Total Hip Replacement

Introduction

A total hip replacement is generally performed in larger dogs with severe degenerative joint disease (DJD). Canine hip dysplasia is the most common reason for the degeneration of the hip joint, however other causes such as trauma may result in severe DJD and the need for joint replacement.

Canine hip dysplasia is a condition which begins in immature dogs with instability or laxity of the hip joints. The incidence of hip dysplasia is greatest in large breed dogs. Typically there are two populations of dogs which will demonstrate signs of lameness associated with hip dysplasia. First are the younger patients (those between 5 to 10 months of age) that are still growing and developing. Often times the laxity of the hip joint is responsible for early clinical signs and joint changes. Second are the older patients that have reached skeletal maturity but have now developed secondary changes. These changes often lead to osteoarthritis or simply arthritis of the hips joints.

Symptoms

Signs and symptoms commonly observed as a result of the changes within the joint are often observed as lameness involving one or both rear limbs, a shifting or swaying gait in the rear limbs, slowness when rising, reluctance to jump or climb, shifting the weight to the forelimbs, loss of muscle mass on the rear limbs, and pain when the hips are manipulated. Dogs may show clinical signs at any age or stage of development of the disease. As the osteoarthritis progresses with age, some dogs may show clinical signs similar to people with arthritis such as lameness after unaccustomed exercise, lameness after prolonged confinement, and worsening of problems if they are overweight.

Treatment

Occasionally, severely affected joints may become so painful that surgical options should be considered. Surgical options for canine hip dysplasia include such surgeries as: juvenile pubic symphysiodesis (JPS), triple pelvic osteotomy (TPO), femoral head and neck excision arthroplasy (FHO), and total hip replacement or total hip arthroplasty (THA). All of these surgeries are potential options for dogs with canine hip dysplasia and are based upon an individual's age, clinical signs, radiographic changes, size, body condition, conformation, as well as several other factors.

Surgical replacement of arthritic joints (total joint replacement) was first developed for dogs with osteoarthritis or other diseases of the hip. Total hip replacement surgery has been available for dogs for over 30 years. The design and materials of the implants have closely paralleled those used for hip replacement in human beings.

Typically, the replacement consists of a medical grade plastic (ultrahigh molecular weight polyethylene) cup for replacement of the cup portion of the joint or acetabulum and a metal (chrome cobalt) ball and stem for replacement of the femoral (thigh bone) aspect of the hip joint. The cup and stem implants have traditionally been held in place within the bone by use of bone cement. More recent technology now allows the implant to be maintained securely within the bone by allowing bone to grow directly into the implant. There are advantages and disadvantages to both techniques but either method works very well when performed by an experienced veterinary surgeon.

Considerations and Prognosis

Careful attention to detail by the surgeon and diligent care after the surgery by the owner usually results in an artificial hip that lasts the rest of the dog's life and allows unlimited, pain-free function, including running and jumping.

Finally, one of the most significant considerations with total hip replacement surgery is the cost and potential for complications. Approximately 90% of patients undergoing total hip replacement surgery recovery quickly with a low likelihood for complications. Potential complications associated with the surgery include infection (1-2%), implant loosening (2-4% this may be in fact lower for cementless implants), and fracture or dislocation of the implants (3-4%). For patients with complications, there is almost always a method of revision to allow for continued improvement and return to function.

When considering these factors, for those clients with large breed dogs that are afflicted by canine hip dysplasia enough so that the dogs' quality of life is severely impacted, a surgical option such as total hip replacement may be an extremely viable option to provide restoration of comfort, mobility, and function for that animal.

After total hip replacement, most patients feel comfortable enough to use the leg because the prostheses are well stabilized regardless of type (cement or cementless).  Due to the removal of the once painful components of the diseased joint, many dogs will quickly become too active and must be confined to a kennel, crate, or small area with activity restricted to leash walking with abdominal sling support for elimination purposes only.