HIP DYSPLASIA
(by Dr Jason Smith 2005)
Hip dysplasia is defined as a deformity of the coxofemoral (hip) joint that occurs during the growth period. Hip dysplasia is caused by a variety of factors including genetic, obesity in the young puppy and excessive exercise, all of which contribute to a poorly fitting hip joint. As the dog walks on this joint, arthritis eventually develops, causing pain in the joint. The degree of lameness that occurs is usually dependent upon the extent of arthritic changes in the hip joint.
Most breeds of dogs can be affected with hip dysplasia although it is predominantly seen in the larger breeds of dogs, such as the German Shepherd, St. Bernard, Labrador Retriever, Old English Sheepdogs, etc.
The typical clinical signs of hip dysplasia are weakness and pain in the hind legs, lack of co-ordination, and a reluctance to rise. Wasting of the large muscle groups in the hind legs may eventually develop. Most owners report that the dog has had difficulty in rising from a lying position for a period of weeks or months; lameness and pain subsequently develop. Again, the severity of signs and progression of the disease usually correlate with the extent of the arthritis in the joint. Clinical signs can occur as early as 4-6 weeks of age, but most dogs manifest the disease as a lameness around one to two years of age. Dogs with mild hip dysplasia and minimal arthritis may not become painful and lame until 6-10 years of age.
Tentative diagnosis of hip dysplasia is made on the basis of history, breed, and clinical signs. Radiographs are normally performed after 12 months of age and sent to a registered veterinary radiology specialist to be hip scored. A new technique of positioning for radiographs called Penn-Hip can be performed from an earlier age by a registered Veterinary surgeon at Murdoch University Veterinary Hospital. The advantages of the new technique is that newer corrective surgical procedures can be performed at an earlier age.
Treatment of hip dysplasia may involve the use of drugs or surgery, or both. The options are as follows:
l. Anti-inflammatory drugs:
Several drugs will give relief from pain. Early in the course of the disease drugs which protect the cartilage lining of joints may be effective in limiting pain. Also non-steroidal anti-inflammatory drugs (NSAIDs) may work well in some dogs. In others, corticosteroids are used. Most drugs have some side-effects and therefore the most suitable drug for your pet may require close co-operation between you and your veterinary surgeon. Unfortunately, it is not possible to predict which dog will respond to which drug. Therefore, a series of trials may be needed to find the most effective one for your dog.
2. Surgery:
There are four main procedures:
A) Pectineal Myotomy (muscle cutting surgery),
B) Femoral Head Ostectomy/Excision (ball removal),
C) Triple Pelvic Osteotomy, and
D) Total Hip Replacement.
A) Pectineal Myotomy is a relatively minor procedure that involves cutting a small muscle that puts pressure on the hip joint. It results in no loss of leg function and gives good to excellent relief in 80-90% of dogs. If both hips are abnormal, both hips may be operated at the same time. The dog recovers from surgery in one to two days. However, this procedure does not stabilise the hip joint or prevent progression of arthritic changes. Within a few months to several years, pain and lameness will return.
B) Femoral Head Ostectomy (FHO) or excision is another choice. The hip joint is a ball and socket joint. FHO is the removal of the ball part of the joint. This gives excellent results in small dogs because a functional "false joint" forms. However, some large dogs may not form this "false joint" very well. This procedure is usually used in large dogs if arthritis is very severe, if the hip dislocates, or if the expense of the other procedures is prohibitive.
C) Triple Pelvic Osteotomy is a procedure in which the pelvis is cut in three places around the hip joint. The bone is rotated to create better alignment with the femoral head (the ball). It is reattached so that the joint functions in a more normal fashion without looseness and pain. This should only be performed in a dog with no arthritic changes in the joint and is generally reserved for younger patients under 12months of age.
D) Total Hip Replacement (THR) is possible, as is done in humans. The hip joint is replaced with an artificial ball and socket often made of plastic and stainless steel attached to the pelvis and femur in place of the abnormal joint. It is another expensive procedure, but it may give many years of pain-free use of the hips. Although the intent is for the transplant to be permanent, the new joint may loosen after a period of time.
I am considering breeding my dog. Can anything be done to prevent hip dysplasia in the puppies?
Research has shown that the cause of hip dysplasia is related to a combination of genetic and environmental factors. The disease is known to be an inherited condition and the genetics of hip dysplasia are extremely complicated. In addition, environmental factors such as overfeeding
and excessive exercise can predispose a dog (especially growing puppies) to developing hip dysplasia. Because the inheritance of the disease is so complicated, many questions remain regarding eradication of the disease.
