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Approximately one million Americans have a lower-limb amputation. For these individuals walking with a prosthesis is slower, more asymmetric, less stable, and requires more metabolic energy than for people with intact limbs. This is largely because most available prostheses are passive, that is they don’t provide the power that would be provided by an intact knee and ankle during walking.
In the United States, older individuals make up over 90% of persons with a lower-limb amputation. These individuals need assistance getting out of chairs and off the toilet, in addition to walking the short distances necessary for them to live independently at home.
Lower-limb prostheses that can provide power are being developed, but are designed for younger users and are too heavy for the limited stability and strength of older individuals. Older people need powered legs that provide power to help them get out of a chair, yet light enough to use while walking without affecting balance.
With funding from our first RERC, we have designed a lightweight powered leg with innovative knee and ankle designs that significantly reduce weight and noise while providing necessary power only when needed.
Hybrid Knee
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The knee has a novel active variable transmission (AVT) that adapts motor power and speed based on the requirement of different activities. This means that the knee does not provide power when the user is walking on level ground, but provides maximum power when needed, for example, when going from sitting to standing or climbing stairs. Because the motor is only used when needed, we can use smaller, lighter motors than used in legs that provide power all the time. And the prosthesis is quieter because the motor is off most of the time.
Adaptive Ankle
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Our lightweight ankle-foot uses a novel non-backdrivable cam-based transmission to actively control the ankle position during non-weight-bearing activities, e.g., when the leg is off the ground during swing phase. Like the knee described above, this passive/powered hybrid adaptive ankle uses a smaller motor and batteries than a fully powered device.
Next Steps
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As part of our original RERC funding, we began preliminary testing of the knee and ankle in the lab, by people without amputations (using a bypass device).
With funding from our new RERC, we will test the leg in individuals with leg amputations at the transfemoral (thigh) level and compare it to a commercially available, lightweight passive prosthetic leg (the C-Leg Compact by Ottobock). We will compare how people walk with each leg, and the amount of metabolic energy the use when walking with each device.
We expect that our leg will allow people to walk more normally (which reduces the risk of injuries) and with lower energy requirements, making it suitable for older people.
We will also test whether electrical signals generated by contraction of leg muscles in the residual limb can be used to control the prosthesis when the person is not walking on it. The electrical signals (called EMG signals) are recorded and analyzed by a built-in computer on the leg, which then prepositions the leg to, for example, transfer into or out of a vehicle or stand from a sitting position, or to reposition the leg for comfort.
Publications & Presentations
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Papers
Lenzi T, Cempini M, Hargrove LJ, and Kuiken TA. “Hybrid Actuation Systems for Lightweight Transfemoral Prostheses” ASME Journal of Medical Devices, 2017 (special issue from Design of Medical Device Conference 2017).
Lenzi T, Cempini M, Sensinger JW, Hargrove LJ, and Kuiken TA, “Design, Control, and Preliminary Validation of a Robotic Retrofit for Knee Prostheses” IEEE Transactions on Robotics.
Lenzi T, Cempini M, Hargrove LJ, and Kuiken TA, “A Hybrid Robotic Knee Prosthesis with Actively Variable Transmission” International Journal of Robotics Research.
Lenzi T, Cempini M, Hargrove LJ, and Kuiken, TA. “A Lightweight Robotic Ankle Prosthesis with Non-Backdrivable Cam-based Transmission” IEEE/ASME Transactions on Mechatronics.
Conference Presentations
Lenzi T, Sensinger JW, Lipsey J, Hargrove L, Kuiken TA. (Poster presentation) “The RIC hybrid knee prosthesis” IEEE International Conference on Robotics and Automation (ICRA 2015), May 26-30, 2015, Seattle, WA.
Lenzi T, Sensinger JW, Lipsey J, Hargrove LJ, Kuiken TA “Design and Preliminary Testing of the RIC Hybrid Knee Prosthesis” 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, August 25-29 2015, Milan, Italy.
Cempini M, Hargrove LJ, Kuiken TA, and Lenzi T. “Design of a Polycentric Powered Ankle Prosthesis” 38th International conference of the IEEE Engineering in Medicine and Biology Society, August 16-20, 2016, Orlando, FL.
Lenzi T, Cempini M, Hargrove LJ, and Kuiken TA. “Actively Variable Transmission for Powered Knee Prostheses.” IEEE International Conference on Robotics and Automation (ICRA 2017), May 29 to June 3, 2017, Singapore.
Design, control, and preliminary testing of the RIC Adaptive Ankle with an able-bodied subject IEEE International Conference on Rehabilitation Robotics (ICORR) London, July 17-20 2017.
Lenzi T, Cempini M, Hargrove LJ, and Kuiken TA. “Actively Variable Transmission for Powered Knee Prostheses.” IEEE International Conference on Robotics and Automation (ICRA 2017), May 29 to June 3, 2017, Singapore.
Lenzi T, Cempini M, Newkirk J, Hargrove LJ, and Kuiken TA. “A Lightweight Robotic Ankle Prosthesis with a Novel Non-backdrivable Transmission.” IEEE International Conference on Rehabilitation Robotics (ICORR 2017), July 10 to July 17, 2017, London.
Cempini M, Hargrove LJ, Lenzi T. “Design, Development, and Bench-top Testing of a Powered Polycentric Ankle Prosthesis.” IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2017), September 24 to September 28, 2017, Vancouver – Manuscript on design and validation of the polycentric architecture of the RIC Active Ankle (generation 2).
Lenzi T, Cempini M, Hargrove LJ, and Kuiken TA. “Hybrid Actuation System for Lightweight Transfemoral Prostheses.” podium presentation Design of Medical Devices Conference, April 10 - 13, 2017, Minneapolis.
Patents
Powered and Passive Assistive Device and Related Methods. Kuiken T, Lipsey J, Lenzi T, Cempini M. Application # 14/962,982 A1; Publication Date June 9, 2016. (US and PCT)
Polycentric Powered Ankle Prosthesis. Lenzi T, Cempini M, Kuiken T. application # 17/26703. (US and PCT)
Lead Study Personnel
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Levi Hargrove, PhD (Principal Investigator)
Ann Simon, PhD
Mentioned Profile
Annie Simon, PhD
Engineering ManagerBody
The contents of this webpage were developed under grants from the National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR grant numbers 90RE5014 (2013-2018) and 90REGE0003 (2018-2023). NIDILRR is a Center within the Administration for Community Living (ACL), Department of Health and Human Services (HHS). The contents of this webpage do not necessarily represent the policy of NIDILRR, ACL, or HHS, and you should not assume endorsement by the Federal Government.