Effect of Gel Type and Anode Selection in Ankle Movements Elicited by a Multi-field FES Device

Functional electrical stimulation (FES) is an evidence-based technique for treating foot drop, the inability to lift the foot due to weak or absent ankle dorsiflexors. Surface multi-field electrodes have brought some advantages such as improved selectivity or possibility of performing automatic motor-search configurations. In fact, they provide new stimulation paradigms that should be tested. This pilot study analyses the movements created using different anode combinations and gel types with the Fesia Walk system, a commercial multi-field technology-based FES device for foot drop compensation. 8 different anode combinations and 2 gel types were tested in 4 healthy subjects. Results show that the most lateral anodes located on the shank produce predominantly ankle plantarflexion and eversion, while the ones located most medially produce more dorsiflexion and inversion. No significant effect was observed between both gel types. This study suggests that anode selection has an influence on the elicited ankle movements and therefore it should be taken into account in the configuration process.