On Four Legs Again
Advances with prosthetic surgery give three-legged dogs the hope for better mobility.
Although Sally and Cassidy will probably never meet, they are both catalysts in important advances in veterinary and human orthopedic medicine.
In spring 2005, Cassidy, a young German Shepherd Dog mix missing most of his lower-right hind leg, was discovered running around the streets of New York City. Two years later and half a world away, a Saluki named Sally was found hobbling in the Kuwaiti desert. Sally's lower-left hind leg had been cut off or trapped off.
Both dogs were rescued and ended up with owners who faced their dog's three-legged condition by opting for a new procedure known as osseointegrated prosthetic surgery. Cassidy and Sally received permanent implants attached to sophisticated artificial legs. Compared to a slip-on prosthesis, an artificial leg is far more secure and performs more like a natural leg.
"Osseointegration means bone-integration. That is, the tissues - bone, in this case - are firmly connected to the implant," says Denis Marcellin-Little, D.V.M., Dipl. ACVS, professor of orthopedic surgery at North Carolina State University in Raleigh and part of the team that performed Cassidy's surgery. The bone grows into or around the implant.
Osseointegrated implants are used daily in artificial joint replacements for prostheses that are completely buried inside the body, such as total hip, knee and elbow replacements in humans and dogs. They have been used for many years in humans as the base for artificial teeth, hearing aids and facial-reconstruction prostheses.
"Recently, several groups, mostly in Europe and England, have had some success using osseointegrated implants as a base for artificial limbs in humans," says Erick Egger, D.V.M., Dipl. ACVS, associate professor of small-animal orthopedic surgery at Colorado State University in Fort Collins. "Such devices are considered experimental at this time."
Although the ultimate goal is to perfect osseointegrated limb prostheses for human use, the procedure is also being perfected for dogs and cats. At least three veterinary groups in the United States and a study group in England are working in this area, using dog and cat models. In spring 2005, NCSU veterinarians implanted two prosthetic limbs to a cat born without the lower half of his hind legs. Later that year, now-retired veterinarian Robert Taylor, D.V.M., of Alameda East Veterinary Hospital in Colorado, performed similar surgery on the hind limbs of a Siberian Husky.
These two surgeries were initially successful, but the cat became so active he broke one of the prosthetic screws after a few months, and the Husky's prosthesis was removed after three years because of an infection. However, researchers learned from those initial cases.
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