TOTAL HIP REPLACEMENT
Q: What is canine total hip replacement (THR)?
A: Canine THR is a surgical procedure in which the arthritic hip joint surfaces are replaced with a new prosthetic ball and socket in the femur and acetabulum, respectively. The prosthesis is designed to fit precisely and mimics the anatomy of the original joint. The arthritic joint is pain-free after total hip replacement.
Q: Why has THR been recommended for my dog?
A: THR has been recommended for your dog to alleviate the pain and/or disability associated with hip pathology. Specific common indications include arthritis secondary to hip dysplasia, traumatic hip luxation that can not be maintained in place following reduction, fractures of the femoral head or neck that do not have a good prognosis following surgical repair, and developmental problems such as avascular necrosis of the femoral head that leads to arthritis. The goal in all cases is to provide a pain-free joint and to restore normal joint function.
Q: What is hip dysplasia?
A: Hip dysplasia is an abnormal development and growth of the hip joint. Both hips are usually affected but symptoms may be more severe on one side. The onset of clinical signs does not always occur in both hips simultaneously. Hip dysplasia is manifested by varying degrees of laxity (looseness) of the hip joint with instability and malformation of the joint components. Arthritis is the long-term consequence of hip joint laxity.
Q: What are the clinical signs of hip dysplasia?
A: The signs of hip dysplasia may be subtle. They can include the presence of lameness in one or both hind legs and the reluctance to climb stairs or jump. Dogs that are affected often become less active and less playful. They may be reluctant to go on walks and their gait may be a "bunny hop" at certain speeds.
Q: What does THR surgery entail?
A: A THR involves removing both the arthritic ball (femoral head) and socket (acetabulum) and replacing them with an artificial ball and socket joint.
The surgical procedure is precisely planned using several radiographic (X-ray) views and specialised templates that match the available implant sizes. Preoperative templating allows the surgeon to accurately determine the appropriate size femoral and acetabular implants to match the patient's femur (thigh bone) and acetabulum (socket in pelvis).
During surgery, the arthritic femoral head is removed, the arthritic acetabulum is prepared, and the acetabular component (socket) is implanted. Next, the femur is prepared, and the femoral component is implanted. The femoral head (ball) is placed on the femoral stem, and the new joint is articulated by placing the femoral head (ball) within the acetabulum (socket) to create the new prosthetic ball and socket joint.
The accompanying animation depicts total hip replacement in a dog. Key stages of the procedure are shown for both cemented and biologic (cementless) techniques; one or the other would be performed in a patient.
Q: What are the alternatives to THR?
A: For dogs with hip dysplasia, the alternatives to THR include medical management of the pain or a surgical salvage procedure called a femoral head ostectomy (FHO). Medical management of hip dysplasia can include any or all of the following: optimisation of body weight, administration of non-steroidal anti-inflammatory drugs, nutritional supplementation, implementation of a rehabilitation program (hydrotherapy is particularly useful), as well as any other method to manage pain. The FHO surgical procedure removes the femoral head and neck from the femur which severely alters the biomechanics of the hip joint.
Q: What are the benefits of THR over an FHO?
A: Pain relief following THR is more predictable than after FHO. Dogs with THR are expected to be pain-free for life. Research has shown objective evidence that dogs return to normal function in three to six months following THR. FHO is less predictable and the joint may remain painful. Dogs that have had successful THR surgery do not require long-term drug therapy. In addition to significant cost savings, this will eliminate the potential problem of long-term complications associated with chronic use of anti-inflammatory drugs.
Q: What are the risks of THR?
A: THR, like all surgeries, carries a low risk of anaesthetic and infection complications. Additional risks can include femur fracture and luxation of joint components. In rare instances, the sciatic nerve can be injured during the surgery. Sciatic nerve problems are usually transient and recovery occurs within a few weeks. If complications arise, they can usually be resolved successfully.
Q: Are there reasons why my dog shouldn't have THR?
A: THR is not performed on dogs with cancer or other major medical problems of higher priority for treatment. Dogs with lameness caused by problems other than hip pain including problems affecting the knee joint or spine must be carefully evaluated before THR is performed.
Q: How common are THRs in dogs?
A: The first THR in a dog was performed in 1957. BioMedtrix introduced the CFX® (Cemented Fixation) total hip system in 1990 and the BFX® (Biologic Fixation) in 2003. Since then, over 37,550 procedures have been performed using these implants. THR can be performed on dogs ranging from 1.5 kilograms up to 80 kilograms. THR can also be performed in cats.
Q: What is the success rate for canine THR procedures?
A: The success rate is very high. The majority of patients who receive a THR should be able to use the new hip for the rest of their life.
Q: How long will the implant last?
A: THR implants are expected to last a lifetime.
Q: How long will my dog be in the hospital following THR surgery?
A: Most veterinary surgeons hospitalise dogs for one to three days following surgery. In some rare instances, high-risk patients may be hospitalised for longer periods to provide additional assistance or to protect the stability of the new prosthetic joint.
Q: What is the typical recovery time for THR and what is involved?
A: Dogs often begin using their operated limb on the day of surgery. Most dogs use their operated leg quite well within a couple of weeks but activity is supervised and limited to leash walks for approximately six weeks after surgery.