Quirks & Quarks

Building a better cyborg leg — adding a sense of touch to artificial limbs

Users were surprised and pleased to be able to feel their prosthetic

Users were surprised and pleased to be able to feel their prosthetic

Volunteer (Djurica Resanovic) with his prosthetica and researchers, from left to right, Stanisa Raspopovic, Francesco M. Petrini, Giacomo Valle (Federica Barberi)

European researchers have developed a prosthesis that restores the sense of touch for lower leg amputees by artificially stimulating the residual nerves in the upper thigh. 

Djurica Resanovic, who lost his lower right leg in a motorcycle accident years ago, was astonished after trying on the prosthesis.

 "It was very interesting, it's like my own leg. First time I feel my leg, I feel my foot." 

One of the major problems with current prosthetic technology is that users can't feel them. They don't trust the prosthesis to help them get around, and so rely more on their functional limb to move. This puts additional stress on that limb and ultimately impedes their mobility, increases their risks of heart and bone diseases, and decreases their quality of life. 

Volunteer recognizes where the prosthesis foot sole is touched. (Francesco M. Petrini)

Dr. Stanisa Raspopovic, who led the research, has been working to solve this problem for a decade. He works on neural interfaces —  systems that can tie nerves into machines. The prosthesis he developed provides nerve stimulation to the user by converting sensory signals provided by sensors placed in the prosthetic knee and insole underneath the prosthetic foot, to neural signals that the brain understands to convey the sensations of pressure and balance.

In a small preliminary trial with three volunteers, the neuro-prosthesis has improved the mobility and agility of users while they performed difficult tasks such as climbing stairs or walking on uneven ground. They were able to climb stairs 30 per cent faster, and were less likely to stumble when navigating tricky terrain that they could not see. Users' minds were also noted to be more at ease when they could feel the ground with sensory feedback provided to them compared to no feedback. 

Going forward, Raspopovic wants to undertake a larger clinical study to confirm the findings of this preliminary study, with the goal of eventually bringing the device to the broader public. 

 

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