Prosthetic Elbow Flexion and Extension Sense rebuilt by Electrotactile Feedback: a Preliminary Study

Abstract

The elbow position and movement (PM) feedback can help amputees control the prosthetic limbs more flexibly. This study attempts to explore whether electrotactile stimulation can help amputees identify the elbow PM information of prosthesis, due to valuable potential of electrotactile stimulation. This study designed an encoding scheme by relating the elbow PM information with amplitudes, and it tested the scheme on four able-bodied subjects and two transhumeral amputees. After two stimulation positions on the upper limb were determined using sensory sensitivity experiment, four sets of amplitudes (Am, An) were encoded four positions of prosthetic elbow (0°, 45°, 90°, and 135°) and changes in sets of amplitudes were encoded flexion and extension (FE) movements of prosthetic elbow. All subjects were required to identify the prosthetic elbow PM during the experiment, and the success rate and discrimination reaction time were recorded. The average success rates of the position and movement experiments among the four subjects were 76.25% and 91.17% respectively. For the two transhumeral amputees, the position feedback success rates were 86.38% and 75%, respectively, and the movement feedback success rates were 80.5% and 75%, respectively. These results indicate that subjects can learn the mapping relationship of this sensory feedback after training. This method potentially in future provides amputees with PM sensory information of elbow FE during the actual control of prosthetic elbows.