HIP DYSPLASIA

Hip dysplasia is one of the most common skeletal diseases seen in dogs. Gender does not seem to be a factor, but some breeds are more likely to have the genetic predisposition for hip dysplasia than other breeds.  

Hip dysplasia often begins while a dog is still young and physically immature. Early onset usually develops after four months of age. There are also cases of later onset, where hip dysplasia develops later due to osteoarthritis, a form of joint inflammation (arthritis) that is characterized by chronic deterioration, or degeneration of the joint cartilage.

Symptoms depend on the degree of joint looseness, the degree of joint inflammation, and the duration of the disease. 

  • Decreased activity
  • Difficulty rising
  • Reluctance to run, jump, or climb stairs
  • Intermittent or persistent hind-limb lameness, often worse after exercise
  • “Bunny-hopping,” or swaying gait
  • Narrow stance in the hind limbs (back legs unnaturally close together)
  • Pain in hip joints
  • Joint looseness
  • Grating detected with joint movement
  • Decreased range of motion in the hip joints
  • Loss of muscle mass in thigh muscles
  • Enlargement of shoulder muscles due to more weight being exerted on front legs as dog tries to avoid weight on its hips, leading to extra work for the shoulder muscles and subsequent enlargement of these muscles 

Influences on the development and progression of hip dysplasia are concurrent with both genetic and environmental factors: 

  • Genetic susceptibility for hip looseness or laxity
  • Rapid weight gain and obesity
  • Nutritional factors
  • Pelvic-muscle mass

Your vet will perform a complete physical exam on your dog, including a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis. Inflammation due to joint disease may be noted in the complete blood count. As part of surveying the physical symptoms and fluid work-ups, your veterinarian will also need a thorough history of your dog's health, onset of symptoms, and any possible incidents or injuries that may have contributed to your dog's symptoms. Any information you have on your dog's parentage will be helpful as well, as there may be a genetic link.

 X-rays are crucial for visualizing the signs of hip dysplasia. Some of the possible findings may be degenerative disease of the spinal cord, lumbar vertebral instability, bilateral stifle disease and other bone diseases.

Treatment of hip dysplasia can be conservative or surgical. The objectives of conservative therapy are to relieve pain and maintain limb function, as well as to continue the dog in as normal a level of activity as possible. Conservative therapy consists of weight control, moderate exercise, and analgesics (pain relief medication). The most important element will always be the maintenance of muscular support. Muscle is built by walking, jogging, and swimming. Acrobatics (playing frisbee, jumping, etc.) should be avoided as they place unnecessary pressure on the joint.

Another medical approach to the treatment of degenerative arthritis secondary to hip dysplasia involves the use of products called polysulfated glycosaminoglycans or PSGAGs. PSGAGs are naturally occurring components of the joint cartilage and increase joint fluid production.

When should a patient receive conservative management as opposed to specific surgical treatment? The answer depends on the age of the dog, the intended use of the dog, the degree of arthritis, the severity of the lameness, and the financial capability of the owner. Approximately 50-60% of the patients may respond to conservative therapy over a long period of time. The remaining 40-50% will require surgical treatment. Unfortunately, there is no way to predict into which category a dog will fall.

Three surgical procedures are currently used in the treatment of hip dysplasia. In young patients with minimal evidence of arthritis, a stabilizing reconstruction of the hip joint is recommended. This involves reconstructing the joint congruency and stopping the subluxation and laxity that lead to severe arthritis. This technique is called a triple pelvic osteotomy. It has been established as a reliable mode of treatment in cases which meet the case selection criteria.

Once the patient (usually adult) has radiographic evidence of degenerative arthritis, it is no longer a candidate for a triple pelvic osteotomy. Over time, many of these dogs will become less responsive to analgesic medications and surgical therapy should be considered. There are two procedures available.

1. Removal of the femoral head and neck (excision arthroplasty, femoral head ostectomy, FHO).
2. Total hip replacement.

Femoral head excision works well for dogs under thirty pounds and those with unilateral dysplasia. It is less satisfactory for dogs over fifty pounds, particularly when performed bilaterally. This is a salvage procedure for those owners who cannot afford the cost of a total hip replacement but need an alternative to constant medication and debilitating pain.

Introduced in 1976, the total hip replacement has become the only treatment available that provides normal hip joint function once advanced arthritis is present. With this technique, the femoral head and neck are replaced with a cobalt chrome or titanium component and the acetabulum is replaced with a plastic cup prosthesis. A five year followup study of 221 total hip replacements revealed an overall success rate of 91%. Total hip replacement can be done on both hips although many dogs (80-90%) do very well with one side replaced.

 

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