Hip Dysplasia is a malformation of the hip joint
which leads to degenerative joint disease and often times crippling
arthritis in dogs. While breeds of all sizes can get hip dysplasia,
large breed dogs are more prone to it.
Click here to see a more in depth presentation about this topic
Understanding Hip Dysplasia:
The hip is a ball and socket joint where the head
of the femur (thigh bone) is the ball and the acetabulum of the pelvis
forms the socket. In dysplastic dogs, the shape of the head of the
femur or the acetabulum or both are abnormal. As a result, the ball
cannot rotate smoothly in the socket. The head of the femur slips
partially out of the joint (sub-luxates) and bangs around in the
acetabulum which causes trauma to the joint and leads to arthritis. Hip
Dysplasia is an inherited trait. About 60% of the likelihood of
developing hip dysplasia is based on the genes of the parents. The other
40% is based on environmental factors such as growth rate, amount of
exercise during growth and trauma to the joint.
Diagnosing hip dysplasia can be done with a great
degree of certainty by 14 weeks of age using a special radiographic
technique called the Pennhip system. This procedure (developed at the
University of Pennsylvania) allows us to determine exactly how loose the
hip joint is by providing a view of the hips where we can measure how
far the femur can be pulled out of the acetabulum. These measurements
are calculated and a value known as the distractive index(DI)
is determined. This value is compared to the averages of the breed and
from that we can tell what the probability is that the pet will develop
hip dysplasia and whether or not they are acceptable for breeding. In
general, if the DI is greater than 0.45, the pet has over an 80%
probability of developing dysplasia. Because dysplasia is heritable, we
can select only pets with DI values that are better than the breed
average to breed. In doing so, we can eventually reduce and hopefully
eliminate dysplasia from that line of dogs.
This video explains a
comparison between PennHip and OFA Testing
Preventing the clinical symptoms of dysplasia:
Recently a minimally invasive technique known as
the Juvenile Pubic Symphysiodesis (JPS) surgery has been developed to
dramatically (80-90% reduction) reduce the chances that a pet at risk of
developing dysplasia will actually get the disease. This surgery is
performed on pets between 12 and 20 weeks and operates on the
principle that if we can close the growth plate between the left and
right halves of the pubis (the bones on the bottom of the pelvis), it
will force the acetabuli to move further out to the sides and cover the
femoral heads more effectively thus reducing the instability of the hip
joint.
How the JPS surgery works
The pelvis when viewed from a dog's rear end is a circular
The dark area at the bottom of the left drawing is the
growth center (growth plate) of the pubic bone of the pelvis
When the growth from this growth center (pubis) is
stopped, yet the remaining parts of the pelvis grow, the sockets of the
hips rotate over the ball of the hip (femoral head)
Take note of the lack of coverage (shading) of the ball of
the femur prior to surgery (below left) versus after the dog has
finished growing (below right)
The result is a stable hip that has much less chance of
developing significant arthritis
How do we select candidates for
JPS surgery
Hip dysplasia occurs more frequently in large breed
dogs, but almost all breeds do have it. Because this procedure is only
beneficial between the ages of 12 and 20 weeks of age, we recommend that
all pets should be evaluated for potential hip dysplasia at 14 weeks of
age using the Pennhip system. Pets with distractive index values above
0.45 should have JPS surgery and sterilization performed at 16 weeks of
age.
What happens during the surgery:
Your pet will be put under general anesthesia
A small incision is made between the hind limbs to expose
the pubic bone of the pelvis
The growth plate of the pubis is cauterized to destroy the
growing cells of this part of the pelvis
Your pet will stay over night and go home the next day
with pain medication and antibiotics to take for a few days.
An Elizabethan plastic collar will be dispensed to prevent
your pet from licking the wound.
Success of the JPS procedure:
The earlier the procedure is performed in the 12-20
week age bracket, the greater chance that it will prevent significant
development of arthritis of the hips. In general, there is a 90% chance
that your pet will benefit from this surgery if he/she is predisposed to
dysplasia based on a distractive index greater than .45
Potential complications
This is a very safe and minimally invasive
procedure when performed in young pets. Potential complications
include:
Failure of the pubic growth center to be successfully
ablated by the cauterization surgery, thus the pelvis grows as it would
naturally and the hip dysplasia progresses
Seroma (a serum pocket) formed at the surgical site
Infection is uncommon
In conclusion:
The Pennhip system allows us to reliably diagnose hip
dysplasia at an early age.
JPS surgery offers a minimally invasive and financially
affordable method for reducing arthritis resulting from hip dysplasia if
performed between 12 to 20 weeks of age.
