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This disorder of immature
long bones is seen primarily in the human, horse and dog. Due to
a various set of circumstances which include diet, trauma, genetics and
body size and weight, growing long bones may develop cracks in the cartilage
of the weight bearing surface. These cracks may extend deep to the
soft (cancellous) bone beneath the cartilage and eventually a section of
the joint cartilage will separate from the underlying structure.
This cartilage flap, varying in size from less than a quarter of an inch
to over and inch in diameter, acts as an irritant in the joint. Subsequent
inflammation and attempts at healing can lead to scar tissue and calcium
deposits in the affected joint. Not a happy situation for a creature
who is growing and active!
The normal humeral
head has a very regular and smooth surface which slides forward and backward
under the joint surface of the scapula bone. In the x-ray image
above, the scapula bone (shoulder blade) can be seen above
the head of the humerus (upper arm bone). The rear surface of the
humeral head has a pitted area instead of continuing the smooth round surface
line of the joint. You can see the thin line that is the flap of
cartilage which has lifted off the surface of the head of the humerus.
We are seeing the circular cartilage flap edge-on so it appears as a thin
white line. This particular flap was about the size of a dime.
Every time this dog
would move the joint or bear weight on it, the flap would irritate the
underlying tissue and create pain and discomfort. That's why a dog
limps with this condition. Plus there often is inflammation and nerve
irritation simply due to the fact that the cartilage flap shouldn't be
there! This loose object in the joint can float about and create
what is termed a "foreign body" reaction.
The joint capsule is
actually a sealed chamber that contains lubricating joint fluid.
Any loose cartilage fragments are trapped in this space and can really
create pain if wedged between the two bones forming the joint. Most
cases of Osteochondritis Dissecans create low grade discomfort in the dog.
Extra joint fluid builds up, nerve endings are irritated, scar tissue and
calcium deposits can result from the body's defense mechanisms that are
trying to heal the defect.
In truth, there are
theories as to the causes but since this disorder seems to be spontaneous
and not so easy to predict, no one knows for sure why some dogs get OCD
and some don't. It is much more prevalent in Labrador Retrievers,
Golden Retrievers, German Shepards, Rottweilers and other large breeds.
It is uncommon in the small breeds. OCD almost always shows up during
the growth phase of a young dog's life... usually six to nine months of
age. OCD can affect the shoulder, ankle or elbow joint. It
may start as an intermittent limp in one front leg, or the dog may "hold
it out" or point the toes away from the midline more than the normal front
leg. Many young dogs with Osteochondritis Dissecans will run and
play with gusto; buy when their activity has slowed they recall that the
limb hurts and then return to favoring the leg. When laying down
they will take care to be gentle with the affected limb.
Some people believe
that an overweight, growing dog will be much more likely to acquire Osteochondritis
Dissecans than one that is trim. Physical impact on the limbs, such
as would occur in a dog that repeatedly jumps off of a deck or from the
back of a truck, may be a predisposing cause. Repeated impacts to
the surface of the humerus may separate the cartilage from the growing
soft bone beneath. Once the cartilage has detached, it takes very
special conditions of rest for any chance of the non vascular cartilage
to reattach. Non vascular means that there is no direct blood supply
and nutrients are transferred via a fluid medium.
Does diet play a role
in OCD? Yes! Diet plays a major role in everything a
dog does or is! An over fed pup who is carrying more weight than
optimum has a greater statistical chance of developing OCD than a
lean pup. That is NOT to say that you should underfeed a growing
pup just to avoid skeletal deformities! That line of reasoning has
been proven to be in error. Rather, be certain to feed high quality
meat-based diets that do not have grain as their first ingredient.
Diets with high protein and fat seem to be a better choice for dogs and
cats than those diets high in carbohydrates like corn, wheat, soybean meal.
Rather than a cure,
there is a treatment for Osteochondritis Dissecans. One treatment
method requires the dog to be confined to a pen for a number of weeks where
activity and jumping will be kept to a minimum. After four to ten
weeks of confinement there is about a sixty percent chance that the cartilage
defect on the humeral head will heal and the dog will return to normal
activity. This may be termed the conservative approach.
The most direct approach
and the one that returns the pup to normal activity the soonest is the
surgical approach. In surgery the veterinarian makes an incision
over the shoulder and accesses the shoulder joint. Opening
the joint space the surgeon inspects for any loose cartilage pieces and
rotates the humerus to expose the back side of the head of the humerus
where the defect comes into view. Usually the cartilage flap can
be grasped with forceps and lifted away from the humerus. Some surgeons
gently scrape the bed where the flap was situated in order to stimulate
faster healing and some leave the area as it is. The joint is flushed again
and closed with sutures.
The dog is rested for
about ten days and then gradually returned to activity. In successful
cases some dogs return to normal within two weeks. Other dogs will
take longer depending upon the size of the defect, how deep into the head
of the humerus the bed was eroded, the dog's weight and diet, and other
undefinable factors. Many veterinarians believe it is better to do
surgery rather than hope that weeks of rest will solve the problem (how
DO you make a young pup rest, anyway!?) . Once the surgery is done
the dog begins the healing process immediately.
Any dog that develops
a limp that does not improve within fourty eight hours should be checked
by a veterinarian.
