The first hip replacements in people and in dogs were what is known 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 Moores we have used the Kyon 'Zurich' system since 2008. 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. Total hip replacement is also a great option for smaller dogs and even cats with hip disease or hip fractures. In these smaller patients cemented total hip replacement is performed.
Some canine cementless THR systems which use a 'press-fit' femoral stem run the risk of femoral fractures developing 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. Both the stem and the cup are coated in hydroxyappatite to encourage bone to grow onto/into the implants.
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. Cemented THR is also an option for small dogs and cats with hip disease, avascular necrosis of the femoral head (Legg Perthes disease) or non-reconstructable hip fractures.
Total hip replacement is not appropriate for all dogs with hip disease or for all owners. 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. The nature of this type of surgery and the quality of the implants we use mean that total hip replacement is not a cheap option for your pet; as a guide, the cost for a straight-forward hip replacement surgery will be in the region of £4,500-5,500 (includes VAT) and there are likey to be additional preoperative and postoperative costs. The costs involved are always discussed at the initial assessment. Alternative surgical options do exist if these costs are prohibitive, although other surgeries do not offer as full a return to function or comfort as total hip replacement.
Why choose Anderson Moores? With a technical surgery such as a THR it is critical to have a good surgeon who is very familiar with the procedure. Andy Moores performs all the THRs at Anderson Moores. Andy has been performing THR surgeries in dogs since 2003 and has performed over 100 THRs at Anderson Moores, including complex revision THRs. And it is not all about the surgeon - we also have a great team of specialist anaesthetists and nurses to ensure your pet's surgery is as safe and comfortable as possible. Finally, implant positioning is an important factor in THR success and we routinely use fluoroscopy (video x-ray) in the orthopaedic theatre which allows us to be very consistent with implant positioning.
To minimise the risk of complications it is very important to strictly rest your pet after THR surgery. This sample discharge sheet will give you an idea of what is involved..
THR Sample Discharge Sheet
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 Moores we will request your consent for inclusion in the registry.
Click here for further information on the Hip Registry
If your dog will be having a hip replacement it would be helpful if you could bring a completed Hip Registry consent form with you prior to the surgery:
Click here for the consent form
Click here for James' guide to Hip Dysplasia, published in 'Dogs Monthly' magazine October 2011 (thanks to Dogs Monthly for allowing this to be posted here www.dogsmonthly.co.uk)