The Journal of Bone and Joint Surgery, Vol 72, Issue 2 220-229, Copyright © 1990 by Journal of Bone and Joint Surgery, Inc
Histological changes in aging lumbar intervertebral discs. Their role in protrusions and prolapses
T Yasuma, S Koh, T Okamura and Y Yamauchi
Department of Orthopaedic Surgery, Kouto Hospital, Tokyo, Japan.
To study the relationships between the changes due to aging in lumbar
intervertebral discs and the development of protrusion or prolapse, we
carried out histological studies on operative specimens of thirty-one
discs, of which twenty-two had been protruded and nine, prolapsed. The
specimens were obtained during twenty-nine operations for herniation of a
lumbar intervertebral disc in patients who were sixty years old or older.
Changes in the anulus fibrosus were more extensive in the nine prolapsed
discs than in the twenty-two protruded discs. Of the nine prolapsed discs,
myxomatous degeneration, fibrosis, and swollen anular fibers were found in
all nine, and cysts were seen in five. Of the twenty-two protruded discs,
only five showed myxomatous degeneration; ten, fibrosis; one, a cyst; and
sixteen, swollen fibers. For comparison, we also studied specimens that had
been obtained at operation from twenty-one other patients, twenty to
fifty-nine years old, who had a prolapsed disc. The anulus showed
myxomatous degeneration in all twenty-one specimens, cysts in eight, and
fibrosis in ten. In addition, we examined 368 autopsy specimens from people
who had been between twenty-five and eighty-five years old at the time of
death. In many of the subjects who had died in the sixth decade of life or
later, we found that the orientation of the inner fiber bundles of the
anulus fibrosus was reversed, so that they bulged inward. The reversal
appeared to be the result of myxomatous degeneration of the middle fibers
of the anulus, atrophy of the nucleus, and narrowing of the disc space.
These histological findings suggest explanations for the predominance of
protrusions of the nucleus pulposus in patients who are less than sixty
years old and of prolapse of the anulus fibrosus in the few patients who
are more than sixty years old who have herniation of an intervertebral
disc.
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