Surplus value of implanted peroneal functional electrical stimulation over ankle-foot orthosis for gait adaptability in people with foot drop after stroke.

BACKGROUND: Implanted peroneal functional electrical stimulation (FES) is an effective alternative treatment to ankle-foot orthosis (AFO) in people with drop foot after stroke. With FES no constraints on ankle mobility are imposed which might particularly be exploited in challenging walking environments that require adaptations of the gait pattern to environmental disturbances. RESEARCH QUESTION: Is gait adaptability, by means of the capacity to avoid sudden obstacles while walking on a treadmill, superior with implanted FES compared to AFO in people with drop foot after stroke? METHODS: A 4-channel peroneal nerve stimulator (ActiGait®) was implanted in 22 persons with stroke (>6 months) who regularly used an AFO. Gait adaptability was tested with an obstacle avoidance task on an instrumented treadmill up to 26 weeks (n = 10) or 52 weeks (n = 12) after FES-system activation. At assessments, 30 trials, in which obstacles were suddenly dropped onto the treadmill in front of the paretic leg, were recorded with each device (FES / AFO). Trials were grouped by available response times (ART) and success rates were calculated. The effect of device, ART and follow up time on success rates was tested using generalized estimated equations. Nonparametric correlations were calculated to associate changes in success rates with clinimetrics. RESULTS: Success rates of obstacle avoidance were higher when participants used their FES system compared to AFO (Δ4.7%, p = 0.03), which effect was largest for longest ARTs (Δ15%, p = 0.03). Participants with greater motor impairment of the paretic leg showed greater benefit from FES (rs=-0.49, p = 0.04). SIGNIFICANCE: FES has been found equally effective as AFO in improving walking speed of people with drop foot after stroke. We now present superior walking performance in a complex walking environment for implanted peroneal FES compared to AFO. These findings underline the importance of using gait assessments that require interplay with the environment, besides assessment of stationary walking, in community ambulators.

Effects of implantable peroneal nerve stimulation on gait quality, energy expenditure, participation and user satisfaction in patients with post-stroke drop foot using an ankle-foot orthosis.

PURPOSE: To investigate whether an implantable functional electrical stimulation (FES) system of the common peroneal nerve (ActiGait®) improves relevant aspects of gait in chronic stroke patients with a drop foot typically using an ankle-foot orthosis (AFO). METHODS: Ten community-dwelling patients participated, of whom eight patients could be analysed. Gait quality (kinematic, kinetic, and spatiotemporal characteristics) during a 10-meter comfortable walk test, normalised net energy expenditure during a 6-minute walk test, participation (physical activity and stroke impact) and user satisfaction were tested before implantation and at various moments after FES-system activation up to 26 weeks. RESULTS: Walking with FES yielded increased maximum paretic ankle plantarflexion (FES: -0.12; AFO: -4.79°, p <  0.01), higher paretic peak ankle power (FES: 1.46; AFO: 0.98 W/kg, p <  0.05) and better step length symmetry (FES: 14.90; AFO: 21.45% , p <  0.05). User satisfaction was higher for FES, but was unrelated to objective gait improvements. Energy expenditure and participation did not change. CONCLUSION: Implantable FES improved the use of residual ankle plantarflexion motion, ankle power of the paretic leg and step length symmetry compared to using an AFO, however, not resulting in decreased energy expenditure or improved participation. User satisfaction was highest with FES, but this was not related to the observed gait improvements.

The capacity to restore steady gait after a step modification is reduced in people with poststroke foot drop using an ankle-foot orthosis.

BACKGROUND: A reduced capacity to modify gait to the environment may contribute to the risk of falls in people with poststroke foot drop using an ankle-foot orthosis. OBJECTIVE: This study aimed to quantify their capacity to restore steady gait after a step modification. DESIGN: This was a cross-sectional, observational study. METHODS: Nineteen people in the chronic phase (>6 months) after stroke (mean age=55.0 years, SD=10.1) and 20 people of similar age (mean age=54.6 years, SD=12.0) who were able-bodied were included. Participants were instructed to avoid obstacles that were suddenly released in front of the paretic leg (stroke group) or left leg (control group) while walking on a treadmill. Outcomes were success rates of obstacle avoidance as well as post-crossing step length, step duration, hip flexion angle at foot-strike, and peak hip extension of the steps measured within 10 seconds following obstacle release. RESULTS: Success rates of obstacle avoidance were lower for people poststroke. Moreover, their first post-crossing step length and duration (ie, the nonparetic step) deviated more from steady gait than those of people in the control group (ie, the right step), with lower values for people poststroke. Similar deviations were observed for post-crossing hip flexion and extension excursions. LIMITATIONS: People poststroke were relatively mildly impaired and used an ankle-foot orthosis, which may limit the generalizability of the results to other populations poststroke. CONCLUSIONS: People with poststroke foot drop using an ankle-foot orthosis had reduced gait adaptability, as evidenced by lower success rates of obstacle avoidance as well as an impaired capacity to restore steady gait after crossing an obstacle. The latter finding unveils their difficulty in incorporating step modifications in ongoing gait.

Deficits in motor response to avoid sudden obstacles during gait in functional walkers poststroke.

BACKGROUND: Safe community ambulation requires the capacity to adapt gait to environmental changes on short notice. Reduced adaptability may contribute to an increased risk for falls. OBJECTIVE: This study investigated gait adaptability in community-dwelling persons poststroke and sought to understand some of the mechanisms of reduced adaptability. METHODS: Participants were 25 poststroke persons (Functional Ambulation Categories score 5) and 25 healthy controls of similar age. During treadmill walking, 30 obstacles were suddenly dropped in front of the affected leg or left leg of controls. The participants had to avoid the obstacle by either lengthening or shortening the ongoing stride. The obstacle avoidance success rates were determined. Electromyography activity of bilateral biceps femoris, rectus femoris, tibialis anterior, and gastrocnemius medialis muscles was recorded as well as concomitant knee and hip angle courses and spatial characteristics of the avoiding stride. RESULTS: Poststroke persons demonstrated markedly decreased obstacle avoidance success rates, most prominently under time pressure. They showed normal avoidance strategies but had delayed and reduced electromyography responses, smaller joint angle deviations from unperturbed walking, and smaller horizontal margins from the foot to the obstacle. CONCLUSIONS: Even in persons who were only mildly affected by stroke, gait adaptability may be reduced, which may place them at risk of falling. Delayed and decreased muscle responses were identified as one possible mechanism with diminished ability to adapt the length of the avoiding stride. Rehabilitation interventions could focus on these impairments.

Community-dwelling people with chronic stroke need disproportionate attention while walking and negotiating obstacles.

The objective of the present study was to examine the attentional demands of gait adaptations required to walk over irregular terrain in community-dwelling people with chronic stroke. Eight community ambulators (>6 months post-stroke, aged 57 ± 15 years) and eight age-matched healthy controls participated in the study. As the primary motor task, participants walked on a treadmill while they quickly reacted to a sudden obstacle in front of the affected (in the stroke group) or left (in healthy controls) leg. The secondary, cognitive task was an auditory Stroop task. Outcomes were avoidance success rate and muscle reaction times of the biceps and rectus femoris (motor task), and a composite score of accuracy and verbal reaction time (cognitive task). Success rates did not differ between single- and dual-task conditions in either group, while muscle reaction times deteriorated equally during the dual task in both groups. However, compared with the Stroop scores just before and after obstacle crossing, the scores while crossing the obstacle deteriorated more in the stroke group than in the controls (p=0.012). The higher dual-task costs on the Stroop task reflect greater attentional demands during walking and crossing obstacles. The absence of dual-task effects on obstacle avoidance performance suggests that the people with stroke used a "posture-first strategy". The results imply that common daily life tasks such as obstacle crossing while walking require disproportionate attention even in well-recovered people with stroke.

Effect of peroneal electrical stimulation versus an ankle-foot orthosis on obstacle avoidance ability in people with stroke-related foot drop.

BACKGROUND: Walking ability of people with foot drop in the chronic phase after stroke is better with functional electrical stimulation (FES) of the peroneal nerve than without an orthotic device. However, the literature is not conclusive on whether peroneal FES also is better than an ankle-foot orthosis (AFO) in this regard. OBJECTIVE: This study aimed to identify potential benefits of peroneal FES over an AFO with respect to the ability to negotiate a sudden obstacle. DESIGN: The study design was a within-subject comparison between FES and AFO using repeated measures. METHODS: Twenty-four community-dwelling people with stroke (mean age=52.6 years, SD=12.7) who regularly used a polypropylene AFO were fitted with a transcutaneous FES device. The participants' obstacle avoidance ability was tested after 2 and 8 weeks. They had to avoid 30 obstacles that were suddenly dropped on a treadmill in front of the affected leg while walking with either FES or an AFO. The obstacle avoidance success rates were determined. RESULTS: Success rates were higher with FES than with an AFO, especially after adjustment for individual leg muscle strength. Participants with relatively low muscle strength (Motricity Index score <64) were most likely to benefit from FES regarding obstacle avoidance ability. LIMITATION: Further work is needed to determine whether the results may be generalized to other groups of people with stroke. CONCLUSIONS: Peroneal FES seems to be superior to an AFO with regard to obstacle avoidance ability in community-dwelling people with stroke. The observed gains in obstacle avoidance ability appear to be clinically most relevant in the people with relatively low leg muscle strength.

Near-normal gait pattern with peroneal electrical stimulation as a neuroprosthesis in the chronic phase of stroke: a case report.

In recent years, the use of functional electrical stimulation (FES) of the peroneal nerve has increased as an alternative for an ankle-foot orthosis (AFO) to treat stroke-related drop foot. We present a chronic stroke patient demonstrating an almost normal gait pattern with peroneal FES as a neuroprosthesis. A 60-year-old survivor of a right hemisphere infarction 21 months ago, who regularly used a polypropylene AFO, was provided with a surface-based peroneal FES device for severe drop foot. In a second instance, he received an implanted FES system because of skin problems with the surface stimulator. With both FES devices, the patient achieved an adequate foot elevation. Moreover, his hip and knee flexion angles during walking increased to normal values and his ankle push-off power increased. His gait pattern became almost symmetrical and less variable than with the AFO. Furthermore, his ability to avoid a sudden obstacle improved to normal values with FES. Our patient showed benefits from peroneal FES beyond what can be attributed to improved foot lift alone. With regard to the potential working mechanisms underlying this response to FES, biomechanical benefits related to improved ankle push-off are suggested as the main mechanism.

Is transcutaneous peroneal stimulation beneficial to patients with chronic stroke using an ankle-foot orthosis? A within-subjects study of patients' satisfaction, walking speed and physical activity level.

OBJECTIVE: The aim of this study was to evaluate whether community-dwelling chronic stroke patients wearing an ankle-foot orthosis would benefit from changing to functional electrical stimulation of the peroneal nerve. METHODS: In 26 community-dwelling chronic (> 6 months post-onset) patients after stroke, their ankle-foot orthosis was replaced by a surface-based functional electrical stimulation device (NESS L300). Comfortable walking speed over 10 m was measured at baseline with the ankle-foot orthosis and after 2 and 8 weeks with both ankle-foot orthosis and functional electrical stimulation. The level of physical activity was assessed with a pedometer, and patients' satisfaction was assessed with a questionnaire at baseline and at week 8 regarding ankle-foot orthosis and functional electrical stimulation, respectively. RESULTS: Ankle-foot orthosis and functional electrical stimulation were equally effective with regard to walking speed and activity level. The participants were more satisfied with functional electrical stimulation than with their ankle-foot orthosis regarding the effort and stability of walking, quality of the gait pattern, walking distance, comfort of wearing and appearance of the device. CONCLUSION: The patients judged functional electrical stimulation superior to their ankle-foot orthosis, but measurements of walking speed and physical activity could not objectify the experienced benefits of functional electrical stimulation. Other outcome measures focusing on the stability and effort of ambulation may objectify the perceived benefits of functional electrical stimulation in community-dwelling chronic stroke patients.

The dynamics of postural sway cannot be captured using a one-segment inverted pendulum model: a PCA on segment rotations during unperturbed stance.

Research on unperturbed stance is largely based on a one-segment inverted pendulum model. Recently, an increasing number of studies report a contribution of other major joints to postural control. Therefore this study evaluates whether the conclusions originating from the research based on a one-segment model adequately capture postural sway during unperturbed stance. High-pass filtered kinematic data (cutoff frequency 1/30 Hz) obtained over 3 min of unperturbed stance were analyzed in different ways. Variance of joint angles was analyzed. Principal-component analysis (PCA) was performed on the variance of lower leg, upper leg, and head-arms-trunk (HAT) angles, as well as on lower leg and COM angle (the orientation of the line from ankle joint to center of mass). It was found that the variance in knee and hip joint angles did not differ from the variance found in the ankle angle. The first PCA component indicated that, generally, the upper leg and HAT segments move in the same direction as the lower leg with a somewhat larger amplitude. The first PCA component relating ankle angle variance and COM angle variance indicated that the ankle joint angle displacement gives a good estimate of the COM angle displacement. The second PCA component on the segment angles partly explains the apparent discrepancy between these findings because this component points to a countermovement of the HAT relative to the ankle joint angle. It is concluded that postural control during unperturbed stance should be analyzed in terms of a multiple inverted pendulum model.