{"id":5427,"date":"2015-08-01T04:13:55","date_gmt":"2015-08-01T04:13:55","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=5427"},"modified":"2015-08-01T04:13:55","modified_gmt":"2015-08-01T04:13:55","slug":"a-cheaper-high-performance-prosthetic-knee","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/a-cheaper-high-performance-prosthetic-knee\/","title":{"rendered":"A cheaper, high-performance prosthetic knee"},"content":{"rendered":"

Researchers design cheap prosthetic knee that mimics normal walking motion.<\/strong><\/p>\n

\"Yashraj<\/a>
Yashraj Narang SM ’13 (right) conducted a comprehensive survey of above-knee amputees in India to understand their unique user-needs and the performance of their current prostheses.
Photo courtesy of the researchers.<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0In 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.<\/p>\n

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.<\/p>\n

\u201cWe\u2019re going after this disruptive opportunity,\u201d says Winter, an assistant professor of mechanical engineering at MIT. \u201cIf we can make a knee that delivers similar performance to a $50,000 knee for a few hundred dollars, that\u2019s a game-changer.\u201d<\/p>\n

Now Winter and his colleagues have taken a significant step toward that goal. In a paper published in IEEE\u2019sTransactions on Neural Systems and Rehabilitation Engineering,\u00a0<\/em>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.<\/p>\n

Using the paper\u2019s 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.<\/p>\n

\u201cIn places like India, there\u2019s still stigma associated with this disability,\u201d Winter says. \u201cThey may be less likely to get a job or get married. People want to be incognito if they can.\u201d<\/p>\n

The paper\u2019s co-authors include graduate student Murthy Arlekatti and Yashraj Narang, a PhD student at Harvard University.<\/p>\n

Tuning torque<\/strong><\/p>\n

Most amputees in developing countries wear passive prostheses \u2014 simple, cheap designs with no moving parts. \u201cWhen you see people walk in them, they have a pretty distinctive limp,\u201d Winter says. In part, that\u2019s 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 \u2014 a shift in torque that keeps a person\u2019s center of mass steady. In contrast, a stiff, unbending prosthetic knee would cause a person to bob up and down with each step.<\/p>\n

\nWinter 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\u2019s gait, including the angle of their joints, the weight of each leg segment, and the ground reaction force \u2014 the force between the ground and the foot \u2014 during a single step, or gait cycle.<\/p>\n

The researchers used the measurements to calculate a torque profile \u2014 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.<\/p>\n

\u201cIf you applied healthy levels of torque to a much lighter limb, your kinematics would get all screwed up,\u201d Winter says. \u201cRobotic 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?\u201d<\/p>\n

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.<\/p>\n

Winter\u2019s team is now testing the design with volunteers in India.<\/p>\n

\u201cThis was a quick and dirty prototype, but so far, we\u2019re seeing good indicators of natural gait,\u201d Winter says. \u201cI\u2019m not ready to claim victory yet, but [this paper] lays out a roadmap that is very different than what\u2019s been done before, which will enable us to achieve very high performance at low cost. And that\u2019s what we\u2019re going after.\u201d<\/p>\n

This research was funded, in part, by the National Science Foundation.<\/p>\n

\\<\/p>\n","protected":false},"excerpt":{"rendered":"

Researchers design cheap prosthetic knee that mimics normal walking motion. CAMBRIDGE, Mass. —\u00a0In 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 […]<\/p>\n","protected":false},"author":2,"featured_media":5428,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-5427","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Prosthetic-Knee-1_0.jpg",150,100,false]},"author_info":{"info":["RevoScience"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5427","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=5427"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5427\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/5428"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=5427"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=5427"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=5427"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}