Research In Brief

Targeted muscle reinnervation in prosthetic arms: Amputees' remaining arm muscles can be "reinnervated" to produce enough signals to control an artificial arm in real time, according to data from five patients treated at the Rehabilitation Institute of Chicago published in the Feb. 11 Journal of the American Medical Association. In the study, five people with shoulder disarticulation or transhumeral amputations underwent targeted muscle innervations; transfer of the remaining arm nerves to residual chest or upper-arm muscles transforms the muscles into "biological amplifiers" of motor commands from the transferred nerves. The target muscles produce electromyogram signals on the surface of the skin that can control an artificial elbow, wrist and hand, according to study author Todd A. Kuiken, M.D./Ph.D., Neural Engineering Center for Artificial Limbs, et al. The patients in the study were able to repeatedly perform 10 different elbow, wrist and hand motions with their artificial arm. The mean motion selection and motion completion times for elbow and wrist movements were 0.22 seconds and 1.29 seconds, respectively. These times were only 0.06 seconds and 0.21 seconds longer than the mean time for five non-amputee patients enrolled as the control group. In an accompanying editorial, Gerald E. Loeb, University of Southern California's Departments of Biomechanical Engineering and Neurology, calls Kuiken's results "exciting and promising." Loeb adds: "Such revolutions develop slowly at best, but their effects tend to be profound. With increasing functional capabilities, patients with upper-extremity amputations may derive exceptional benefit from prosthetic arms, just as legions of patients with lower-extremity amputations now lead remarkably normal and even athletic lives.