Total Hip Replacement

Overview:

Total hip replacement is a surgical procedure which reliably restores comfort and near normal function to dogs with a variety of painful hip conditions. Advantages include relatively quick recovery, predictable results, and options if complications are encountered. Disadvantages are cost, and need for extended exercise restriction.

Indications:
The most common condition for which total hip replacement is indicated is osteoarthritis that results from hip dysplasia.  Other indications include recurrent luxation (dislocation of the hip) and femoral head and neck fracture, either acute that is not amenable to repair, or chronic that has healed but remodeled such that discomfort results.

Some hips are so remodeled and malformed that sufficient bone stock does not remain to support the total hip implants, but this is rare. Radiographic severity does not always correlate to clinical discomfort. Some dogs have relatively mild radiographic signs but are severely impaired, and vice versa. Radiographs can tell us why a dog is painful or lame, but the decision for surgery is based on a pet’s clinical lameness and quality of life.

Age is rarely a limiting factor.  Hip replacement can be considered for dogs as young as 6 months, though most dogs are at least 10 months of age when the procedure is needed, and average 2-8 years. There is no upper age limit, but concurrent disease in older dogs such as neoplasia, degenerative myelopathy, lumbosacral disease, renal or cardiac deficiency may significantly reduce prognosis.

Body size also does not limit application. The modular hip systems currently in use offer implants small enough for toy breed dogs and cats, and large enough for 200+lb dogs. We have successfully replaced hips in patients from Yorkies to Mastiffs, though typical patients are over 45lb.

Muscle atrophy can prolong recovery and alter implant size selection, but does not preclude the procedure.

Implants:

Hip replacements have been done in dogs since the 1950’s and until the early 2000’s most implants were stabilized with bone cement (PMMA). In parallel with human implants, there was a shift towards uncemented systems when bone cement was found to result in implant loosening later in a patient’s life.  We implant hips with cement in geriatric patients, but most are now uncemented with long term stability achieved with osteointegration, meaning that bone grows into the implant.  The prosthetic is designed for this to happen with a porous metallic coat and manufactured interstices in the implant surface.

The two most common implant systems used in veterinary medicine are KYON and Biomedtrix. Both are completely uncemented systems and both are used at the DVSC, but by far the majority is KYON. The choice is primarily surgeon’s preference, but there are a small number of cases that may be more appropriately treated with one or the other. The main determinant would be bone size and shape.

The modular system has a variety of sizes of the femoral implant, the acetabular implant, the prosthetic femoral head diameter, and the femoral neck length. They are interchangeable so the ideal combination of each of these elements are determined for each patient.

Post op total hip replacement

Scheduling:

Hip replacement surgery can be performed at any of our facilities.  During preoperative consultation, the procedure is fully explained, and the surgery scheduled soon after.  The patient is dropped of the day before or the early morning of surgery. Most dogs will be discharged one day after surgery, but occasionally they will be hospitalized for an additional day. Scheduled rechecks include suture removal at 10-14 days, an 8 week visit with radiographs, and a 16 week visit with radiographs. A cost estimate is typically $5500-6000 per hip, but with preoperative and postoperative diagnostics and radiographic evaluations the total is expected to be about $6500 per hip.

Home Care:

The single most important element is exercise restriction for 16 weeks.  Dogs are prohibited from any running or jumping during this time.  Clients must be fully aware of the potential complications that can occur with unregulated activity.  When outdoors, patients must be on a leash only, very gradually increasing in walking times from 15 minute walks by 8 weeks, and 25 minute walks by 16 weeks, but they should at no time be allowed to exercise vigorously.   Physical therapy is not recommended for most patients. Dogs usually feel well enough to do too much too soon. They are typically weight bearing on the operated limb within 24 hours of the surgery, and they want to start playing within 2 weeks. They need rest….rest….rest.

Expectations and Complications:

Greater than 90% of cases go through their recovery without complications, and return to full weight bearing and normal activity once recovery is complete.  Clients are rarely disappointed with results. Unfortunately, just as the procedure itself is elaborate and expensive, the complications tend to be elaborate and expensive. Potential complications include implant loosening, infection, luxation of the new hip, and femur fracture. Some of these can be resolved with additional surgery, though removal of the implants may be required in the more severe cases, resulting in the equivalent of an FHO. When additional surgery is required we typically will discount it, depending on the cause of the complication, if one is evident.

Why not FHO?

The principal negatives to FHO are less predictable results, and limited options if results are not optimal. FHO will predictability result in decreased range of motion which can impair gait and weight bearing. If it does, total hip replacement after FHO is not a viable option. The single advantage to FHO is lower cost which is understandable. When we consult with clients regarding painful hip conditions we will discuss FHO if finances preclude hip replacement, but it is not advised, especially in larger dogs.

Author:  Scott Bertrand, DVM