Hip dysplasia in the dog is a common orthopedic problem, which is influenced both by heredity and environmental influences such as exercise and diet. Most commonly, hip dysplasia affects large and giant breeds of dogs, although it may affect almost any breed.
The normal hip joint is a ball and socket joint in which the end of the femur (femoral head) forms the ball that fits into the socket (acetabulum) of the pelvic bone. Although almost all puppies have a normal hip configuration, at some point in the development of the hip joint in dogs with hip dysplasia, the configuration changes. Instead of being a close fitting round ball and deep socket, the ball becomes flattened and irregular and the socket becomes shallow. Since the ball can then easily shift out of the socket, with weight bearing on the leg, the femoral head rubs on the rim of the acetabulum causing discomfort and pain.
Some dogs will first show clinical signs at 4 - 6 months while in a rapid growth phase which is manifested as pain in the rear limbs, or hesitancy to rise in the rear, jump up on furniture, and climb stairs. This pain will sometimes diminish as the dog approaches 1-1/2 years of age and the dog may be sound for several years. The reason the dog becomes sound again is that with the constant grinding between the two bones forming the joint, the sensitive nerve endings are eventually worn away. Usually as the dog ages several years, advanced degenerative joint disease/arthritis develops and starts to interfere with the dog's normal range of motion thereby causing pain once again. Some dogs seem to skip the initial phase of this disease and don't have problems until later in life, and this probably represents a less severe manifestation of canine hip dysplasia.
Diagnosis of hip dysplasia consists of careful radiographic evaluation of the dog’s hip joint. Traditionally, this evaluation consisted of radiographic interpretation of the conformation of the hip joint at 2 years of age or greater. Another method has been developed for the early diagnosis of hip dysplasia. This newer, PennHIP method was developed at the University of Pennsylvania School of Veterinary Medicine and is based on the measurement of the passive laxity or looseness of the ball in the socket. Radiographic measurement of the hip laxity in dogs as young as 4 months old has shown a high correlation to the development of degenerative joint disease later in life. The more laxity in the hips, the more likely that the dog will develop problems.
There are several medical and surgical options for treatment of canine hip dysplasia. The choice is dependent upon the age of the dog, severity of disease, presence or absence of arthritis, and economic considerations. Medical treatment is geared toward relief of pain and inflammation. This option is generally accomplished by use of nonsteroidal anti-inflammatory drugs, along with rest. Medical treatment works well initially for many animals, but often reaches an endpoint where there is little benefit, as the dog gets older. Surgically, the options are geared toward either pain relief or maintaining or creating a normal hip configuration. These options will be discussed as follows:
Femoral Head and Neck Ostectomy
This procedure removes the entire ball of the joint and is aimed at relieving pain by disallowing the abnormal grinding of the bone to bone contact. This procedure works very well in many dogs by allowing a false joint to form between the top of the femur and the surrounding musculature. Although some shortening of the limb occurs, in a four-legged animal such as the dog, the difference is negligible. One or both hind legs may be done depending on the severity of the dysplasia
Triple Pelvic Osteotom
This procedure is aimed at trying to restore the hip joint to a more normal conformation. Since the problem with hip dysplasia is the grinding of the acetabular rim over the head of the femur, the triple pelvic ostectomy was developed. The pelvis is cut in three places so that the acetabulum can be rotated over the head of the femur for better coverage and elimination of the rubbing. Again one or both sides may be done in staged surgeries. The maximum benefit from this procedure is attained when done in young dogs 8 months to 1 year old and is of little benefit after signs of degenerative joint disease develop.
Total Hip Replacement
As the name implies, the procedure consists of replacing both the acetabular and femoral head components of the hip joint. The advantage of this procedure is in replacement of normal hip conformation. In 80% of the cases replacement of only one hip is necessary.