The "degenerative cascade" of
a degenerating disc
There is minimal blood supply to the disc, and
blood is what brings healing nutrients and oxygen
to damaged structures in the body. This
means that the spinal disc lacks any significant
reparative powers. Unlike muscles, which have
good blood supply, once a spinal disc is injured
it cannot repair itself.
Stages of degenerative disc disease
In the 1970’s, Kirkaldy-Willis first
described the "degenerative cascade" of
degenerative disc disease. He postulated that
after an individual suffers a torsional (twisting)
injury to the disc, the disc would degenerate
in three general stages.
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First, there is significant dysfunction caused
by the acute back pain of the injury.
-
Next,
there is a long phase of relative instability
at that particular vertebral segment and the
patient will be prone to intermittent bouts
of back pain.
-
Finally, the body re-stabilizes
the segment and the patient experiences fewer
episodes of back pain.
Based on the observation that demographic studies
show less back pain from degenerative disc disease
in elderly adults (over 60 years) than in younger
adults (30 to 50 year-olds), he also concluded
that this process happened over a period of 20
to 30 years. Although elderly patients
may have pain from facet osteoarthritis, it is
uncommon for them to have disc problems.
While
this summary is a simplification of Kirkaldy-Willis’s
extensive work, it lays the framework for what
is known today. We do know that lumbar disc degeneration
is a very common and natural process, and only
in limited cases does it become painful.
Degenerative disc disease and low back pain
The natural history
of lumbar degenerative
disc disease is relatively benign. The pain tends
to be intermittent, and although at times the
pain may seem to be getting worse, the painful
symptoms are generally not progressive. While
the disc degeneration will progress, the low back pain and other symptoms do
not tend to get worse with the progression of the degeneration.
Many patients
worry that if they
are have a lot of
low back pain when
they are only 35
years old, the pain
will become much
worse and they may
be in a wheelchair
by the time they’re
in their sixties. However, if patients can find
a way to manage their back pain and maintain
their function, the natural history is really
quite favorable. With continued disc degeneration,
all the inflammatory proteins within the disc
space will eventually burn out, and the disc
will usually become stiffer, thus decreasing
micro-motion. In fact, someone who is 65 years
old is actually less likely to have discogenic
back pain than someone who is 35 years old. |