After just a few short years, the neurally controlled Modular Prosthetic
Limb (MPL) system, developed by The Defense Advanced Research Projects Agency
(DARPA) and The Johns Hopkins University Applied Physics
Laboratory (APL), is ready for testing with quadriplegic patients.
Created by APL as part of DARPA’s
Revolutionizing Prosthetics 2009 Program (RP2009), the MPL
device was designed to be closer to a natural arm than any existing prosthetic
device in its appearance, ability and connection to the body.
Natural prosthetic limb
The ultimate mission, Col. Geoffrey Ling, MD, PhD, DARPA program
manager, said, was to create an upper extremity prosthetic device to serve as a
fully functional replacement to a lost natural limb.
|Michael P. McLoughlin|
“In the meantime, there are a lot of young people who really need
these arms to get back to their activities of daily living,” Ling said.
Once selected for the project, the APL team wasted no time. As the first
step of the RP2009 Program, APL set to work developing a prosthetic hand and
arm similar to a natural limb in its weight, appearance and strength.
“It was very challenging to get all of that capability into a
package size that’s equivalent to a 50th percentile male limb,”
Michael P. McLoughlin, APL biomedicine deputy business area executive, said.
Despite those challenges, the team succeeded. The MPL arm boasts 22
degrees of motion, including four fingers that move independently, a thumb that
pivots on a ball joint — a first for the prosthetics industry — as
well as a powered shoulder, elbow and wrist. And the device weighs only about
nine pounds, which is the weight of a natural limb, according to a press
upper extremity prosthetic device to replace a lost natural
Applied Physics Laboratory
This feat required a parallel effort with a team of neuroscientists who
would learn to decode neural signals and then leverage them to drive this robot
arm, Ling said.
“In essence, our goal is that the patient will have full function
back, in terms of being able to use that arm without thinking about it anymore
than you would think about using your own arm,” Ling told O&P
Because the system is modular, the limb can be adapted to fit patients
with various levels of amputation. Likewise, the device can interface with the
body at a number of different neural sites.
“It allows you to deal with a range of injury conditions,”
McLoughlin said. “Someone with a fairly intact, well-preserved peripheral
nerve system has an option to utilize those nerves. On the other hand, for
severely injured patients, spinal cord patients or ALS patients who have lost
the ability to control their natural limb, the only option is a cortical
interface directly to the brain.”
According to a press release, the DARPA-awarded contract granted APL up
to $34.5 million to manage development and testing of the MPL system and
neurally controlled interface on quadriplegic patients.
“This is unusual in the world of prosthetics and orthotics,”
Ling said. “When has anybody, any government agency, thrown this kind of
money into an effort to develop such a platform? It just doesn’t
|The MPL arm offers a powered
shoulder, elbow and wrist, and weighs the same as a 50th percentile male
|Image: Johns Hopkins University
Applied Physics Laboratory
He said he wants to take full advantage of this opportunity, including
all of the government agency’s resources.
“This is an agency that builds rockets. Now to be able to throw
that level of funding behind developing a prosthetic arm, I think, was just
tremendous,” he said.
A second firm,
DEKA Research and Development Corporation, spearheaded another
of DARPA’s efforts to develop the best possible prosthetic arm in a 2-year
timeframe. Ling said that he was looking for an arm that looks like a natural
arm and has a high degree of functionality. The Generation II DEKA Arm met
those requirements, and has moved onto its own set of neural trials with
“We hope that soon it will be available for widespread use, and be
commercially available,” he said. “DEKA produced a fantastic, highly
robust arm, with limited capability when compared to the APL arm, but far
exceeds what’s clinically available.”
Ling said that he is proud of what DARPA has accomplished.
“I challenge anybody to come up with that kind of a success story
in a government program,” he said. “We came with nothing more than an
idea; to actually have something in clinical trials within 3 years, I think is
Ling called the Program’s next step monstrous. While the team has
been successful in pre-clinical studies, he said, the real test begins with the
patient trials, expected to start by the beginning of next year.
For this phase, McLoughlin will look at how cortical devices could be
used to control the prosthesis. With this interface, spinal cord injury
patients were the ideal patient population for testing.
“Patients with a high spinal cord injury have no control of their
natural limb, and there are no real options for them,” he said.
|The MPL is a modular system and
can be adapted to various levels of amputation.
He said that the testing, which is partially funded by the VA, will
focus on connecting these patients with devices that will be mounted in
proximity to the patients — on their wheelchairs, for example. Then the
patients will control the prostheses with their minds, using them to complete
any number of activities of daily living.
“A lot of what we learn here in terms of the ability to use the
prosthetic limb will ultimately benefit the amputee population too,”
McLoughlin said. “We’ll extend our understanding of how to translate
the signals from the brain into motion. It doesn’t matter whether the
patient has a spinal cord injury or is an amputee. It’s still the same
problem. I think there’s a benefit to working across multiple types of
Future of the project
As specified in their contracts, both APL and DEKA have a commercial
transition partner to bring these devices to market. How soon either of these
projects is ready for commercialization remains to be seen.
Ling has been working toward FDA approval since the beginning of the
project, going as far as including an FDA representative in development of the
original proposal. He also said he hopes that CMS will create billing codes for
both devices, so that civilian patients can benefit from this new technology as
“I’m hoping that the community at large will start to pick up
the ball on this,” he said.
McLoughlin said he shares that hope for all amputees.
“My goal, personally, is to make sure that when we’re done
with this program, we led the way so that the commercial industry is able to
pick it up and provide the arms to amputees and other patients and,
particularly for military populations that have been injured in current
conflicts, to be able to provide them a capability that is going to have a big
impact on their lives,” he said. “When we’re done, we really
want to have made a big difference in their lives.”
|The arm provides 22 degrees of
freedom, among other features.
|Image: Johns Hopkins University
Applied Physics Laboratory
The important lesson to learn from this project, Ling said, is that all
of the people involved in DARPA’s work have changed the field forever.
With these devices — and future devices, built on technology like this
— amputees and other disabled individuals no longer will be hindered by
their physical limitations.
“We can actually change the concept of what is being disabled.
It’s a matter of just putting it together,” he said.
“DARPA didn’t invent any new science here. What we’ve
done is gathered up all the good scientists and engineers — put them in a
room, put them on a project — and by coming together, look what
they’ve done,” Ling said. — by Stephanie Z. Pavlou
For more information:
The Orthotic and Prosthetic profession has long needed the impetus that
government research dollars can provide to address difficult topics and
scenarios within our unique rehabilitation field. This is a unique time in our
history when a culmination of events has created opportunity for our profession
to be forever altered. The events of a war — where lives are being
preserved secondary to improved body armor, while limbs are sacrificed to
traumatic blasts — are converging with media, government and public
interest in the rehabilitation available to military limb-absent individuals.
This focus, combined with research dollars, engineering interest and clinical
energy is creating greater hope for military and civilian patients and
Those of us who are fortunate enough to participate in the DARPA
programs are excited that these efforts are becoming available to our military
patients. At the same time, we can inspire our civilian patients with progress
we trust will be available to them within the foreseeable future.
It is becoming clearer as these technological advances occur that the
orthotic and prosthetic profession will need to adjust in order to be
proficient at delivering these technologies in a successful and useful way to
patients. The possibility of specialties within our profession is already a
topic of great interest to orthotic and prosthetic professionals. The concept
of further subspecialties and appropriate training to create, manufacture and
successfully fit limb-absent or paralyzed individuals with neural
prosthetics/orthotics is something for the present and not the distant future.
Our profession will need to make strides toward creating specialty education,
properly certifying individuals and establishing outcomes for these advanced
— Dan Conyers, CPO
director, Advanced Arm Dynamics