Kinesthetic Sensing for the EMG Controlled "Boston Arm"

The contribution of a novel cutaneous display of elbow angle to an amputee's ability to position an EMG-controlled externally powered elbow prosthesis was objectively evaluated. Comparisons were made between the amputee's positional control of his conventional mechanical cable-operated elbow and the EMG "Boston Arm"l elbow, with and without angle feedback, in REACHING tasks with vision occluded in all cases and with and without auditory occlusion. MATCHING tasks compared his ability to position the EMG limb to conform with the flexion of his normal (contralateral) elbow. Computer reduction of almost 9000 individual trials and analysis of variance indicated that for the EMG limb the tactile feedback with sound occluded reduced errors by 50 percent. Terminal device load did not significantly affect positioningperformance due to the force proprioception built into the Boston Arm. In comparison with the standard mechanical prosthesis, the EMG limb with feedback achieves virtually identical kinesthetic performance. The display is completely compatible with the EMG control, causes no discomfort to the wearer, and is not significantly degraded by the environmental conditions of the limb socket.