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Canine 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.

1. NORMAL HIP JOINT: The founded femoral head fits snugly into the acetabulum 2. MODERATE DYSPLASIA: The femoral head flattens, the femoral neck thickens, and the joint becomes loose and unstable. 3. SEVERE DYSPLASIA: The femoral head and acetabulum are riddled with arthritic degeneration. The femoral head is almost totaly dislocated. 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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