At the Rehabilitation Institute of Chicago's (RIC) Neural Engineering Center for Bionic Medicine, researchers and doctors have been making improvements on their advanced prosthesis technology since fitting the first patient ever with the device five years ago. The bionic arm's movement is initiated neurologically, which allows increased natural movement and improved range of motion. Since the first fitting, the technology has also been improved to permit heightened sense of temperature through touch. According to this article:
To provide the neuro-controlled movement of RICs Bionic Arm technology, nerves located in the amputees shoulder, which once went to the amputated arm, are re-routed and connected to healthy muscle in the chest. This surgical process is called targeted muscle reinnervation. The muscle reinnervation procedure allows the re-routed nerves to grow into the chest muscle and direct the signals they once sent to the amputated arm instead to the robotic arm via surface electrodes. Then, when the patient thinks about moving his or her arm, the action is carried out as voluntarily as it would be in a healthy arm allowing for smoother and easier movement of the prosthetic.