Bionic hands controlled by new "minimuscles" implanted in the wearer's arm

Many of today's bionic limbs are "myoelectric," controlled by electrodes attached to theresidual limb that pick up impulses generated when the wearer consciously contracts that muscle. Those systems aren't without their challenges though, such as a disruption in the signal when the wearer sweats or the prosthetic and sensors shift around on the skin. Now, University of Michigan bioengineers have developed what may be a more durable approach: they implant the wearer with new "minimuscles," tiny muscle grafts from their own tissue that are monitored by electrodes inserted into the skin. From Science:

The researchers isolate bundles of fibers from each of the major nerves in the arm and wrap each bundle in a chunk of muscle tissue roughly the size of a paper clip, often harvested from the thigh. The process basically creates a new set of finger muscles inside a persons forearm or bicep.

Because wrapping nerves this way also relieves certain types of pain common after an amputation, hundreds of people have already had the procedurebut without the wire implants that could record from the muscles to control a prosthesis. In a new study out today in Science Translational Medicine, Cederna and UM neural engineer Cynthia Chestek describe the first test of that control step.

In three participants with amputations at different points along the arm who already had muscle implants, wires inserted through the skin near the muscle grafts could easily pick up their electrical signals, the researchers report. Even with an amputation up near the shoulder, a computer could interpret which tiny muscles were contracting, and by how much, to isolate different intended movementsa flex of the pointer finger versus the thumb, for example.