The Orthotic and Prosthetic Assistance Fund (OPAF) offers the following
articles from yesterday’s Washington Post as public service announcement
(PSA), in fulfillment of OPAF’s official representation of O&P in
community and philanthropic circles. OPAF aims primarily to enable
individuals with physical disabilities – especially those served by
members of the orthotics and prosthetics (O&P) community – to enjoy the
rewards of personal interaction, physical fitness, and social
interaction. Complete information about OPAF is available at
http://www.opfund.org.
These articles will be of particular interest to members of the O&P
community who, like OPAF, are engaged in promoting greater public
awareness of the past, present, and future of O&P.
Washington Post article #1 (below), by Sumitra Rajagopalan – “Firm
Strives to Give Amputees a Natural Gait”
Washington Post article #2 (also below), by Manuel Roig-Franzia – “A
137-Year Tale of One Soldier’s Hand-Me-Down Limb”
—
Firm Strives to Give Amputees a Natural Gait
By Sumitra Rajagopalan
MONTREAL — Contemplating the stairs up to his rehabilitation center,
Andre Tremblay grips the railings firmly, then winces in discomfort as
he laboriously swings his artificial leg up onto the first step.
He climbs two more steps, each time twisting the stump where his left
leg was amputated to turn and lift his prosthetic limb. He looks up and
sighs. He has a long way to go.
Hundreds of miles to the north, in a testing laboratory in the sleepy
Quebec City suburb of St.-Augustin-de-Desmaures, Guy Brousseau tries a
very different artificial leg. Under the glare of television lights, he
slowly but smoothly climbs up a set of stairs. He then turns around and
climbs down. He repeats the routine twice, before turning to a group of
onlookers, who are visibly wowed. His eyes sparkle. “It moved on its
own!” he exclaims.
Brousseau’s modest steps are being called a giant leap in the
development of bionic limbs. The fruit of years of intensive research,
the leg includes a motor-driven knee and a complex system — sensors and
a microprocessor — that gives it the uncanny ability to move and bend
naturally.
For Stephane Bedard, the motor-driven knee and leg represent the
realization of a vision he first had in 1997.
Back then, Bedard was a competitive mountain biker recovering from a
knee injury in his native Quebec City. At a rehabilitation center, he
was drawn to the plight of above-the-knee amputees as he watched them
struggle to get around with passive prosthetic legs. By the time he left
the center, his passion for mountain biking had given way to a new
mission in life.
Bedard, a graduate student in mechanical engineering at Laval
University in Quebec City, set out to design an above-knee prosthetic
leg that would function like an amputee’s lost limb. For this, he first
had to delve into the complex science of locomotion.
The complexity stems from the two seemingly contradictory functions of
human legs. Legs get us going, yet they also keep us grounded. That dual
nature — providing both motion and balance — makes mimicking
locomotion challenging.
Furthermore, unlike arms, which rely almost entirely on the brain for
direction, legs get their marching orders from a lesser authority.
Locomotion is largely orchestrated by nerve cells scattered throughout
the leg.
These cells, known as afferent neurons, are attached to receptors in
the leg muscles. They “sense” the terrain by the way the muscles stretch
and shorten in response to the ground and external loads, and they relay
this information to the spinal cord. Nerves in the spinal cord use this
feedback, combined with brain signals, to select a walking pattern
appropriate to the situation and trigger the leg muscles to move
appropriately.
As he began to understand the mysteries of locomotion, Bedard founded
Victhom Human Bionics to try to develop prostheses that would exploit
these insights.
In his office overlooking the St. Lawrence River, Bedard, now 37 and
Victhom’s chief scientific officer, recalled the first 18 months he
spent trying to crack the secret code of locomotion, painstakingly
analyzing a multitude of walking patterns. He studied how legs slow down
or speed up, their response to slippery surfaces or rugged terrain, and
their motion uphill and downhill. He then translated these patterns into
computer code and fed this data into a microprocessor that could be
fitted into an artificial leg.
The next challenge was to design devices that would take the place of
afferent neurons. He and his team built sensors sophisticated enough to
get a feel for the terrain by picking up several cues at once —
pressure, angles, speed and twisting forces called torque, among others.
These sensors, placed at strategic points along the artificial leg,
capture data about the terrain 120 times a second.
The result is an electrical relay race: The sensors transmit
information to the microprocessor. The processor leafs through its
almanac to pick out a suitable walking pattern before sending
instructions to the knee’s electric motor. The motor, in concert with
the sensors and microprocessor, moves the leg in much the same way that
afferent neurons and leg muscles come together to choreograph movement.
Other microprocessor-driven knees on the market, notably Otto Bock’s
C-Leg, also use sensors to control artificial legs, but Victhom’s
approach takes the technology a step further by using the motor as a
“muscle” to propel the leg forward.
Marc Mayrand, a clinical prosthetist at the Quebec Institute of
Rehabilitation, oversees clinical trials of Victhom’s product.
Mayrand, who has no financial ties to Victhom, says the amputees he
works with love the way the knee’s motor helps them move forward, unlike
other prosthetic knees that require them to supply all the energy.
Its most striking feature, added Mayrand, is that amputees can flex
and bend their knees when climbing or traversing rocky terrain, without
having to twist the leg to raise it.
The motor-driven knee has awed many in the industry, including
Iceland-based Ossur, a world leader in prosthetics that teamed up with
Victhom to manufacture and market the leg.
Hanna Smaradottir, products manager at Ossur’s head office in
Reykjavik, noted that the idea of motor-driven knees has been around
since the 1970s. What impressed her and her colleagues was the
systematic approach that Bedard and his team took to understanding and
replicating the nuances of human gait.
Ossur is gearing up to launch the prosthetic knee this fall, but
engineers at Victhom’s laboratories are already working on the next
generation of bionic legs.
To fully integrate the artificial knee with the amputee’s body, Bedard
has been seeking ways to allow the prosthesis to communicate with nerve
endings in the amputee’s stump. For this, he turned to someone who
understood the esoteric language of nerve cells.
Mohamad Sawan, a professor of electrical engineering at the Montreal
Polytechnical Institute, has worked extensively on implantable medical
devices. He designed tiny “cuff” electrodes that fit snugly around nerve
endings and can be implanted into the stump. The electrodes capture
electrical impulses, known as electroneurograms, streaming from the
nerves, and send them to an electronic “translator,” also implanted in
the stump. This device transforms the neural jabber into clear
electrical signals and transmits them wirelessly through the skin to the
microprocessor in the artificial leg.
Bedard is still experimenting with this version and will not discuss
details of Sawan’s system or other improvements in the newest leg.
Smaradottir admits that there is room for improvement. For one thing,
the electric motor makes the leg rather heavy, a problem for small
amputees.
Mayrand said amputees would benefit from a powered ankle as well, to
allow for free rotation of the artificial foot.
Is the day coming when the bionic man could run, hop and jump?
Bedard laughed. “And dance, too, maybe?”
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——-
A 137-Year Tale of One Soldier’s Hand-Me-Down Limb
Robert Hanna must have been a pretty handy guy.
Some Yankee’s bullet cost him his leg at the Battle of Gettysburg, but
he figured out a way to get around without it. Once he was back home in
North Carolina, Hanna took to whittling peg legs and fitting them
himself. They did him just fine.
But one day he heard the State of North Carolina was giving away legs.
He went down to Raleigh and picked up an artificial limb made of wood,
iron and leather. Hundreds of Civil War veterans did the same, as North
Carolina was the first former Confederate state to make an irresistible
offer to its amputees: a free leg or 70 bucks.
Most of those old legs are gone now, disintegrated by time and heavy
use. But Hanna’s leg miraculously survived, passed from generation to
generation, an artifact of a bygone era.
Hanna’s grandson, Duncan Hanna, figured he had something special and
contacted state archivists who could not have been more pleased. They’re
displaying grandpa’s leg at the Bentonville Battlefield, a testament to
the South’s undying fascination with all things Civil War.
But still, there’s the question of how Hanna’s leg survived while
others disappeared. Ansley Herring Wegner, a researcher with the North
Carolina Office of Archives and History, knows the answer. It turns out
that Hanna, the peg-leg whittler — like his grandson 137 years later —
thought the store-bought leg was something special. It was, Wegner says,
“his Sunday-go-to-meeting leg.”
— Manuel Roig-Franzia
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