Prosthetics Advance With Osseointegration
Animal limbs damaged beyond repair are typically amputated, but specialists say the recent success of osseointegration may change the veterinary standard of care.
Veterinary oncologists and surgeons performing frequent amputations due to disease or accident are especially interested in finding alternatives to removing an entire limb when only a portion is adversely affected.
“Osseointegration is the connection of living tissue and bone with an artificial implant and has seen success through numerous surgeries,” says Denis Marcellin-Little, DEVD, associate professor of orthopedics at North Carolina State University. “The procedure is similar to that used in dentistry with artificial teeth and allows the patient to retain the integrity of the limb.”
Infection and implant longevity have stymied vertical evolution of the procedure until now. Dr. Marcellin-Little recently performed osseointegration on a German shepherd missing a portion of its rear leg, while Erick Egger, DVM, associate professor of small-animal orthopedic surgery at Colorado State University, used osseointegration to replace the foot of a Saluki. Both animals are bearing weight on their new limbs.
These procedures serve as markers for the future of animal prosthetics. The implant allows the prosthetic limb to attach without chafing or irritation, and gives the limb a more natural range of motion and the potential of the animal sensing the prosthetic foot as an original appendage. When the prosthesis is screwed into the bone, the bone grows around it and could bring more sensation to the leg and better manipulation of the prosthetic foot.
A custom osseointegrated implant is typically secured to the proximal tibia and includes a titanium osseointegrated component, a ridged tube and a foot. The foot is fitted once the bone ingrowth into the osseointegrated implant is deemed appropriate to support the weight.
“While advances in technology are improving the procedure, a remaining obstacle is general practitioners’ willingness to recommend a prosthetic to an owner, whether it’s internal or external,” says Kevin Jones, DVM, of Animal Rehabilitation and Wellness Hospital in Raleigh, N.C.
“My hope is that the more technology is utilized, the more affordable it will become and more vets will make the suggestion to clients,” Dr. Jones says.
Martin Kaufmann, founder of OrthoPets, a Denver-based company specializing in animal prosthetics, says the introduction of prosthetic services for animals has brought an evolution in design and material composition.
“Veterinarians need access to information guiding them through elective levels of amputation which are conducive for a prosthetic treatment plan,” Kaufmann says. “OrthoPets offers a veterinary certification course to educate them on prosthetics. Considering a treatment plan is contingent on client compliance. Cost of the device is a factor and is a common question clients are concerned about. The price depends on the material, speed of which the device is requested and the number of joints the device must control. Typically, the price can range from $600 to $1,000.”
The primary limitation in the animal prosthetic field is that the mechanical hinges needed to replace major anatomical joints such as the elbow or stifle are not available.
This means that an animal needs to have a residual limb that includes these major joints. When this technology becomes available, Kaufmann says, it will revolutionize the animal prosthetic treatment options available to patients who have lost the majority of their limb.
Although animals can function well with three limbs, the stress on remaining joints is greater and general body conformation is significantly compromised, both of which become more apparent over time.
“Tripods flex or arch in unnatural positions to propel themselves,” Jones says. “This antagonizes arthritis and can cause tendinitis. The animal’s energy expenditure is also significantly higher. In addition to cost, time and dedication are drawbacks to external prosthetic fitting. There are a lot of adjustments that must be performed and frequent visits to ensure comfort and functionality.”
An animal can benefit significantly through rehabilitation, which is often a phase in the prosthetic regimen.
“Not using a limb for an extended amount of time causes muscle loss and poses a problem for using the prosthetic,” says Kim Danoff, DVM, of Veterinary Holistic and Rehabilitation Center in Vienna, Va. “Rehabilitation therapy can build or rebuild the muscle, training the animal to bear weight on the limb, maximizing the prosthetic’s efficiency.”
Marcellin-Little’s 2005 surgery with a feline implant was a success until the animal’s activity and eagerness to use the limb snapped the titanium nail inserted into the bone. The design has since been strengthened.
“We are continuing to gain more experience with the surgical technique,” Marcellin-Little says. “There is hope that the continued success of osseointegration will lead to use in larger animals such as horses that are typically euthanized due to damaged limbs. Ultimately, veterinarians will be viewed as trailblazers for the introduction of osseointegration into human medicine for amputees.”
OrthoViewVET, a new veterinary software, provides preparational templating for prosthetic procedures. The software gives a digital image for joint replacement, fracture management, limb deformity and general measurement.
“I teach the principles and the importance of accurate planning for tibial osteotomies, total hip replacement and fracture fixation,” says Antonio Pozzi, DVM, assistant professor of small-animal surgery at the University of Florida Veterinary Medical Center. “The ability to visualize all this on-screen using OrthoViewVET’s
specially designed tools is an enormous step forward. Improvising during a surgical procedure is dangerous. Planning ahead with this software tool will give the surgeon a digital example of the limb ahead of time.”
Experts predict that more pet owners looking for the newest technological options will jump on the prosthetics bandwagon.
Marcellin-Little is interested in creating a prosthetic with a computer chip that would allow the animal’s muscle to control the prosthetic’s movement. The downfall again is the cost.
“Since none are currently used in animals, it’s not impossible for it to cost $100,000,” Marcellin-Little says. “However, the benefits of this would include the ability for an animal to lock and unlock the artificial joint using its muscles.”
Through research and trial, veterinarians have covered new ground in prosthetics.
“We need to learn how to maximize engineering to perfect prosthetics,” Marcellin-Little says. “Prosthetics save lives or entire limb loss. The implants and external prosthetics will always need to be monitored and tweaked, but it’s very rewarding to see an animal return to near-normal ability, and it’s worth the effort."