Abstracts from the FES users meeting May 1st 1998
The use of FES for footdrop in people with multiple sclerosis
Case history of a patient with some problems using a footdrop stimulator
The use of botulinum toxin in conjunction with FES in two patients
The use of FES with children
The Effect of Functional Electrical Stimulation to assist the Gait of Children with Cerebral Palsy
Implantable stimulators for footdrop
CE marking and The new ODFS III
The New ODFS III
Salisbury District Hospital (Medical Physics) Web Page
Questionnaire for physiotherapists using Functional Electrical Stimulation (FES) techniques
Since the last newsletter, in December 1997, the clinical FES service, the research projects and the teaching programme have all developed at quite a pace. In Salisbury we have assessed 173 new patients during the last year and have 323 patients currently using FES. In addition to this, Christine Singleton, in Birmingham, has had so many referrals that she has been able to appoint a third physiotherapist. We have set-up clinics in Stoke-on Trent, a second clinic in Birmingham - jointly with Oak Tree Lane and Moor Green rehabilitation unit, at Kings College Hospital, London and, in the next few weeks in Seaton, Devon. In addition to this we have run two more FES training courses, one here in Salisbury and one in Tunbridge Wells - both over subscribed. To introduce more therapists and medics to the delights of FES we have given a number of one day and half-day lecture / workshops, these have been in Stoke-on-Trent, Devon, Cambridge and London. They have been successful in introducing FES to a lot more people and, I hope inspired them to take it further.
The Action Research project with the Compustim 10B two channel programmable (all singing, all dancing) stimulator is going well; all twelve subjects have been recruited and there are plans now for the next stage. The project may splint into two. The stimulator is larger and possibly cleverer than it needs to be for most uses and a clinical trial with a mini version may be one step; on the other hand, improving it further, possibly by developing different control mechanisms, may be an alternative or additional study. The LARSI project now has secure funding from the Wellcome Trust for a further three years. This has enabled Anna Dunkerly, who worked with us last year while she was studying for her Msc at Southampton, to be employed as the research physiotherapist.
We were unsuccessful in our bid to the MRC for funding to conduct a large randomised Controlled Trial with MS patients. We want to test the long term effects of using FES on the progress of the disease. We are now waiting to hear whether we have won a grant from the Stroke Association for another RCT looking at the combined affect of FES and Botulinum toxin with a sample of sub-acute stroke patients. This is a multi-centre study involving Birmingham and Bournemouth as well as ourselves.
In this newsletter we are publishing abstracts from the papers presented at the FES User Group meeting user back in May and Paul will introduce the new ODFS III. We have also enclosed a questionnaire. We would be very grateful if you could complete it and send it back to us. It will help us to improve the service we provide both to therapists and patients.
The annual FES User Group meeting has been planned for March 3rd next year and if there is a demand for it, a two channel or advanced FES course on March 1st and/or 2nd. Last year we ran a one day course on using the 02CH stimulator for people who had plenty of experience with the single channel stimulator. We could repeat this or, if there was demand, we could run a two day course that would include more on other uses of stimulation, such as voluntary and therapist controlled stimulation and using stimulation as part of more conventional physiotherapy. If you would be interested in this please could you indicate what you would like when you complete the questionnaire.
Three basic, two day courses have been planned - Courses
Don't forget we now have a website on which not only can this newsletter be found but loads more information and connections with other internet sites.
I hope you enjoy reading this newsletter and we'd really love to hear
The Bristol MS Research Unit has been exploring the influence of both therapeutic and functional electrical stimulation (FES) in multiple sclerosis for some years, with the aim of gaining information and extending experience of using FES for people with MS. Much of this work was carried out during an EC funded study FESTIVAL (Functional Electrical Stimulation to Improve Value and Lifestyle ).
The aim of FESTIVAL was to develop a programmable interactive neurostimulator for foot drop in people with multiple sclerosis or stroke. The device was designed to achieve a programmable stimulus output and triggering options tailored to cope with a range of individual gait problems. The concept of having a stimulus envelope that could be "shaped" arose from studies of the activity of anterior calf muscles during normal gait. Recordings of the EMG (electromyogram) during normal gait show that the initial level of EMG activity at the beginning of swing phase is sufficient to keep the forefoot clear of the ground but on heel strike a greater level of activity is observed as the foot is accurately placed. Either one or both of these elements may be missing in subjects with footdrop who may trip, hip hitch, circumduct the leg or "slap" the foot to the ground.
The stimulators and triggering sensors were manufactured between three centres; BMR (Ireland), BEAC (Italy) and the Dept. of Electric & Electronic Engineering at the University of Bristol (UK). Clinical trials with prototypes of the stimulators were carried out in the MS Research Unit at Bristol Royal Infirmary (UK) and in the National Multiple Sclerosis Centre (Melsbroek, Belgium).
Figure 1 below shows the prototype stimulator currently housed in a
standard commercial casing. The stimulus output is through adhesive pad
electrodes and a full foot sole houses both heel and forefoot switch options.
The small black box to the upper right of the picture is a miniature EMG
pre-amplifier. The EMG from agonist or antagonist muscles can be used as an
alternative or combined triggering option in suitable subjects.
The FESTIVAL EMG Triggered Stimulator
Programming options for the FESTIVAL stimulator.
The shape, duration and delay time of the stimulus and stimulus frequency may be programmed as follows:-
Total stimulus envelope duration depends upon the time set for each
section of the 6 phases of the stimulation envelope. This flexibility enables
the therapist to set the device to assist different parts of the swing and
placement phases independently.
Between the two centres a total of 43 people with multiple sclerosis and 13 people with stroke were included in the study, either using the device in the dept. / during rehabilitation or used at home on a daily basis. A further study using the device in stroke has been carried out in Bristol.
All assessments were performed by one physiotherapist at each centre, adhering to strict inclusion and exclusion criteria. Attention was drawn to the required walking speed and distance for the study of 50 metres within 2 minutes ( 0.42m./sec.) This yielded a study group who were mainly ambulant, either non or occasional wheelchair users.
Trigger selection. The choice of triggering modes depended on the ability of the subject. The heel and toe trigger did not require activity in the tibialis anterior muscle whereas the EMG sensor (worn over tibialis anterior of the affected leg ) required sufficient EMG-activity in tibialis anterior in order to trigger a stimulus. The heel switch required an appropriate heel strike and the forefoot switch required contact of the forefoot at the end of the stance phase.
The choice of triggering options and the programmable stimulation waveform (delay, duration and shape) enabled the study to use and evaluate different options according to individual gait patterns.
The study indicated that walking speeds within the MS group were generally unaltered during the use of FES although walking was less effort and some reported being able to walk further before requiring rest. Mechanisms of gait compensation were reduced whilst walking with FES.
The FESTIVAL study has now been completed; the prototype is still in use by the MS Research Unit and it is hoped that further development will take place in the near future.
MS Research Unit, Bristol Oncology Centre, Horfield Road, Bristol BS2 8ED. Tel. 0117 928 3022
Dr. R J S Jones firstname.lastname@example.org uk.
Angela Davies Smith email@example.com uk.
Patient A was the first patient to be referred from Frome to Salisbury for an Odstock Drop Foot Stimulator ( ODFS ) .
He suffered a ( L ) CVA in 1994. The only relevant past medical history was T.I.A.s. He was previously a fit and active man with many interests. Since the stroke his speech and intellectual ability are intact and he has a high level of motivation. His sensory state is good. Despite some signs of active movement proximally in the arm, no useful function has been regained.
By 2 months post-stroke the patient was able to walk unaided at home with an aircast splint, and could manage stairs and slopes . Outside he used a stick. By 9 months he could do a lot of gardening and go unaccompanied on the train to London periodically for meetings.
Although sceptical about the prospective benefits of using an ODFS to correct his drop foot, he decided he would like to be assessed. This assessment was in October 1996. At this stage he described walking indoors as "not a problem", but did feel "unbalanced" and used frequent finger touch on furniture. Outside he used a stick and experienced more difficulty clearing his ( R ) foot off the ground on tarmac, paving stones, uneven ground and slopes. Slopes were easier traversed when the ( R ) foot was lower than the ( L ). Stairs and steps into a train were a problem and walking backwards unbalanced him.
On examination, all activities involved over use of the ( L ) side with decreased weight-bearing on the ( R ) . The ( R ) side of the body was sideflexed and retracted during gait, and swing - through phase was achieved by slight hip hitching and abduction. There was increased tone in quadriceps and plantarflexors but the knee remained in slight flexion during stance-phase. ( Without the AFO there was no heel strike )
On 5th November 1996 Patient A was fitted with an ODFS and responded well with good heel strike. walking speed increased by 1.5%, physiological cost index ( PCI ) fell by 5.5% .
By the next day he was very impressed and no longer sceptical;. Stairs were easier and he no longer needed to concentrate to avoid tripping as he crossed the car park. After 10 days he was finding the stimulator helpful, but -
These teething problems resolved quickly. By the end of November, he has actually been heard to sing whilst walking! For the first time since his stroke he was able to enjoy walking as he no longer had to concentrate all the time to avoid tripping. He did not use it all the time indoors as he found it fiddly to keep turning on and off.
By early December he had walked 1.5 miles with the ODFS. His walking speed was up 6.5% and PCI down 2%. His gait without the stimulator was better than previously, with less hip hitch.
By March 1997 Patient A was delighted with his improved level of safety, confidence and mobility. He had some oedema below the level of the stimulator and was given long-leg tubigrip. By June this was less of a problem. He was wearing the stimulator daily and had improving trunk symmetry with less retraction.
By July 1997, walking speed was up 13.6% and PCI down 15% with the stimulator. Without the stimulator, walking sped had increased by 8% since the first appointment.
Unfortunately, in October he developed blisters under the electrode site. This was probably secondary to inadequate cleaning of the skin and electrodes, leading to the formation of electro-chemical compounds which caused he irritation. He stopped wearing the stimulator for 10 days until the skin had healed and was then fitted with a bi-phasic stimulator to ensure charge balance. He was also given hypo-allergenic electrodes, which were to be changed more frequently. He was asked to clean the skin with alcohol prior to applying the electrodes.
Subsequently he needed to remove the electrodes for part of the day to avoid developing a persistent erythema. In December after wearing the stimulator for 2 long days in London he developed blisters and bleeding and had the to resort to his AFO. After a month he resumed using the ODFS.
In February 1998 his walking speed with the ODFS had increased by 14.7% since first used and the PCI had fallen by 39%. Without stimulation, walking speed was up 11.5% and PCI down 4.5%.
He now uses the stimulator all the time except if a red spot appears, then he stops for a day. He feels that the skin problems he has experienced are related to inadequate skin and electrode cleansing, and advises others to be scrupulous!
The ODFS enables him to move around much more easily and live a more normal life. He has no carryover of dorsiflexion at present and is very dependent on the ODFS. It is a nuisance when pieces of the equipment fail, but new parts usually arrive very quickly. Patient A is very impressed by the efficient service he has received, and also by the great expertise of the research team at Salisbury . He has found everyone very helpful and says the ODFS is a first-rate invention.
By Rosalind Edwards,
I have been using FES for quite some time now, but I had no practical experience with Botulinum Toxin until about 2 years ago, when in the spring of 1996 a new Consultant in Rehabilitation, Dr Margaret Rice-Oxley, took up her post at Worthing & Southlands Hospitals. One of her fields of expertise was the use of Botulinum Toxin in large muscle groups , e.g. Gastrocnemius.
It was decided to set up a clinic where patients with gait problems including foot drop and calf shortening, who might benefit from FES or Botox, would be assessed jointly by Dr Rice-Oxley and myself.
Over a 7 month period we assessed some 32 patients, of whom 14 were accepted for Botox, and 12 for FES.
Among these were a few patients assessed for suitability for FES about whom we were initially doubtful, because of significant shortness of calf muscle, despite having a good response to FES.
The first of these was John, who was first assessed in July 1997. John is a 49 year old ex-navy man who had a stroke in 1994. He lives in an ex-serviceman's home in Worthing. He was referred by the home to Dr Rice-Oxley with a request that she provide a calliper to support his left ankle which was inverting. It was obvious from the outset that John's tendency to invert on weight bearing was a result of his grossly abnormal posture in standing and walking, and that provision of a calliper would not change this. A better solution would be to generally improve his posture and walking pattern, and consider FES to assist dorsiflexion. John's problems included considerable unilateral neglect, together with almost total lack of sensation on his left side. He also showed a very marked predominance of flexion. He walked with a stick. He habitually stood and walked with almost all his weight on his right leg. His midline was centred over this leg, and his left foot was always ahead of his right at all stages of gait. I was unable to get 90 degrees of dorsiflexion passively at his ankle, and he experienced a lot of clonus when standing. The overuse of his right side was obvious in every position and movement, and was extremely well established. However, when the overactivity was reduced, he was found to have good active movement in his left knee and hip. John had significant cognitive problems, mainly short term memory, and therefore his ability to learn and to self monitor was limited. He was however, very determined to improve, and would try whatever we asked. John was largely wheelchair dependent and self propelled.
He was provisionally accepted for FES, provided we were able to make enough gains with a course of treatment to address his problems. John was treated initially for a month using conventional neurophysiotherapy techniques to address the problems mentioned above. Walking was practised using an ODFS, with an aircast for added security. He walked with one or two people, as he immediately reverted to old habits when allowed to walk with his stick. John was not asked to walk except when necessary at home. He was seen in the neurogym twice a week. By the end of August, it was possible to get 90 degrees at the ankle but not at the forefoot. Clonus was still present. There was not enough calf length for John to bring his hip over his foot on stance phase. FES produced a good response, and we were able to use a high intensity because of the insensitivity of his lower leg. However, the increased calf tone was such that the response to stimulation was quite slow, even with almost no ramping. This meant that only a slow walk was possible.
The possibility of using Botox was discussed with Dr Rice-Oxley , and John has 600 units of Botox injected into his left gastro-soleus complex on Friday 29th August 1997. He was seen again on the following Tuesday, when he reported that his calf had felt a lot softer and more relaxed over the weekend. Already it was possible to get a much better contraction using FES. It was also noticed that the speed of the response was greater, enabling a much better rate of walking to be achieved. On the strength of this, it was agreed to order John an ODFS for his own use. Over the following months, John continued to be seen twice a week in the Neuro Gym for several weeks at a time, with breaks in treatment of about a month. During this period John made and maintained slow but steady progress with respect to balance and symmetry. He still walks better with one person than one stick, as his old habits are still very dominant, and he is unable to use his new skills when walking by himself with a stick. It is worth noting that since using FES, John's sensation- in his lower leg at least - has improved noticeably. He is now able to feel stimulation well enough to know when it is uncomfortable and needs to be turned down. He rarely experiences clonus now.
His greatest recent achievement was when he undertook a long train journey (accompanied) to visit relatives, without his wheelchair. John hasn't needed a repeat of the Botox - that single dose gave us the window we needed to make changes which are now, if not reliably permanent, at least allowing him to continue improving steadily.
The second patient was seen in September 1997. His diagnosis was familiar spastic paraparesis , and both Dr Rice-Oxley and myself were particularly interested in this young man because Jane has told me that people with this condition often do very well with FES! Howard is 25 years old, and problems had first been noticed with his walking at the age of 12. When he was first seen in the combined clinic on the 18th of September, in order to get about he was either using a rollator frame , crawling or using a borrowed wheelchair. Howard's lower limbs were in marked medial rotation at the hip, with shortened hip extensors and abductors, and he had extremely short calf muscles, with the right being worse than the left. He walked on his toes with an extreme intoeing gait and stood and walked with very flexed hips. Bt the time Howard was seen at the combined clinic, he had already been given 500 units of Botox into each calf by Dr Rice-Oxley on September 10th, which had brought his heels were nearer the floor though not on it. Howard had a good response to FES, and it was felt that it was worth pursuing.
The initial plan for Howard at this stage included:
Physiotherapy, using manual techniques to increase ROM at the hips, and calf length of both legs. Use of a 4 - channel stimulator to exercise the anterior tibials, and by use of reciprocal innervation, lengthen the posterior tibials of both legs.
Referral to Salisbury, Odstock for an assessment for a 02chs.
We had about 8 weeks before Howard's appointment at Salisbury, and during this time we had made some progress with improvement of range of his hips and calf length.
There were also some problems:
Howard reported that his ankles, especially the right, felt unstable when he stood or walked, and that he was getting ankle and muscle pains.. This was presumably the effect of the Botox on a stable but abnormal system. We had issued Howard 2 aircast splints to protect his ankles, but he didn't always wear them. He also experienced some pain when using the 4 channel on his anterior tibials alone. This was helped by cycling posterior and anterior tibials.
On 14th November, Howard made his first visit to Salisbury, but Jane was not able to get a good lift when Howard was standing, and has some trouble finding effective electrode positions. However, she still felt that there was potential for the system to be useful. It was decided that Howard would be accepted at Salisbury, but that we would do further work before the system was set up. During Howard's twice weekly attendance at Worthing, we continued with existing physiotherapy treatment, and in addition we used 2 single channels ( hand triggered ) to let Howard practice his walking. He also asked Dr Rice-Oxley to repeat the Botox injection in either the right calf alone, or both calf muscles, in December 1997. This would be 3 months after the first injections. We continued to have more trouble with Howard's right leg, which now was demonstrating clonus when he walked with stimulation. It was less of a problem if we cycled anterior and posterior tibials for about 10 minutes before he walked. On the 3rd December 1997, Howard had a further 500 units of Botox injected into his right calf. He was still being seen twice a week for physiotherapy.
On 9th March 1998 Howard visited Salisbury to be set up with a 2 channel system. The foot switches caused some problems but were eventually sited under his metatarsals. Conventional positions were used for the electrodes, and a good lift achieved for both feet. It all looked very promising.
However, we are now experiencing problems from a most unlikely source - Howard himself. Having been keen all along to try something which might improve his walking, we have now discovered that he is hardly wearing his stimulator at all. (our informant is his girl friend). When taxed about it his excuses are that his house is too small to walk in and he is waiting to be rehoused, or it has been raining so he cannot walk outside, etc,etc. He has more pain in his ankles than he used to have, yet he won't wear the aircast splints which would protect them.
It is all very disappointing when so many people have worked on his behalf for months - not to mention the cost, which in these days of cash - starved Hospitals Trusts, is an important consideration. It was hoped that we could encourage Howard into wearing the 02chs on a regular basis and work on the changes that it will make possible in his walking. However, we have currently had to put him on review until he gets his housing sorted out, when we hope that he will feel more inclined to give FES a reasonable try. I still feel that we can offer Howard the chance to be able to use walking as part of his daily routine. I also think that the problems experienced with Howard have provided something as a warning when we are considering using Botox on someone with complex difficulties. This is not to say that I wouldn't use Botox again in someone in a similar situation , but would perhaps approach it with a little more caution.
I have found that to have Botox readily available as an adjunct to FES
has expanded the possibilities of both techniques. Someone like John is
unlikely to need a repeat injection, as one dose enabled us to make changes
which were sufficiently profound as to move him considerably further forward in
his rehab than by FES alone, and enabled him to make the best use of FES. This
is perhaps the most cost effective use in the patients we are seeing in the
clinic. Repeat injections are only given if we are fairly sure the outcome is
going to be favourable, or, as in Howard's case, if we needed to go further
along that road in order to be certain. In all, I would recommend it as an
excellent weapon in the battle to give our patients the opportunity to make the
best recovery of which they are capable.
My initial contact with FES was in 1996 when, following attendance at a half-day FES course I decided to refer a 10 year old girl who, following cardiac surgery, had been left with an unusual pattern of lower limb weakness. Although FES was only partially useful in that particular case, I became increasingly convinced that it could be a useful tool in the treatment of some children on our caseload. So ... two years and two FES courses later, we have regular paediatric clinics with Jane and a steady increasing number of children using FES. Over that time it became obvious that we needed to run some form of pilot study/research project in order to try and assess the effectiveness of FES with a paediatric caseload.
As a 'pre-degree' physiotherapist, with no previous involvement in research the last 12 months have involved a steep learning curve! After initial discussion with my colleagues we have progressed to a point where we have just taken our first 3 children on the study to the gait lab at our local university ( an hours drive away ). We have been fortunate in being able to involve ( persuade!! ) a final year podiatry student from the university to use the project in her dissertation which takes care of much of the paperwork aspect for us! Our criteria for inclusion on the study seems to have changed on a 6 monthly basis; coinciding with Jane's visits! Generally this is because we seem to be 'feeling our way' with regards to the best method of treatment with FES. After an initial phase of using ODFS or dual channel stimulators for a large part of the day we have gradually altered this to the current method where the children ( generally aged 8 years plus ) are initially using a Microstim for 30 minutes a day, they will be re-assessed at the next clinic to decide whether to progress this to a walking stimulator.
After meeting with Sally and Linda ( Paediatric Physiotherapists at Roehampton ) we discussed the possibility of a joint study, with the obvious advantage of increased numbers of children to be included on the trial. However, we all decided that this was not feasible due to differences in local resources available i.e. accessibility of gait lab, treadmill etc.
Our study here in Worthing is looking at any alteration in number of heel-strikes when using FES on children with Cerebral Palsy. Information collected includes GMFM ( Gross Motor Function Measure, a validated measurement tool), PCI , height and weight ( we frequently see a alteration in gait following a growth spurt ( number of heel-strikes during a timed walk on a treadmill (videoed) and gait analysis using 'Vicom'.
We are only at the initial stage of our pilot study and no doubt there
is still a large part of the 'steep-curve' to climb! Hopefully though, despite
differences between our study and Linda and Sally's at Roehampton, both will
help to gather sufficient information so that we can form clearer ideas
regarding the most advantageous use of FES with children.
Neuromuscular Electrical Stimulation has been used successfully in the treatment of neurologically repaired adults for many years. Preliminary data suggests that this form of treatment may be transferable to children with Cerebral Palsy. A preliminary investigation was set up at Queen Mary's University Hospital, Roehampton, to:
Five children were selected from the QMUH Community Paediatric caseload:
|CHILD||AGE||DIAGNOSIS||WALKING ABILITY||PRESENTING PROBLEM|
|1 JL||4 1/2||Diplegia||Independent||Asymmetrical toe gait. Did not tolerate AFO's. Frequent threatening contracture TA|
|2 PC||8||Diplegia||Independent||Asymmetrical toe gait. Valgus foot Did not tolerate AFOs. Frequent falls threatening contracture TA|
|3 LJ||8||Diplegia||Independent||Asymmetrical toe gait. Tight TA|
|4 MA||8||Hemiplegia||Independent||Toe walks on affected side|
|5 HH||8||Quadriplegia (Right Erbs Palsy)||Dependent - Kaye Posture Walker||Bilateral toe gait -unable to stand with flat feet. Tight TAs (just 90º). Marked scissor gait|
All the children were in mainstream school (except No 1, who was still in mainstream nursery at the start of this trial). Numbers 2 and 3 had classroom assistants at school. The purpose and nature of the investigation were explained to the parents, and the expected level of commitment from them.
Baseline measures were taken, including functional assessment, Gait Laboratory data and video analysis.
A parent questionnaire addressing quality of life and functional gait issues was completed at 4 months.
Set up with Odstock Drop Foot Stimulator (ODFS) on more affected side, stimulating the anterior tibial muscles as described in the Adult literature, and the affects assessed. When the optimum correction was achieved, the parents/children were instructed how to set up and use the machine. They were followed up at regular intervals.
Was set up with a four-channel exercise stimulator to the anterior tibials and calf muscles on both legs.
An immediate change in gait pattern was noted as the children used the stimulator. A more "normal" gait was achieved, with increased frequency of heel contacts and heel strikes. The improvement became proportionally less reliable as walking speed increased.
While using the stimulator analysis from Gait Laboratory data at six weeks showed on one child for example,:
During exercise stimulation he was able to achieve a flat foot stance. At six weeks, a marked reduction in the scissor motion during swing phase of the right leg was noted.
Child 1. JL Despite achieving good gait correction and a functionally improved gait, (parent reported child could walk further and with fewer falls), he discontinued use of FES. This coincided with transfer into full time school, and it was not practical to continue using FES at that time, though it may be very useful to him in the future.
Child 2. PC After an initial period of stimulation to the anterior tibial muscles, we tried stimulating calf muscles, and achieved a better correction of gait. She continues to use FES with good effect, though problems remain with the valgus position of her foot.
Child 3. LJ Has discontinued use of FES. Good gait correction and functional improvement were noted, but without appropriate support in school and at home, he was unable to manage the practicalities himself. We hope to reintroduce the FES when he has better support in school.
Child 4. MA Continues to use the system to good effect.
Child 5. HH Discontinued use and has opted for Botulinum injections. We are investigating the possibility of restarting FES, not as an exercise stimulator but in active walking 6 months post injection.
Type of study
An ABA approach will be used with children who present with a toe-walk gait and for whom alternate methods of gait correction/improvement have been less successful than desired. It is not possible to use a placebo or to use double blind studies due to the nature of the intervention
The time is ripe to start using implanted stimulators to correct footdrop. A recent survey of ODFS users found that 44% found it difficult to place the electrodes and 22% suffered from skin allergy under the electrodes. A well-designed implant will avoid these difficulties.
Implanted stimulators either have an internal power source, normally a battery, or they receive their power through the skin, usually by radio-frequency magnetic induction between a coil in the implant and one worn nearby, close to the skin. If we want to make an implantable stimulator which works like the ODFS, in which the stimulation is triggered by a foot-switch, we must send this stimulation signal to the implant and it is therefore convenient to use the same coupled coils for the trigger signal. There is however an unavoidable complication. With ODFS and other surface electrode footdrop stimulators, the dorsiflexion movement is adjusted, ideally so that there is neither concomitant inversion nor eversion, by moving the electrodes on the leg. With implanted electrodes, the adjustment can only be done after the operation if two channels (stimulation electrodes) are available, one which inverts and one which everts, so that the user can set their relative intensities to get a satisfactory ankle movement.
This simple two-channel stimulator (in Ian Swain's terminology), used with a ODFS-type foot-switch, may be the best type of implant for the first implantations because it will be most familiar. However, if the results are encouraging, there are further possible developments. The object of the first improvement will be to reduce the extent of surgery by placing one electrode "cuff" on the peroneal nerve above the branch to the peronii and the anterior tibial muscles: adjustment of the movements will be possible because the cuff will have three or four separate stimulating electrodes inside. This electrode configuration has been tested successfully in Cleveland but never applied to patients. In order to carry out a patient trial, a rather special selective stimulator is required which, to be small enough to implant, should use largely integrated (silicon) circuitry. Martin Bugbee at UCL has been working on a customised integrated circuit for this purpose since 1994.
The second development will avoid the need for an external footswitch, and therefore also difficulty which some patients have in connecting the footswitch, by picking up a suitable signal inside the body. This will make the device easier to use and may be more reliable. One exciting possibility is to use the natural sensory signal present in the cutaneous afferent nerves from the foot. Sinkjaer's group in Denmark have shown that it is possible with an electrode on the sural nerve to control a footdrop stimulator in a stroke patient (however he had wires coming through the skin in this demonstration). We are at present making, in a collaboration with Sinkjaer, a telemeter for transmitting such ENG signals out of the body so that more extensive trials may be acceptable. These cutaneous ENG signals from the sole carry information about when the foot is in contact with the ground, and therefore control the stimulation in a manner analogous to the usual foot-switch. However, there may be an even better input: the electromyographic signals which are probably still present in tibialis anterior. In this case, the sensing electrode would be placed in or on the muscle, rather than around a nerve, and would indicate when the user was trying to dorsiflex.
Designing and building new implanted devices of this complexity takes a
long time. One of our goals, in the Implanted Devices Group, is to develop an
advanced stimulator for footdrop which incorporates both the internal sensing
and selective stimulation. By the end of 1998, we should have two separate
implants for these functions but trials can not begin until approval from the
Medical Devices Agency has been obtained. Further work will be required to make
the all-in-one device with both sensing and stimulation. While this engineering
development is under way, we should like to see clinical experiments being done
to compare the signal sources and to find the best method of stimulation.
From June this year it became compulsory for all medical equipment sold throughout the European Union to carry the CE mark. The CE mark indicates that the equipment is made under a maintained quality system and that it meets all necessary EU directives. I am pleased to say that The Departments of Medical Physics and Biomedical Engineering has been assessed by BSI and been awarded an EC Certificate enabling us to CE mark our stimulators.
All new stimulators will be CE marked. However we still have a few ODFSs in stock which we are able to pass on to you because they were made before June and these do not have a CE mark.
For some time we have been talking about an upgraded version of the ODFII. Finally we have the new model in production. The old version had several disadvantages which have been addressed in the new model:
The old ODFSII is being phased out and will be replaced by the new version. So far feed-back has been favourable, the new version being liked by users and clinicians. It is not thought to be any more difficult to set up despite its extra functions. The price of the ODFSIII is the same as the ODFSII. As always we welcome any feed-back from you on our equipment or service. Any queries or comments please contact Paul tel. 01722 336262 Ex 4060 email:- firstname.lastname@example.org
1.5" Pals Plus Electrodes
We have just arranged a large bulk-buy of Pals Plus 1.5" electrodes. This is because they are no longer available from the distributor. Prices as before. We should have the electrodes by the end of November.
At the second FES user meeting May 1st, I introduced the departments new web page. As I only had a short time to present the web site, listed below is a summary of what can be found by visiting the site:-
Functional Electrical Stimulation (FES)
Which includes FES topics such as Research, Development and Clinical Service carried out at Salisbury District Hospital. This section also contains an interesting list of relevant papers and general information about The Odstock Dropped Foot Stimulator, Improved Dropped Foot Correction - 2 Channel Stimulators, Identification of Suitable Candidates for Dropped foot stimulators, FES for the Upper Limb in Stroke, Paraplegic Standing, The LARSI Project, Clinical Evaluation of the Free Hand System and Long pulse stimulation for denervated muscle.
This section includes literature on Restoration Of Hand Function For Tetraplegics Programme and Electrical stimulation exercise to improve hand function and sensation following chronic stroke. Paul Taylor, Jane Burridge, Sean Hagan, Ian Swain.
Here you can find the latest list of courses run by the team here along with contact names/numbers. There is also a form you can fill out to apply to come on a course, simply type in your details and press the 'SUBMIT' button.
Staff Contact Page
You can use this page to contact any member of staff. If you press on a name an e-mail box pops up, you can type the message and simply press send.
This page enables you to jump to somebody else's web site. Most of the these sites are FES related.
See what is happening at Medical Engineering Department.
Mattress & Cushion Trials
This page gives brief details on the tests carried out on pressure relieving mattresses and cushions.
For those of you who haven't seen it yet, our web site address is:
We try our best to keep these pages updated and we hope you find them useful, so don't forget to add it to your 'bookmarks' list. And if there is anything you would like to add to our page e.g. the work you are carrying out, please do not hesitate to contact us and we can add it on.
Don't be bewildered if you've never used the Internet before-there will be somebody around to show you how to access our web-site (or any others).
There are now over 100 physiotherapists who have done the Salisbury course and are using FES as part of their clinical practice. As part of our standard procedures we audit the use of stimulators built in this department. Please could you help us to identify the needs of therapists using FES and improve our service by completing this questionnaire.
Please tick the Yes or No box for each question. If you answer Yes to any questions please use the reverse side of the form to comment further.
Thank you - please add any comments on the other side of the page
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