TOTAL HIP REPLACEMENT

The first hip replacements in people and in dogs were what is know as 'cemented' total hip replacements (THR), meaning that the implants (the cup in the acetabulum of the pelvis and the stem in the femur) were held in place using an acrylic cement, known as bone cement. These have been very successful and are still very commonly performed in people and dogs. Over the last decade or so 'cementless' hip replacement has become increasingly popular in people, particularly if they are still active. Rather than using cement to hold the implants in place, these systems rely on the friction created by a ‘press-fit’ between the bone and the implant. Cementless implants are also coated to encourage bone to grow into/onto the implant with time. Avoiding the use of cement reduces the amount of implanted foreign material thus reducing the infection risk. The implants may also last longer as particulate matter generated from the cement is a factor in implant loosening.  Finally, implant revision, if necessary, is more straight-forward. 

Cementless systems are now also available for our canine patients and have the same advantages as the human cementless systems. At Anderson Sturgess we use the Kyon 'Zurich' system for most dogs. This system was developed in Switzerland in the 1990’s and is used for dogs greater than about 15-18kg in size. Over 7,500 prostheses have now been implanted, with over 140 surgeons world-wide using the system. For smaller dogs (and even cats), cemented total hip replacement is available.

Some canine cementless THR systems which use a 'press-fit' femoral stem have a relatively high incidence of femoral fractures when the stem is hammered into the femur. The Kyon system has the advantage that the stem does not need to be hammered into a precise 'press-fit' since locking screws are used to fix the stem to the femur. Over time additional stability is afforded by bone growth onto the titanium surface. The polyethylene cup has a perforated titanium shell for bone ingrowth.

So what cases are suitable for THR? THR is generally reserved for dogs with significant and persistent clinical signs attributable to hip disease, most commonly hip dysplasia/osteoarthritis but occasionally for certain fractures. Surgery is not appropriate for dogs with radiographic evidence of hip disease but no associated clinical signs. Most patients are older than 10 months, but the unique fixation of the Kyon stem means that we have been able to provide dogs as young as 7 months with a total hip replacement.

Total hip replacement is not appropriate for all dogs with hip disease. Prior to surgery all patients are assessed clinically and radiographically. Long term management options, costs and the risks of surgery are always discussed with the owner in detail prior to committing to hip replacement.

We are members of the BVOA Hip Registry. The aim of the registry is to improve our understanding of the long term success rate of total hip replacement in dogs. If your dog has a hip replacement at Anderson Sturgess we will request your consent for inclusion in the registry.