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Prosthetics can be anchored to bone

SHARE Prosthetics can be anchored to bone

Titanium screws implanted in the bone form a stable anchor for an artificial leg, providing more flexibility and general quality of life, according to a Norwegian man who has experienced both traditional and "osseointegrated" prosthetic legs. The same technique can also be used to anchor artificial arms.

It's a process that soon may be available in the United States to some with above-knee amputations or missing arms. The Department of Defense has reportedly expressed great interest on behalf of injured American soldiers. And local orthopedic surgeons are looking into getting the process — invented in Sweden more than 15 years ago — approved by the Food and Drug Administration.

Many Utahns had their first look at the implantable devices this week, when Norwegian Erik Ax doffed his pants to demonstrate the prosthetic device for his leg that he's enjoyed for six years during a presentation at the Salt Lake City Library Tuesday afternoon. Wednesday morning, his Swedish surgeon, Dr. Rickard Branemark joined him for an orthopedic Grand Rounds lecture and demonstration at the University of Utah School of Medicine.

The process is called osseointegration because the titanium screw is fitted into the bone, which then grows around it. Branemark's father, Dr. Per-Ingvar Branemark, first discovered that bone and titanium fuse together while doing research in the 1950s in Sweden. The first successful titanium implants, in 1965, were the posts to which replacement teeth are attached, a now commonly used implant technique that has changed modern dentistry. Next, the elder Branemark's team began working on implantable titanium frames to which artificial ears, noses and other cosmetically needed features could be attached following disfiguring facial tumors and accidents.

In 1985 a woman whose legs were amputated challenged the doctors in Sweden to make her titanium implants so that she could stand. She had very high amputations that made traditional prosthetics impossible. In 1990, she was fitted with a pair, each anchored into the bone. But Branemark noted that with high amputations, the risk of a bone fracture increases.

Advocates of osseointegrated prosthetics say it's not for everyone. It's best for those who are relatively young and have above-knee amputations, for instance, when it comes to legs. It's a less perfect match for patients who lost a limb because of circulatory problems.

In the early days of the prosthetic limbs — most often legs — the risk of deep infection or loosening of the screws was about 45 percent, but most of those could be fixed for an overall success rate of about 85 percent, Branemark said. Now, about 5 percent experience one of those complications.

It has become a well-defined, standardized process, Branemark said. The patient has an initial surgery to implant the screw/post, then is given six months to heal. Those with traditional prosthetics can go back to using them during that time. Once the bone has formed around the implant, a second operation occurs to trim the skin and create a muscle platform, as well as extend a post out through the skin. It is to that post the leg will eventually be attached.

Both surgeries require some in-patient time in the hospital.

It takes about a year to get from the initial surgery to completed gait training, including time during which a short training prosthesis is used. Weight is gradually added to that until the individual's weight can be borne on the artificial leg and implant.

Ax was practically gleeful as he spun his leg around and bent his knee up backward, then demonstrated how quickly he can get the leg on and off. Ax, now 66, was injured in a hunting accident nearly 20 years ago. Since them, he has gone through two different prostheses in which the residual leg stump slips into a socket. He would never go back, now that he's had the implantable variety, he said.

Branemark believes that eventually "brain-controlled" devices will be available in the implantable form. He showed video of one patient climbing a rock wall and of Ax riding a bike.

Ax said he no longer has to fuss with a sweaty socket, he can sit on any kind of surface, and he can move his leg sideways, something that Salt Lake resident and prosthetics expert Tom Andrew, who lost his own leg 32 years ago, cannot do as well, although they have the same type of leg except for how it attaches to their bodies.

Ax says he can sense the different surfaces he's walking on, which he could not do before. And his hips move better, without skin sores on the groin area. He's so active, in fact, that he broke his leg by the hip — nowhere near the implanted titanium screw, which held up just fine.

Andrew was intrigued by the integration with bone but said he does very well with his current legs. He was blessed, he said, with a good stump, so he doesn't have some of the problems that some people with amputations experience. Some find the socket is tight if they gain weight and it falls off if they lose weight, he said.

E-mail: lois@desnews.com