Experimental assessment of imbalance conditions in a tripolar cuff for ENG recordings

Functional Electrical Stimulation (FES) may be improved by the use of naturally occurring nerve signals as feedback signals. However, the usefulness of the recorded electroneurogram (ENG) signals from nerve cuff electrodes depends on the amount of electromyogram (EMG) interference and stimulus artefact present. Tripolar cuff electrodes reduce interference but suffer from imbalance, which degrades the performance of amplifier recording configurations. Previously cuff imbalance has been mainly associated with impedance variations inside the cuff and cuff asymmetry. In this paper, imbalance is associated with additional factors, including cuff orientation and distance from the interference source. The findings are based on in-vivo and in-vitro experiments performed using a true-tripole amplifier recording system.