The hip joint is made up of a ball at the top of the femur (femoral head), which articulates with a hemispherical socket (acetabulum) on the side of the pelvis. Dogs that develop hip dysplasia have a genetic predisposition to developing laxity in the attachments between the femoral head and acetabulum. This laxity allows the femoral head to move around excessively within the acetabulum causing abnormal development of the hip joint and ultimately inflammation (osteoarthritis) within the joint.
Many dogs with mild hip dysplasia will show no clinical signs. As the condition progresses, owners may notice varying degrees of lameness, reluctance to jump, a “bunny-hopping” gait when running, and atrophy of muscles in both hind limbs. Some dogs may cry out in pain upon movement of the hip.
Physical examination and radiographs are used to make a diagnosis of hip dysplasia. It is an inherited disease, and a lot of work has been done by the Orthopedic Foundation for Animals to help eliminate affected dogs from the breeding population.
Treatment of hip dysplasia can be conservative or surgical. The objectives of conservative therapy are to relieve pain and maintain limb function, allowing the dog to continue with as normal a level of activity as possible. Conservative therapy consists of weight control, moderate exercise, and medication. Medications used in the management of hip dysplasia include analgesics (pain relief medication) and neutriceuticals (nutritional supplements to aid cartilage healing). The decision to pursue medical management is typically based on the age of the dog, its intended use, the severity of the lameness, and its response to initial attempts at medical management. Many dogs can be managed successfully on a long term basis medically.
Currently, four surgical procedures are widely used in the treatment of hip dysplasia. These techniques can be divided into two groups: those that are completed prior to the development of significant osteoarthritis and those that are reserved for dogs with osteoarthritis.
Pubic symphysiodesis is a prophylactic procedure performed in very young dogs at risk for the development of hip dysplasia. As puppies grow their bones grow as well. Using a tool called electrocautery, the growth of one part of the pelvis is halted allowing other areas of the pelvis to grow, resulting in a more normal development of the hip joint.
In more mature puppies, a triple pelvic osteotomy (TPO) can be performed. In this procedure, each side of the pelvis is reshaped, moving the acetabulum to a more desirable position thus eliminating the laxity in the hip joint. The acetabulum is held in its new position with a specially designed bone plate.
Once significant osteoarthritis has developed, a total hip replacement or femoral head and neck excision can be performed. With a total hip replacement, the abnormal femoral head is replaced with a metal head and the acetabulum is replaced with a plastic socket. The discomfort that arose from an irregular femoral head rubbing against an irregular acetabulum is eliminated. In some cases, these implants are cemented in place (cemented hip replacement). In other cases, they are pressed into the remaining bone (uncemented hip replacement). Candidates for this procedure are medium and large breed dogs that are having clinical problems with arthritis in their hips.
In smaller dogs with osteoarthritis, a femoral head and neck excision can be performed. In this procedure, removing the femoral head eliminates the pain that arises from the abnormal femoral head rubbing against the shallow acetabulum.
Although many treatment options are available to help the patient with hip dysplasia, early diagnosis is critical in helping to decide the most appropriate treatment plan for each patient.