Robotic Knee Offers new Hope for Amputees, Study Finds
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A groundbreaking study reveals that a commercially available robotic knee can significantly improve mobility and reduce strain for amputees, perhaps paving the way for wider clinical adoption and insurance coverage. For the first time, researchers have demonstrated tangible benefits of a powered prosthetic leg for both individuals with higher and lower activity levels. The gains were most pronounced when paired with a novel control strategy developed by a team at the University of Michigan,resulting in a more natural gait,decreased risk of falls,and reduced stress on sound limbs and hips.
Bridging the Gap Between Passive and Powered Prosthetics
While lightweight and simple passive prosthetic legs remain popular, they often fall short during demanding activities like climbing stairs, navigating hills, or walking long distances. Powered prosthetics offer a solution, but until now, concrete evidence of their superiority over advanced passive models has been lacking – a key barrier to both adoption and insurance reimbursement.
“Our study is meaningful as evidence was previously lacking for benefits of robotic knees over advanced passive knees, which is a big reason insurance companies don’t typically cover robotic knees,” explained a senior researcher involved in the project. “Our results begin to provide this evidence.”
The research, conducted in collaboration with Össur and funded by the National Institutes of Health, focused on key daily activities – sitting and standing, treadmill walking, and repeated transitions between sitting and walking. Participants, utilizing Össur’s Power Knee, underwent testing with both the manufacturer’s standard control system and the University of Michigan’s innovative algorithm.
A New Control Algorithm for More Natural Movement
The team investigated two distinct approaches to controlling the robotic knee. Össur’s existing system relies on recognizing specific movements to anticipate the user’s intentions. while safe and predictable, this method can sometimes lag behind the user’s actual needs.
In contrast, the algorithm developed by the University of Michigan team continuously adapts to the user’s motion, leveraging mathematical models of human movement based on data from individuals without impairments. By measuring thigh motion in real-time, the system creates more fluid and synchronized knee movements.
“Our goal in prosthesis control is to make the leg behave as close as possible to the missing human limb in order to prevent compensations that often lead to overuse injuries,” stated a research associate and first author of the study. “It also matters because gait deviations can bring unwanted attention to some users.”
Real-World Improvements and Future Directions
The study revealed significant improvements for all participants,but the benefits were especially striking for those with greater mobility. These individuals exhibited a higher prosthetic foot lift – reducing tripping hazards – and decreased hip swing,potentially alleviating back pain and increasing endurance. One recent amputee described the experience as feeling “the closest they’d felt to two-legged walking on a prosthesis.”
Notably, the improvements observed with Össur’s own control algorithm were substantial enough that two participants opted to switch to the Power Knee for their everyday use, demonstrating a tangible shift towards real-world application.
The team is now preparing for further testing, focusing on stairs and ramps, and also extended take-home trials. If successful, aspects of the University of Michigan’s control strategy could be integrated into Össur’s existing algorithm.
“With the improvements in robotic devices, it is indeed clear that robotic prostheses offer great promise to the amputee population,” commented a certified prosthetist/orthotist and study coauthor. “I am excited to see the advancement of a strategy to provide powered prosthesis users with user-synchronized control. I believe that this is a missing link to making powered prosthetics a reality for amputees.”
The research was primarily funded by the National Institutes of Health (award No. R01HD094772), with additional support from the National Science Foundation. Össur provided initial financial support and holds a potential financial interest in the results. The team has filed for patent protection for their controller with the assistance of U-M Innovation Partnerships.
