Abstract
FES can be of benefit in the treatment of the
patient with incomplete spinal cord injury. A series of 12 subjects who
received FES intervention in the immediate
post injury phase demonstrated significantly improved motor scores in that
average improvement in the most affected weaker limb was 200% (range 128-443%).
FES can assist three principal goals of
rehabilitation-muscle strengthening & endurance, motor recovery and early
gait re-training. Reduction of the effects of disuse muscle atrophy that is
common after SCI and early gait re-education may be two of the principal
benefits of early FES intervention. Chronic
gait deficits, in particular difficulty with swing phase of gait, may also be
minimized with early common peroneal nerve stimulation for the restoration of
active dorsiflexion and hip flexion. Functional outcomes, particularly
ambulatory capacity, in ASIA C and D patients can be improved with early FES intervention.
1.
INTRODUCTION
Restoration of independent
ambulation in the incomplete spinal cord injury (ISCI) patient is generally a
primary goal of rehabilitation. Improvement of motor function and endurance in
muscles affected by the SCI is key to the attainment of a functional gait.
Various studies1,2 have
highlighted the correlation between early recovery of lower extremity motor
function and ability to ambulate following ISCI. Functional
electrical stimulation is recognised as a means of enhancing gait in ISCI. For
instance, it has been demonstrated in ISCI & stroke patients that
stimulation applied to the common peroneal nerve of the affected leg enhances
limb swing and foot clearance during the swing phase of gait3.
However, FES intervention to enhance walking
speed and endurance is applied as a means of correcting gait abnormalities,
generally at a later phase of rehabilitation when chronic gait deficits have
developed. This strategy, however, may have limited benefit for the ISCI
patient months or years post injury as there may be chronic weakness and loss
of endurance in major muscle groups responsible for walking. Disuse atrophy is cited as one of the
contributing factors in muscle weakness and decreased development of muscle
force after SCI. It is thought to occur from loss of muscle
activation due to disruption of central and segmental synaptic drive into
surviving spinal motoneurons.4 The
benefit of early FES intervention after ISCI may be that disuse atrophy in muscles affected by the SCI is, to some
degree, arrested. This may lead to improved ambulatory outcomes.
2. METHODS
2.1 Objectives
1. To describe a protocol of early FES
intervention for the enhancement of motor function in individuals with ISCI. 2.
To document changes in lower extremity motor scores (LEMS) in subjects who
received early FES protocol.
2.2 Study Design
Retrospective study of
changes in lower extremity motor scores in a group of twelve individuals with
ISCI (7 cervical, 5 thoracic) who received early, extensive FES
as part of their rehabilitation on admission to a tertiary rehabilitation
facility.
All subjects were assessed as per the American Spinal Injury
Association (ASIA) classification of spinal cord injury5, a
validated objective measure of neurologic status after spinal cord injury.
Admission and discharge ASIA motor scores
(strength of 5 key muscles per limb graded at 0 to 5 muscle strength, maximum
score per limb = 25). ASIA
impairment scale (C or D) and ambulatory capacity were evaluated on initial and
final assessment.
2.3 Subjects
12 subjects with a diagnosis of ISCI, 8 presented with unilateral lower
limb weakness in that they preserved close to normal motor scores on their less
affected limb (LAL). 4 presented with bilateral weakness in that their LAL
motor score was only marginally higher than their most affected limb (MAL).
Strength of key muscles: hip flexors (L2), knee extensors (L3), ankle
dorsiflexors (L4), long toe extensors (L5) and ankle plantarflexors (S1) was
assessed pre and post treatment. Presentation of neurologic deficit was
according to the ASIA impairment scale. 6
subjects were classified as ASIA C [motor function is preserved below the
neurological level, and the majority of key muscles below the neurological
level have a muscle grade less than 3}. 6 subjects were classified as ASIA D {majority of key muscles have a muscle grade
greater than or equal to 3}.
None of the subjects could stand or walk on initial assessment.
2.3 Intervention
The goals of FES application were 1)
recovery of motor function. 2) improvement of strength & endurance 3) gait
re-training.
Motor Recovery: In muscles demonstrating
flickers (grade 1 muscle activity) a program of therapeutic FES
was applied. This included unilateral or bilateral stimulation of quadriceps,
hamstrings and glutei muscles. As voluntary motor recovery was observed in the
stimulated muscles (grade 2, or better muscle activity) a regimen of muscle
strengthening and conditioning was commenced. This included weight resistance
training and development of anti-gravity strength in the targeted muscle
groups.
Strength & Endurance Training: Retraining of the
flexion withdrawal response of one or both lower limbs was commenced with
stimulation of the common peroneal nerve. The active electrode was placed
behind the head of the fibula, the indifferent over the tibialis anterior
muscle. The limb to be stimulated was positioned with the hip and knee at 90 ° to allow dorsiflexion
through range at the ankle. Stimulation was applied for an average of 1 hour
per day (duty cycle- 5 seconds on/4 off; 35 pulses per second) producing
dorsiflexion through range and was continued until the patient could actively
dorsiflex the ankle. (Average duration of 2 months). As voluntary activity was
observed in the anterior tibial muscles, proprioceptive input was provided with
stimulation to re-train a flexion response at the hip, knee and ankle. As subjects regained anti-gravity power in
the limb flexors they were progressed to a weight resistance training regimen
of extensor muscle groups required for independent standing and erect posture.
Gait
Re-training: Once subjects were able to stand
independently, either in the parallel bars or using a walker, the WalkAide 2
common peroneal foot drop stimulator was fitted to promote early stepping
activity and facilitate the swing phase of gait. The triple flexion response,
obtained with CPN stimulation elicits a flexion moment at the hip and knee and ankle. Balanced ankle dorsiflexion through activation of the
tibilias anterior and peronei muscles facilitates heel contact on initial
stance. A gait pattern, customised for the individual, and programmed using a
hand or foot-switch trigger was set up. Subsequently, as walking ability and
endurance increased with FES assistance, a
tilt-sensor walk was programmed with the WalkAide 2 to provide automatic
control of swing phase of gait. As gait pattern and ambulatory endurance
improved, wheelchair use was discontinued where possible so that walking became
a primary method of mobility. To optimise outcomes in strength, endurance and
standing balance a regimen of weight resistance training with pulleys and free
weights, treadmill training and mat exercises were continued throughout the
entire treatment period.
3.
RESULTS
Mean MAL pre treatment ASIA motor
score was 6.25. Mean post treatment MAL score was 17.5. 6 subjects improved
their MAL motor score by > 200% (range 129% -433%). 2 subjects demonstrated initial MAL scores of 1 and 3, respectively with final scores of 17
and 16 respectively. Initial LAL scores for these subjects were similarly low
at 2 and 8 respectively. Final LAL scores were 18 and 19 respectively. Combined
improvement in MAL+ LAL motor performance was therefore 32 and 24 points
respectively. All subjects achieved independent ambulation at discharge. 7
subjects became fully ambulatory in the community (did not require a wheelchair).
3 Subjects were limited community walkers while 2 subjects managed household
ambulation only. Mean MAL pre/post treatment motor scores for the 12 subjects
based on final ambulatory outcomes are presented in Fig 1. Least affected limb
pre/post scores in Fig 2. 4 subjects with unilateral weakness and an initial
grade 0 of MAL dorsiflexion (DF) regained grade 4 DF on final testing. 1
subject with initial grade 2 MAL/DF regained a grade 4 final score. All other
subjects regained grade 3 MAL/DF (vs
initial grade 0 DF). Of note, all subjects regained a minimum of grade 3 hip
flexion that when combined with active dorsiflexion provided sufficient foot
clearance and limb advancement during the swing phase of gait. Ankle plantar
flexors graded on final evaluation demonstrated a mean score of 3 (6 subjects)
and
grade 4 in the remaining 6 subjects. In 5 subjects an ankle foot
orthosis (AFO) was fitted to the most affected limb to provide mediolateral
stability at the ankle, reduced hyperextension moment at the knee and improved
heel strike during walking.[FES can also be
combined with an AFO to improve walking speed as reported in a previous study5.]
4.
DISCUSSION AND CONCLUSIONS
In recent years, the trend towards early surgical stabilization of SCI
patients has meant that early mobilization and active rehabilitation can be
commenced within the first few weeks of injury. In the case of the incomplete
SCI patient, early muscle activation with FES
may hasten motor recovery. Muscle strengthening and gait re-training using FES may also lessen the deleterious effects of prolonged
immobility and disuse atrophy that frequently were the sequelae of a spinal
cord injury. This small sample study of FES in incomplete spinal cord injury
has attempted to highlight a methodological approach to the application of FES as a means of improving lower extremity motor scores
in the period immediately following the ISCI. Electrical activation of muscles
below the level of injury may mitigate to some degree the disuse atrophy that
would otherwise occur due to loss of normal activation. The effect of afferent
stimulation provided by FES may also play a role in the improved outcomes seen
in this patient group who received early FES. Granat
et al6, concluded, in a study of FES in ISCI subjects, that an
increase in the strength of the hip flexors not directly exercised during FES
gait training could be attributed to the effect of stimulation of the flexor
withdrawal reflex. They suggest also that eliciting a motor response via an
afferent pathway could be a means of strengthening certain muscle groups
weakened due to SCI.
Predicting neurologic recovery and ambulatory potential is difficult in
the incomplete SCI patient especially if there is a pattern of bilateral
weakness. However, early FES application may
lead to functional recovery of motoneurons and improvement of motor scores
earlier in the rehabilitation phase. The objective should be to progress ASIA C
patients to ASIA D. In Brown-Sequard
syndromes where there is mostly unilateral weakness, every attempt should be
made to strengthen the most affected limb so that the ASIA motor score
discrepancy between most and least affected limb is reduced. Data from this
pilot retrospective study would suggest that the use of FES
as an early intervention strategy can assist this objective.
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SCI Physical Therapy/Vol 74, Number 1/Jan:56-66 1994
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Arch Phys Med Rehabil Vol 85, 1718-1723 Oct 2004
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