Abstract
Background
Central drop foot is a common problem in patients with stroke or multiple sclerosis (MS). For decades, it has been treated with orthotic devices, keeping the ankle in a fixed position. It has been shown recently that semi-implantable functional electrical stimulation (siFES) of the peroneal nerve can lead to a greater gait velocity increase than orthotic devices immediately after being switched on. Little is known, however, about long-term outcomes over 12 months, and the relationship between quality of life (QoL) and gait speed using siFES has never been reported applying a validated tool. We provide here a report of short (3 months) and long-term (12 months) outcomes for gait speed and QoL.
Methods
Forty-five consecutive patients (91% chronic stroke, 9% MS) with central drop foot received siFES (Actigait®). A 10 m walking test was carried out on day 1 of stimulation (T1), in stimulation ON and OFF conditions, and repeated after 3 (T2) and 12 (T3) months. A 36-item Short Form questionnaire was applied at all three time points.
Results
We found a main effect of stimulation on both maximum (p < 0.001) and comfortable gait velocity (p < 0.001) and a main effect of time (p = 0.015) only on maximum gait velocity. There were no significant interactions. Mean maximum gait velocity across the three assessment time points was 0.13 m/s greater with stimulation ON than OFF, and mean comfortable gait velocity was 0.083 m/s faster with stimulation ON than OFF. The increase in maximum gait velocity over time was 0.096 m/s, with post hoc testing revealing a significant increase from T1 to T2 (p = 0.012), which was maintained but not significantly further increased at T3. QoL scores showed a main effect of time (p < 0.001), with post hoc testing revealing an increase from T1 to T2 (p < 0.001), which was maintained at T3 (p < 0.001). Finally, overall absolute QoL scores correlated with the absolute maximum and comfortable gait speeds at T2 and T3, and the increase in overall QoL scores correlated with the increase in comfortable gait velocity from T1 to T3. Pain was reduced at T2 (p < 0.001) and was independent of gait speed but correlated with overall QoL (p < 0.001).
Conclusions
Peroneal siFES increased maximal and comfortable gait velocity and QoL, with the greatest increase in both over the first three months, which was maintained at one year, suggesting that 3 months is an adequate follow-up time. Pain after 3 months correlated with QoL and was independent of gait velocity, suggesting pain as an independent outcome measure in siFES for drop foot.
Introduction
Drop foot is a common symptom in patients suffering from first motor neuron lesions, such as due to stroke and multiple sclerosis (MS). It is characterized by impaired lifting of the forefoot from the ground during the swing phase of walking and by a lack of stability during the early stance phase. Drop foot results in an altered gait pattern [3] and increased risk of falls [8]. Application of an ankle foot orthosis (AFO) is the traditional approach to improving gait pattern and reducing falls. However, it is not well-tolerated in all patients [10]. In recent years, gait improvement has been achieved using functional electrical stimulation (FES) [1, 10, 16, 23, 25], which combines the orthotic benefits of an AFO with a more physiological approach that involves muscle contraction and the related sensory feedback [10, 25]. Transcutaneous FES (tcFES) of the peroneal nerve has been associated with significantly reduced falls compared to intensive physiotherapy [7]. Indeed, 69% of the falls in this FES group occurred when the system was not used. Moreover, a systematic review of FES in MS patients indicates increased gait speed using FES [19]. Semi-implantable FES (siFES) of the peroneal nerve has been found to increase gait speed and improve gait patterns compared with a baseline without stimulation [6, 10, 17], compared to orthotic devices [1, 23], and also compared to tcFES [17]. The findings of a systematic review, including predominantly chronic stroke patients, however, did not suggest a difference between tcFES and siFES in terms of walking speed [13]. An implantable stimulator does, however, offer the advantage of avoiding the need for daily optimization of stimulator location [28] and potential skin lesions associated with surface stimulation electrodes. Moreover, the possibility of using a 4-channel implantable system, with independent control of each channel, means that the volume of tissue activated within the nerve can be individually selected, in order to optimize dorsiflexion of the foot while avoiding stimulation of the sensory fascicles of the common peroneal nerve [10]. Here we retrospectively hypothesised that increases in gait speed are associated with improvements in quality of life (QoL). Furthermore, we assumed pain scores had improved under therapy and expected them to be related to the overall QoL, and we hypothesised that increased gait velocity would have resulted in improvement of both physical and emotional subscores of the QoL. To address these hypotheses, we evaluated improvement in gait velocity in the largest cohort of patients to date, with stimulation ON and OFF, at three time points over 1 year, to assess the short- and long-term effects of siFES, examining correlation between gait speed and QoL, as well as between changes in these factors, over a year of continuous treatment.
Most studies of implantable systems for stroke to date cover observation periods of 3 to 6 months post-surgery and suggest siFES provides a promising approach to managing drop foot. An increase in gait velocity and endurance, as well as an improvement in QoL, was observed 3–6 weeks post-operatively in a cohort of 27 patients receiving siFES [17]. Trials applying tcFES, which has been available since the early seventies [27], have tended to employ standardized and stratified re-examination, with early and long-term follow-up periods, such as 6 and 12 weeks [16], 3 and 12 months [25], and 24 days and 3 years [28]. A recent long-term multi-centre study applying siFES reported an improved gait pattern in a cohort of 10 stroke patients 6 months following siFES activation and in a separate cohort of 12 stroke patients 1 year after activation [1]. Their findings suggested greater knee stability, ankle plantarflexion power, and propulsion than that provided by an AFO. Here, we examined both the short- and long-term effects of using multichannel peroneal siFES in the largest patient group thus far reported, including both stroke and MS patients. The independent association between slow gait velocity and an increased risk of falls [8] renders gait velocity a valid surrogate parameter for the orthotic functionality of devices aiming to improve the limitations of drop foot. We aimed to investigate whether gait velocity improvements translate into QoL changes. Long-term follow-up (one year or longer) has been reported for large cohorts (more than 20 patients) using tcFES [25, 28], and for a smaller cohort (N = 12) using siFES [1]. Long-term follow-up in a large cohort of patients receiving siFES and evaluating QoL has not yet been reported. The particular strengths of the current study are the large cohort, the inclusion of short- and long-term follow-up, and the evaluation of QoL and its correlation with gait speed.[…]
Fig. 1Gait speed (m/s) in relation to duration of therapy with stimulation ON and OFF. a. Maximum gait velocity. Main effect of stimulation and time. Post hoc testing: significant difference from day 1 to month 3 (*). b. Comfortable gait velocity. Main effect of stimulation only. Error bars = standard error of the mean
TBI Rehabilitation 