Total Hip Replacement
What is a total hip replacement?
The hip joint is a ‘ball-and-socket’ joint where the ‘ball’ is the femoral head and the ‘socket’ is the acetabulum of the pelvis. A total hip replacement consists of a metal femoral stem with a metal femoral head attached and a separate high-density polyethylene cup. The patient's diseased femoral head is removed and the metal femoral stem is positioned into the medullary cavity of the femur. The artificial femoral head articulates with the cup which is fixed into the pelvis.
What makes a good candidate for a total hip replacement?
Many dogs have hip dysplasia/osteoarthritis diagnosed from radiographs (x-rays) but do not demonstrate clinical signs. These dogs have good limb function without any evidence of lameness or pain. These dogs are oblivious to their hip problem and do not need a total hip replacement.
It is clearly appropriate to consider surgery for dogs with marked lameness and hip pain if they have not responded to measures such as 
exercise modification, non-steroidal anti-inflammatory drugs (known as NSAIDs -e.g. Metacam, Rimadyl) and weight loss (if appropriate).
Many dogs fall into the ‘grey area’ between the two scenarios above. There may be a degree of lameness or hip pain, which is responsive to non-surgical management to a greater or lesser extent. The decision to pursue surgical management for these dogs should be made on a case-by-case basis after consideration of the potential benefits and risks of surgery. Weight-loss can make a significant difference to over-weight dogs with osteoarthritis.
Infections that develop around hip replacements can be very difficult to manage and usually result in the removal of the implants. Infections can be caused by bacteria travelling through the blood stream from other areas of the body. For this reason any dog with an active infection such as a skin infection (dermatitis), ear infection (otitis) or dental disease (periodontitis) would not be a suitable candidate for a total hip replacement.
For more information and to read our Pre-Operation Client Information Sheet - Click here.
The system
The total hip replacement system used at the Royal Veterinary College is the Biomedtrix CFX system. It is a modular, cemented system. The choice of 7 different stem sizes, 4 different neck lengths and seven different cup sizes allows us to optimally tailor the size of the hip implants to most dogs over 15kg in body weight.
What can be expected after surgery?
Most dogs start to use the treated limb within 1-2 days of surgery. Initially they may benefit from being supported with a sling under their abdomen (tummy) in case they were to slip and fall. After a few days, once the postoperative inflammation is reduced, they are a lot more comfortable than they were before surgery.
Dogs are strictly rested for the first eight weeks after surgery. During this time they should be kept confined to a small room or kennel. They should not be allowed to jump onto or off furniture or into or out of cars. They must not be allowed to go up or down stairs, although shallow steps to get outside are ok if taken with care. They should be taken outside to go to the toilet a few times daily and this must be on a lead.
At eight weeks dogs are re-examined and are anaesthetised or sedated for follow-up x-rays. If all is well at this stage exercise can usually start to be increased, starting with gradually increasing lead walks. Short periods off the lead can be implemented from 14 weeks postoperatively.
Following total hip replacement dogs are expected to return to full limb function with a good range of motion in the hip joint and with an absence of hip pain.
What are the possible complications?
Complications are seen in 5-10% of dogs undergoing total hip replacement.
Postoperative infection is seen in less than 5% of cases. Infection can also develop any time after surgery if bacteria spread through the bloodstream from an infection elsewhere in the body. Infections can generally only be controlled with removal of the implants and the cement. The end-result is that the dog is left without a functioning hip joint –similar to a femoral head and neck excision, which we might consider as an alternative to a hip replacement in some dogs. A pseudoarthrosis or ‘false joint’ develops and limb function can be surprisingly good.
Dislocation (luxation) of the new joint is seen in about 5% of cases and is most likely to occur in the first eight weeks after surgery. For this reason it is important that dogs are strictly rested for this period. Dislocation can often be rectified but is likely to require another surgical procedure.
Loosening of the implants is an uncommon complication. Loosening of the cup can occur soon after surgery if it is not suitably positioned. Loosening of the stem is usually seen several years after surgery. Loose implants require removal. Implants that loosen as a long term complication can not generally be replaced.