Clinical experience of functional electrical stimulation in complete paraplegia

Contralaterally controlled functional electrical stimulation immediately improves hand function

Murata S, Koike Y, Kasukawa Y, Saito K, Okada K, Kudo D, Shimada Y, Miyakoshi N. Contralaterally controlled functional electrical stimulation immediately improves hand function. Jpn J Compr Rehabil Sci 2022; 13: 26-30.

Objective

The purpose of this study was to investigate the immediate effects of contralaterally controlled functional electrical stimulation (CCFES) on upper limb function in stroke patients.

Methods

CCFES and mirror therapy (MT) exercises were conducted for 13 stroke patients at least 4 weeks post-onset. A sufficient interval of at least 24 hours was left between the two types of rehabilitation exercises. Before treatment and immediately after each training session, grip strength, Fugl-Meyer Assessment for Upper Extremity (FMA-UE) score and FMA-UE subscores for the shoulder/elbow/forearm, wrist, hand, and coordination were evaluated.

Results

Grip strength, FMA-UE and FMA-UE shoulder/elbow/forearm, wrist, and coordination did not differ significantly after CCFES and MT compared to before therapy. FMA-UE hand did not change significantly after MT compared to before therapy, but it improved significantly after CCFES (p = 0.013).

Conclusion

CCFES for the upper extremities immediately improves hand function and may be effective in maintaining and improving patients' motivation for rehabilitation treatment.

Advanced Equipment Development and Clinical Application in Neurorehabilitation for Spinal Cord Injury: Historical Perspectives and Future Directions

Partial to complete paralysis following spinal cord injury (SCI) causes deterioration in health and has severe effects on the ability to perform activities of daily living. Following the discovery of neural plasticity, neurorehabilitation therapies have emerged that aim to reconstruct the motor circuit of the damaged spinal cord. Functional electrical stimulation (FES) has been incorporated into devices that reconstruct purposeful motions in the upper and lower limbs, the most recent of which do not require percutaneous electrode placement surgery and thus enable early rehabilitation after injury. FES-based devices have shown promising results for improving upper limb movement, including gripping and finger function, and for lower limb function such as the ability to stand and walk. FES has also been employed in hybrid cycling and rowing to increase total body fitness. Training using rehabilitation robots is advantageous in terms of consistency of quality and quantity of movements and is particularly applicable to walking training. Initiation of motor reconstruction at the early stage following SCI is likely to advance rapidly in the future, with the combined use of technologies such as regenerative medicine, brain machine interfaces, and rehabilitation robots with FES showing great promise.

Development of a Gait Rehabilitation Robot Using an Exoskeleton and Functional Electrical Stimulation: Validation in a Pseudo-paraplegic Model

Objective:

We have developed a robot for gait rehabilitation of paraplegics for use in combination with functional electrical stimulation (FES). The purpose of this study was to verify whether the robot-derived torque can be reduced by using FES in a healthy-person pseudo-paraplegic model.

Methods:

Nine healthy participants (22–36 years old) participated in this study. The robot exoskeleton was designed based on the hip–knee–ankle–foot orthosis for paraplegia. Participants walked on a treadmill using a rehabilitation lift to support their weight. The bilateral quadriceps femoris and hamstrings were stimulated using FES. The participants walked both with and without FES, and two walking speeds, 0.8 and 1.2 km/h, were used. Participants walked for 1 min in each of the four conditions: (a) 0.8 km/h without FES, (b) 0.8 km/h with FES, (c) 1.2 km/h without FES, and (d) 1.2 km/h with FES. The required robot torques in these conditions were compared for each hip and knee joint. The maximum torque was compared using one-way analysis of variance to determine whether there was a difference in the amount of assist torque for each gait cycle.

Results:

Walking with the exoskeleton robot in combination with FES significantly reduced the torque in hip and knee joints, except for the right hip during extension.

Conclusions:

In the healthy-participant pseudo-paraplegic model, walking with FES showed a reduction in the robot-derived torque at both the hip and knee joints. Our rehabilitation robot combined with FES has the potential to assist paraplegics with various degrees of muscle weakness and thereby provide effective rehabilitation.

Effect of Joint Friction Compensation on a "Muscle-First" Motor-Assisted Hybrid Neuroprosthesis

This study assessed the metabolic energy consumption of walking with the external components of a “Muscle-First” Motor Assisted Hybrid Neuroprosthesis (MAHNP), which combines implanted neuromuscular stimulation with a motorized exoskeleton. The “Muscle-First” approach prioritizes generating motion with the wearer's own muscles via electrical stimulation with the actuators assisting on an as-needed basis. The motorized exoskeleton contributes passive resistance torques at both the hip and knee joints of 6Nm and constrains motions to the sagittal plane. For the muscle contractions elicited by neural stimulation to be most effective, the motorized joints need to move freely when not actively assisting the desired motion. This study isolated the effect of the passive resistance or “friction” added at the joints by the assistive motors and transmissions on the metabolic energy consumption of walking in the device. Oxygen consumption was measured on six able-bodied subjects performing 6 min walk tests at three different speeds (0.4, 0.8, and 1.2 m/s) under two different conditions: one with the motors producing no torque to compensate for friction, and the other having the motors injecting power to overcome passive friction based on a feedforward friction model. Average oxygen consumption in the uncompensated condition across all speeds, measured in Metabolic Equivalent of Task (METs), was statistically different than the friction compensated condition. There was an average decrease of 8.8% for METs and 1.9% for heart rate across all speeds. While oxygen consumption was reduced when the brace performed friction compensation, other factors may have a greater contribution to the metabolic energy consumption when using the device. Future studies will assess the effects of gravity compensation on the muscular effort required to lift the weight of the distal segments of the exoskeleton as well as the sagittal plane constraint on walking motions in individuals with spinal cord injuries (SCI).

Development of a Rehabilitation Robot Combined with Functional Electrical Stimulation Controlled by Non-disabled Lower Extremity in Hemiplegic Gait

Objective

We developed a rehabilitation robot to assist hemiplegics with gait exercises. The robot was combined with functional electrical stimulation (FES) of the affected side and was controlled by a real-time-feedback system that attempted to replicate the lower extremity movements of the non-affected limb on the affected side. We measured the reproducibility of the non-affected limb movements on the affected side using FES in non-disabled individuals and evaluated the smoothness of the resulting motion.

Method

Ten healthy men participated in this study. The left side was defined as the non-affected side. The measured hip and knee joint angles of the non-affected side were reproduced on the pseudo-paralytic side using the robot's motors. The right quadriceps was stimulated with FES. Joint angles were measured with a motion capture system. We assessed the reproducibility of the amplitude from the maximum angle of flexion to extension during the walking cycle. The smoothness of the motion was evaluated using the angular jerk cost (AJC).

Results

The amplitude reproduction (%) was 87.9 ± 6.2 (mean ± standard deviation) and 71.5 ± 10.7 for the hip and knee joints, respectively. The walking cycle reproduction rate was 99.9 ± 0.1 and 99.8 ± 0.2 for the hip and knee joints, respectively. There were no statistically significant differences between results with FES versus those without FES. The AJC of the robot side was significantly smaller than that of the non-affected side.

Conclusions

A master-slave gait rehabilitation system has not previously been attempted in hemiplegic patients. Our rehabilitation robot showed high reproducibility of motion on the affected side.

A randomized trial of functional electrical stimulation for walking in incomplete spinal cord injury: effects on body composition

OBJECTIVE

To evaluate the effects of functional electrical stimulation (FES)-assisted walking on body composition, compared to a non-FES exercise program in individuals with a spinal cord injury (SCI).

DESIGN

Parallel-group randomized controlled trial.

METHODS

Individuals with chronic (≥ 18 months) incomplete SCI (level C2 to T12, AIS C or D) were recruited and randomized to FES-assisted walking (intervention), or aerobic and resistance training (control) sessions thrice-weekly for 16 weeks. Whole body and leg lean mass and whole body fat mass, measured with dual-energy X-ray absorptiometry, and lower-limb muscle cross-sectional area (CSA) and fat CSA, measured with peripheral computed tomography were assessed at baseline, 4 months, and 12 months. Intention-to-treat analyses using repeated measures general linear models were used to assess between-group differences.

RESULTS

Thirty-four individuals were randomized (17 per group); 27 remained at 12 months. There were no significant main effects of FES-assisted walking on body composition variables in intention-to-treat analyses with group means. There was a significant group-by-time interaction for muscle area from baseline to 12 months (P = 0.04). Intention-to-treat analysis of muscle area change scores between baseline and 12 months revealed a significant difference between groups (mean (SD) muscle area change score 212 (517) mm(s) for FES, -136 (268) mm(s) for control, P = 0.026). There were 13 side effects or adverse events deemed related to study participation (7 intervention, 5 control); most were resolved with modifications to the protocol. One fainting episode resulted in a hospital visit and study withdrawal.

CONCLUSIONS

Thrice-weekly FES-assisted walking exercise over 4 months did not result in a change in body composition in individuals with chronic, motor incomplete C2 to T12 SCI (AIS classification C and D). However, longer-term follow-up revealed that it might maintain muscle area.

Development of FES-rowing machine

As per present social needs, assisting machines are very much needed for persons of advanced age. We analyzed and developed a fitness apparatus suitable for meeting the requirement of elderly people. The proposed apparatus consists of a rowing machine and Functional Electrical Stimulation (FES), that can be used to exercise every muscle of a person of advanced age. The rowing mechanism was actually developed to train rowers and can train the legs and upper body parts most effectively. Move over FES can assist the exercise of the legs by using surface electrical stimulation. An experiment was conducted and the results prove that the developed apparatus can train the muscles of the person of advanced age effectively and can compensate exercise shortage.

Clinical application of acceleration sensor to detect the swing phase of stroke gait in functional electrical stimulation

Functional electrical stimulation (FES) can improve the gait of stroke patients by stimulating the peroneal nerve in the swing phase of the affected leg, causing dorsiflexion of the foot that allows the toes to clear the ground. A sensor can trigger the electrical stimulation automatically during the stroke gait. We previously used a heel sensor system, which detects the contact pressure of the heel, in FES to correct foot drop gait. However, the heel sensor has disadvantages in cosmetics and durability. Therefore, we have replaced the heel sensor with an acceleration sensor that can detect the swing phase based on the acceleration speed of the affected leg, using a machine learning technique (Neural Network). We have used a signal for heel contact in a gait using the heel sensor before training with the Neural Network. The accuracy of the Neural Network detector was compared with a swing phase detector based on the heel sensor. The Neural Network detector was able to detect similarly the swing phase in the heel sensor. The largest difference in timing of the swing phase was less than 60 milliseconds in normal subjects and 80 milliseconds in stroke patients. We were able to correct foot drop gait using FES with an acceleration sensor and Neural Network detector. The present results indicate that an acceleration sensor positioned on the thigh, which is cosmetically preferable to systems in which the sensor is farther from the entry point of the electrodes, is useful for correction of stroke gait using FES.

Hybrid functional electrical stimulation with medial linkage knee-ankle-foot orthoses in complete paraplegics

We have previously restored ambulation in paraplegics by performing hybrid functional electrical stimulation (FES) with medial linkage knee-ankle-foot orthosis (MLKAFO). The most common MLKAFO (hinge-type MLKAFO) has the hypothetical axis that is lower than the physiological hip joint position, resulting in slow velocity and short step length. A new MLKAFO (sliding-type MLKAFO), which uses sliding medial linkages, has been developed to correct the axial discrepancy of the hinge-type MLKAFO that causes limited hip joint excursion. There have been reports of instability associated with sliding medial linkages, but the mechanism of this instability is unclear. The purpose of the present study was to evaluate the effects of FES with MLKAFOs on ambulation in paraplegics. Two complete paraplegic patients (levels T8 and T12, respectively) participated in this study. Kinematics data during ambulation were obtained using a motion analysis system. We measured gait velocity and hip progression during the standing phase. The sliding-type MLKAFO produced faster gait velocity than did the hinge-type MLKAFO, but it caused pelvis instability without FES. Pelvis instability was controlled by hybrid FES using the sliding-type MLKAFO. With hybrid FES, the sliding-type MLKAFO provides better gait performance than the hinge-type MLKAFO, but the hinge-type MLKAFO provides greater pelvis stability during walking. Moreover, FES provides sufficient propulsion to allow the complete paraplegics to walk.

Effects of therapeutic magnetic stimulation on acute muscle atrophy in rats after hindlimb suspension

In most subjects with spinal cord injury, the spinal neurons below the level of injury are spared. Therefore, it is conceivable that the skeletal muscles innervated by these spinal nerves can be activated by applying therapeutic magnetic stimulation along the dorsal spine. The purpose of this study was to evaluate the ability of magnetic stimulation to prevent acute muscle atrophy in rats after hindlimb suspension. Forty adult male Wistar rats were randomly assigned to stimulated and non-stimulated (control) groups. Their hindlimbs were unweighted using a suspension method, causing muscle atrophy. In the stimulation group, magnetic stimulation (20 Hz, 60 min per day) was applied to the sciatic nerve for 10 days. After the stimulation period, the tibialis anterior (TA) and extensor digitorum longus (EDL) were surgically removed and histologically measured. The lesser diameters of type 1, 2A, and 2B muscle fibers were significantly greater in the stimulated group than in the non-stimulated group for both the TA and EDL (p < 0.05). The mean difference in lesser fiber diameter was 20% (range, 14%-27%). These results suggest that therapeutic magnetic stimulation is an effective method of preventing muscle atrophy.

Reduction of muscle fatigue by catchlike-inducing intermittent electrical stimulation in rat skeletal muscle

Catchlike property is the force enhancement produced when a brief, high-frequency burst of pulses is added to a constant low-frequency stimulation. In functional electrical stimulation, constant low-frequency stimulation of approximately 20 Hz has primarily been used to reduce muscle fatigue. The purpose of this study was to investigate the effects of catchlike-inducing intermittent stimulation on muscle fatigue in relation to continuous intermittent low-frequency stimulation. Twenty-two adult male Wistar ST rats were randomly assigned into the constant frequency stimulation (CFS) group or the catchlike-inducing stimulation (CIS) group. In the CFS group, constant low-frequency stimulation of 20 Hz was applied intermittently (4 seconds "ON"/15 seconds "OFF"). In the CIS group, a single electrical burst of 100 Hz was applied at the start of the every 4-second period of stimulation. The muscle fatigue test lasted for 16 min and isometric muscle force, muscle fatigue, and muscular workload were evaluated. CIS significantly increased the maximum muscular force (under fatigued condition) and workload, and significantly decreased muscle fatigue (p < 0.05). The results of this study suggest that catchlike-inducing intermittent electrical stimulation is useful in the clinical administration of functional electrical stimulation.

Bone loss and muscle atrophy in spinal cord injury: epidemiology, fracture prediction, and rehabilitation strategies

Individuals with spinal cord injury (SCI) often experience bone loss and muscle atrophy. Muscle atrophy can result in reduced metabolic rate and increase the risk of metabolic disorders. Sublesional osteoporosis predisposes individuals with SCI to an increased risk of low-trauma fracture. Fractures in people with SCI have been reported during transfers from bed to chair, and while being turned in bed. The bone loss and muscle atrophy that occur after SCI are substantial and may be influenced by factors such as completeness of injury or time postinjury. A number of interventions, including standing, electrically stimulated cycling or resistance training, and walking exercises have been explored with the aim of reducing bone loss and/or increasing bone mass and muscle mass in individuals with SCI. Exercise with electrical stimulation appears to increase muscle mass and/or prevent atrophy, but studies investigating its effect on bone are conflicting. Several methodological limitations in exercise studies with individuals with SCI to date limit our ability to confirm the utility of exercise for improving skeletal status. The impact of standing or walking exercises on muscle and bone has not been well established. Future research should carefully consider the study design, skeletal measurement sites, and the measurement techniques used in order to facilitate sound conclusions.

Modular transcutaneous functional electrical stimulation system

A new multipurpose programmable transcutaneous electric stimulator, Compex Motion, was developed to allow users to design various custom-made neuroprostheses, neurological assessment devices, muscle exercise systems, and experimental setups for physiological studies. Compex Motion can generate any arbitrary stimulation sequence, which can be controlled or regulated in real-time using any external sensor or laboratory equipment. Compex Motion originated from the existing Compex 2 electric stimulator, manufactured by a Swiss based company, Compex SA. The Compex Motion stimulator represents a further evolution and expansion of the ETHZ-ParaCare functional electrical stimulation system. This stimulator provides all the advanced functional electrical stimulation (FES) application and control features and can be easily incorporated into any standard rehabilitation program. Compex Motion has successfully been applied as a neuroprosthesis for walking, reaching and grasping in more than 100 stroke and spinal cord injured patients. This system has also been used to strengthen muscles and to investigate muscle properties in able-bodied subjects. Compex Motion is a multipurpose FES system specially designed to promote sharing and exchanging of stimulation protocols, sensors, and user interfaces. To the best of our knowledge an FES system that has similar capabilities does not exist yet.

Grasping power by means of functional electrical stimulation in a case of C6 complete tetraplegia

Grasping power (GP) by means of functional electrical stimulation (FES) was measured in a case of C6 complete tetraplegia. This was compared with GP by means of the dynamic tenodesis effect, the flexor hinge splint and the GP of normal female. Palmar grasp strength by means of FES was approximately 16% of the control group and 2.4 times greater than the flexor hinge splint. Lateral grasp strength by FES was approximately 13% of the control group. Our results suggest that FES is more effective than the flexor hinge splint in increasing the GP of tetraplegic patients, and that a stronger and stable GP, which is not affected by wrist position, makes FES practical for improving activities of daily living (ADL).

Closed-loop control using a stretch sensor for restoration of standing with functional electrical stimulation in complete paraplegia

A closed-loop control system for standing with functional electrical stimulation (FES) using percutaneous intramuscular electrodes in complete paraplegia is described. The system consisted of ultrafine percutaneous intramuscular electrodes, a 32-channel stimulator and a stretch sensor with active current control to detect knee buckling. The closed-loop control system was applied in a T8 completely paraplegic patient. Compared to the stretch sensor with a wide use flexible goniometer for direct current control during standing, the stretch sensor was superior to the flexible goniometer in both ease of use and response. The average time delay from the start of knee buckling until the sensor turned on was 0.56+/-0.19 seconds (Mean+/-S.D.) in the goniometer and 0.21+/-0.06 seconds in the stretch sensor. The average time delay from the start of knee buckling until the recovery from knee buckling was 1.01+/-0.05 seconds in the goniometer and 0.78+/-0.06 seconds in the stretch sensor. The continuous standing ability of the patient increased from 12 minutes with open-loop stimulation to 30 minutes with the closed-loop control. No complications such as falling occurred during clinical use. This system prevented falling due to knee buckling during standing and prolonged upright activities in complete paraplegics.

Hybrid functional electrical stimulation for energy-efficient restoration of standing-up motion

OBJECTIVE

To find the most energy-efficient standing-up motion for quadriceps and to restore that motion in a person with complete paraplegia by using hybrid functional electrical stimulation.

DESIGN

Nonrandomized control trial.

SETTING

A referral center and institutional practice providing outpatient care.

PARTICIPANTS

Twenty-nine volunteer samples were used to collect normal data. One patient with complete paraplegia received treatment for the restoration of standing-up motion.

MAIN OUTCOME MEASUREMENTS

Joint angles and ground reaction forces were investigated during the standing-up motion with arms crossed in front of the chest with an ankle-foot orthosis set at various angles. The electromyogram (EMG) was performed during the standing-up motion with and without the orthosis. The energy costs of quadriceps during the standing-up motion were calculated using a mathematical model. Standing-up motion in a person with complete paraplegia was restored and then analyzed by measuring the vertical ground reaction force and the hip and knee angles.

RESULTS

Quadriceps energy cost was lowest (p < .05) in subjects wearing the ankle-foot orthosis set at neutral with a flat sole line. In the integrated EMG the peak value of rectus femoris contraction was larger with the orthosis than without it (p < .05). A patient with complete paraplegia was able to stand up smoothly from a wheelchair based on stimulation patterns obtained from healthy subjects.

CONCLUSIONS

Energy-efficient standing-up motion in a patient with complete paraplegia was restored when the patient used an ankle-foot orthosis set at neutral with a flat sole line.

Muscle fatigue from intermittent stimulation with low and high frequency electrical pulses

OBJECTIVE

To evaluate muscle fatigue resulting from intermittent low frequency and high frequency stimulation for the application of closed-loop control in functional electrical stimulation (FES).

DESIGN

Nonrandomized trial.

SETTING

General community, a referral center, institutional practice, and ambulatory care.

PATIENTS

Twenty healthy nondisabled men volunteered for the normal muscle group. Four paraplegic men with implanted percutaneous intramuscular electrodes for FES volunteered for the paralyzed muscle group.

INTERVENTION

The stimulation frequency was set at low (20 Hz) or high (100 Hz). Stimulation was administered in 4-second bursts at the start of 60-second, 120-second, and 240-second periods (duty cycles of 1/15, 1/30, and 1/60, respectively).

MAIN OUTCOME MEASUREMENTS

Knee extensor torques were measured during intermittent electrical stimulation. A strength decrement index (SDI) was used to assess muscle fatigue. Actual knee extensor torques in the paraplegic men were also measured with an isokinetic dynamometer.

RESULTS

Muscle fatigue was significantly greater at 20 Hz than at 100 Hz for both the nondisabled and the paraplegic subjects (p < .0001). Muscle fatigue at the 1/15 cycle was significantly reduced (p < .01).

CONCLUSIONS

Muscle fatigue was greater at the lower frequency (20 Hz) than at the higher frequency (100 Hz) during intermittent electrical stimulation, suggesting that intermittent high frequency stimulation may be valuable in the development of closed-loop control strategies for FES.

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.