Prosthetic Arm

A new technique that capitalizes on remaining nerves allows amputees to intuitively control their prosthetic limb, providing them with a much better level of control than traditional prosthetics.
Scientists describe a procedure to surgically transplant nerves from the shoulder to the upper-chest muscle.
The rerouted nerves then grew into the muscle, which amplified the messages once sent to muscles in the arm and hand; those signals are read by sensors on the prosthetic limb and translated into movement. The patient also developed a surprising degree of sensory perception in the upper chest, which scientists say will be key in the next generation of prosthetics.
Most artificial arms are controlled by remaining muscles near the amputated limb. But the devices can be frustrating and slow: the user must consciously contract those muscles to trigger a movement, and only one movement can be performed at a time.

The scientists transplanted to the upper chest both motor and sensory nerves that, prior to the amputation, would have traveled from the shoulder to muscles in the arm and hand. In the months after the surgery, the transplanted nerves grew into the chest muscle, eventually triggering twitches in the shoulder muscle when the patient thought about moving her hand or elbow. Scientists then mapped the precise pattern of muscle activity that occurred when the patient mentally executed specific movements, such as grasping or moving the elbow. Liberating Technologies, a prosthetic-device company, then made a specialized prosthetic limb, which was programmed to sense muscle activity generated by the transplanted nerves and use it to control movement of a motorized elbow, wrist, and hand.

The patient was able to use her new arm within a few days, becoming four times as fast on movement tests as she was with her traditional prosthetic.