Vibrotactile Feedback Improves Foot Placement Perception on Stairs for Lower-Limb Prosthesis Users.

Lower-limb amputees demonstrate decreased performance in stair ambulation compared to their intact-limb counterparts. An estimated 21% of amputees can navigate stairs without a handrail; almost 33% do not use stairs at all. The absence of tactile sensation on the bottom of the foot, creating uncertainty in foot placement, may be overcome by integrating sensory feedback into prosthesis design. Here we describe the design and evaluation of a haptic feedback system worn on the thigh to provide vibrotactile cues of foot placement with respect to stair steps. Tactor discrimination and foot placement awareness tests were performed to analyze system efficacy. Control participants wearing ski boots (N=10) and below-knee amputees (N=2) could discriminate individual tactor vibrations with 95.4% and 90.1% accuracy, respectively. The use of vibrotactile feedback increased accuracy in reporting foot placement by 15% and 17.5%, respectively. These results suggest that using vibrotactile arrays for sensory feedback may improve stair descent performance in lower-limb amputees.