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ABOUT CANINE HIP DYSPLASIA
The equation of dysplasia: P (phenotype) = G (genetics) + E (environment)
Definition of canine hip dysplasia (CHD): a developmental defect initiated by
the genetic predisposition to the subluxation (dislocation) of a joint
The hip joint is a ball and socket joint. The socket or acetabulum, is situated
within the pelvis, the ball or hip head, is located at the end of the femur
(thigh bone) in a normal hip joint, the ball fits closely and deeply into the
socket both (ball and socket) rotate smoothly, are cushioned by cartilage and
lubricated with a joint fluid (synovial). The better the fit of these parts, the
less wear the joint experiences, and the longer it functions efficiently.
When the joint is loose, this causes abnormal wear of the joint components; this
wear can distort the joint - leading to a degenerative joint disease (DJD) or
arthritis. Hip dysplasia is a condition of abnormal development of-or within the
hip joint, that results with joint instability (unsteadiness). The condition of
developmental hip dysplasia can develop over the first few weeks, months, or
years of a dog's life.
It is not uncommon for elbow dysplasia to occur with hip dysplasia; especially
since dogs with hip dysplasia may experience an altered gait. Elbow and hip
dysplasia can occur on one or both sides. The common symptom is a lameness that
will shift the legs from a natural position, and cause a swaying gait.
It is important to realize that the underlying factor, or causes for dysplasia
are genetic. The genetic predisposition (tendency) for dysplasia causes the body
react to certain diets, activities and environmental factors, which in turn -
enhances the dysplastic condition. Several genes interact (polygenetic) to
produce this condition, consequently making it difficult to isolate or eliminate
that one particular gene. Breeders who are cautious about testing for the
condition, help to decrease the occurrence by controlling environmental factors:
i.e. diets, exercise and selective breeding pools. Outside factors which have
been suggested as influencing the development of dysplastic components are:
overweight, extreme amounts of protein and energy rich foods, rapid growth
rates, excessive exercise, or lack of exercise, and high calcium intakes.
Studies have proven that mating only dogs with radiographically normal hips have
noticeably reduced dysplasia.
Elbows are also subject to dysplasia and can be equally debilitating
(incapacitating). Elbow dysplasia is a condition diagnosed as: ununited anconeal
process (UAP). The elbow consists of three bones, the radius, and the ulna �
which make up the forearm (ulna, being the longer of the two bones) and the
humerus or upper arm, these three bones all fit together accurately to allow
ease of movement. The upper end of the ulna (trochlea - a half moon shaped bone)
has attached tendons, which act as a pulley. On the trochlea is a pointy bone
called the anconeal process (facing into the arm) when the elbow is extended,
the anconeal process fits into a notch at the lower end of the humerus called
the olecranon fossa. This is a typical tongue and groove construction collateral
(both sides) ligaments stabilize the elbow in order to make movements backward
and forward. As a puppy grows, the anconeal process should fuse (grow together)
to the ulna, if no fusion takes place (UAP) fractures of the growth plate can
occur, which in turn will lead to dysplasia. If the anconeal process does not
attach naturally to the ulna, then the elbow becomes unstable; this instability
results in bony changes known as osteochondrosis (OCD).
Any dog, any breed, can develop this condition, dysplasia is not exclusive to
just large breeds. The occurrence of dysplasia can be reduced through selective
breeding practices, by selecting only animals that have disease-free
radiographic examinations, and clear family histories of dysplasia free progeny.
Michele Scarberry, X-ray Technologist and GSD Breeder
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