This new type of intelligent arm prosthesis represents a quantum leap in prosthetic treatment. It is controlled by the nerves that originally moved the healthy arm. In this way, an entire pattern of movement can be made intuitively with the prosthesis, which currently features three active joints.
If the nerve endings in the amputee's residual arm still are intact, they can be re-used for functional purposes. Following a surgical procedure, the nerves grow into the target muscle and transfer their neuronal signals to that muscle. This is aided by a natural repair mechanism that restores the amputee's ability to contract the muscle. TMR (targeted muscle reinnervation) is based on the idea of using the target muscle as a natural amplifier for neuronal signals when the severed nerve endings grow into the muscle. Once re-attached to the nerves, the muscle contracts according to the movement pattern of the phantom arm (i.e., the imagined sensation of the missing arm). A minicomputer in the prosthesis transfers the movement pattern of the phantom arm to the prosthetic arm. If the prosthesis performs the exact same movements as the phantom arm, the patient can be said to control the prosthesis intuitively, i.e., with his or her mind.
This new type of prosthetic technology eliminates the relearning process normally required with conventional myo-electrically controlled prosthetics. Thanks to the natural movement pattern between the phantom arm and the prosthesis, the prosthetic arm feels more like a replacement limb and takes on an entirely new quality.