginous tissue, chondrocytes showed activesecretory function or underwent interstitial growthand degeneration. The cellular component of thesuperficial stratum of the annulus fibrosus was com-prised mainly of living fibrocartilage cells similarto fibroblasts.