Functional electrical stimulation for foot drop in the upper motor neuron syndrome: does it affect 3D foot kinematics during the stance phase of walking?

Abstract Background Foot-drop is a common impairment in individuals with upper motor neuron syndrome. It may cause walking instability, and greater risk of tripping and falling. Ankle–foot orthoses are the standard of care for foot-drop, but may constrain ankle movement and limit function. Functional electrical stimulation (FES) was shown to be a less restrictive and effective alternative. Previous studies have addressed the improvement of ankle dorsiflexion during swing and initial contact. However, the foot motion is 3-dimensional and if the stimulation of m. peroneus longus and m. tibialis anterior is not well balanced, excessive eversion or inversion of the foot can occur respectively. Therefore, the objective is to show the effect of FES on foot motion during walking. Methods Sixteen patients with an upper motor neuron syndrome, with a mean age of 15.7 (SD=8.7) years, GMFCS I and II and foot-drop were included. Gait analyses in FES and non-FES conditions were performed at preferred walking speed using the Oxford Foot Model. Differences between conditions were revealed using a t-test. Results Use of FES significantly increased peak dorsiflexion in swing phase during walking by 4.7 (SD=6.0). Eversion of the rearfoot and abduction of the forefoot significantly increased during initial ground contact by 3.7 (SD=4.9) and 1.9 (SD=2.2) respectively. This translates to a significant eversion and abduction of 1.4 (SD=2.7) and 1.3 (SD=2.1) during stance phase of walking. Conclusions FES aiming for improved dorsiflexion in swing, increases hindfoot eversion and forefoot abduction that translates into initial contact and persists, although to a lesser extent, during stance phase of walking. The consistent increase in rearfoot eversion may be due to the strategy of choosing higher stimulation intensity and accept exaggerated eversion. While this strategy provides a certain amount of safety and functionality, it affects foot kinematics during stance phase of walking. This can be advantageous for a clubfoot deformity and may have implications for their therapy but deteriorates an existing flatfoot deformity.