Electrically-evoked control of the swinging leg after spinal cord injury: open-loop or motion sensor-assisted control?

In paraplegics, gait can be restored by means of functional electrical stimulation (FES). Because the electrophysiological responses of the lower limbs to the neuromuscular stimulus are not completely deterministic, several stimulation strategies have been reported in an attempt to refine stepping motion. In open-loop (OL) systems, the electrical stimulation sequences applied over the leg muscles are often tuned for each patient in order to improve the quality of gait. Our aim was to contrast this traditional technique against variable stimulation sequences based on motion sensors (MS) data feedback. Both strategies were tested over 240 stepping trials in three complete paraplegics. In comparison to OL, which used a customised stimulation sequence for each subject, the same MS strategy was as functional for all three subjects. Despite MS producing a lower variability on step lengths, the toe clearances had a similar pattern of variability regardless of the strategy applied. Although the novel MS showed promising results, the reliability of OL was also demonstrated. Therefore, we still recommend the use of OL mainly due to its faster donning and doffing, since this is a matter of importance for the user acceptance of any rehabilitation systems.