For Functional Electrical Stimulation Research Articles

Automatic synthesis of synergies for control of reaching — hierarchical clustering

In this paper we describe a novel method for determining synergies between joint motions in reaching movements by hierarchical clustering. A set of recorded elbow and shoulder trajectories is used in a learning algorithm to determine the relationships between angular velocities at elbow and shoulder joints. The learning algorithm is based on optimal criteria for obtaining the hierarchy of descriptions of movement trajectories. We show that this method finds complex synergism between optimal joint trajectories for a given set of data and angular velocities at the shoulder and elbow joints. Three other machine learning techniques (ML) are used for comparison with our method of hierarchical clustering of trajectories. These MLs are: (1) radial basis functions (RBF), (2) inductive learning (IL), and (3) adaptive-network-based fuzzy inference system (ANFIS). Better error characteristics were obtained using the method of hierarchical clustering in comparison with the other techniques. The advantage of the method of hierarchical clustering with respect to the other MLs is in integrating the spatial and temporal elements of reaching movements. Determination and analysis of spatio-temporal events of movement trajectories is a useful tool in designing control systems for functional electrical stimulation (FES) assisted manipulation.

Multicenter evaluation of electrical stimulation systems for walking

Objective: To test the long-term benefits of several noninvasive systems for functional electrical stimulation (FES) during walking. Design: Forty subjects (average years since injury, 5.4) were studied in four centers for an average time of 1 year. Gait parameters were tested for all subjects with and without FES. Thus, subjects served as their own controls, since the specific effect of using FES could be separated from improvements resulting from other factors (eg, training). Setting: Subjects used the devices in the community, but were tested in a university or hospital setting. Patients: Subjects with spinal cord injury ( n = 31) were compared to subjects with cerebral damage ( n = 9). Main Outcome Measures: Gait parameters (speed, cycle time, stride length). Acceptance was studied by means of a questionnaire. Results: Some initial improvement in walking speed (average increase of >20%) occurred, and continuing gains were seen (average total improvement, 45%). The largest relative gains were seen in the slowest walkers (speeds of <0.3m/sec). Acceptance of the FES systems was good and improved systems have been developed using feedback from the subjects. Conclusions: Based on the improvements in speed and the acceptance of these FES systems, a greatly increased role for FES in treating gait disorders is suggested.

Adaptive restriction rules provide functional and safe stimulation pattern for foot drop correction.

We report on our advances in sensory feedback data processing and control system design for functional electrical stimulation (FES) assisted correction of foot drop. We have applied 2 methods of signal purification on the bin integrated electroneurogram (i.e., optimized low pass filtering and wavelet denoising) before training adaptive logic networks (ALN). ALN generated stimulation control pulses, which correspond to the swing phase of the impaired leg when dorsal flexion of the foot is necessary to provide safe ground clearance. However, the obtained control signal contained sporadic stimulation spikes in the stance phase, which can collapse the subject, and infrequent broken stimulation pulses in the swing phase, which can result in unpredictable consequences. In this study, we have introduced adaptive restriction rules (ARR), which are initially used as previously reported and then dynamically adapted during the use of the system. Our results suggest that ARR provide a safer and more reliable stimulation pattern than fixed restriction rules.

Functional control of the hand in tetraplegics based on residual synergistic EMG activity.

A microprocessor controlled device (MeCFES) was used for the investigation of the possibility of restoring hand function in C5 tetraplegics with paralysis of the hand. To date, 3 tetraplegics have been testing the system. The myoelectric signals from wrist extension were recorded and used as control signals for functional electrical stimulation (FES) of thumb adduction/flexion. The results have shown that the device can improve the hand function of tetraplegics. In this part of the work, a hand function test was designed and used to assess the results.

Electrophysiologic evaluation of denervated muscles in incomplete paraplegia using macro electromyography

Objective: To evaluate denervated muscles in persons with incomplete paraplegia due to thoracolumbar spinal injury (TLSI) using macro electromyography in determining indications for functional electrical stimulation (FES). Design: A randomized clinical trial and a criterion standard. Setting: A department of orthopedic surgery in a university hospital. Patients and Other Participants: Eighteen patients with incomplete paraplegia, including 11 with TSLI, and 50 healthy adults. Intervention: Area and amplitude of macro motor unit potential (macro MUP) were measured at the tibialis anterior, the vastus lateralis, and the vastus medialis. The normal limits of macro MUP parameters were defined based on values from healthy subjects. Abnormal denervated muscles were detected by macro EMG and conventional EMG in paralytic patients. The correlation between macro MUP parameter values and muscle forces of the tibialis anterior and quadriceps femoris induced by electrical stimulation was analyzed. Main Outcome Measures: The number of abnormal muscles, parameter values, and muscle force induced by electrical stimulation. Results: Abnormal muscles were found only in the TLSI patients and 13 abnormal muscles were detected by macro EMG only. The abnormal muscles defined by macro EMG showed insufficient contraction induced by electrical stimulation. The increase of parameter value negatively correlated with the muscle force (tibialis anterior area r = −.797, amplitude r = −.866; quadriceps area r = −.866, amplitude r = −.893; p < .001). Conclusions: These results suggest that macro EMG is useful in detecting denervated muscles, in determining indications for FES, and in predicting FES effects before implantation of electrodes.

機能的電気刺激 (FES) システムの制御命令としての舌動作の検討

機能的電気刺激 (FES) システムの制御命令としての舌動作の検討

The influence of orthosis stiffness on paraplegic ambulation and its implications for functional electrical stimulation (FES) walking systems

This study examines the evidence which supports the importance of maintaining relative abduction for effective reciprocal walking in high level paraplegic patients. In comparisons of orthoses, where this can only be achieved mechanically, those with higher lateral rigidity consistently showed greater levels of walking efficiency. The influence on hybrid systems of functional electrical stimulation (FES) of the gluteal muscles, where the primary function is to maintain abduction, also showed reductions in overall energy cost, reductions in upper limb effort, or both. Examination of the effect of increasing lateral rigidity of a purely mechanical orthosis by 10% showed that significant energy cost reductions were achieved (30% reduction in Physiological Cost Index) for patients with thoracic lesions experienced in reciprocal walking. A review of FES research suggested that for the modern healthcare sector the cost effectiveness of purely mechanical systems make them an attractive means of routinely providing the functional and therapeutic benefits of walking for high level paraplegic patients. In the prevailing climate of strict budgetry control a case is made for concentrating more research resources on improving still further walking efficiency, and resolving the outstanding problems of functionality and cosmesis in such systems for reciprocal walking.

機能的電気刺激 (FES) システムの制御命令としての耳介動作の検討

機能的電気刺激 (FES) システムの制御命令としての耳介動作の検討

ＦＥＳ用経皮的電力伝送コイルの特性改善に関する考察

Inductively coupled coils are thought to transfer electrical energy for functional electrical stimulation (FES). This paper describes methods for the design of spiral transmitting coils with amorphous magnetic fibers for FES loads. Generally. transmitting coils - for lighter loads need more winding turns. After determination of the size of coil, which corresponds to the power to be transmitted, the number of coil turns can be increased by using thinner conducting wires or by winding the wires in multi-lavers. In an investigation of the merits and demerits of each method, we were able to transmit electrical energy non-contactingly to loads of between 100 Ω and 250 Ω with a high efficiency of nearly 90%.

A review of the functional electrical stimulation equipment market.

The market for functional electrical stimulation (FES) equipment for use in rehabilitation is growing as increasingly sophisticated products enter the market each year. Factors that impact the availability of FES equipment include technological limitations, government regulation, reimbursement status, and clinician training. New products have become available in the last decade with many innovative applications available under investigational status. The current availability of FES equipment for selected applications such as therapeutic muscle stimulation, cardiovascular exercise, restoration of function in the lower and upper extremities, respiratory assist, restoration of bladder function, electroejaculation, and scoliosis correction is reviewed. A review of FES equipment for nonneuromuscular applications such as control of epilepsy, cochlear implants, electrotactile stimulation, and systems to enhance wound healing and bone growth is also included. Key manufacturers are identified.

Long-term results of nervous tissue alterations caused by epineurial electrode application: an experimental study in rat sciatic nerve.

In order to evaluate the long-term effects of epineurial electrode application for functional electrical stimulation (FES) the left sciatic nerve of seven rats was exposed. Four ring-shaped stainless steel wire electrodes were sutured to the epineurium of each nerve in the same manner as performed clinically for carrousel stimulation in man. The nerves were reexposed 1 year after implantation and the stimulation threshold to obtain a tetanic contraction in the lower limb was determined for each electrode. Afterwards the animals were sacrificed. The electrodes were excised and cross sections of the sciatic nerve directly at site of the electrodes, 2-mm proximal and 2-mm distal to them were harvested for histologic and planimetric assessment of nerve lesions. The area of damaged neural tissue was expressed as a percentage of the total cross-sectional area within the perineural sheath. The sciatic nerves of the right side served as controls. The values for the stimulation thresholds ranged between 0.1 and 1.0 mA (mean 0.43 mA). By morphometric examination five of seven nerves were seen altered, the altered areas captured between 1% and 4.8% of the total cross-sectional area of the nerves within the perineural sheath. Besides two specimens, all altered nerve segments exhibited distinct signs of nerve fiber regeneration. The clinical implications of the results for long-term electrical stimulation, such as phrenic pacing, are discussed.

Technology Transfer of a System for Medically Prescribed F.E.S. Walking Exercise

Commercially available electronic muscle stimulators (EMS) are used for functional electrical stimulation (FES) and are interfaced with the reciprocating gait orthoses (RGO). The new system that results is described with both individual electrodes and an electrode garment. Various advantages of the system include: (a) commercially available subsystems from various manufacturers, and (b) subsystems that may be individually prescribed by a physician. The system itself currently employs two EMS units worn on a belt, controlled by remote switches and interfacing to electrodes placed over hamstring and gluteal muscle groups of each leg. Two EMS units (for stimulation of the hip extensors) function primarily for ambulation. The system has been evaluated on four spinal-cord-injured individuals (two paraplegic and two quadriplegic) who are five or more years post-injury. Each EMS unit is powered by a nine-volt alkaline transistor battery. All subjects utilized individual carbon-rubber electrodes, and one subject also utilized a Transcutaneous Transducer Garment (TTG). It is emphasized that successful EMS-RGO walking exercise is one of three modalities in a program of active physical therapy. The paper gives an overview of the operational, design and material considerations that are important for technology transfer.

Creation of Neuromuscular Stimulation Data for Functional Electrical Stimulation (FES)—Control of Paralyzed Elbow Movements—

Creation of Neuromuscular Stimulation Data for Functional Electrical Stimulation (FES)—Control of Paralyzed Elbow Movements—

Posture switching for prolonging functional electrical stimulation standing in paraplegic patients.

The presently employed posture for Functional Electrical Stimulation (FES) assisted standing in spinal cord injury (SCI) patients utilises the active locking of knee joints by tetanically stimulating the quadriceps muscle. The hip joints are in hyperextension and the ankle joints remain free. The upper limbs are used for balancing. This posture requires minimal corrective forces exerted by the hands, the weight is transferred across the legs, while very limited forward-backward sway is permitted. Knee jack-knifing may occur in the instance when the gravity knee bending moment exceeds the moment generated by the quadriceps muscle. Because of these effects and fatiguing of the M. quadriceps the standing time is short, lasting from several minutes up to an hour, depending on the condition of the patient's muscles. Cyclical FES with a duty cycle of 10-20 seconds (on/off) fatigues muscle considerably less. The use of different postures for standing requiring activation of different muscles permits the application of cyclical FES. The cyclic FES results in prolonging standing times by a factor of two to five. Utilising this improvement some patients can stand for up to five hours at a time. This functional achievement is comparable to the standing time of a normal man. The incorporation of the principle of posture switching also prolongs standing in patients with weak muscles, because of the possibility of cyclical coactivation of different synergistic muscle assemblies. It is shown that posture switching can be carried out automatically and that patients adapt quickly to it. In addition using co-contraction of two or three muscles with posture switching does further expand the range of suitable patients and improves standing with an increased permissible range of body sway. Also, the FES antigravity action obtained raises hopes for substantially improving FES induced reciprocal gait.