Sensory feedback restoration in leg amputees improves walking speed, metabolic cost and phantom pain

Abstract

Despite advances in the development of lower-limb prosthetics, the potential benefits of restoring sensory feedback from such devices to transfemoral (above-knee) or transtibial (below-knee) amputees has not been investigated. Most surgery techniques and noninvasive methods to restore sensory feedback have been tested only in transtibial amputations, which produce a less disabling clinical condition than transfemoral amputation. Direct neural stimulation through transversal intrafascicular multichannel electrodes (TIMEs) has enabled upper-limb amputees to feel touch sensations from the missing hand and to exploit them for long-term prosthesis control. Only a few trials with direct nerve stimulation that did not show clear benefits for the leg amputees have been conducted. Restoring sensory feedback from the phantom hand of upper-limb amputees through neural stimulation has been shown to decrease phantom limb pain (PLP). However, the efficacy of low-frequency nerve stimulation has never been investigated for treating PLP in leg amputees. In this study, we recruited two volunteers with transfemoral amputation as a consequence of traumatic events (Supplementary Table 1). These volunteers were implanted with four TIMEs in the nearest portion of the residual tibial nerve to the amputation for more than 90 d each (top right in Fig. 1 and Extended Data Fig. 1).