The Mind-controlled Arm Prosthesis
A sensational new development from Otto Bock can be seen for the first time in Germany at the ORTHOPÄDIE + REHA-TECHNIK trade fair: A prototype of the unique mind-controlled arm prosthesis. The first user of the intelligent arm outside of the USA is the young Christian Kandlbauer (Steiermark, Austria) who has both arms amputated and is now working again at his former employer as a warehouse clerk.
After an amputation of an arm, the nerves are functional up to the amputation point. These nerves can grow into a new muscle and bring about contraction. This principle is nature’s “repair mechanism” where the lost ability for muscle contraction is restored.
The idea of Targeted Muscle Reinnervation (TMR) involves artificially introducing this repair mechanism. A muscle that no longer functions due to an amputation is surgically divided into several segments. The original supply of nerves of this muscle is separated and used for growing the nerve ends. This procedure is called targeted reinnervation. After reinnervation, the muscle contracts according to a new scheme that relates to the movement of the phantom arm. If the prosthesis follows the same movement exactly as the phantom arm, it is referred to as intuitive control: The prosthesis user controls the prosthesis with his mind.
Surgery must be carefully planned. Patience is required after surgery as the nerves must first grow in the new muscles. This takes about one day per millimetre. A targeted muscle build-up starts after three to six months according to current knowledge.
After this training, the patient can control a prosthesis with a considerably higher degree of functionality. The orthopaedic technician produces a prosthesis socket that securely fixes the prosthesis to the body. The socket should restrict the patient as little as possible and ensure that the electrode contacts for EMG conductance lie securely on the skin. The artificial arm is attached to the socket and covered cosmetically.
Artificial arms that exploit the described usage to the full extent exist as prototypes. The patient uses a modified standard prosthesis as an everyday prosthesis that consists of serial parts. This arm has only three active joints but enables the patient intuitive control and provides a significantly higher usage.