Fri, 04/16/2021 - 5:19pm

Casing the Joint

What you need to know about hip dysplasia


What is hip dysplasia?


Hip dysplasia is the abnormal development and growth of a dog’s hip joint. It usually occurs in large breeds, but it can be found in dogs of any breed and size, and even in cats. There is no single cause of hip dysplasia. Multiple factors, such as genetics, environment and nutrition, lead to the formation of deformed hip joints.

The hip joint can be described as a “ball in a socket” joint. During a puppy’s growth stage, both the “ball,” which is the head of the femur (or thighbone) and the socket in the pelvic bone (acetabulum) must grow at equal rates. The bony surfaces of the femoral head and acetabulum are covered by cartilage. The bones provide the necessary strength to support body weight, and the cartilage ensures a smooth fit and easy rotation when the hip moves.

With hip dysplasia, the growth of the ball and socket is uneven. This results in laxity, or looseness, of the joint. As the dog ages, degenerative joint disease, wearing away of the cartilage, muscle wasting and osteoarthritis develop. The extra bone that forms is the body’s attempt to stabilize the loose hip joint. When the cartilage is eroded, painful bone-to-bone contact occurs.

The deformity of the joint may get worse over time or stay the same. The degree of lameness exhibited depends upon the extent of the arthritic changes. A dog with mild changes may be quite painful, while a dog that has extensive changes in the joint may show no signs of pain.


How do dogs get hip dysplasia?


Hip dysplasia is considered an inherited genetic disease. Recent research suggests environment, nutrition, exercise, growth rate, muscle mass and hormones also play a role. In some breeds, early spaying or neutering, especially before the dog has reached the age of full developmental maturity, increases the chance the dog will develop hip dysplasia as compared to dogs that were sterilized after reaching adulthood.

Diet is another contributing factor. It is recommended that large, at-risk breeds be kept at a normal, lean weight during growth. Studies have shown puppies fed as much as they wanted to eat were more prone to developing hip dysplasia than puppies who were fed measured meals.

Other environmental influences include injury to the hip, ligament tear and overexertion on the hip joint at a young age, as well as repetitive motion on forming joints. An example would be jogging or roadworking a puppy under the age of one year. Any strenuous exercise, including treadmill work, should be postponed until the age that the growth plates of the bones have closed. In large breeds, this is usually between 14 and 18 months of age.

To what degree the cause of hip dysplasia is genetic and what portion is environmental is currently a topic of debate. All dogs considered for use in a breeding program should have their hips evaluated.


What are the symptoms of hip dysplasia?


Dogs affected with hip dysplasia can show signs as early as seven months of age, but most exhibit symptoms between one to two years. Weakness and pain are the usual signs. Some dogs will limp or be reluctant to climb stairs. Other signs are lameness after exercise and decreased thigh musculature. In order to avoid pain, a dog will try to reduce its movement of that hip. This may be visible as running with a narrow-based, “bunny-hopping” rear gait. There could be noticeable enlargement of the shoulder muscles as they compensate for the weakness in the rear legs.


How is hip dysplasia diagnosed?


Clinical signs and palpable looseness in the joints may indicate hip dysplasia. Radiographs of the hips, preferably under general anesthesia, is the best way to evaluate hip conformation in order to diagnose hip dysplasia. There are several standardized systems for categorizing hip dysplasia. The most widely used systems include Orthopedic Foundation for Animals (OFA), PennHIP and British Veterinary Association (BVA).

Radiographs can be sent to OFA for grading and certification by a panel of three board-certified veterinary radiologists. This system rates a dog’s hip joint on a seven-point scoring system. Normal hips are certified free of dysplasia and assigned a score of excellent, good or fair. Hips showing evidence of dysplasia are rated borderline, mild, moderate or severe and not certified. This procedure can be performed with or without anesthesia, depending upon the cooperation of the patient. Dogs must be two years of age to be certified.

PennHIP requires the dog to be anesthetized. Three X-rays are taken to measure the hip-joint laxity, or looseness. A score between 0-1 is assigned, with 0 being very tight hips and 1 being very loose. The score is based on a measurement of the hip’s distraction index (DI). The distraction index is an indication of the “percent out of joint” that the femoral head (ball) is displaced from the acetabulum (socket). For example, a DI of .15 means that the head of the femur is 15% out of joint.

A BVA panel of experts assess each hip joint and assign points based on nine aspects of the joint. The degree to which a dog is affected by hip dysplasia is represented by a score given to each hip. Scores for each hip are added together to get an overall hip score. Scores range from 0 to 106 (zero to 53 for each hip). A score of zero represents the least degree of hip dysplasia, while 53 indicates the most.

It is also common procedure to X-ray the spine and legs, as well as the hips, since other tissues can be affected by the extra strain of dysplastic hips. There may be other undetected factors such as neurologic issues and nerve damage involved.


What are the treatment options for hip dysplasia?


Many dogs with hip dysplasia can be managed with medical therapy. Conservative therapy does not cure the arthritis. The goal is to control the dog’s pain and lameness. Non-steroidal anti-inflammatory medications, such as carprofen (Rimadyl) and meloxicam (Metacam) have the dual action of reducing inflammation and relieving pain.

Physical therapy and low to moderate impact daily exercise will keep the muscles of the pelvic region strong and encourage healthy joint function. Acupuncture has been shown to help increase muscle strength and joint mobility, as well as decreasing pain.

Weight loss is important if your dog is overweight. Regardless of surgical or medical management, any dog afflicted with joint disease should be kept at ideal weight. I have been told that every extra five pounds carried is 40 additional pounds of pressure on the joints.

Cold laser treatment, massage and traditional Chinese medicine have all been used to treat hip dysplasia with varying results. Incorporating omega-3 fatty acids into the diet helps decrease the inflammation that occurs with osteoarthritis.

Joint supplements such as glucosamine-chondroitin products for high-risk breeds can be started as early as three months of age to ensure joint health and protect the cartilage of the joints. Vitamin C is another nutrient that contributes to the building blocks of collagen that can strengthen the joints. The use of pressure-reducing pet beds, ramps, stairs and steps help prevent further damage.

Many dysplastic dogs can be made comfortable with conservative treatment. However, arthritis, pain and lameness often worsen over time. At this point, surgery is recommended. Surgical procedures attempt to modify, replace or repair the hip joint in order to allow pain-free usage.

Femoral head ostectomy (FHO) is when the head of the femur is removed but not replaced. The resulting scar tissue from the operation takes the place of the hip joint. The false joint is less stable, with a reduced range of motion than a normal joint, but pain relief with adequate function is the result. This procedure can be done on dogs of all sizes, but is better suited for those weighing under 45 pounds.

Triple pelvic osteotomy (TPO) involves bone cuts in the pelvis so that the socket portion of the joint can be rotated over the ball. The bones are then stabilized with a bone plate. This procedure is best done on young dogs under 10 months of age. It is not recommended if osteoarthritis is already present.

Hip replacement has the highest rate of success, especially in severe cases. The faulty joint is completely replaced. If no other joint is affected, complete mobility is restored. It is ideal for older dogs with osteoarthritis that can no longer be managed with medication.

Juvenile pubic symphysiodesis (JPS) is a procedure for very young dogs that manipulates the way the pelvis grows to create a tighter hip. It involves cauterizing the growth plates of the pelvis to halt vertical growth. To compensate, the rest of the pelvis grows outward, in a manner which enhances the socket of the hip and provides better support than the dog would have had naturally. Since it relies on growth in puppyhood, it has a very small window for surgery, which is between four and five months old.

Capsular neurectomy is a procedure in which the hip joint capsule is de-nerved to reduce pain in the hip. This allows the dog to exercise moderately with less pain, keeps the leg muscles strong with use, and provides more support to the bad joint. Both hips can be done at the same surgery.

At this time, the best way to prevent hip dysplasia is by screening breeding stock before they are bred.



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