Neurological conditions like hemiplegia following stroke or tetraplegia following spinal cord injury, result in a massive compromise in motor function. Each of the two conditions can leave individuals dependent on caregivers for the rest of their lives. Once medically stable, rehabilitation is the main stay of treatment. This article will address rehabilitation of upper extremity function. It is long known that moving the affected limb is crucial to recovery following any kind of injury. Overtime, it has also been established that just moving the affected extremities does not suffice, and that the movements have to involve patient’s participation, be as close to physiologic movements as possible, and should ideally stimulate the entire neuromuscular circuitry involved in producing the desired movement. For over four decades now, functional electrical stimulation (FES) is being used to either replace or retrain function. The FES therapy discussed in this article has been used to retrain upper extremity function for over 15 years. Published data of pilot studies and randomized control trials show that FES therapy produces significant changes in arm and hand function. There are specific principles of the FES therapy as applied in our studies: (i) stimulation is applied using surface stimulation electrodes, (ii) there is minimum to virtually no pain during application, (iii) each session lasts no more than 45–60 min, (iv) the technology is quite robust and can make up for specificity to a certain extent, and (v) fine motor function like two finger precision grip can be trained (i.e., thumb and index finger tip to tip pinch). The FES therapy protocols can be successfully applied to individuals with paralysis resulting from stroke or spinal cord injury.
Introduction
Application of functional electrical stimulation (FES) for therapeutic purposes in rehabilitation settings dates back to the 1960’s when Liberson et al. (1961) used an FES system to stimulate the peroneal nerve to correct foot drop by triggering a foot switch, a single-channel electrical stimulation device stimulated the common peroneal nerve via a surface electrode, producing ankle dorsiflexion during the swing phase of gait (Liberson et al., 1961). This led to the first commercially available FES system with surface stimulation electrodes. Since then FES technology has been researched extensively to evaluate its benefits in diverse neurological conditions, and using an array of application techniques (Baldi et al., 1998; Field-Fote, 2001; Popovic et al., 2005, 2011, 2012, 2016; Yan et al., 2005; Frotzler et al., 2008; Griffin et al., 2009; Daly et al., 2011; Kapadia et al., 2011, 2013, 2014a; Giangregorio et al., 2012; Malešević et al., 2012; Martin et al., 2012; Kawashima et al., 2013; Lee et al., 2013; Sadowsky et al., 2013; Ho et al., 2014; Kapadia N. et al., 2014; Popović, 2014; Sharif et al., 2014; Bauer et al., 2015; Howlett et al., 2015; Vafadar et al., 2015; Buick et al., 2016; Cuesta-Gómez et al., 2017; Fu et al., 2019; Straudi et al., 2020). The two common uses of FES are to replace function (i.e., as an orthotic device) and to retrain function (i.e., as a therapeutic device). In this article we will limit ourselves to the therapeutic application of FES.
In the therapeutic application (FES therapy), FES is used as a short-term treatment modality. The expectation is that, after training with the FES system, the patients will be able to voluntarily perform the trained activities without FES (i.e., patients are expected to regain voluntary function). To date, a few high-quality randomized controlled trials have been performed, proving the efficacy of FES therapy over other rehabilitation techniques (Sharififar et al., 2018; Yen et al., 2019). This paucity in multicenter randomized controlled trials and the limited access to systems that can properly deliver FES therapy might have affected its uptake in clinical settings (Ho et al., 2014; Auchstaetter et al., 2016). Fortunately, both these issues are being addressed as new FES systems that are specifically developed for FES therapy are being introduced, as well as large scale multicenter randomized controlled trials are being planned to further confirm the efficacy of this rehabilitation modality. This article will provide readers with the details on how transcutaneous multichannel FES therapy for the upper extremity can be applied in clinical trials and as such the same methodology can be used in clinical practice by physiotherapists and occupational therapists.
The FES methodology discussed here has been developed with the intent to be user friendly, robust and to be able to produce better functional gains than the presently available best-practice rehabilitation techniques. The FES system used in our laboratory is a surface stimulation system with up to 4 stimulation channels that can produce gross motor function as well as precision grips such as two finger pinch grip. However, the methodology of FES application discussed here is pertinent to any multichannel transcutaneous FES device. We have used transcutaneous FES to retrain reaching and grasping in individuals with both spinal cord injury and stroke (Thrasher et al., 2008; Kapadia and Popovic, 2011; Kapadia et al., 2011, 2013; Popovic et al., 2012; Hebert et al., 2017). The results obtained in both patient populations indicate functional improvements after 8–14 weeks of therapy (20–48 h of stimulation). Patients showed reduced dependency on caregivers, and some even became independent in their activities of daily living.
This article will extensively detail how FES was applied in these previously successful clinical trials to retrain reaching and grasping functions in individuals who sustained a spinal cord injury or a stroke.[…]