A review of the design and clinical evaluation of the ShefStim array-based functional electrical stimulation system

Abstract

Functional electrical stimulation has been shown to be a safe and effective means of correcting foot drop of central neurological origin. Current surface-based devices typically consist of a single channel stimulator, a sensor for determining gait phase and a cuff, within which is housed the anode and cathode. The cuff-mounted electrode design reduces the likelihood of large errors in electrode placement, but the user is still fully responsible for selecting the correct stimulation level each time the system is donned. Researchers have investigated different approaches to automating aspects of setup and/or use, including recent promising work based on iterative learning techniques. This paper reports on the design and clinical evaluation of an electrode array-based FES system for the correction of drop foot, ShefStim. The paper reviews the design process from proof of concept lab-based study, through modelling of the array geometry and interface layer to array search algorithm development. Finally, the paper summarises two clinical studies involving patients with drop foot. The results suggest that the ShefStim system with automated setup produces results which are comparable with clinician setup of conventional systems. Further, the final study demonstrated that patients can use the system without clinical supervision. When used unsupervised, setup time was 14 minutes (9 minutes for automated search plus 5 minutes for donning the equipment), although this figure could be reduced significantly with relatively minor changes to the design.

Advances in neuroprosthetic management of foot drop: a review

“…The current trend is to use electrode arrays combined with a self-calibration system that allows the proper selection of virtual electrodes to achieve an optimal dorsiflexion movement, avoiding an eversion or inversion of the ankle during the same process. Examples of this type of systems are the ShefStim [45][46][47][48][49] and DeltaStim [66]. Moreover, although stimulation by implanted electrodes allows assistance to be applied in a more specific way, the use of virtual electrodes selfcalibrate strategies could become an effective noninvasive alternative.…”

“…Results show increased walking speed (from 10 to 23, or 36%), reduction in walking effort (Borg scale score~9), improved dorsiflexion and reduced inversion at the initial contact. In addition, this work was the first in demonstrating the feasibility of using an FES system outside of the laboratory environment without technical support[45][46][47][48][49].…”

Myoelectrically Controlled FES to Enhance Tenodesis Grip in People With Cervical Spinal Cord Lesion: A Usability Study

“…It should be considered that, stimulation is activating the nerves rather than the muscle fibers themselves, that the flexor digitorum superficialis comprises four compartments with respective nerve branches, that flexors are composite muscles with variations in innervation (radial vs. median nerve) and finally the possibility of anatomical variations (Yammine and Erić, 2018). These issues combined with varying degrees of residual control of intrinsics and finger extensors makes it difficult to predict the stimulated hand function without actually stimulating at various points (Kenney et al, 2016). Moreover, racial variations are likely to exist (Al-Qattan, 2010), which calls for studies in other parts of the world.…”

Conformable Electrode Arrays for Wearable Neuroprostheses

“…Such activation is achieved by shaping a cathode across a subset of electrodes in an array. Thus, wearable neuroprostheses deploy electrode arrays to stimulate forearm muscles by integrating them into a sleeve [ 2 , 3 ]. However, such systems have limited user acceptance due to challenges in achieving selective activation (due to the complex musculature of the forearm) and poor control with transcutaneous delivery of charges [ 4 , 5 ].…”