Abstract
The
study attempts to find out if Functional Electrical Stimulation using a single
channel dropped foot stimulator on tibialis anterior, with timing controlled by
a foot switch can help children with cerebral palsy who walk with a toe gait.
Baseline
kinematic and other data of their usual gait was taken using a computerized
motion analysis system.
Data
collection was repeated at the start and end of stimulation, and after three
months of no stimulation. Mean heel - toe intervals of the affected leg rose
from 4 to 78 ms in the child analysed. Questionnaire
responses by children and parents cite improvements in heel strike in gait,
standing with flat feet, toe clearance during swing phase and increased
stability.
Introduction
Persistent toe walking in children with cerebral palsy
may lead to poor balance, frequent falls, greater asymmetry, and likely
development of fixed deformity resulting in reduced function.
Accepted
current practise to reduce toe walking include orthotics, botulinum toxin,
physiotherapy, exercise and surgery [1,2].
An alternative
approach is that of electrical stimulation. This has been used for many years
in the rehabilitation of muscle activity following neurological damage, e.g.
spinal cord injury and stroke [3,4,5]. Considerable work on Functional
Electrical Stimulation (FES) has been carried out in adults with hemiplegic
gait [6,7]. [6] for example, demonstrated an improvement in walking speed of
10% or more by 12 of the 16 patients receiving FES and a mean reduction in
physiological cost index of 33% when electrical stimulation was used as an
orthosis. There were also improved scores on quality of life measures.
In comparison, less work has been reported in
assisting gait in children with cerebral palsy with electrical stimulation.
However, the general view is that although requiring further work it offers
possible therapeutic and functional benefits [8,9,10].
There is conflict in the literature regarding the use of electrical
stimulation in children with cerebral palsy. Some evidence supports the use of
stimulation to the tibialis anterior muscle, others support stimulation of the
calf muscles. In this, the first of two pilot studies, the aim is to quantify
the effect of stimulating the tibialis anterior muscle during gait. A second
study is planned to investigate the effects of stimulating calf muscles.
Methods
An ABA approach was used. This study design was
thought appropriate to a pilot study with a small sample size. It was not
possible to use a placebo or to use double blind studies due to the nature of
the intervention. Ethics approval was obtained from the Queen Mary’s Hospital
(QMH) Trust.
Patients who presented with a toe-walk gait were
recruited from existing departmental caseload together with referrals from
other departments. Seventeen children were screened for the study. Of
these, twelve were recruited (8 boys and 4 girls, with an age range of 6 to 14
years, mean 9 years). To date, all have completed phase A1, five are in phase
B, three are in A2, and four have completed the trial.
The selection criteria were:
·
Diagnosis of
cerebral palsy.
·
Walking with toe
gait indicated by limited heel contact, increased tripping and falling, typical
wear pattern on shoe.
·
Had 90 degrees
dorsiflexion passively, with knee extended. Checks were also made to discount
associated problems, e.g. other contractures and joint problems.
·
The child was
co-operative, with parents/ carers motivated to carry out programme.
·
Tolerant of
machine.
· Able to walk independent of aids.
The exclusion criteria were:
·
Surgery or Botox
injection within 18 months.
·
Concurrent use of
fixed AFO.
·
Insufficient
parental/guardian/carer support to use equipment reliably.
·
A need for more
than single channel stimulation.
·
Severe
contractures and/or fixed deformities
Intervention
In the first A period (0-3 months), baseline data of
the child’s gait patterns (with any current orthosis if applicable) were
recorded twice at the start of month 1, 1 week apart (session1 and session 2)
and once at 3 months (session 3). Session 1 was used to acclimatise the subject
to the gait laboratory and the measurements to be made. Data from this session
were not used in the final analysis.
At the start of phase B (3-6 months) the electrical
stimulator was set up. Stimulation was applied to the Tibialis Anterior muscle
(directly through the motor nerve or through stimulating the flexor withdrawal
reflex action), using the Salisbury (Salisbury Hospital, UK) ODFS III single
channel dropped foot stimulator. The stimulation envelope timings were adjusted
to optimise improvements in the movement of the leg and foot during gait. The
foot switch was positioned under the heel or metatarsal head. A follow up took
place the next day to ensure that electrical stimulation was being applied
correctly. For the three months of this phase the stimulator was to be used
throughout the day as a gait assist device, within the confines of the subjects’
daily schedule.
The gait measurements were carried out at the follow
up (session 4) and end of this phase (session 5). Data were collected with and
without stimulation to facilitate investigation of the orthotic and therapeutic
effect of stimulation. In addition a patient questionnaire (developed in
conjunction with the Clinical Audit Department at QMH) was used after 1 and 3
months of this phase to discover the subjects’ usage, compliance and
perspective. This phase has not been completed, so a full analysis of all
subjects is not yet possible
In the final A period, the electrical stimulation
orthosis was withdrawn, with gait data being recorded at the start and end of
this phase (session 5 and session 6).
Normal physiotherapy treatment by the child’s regular
therapist has continued throughout all phases of the programme. Additional
monthly checks and telephone contact being offered in case of problems during
phase B to ensure correct use of equipment, but with no additional therapy. The
gait analysis session (session 5) at the end of phase B includes measurements
needed for the start of phase A2 i.e. gait without stimulation.
Data
Collection
Subjects were timed whilst they walked 25 metres with a heart rate monitor (Polar Electro Oy, Kempele, Finland). Heart rate was recorded before and after each walk for three walks to give an estimate of the physiological cost index (PCI).
Passive and active ranges of motion for ankle, knee
and hip joints were measured using an electric goniometer (Biometrics Ltd, Cwmfelinfach,
UK).
Subjects stood on a
dual 3.3 metre long force platform [11] with one foot on each platform to
record their weight distribution in the standing trials. Subjects then walked
over the platform for the walking trials, from which kinetic and spatio-
temporal data were obtained
Sagittal and frontal plane video were recorded onto
tape and displayed using a split screen TV monitor. The video record was
employed to aid in the analysis of the kinematic data.
Retroreflective markers were attached to
the left and right acromion processes, sacrum, left and right asis, thighs,
lateral epicondyles, shanks, and at the level of the lateral malioli and third
metatarsals (modified Helen Hayes). The coordinate data of the markers for
standing and walking were collected using a six camera Mac Reflex 60Hz system
(Qualisys AB, Partille, Sweden).
A record of the marker positions for each
session was made using frontal, rear, left and right photographs.
Data
Analysis
Measuring the heel-toe interval tells us how often the
heel reaches the floor and in what sequence relative to the toe. This paper
reports on data from one subject for phases A1 and B.
Using data collected in standing for the ankle and toe
markers, the z-coordinates of these markers at heel and toe contact were found.
These values were used as thresholds to estimate the timings of heel and toe
contact in the walking data. 103 steps of the no-stimulation condition and 74
steps of the with-stimulation condition were analysed in this way. The mean, maximum
and minimum intervals between heel and toe contact for each condition were
calculated.
Other analyses underway include step length, degree of
knee flexion at heel contact, PCI, and walking speed with heel contact.
Results
Figure 1 is a
graph and table, which shows the mean heel-toe contact interval (int) for one
subject, whose right leg was stimulated, for the no-stimulation and stimulation
conditions for the left (l) and right (r) feet. Also it shows the maximum and
minimum heel-toe intervals.
Questionnaire
returns of the orthotic effect and acceptability so far include improvements in
heel strike in gait, standing with flat feet, toe clearance during swing phase
and increased stability.
Discussion
The analysis presented suggests the efficacy of FES in
the case considered. Analysis of a wider range of data detailed above from all
the children in the study is underway.
The additional monthly checks in phase B
were necessary to ensure correct use of the equipment. Although no therapeutic
input was intended, it is recognised this may result in a bias in the results.
References
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Acknowledgments
This
study was supported by Remedi and the S W London Community NHS Trust. Thanks go
to Faye Bater for help with the measurements, the children, and their
parents/carers