WHAT IS A TOTAL HIP REPLACEMENT (THR)? A THR is a prosthetic hip that is implanted in a similar fashion as is done in people.  It replaces the painful arthritic joint.  The modular prosthetic hip replacement system used today has three components – the femoral stem, the femoral head, and the acetabulum.  Each component has multiple available sizes which allow for a custom fit.  The components are made of cobalt chrome stainless steel and ultra high molecular weight polyethylene. Prosthesis implantation may be cemented or cementless (press-fit).

CFX Prosthesis 2010 copy
Cementless Prosthesis
Both cemented (shown on the left) and cementless (shown on the right) systems are available. Each system has advantages and disadvantages. Your dog will receive whichever is best depending on several factors including your dog’s age as well as the severity and duration of the arthritis present. Cemented components are held in place by the bone cement plus on-growth of bone once the prosthesis is in place. Cementless components are held in place by precise initial implantation plus bone in-growth into the surface of the implant. Cementless prosthesis implantation demands greater surgical precision. 
WHAT ARE THE COMPONENTS MADE OF? The cemented components are made of cobalt chrome stainless steel and ultra high molecular weight polyethylene. PMMA, or polymethylmethacralate, is bone cement used to hold the implants. A portion of the surface of the cementless implants is covered with 250 micron diameter titanium beads.

WHY CHOOSE A TOTAL HIP REPLACEMENT? A THR is performed to improve quality of life by providing pain relief, better hip function, and return to an active life.  The arthritic joint is replaced with the implant so the pain of bone rubbing on bone in the arthritic joint is gone.  Stability of the hip is returned.  The decreased range of motion of the arthritic joint is also corrected to allow good range of motion.
Micro Prosthesis 2010 copy
Your companion is a possible candidate for a THR if there is uncomplicated hip joint arthritis due to hip dysplasia or other causes.  Most are over 8 months of age (our oldest patient was 16 years old), and weigh more than 6 pounds.  (See “THR – Small Dogs/Cats”).  Other reasons for a THR include hip luxations, arthritis secondary to malunions, fractures and, rarely, some bone tumors.  A thorough examination to rule out other problems is a mandatory part of the preoperative examination.  Dogs and cats that have had femoral head and neck excisions (FHO) are usually not good candidates.

Dogs that have had femoral head ostectomy 
(FHO) are usually not candidates, although revision of an FHO to a THR is successful in some dogs. Most dogs are over 6 months of age (our oldest patient was 16 years old), and weigh more than 10 pounds (the largest is 180 pounds).

HOW DO PATIENTS FEEL WITH A TOTAL HIP REPLACEMENT? Most walk on their new hip immediately after surgery.  Most clients report the personality improves and that they feel great.  Gradual return to normal function is allowed between 6 to 10 weeks after surgery.  Long-term studies found THR to be a very effective method of treating disabling conditions of the canine hip.  The majority of dogs displayed marked improvement in walking, sitting, climbing stairs, standing, running, getting into the car, playing, and exercise following surgery.  THRs have been performed in both pet and working dogs with equal success.

DOES A TOTAL HIP REPLACEMENT 'WEAR OUT'? The life span of a THR in people is approximately 10 to 20 years.  Replacement of implants due to wear and tear has not been necessary in dogs partly because dogs weigh less than people, their weight is distributed on four rather than two legs, and their average life span is considerably shorter.

SHOULD BOTH HIPS RECEIVE A TOTAL HIP REPLACEMENT? Only one hip can be done at a time. The most painful hip should be replaced first. If pain is present on both sides, both sides should be replaced. The interval between surgeries is about 6 to 10 weeks.

WHAT DO DOGS AND CATS GO THROUGH TO GET A TOTAL HIP REPLACEMENT? The surgery takes 60-90 minutes.  They are under continuously monitored inhalation general anesthesia.  Vital parameters, such as heart rate, heart rhythm, tissue perfusion, blood oxygen content, respiratory rate and pattern, temperature and blood pressure are monitored.  The surgery is performed with extensive precautions to prevent infection.  Much attention is paid to preoperative preparation of the patient, instrument preparation, aseptic technique, and environment control in the operating room.  The patient’s leg is occasionally clipped and bathed a few days prior to surgery to ensure healthy skin.Pain medication is administered and maintained postoperatively as long as is needed.  The patient is hospitalized with 24-hour patient care.  The patients routinely support some weight on the leg immediately postoperatively.  They are generally released from the hospital on the second postoperative day – sometimes the next day.

WHAT IS THE AFTERCARE? The dog should remain inactive for 6 weeks postoperatively. They should be indoors, but walked outside on a leash to eliminate. Vigorous and strenuous activity is to be avoided during this time period. A good traction surface is helpful to prevent an accidental fall.

ARE THERE ANY RISKS? Yes.  The incidence of complications is very low, but risks exist just as they do for surgery in people.  Complications such as infection, luxation, neurapraxia, loosening, technical problems, and anesthesia incidents can never be totally eliminated.  Extreme precautions to minimize complications and anesthesia problems are taken by a surgery team with a combined experience in veterinary surgery of over 40 years.  Problems with this highly technical procedure are minimized by the frequent repetition of the same team of surgeons and scrub nurses using the most advanced instrumentation available. According to the implant manufacturer, Gulf Coast Veterinary Surgery is the leader in numbers of THRs being performed in the state of Texas and is among the leaders in the country.

WHEN SHOULD THE SURGERY BE PERFORMED? Surgery is recommended when pain or lameness is present. The hip will be painful when extended and/or abducted. Radiographs of the hips are used to confirm the diagnosis of osteoarthritis. A conservative approach using pain relievers for arthritis may be initially recommended. Surgery is recommended if medication is needed over an extended period of time or if it is ineffective. Long delays in performing surgery can lead to longer rehabilitation time. THR is ideally performed before severe bony remodeling and atrophy of hind leg muscles occurs. Additionally, a delay means less time for your dog to enjoy the improved pain free function provided by the hip replacement.

HOW DO WE GET STARTED? Schedule an appointment for a consultation and examination of your dog. If available, bring radiographs and copies of recent lab work performed by your veterinarian. A referral to Gulf Coast Veterinary Specialists from your veterinarian for an appointment is recommended. If your dog is a candidate, the surgery will be scheduled. We ask that you bathe the skin the day before surgery.  Radiographs of the hips will be taken if necessary on the consultation/examination day.
For more information on Hip Replacement Implants: BioMedtrix.com