Brief Report The effectiveness of functional electrical stimulation for the management of footdrop after stroke.

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1 Brief Report The effectiveness of functional electrical stimulation for the management of footdrop after stroke. Reviewer Peter Larking Date Report Completed November 2009 Important Note: The purpose of this brief report is to summarise information on the effectiveness of Functional Electrical Stimulation for the management of foot drop as a result of a stroke and to provide best practice advice. It has been systematically developed according to a predefined methodology. It is not intended to replace clinical judgement, or be used as a clinical protocol. A reasonable attempt has been made to find and review papers relevant to the focus of this report, however it does not claim to be exhaustive. The document has been prepared by the staff of the evidence based Healthcare Advisory Group, ACC. The content does not necessarily represent the official view of ACC or represent ACC policy. This report is based upon information supplied up to 14 September Background Footdrop is one of the most common gait impairments associated with hemiplegia and is a simple term describing a complex problem. It is caused mainly by spasticity of the posterior muscles of the leg, tendon shortening of the posterior muscles and weakness of the anterior muscles 1. The muscle weakness may be treated with rehabilitation, walking aids, ankle foot orthoses (AFO) and sometimes by functional electrical stimulation (FES). FES is a technique that delivers an electric current to muscles via electrodes. The intensity of the FES current is able to activate motor neurons and produce a muscle contraction. FES technology varies widely; the current can be delivered via implanted or external electrodes. Single channel units stimulate along the path of a nerve or muscle via two electrodes; multichannel units with more than two electrodes may be used to stimulate numerous muscles. Accident Compensation Corporation

2 It is claimed that FES may be used to improve such things as gait, muscle strength and motor performance, and decrease spasticity in a range of patients including those who have had a cerebrovascular accident or have conditions like motor neurone disease or cerebral palsy 1. In patients with footdrop as a result of a stroke, FES has been used for a therapeutic effect whereby improvements are sought after a series of FES treatments over weeks or months or for an orthotic effect when improvements in gait speed are sought when the patient is walking and the FES device is activated. Therapeutic effects may be sought at any time after the stroke whereas orthotic effects are sought typically in the chronic phase. This report investigates evidence of effectiveness of FES for footdrop after stroke regardless of the FES system used. 2. Methodological approach The original research question was: Is functional electrical stimulation using the Ness L300 device effective for foot drop and chronic muscle spasm of the lower limb in patients with hemiplegia? Because there were only three related papers essentially from the same trial that investigated the Ness L300 system, systematic reviews and recent RCTs have also been included that investigated FES for correction of footdrop post stroke. This review is based on two systematic reviews, one for the therapeutic effect published in and one on the orthotic effect published in Trials published since these dates that investigated FES for footdrop in stroke patients are also included. All studies had to be based predominantly on subjects with footdrop as a result of stroke and include 10 or more subjects in the study. 3. Investigation The effect of FES on footdrop after stroke the orthotic effect 1. Kottink et al (2004) 2 have conducted a systematic review of the orthotic effect of FES on the improvement of walking in stroke patients with a footdrop. They found eight studies on a total of 203 patients. The studies included stroke patients in the acute, sub acute and chronic (87%) phases. Four studies were of a before/with design, two crossover, one with and without FES and one RCT; three used implanted systems and 5 surface systems. One crossover study compared the result of FES use with that of an ankle/foot orthosis, the remaining seven with no aid. Walking speed and physiological cost index were selected as the primary outcome measures. A meta-analysis was made. Walking speed changes were measured in six studies and a pooled difference estimated using a random effects model. The pooled improvement in walking speed in the six studies was 0.13m/s (95% CI, ) or a 38% improvement. Five of the six studies found that FES improved walking speed and one found a small decrease. The quality of the underlying studies is marginal; only one was an RCT, numbers are small and there are considerable variations amongst the eight studies included in experimental design, technology and time after the stroke event. However the conclusion that the use of FES is, in a statistical sense an improvement seems reasonable. The questions of whether FES results in significant clinical improvements is less certain and whether or not it is superior to the use of an ankle foot orthosis (AFO) was not able to be examined. Accident Compensation Corporation Page 2

3 2. One RCT has been reported since publication of the systematic review (above). It investigated the effect on walking speed post stroke of an implanted 2-channel peroneal nerve stimulator (Kottink etal) 3, the control group being, use of conventional walking aid ( a plastic AFO (intervention group 7/14, control 15/15) orthopaedic shoe or no device). The study was conducted on 29 stroke survivors in the chronic phase who were all capable of walking outdoors. Fourteen subjects were randomly allocated to the intervention and 15 to the control group at least 6 months post stroke. All subjects had to be able to walk outdoors. Patients were assessed before randomisation and at 4, 8, 12 and 26 weeks. Mean data was not reported other than in graphs and it is difficult from the paper to estimate the actual size of the changes. The author s reported in the abstract that FES resulted in a 23% improvement in walking speed as measured by the 6 minute walking test whereas the control group improved by only 3% (P=.01). In the Results these figures are not mentioned. It is said that when the control group used their walking aid and the intervention group used FES the linear mixed model indicated significant differences between groups (P<.038). Further at none of the follow-up assessments where the use of FES in the intervention group was compared with use of an AFO in the control did post hoc testing result in a statistically significant difference relative to baseline. This paper has several important limitations which make interpretation difficult. Some of these problems are - Subjects were only recruited if able to walk outdoors and so were already reasonably ambulatory; the trial does not therefore test FES in the more impaired subjects Data is only reported in graphs and this makes any assessment of the impact of this study difficult The potential importance of this study is that the comparison group was to be use of a walking aid. This potential advantage was negated in reality as the entire control group came into the study using a plastic ankle foot orthoses whereas only half of the intervention group used one; of the rest 3 patients wore orthopaedic shoes and four did not wear an aid. On this basis it is concluded that the two groups were not comparable at baseline with respect to the type of walking aid used. The randomisation therefore seems flawed in this critical aspect and this adds to the doubtfulness of the findings Statistical significance of the findings was at best low and was not sustained when conducted at individual follow up periods. It is concluded that the clinical relevance of the reported difference cannot be ascertained with certainty but appears to be slight and provides no conclusive evidence that FES is better than use of an AFO. 3. Hausdorf and others 4 5 have reported in two related papers a study on 24 subjects whose walking was impaired by footdrop; 21 as a result of stroke, 3 as result of a TBI. Seventeen used an anklefoot orthosis. Patients selected were in the chronic phase of care (5.8 +/- 5.2 years post stroke) and able to walk for at least 10 mins independently or with a cane. The FES neuroprothesis was the Ness L300 which delivers externally electrical pulses to the peroneal nerve throughout the swing of the gait resulting in ankle dorsiflexion. Subjects were tested in randomised order Accident Compensation Corporation Page 3

4 without and with the orthosis at baseline, four and eight weeks 4 and again at one year 5. FES resulted in statistically significant improvements at four and eight weeks (p<.001) in the asymmetry index, stride time variability, walking on carpet, obstacle course speed and the physiological cost index. The six minute walking speed rose 34% from 0.53 m/s at baseline to 0.71 at eight weeks. Similarly gait asymmetry index improved from 0.58 to 0.32 and stride time variability from 5.7 to 3.8. Sixteen of the 24 were available for follow up at one year. There was an 18% improvement in physical functioning and a 25% improvement in participation in community life at two months and these effects were maintained at one year 5. The authors quote data that suggest that in patients such as this the smallest change that indicates a clinical improvement in gait velocity is 7.9% (compared to 34% found here at 8 weeks). The majority of patients did not need further help to use the appliance after initial training and found it comfortable for all-day use. The authors conclude that the gains in social participation as a result of using the device were the more significant finding. Some limitations of the study are that it was conducted on small numbers, was partly funded by the manufacturers of the device and the omission of a control group increases risk of bias. More importantly it must be noted that the population trialled had a mean gait velocity before the application of the device of 0.67m/s which is as the authors acknowledge well within the gait velocity accepted as necessary for unlimited household ambulation. Moreover this velocity was measured without the use of an AFO which most subjects used so that gait velocity was routinely likely to be even higher. Finally effectiveness of FES was compared with performance with no orthosis even though a majority routinely used one. It is concluded that the use of the Ness L300 neuroprothesis resulted in statistically significant improvements in a range of relevant parameters in this particular population when compared to performance without an AFO. Since the population trialled was already mobile, many already used an AFO, and standard ankle foot orthoses convey some clinical benefit the relevance of the findings to ACC is doubtful. 4. Ring et al 6 have reported a follow up study to that of Hausdorf 4 5 as reported above. They used a subset of 15 patients from the above study whose walking was impaired by footdrop and regularly used an AFO. This time use of the Ness neuroprothesis was compared with the performance when the subjects used their own anklefoot orthosis. Performance was measured at baseline, after four weeks of adaptation and at the end of another four weeks; the AFO and the Ness neuroprothesis being tested in random order. After eight weeks there was no significant difference in gait speed; there were significant improvements in stride time (p<.02) swing time variability in the non paretic leg (p<0.01) and swing asymmetry (p<.05). There were no differences at the four week period. The authors concluded that compared to the AFO, the neuroprothesis appears to enhance balance control during walking and thus more effectively manage footdrop. Some limitations of the study include its small sample size and the limited duration of the study. Accident Compensation Corporation Page 4

5 It is concluded that the Ness neuroprothesis compared to the use of an AFO may influence a range of balance parameters but not gait speed over shorter time frames in subjects who were already reasonably mobile. The functional utility of these changes to the client in for example reducing falls was not investigated. 5. Sheffler et al (2006) 7 compared the efficacy of the Odsock Dropped Foot Stimulator a peronal nerve stimulation device with AFO in improving functional ambulation in 14 stroke subjects with footdrop greater than 90 days post stroke. Participants were required to be able to ambulate at least 30 feet continuously with minimal assistance without an AFO. They received training over three days with the stimulator, a customised AFO and no device. After this the participants were trialled first without any device and then with the AFO or stimulator in randomised order and performance measured at 5 individually timed tasks using a modified Emory Functional Ambulation Profile which includes walking on hard and carpeted floors. Functional ambulation with the AFO was significantly improved relative to no device on the floor (p<0.001), carpet (p = 0.013) and for the up and go test (p=0.042). Performance with the stimulator was statistically superior to no device on the carpet only (p=0.004). There was no statistical difference between the use of the stimulator and AFO. Subjects who used the stimulator preferred it to the AFO. The authors concluded that the AFO and stimulator were comparable in their effect on improving functional ambulation. This was a small trial and the authors noted that the outcomes from using the stimulator may have been prejudiced by the short training period in that all subjects had more experience pre trial with no device and the AFO. The trial may suggest that use of an AFO is effective and that short term training with the Odstock stimulator does not convey benefit in functional improvement over an AFO. The effect of FES on footdrop after stroke the therapeutic effect 6. A systematic review has been published in 2006 which investigated the therapeutic effect of FES on gait speed in stroke patients 1 (ie the carryover effect of FES when the stimulator is not used). They found three trials; Bogataj et al 8 used a randomly assigned controlled trial with crossover. Twenty subjects with severe hemiplegia were treated with multichannel FES for 3 weeks at a mean time of 3 to 4 months post stroke. Ten subjects received FES and conventional treatment first followed by three weeks of conventional treatment. The other 10 subjects received these treatments in reverse order. Burridge et al 9 used an RCT design using a single channel FES over the peroneal nerve for 3 months at a mean time of 3 years post stroke. 32 subjects completed the trial; 16 in each group. The comparison group was physiotherapy alone. Alon and Ring 10 used a non RCT design and treated 10 subjects with an integrated stimulation system for 8 weeks at a mean time of 3 years post stroke. The comparison group (9) was individual instructions for specific functional training and self exercising. A meta-analysis of these three trials was conducted. A total of 36 subjects received FES with 35 controls. Two trials reported effects in favour of FES; the one RCT found a small benefit in favour of the control group. The mean improvement due Accident Compensation Corporation Page 5

6 to FES over that of the controls was 0.18 m/s (95% CI; ) (P<.01). The therapeutic effect of FES was greatest when used in the post acute stage. Limitations of this systematic review include; It was based on only three small trials Considerable heterogeneity in the practice of FES used and when it was applied Widely variable baseline gait speeds between the three trials Only one trial was an RCT 9 and this reported that FES had no benefit The size of the mean improvement was largely dependent on one trial 8. The author s conclude that FES is effective at improving gait speed post stroke but in view of the limitations of the included studies this conclusion is not justified. 7. Since publication of this systematic review Daly et al published the results of an RCT which investigated the therapeutic effect of FES in conjunction with intensive physiotherapy exercises in chronic stroke patients at least one year post stroke 11. Subjects had footdrop but were able to walk without assistance. 2x16 subjects received physiotherapy (coordination exercise, over ground gait training and weight-supported treadmill training (BWSTT)). In addition one arm received FES as well. Subjects were trained 4 times a week for 12 weeks. FES was provided via intramuscular implanted electrodes to 8 muscles. It appears that outcome measures were obtained the day before and after treatment using volitional movement without FES or BWSTT. The primary outcome measure was Tinetti gait score, a 12 point score assessing various gait components. Training significantly improved this score (p<.003) over that of no-fes group, a result that the researchers considered also clinically significant. Fugl-Meyer knee flexion coordination was also significantly improved but there was no improvement in Fugl-Meyer lower extremity coordination, Tinetti balance and the 6 minute walking time. The authors concluded that FES had a significant advantage over no-fes in improving gait components and knee flexion coordination after stroke. This appears to be a well designed trial which offered ambulatory subjects with footdrop, intensive physiotherapy training with and without FES via implanted electrodes. It appears that the subjects were only tested up to the end of the 12 week period and no attempt was made to test the duration of the effect further out. Modest gains were made in improving various components of ambulation but not in walking time. The omission of any reference to use of AFOs or investigation of the durability of the improvements are serious deficiencies. Adverse events and contraindications According to Kottink FES 2 is not appropriate for all stroke patients with a dropped foot and it is impractical to continue to use FES with surface electrodes indefinitely 1. AFOs also have limitations and are said to be uncomfortable and awkward to use 2 : there is limited evidence for their effectiveness 7. Kottink 2 believes that FES is not appropriate for all stroke patients with a dropped foot; patients need to be well motivated, able to stand and walk either alone or with minimal assistance and the muscles that raise the foot should not be denervated. Contraindications are communication disorders, irritation of the skin and limited range of movement. Accident Compensation Corporation Page 6

7 Technical limitations associated with surface stimulators include, lack of selectivity over the muscles and nerves recruited, the sensitivity of the muscle recruitment to electrode placement, and pain and tissue irritation associated with the passage of current through the skin. Costs of typical systems The Ness L300 is initially rented for 2 months at a cost of $ plus GST. The 2 months allows the patient time to try the device and ensure it is the right treatment for them. Surgical Synergies have a pool of rental machines for this purpose. After the 2 month trial if the patient decides to purchase, a new device costs $10, plus GST (minus the rental already paid). The ongoing costs are A new set of electrodes every 2 weeks at a cost of $18.00 plus GST A small battery for the foot sensor every 6 months at a cost of $24.00 plus GST The device requires servicing every 3 years All soft wear upgrades are free and completed at each patient assessment There are no costs for the set up and monitoring of patients by the agent. 4. Excluded Studies A systematic Cochrane review was excluded because it investigated the therapeutic effect of FES on recovery of movement or functional ability after stroke, not specifically for its impact on gait speed or on gait speed as a result of footdrop 12. Two other studies were also excluded, one a non randomised test-retest study because stroke patients only formed 46% of the subjects 13 and the other because it was only based on 8 subjects 14. The National Institute for Health and Clinical Excellence (NICE) conducted a rapid review of the literature on FES for footdrop 15. They concluded that FES for footdrop of central neurological origin appears adequate to support the use of the procedure. This conclusion was reached without what appears to be critical analysis of the papers reviewed. Importantly they made no distinction between trials for the therapeutic effect and the orthotic effect. For this reason the review has not been included as a systematic review. 5. Discussion The orthotic effect of FES on footdrop The quality of the trials included in the systematic review and the papers published since that time have a variety of deficiencies including small numbers, lack of control groups, inappropriate choice of control groups, limited trial and follow up periods and wide variations in trial design and time after stroke. Comparison of results is made difficult by variations in the clinical state of participants and variability in the type of FES device used; many studies used implantable devices and it cannot be assumed that all systems are equally effective. A further factor effecting interpretation is that in many of these trials subjects were already reasonably ambulatory without the benefit of FES. To summarise, the studies reviewed that found positive effects for FES on gait speed for stroke patients with footdrop were - Accident Compensation Corporation Page 7

8 Kottink s systematic review 2 where 7/8 trials compared performance of FES with no AFO The Hausdorf trial on the Ness L where the comparator was no AFO Kottink s RCT 3 where the comparator was use of conventional walking aid. Two other trials that compared effectives of FES with use of an AFO found no net benefit 6 7 for gait speed. When it is considered that Kottink s RCT 3 that reported a positive effect compared to a walking aid clearly had a flawed randomisation with 7/14 in the intervention group using an AFO compared to 15/15 in the control group it would seem reasonable to conclude that there is no good evidence that FES will result in improved gait speeds over that of an AFO. There is some evidence though that use of FES may be superior to no-afo when gait speed is the outcome variable under consideration. Many of the studies report evidence that FES results in other benefits such as on stride time variability and the asymmetry index but there is little evidence that these benefits result in positive functional outcomes for the subject such as the prevention of falls. What constitutes a clinically relevant improvement in walking speed for stroke patients is problematic; Perry 16 has suggested that a clinical improvement in walking speed would be 0.22m/s. Pooled data reported in Kottink s systematic review 2 suggest that the improvement obtainable through use of FES is less than this. Nevertheless improvements of 20 to 30% over baseline may be achieved in selected subjects when the baseline measurements were made without use of an AFO. The therapeutic effect of FES on footdrop Robbins 1 concluded from their meta-analysis that FES training did result in a therapeutic effect but this seems a very generous interpretation of results that are based on three small, heterogeneous and relatively poor quality studies, one of which showed a slightly negative effect of FES and one conducted in the post acute phase which showed a relatively large effect. Daly s RCT 11 appears to have been well designed. They found no therapeutic effect of FES plus physiotherapy on gait speed over physiotherapy alone but modest gains in a range of other parameters of ambulation. As noted the omission of any reference to use of AFOs or investigation of the durability of the improvements are serious deficiencies in this paper. Modest gains are reported for various components of ambulation other than walking time. In a 2004 paper Kottink 2 reported that the literature showed no convincing therapeutic effect. 6. Conclusions The trials reviewed here have serious deficiencies and have been mainly conducted in subjects that were already reasonable walkers. The few trials that compared FES with use of an AFO showed no improvement in walking speed or were seriously flawed; they do show some improvement in parameters other than this but there is no evidence that these improvements result in improved functional outcomes. It is concluded that there is no good evidence to show that FES is more effective than use of an AFO to assist with correcting footdrop in stroke patients either as a therapeutic or as an orthotic effect. Accident Compensation Corporation Page 8

9 It is concluded that that ACC should not routinely purchase FES for treating footdrop in stroke patients either for its orthotic or its therapeutic effect. 7. References 1. Robbins SM, Houghton PE, Woodbury MG, Brown JL, Robbins SM, Houghton PE, et al. The therapeutic effect of functional and transcutaneous electric stimulation on improving gait speed in stroke patients: a meta-analysis. Archives of Physical Medicine & Rehabilitation 2006;87(6): Kottink AI, Oostendorp LJ, Buurke JH, Nene AV, Hermens HJ, MJ IJ, et al. The orthotic effect of functional electrical stimulation on the improvement of walking in stroke patients with a dropped foot: a systematic review. Artificial Organs 2004;28(6): Kottink AI, Hermens HJ, Nene AV, Tenniglo MJ, van der Aa HE, Buschman HP, et al. A randomized controlled trial of an implantable 2-channel peroneal nerve stimulator on walking speed and activity in poststroke hemiplegia. Archives of Physical Medicine & Rehabilitation 2007;88(8): Hausdorff JM, Ring H. Effects of a new radio frequency-controlled neuroprosthesis on gait symmetry and rhythmicity in patients with chronic hemiparesis. American Journal of Physical Medicine & Rehabilitation 2008;87(1): Laufer Y, Hausdorff JM, Ring H. Effects of a foot drop neuroprosthesis on functional abilities, social participation, and gait velocity. American Journal of Physical Medicine and Rehabilitation 2009;88(1): Ring H, Treger I, Gruendlinger L, Hausdorff JM. Neuroprosthesis for Footdrop Compared with an Ankle-Foot Orthosis: Effects on Postural Control during Walking. Journal of Stroke and Cerebrovascular Diseases 2009;18(1): Sheffler LR, Hennessey MT, Naples GG, Chae J. Peroneal nerve stimulation versus an ankle foot orthosis for correction of footdrop in stroke: impact on functional ambulation. Neurorehabilitation & Neural Repair 2006;20(3): Bogataj U, Gros N, Kljajic M, Acimovic R, Malezic M. The rehabilitation of gait in patients with hemiplegia: a comparison between conventional therapy and multichannel functional electrical stimulation therapy. Physical Therapy 1995;75(6): Burridge JH, Taylor PN, Hagan SA, Wood DE, Swain ID. The effects of common peroneal stimulation on the effort and speed of walking. A randomized controlled trial with chronic hemiplegic patients. Clinical Rehabilitation 11 (3): , Alon G, Ring H. Gait and Hand Function Enhancement Following Training with a Multi-Segment Hybrid-Orthosis Stimulation System in Stroke Patients. Journal of Stroke and Cerebrovascular Diseases 12(5) , Daly JJ, Roenigk K, Holcomb J, Rogers JM, Butler K, Gansen J, et al. A randomized controlled trial of functional neuromuscular stimulation in chronic stroke subjects. Stroke 2006;37(1): Pomeroy VM, King LM, Pollock A, Baily-Hallam A, Langhorne P. Electrostimulation for promoting recovery of movement or functional ability after stroke. Cochrane Database of Systematic Reviews 2009(2). 13. Stein RB, Chong S, Everaert DG, Rolf R, Thompson AK, Whittaker M, et al. A multicenter trial of a footdrop stimulator controlled by a tilt sensor. Neurorehabilitation and Neural Repair 20(3)(pp ), Shimada Y, Matsunaga T, Misawa A, Ando S, Itoi E, Konishi N. Clinical application of peroneal nerve stimulator system using percutaneous intramuscular electrodes for correction of foot drop in hemiplegic patients. Neuromodulation 9(4)(pp ), Accident Compensation Corporation Page 9

10 15. National Institute of Health and Clinical Excellence. Interventional procedure overview of functional electrical stimulation for drop foot of central neurological origin Perry J, Garrett M, Gronley JK, Mulroy SJ. Classification of walking handicap in the stroke population. Stroke 1995;26(6): Accident Compensation Corporation Page 10