The Challenge of Robotic Prosthetics

While several robotic prosthetic legs are currently available, widespread clinical adoption remains limited. Many users still prefer the simplicity and lightweight nature of traditional, passive prostheses. However, passive legs can be particularly challenging during demanding activities like ascending stairs, navigating hills, or undertaking long walks, potentially leading to overuse injuries. Powered prosthetics offer a solution, but until now, definitive evidence of their superiority over advanced passive knees has been lacking – a key barrier to insurance coverage and broader acceptance.

A New Control Strategy for Natural Movement

The research, conducted at the University of Michigan in collaboration with Össur, focused on refining the control systems of the Power Knee. The team investigated two distinct approaches. Össur’s existing controller 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 team developed a novel algorithm that continuously adapts to the user’s motion, building upon mathematical models of human movement derived from extensive datasets of unimpaired individuals.

“Our goal in prosthesis control is to replicate the natural function of a missing limb as closely as possible,” explains Kevin Best, a research associate in robotics and the study’s first author. “This minimizes compensatory movements that can cause overuse injuries and also addresses the social aspect – gait deviations can sometimes draw unwanted attention.”

Real-World Benefits Demonstrated

The study involved participants performing everyday tasks such as sitting and standing, walking on a treadmill, and transitioning between sitting, walking, and standing repeatedly. Those who typically used a cane for assistance experienced significant improvements across all activities with the Power Knee. However, the most dramatic gains were observed in participants with higher mobility when paired with the team’s new control algorithm. One recent amputee described the experience as the closest they’d felt to walking with two natural legs.

Specifically, the algorithm enabled participants to lift their prosthetic foot higher, reducing the risk of tripping, and minimized the amount of hip swing required for forward motion. This suggests a potential for reduced back pain and increased endurance, although further research is needed to confirm these benefits. What impact do you think more natural prosthetic movement will have on the psychological well-being of amputees?

Jeff Wensman, a certified prosthetist/orthotist at Michigan Medicine and study coauthor, emphasizes the significance of this advancement: “I am excited to see the development of a control strategy that synchronizes with the user. This is a missing link in making powered prosthetics a viable option for a wider range of amputees.”

The team is now focusing on testing the algorithm’s performance on stairs and ramps, with plans for real-world, take-home trials. Össur is also exploring the possibility of incorporating aspects of the new control strategy into its existing Power Knee technology. Interestingly, two participants in the study have already opted to switch to the Power Knee for their daily use, a testament to the tangible benefits observed.

Further research into robotic prosthetics can be found at the Johns Hopkins Center for Prosthetics and Orthotics.

Frequently Asked Questions About Robotic Knees

1. What are the primary benefits of a robotic knee prosthesis?
   Robotic knee prostheses offer increased power and assistance during activities like walking, climbing stairs, and standing, potentially reducing strain and improving endurance.
2. How does the new control algorithm improve prosthetic leg function?
   The algorithm continuously adapts to the user’s motion, creating more natural and synchronized knee movements compared to traditional controllers that rely on anticipating the user’s intent.
3. Is insurance coverage typically available for robotic knees?
   Insurance coverage for robotic knees has historically been limited due to a lack of conclusive evidence demonstrating their superiority over advanced passive knees. This research aims to provide that evidence.
4. What types of activities were used to test the robotic knee in this study?
   Researchers focused on key activities of daily living, including sitting and standing, treadmill walking, and repeated transitions between sitting and walking.
5. What are the next steps in the development of this technology?
   The team plans to test the algorithm on stairs and ramps, conduct take-home trials, and potentially integrate it into Össur’s Power Knee.
6. How does this new technology address the social concerns of prosthetic users?
   By promoting a more natural gait, the algorithm can minimize noticeable deviations in walking patterns, potentially reducing unwanted attention.
7. What role did Össur play in this research?
   Össur provided the Power Knee prosthetic leg and initial financial support for the study, and may have a financial interest in the results.