SPONDYLOSIS
DEFORMANS
by Fred Lanting
Spondylosis deformans
is a condition in which bridges are formed along the ventral (bottom) parts of
the vertebrae. It has been diagnosed in man, domestic cats (68%, yet no
symptoms!), bulls, and even whales as well as in dogs. The term “spondylitis” literally means “an inflammation of the
spine”, especially the bone, and spondylosis is
sometimes used as a synonym as well as for describing types of ankylosis. One of these types is a bone proliferation,
usually on the ventral surfaces of adjacent vertebrae, producing a bridge from
one to the other. This condition is best known as spondylosis
deformans. There is no spinal cord compression, but
the spine is immobilized in that location. If the condition continues to
spread, there may be several such bridges, “welding” a series of vertebrae into
an inflexible backbone. It is seen fairly easily via lateral radiography.
Because of different degrees seen in different breeds, I believe there to be
more than one genetic determinant for this disorder, though nutrition may play
a modifying role. I know full well the familial line in a significant portion
of American German Shepherd Dogs with this problem, but there are some “German”
lines with it, too. Pain may come from encirclement or pressure on nerve roots
leading out from the cord to peripheral nerves, although such discomfort might
be from concurrent arthritis, cauda equina syndrome, or other problems. As in Wobbler Syndrome, much growth of osteophytes
can occur, and may be part of the reason some dogs have pain, but generally the
animal does not appear to be suffering.
It is not completely
clear how this disorder progresses, but it may start with a breakdown of Sharpey’s fibers, which are the fibers making up the annulus or outer portion of the intervertebral disks. Subsequently, inner disk material
protrudes, stretching the longitudinal ligament, and promoting the appearance
of osteophytes which grow out from the vertebral
bodies in such a way that one cannot tell where the original bone ends and the osteophytic growth begins. Before that happens, though,
separate ossification centers can be seen forming a
few millimeters from the vertebral bodies; they later
fuse and grow toward the adjacent vertebral segment. Eventually, and depending
on breed and family history, the disk spaces between particular segments are
bridged. True ankylosis (complete fusion into a
continuous bony bridge between vertebrae) is far less common than the
near-junction of these osteophytes. Very seldom do
the osteophytes grow upward or in such a way as to
pinch the spinal cord or otherwise cause neurological signs, so spondylosis deformans might be
considered a relatively benign disorder when compared with HD, elbow dysplasias, wobbler syndrome,
etc.
Many affected dogs live
satisfactory lives, though somewhat limited in flexibility and range of motion.
Fortunately, by the time spondylosis deformans becomes noticeable in clinical signs, the dog may
be considered “retired” from his duties of running around, jumping, and doing
the other things expected of a youngster. In some individuals, it will get
worse suddenly rather than continue in a gradual worsening. Possibly, trauma
may bring fracture of the bridge created in the development of spondylosis, which crack may spread to the arch and body,
thus pinching the cord.
Often, spondylosis will be discovered on radiographs incidentally
while the vet is looking for something else, such as a cause for lameness. In
some of these cases, he may be tempted to make his diagnosis right then, and
not to look further for the actual main cause, which may include HD, osteochondrosis in other joints, tumors,
and others. Osteoarthritis of the spine (inflammation of the joints between
vertebrae) is not the same disorder, nor is true spondylitis
(an inflammation of the vertebrae themselves, brought on by either trauma or
infection). Remember that “-itis” means inflammation,
and spondylosis deformans
is a non-inflammatory degenerative disease.
An intervertebral
inflammation resulting in fusion of the vertebrae has been seen in humans and
is known as ankylosing spondylitis.
It is related to both adult and juvenile rheumatoid arthritis, and the
similarity to spondylosis deformans
in the dog (minus the inflammation) makes me wonder if there is a common or
similar genetic defect in the “immune systems” of man and beast. Although it
has been misnamed ankylosing spondylitis
in the past, spondylosis deformans
in the canine is not that disorder, exactly. Senile ankylosing
hyperostosis is a syndrome in humans that is considered to be a variation of
osteoarthritis characterized by large osteophytes,
bridging between and on the anterolateral (front and
side) surfaces of the vertebral bodies. In man, it appears mainly in males over
50 years of age, giving symptoms of minor to moderate back pain, stiffness, and
lack of flexibility. Bone spurs and ossification in tendons and ligaments are
common. Even intervertebral osteochondrosis
may be a separate disorder; although also a result of disk degeneration, it is
characterized by reduced disk height and vertebral end-plate sclerosis, not
seen in spondylosis deformans.
The genetic
transmission of the tendency to develop this disease is obvious to anyone who
has watched it appear in offspring of certain dogs, generation after
generation. But exactly how (the etiology)
is not as sure. Perhaps there is an inherited weakness in how a dog’s
vertebrae respond to or withstand repeated microtraumas;
perhaps in some lines, the blood vessels that serve the outer layers of the
disks regress and disappear faster than the normal or expected three or four
years. It seems to be a fairly natural consequence of aging, as 75% of dogs in
some breeds are affected to some degree by 9 years, and half by 6 years. On the
other hand, some work has indicated that spondylosis deformans is more a disease of middle age. Breed and family
variables make the incidence figures vary tremendously. It became a very
noticeable disorder in the German Shepherd Dog when, for a while, 90% of the
“show” German Shepherd Dogs in the USA were allegedly descended from one very
popular late-1960s American Grand Victor (estimate based on a pedigree study
reported in a GSD magazine several years ago) who had and passed along this
disease in a severe form.
A couple of other
miscellaneous thoughts about spondylosis: Regarding
the effect or influence of environment, small trauma has already been mentioned
as a possible factor, but with little evidence. It is suspected that bulls on
high-calcium diets may have increased susceptibility. Males seem more at risk
than females.
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Illustrations can be found in
“The Total German Shepherd Dog” (Hoflin, 1999), page 212.
You may “lift” that or the one you find on this website only if it accompanies
the above article, which must carry the copyright notice. “Copyright,
1990, by Fred Lanting. Used
with permission.” (Anyone wanting to re-use this article must ask for
permission to do so, and give full credits such as the info in this paragraph.)
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Copyright 2001 Fred Lanting, Canine
Consulting. Mr.GSD@juno.com. All rights reserved. Used
with permission. Please view his site Real GSD.
NOTE: A well-respected AKC
and Schaferhund Verein
judge, Mr. Lanting has judged in more than a dozen
countries, including the prestigious FCI Asian Show hosted by Japan Kennel
Club, the Scottish Kennel Club, a Greyhound specialty in