To date, there are no randomized controlled or blinded assessments of the training effects of FES to improve mobility after SCI. Furthermore, only three of the studies reviewed here (Thrasher et al. 2006; Granat et al. 1993; Klose et al. 1997) report specific usage parameters for FES during gait rehabilitation, whereby FES was applied for at least 30 minutes, 2 to 5 times/week for up to 4.5 months. In the remainder of the studies, participants were provided with FES systems to use at home “as much as possible” or “as desired” over the course of the study (Ladouceur and Barbeau 2000a; 2000b; Wieler et al. 1999; Stein et al. 1993). Results from the ten pre-post studies included here show that almost all the participants showed improvements in gait parameters (walking speed or distance) when FES was used (Thrasher et al. 2006; Ladouceur and Barbeau 2000a; 2000b; Wieler et al. 1999; Klose et al. 1997; Granat et al. 1993; Stein et al. 1993; Granat et al. 1992). This is not surprising, given that the FES could compensate for weakened or paralyzed muscle function during gait. Of greater interest is the finding of carryover effects after FES training. Several investigators have also reported a carryover effect after FES training such that improvements in functional ambulation (e.g. overground walking speed and distance, step length) persisted even when the stimulator was turned off (Ladouceur and Barbeau 2000b; Wieler et al. 1999). This suggests that neuroplastic changes may have taken place in response to regular use of FES during walking. Indeed, it has been shown in non-disabled human participants that the combination of treadmill walking and FES led to an acute increase in corticospinal excitability that persists even after the cessation of FES (Kido Thompson and Stein 2004). Improved muscle strength and conditioning after regular use of FES could also contribute to carryover effects in walking function (Granat et al. 1993). The use of FES and weight-bearing also helps to maintain the subtalar and midfoot joint mobility needed for walking (Bittar & Cliquet 2010).
Although laboratory studies advocate the efficacy of FES systems for improving ambulatory function in patients with SCI, the effectiveness of any technology is only as good as its acceptance by the intended users. Wieler et al. (1999) reported that the majority of their participants found they could use the FES device easily on a regular basis and that they walked better with the FES. Those who reported difficulties reported problems with finding the proper stimulation site or technical difficulties with the leads, switches, or electrodes. There have also been reports of musculoskeletal complications such as ankle sprain, calcaneum fracture, back pain, or falls with FES use (Brissot et al. 2000; Gallien et al. 1995). Some of these complications may have been associated with commencement of upright exercise (gait) after a period of being non-ambulatory. Anecdotal reports found in several studies suggest that most participants mainly use FES indoors or at home, for short distance walking, to prevent complications due to prolonged immobilization, and to enhance physical fitness rather than functional community ambulation (Brissot et al. 2000; Gallien et al. 1995; Klose et al. 1997). Participants who do use FES outdoors for community ambulation tend to be those less severely impaired (Brissot et al. 2000; Granat et al. 1993).
The functional benefits derived from FES are also quite variable. For instance, Stein et al. (1993) report that most participants showed a modest improvement in gait speed (average: 4 m/min), which was more significant for the more severely disabled participants. Higher-functioning participants felt that this small benefit in gait speed did not warrant the daily use of FES. In contrast, Ladouceur and Barbeau (2000b) reported that there was a tendency for the participants with initially faster gait speed to have greater absolute improvements. Thus, outcomes from FES-use also seem to be quite variable in terms of walking speed (Ladouceur and Barbeau 2000b; Stein et al. 1993) or distance (Klose et al. 1997).
There is level 4 evidence (Thrasher et al. 2006; Ladouceur and Barbeau 2000a; 2000b; Wieler et al. 1999; Klose et al. 1997; Granat et al. 1993; Stein et al. 1993; Granat et al. 1992) that FES-assisted walking can enhance walking speed and distance in complete and incomplete SCI.
There is level 4 evidence from 2 independent laboratories (Ladouceur and Barbeau 2000a,b; Wieler et al. 1999) that regular use of FES in gait training or activities of daily living leads to persistent improvement in walking function that is observed even when the stimulator is not in use.