Rheo Bionic Knee for Amputees

[Wayne Renardson]

>From one of our subscribers who prefers remaining in lurk mode:



Bionic Knee 'Learns' How to Walk New Prosthesis Is Designed To 
Adapt to the Movements Of Users at Varying Speeds    

By NICHOLAS ZAMISKA Staff Reporter of THE WALL STREET 
JOURNAL July 6, 2004; Page D8   

The human knee -- whose complexity is belied by its hinge-like 
appearance -- has proved to be second only to the hand in difficulty  
for doctors to replicate in the effort to help out amputees. Walking 
involves a delicate pattern of shifting between bearing weight and 
bending, doctors say, with the knee literally at the center. Enter the 
Rheo Knee, a bionic body part that its maker, Ossur, touts  as being 
able to "learn" and adapt to a user's idiosyncratic movements.   

"We can basically turn the knee on, have the person walk, and the 
knee begins to learn how that person walks," said Scott B. Elliott, a 
prosthetist with Ossur who has been testing the knee for the past 
three years. "If they start to change their walking speed, Rheo will 
be watching."   

A small group of prosthetists has been selected to receive the first 
batch of Rheo Knees as part of what Ossur officials call "a soft 
launch" of the new product. The knee will be available to the public 
sometime early next year, according to officials of Ossur, which is 
based in Iceland.   

So how does a prosthetic knee learn? Electronic sensors on the 
artificial joint measure both its angle and the loads it is bearing 1, 
000 times per second while a computer chip, manufactured by 
Motorola Inc., controls the viscosity of a magnetic fluid inside the 
knee. Tiny metal particles suspended in the fluid form small chains 
when the magnetic field is turned on, causing the fluid to become 
thicker. That, in turn, affects the stiffness of the joint, which is 
modified constantly while the knee is in use, allowing for a smooth  
swing of the leg.  

Doctors will be able to monitor the Rheo with Hewlett-Packard Co. 
's handheld iPAQ computer, which can be plugged directly into the  
knee, providing information about the internal settings, the battery 
and other data.  

It sounds expensive, and it is. The starting cost for the Rheo will be 
around $18,000, although the final price tag for a knee, foot, socket 
and labor of a prosthetist to fit the limb could be anywhere from $ 
40,000 to $50,000.  

Patient Testing

The completed design of the Rheo Knee has been tested in only 13 
patients for one month, although 10 others have tested earlier 
versions of the knee during development. Given the lack of 
independent research on the Rheo Knee, it isn't yet clear whether the 
technology will translate into improved functionality for amputees. 
"I love it," says Julie Greder, one of the test subjects who has been  
using the Rheo Knee for around a year. "It feels like it does the 
walking for you."   

While there's another "self-learning" knee on the market, made by 
Daw Industries Inc. of San Diego, Calif., the Rheo Knee's main 
competition, the C-Leg, made by Otto Bock HealthCare of 
Germany, is now widely in use for wounded soldiers returning from 
Iraq. World-wide, more than 5,000 people have been fitted for the 
C-Leg, which costs around $16,000.   

At Walter Reed Army Medical Center in Washington, Paul 
Pasquina, chief of physical medicine and rehabilitation, says that 
wounded soldiers he works with have been "extremely happy" with 
the C-Leg, but he is eager to see the Rheo Knee come out of testing.  

"We're still a long way off from recreating a leg as good as the one 
you're born with," he says.  

But Ossur's knee, which uses the same magnetic technology found 
in the shock absorption systems installed in some new Corvettes, 
may have an Achilles' heel, so to speak, according to competitors 
familiar with the design. When its battery dies, the knee becomes a  
"free swinging joint," leaving the user prone to a fall.  

'Reviewed and Abandoned'

Indeed, Otto Bock is dismissive of Rheo. "The Rheo Knee, at its 
heart, uses a very sexy technology, which we reviewed and 
abandoned nine years ago," said Patrick Chelf, vice president of 
marketing and business development for Otto Bock in the Americas. 
Otto Bock says that its C-Leg is the most reliable knee in the 
industry, helping users avoid falls.  

Technicians at Ossur counter that with the Rheo Knee, warning 
signals will give the user ample notice that the battery needs to be 
charged before it shuts off.  

Ossur CEO Jon Sigurdsson, a 48-year-old former Icelandic diplomat 
who joined the company eight years ago, predicted that in coming 
years, many artificial joints will have some sort of intelligence 
similar to that found in the Rheo Knee.  

Innovation in prosthetics has often been prodded along by wartime, 
as wounded soldiers return home. Fighting in Iraq has produced 
more than 800 U.S. deaths since the war began and at least 100 
amputees, according to doctors at Walter Reed Army Medical 
Center.  

Anticipating where artificial-limb technology is headed, researchers 
at the Defense Department are already looking at whether signals 
from the brain can be captured and transmitted directly to the 
artificial limb.  

The market for high-end prosthetics is a relatively narrow one, 
given that a small fraction of the more than one million amputees in 
the U.S. can afford the latest artificial limbs. Ossur expects to sell a 
few hundred of its new knees next year, but hopes sales will grow 
after word of the new technology has gotten out.  

For an industry faced with such a small market, sinking money into 
research and development is a risky business. Even after seven years 
on the market, the C-Leg has still not made a profit for Otto Bock, 
which estimates that total revenue among all prosthetics 
manufacturers in the U.S. hovers around $300 million annually.  

Health-insurance companies, meanwhile, can balk at paying for the 
most expensive limbs.  

"You can have this great technology out there, but the real concern 
is how you can actually put it on patients," said David McGill, 
chairman of the board of the Amputee Coalition of America, a 
nonprofit advocacy group. "The reimbursement end of this thing is  
a disaster."