(Press-News.org) In the last two decades, prosthetic limb technology has grown by leaps and bounds. Today, the most advanced prostheses incorporate microprocessors that work with onboard gyroscopes, accelerometers, and hydraulics to enable a person to walk with a normal gait. Such top-of-the-line prosthetics can cost more than $50,000.
Amos Winter is aiming to develop a passive, low-tech prosthetic knee that performs nearly as well as high-end prosthetics, at a fraction of the cost.
"We're going after this disruptive opportunity," says Winter, an assistant professor of mechanical engineering at MIT. "If we can make a knee that delivers similar performance to a $50,000 knee for a few hundred dollars, that's a game-changer."
Now Winter and his colleagues have taken a significant step toward that goal. In a paper published in IEEE Transactions on Neural Systems and Rehabilitation Engineering, the team reports that it has calculated the ideal torque that a prosthetic knee should produce, given the mass of the leg segments, in order to induce able-bodied kinematics, or normal walking.
Using the paper's results, the group has built a prototype of a prosthetic knee that generates a torque profile similar to that of able-bodied knees, using only simple mechanical elements like springs and dampers. The team is testing the prototype in India, where about 230,000 above-knee amputees currently live.
"In places like India, there's still stigma associated with this disability," Winter says. "They may be less likely to get a job or get married. People want to be incognito if they can."
The paper's co-authors include graduate student Murthy Arlekatti and Yashraj Narang, a PhD student at Harvard University.
Tuning torque
Most amputees in developing countries wear passive prostheses -- simple, cheap designs with no moving parts. "When you see people walk in them, they have a pretty distinctive limp," Winter says. In part, that's because passive prostheses do not adjust the amount of torque exerted as a person walks. For instance, in normal walking, the knee flexes slightly, just before the foot pushes off the ground -- a shift in torque that keeps a person's center of mass steady. In contrast, a stiff, unbending prosthetic knee would cause a person to bob up and down with each step.
Winter reasoned that in order to produce a passive prosthetic knee that mimics normal walking, he would have to also mimic the changing forces, or torque profile, during normal walking. He and his team looked through the scientific literature for data on normal walking, and found a complete dataset that represented one person's gait, including the angle of their joints, the weight of each leg segment, and the ground reaction force -- the force between the ground and the foot -- during a single step, or gait cycle.
The researchers used the measurements to calculate a torque profile -- the amount of torque generated by the knee during normal walking. As prostheses are generally one-third to one-half as heavy as human legs and feet, the researchers adjusted the torque profile to apply to lighter leg segments.
"If you applied healthy levels of torque to a much lighter limb, your kinematics would get all screwed up," Winter says. "Robotic limbs are designed to dial that torque back. Our challenge was, how do you tune the torque profile to get able-bodied motion, with a passive prosthetic knee?"
The researchers then looked at whether they could build a prosthetic knee to replicate the adjusted torque profile, using simple mechanical elements. Currently, the group has engineered a simple prototype that includes a spring and two dampers that act as brake pads. The spring allows the knee to bend just before the foot pushes off the ground. At the same time, the first damper engages to prevent the leg from swinging back. The second damper engages as the leg swings forward, in order to slow it down just before the heel strikes the ground.
Winter's team is now testing the design with volunteers in India.
"This was a quick and dirty prototype, but so far, we're seeing good indicators of natural gait," Winter says. "I'm not ready to claim victory yet, but [this paper] lays out a roadmap that is very different than what's been done before, which will enable us to achieve very high performance at low cost. And that's what we're going after."
INFORMATION:
This research was funded, in part, by the National Science Foundation.
Additional background
ARCHIVE: MechE spinoff launches all-terrain wheelchair in U.S.
http://newsoffice.mit.edu/2014/meche-spinoff-launches-freedom-chair-all-terrain-wheelchair-1124
ARCHIVE: Sun-powered desalination for villages in India
http://newsoffice.mit.edu/2014/solar-desalination-india-0908
ARCHIVE: GEARing technology for developing markets
http://newsoffice.mit.edu/2014/amos-winter-gear-lab-0729
NEW YORK, July 30, 2015 - Major achievements have been made in the domestic HIV/AIDS response as a result of increased realignment and coordination of efforts at the federal level. However, that level of consistent coordination and alignment has yet to take place in most states. In an effort to identify what needs to be done, amfAR, The Foundation for AIDS Research, in collaboration with the National HIV/AIDS Initiative at the O'Neill Institute for National and Global Health Law at Georgetown Law, has released a set of recommendations for how states across the U.S. can ...
BUFFALO, N.Y. - A little recognition for a job well done means a lot to children with Attention Deficit/Hyperactivity Disorder (ADHD) - more so than it would for typically developing kids.
That praise, or other possible reward, improves the performance of children with ADHD on certain cognitive tasks, but until a recent study led by researchers from the University at Buffalo, it wasn't clear if that result was due to heightened motivation inspired by positive reinforcement or because those with ADHD simply had greater room for improvement at certain tasks relative to ...
The presence of persistent human papillomavirus (HPV) type 16 DNA in oral rinses after treatment for HPV-related oropharyngeal cancer was rare but it appears to be associated with poor prognosis and therefore may have potential as a long-term tool for tumor surveillance, according to an article published online by JAMA Oncology.
HPV infection is responsible for the majority of oropharyngeal carcinomas in the United States. In 10 percent to 25 percent of patients with HPV-positive tumors, the cancer will progress after treatment and earlier diagnoses of progressive or ...
(Boston)--New evidence highlights the importance of the liver in immunity against bacterial pneumonia. The study is the first of its kind to directly show such a link between liver-produced molecules and pneumonia susceptibility during sepsis.
Led by researchers at Boston University School of Medicine (BUSM), the study appears in the journal Infection and Immunity.
Pneumonia, according to the World Health Organization, is the leading infectious cause of death in children worldwide, taking more than 900,000 lives of children under the age of 5 in 2013 alone. Pneumonia, ...
A new piece of research led by the University of Southampton has found that the behaviour of fruit flies, which are commonly used in laboratory experiments, is altered by electric fields.
The research indicates that the wings of the insects are disturbed by static electric fields, leading to changes in avoidance behaviour and the neurochemical balance of their brains.
The paper, published in the Proceeding of the Royal Society B, suggests that the plastic housing laboratory fruit flies are commonly kept in (which hold their own static electric charge) could agitate the ...
In a survey of hospital medical physicians across the United States, women made nearly $15,000 less than their male counterparts, with a portion of this disparity explained by female doctors' tendency to prioritize collegiality and control over personal time, rather than substantial pay. The figure was determined after controlling for a number of factors, including age, geography, specialty, and amount and type of clinical work.
Optimal workload was the top priority for both male and female physicians, 776 of whom responded to survey questions on work priorities. Substantial ...
A new study led by a University of York scientist addresses an important question in climate science: how accurate are climate model projections?
Climate models are used to estimate future global warming, and their accuracy can be checked against the actual global warming observed so far. Most comparisons suggest that the world is warming a little more slowly than the model projections indicate. Scientists have wondered whether this difference is meaningful, or just a chance fluctuation.
Dr Kevin Cowtan, of the Department of Chemistry at York, led an international study ...
July 30, 2015 - Some women with breast cancer can now undergo a "one and done" approach combining nipple-sparing mastectomy with immediate single-stage implant (SSI) breast reconstruction in a single procedure, according to a report in the July issue of Plastic and Reconstructive Surgery®, the official medical journal of the American Society of Plastic Surgeons (ASPS).
In the article, ASPS Member Surgeon Dr. Mark A. Codner of Emory University, Atlanta, shares his approach to single-stage implant (SSI) breast reconstruction after mastectomy for breast cancer. Coauthor ...
July 30, 2015 - More women are expressing interest in plastic surgery to restore a more youthful figure after having children. An update on combined procedures for postpartum body contouring--addressing the abdomen, breasts, and other problem areas--is presented in the August issue of Plastic and Reconstructive Surgery®, the official medical journal of the American Society of Plastic Surgeons (ASPS).
Sometimes called the "mommy makeover," postpartum body contouring combines a "tummy tuck"(abdominoplasty) with breast lift surgery (mastopexy) and other procedures to ...
Some 10-15 percent of combat veterans struggle with wounds invisible to the naked eye: post-traumatic stress. Their lives are ridden with debilitating symptoms: insomnia, flashbacks, depression, anxiety, guilt, and ever-present tension. While there is no cure-all for post-traumatic stress disorder (PTSD), cognitive behavioral therapy -- which actively reprocesses traumatic events to reduce symptoms -- has seen some success.
A new study from researchers at Tel Aviv University, Creighton University in Omaha, Nebraska, and the National Institute of Mental Health suggests ...
