Total Hip Replacement
Nancy O. Brown, VMD, DACVS, DACVIM-Oncology Stephanie Dobbins, DVM
The first total hip replacement performed at Pennsylvania Veterinary Specialty and Emergency Associates at Hickory Veterinary Hospital was in January of 1997. Since then there has been a great deal of advancement in the procedure. A total hip replacement is the best treatment for hip dysplasia with clinical signs that are not responsive to conservative, medical management. Approximately 90% of patients have excellent outcome. Most dogs walk on their new hips immediately post-operatively. Most owners report their dog’s personality improves.
Hip dysplasia is the abnormal development and growth of the hip joint. Both hips are usually affected but only one hip may show clinical signs. Hip dysplasia is manifested by varying degrees of laxity or looseness of the muscle and ligament around the joint with instability and malformation of the joint components. Signs of hip dysplasia are stiffness in the morning, not wanting to stand, wanting to sit during eating, reluctance to go up stairs or jump into the car, change in stride, short choppy gait, exercise intolerance, not wanting to exercise as long or as vigorously, or the pet may just seem “inactive”. Medical or conservative management of hip dysplasia is usually recommended before surgery. This includes management of the pet’s body weight, nutritional supplementation, moderate exercise, physical therapy, and medications. A thorough examination is mandatory to rule out any other problems.
When medical management of hip dysplasia no longer maintains “quality of life” and function, a total hip is a great alternative. The goal of a total hip replacement is to provide pain relief, better hip function, and return the dog to an active life. It should improve the quality of the pet’s life by improvements in walking, sitting, climbing stairs, standing, running, getting into the car, playing and working if required. The pain of bone rubbing on bone in an arthritic joint is removed. The hip joint is stabilized and the range of motion of the joint is increased. Although trying medical management is encouraged a long delay in performing surgery can lead to a longer rehabilitation time. A total hip replacement is ideally performed before severe boney remodeling and atrophy of the hind leg muscle occurs. If a total hip is not affordable the alternative is a femoral head and neck excision. In this surgery the ball of the ball and socket joint is removed. The hip functions by the leg being supported by the gluteal muscles.
A total hip procedure is designed to eliminate the source of discomfort by replacing the arthritic hip joint with an artificial joint. The dog's femoral head and neck are removed and replaced with a metal implant made of cobalt chrome stainless steel and titanium. The socket is removed and replaced with a polyethylene cup. Both components fit together to form a new ball and socket joint which is a pain free and anatomically correct joint. Pennsylvania Veterinary Hospital and Emergency Associates at Hickory Veterinary Hospital uses noncemented, cemented, and hybrid total hip implants. This allows us to take advantage of the benefits of each system. Although hip dysplasia is usually bilateral only one hip is necessary in 70-80% of the pets.
Postoperatively the pet spends one to two nights in the hospital. They need to return for an appointment two weeks later for a suture or staple removal. Eight weeks of “inactivity” is necessary. All exercise needs to be controlled, and restricted to gradually increasing leash walks only.The pet should be confined to a small room with traction, “rough, flat” surface. Running and jumping is not allowed. The pet will go home with approximately ten days of prophylactic antibiotics and pain medication. Radiographs are needed 4 weeks, 12 weeks, and 1 year postoperatively. Hip radiographs are recommended yearly after that.
A success rate of 85-95% is expected. Every surgery has some risk associated with it. Every possible measure is taken to minimize the risk of complications from total hip replacement surgery. The risk of complication is approximately 8% of the cases. Possible complications include hip luxation, infection, bone fracture, subsidence, and aseptic loosening. Luxation is the most common complication. It occurs in 2-4% of cases. Diligent post operative exercise restriction helps reduce this risk. Rarely is this condition not resolvable. The most serious complication is infection. This is more common with the cemented implant. If an implant gets infected, the entire implant needs to be removed. The pet ends up with a femoral head and neck excision. This occurs in 1-2% of cases. Fractures are more common with cementless implants and are usually repairable. Subsidence is when the femoral implant slides down inside the bone. This occurs only with cementless implants. In some cases this is not necessary to treat, but in others the femoral implant is modified or changed. Aseptic loosening means loosening without infection. This can occur with either the stem or cup. When a total hip replacement is placed it is expected to last the life time of the pet.