Todd Kuiken: A prosthetic arm that "feels"

Summary

Todd Kuiken describes bionics—the use of mechatronic devices to replace or restore parts of the body—and focuses on improving prosthetic arms for people with upper-limb amputations. Losing an arm can affect everyday function, emotional well-being, and social interaction.

Traditional body-powered prostheses use shoulder movement and cables to operate a hand, hook, or elbow. Myoelectric prostheses use electrical activity from muscles to control motors. These can work intuitively after a hand amputation, but people with higher-level amputations may have too few usable muscles and must operate several joints through slow, awkward control sequences.

Targeted reinnervation

Kuiken’s team developed targeted reinnervation to make prosthetic control more natural:

• Nerves that once served the missing arm are redirected into selected chest muscles.
• The nerves grow into the muscles, which amplify their signals.
• When a person thinks about moving the missing hand or elbow, corresponding muscle regions contract.
• Electrodes detect these signals and use them to control the prosthesis.

Patients in the talk could control multiple joints more intuitively and simultaneously. Kuiken reported a high success rate for the nerve transfers, along with faster and easier performance on functional tests. Amanda Kitts described the system as more natural than her earlier prosthesis, which required her to switch between controls by contracting her biceps and triceps.

Pattern recognition and sensory feedback

The team also used pattern-recognition algorithms, similar to those used in speech recognition. They recorded muscle-signal patterns while patients attempted different movements, then trained a computer to interpret those patterns. This enabled control of more functions, including elbow movement, wrist rotation and flexion, and hand opening and closing.

The team found that redirected sensory nerves could make touch on the chest feel as if it came from the missing hand. In experiments, a sensor on a prosthetic hand pressed on reinnervated skin, allowing a participant to perceive different textures. Another demonstration used pressure on the skin to convey how firmly the prosthetic hand was squeezing.

These were early experiments in restoring sensation. The team noted that placing sensors and motors near the electrodes created technical challenges.

Future goals

The research team aims to:

• Develop small implanted devices that transmit muscle signals, reducing reliance on skin electrodes.
• Make more space for sensory-feedback components.
• Build a smaller, lighter prosthetic arm, beginning with a design sized for a smaller adult user.
• Improve the hand, wrist, and elbow while making the device practical for everyday clinical use.

Researchers and sources featured

• Todd Kuiken — surgeon and engineer presenting the work.
• Dr. Greg Dumanian — performed the targeted-reinnervation surgery described in the talk.
• Dr. Annie Simon — helped repair the demonstration arm before the talk.
• University of New Brunswick colleagues — collaborators on the pattern-recognition control algorithm.
• DEKA Research Corporation — maker of an advanced prosthetic arm demonstrated by Amanda Kitts.
• Dean Kamen — cited as having presented the DEKA arm at TED.

Patients and demonstration participants mentioned: Jesse Sullivan, Chris, Amanda Kitts, and Claudia.