Augmenting gait in a population exhibiting foot drop with adaptive functional electrical stimulation

Functional electrical stimulation (FES) can be used for improvement of gait in people with foot drop resulting from neurological disease or injury. However, existing FES solutions suffer from significant limitations. First, fixed placement electrode devices are difficult to tune stimulation for improved ankle dorsiflexion while maintaining balanced ankle eversion. Second, standard tilt-sensor-like triggers do not allow for adaptive, configurable stimulation sequencing algorithms. Here, we introduce the first FES system with adaptive current steering for an array of FES electrodes enabling precise control over dorsiflexor and evertor muscles, allowing for personalized treatment to correct key foot drop characteristics including dorsiflexion at heel strike and ankle inversion during swing phase. We share results of a pre-test, post-test study on thirty-two participants exhibiting symptoms of foot drop. The differences in pre-test versus post-test primary and secondary outcome measures were statistically significant (p<0.0125) within our cohort. With adaptive, current-steering FES, ankle dorsiflexion at heel strike increased an average 5.2°, and ankle inversion during swing phase was reduced by an average -3.6°, bringing the ankle to a more neutral position for stabilization. By significantly increasing ankle dorsiflexion at heel strike and decreasing ankle inversion during swing phase, adaptive FES enabled a more neutral ankle at heel strike, which is associated with greater ankle stability and decreased fall risk. Gait augmentation using adaptive, current-steering FES improved gait in a population exhibiting symptoms of foot drop.