HIP DYSPLASIA

What is hip dysplasia?

What are the symptoms of hip dysplasia?

Dogs of all ages are subject to hip dysplasia and the resultant osteoarthritis. In severe cases, puppies as young as five months will begin to show pain and discomfort during and after exercise. The condition will worsen until even normal daily activities are painful. Without intervention, these dogs may eventually be unable to walk. In most cases, however, the symptoms do not begin to show until the middle or later years in the dog's life.

The symptoms are similar to those seen with other causes of arthritis in the hip. Dogs often walk or run with an altered gait. They may resist movements that require full extension or flexion of the rear legs. Many times, they run with a 'bunny hopping' gait. They will show stiffness and pain in the rear legs after exercise or first thing in the morning. They may also have difficulty climbing stairs. In milder cases dogs will warm-up out of the stiffness with movement and exercise. Some dogs will limp and many will become less willing to participate in normal daily activities. Many owners attribute the changes to normal aging but after treatment is initiated, they are surprised to see a more normal and pain-free gait return. As the condition progresses, most dogs will lose muscle tone and may even need assistance in getting up.

Who gets hip dysplasia?

Hip dysplasia can be found in dogs, cats, and humans, but for this article we are concentrating only on dogs. In dogs, it is primarily a disease of large and giant breeds. German Shepherds, Labrador Retrievers, Rottweilers, Great Danes, Golden Retrievers, and Saint Bernards appear to have a higher incidence, however, these are all very popular breeds and may be over represented because of their popularity. On the other hand, sighthounds such as the Greyhound or the Borzoi have a very low incidence of the disease. This disease can occur in medium-sized breeds and rarely in small breeds. It is primarily a disease of purebreds although it can happen in mixed breeds, particularly if it is a cross of two dogs that are prone to developing the disease.

What are the risk factors for the development of hip dysplasia?

Hip dysplasia is caused by a subluxation in the hip joint. This creates abnormal wear and erosion of the joint and as a result arthritis and pain develop. The disease process is fairly straightforward; the controversy starts when we try to determine what predisposes animals to contracting the disease.

Nutrition: It appears that the amount of calories a dog consumes and when in the dog's life those calories are consumed have the biggest impact on whether or not a dog genetically prone to hip dysplasia will develop the disease.

Experimentally, it has been shown that obesity can increase the severity of the disease in genetically susceptible animals. It stands to reason that carrying around extra weight will exacerbate the degeneration of the joints in a dog; including the hip. Dogs that may have been born genetically prone to hip dysplasia and are overweight are therefore at a much higher risk of developing hip dysplasia and eventually osteoarthritis.

Another factor that may increase the incidence of hip dysplasia is rapid growth in puppies during the ages from three to ten months. Experimentally, the incidence has been increased in genetically susceptible dogs when they are given free choice food. In one study, Labrador Retriever puppies fed free choice for three years had a much higher incidence of hip dysplasia than their littermates who were fed the same diet but in an amount that was 25% less than that fed to the free-choice group.

Feeding a diet that has too much or too little calcium or other minerals can also have a detrimental effect on the development of the hip joint. However, with today's complete and balanced dog foods this has become a rare occurrence. The practice of feeding home-made dog foods is popular with some dog owners. These diets must be carefully monitored for proper nutritional balance; not only for calcium and the other essential minerals but for all nutrients.

Exercise: Exercise may be another risk factor. It appears that dogs that are genetically susceptible to the disease may have an increased incidence of disease if they over-exercised at a young age. But at the same time, we know that dogs with large and prominent leg muscle mass are less likely to contract the disease than dogs with small muscle mass. So, exercising and maintaining good muscle mass may actually decrease the incidence of the disease. Moderate exercise that strengthens the gluteal muscles, such as running and swimming, is probably a good idea. Whereas, activities that apply a lot of force to the joint are contraindicated. An example would be jumping activities such as playing Frisbee.

How is hip dysplasia diagnosed?

The diagnosis of canine hip dysplasia is typically made by combining: clinical signs of arthritis and pain, a complete physical exam, and radiographs (x-rays). If a dog is showing outward signs of arthritis, there are usually easily recognized changes in the joint that can be seen on radiographs. In addition, the veterinarian may even be able to feel looseness in the joint or may be able to elicit pain through extension and flexion of the rear leg. Regardless, the results are straightforward and usually not difficult to interpret.

However, about half of the animals that come in for a determination on the health of their hip joints are not showing physical signs, but are intended to be used for breeding. The breeder wants to ensure that the animal is not at great risk for transmitting the disease to his or her offspring. There are two different testing methods that can be performed. The traditional is OFA testing. The other relatively newer technique is the PennHip method.

OFA: The method used by the Orthopedic Foundation for Animals (OFA) has been the standard for many years. The OFA was established in 1966, and has become the world's largest all-breed registry. The OFA maintains a database of hip evaluations for hundreds of thousands of dogs. Radiographs are taken by a local veterinarian using specific guidelines and are then submitted to the OFA for evaluation and certification of the dog's hip status. Since the accuracy of radiological diagnosis of hip dysplasia using the OFA technique increases after 24 months of age, the OFA requires that the dog be at least two years of age at the time the radiographs are taken. Because some female dogs experience additional hip subluxation when they are in heat, pregnant or nursing the OFA recommends that the evaluation should not be performed during these times.

To get the correct presentation and ensure that the muscles are relaxed, the OFA recommends that the dog be anesthetized for the radiographs. OFA radiologists evaluate the hip joints for congruity, subluxation, the condition of the acetabulum, and the size, shape, and architecture of the femoral head and femoral neck. The radiographs are reviewed by three radiologists and a consensus score is assigned based on the animal's hip conformation relative to other individuals of the same breed and age. The OFA then places the evaluated dogs into one of seven categories. Normal hips are graded as: excellent, good or fair. If the consensus is unclear the dog is graded as borderline dysplastic. And dogs with obvious radiographic signs of hip dysplasia are graded as: mild, moderate, severely dysplastic. Dogs with hips scored as borderline or dysplastic (mild, moderate, severe) are not eligible to receive OFA breeding numbers.

The OFA will also provide preliminary evaluations (performed by one OFA radiologist) of dogs younger than 24 months of age to help breeders choose breeding stock. Reliability of the preliminary evaluation is between 70 and 100% depending on the breed.

How is hip dysplasia treated surgically?

There are several surgical procedures available to treat hip dysplasia depending on the dog's age, body size, and the severity of the hip joint's degeneration.

Triple Pelvic Osteotomy (TPO): TPO is a procedure used in young dogs usually less than 10 months of age that have radiographs that show severe hip laxity, but have not developed damage to the joints. The procedure involves surgically breaking the pelvic bones and realigning the femoral head and acetabulum restoring the weight-bearing surface area and correcting femoral head subluxation. This is a major surgery and is expensive, but the surgery has been very successful on animals that meet the requirements.

Juvenile Pubic Symphysiodesis: A less invasive surgery for treating hip dysplasia is called Juvenile Pubic Symphysiodesis. This surgery prematurely fuses two pelvic bones together, allowing the other pelvic bones to develop normally. This changes the angle of the hips and improves the articulation of this joint, lessening the likelihood of osteoarthritis. Early diagnosis is critical, since the procedure must be done before 20 weeks of age, preferably 16 weeks, and before any signs of arthritis are evident.

Total Hip Replacement: This may be the best surgical option for dogs that have degenerative joint disease as a result of chronic hip dysplasia. Total hip replacement is a procedure that can produce a functionally normal joint, eliminate degenerative changes, and alleviate joint pain. The procedure involves the removal of the existing joint and replacing it with an artificial joint or prosthesis. To be a candidate for this procedure, the animal must be skeletally mature. With the new micro-prosthetics there is no minimum size limit. In addition, there is no maximum size limit. If both hips need to be replaced, there is a three-month period of rest recommended between the surgeries. As with the TPO surgery, this is an expensive procedure but it produces very good results. Most dogs return to a near normal level of activity without pain.

Femoral Head and Neck Excision: Femoral head and neck excision is a procedure in which the head of the femur is surgically removed and a fibrous pseudo-joint replaces the hip. This procedure is considered a salvage procedure and is used in cases where degenerative joint disease has occurred and total hip replacement is not feasible or if the expense of a total hip replacement is prohibitive. The resulting pseudo-joint will, in most cases, be free from pain and allow the animal to increase his activity, however, full range of motion and joint stability are decreased. For best results, the patient should weigh less than 40 pounds; however, the procedure may be performed on larger dogs.

How is hip dysplasia treated medically?

Medical management of hip dysplasia and osteoarthritis has greatly improved thanks to the introduction and approval of several new drugs. Because hip dysplasia is primarily an inherited condition, there are no products on the market that prevent its development. Through proper diet, exercise, supplements, anti-inflammatories, and pain relief, you may be able to decrease the progression of degenerative joint disease, but the looseness in the joint or bony changes will not change significantly.

Because of the high cost involved with corrective surgeries, medical management is many times the only realistic option for pet owners. Medical management is multifaceted. For the best results, several of the following modalities should be instituted.

Weight Management: Helping a dog maintain his recommended weight may be the single most important thing owner scan do for their pets. Surgical procedures and medical therapies will be far more successful if the animal is not overweight. You, as the owner, have control over what your dog eats. If you feed a quality food in an amount appropriate for your dog's size, breed and activity level and keep treats to a minimum, your dog should be able to maintain an ideal weight. Considering that more than half of the pets in the U.S. are overweight, there is a fair chance that many of the dogs with hip dysplasia/osteoarthritis are also overweight. If your dog is overweight, seek the advice of your veterinarian concerning a lower calorie dog food and an exercise program.

Exercise: Exercise is equally important in losing and/or maintaining the appropriate weight. Exercise that provides good range of motion and muscle building as well as limiting wear and tear on the joints is best. Leash walks, swimming, walking on treadmills, and slow jogging are excellent low-impact exercises. Bear in mind that an exercise program needs to be individualized for each dog based on the severity of the osteoarthritis, his weight, age, and physical condition. In general, too little exercise can be more detrimental than too much, however the wrong type of exercise can actually cause harm. While playing Frisbee can be very enjoyable and fun for the dog, it is extremely hard on his joints.

Remember, it is important to exercise daily; only exercising on weekends, for example, may cause more harm than good. Regular exercise in shorter sessions is always better than long work-outs on weekends. Warming the muscles prior to exercise and following exercise with a "warm-down" period are beneficial. Consult with your veterinarian regarding an exercise program appropriate for your dog.

Warmth and good sleeping areas: Most people with arthritis find that the symptoms tend to worsen in cold, damp weather. Keeping your pet warm, may help him be more comfortable. A pet sweater will help keep joints warmer. In addition, you may want to consider keeping the temperature in your home a little warmer.

Providing an orthopedic foam bed helps many dogs with arthritis. Beds with dome-shaped, orthopedic foam distribute weight evenly and reduce pressure on joints. They are also much easier for the pet to get out of. Place the bed in a warm spot away from drafts.

Massage and physical therapy: Your veterinarian or the veterinary staff can show you how to perform physical therapy and massage on your dog to help relax stiff muscles and promote a good range of motion in the joints. Remember, your dog is in pain, so start slowly and build trust. Begin by petting the area and work up to gently kneading the muscles around the joint with your fingertips using small, circular motions. Gradually work your way out to the surrounding muscles. Moist heat may also be beneficial.