Author Affiliations: Departments of Biomedical Engineering and Neurology, University of Southern California, Los Angeles.
Prosthetic limbs aim to replace what is most obviously missing—the mechanical function and physical appearance of bones, muscles, and skin. Mechatronics—the fusion of advanced motors, electronics, and servocontrol and power systems—is enabling the development of highly articulated prosthetic limbs capable of complex movements. But still missing are the parts that cannot be seen—the bidirectional flow of information between the limb and the central nervous system, which enables dexterous movements.1 The absence of interfaces with the nervous system has been less of a problem for advanced lower-extremity prostheses, because the functional abilities of these prostheses are much more limited and because these devices can take cues by sensing mechanical events initiated by the intact parts of the body (eg, stump and contralateral leg).2 Failure to develop practical neural interfaces for command and sensation in the upper extremity will lead to a repeat of the early disappointment with myoelectric arms.3 Those limbs were (and continue to be) difficult to control, requiring intense user concentration to move one joint at a time with little or no control of velocity or force.
Loeb GE. Taking Control of Prosthetic Arms. JAMA. 2009;301(6):670-671. doi:10.1001/jama.2009.112