Functional Electrical Stimulation

Transcription

1 Functional Electrical Stimulation Mr. Deon Bührs 22/04/2002

2 What is Functional Electrical Stimulation 4 The Odstock Dropped Foot Stimulator 4 Development 4 Approvals and recommendations 5 Current use and findings 5 What does using the system involve? 5 Future developments 6 The Odstock Two-Channel Stimulator 6 Development 6 Current use 6 What does using the system involve? 7 Future developments 7 The Microstim 2 7 Development 7 Current use 8 What does using the system involve? 8 Future developments 8 The Four-Channel Exercise Stimulator 9 Development 9 Current use 9 What does using the system involve? 9 Functional Electrical Stimulation & Stroke Rehabilitation 10 Functional Electrical Stimulation & Multiple Sclerosis 11 Functional Electrical Stimulation & Spinal Cord Injuries 11 Incomplete injuries 11 Tetraplegics 12 2

3 Where can I go for Treatment? 13 How is the Treatment Funded? 13 Clinical Evidence & Reports 14 Abstracts on Stroke and Multiple Sclerosis 14 Abstracts on Tetraplegia 14 Publications 15 3

4 What is Functional Electrical Stimulation? Functional Electrical Stimulation is the clinical application of a small electric current to the intact nerves of the body, in order to trigger a muscle contraction. This contraction is then incorporated into a functional activity, for example walking. A clear distinction needs to be made between Therapeutic Stimulation and Functional Stimulation. The former being of an exercise orientation, where one would relax whilst the stimulation works on its own. Functional Electrical Stimulation on the other hand, incorporates this elicited muscle movement into an everyday activity, like standing, walking, reaching out etc. Much work has been done in the field of FES world wide, but one of the largest clinical applications of FES is found in Salisbury District Hospital, Department of Medical Physics, England. They have up to now seen more than 1100 patients, trained more than 300 clinicians, and employ an active Research and Development programme. Their clinical service began in 1994, and they currently employ Clinical Engineers, Physiotherapists, Occupational therapists and technicians to this end. The following is a list of the Stimulators designed in Salisbury, under the Department of Medical Physics, together with their applications. All systems are CE marked, and are BSI (British Standards Institution) Registered. The Odstock Dropped Foot Stimulator Development The Odstock Dropped Foot Stimulator (ODFS) was developed at the Medical Physics Department of Salisbury District Hospital in Wiltshire, England over a period of several years under the support of the National Health Service (NHS) and additional grants. The development culminated in a Randomised Control Trial being conducted from , after which the Development and Evaluation Committee (DEC) recommended its use for the treatment of Dropped-foot in the NHS. 4

5 The development and research was conducted by a multi-disciplinary group of Clinical and Electronic Engineers and Physiotherapists. This culture of teamwork and continual research and development continues to today. The team now comprises of 3 Physiotherapists, 2 Occupational Therapists, a Medical Physicist, 4 Clinical Engineers and technical and secretarial staff headed by Professor Ian D. Swain. The team is affiliated to the University of Bournemouth. Use of the ODFS has extended to other countries, due to its success as an active orthosis in assisting patients into the final stage of gait re-education and rehabilitation. These countries include Belgium, Hong Kong, Denmark, Italy, Spain and Switzerland. It is now that the possibility of patients in South Africa receiving this treatment is a reality. This is currently offered on a private patient basis, pending further funding agreements. Approvals and recommendations Approval for this treatment has been granted on an individual basis by many Health Authorities in the United Kingdom, on the recommendation of several independent bodies. These are: 1. The Development and Evaluation Committee Report, The Royal College of Physicians, CE mark classification. Further findings reveal the potential cost saving benefits of reducing the occurrence of falls. These when expressed in monetary value, outweigh the initial expense of the equipment. This will be worked out in savings benefit in the South African market soon. Current use and findings Over 1000 patients have currently used the stimulator system, of which approximately 75% are Stroke victims, 15% Multiple Sclerosis sufferers, and the remaining 10% being comprised of patients with incomplete Spinal Cord Injuries, Traumatic Brain Injuries, and Cerebral Palsy. The center in Salisbury has trained over 300 clinicians in the use of the single-channel stimulation system, and has now set up 5 independently run clinics across the UK. The Medical Physics Department in Salisbury has been fully supportive of the initiative in establishing an FES clinic in South Africa, and will continue to supply support and back-up service to this end. A service is currently available in Pretoria East, under the care of a Physiotherapist, and Neurosurgeon. What does using the system involve? The single-channel Dropped Foot system is the size of a pack of cards, easily attached to the waistband or belt, or even carried concealed in a pocket. Electrical stimulation is passed through the skin via a lead to self-adhesive electrode pads, which are placed over the lower leg. The impulses then stimulate the muscles needed to lift the foot upward via the nerve fibers. The timing of stimulation is controlled internally by the stimulator, relying on a foot switch, which is placed inside the shoe. This then synchronizes the stimulation cycles with each individual walking pattern. If a satisfactory response is found at the initial assessment, two appointments on consecutive days are needed in order to train the patient and/or carers in setting up the system correctly. This is then followed up with appointments 6 weeks later, then 3 months, and 6 months apart. Once the system becomes part of daily life, the follow-up appointments will be carried out 6 monthly. The system is ideally used on a daily basis, for the whole day, for as long as it is required. Other possibilities involve adding therapeutic exercise stimulation to the daily program, or a two-channel device, stimulating an additional muscle group. 5

6 Future developments Current trials are underway exploring the possible use of an implanted stimulation unit. This involves the implantation of the electrodes around the nerve fibers, but still employs an external control unit and footswitch. A policy of continual upgrading and improvement is employed. The Odstock Two-Channel Stimulator Development The 2-channel stimulator developed as a logical progression on the single-channel Odstock Dropped Foot Stimulator. It was found that in some clinical cases it was necessary to stimulate another group of muscles to improve the global gait pattern. Current use The 2-channel stimulator is currently used in a variety of cases, coordinating another group of muscles to the walking cycle. The following algorithms have been developed: Bilateral dropped foot stimulation (especially in MS and incomplete Spinal Cord Injuries) Dropped foot with Calf stimulation Dropped foot with Hamstring stimulation Dropped foot with Quadriceps stimulation Dropped foot with Gluteal stimulation Dropped foot with Triceps stimulation Bilateral Quadriceps stimulation 6

7 By using these, we can for example improve the initiation of swing-phase by stimulating the hamstrings, or improve hip protraction in the stance-phase of walking by stimulating the gluteal muscles. What does using the system involve? This stimulator is only prescribed in some cases, and only after regular use of the single channel system. It may however be set-up as the primary intervention of bilateral dropped foot, for example in Spinal Cord Injured patients, or Multiple Sclerosis sufferers. The size of this stimulator is slightly larger than the ODFS. The user will be waring 2 sets of electrodes, with 2 leads. In some cases it may also be necessary to use two foot-switches. Furthermore, there is no difference from the ODFS as to frequency of use and follow-up appointments required. This stimulator would then replace the initial unit. Future developments This system is currently being redesigned at Salisbury District Hospital, and is being used in a multicenter trial looking at the potential benefits of this system over the conventional use of a dropped foot splint (ankle-foot orthosis). The Microstim 2 Development This stimulator was also developed by the Salisbury team, as the need for therapeutic exercise stimulation arose in the clinical environment, to augment the functional stimulation work. It has two channels of stimulation, able to deliver various frequencies and independent intensities via surface electrodes. 7

8 Current use The applications of the Microstim 2 vary, but in essence remain of therapeutic input. The current uses of exercise stimulation include: 1) Shoulder pain and subluxation ( gapping of the shoulder joint) 2) Arm stimulation including the hand and forearm. 3) Leg stimulation to improve the affectivity of the Dropped Foot Stimulator 4) Facial stimulation 5) General control of spasticity, and resting tone. These applications are often used in Stroke patients, but also Multiple Sclerosis and Facial Palsy s like Bell s Palsy. What does using the system involve? Exercises are usually prescribed twice a day, slowly increasing the time of stimulation until stimulating for approximately 30 minutes twice daily. The electrodes will be applied only for this period, during which functional activities can be carried out as prescribed by a Physiotherapist. The mode setting on the stimulator allows for the integration of stimulating muscle groups, or individual alternating stimulation. Future developments This stimulator is also currently being redesigned, although there will be no technical changes to the current device. 8

9 The Four-Channel Exercise Stimulator Development In essence, just a 4-channel version of the Microstim 2, although it does allow for parameter changes by the clinician allowing more versatility. It also allows for variable integration of the separate channels, thereby lending itself to more functional integration of various muscle groups. Current use Uses include facilitating a reaching movement of the arm, shoulder stimulation, and in some incomplete Spinal injured patients, for muscle retraining. It is also a useful aid to Physiotherapy reeducation of movements, when using a Wow-pedal. This enables the therapist to bring on the stimulation using a foot pedal, to encourage synergistic muscle activation in conventional physiotherapy treatments. What does using the system involve? Similar application is utilized as the Microstim 2, but this can be used in conjunction with Physiotherapy. 9

10 Functional Electrical Stimulation & Stroke Rehabilitation Conventional therapy in improving mobility in Stroke patients involve the use of a wheelchair or walking aids like a walking frame, stick or crutches. If a patient is able to walk about, this ability is often hampered by a dropped foot. This occurs when the muscles of the lower leg are not strong enough to lift the foot upwards when bringing the foot forwards off the ground. As a result, the foot catches resulting in stumbling and even falling. To avoid this patients often compensate by either hitching the hip, or swinging the leg outward. The conventional treatment might include the use of a dropped foot splint, or Ankle-Foot Orthosis (AFO), which is a plastic support worn inside the shoe. FES offers an alternative to this treatment, encouraging active movement of the foot, and by constantly taking the foot through full range of movement with walking, avoids stiffening up of the ankle. Improvements are reflected in objective tests, recording the speed of walking and the effort of walking by measuring the heart rate. Common reports are of walking being made easier, quicker, and safer, with patients feeling a lot more confident in walking about. The problem of having to wear larger shoes in order to fit the splint in is also solved. Carry-over of these improvements is often found when looking at unstimulated walking too, indicating a training effect of stimulation. Other improvements are also found in decreasing spasticity and improving range of movement, and peripheral circulation. Improved symmetry is also encouraged due to the nature of the foot switch-stimulation relationship. Two channels of stimulation are also used at times, in order to integrate another set of muscles into the walking pattern. This might include the hamstring muscles to improve the knee bending when bringing the foot forwards, or to the gluteal muscles to bring the body over the effected leg when standing. Exercise stimulation may also be applied to the leg in order to improve the effect of the abovementioned systems. This could be done using the 2- or 4-channel stimulator. Improvements have been found using exercise stimulation to the shoulder, easing shoulder pain, and reducing subluxation. This is when a gap appears in the shoulder joint, as the muscles are unable to keep the arm in place. There have also been reports of improved sensation following electrical stimulation. 10

11 Functional Electrical Stimulation & Multiple Sclerosis The application of FES to Multiple Sclerosis induced weakness is possible, as the nerve fibers are still intact, making it an upper motor neuron disease. The applications are focussed on the clinical presentation of the patient, and are often in the form of a single channel of stimulation to improve a dropped foot. A dropped foot is brought on by the inability of the muscles of the foot to lift it up during the swing phase of walking. This often results in tripping and even falling. A conventional approach might include Physiotherapy rehabilitation, the use of walking aids, and at times, an ankle-foot orthosis is used to keep the foot in a lifted position. FES offers an alternative to this treatment, encouraging active movement of the foot, and by constantly taking the foot through the full range of movement with walking, avoids stiffening up of the ankle. Improvements are reflected in objective tests, recording the speed of walking and the effort of walking by measuring the heart rate. Common reports are of walking being made easier, quicker, and safer, with patients feeling a lot more confident in walking about. Carry-over of these improvements may be found when looking at unstimulated walking too, although due to the progressive nature of this disease, are not as pronounced as in Stroke patients. Other improvements are also found in decreasing calf tone and improving range of movement, and peripheral circulation. Improved standing symmetry is also encouraged due to the nature of the foot switch-stimulation relationship. Two channels of stimulation are also used at times, in order to integrate another set of muscles into the walking pattern. This might include the hamstring muscles to improve knee bending when bringing the foot forwards, or to the gluteal muscles to bring the body over the effected leg when standing. Bilateral dropped foot stimulation is not uncommon in MS patients. Exercise stimulation may also be applied to the leg in order to improve the effect of the above-mentioned systems, or to the upper limb. This could be done using the 2- or 4-chnnel stimulator. Functional Electrical Stimulation & Spinal Cord Injuries Incomplete injuries. The electrical stimulation parameters used in the Odstock range of stimulators allows for nerve stimulation only, and is therefore unable to induce any movement in denervated muscles. This denervation would occur as a result of a lower motor neuron injury. As a rough guideline, this occurs in patients with a spinal cord injury of the level of L1 (Lumber 1) and lower. When being used in patients with a lesion higher than this, in order to achieve any sort of functional improvement, there needs to be some element of incompleteness to the clinical picture. In other words there needs to be some specific element absent from an already moderately functioning lower limb, or arm. The patients usually seen are those mobile using some form of walking aid already, and are perhaps using an Ankle foot orthosis to improve the walking by keeping the foot in a semi lifted position. 11

12 FES offers an alternative to conventional treatment, encouraging active movement of the foot, and by constantly taking the foot through full range of movement with walking, avoids stiffening up of the ankle. Improvements are reflected in objective tests, recording the speed of walking and the effort of walking by measuring the heart rate. Common reports are of walking being made easier, quicker, and safer, with patients feeling a lot more confident in walking about. Carry-over of these improvements is often found when looking at unstimulated walking too, indicating a training effect of stimulation. Other improvements are also found in decreasing calf tone and improving range of movement, and peripheral circulation. Improved standing symmetry is also encouraged due to the nature of the foot switchstimulation relationship. Two channels of stimulation are also used at times, in order to integrate another set of muscles into the walking pattern. This might include the hamstring muscles to improve the knee bending when bringing the foot forwards, or to the gluteal muscles to bring the body over the effected leg when standing. The quadriceps muscles may also be stimulated to improve standing stability. Exercise stimulation may also be applied to the leg in order to improve the effect of the abovementioned systems, or to the upper limb for therapeutic stimulation. This could be done using the 2- or 4-chnnel stimulator. Tetraplegics Patients who have suffered from a cervical cord injury usually have limited upper limb function, and are wheelchair dependent for mobility. Conventional treatment involves physiotherapy and occupational rehabilitation, and tendon transfers may be done to improve hand function. NeuroControl, a company based in the USA has now developed the Freehand System", which involves the implantation of 8 electrodes into the muscles of the hand and forearm. These are stimulated via an external system by transmitting radio frequencies to an implanted receiver unit. This is often done together with tendon transfers, and enables the patient to perform tasks using a shoulder control to bring on different movements of the hand. The patient is then able to grasp objects, and manipulate them spatially. Selection criterion is strict, as some patients may benefit from tendon transfers alone. Usual candidates are C5/6/7 injured patients. Currently this surgery is not being performed in South Africa, but the Salisbury unit in the UK, others in Europe, Japan, Australia, Canada and the USA do. For more information, go to the NeuroControl website. Other possibilities include abdominal stimulation to improve respiratory function by improve coughing, and decreasing the occurrence of orthostatic hypotention (a lowering of the blood pressure in response to body position, resulting in dizziness/fainting). 12

13 Where can I go for Treatment? Treatment is currently available in Garsfontein East, Pretoria and at the Netcare Rehabilitation Hospital in Auckland Park, Johannesburg. Plans are underway to set up other clinics in Cape Town and Durban. Address: Bührs Physiotherapists 51 Carstens Crescent Garsfontein East Pretoria South Africa Cell number: Telephone/fax: address: d.buhrs@proffessa.co.za How is the Treatment Funded? We are currently busy with negotiations with the Private medical aid schemes, in order to secure funding for this treatment. Until this is finalised, patients will need to pay upfront for the cost of the equipment, and try to claim this back from their medical aid schemes themselves. We can advise you in this and assist in the application for an Ex Gracia payment, should this be nessesary. Initial assessments will be carried out in the usual way of a Complex Physiotherapeutic evaluation, which is funded by most medical schemes. The follow-up clinic appointments with the Physiotherapist should be covered in the usual way by those medical aids with Physiotherapy benefits. These followups are on average 5 in the first year, totaling 6; and then 2 per year from then onwards. The equipment costs are currently the responsibility of the patient. 13

14 Clinical Evidence & Reports 1. Abstracts on Stroke and Multiple Sclerosis Patients' Perceptions of the Odstock Dropped Foot Stimulator (ODFS) Clinical use of the Odstock Dropped Foot Stimulator. Its effect on the Speed and Effort of walking The effects of common peroneal stimulation on the effort and speed of walking. A randomised controlled trial with chronic hemiplegic patients The effect of common peroneal nerve stimulation on quadriceps spasticity in hemiplegia Correction of Bi-lateral Dropped Foot using the Odstock 2-Channel Stimulator (O2CHS) The Relationship between abnormal patterns of muscle activation and response to Common Peroneal nerve stimulation in Hemiplegia Different muscle activation patterns, identified during walking, in people with spastic Dropped Foot Electrical stimulation exercise to improve hand function and sensation following chronic stroke. Pilot trial to determine Control algorithms and patient selection criteria for Two- Channel Stimulation following Stroke The efficacy of Functional Electrical Stimulation in improving walking ability for people with Multiple Sclerosis Development and Evaluation Committee Report: Common Peroneal Stimulation for the Correction of Drop-foot United Kingdom Clinical guidelines for Stroke-The Royal College of Physicians 2. Abstracts on Tetraplegia Clinical experience of the NeuroControl Free Hand Neuro Prosthesis for Tetraplegic hand function Deltoid Triceps Transfer and functional independence of people with Tetraplegia A portable system for closed loop control of the paralysed hand using functional electrical stimulation Clinical Experience of the NeuroControl Freehand System Electrical stimulation of abdominal muscles for control of blood pressure and assisted cough in a C4 level tetraplegic 14

15 Publications 1. Taylor PN, Ewins DJ, Fox B, Grundy D, Swain ID. Limb blood flow, cardiac output and quadriceps muscle bulk following spinal cord injury and the effects of training for the Odstock Functional Electrical Standing System. Paraplegia 31 (1993) Taylor PN, Burridge JH. Development and experience in use of an electronic stimulator for correction of dropped foot in early gait re-education of subjects following CVA. Therapy weekly Taylor PN, Fox BA, Ewins DJ, Swain ID, Exercise procedure and treatment routine for preparation of paraplegics prior to standing using FES. Ed. Cliford-Rose F, Jones R, Vrbova G. Neuromuscular Stimulation: Basic Concepts and Clinical Practice. Demos 1989 USA 4. Ewins DJ, Taylor PN, Crook SE, Lipcyznski RT, Swain ID. Practical low cost stands/sit system for mid-thoracic paraplegics. J.Biomed. Eng (2): Burridge J, Taylor P, Hagan SA, Wood DE, Swain ID. The effect on the spasticity of the quadriceps muscles of stimulation of the Common Peroneal nerve of chronic hemiplegic subjects during walking. Physiotherapy vol. 83, no 2, pp Burridge, J. Taylor, P. Swain, I. (1997) Clinical Experience of the Odstock Drop Foot Stimulator. Artificial Organs 21 (3): Burridge, J. Taylor, P. Hagan, S. Swain, I (1997) The effect of Common peroneal stimulation on the effort and speed of walking. A randomised controlled trial with chronic hemiplegic subjects. Clinical Rehabilitation 11: Rushton DN, Barr FMD, Donaldson N de N, Harper VJ, Perkins TA, Taylor PN, Tromans AM. Selecting candidates for a lower limb stimulator implant programme: a patient-centred method. Spinal Cord (1998) Burridge JH, Swain ID, Taylor PN Functional electrical Stimulation: a review of the literature published on common peroneal nerve stimulation for the correction of dropped foot. Reviews in Clinical Gerontology : Taylor PN, Burridge JH, Dunkerley AL, Lamb A, Wood DE, Norton JA, Swain ID. Patient's Perceptions of the Odstock Dropped Foot Stimulator (ODFS). Clin. Rehab. 1999; 13: Paul Taylor, Jane Burridge, Anna Dunkerley, Duncan Wood, Jonathan Norton, Christine Singleton, Ian Swain. Clinical audit of 5 years provision of the Odstock Dropped Foot stimulator (ODFS). Artif Organs Vol.23, No. 5, May AH Woodcock, PN Taylor, DJ Ewins, Long Pulse Biphasic Electrical Stimulation of Denervated Muscle. Artif Organs Vol.23, No. 5, May Taylor PN, Burridge JH, Dunkerley AL, Wood DE, Norton JA, Singleton C and Swain ID Clinical Use of the Odstock Dropped Foot Stimulator. It s Effect on the Speed and Effort of Walking. Arch Phys Med Rehab.1999; 80: SE Crook, PH Chappell. A portable system for closed loop control of the paralysed hand using functional electrical stimulation. Medical Engineering and Physics 20 (1998) Swain ID, Bader DL. The measurement and effects of interface pressure on soft tissues. Journal of Engineering in Medicine. In press,

16 16. Burridge JH, McLellan DL. Relation between abnormal patterns of muscle activation and response to common peroneal nerve stimulation in paraplegia. Journal of Neurology, Neurosurgery and Psychiatry, In press, Dunkerley AL, Ashburn A, Stack EL. (2000) Deltoid triceps transfer and functional independence of people with tetraplegia. Spinal Cord 38, Published Abstracts 1. Ewins DJ, Taylor PN, Swain ID, A functional closed loop stand/sit system for mid-low thoracic paraplegics. Advances in the control of human extremities 10. ed. Popovic D Belgrade: Nauka Taylor PN, Ewins DJ, Swain ID. The Odstock closed loop FES standing system. Experience in clinical use. The Ljubljana FES Conference, Ljubljana, Slovenia ISBN pp Taylor PN, Burridge JH, Hagan SA, Swain IDS. Electrical stimulation exercises to improve hand function and sensation following chronic stroke. Pro. 5th Vienna International Workshop on Functional Electrostimulation 1995 ISBN pp Burridge J, Taylor P, Hagan SA, Swain ID. Experience and clinical use of the Odstock Dropped Foot Stimulator. (ODFS) Pro. 5th Vienna International Workshop on Functional Electrostimulation 1995 ISBN pp Barr FMD, Harper VJ, Rushton DN, Taylor PN, Phillips GF, Hagan SA, Wood D. Screening and assessments for a lumbosacral anterior root stimulator implant program. Pro. 5th Vienna International Workshop on Functional Electrostimulation 1995 ISBN pp Taylor. PN Burridge JH, Dunkerley A, Wood D, Norton J, Singleton C, Swain ID Long term follow up of 160 users of the Odstock Dropped Foot Stimulator. Pro. 6th Vienna International Workshop on Functional Electrostimulation 1998 ISBN Perkins TA, Donaldson N de N, Dunkerley AL, Hatcher, Tromans AM, Wood DE. Development of paraplegic leg powered cycling with the Lumbo-sacral Anterior Root Stimulator Implant. 1999, 4th annual IFESS conference pp ISBN Wright PA, Burridge JH, Ewins DJ, Mann GE, Mclellan DL, Swain ID, Taylor PN, wood DE. The Compustim 10B in stroke: Control algorithms and patient selection criteria th annual IFESS conference pp ISBN Burridge JH, Wood DJ, Taylor PN, McLellan DL The relationship between abnormal patterns of muscle activity and response to common peroneal nerve stimulation. 4th annual IFESS conference pp ISBN Ewins DJ, Write PA, Burridge JH, Mann GE, Swain ID, Taylor PN, Wood DE. The compustim 10B Programming interface. 4th annual IFESS conference pp ISBN Taylor PN, Wright PA, Burridge JH, Mann GE, Swain ID. Correction of Dropped Foot using the Odstock 2 Channel Stimulator (O2CHS). 4th annual IFESS conference pp ISBN Swain ID, Burridge JH, Johnson CA, Mann GE, Taylor PN, Wright PA. The efficacy of functional electrical stimulation in improving walking ability for people with multiple sclerosis. 5th Annual Conference of the International Electrical Stimulation Society, (ISBN ), pp , Aalborg, Denmark, June

17 13. Taylor PN, Esnouf JE, Hobby J. Clinical experience of the NeuroControl Freehand system. 5th Annual Conference of the International Electrical Stimulation Society, (ISBN ), p , Aalborg, Denmark, June Mann GE, Swain ID, Cole R. Initial experience in the use of functional electrical stimulation in a variety of neurological conditions resulting in facial palsy. 5th Annual Conference of the International Electrical Stimulation Society, (ISBN ), pp , Aalborg, Denmark, June Taylor PN, Tromans A, Swain ID. Electrical stimulation of abdominal muscles for control of blood pressure and assisted cough in a C4 level tetraplegic. 5th Annual Conference of the International Electrical Stimulation Society, (ISBN ), pp , Aalborg, Denmark, June Mann GE, Burridge JH, Ewins DJ, McLellan DL, Swain ID, Taylor PN, Wood DE, Wright PA. Optimising two-channel stimulation to improve walking following stroke. 5th Annual Conference of the International Electrical Stimulation Society, (ISBN ), pp , Aalborg, Denmark, June Norton JA, Donaldson N de N, Day BL, Dekker L, Perkins TA, Wood DE, McFadden C, Tromans A. The determinants of posture in paraplegics standing using lumbar anterior root stimulation. 5th Annual Conference of the International Electrical Stimulation Society, (ISBN ), pp , Aalborg, Denmark, June