Functional electrical stimulation can be used to treat poststroke gait deficiencies. Stimulation of the ankle dorsiflexors alone is not enough to treat other gait problems.
Stroke survivors can still experience gait impairments even after their rehabilitation. Walking ability can be a major concern for stroke victims. Up to 20% of them have foot drop. This is due to partial or complete paralysis of the dorsiflexor muscles. 2
Trisha M.Kesar (PT) and PhD explained that it is necessary to develop interventions to address multiple gait issues at different joints. This includes the important stance phase and swing phase poststroke gait deficiencies at both the knee and hip.
Kesar's research group is currently working on a multidisciplinary National Institutes of Health-funded project. The goal of the project is to create new intervention strategies that combine FES with fast treadmill training to maximize poststroke walking function.
Supplementing dorsiflexor-essor stimulation with plantar-flexor stimulation has many benefits. Additionally, this is due to decreased swing phase kneeflexion when walking with FES 2. Plantar stimulation could possibly correct this.
Kesar and his colleagues noticed that this phenomenon was first discovered in Physical Therapy HTML2. This study used two types or frequency trains of stimulation to examine swing-phase knee and ankle motions during dorsiflexor EES.
Researchers worked alongside 13 hemiparetic individuals (nine men, four women, aged 46-72), and who were able to walk at least five minutes at a time. They also had to have had at least six months of stroke recovery and had enough passive dorsiflexion to move the paretic foot joint while the knee was bent.
Participants were stimulated with electrodes attached to their dorsiflexor muscles. Participants were given a 30-Hz pulse of 300 ms duration and a length of 300 microseconds. This pulse was repeated until the participants achieved a neutral ankle position (0deg), and at least 5deg of plantar flexion for patients with range of motion impairments. 2
To control the timing and gait, two footswitches were placed bilaterally under each shoe's soles. To control the timing of gait, one foot was placed under the forefoot and the other under the hindfoot. This is the period between the moment the forefoot footswitch touched the ground and the moment the hindfoot touches the ground.
The Investigators used a constant frequency train at 30-hz to stimulate FES with CFTs. Other than the 200-Hz three-pulse burst that was used for initiating the VFTs, the stimulation parameters with CFTs and VFTs were identical.
Surprising results
Investigators compared three walking conditions: walking without FES, walking with DorsiflexorFES with CFTs, and walking with DorsiflexorFES with VFTs. All three conditions required 20-40 seconds of walking at self-selected speeds
VFT FES and CFT both increased ankle dorsiflexion angles when walking, as compared with no FES. This led to greater ankle swing dorsiflexion.
Investigators were surprised to find that dorsiflexor EES decreased ankle plantarflexion at the toe and swing-phase kneeflexion. VFTs were better than CFTs, and this suggests that dorsiflexor may worsen the type of gait impairment experienced by hemiparetic poststroke patients. They are more likely than others to have swing phase kneeflexion deficits in the paretic legs.
According the authors, lower angles of plantarflexion may result in lower push off forces at your ankles when you transition from swinging to standing.
Kesar and his colleagues believe that timing is crucial for FES's effectiveness. FES activated the forefoot footswitch when the forefoot touched the ground. This happened just before the toe-off.
The authors suggest that stimulating the plantar muscles might reduce the problem. This would increase force generation during pushoff.
Kesar said that stimulation of the dorsiflexors as well as the plantar can lead to improvements in foot drop, and knee flexion. This can be in addition to improving walking speed, push-off forces, and walking speed.
FES Combined
Kesar, coworkers and others tested this hypothesis in a 2009 Stroke study.
The investigators used an FES system that provided VFT stimulation during gait.
Kesar stated that timing is critical for electrical stimulation.
"During normal walking, dorsiflexor and plantar flexor muscles are active during various parts of the gait cycle. "The stimulation method in our study provides stimulation for the dorsiflexors when they are performing foot swings, as well as the plantarflexors, when transitioning from stance to swing (i.e. during push off).
The ankle plantar angle at paretictoeoff for walking with FES was -9.2+-1.22deg. There were no differences in the ankle angle (-8.3+1.3deg; P=0.41).
Dorsiflexor EES significantly decreased peak swing-phase kneeflexion angles (40.8+-42.2deg) compared to combined FES (P=0.81). There was no difference in peak swing-phase kneeflexion angles between combined FES (44.1-24.2deg) and no FES (44.3-24.6deg), P=0.81.
Comparing walking with FES and walking without FES, peak anterior ground reaction forces of the paretic legs increased 18% when walking with FES to both plantar flexors and dorsiflexors.
Combination FES resulted in significantly greater peak swing-phase ankle dorsiflexion than no FES, but less than dorsiflexors alone FES. This suggests that the intensity of dorsiflexor stimulation might need to increase when dorsiflexors are activated simultaneously with plantar flexors. 3
Kesar said that the combination approach has been promising. Kesar stated that the combination approach is promising so far.
Timing of refinement
Researchers at MultiCare Good Samaritan Rehabilitation Center, Puyallup (WA), are currently focusing on the use combined dorsiflexion/plantar flexor FES to train the brain for better walking.
Figure 1. Figure 1. (Provided By David Embrey PhD, PT.
A recent cross-over study that involved 28 patients with chronic hemiplegia, ranging in age between 4.9+ and 3.8 years poststroke, examined the effects combined FES on walking. This was done with a 6-minute walk test (EFAP), Emory Functional Ambulatory Profile (EFAP), and the Stroke Impact Scale (8 span>).
Participants were randomly assigned one of two interventions that lasted three months each. Participants were randomly assigned to one of two interventions, each lasting three months. The FES system activated while participants walked. It was used for an hour every day, six days a week. They walked at a pace that was comfortable for them with sessions lasting no more than fifteen minutes. B-A contained 13.
The customized FES system was designed to stimulate the paretic leg. It had a forefoot switch and a heel switch. This system was then placed on the foot of the nonparetic. The system was worn daily by the participants, which gave them the freedom to use it in their own environment.
David G. Embrey PhD. PT was the lead author. He stated that no pre- or postintervention assessment was done while participants were wearing stimulators.
Embrey is the Children's Therapy Unit's research program coordinator at the Good Samaritan Movement Laboratory. Embrey is the research program coordinator for the Children's Therapy Unit at the Good Samaritan Movement Laboratory.
A's intervention had statistically significant improvements in two primary outcomes measures at the study midpoint compared with intervention B. At three months, SIS for A showed statistically significant improvements (P=0.03; mean SD scores 23.5+-26.6 compared with intervention B; average +– SD scores 3.6+–28).
Three month later, statistical significance was achieved when the time taken to complete the EFAPs for the A and B interventions was measured (P=0.08. Mean 23.7+-23.9 secs for the A intervention vs 9.8+-8.9 seconds in the B intervention).
The overall gains in the 6MWT over six months were 57.1+-35.7m, 32.3+-20.5m, and 21.6+-11.4 second respectively for A/B and A/A groups. SIS scores increased by 45.4+-47.0 in the A/B and 33.4+-30.7 respectively (P=0.01) following the study.
Crossover design was used to study carryover effects in A and B, who stopped using FES after three months but continued walking for an hour each day for six consecutive days.
Embrey said that participants not only maintained their gains but also their progress.
During B intervention, A/B group walked 9.3+-36.4m faster on the 6MWT. This reduced EFAP time by another 7.2+-5.3 seconds and earned 24.8+48.7 SIS points.
Embrey said that stimulation received within the first three months was more effective than walking intervention. They also reaffirmed what they had learned in the first three months.
Embrey stated the stimulation timing should be set in a manner that promotes normal gait patterns.
He said that although most studies of dorsiflexor FESs to treat drop foot used stimulation during the swing phase, dorsiflexors also fire during the loading phase. This is also the case for many other researchers who used plantar stimulation.
Kesar was among the "other researchers", who supported the team's decision.
Figure 2. Figure 2. (Provided By David Embrey PhD, PT.
"Our FES stimulates dorsiflexors during swing phase to correct foot falls. She explained that the foot displays a more controlled plantarflexion, and doesn't slap" during the loading response.
The timing of plantar contraction controls plantar flexion. Plantar flexion is controlled by the timing of plantar contraction. This contrasts with the roles they play in the mid-stance or early phases.
Rehabilitation in the real world
Physical therapists have the ability to treat patients with a wide range of gait, stance, and control.
Lichy explained that FES can be used in many ways at the clinic. Lichy also stated that FES is used in many different ways at the clinic.
She stated that although the current FES research is logical and worthwhile, it may not be appropriate for all patients.
Lichy said that the most common complaint patients have about their feet is that they drag. Patients with foot drag don't need more pushing forward. They can step, hesitate and step, then hesitate again. It is important to strengthen their ankle muscles.
She stated that bracing with orthoses can improve poststroke gait performance.
Braces can provide support for patients who need it, but bracing may be necessary for those who require more than FES.
In her clinic, Lichy uses only FES with dorsiflexor. Some of her patients have participated in studies that used combined FES systems.
"Some people respond well, while others don’t like it or find it ineffective.
Refers
1. Burridge JS, Taylor PN and Hagan SA. An randomized controlled trial was performed to evaluate the effects of common peoneal stimulation (CPS), on walking speed in chronic hemiplegics.
2. Kesar TM. Perumal R. Jancosko A. After a stroke, new patterns of functional electric stimulation can be used to immediately alter dorsiflexor muscle function.
3. Kesar TM, Perumal R, Reisman DS, et al. Effects of functional electrical stimulation on ankle dorsiflexor and plantarflexor muscles after stroke: Stroke 2009;40(12):3821-3827
4. Binder Macleod, S. and Kesar T. The catchlike characteristic of skeletal muscles: Recent discoveries and clinical implications. Muscle Nerve 2005.31(6):681-693.
5. Lee SC, Becker CN and Binder-Macleod SA. Burst modulation: Catchlike-inducing train activation in human muscle during isotonic contractions. J Appl Physiol 1999,87:1758-1767.
6. Lee SC, Binder-Macleod SA. The effects of activation frequency on the dynamic performance of human fresh- and tired muscles. J Appl Physiol 2000;88(6):2166-2175.
7. Maladen RD, Perumal R, Wexler AS, Binder-Macleod SA. The effects of activation patterns on human nonisometric skeletal muscle performance J Appl Physiol 2007;102(5):1985-1991.
8. Embrey DG. Holtz SL. Alon G. Physiological electrical stimulation of dorsiflexors and plantar flexors during gait in chronic hemiplegia patients.
9. Bowden MG. Neptune RR.
10. Balasubramanian CK and Bowden, MG. Relationship of walking performance to step length in chronic hemiparesis.