FES for drop foot

Hello to everybody once again, this blog will focus on the pioneering uses of FES in drop foot after a person has had a stroke. The main focus of this blog will be assessing the suitability of foot switch FES in correcting the gait cycle.

           
The factors necessary for successful FES of the lower limb are: appropriate patient selection, comprehensive guided training, and effective follow-up after initial installation of the FES device (Embrey, Holtz, Alon, Brandsma, & McCoy, 2010). The FES device will be used to improve dorsiflexion during the swing phase and at primary contact and increase plantar flexion at toe-off (Embrey et al., 2010). The eccentric dorsiflexion contractions are essential for normal gait because it allows for shock absorption and to prevent foot slap (Popovic & Sinkjær, 2000). The video in the blog displays an FES device but it is not the device reviewed, the device that is reviewed is shown in the pictures below the video. The video has been inserted to demonstrate correction of foot drop via FES. Although, the device displayed in the video varies from the device reviewed in the study, they were both developed with the same functional outcomes as a priority. 

Equipment and parts

The FES device is administered via surface electrical stimulation electrodes (5.08 × 5.08 cm [2 ×2 in]) and they are applied to the ankle dorsiflexor muscles (Kesar, Perumal, Jancosko, Reisman, Rudolph, Higginson & Binder-Macleod, 2010). Accurate electrode placement is essential because it will limit the amount of ankle inversion and eversion during gait (Kesar et al., 2010). Two compression-closing footswitches (25-mm diameter MA-153) are attached bilaterally to the soles of each shoe, one on the forefoot under the fifth metatarsal head and the other on the hind foot under the lateral portion of the heel, they are used to control the timing of FES during gait (Kesar et al., 2010). These electrodes are connected to a Grass S8800 stimulation, in combination with a Grass Model SIU8TB stimulus isolation unit, which deliver the electrical stimulation (Kesar et al., 2010). The functional parameters for both items can be viewed via the hyperlinks.

How it all works  

Once the FES device has been tailored specifically to the participant, they are placed into a seated position which allows their foot to hang freely in a plantar-flexed position (Popovic & Sinkjær, 2000). The FES device stimulation amplitude is established by gradually increasing the amplitude of a 300-millisecond-long, 30-Hz train with a pulse duration of 300 microseconds until a neutral ankle joint position (0°) is gained (Popovic & Sinkjær, 2000). In severe control deficit cases, a plantar flexion of at least 5 degrees needs to be acquired from the FES device stimulation (Kesar et al., 2010). The FES device purpose is to supply the FES to the paretic (paralysis) ankle dorsiflexor muscles during the swing phase of each gait cycle and this is sensed by the footswitches placed on the foot. (i.e., from the time when the forefoot footswitch was off the ground to the time when the hindfoot footswitch contacts the ground)(Kesar et al., 2010).

3D animation of foot drop treated by FES (Please note this treatment varries slightly from that explained above)

Outcomes of the FES system

The benefits of this FES system are increased dorsiflexor of the paretic muscles of the ankle (Popovic & Sinkjær, 2000). This functional enhancement causes a reduction in ankle plantar flexion at toe-off and reduced knee flexion during the swing phase of gait (Popovic & Sinkjær, 2000). Although, there is an increased amount of ankle dorsiflexion from the FES system, there was no improvement in hip circumduction. The cause of the non-reduction in hip circumduction is because hip circumduction is used as a gait compensatory technique and this habit would not be immediately stopped when the person had regained necessary foot clearance during gait (Kesar et al., 2010).

The Cost

1 x Transformer Stimulus Isolation Unit, Transformer Coupled     £599.50

1 x Grass S8800 stimulator                                                              £60.50

Picture from : http://www.lowerextremityreview.com/article/next-step-for-fes-focuses-on-plantar-flexor-muscles