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Hip DysplasiaCanine hip Dysplasia (CHD)---the most common
orthopedic problem in dogs---is caused by a loose hipbone-thighbone connection.
It leads to hind-end pain and lameness that can range from mild to crippling. We
know CHD is genetically transmitted. But because multiple genes are involved,
scientists have yet to unravel the pattern of inheritance. Adding to the CHD
riddle is the complicated interplay between heredity and the environment. While
we know environmental factors (such as growth rate) influence whether CHD shows
up clinically during a dog's life, we still don't understand the exact nature of
the heredity-environment interaction. Although the disease disproportionately
affects larger-breed dogs, veterinarians have documented hip dysplasia in just
about every type of dog, including mixed breeds. The good news is that owners
and breeders can take preventive measures to reduce the odds of a dog developing
hip dysplasia. But if your dog does develop CHD, early detection and treatment
can help your friend live a long and relatively comfortable life. Loose Hips
Remember the lyrics, "The hipbone's
connected to the thighbone"? To picture the dog's hip joint, imagine a ball
fitting into a socket. The ball is the top (head) of the thighbone (femur),
which is coated with a smooth, low friction surface of cartilage. The femoral
head fits into the hip's socket (acetabulum). The entire ball-and-socket joint
is surrounded and supported by muscles, ligaments, and lubricating synovial
fluid. During the growth spurt from birth to 60 days,
the dysplastic puppy's muscle and connective tissue--unlike a normal pup's --
can't keep pace with the fast-growing bones. The resulting mechanical looseness
of the joint (hip laxity or subluxation) causes abnormal wear on the cartilage
that line the femoral head. As the bone-buffering cartilage deteriorates,
arthritis often sets in. "Arthritis is basically an abortive attempt by the
body to stabilize the joint by adding bone." explains Dr. Randy Boudrieau,
associate professor of surgery at Tufts University School of Veterinary
Medicine. Telltale Signs
Although pain and restricted range of motion
are universal signs of CHD, other indicators may vary, depending on the age of
the dog and the degree of arthritis present. In younger prearthritic dogs with
CHD, you may hear a "click" as the dog walks. (The femoral head is
"popping" in and out of the acetabulum.) Also, young dysplastic dogs
often move both back legs simultaneously in a "bunny hop" gait. On the
other hand, some younger dogs with radiographic (X-ray) evidence of CHD maintain
normal mobility and show signs of CHD only as they grow older and develop
arthritis. Older dogs suffering from CHD related
arthritis often rise stiffly after napping or limp after running. They may balk
at climbing stairs, jumping into the car, or (dare we say) hopping onto the bed.
But both older and younger dysplastic dogs seem to suffer the most discomfort in
cold, damp weather. Look and Listen
Although CHD may remain clinically
"hidden" in some dogs, early detection is crucial. But how do you
detect what is not obvious? A thorough physical examination is the first step.
Your veterinarian will observe your dog as it sits, stands, and walks to check
for characteristic CHD signs such as a side-to-side swinging gait, lameness, and
arched back (caused by shifting weight forward), or overdeveloped front-leg and
shoulder muscles. The veterinarian will next move the dog's hip
joint to assess its range of motion and check for pain with the joint extended.
The veterinarian will also listen for the "click" of the hip popping
out of joint and for the grating sound of bone on bone (crepitus) that indicates
cartilage loss. Finally, your veterinarian may radiograph the
hip joint to confirm subluxation or arthritic degeneration. He or she may send
the X-rays to the Orthopedic Foundation for Animals (OFA) or to PennHIP for
evaluation. The bottom line is if you discover dysplasia
early, you can take action to minimize discomfort. (It is important to point out
the veterinary surgeons perform some types of CHD surgery only on dogs that are
arthritis-free.) And, of course, knowing early on whether your dog has hip
dysplasia con help you make appropriate breeding decisions. Treating CHD
If all the evidence points to CHD, don't
despair. Various medical and surgical approaches can ease discomfort and restore
mobility. Medical treatments such as weight loss, moderate exercise, and
medication aim to alleviate pain and inflammation in and around the joint. But
if medical treatment fails to improve your dog's condition, orthopedic surgery
may be worth considering. Veterinary surgeons can repair, replace, or remove
some of the mechanical defects caused by dysplasia. Most veterinarians initially suggest a
three-pronged medical approach. First and foremost, try to help your dog lose
excess weight. "The heavier the animal, the greater the forces acting on
the joints," explains Dr. Boudrieau. Second, moderate your dog's activity. Taking
into account its physical condition and pain threshold, arrive at a happy
medium---somewhere between complete exercise restriction (inadvisable because it
adds to pain and stiffness) and unlimited physical activity. The owner must
determine an appropriate activity level and help the dog stick to it. Even with weight loss and controlled exercise,
though, many dogs with CHD have "bad days." To help dogs get through
flare-ups, veterinarians usually recommend a weight-based dose of
anti-inflammatory medication----usually buffered aspirin. (When giving your dog
anti inflammatory medication, restrict it from exercise.) But "a dog's
stomach is not quite as hardy as a person's," explains Dr. Boudrieau, so
avoid long-term aspirin use, which can cause vomiting and internal bleeding.
Because of potential toxicity and side--effects, veterinarians rarely prescribe
medications containing acetaminophen, ibuprofen, or corticosteroids for
dysplasia. Anecdotal reports suggest that injections of
glycosaminoglycan my help reduce joint inflammation in Dogs with CHD. This
substance seems to work by inhibiting the action of various destructive enzymes
in the joints. "I have some clients who swear by it, and others who say it
isn't effective," observes Dr. Boudrieau.
Surgical Options
If medical treatment doesn't sufficiently
relieve your dog's discomfort, your veterinarian my suggest surgery. Depending
on the dogs size, age, and arthritic condition, veterinarians usually recommend
one of several surgical procedures, all requiring general anesthesia. During a "hip-tightening" triple
pelvic osteotomy (TPO), the surgeon strategically snaps the dog's pelvis in
three places and repositions it with metal plates so the acetabulum covers the
femoral head more completely. Because this joint stabilizing procedure is
designed to thwart the development of arthritis, veterinarians usually perform
it on arthritis-free dogs aged 6 months to a year. Usually, veterinarians
operate separately on each side, about 4 to 6 weeks apart. (Young dogs typically
recover quickly.) Two less frequently performed hip-tightening surgeries--intertochanteric
varus osteotomy and femoral neck lengthening--modify the femur to improve the
ball-and -socket fit. Advances in prosteses (artificial devices used
to replace body parts) make total hip replacement (THR) and option for some
large, older dogs with CHD and severe arthritis. In THR, a polyethylene cup
replaces the acetabulum; a stainless-steel alloy ball replaces the femoral head.
Despite the elevated risk of infection associated with implantation, many dogs
return to full activity following THR. The vast majority of dogs that undergo
this procedure need only one hip replaced because the artificial joint picks up
the slack for the dysplastic one. THR, the most expensive CHD surgery, is
usually performed by an orthopedic specialists. Another surgical option is femoral head and
neck ostectomy. The goal of this procedure is to eliminate pain by removing the
head and neck of the femur. After surgery, the dog's muscles support what's left
of the femur, and a "false joint" composed of scar tissue develops.
While this procedure works well on dogs under 50 pounds, surgeons usually don't
perform it on dogs weighing more because their hip muscles can't effectively
support their weight without a true hip joint. Many primary-care veterinarians
can perform this operation, and it is less costly that total hip replacement. Hedging Your Bets Against CHD
Although genes play a big role in the
development of canine hip dysplasia (CHD), not everything about the disease is
hereditary. Evidence suggest that even dogs genetically predisposed to CHD can
escape its worst effects if breeders and owners control rapid growth and weight
gain during puppy hood--thus increasing the chance that muscles, connective
tissues, and hip joint bones will develop congruently. You can put the brakes on excessively rapid
growth by controlling what and how you feed young dogs. Studies show that
puppies fed a high-calorie diet grow faster that their litter mates on a
low-calorie diet. Research also shows that puppies that have constant (ad
libitum) access to food have more hip-joint laxity at 30 weeks and higher
incidence of hip dysplasia at 2 years than their counterparts consuming
25-percent less food on restricted feeding schedule. "Feeding a puppy a
controlled, balanced diet is probably the best way to manage its growth,"
advises Dr. Lisa Freeman, clinical instructor at Tufts University School of
Veterinary Medicine. Other so-called nutritional preventives and
remedies don't work to stop CHD--and in fact are potentially harmful. For
example, megadoses of vitamin C are not effective at preventing CHD, and
supplemental calcium can actually exacerbate the disease. You Can Help
Dogs with hip dysplasia benefit from
day-to-day help from their human friends. Comfortable bedding (eggcrate
foam-rubber pads work well), with a heating pad set to "low," often
helps. High-traction flooring also makes it easier for dysplastic dogs to walk
and rise form a sitting or prone position. Try to make it unnecessary for your
dog to climb stairs. (If stairs are unavoidable, help your dog by slinging a
towel under its abdomen to take some weight off its rear end.) Also, try gently
massaging the hip joint to increase blood supply to the area. You might even
want to investigate veterinary acupuncture, which sometimes relieves CHD pain. Although veterinary science is still searching
for definitive answers about how CHD develops, the diagnosis itself is not the
end of the world. Caring owners, working with their veterinarians, can usually
help dogs with unstable hipbone-thighbone connections cope in relative comfort.
And in the process, owners can enhance another important connection--their
relationship with their dog.
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