Resource Library: Hip dysplasia
The hip joint in a dog is a ball (femoral head) and socket (acetabulum) joint. In normal animals the ball and socket are very tightly held in place with no laxity. Hip dysplasia is a disease that affects many breeds of dogs but is more common in larger breed dogs. Affected dogs have laxity (looseness) of the ball and socket joint. The condition has a strong hereditary component and the incidence can be effectively reduced through proper screening (radiographic evaluation) of breeding animals. Affected canine patients will have a variable degree of lameness of the rear legs depending on the severity of the condition. Moderate to severely affected patients will have a stilted/stiff rear limb gait, may "bunny hop" when running, have difficulty standing and shift their weight on to their front limbs. Diagnosis is usually straightforward. The clinical exam usually reveals a loss of muscle mass over the pelvic muscles, there is pain when extending the hips and their toes are scuffed in more severe and chronic cases. Joint manipulation may be painful and in severe cases; there may be palpable grinding (crepitus). Radiographs are diagnostic. In early cases there is laxity of the hip joints (the ball and socket joint is loose) with little to no visible arthritis. In more severe cases, there is also some degree of laxity but as the patient ages arthritis develops and can be easily identified on well-positioned radiographs.
Treatment options are dependent on age. If hip laxity is diagnosed before six months of age and is not severe, then juvenile pubic symphoidesis is a good option. The procedure slows down or closes the growth plate on the floor of the pelvis allowing the rest of the pelvis to turnout slightly as the patient grows allowing the acetabulum (socket) to cover the femoral head (ball). In order for the procedure to be effective it has to be performed early (before six months of age). Therefore, these puppies have to be identified early (at three to four months of age) by a good clinical exam and radiographs. The procedure is minimally invasive and the patients recover quickly. When done early and appropriately it is very effective and allows the patients to salvage their hip joints. In patients over six months of age with dysplastic hips and minimal arthritis a double or triple pelvic osteotomy on one or both sides of the pelvis is indicated. This procedure will allow the surgeon to rotate the acetabulum (socket) over the loose femoral head (ball) to "cover" the loose femoral head and improve joint contact. To achieve the hip rotation a special locking plate will allow changes of 20, 25 or 30 degrees depending on the amount of rotation needed. In order for the procedure to be effective, there has to be some degree (20 to 25 %) of femoral head coverage by the acetabulum present before surgery. If the femoral head and acetabulum are not in contact (the hip is subluxated), then the surgery will not be effective. It should be done no later than 12 to 14 months of age and only in patients with no evidence of arthritis. Dysplastic dogs with arthritis are not candidates for this procedure. In properly chosen patients the procedure is very effective in salvaging the hip joints. This allows the patient to keep the natural hip joints, which is the most functional state with the least complications.
In dogs with arthritic changes that are not responsive to medical therapy are candidates for either a total hip replacement (THR) or femoral head and neck excision (FHO). An FHO is a salvage procedure in which the femoral head and neck are surgically removed. This eliminates the contact between the diseased femoral head and acetabulum and the painful grinding. The procedure will allow the patient to move without pain. It does not restore function and in larger dogs and it will limit the level of activities they can be involved. Proper rehabilitation after surgery is very important. A THR is an excellent alternative for canine patients in an attempt to establish a pain free and very mobile limb. The procedure involves replacing the femoral head (ball) with a metal stem/ball implant and acetabulum (socket) with a metal cup lined with high density cross linked polyethylene to create a replacement joint much the same as it is in people. It can be performed on both joints. These patients have to be screened carefully for hip conformation, sized for proper implants, not be excessively luxated and have no evidence of skin, oral or urinary tract infections. Once healed a THR is a very durable and safe alternative for most dogs with arthritis due to hip dysplasia.
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