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Effects of
orthoses on postural
stability in children
with Down syndrome
Kathy Martin PT DHS, Assistant Professor of Physical
Therapy, Krannert School of Physical Therapy, University of
Indianapolis, Indianapolis, USA.
Correspondence to author at Krannert School of Physical
Therapy, University of Indianapolis, Indianapolis, Indiana, USA.
This study explored the effects of a flexible supramalleolar
orthosis (SMO), indicated to decrease pronation associated
with hypotonia, on postural stability in children with Down
syndrome. Seventeen children with Down syndrome (nine
males, eight females; mean age 5 years 10 months, SD 17.2
months; range 3 years 6 months to 8 years) were tested three
times in a 10-week period (weeks 1, 3, and 10) using the
Standing and the Walking, Running, and Jumping dimensions
of the Gross Motor Function Measure (GMFM), and the
Balance subtest of the Bruininks-Oseretsky Test of Motor
Proficiency (BOTMP). Range of motion measurements were
used to explore the influence of joint laxity. Significant
improvement was found with SMOs compared with shoes only
in the Standing dimension (
p=0.001) and the Walking,
Running, and Jumping dimension (
p=0.0001) of the GMFM,
both at the time of fitting (week 3) and after 7 weeks of
wearing SMOs (week 10). For the BOTMP Balance subtest,
significant improvement (
p=0.027) was seen only at the end
of the 7-week study period. Amount of joint laxity did not
influence response to orthotic intervention. This study showed
that young children with Down syndrome showed immediate
and longer-term (after 7 weeks of use) improvement in
postural stability with the use of flexible SMOs.
Down syndrome, a genetic disorder occurring in 1.3 per 1000
live births in North America, is a common cause of neurode-
velopmental disability (Harris and Shea 1991) that includes
hypotonia, joint laxity, delayed achievement of motor mile-
stones, and disturbances in postural control (Rast and Harris
1985, Shumway-Cook and Woollacott 1985, Lauteslager et al.
1998, Russell et al. 1998). In a longitudinal study, Connolly et
al. (1993) found that children with Down syndrome contin-
ued to have problems with postural stability into adolescence.
The neuropathology associated with Down syndrome, includ-
ing a smaller cerebellum and brainstem, is thought to be a fac-
tor in these deficits (Shumway-Cook and Woollacott 1985,
Connolly et al. 1993).
Improving postural stability leads to better functional
motor performance (Westcott et al. 1997, Lauteslager et al.
1998). Anecdotal reports from physical therapists and parents
indicate that children with Down syndrome have improved
postural stability when they use orthoses. However, this belief
has not consistently been supported in the literature (Knutson
and Clark 1991). Only one study has investigated the use of
orthoses during gait in children with Down syndrome and it
showed decreased external rotation in the foot progression
angle, more consistent foot function during gait, and dec-
reased heel eversion in standing with foot orthoses (Selby-
Silverstein et al. 2001).
Genaze (2000) recommended supramalleolar orthoses
(SMOs) for children with Down syndrome as conventional foot
orthoses are usually not sufficient to control pronation sec-
ondary to hypotonia and joint laxity; yet no study has investi-
gated the use of SMOs in children with Down syndrome. The
purpose of this study, therefore, was to determine the immedi-
ate and longer-term effects of a flexible SMO on postural stabil-
ity and physical disability in children with Down syndrome.
In addition, the influence of joint laxity on response to the
orthoses was investigated. The primary research hypothesis
was that flexible SMOs would improve postural stability in
children with Down syndrome, as measured by dimensions
of the Gross Motor Function Measure (GMFM; Russell et al.
1993) and the Bruininks-Oseretsky Test of Motor Proficiency
(BOTMP; Bruininks 1978). Secondary hypotheses were that
this effect would be greater after several weeks of wearing the
orthoses and that children with Down syndrome with greater
joint laxity would benefit more from SMOs.
Participants were recruited from central and northern Indiana,
USA through local parent support groups. They were eligible
for the study if they met the following criteria: aged between
3 years 6 months and 10 years; diagnosis of Down syndrome;
no parent-reported history of inner ear impairment or
uncorrected visual impairment; ability to follow simple com-
mands; no history of seizures; and independent ambulation
for 30 yards. This study was approved by the Committee on
Research Involving Human Participants at the University of
Indianapolis, USA. Informed, written consent was obtained
from a parent or guardian before participation in the study.
Seventeen children (nine males, eight females) with Down
syndrome participated in the study between July 2002 and
January 2003. Data from three children were eliminated from
the final analysis: one was unable to participate appropriately
in the testing, one did not tolerate the orthoses, and one was
Developmental Medicine & Child Neurology 2004, 46: 406­411
See end of paper for list of abbreviations.
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Orthoses and Balance in Children with Down Syndrome Kathy Martin
a low-scoring outlier on all dependent variables. For the 14
remaining participants, mean age at initial testing was 5 years
10 months (standard deviation [SD] 17.2 months) and range
was 3 years 6 months to 8 years.
To explore the influence of joint laxity, participants were
placed in two groups by creating a single variable that was
the total of six range of motion measurements (right and left
knee hyperextension, elbow hyperextension, and ankle dorsi-
flexion). The two groups were defined as more lax (those with
a total laxity score of 60° or more) and less lax (those with a
score of less than 60°). Because no precedent exists in the lit-
erature to grade severity of joint laxity in children with Down
syndrome, these operational definitions were set after exam-
ination of the data. The range of scores for the less lax group
(n=8) was 33 to 56° (mean 42.5, SD 9.1) and for the more lax
group (n=6) was 64 to 124° (mean 88.2, SD 23.7).
Gross Motor Function Measure
The GMFM can document change over time in gross motor
function. Scores are reported as a percentage of items complet-
ed (Russell et al.1993). Only dimensions D (Standing) and E
(Walking, Running, and Jumping) were used in this study
because one criterion for participation was independent
ambulation, thus the other dimensions had little clinical rele-
vance. The Standing dimension examines skills that progress
from pulling to stand to independent standing and picking
an object up off the floor without support. The Walking,
Running, and Jumping dimension examines skills that
include various aspects of gait, kicking a ball, jumping, and
going up and down stairs. Recommended modifications to
the standard testing procedure, such as demonstration and
simplified verbal cues (Gémus et al. 2001) and use of parent-
report (Russell et al. 1998), were used. Russell et al. (1998)
established the test­retest reliability (within 2 weeks) of the
GMFM for a sample of children with Down syndrome with an
intraclass correlation coefficient of 0.98 for the Standing
dimension and 0.95 for the Walking, Running, and Jumping
Bruininks-Oseretsky Test of Motor Performance
The BOTMP is an evaluative tool that has shown that children
with Down syndrome perform poorly in the areas of Running
Speed and Agility, Balance, Strength, and Visual Motor Control
(Connolly and Michael 1986, Connolly et al. 1993). The cur-
rent study used only Balance and Running Speed and Agility
because they are the subtests that examine skills requiring pos-
tural stability. These two subtests include a shuttle run(for a dis-
tance of 45 feet, pick up an object, and run back, timed) and
static and dynamic balance activities on the floor and on a low
balance beam. Only 11 of the 14 participants were tested with
the BOTMP, as three children were younger than the minimum
age requirement. Testing and scoring followed the procedures
as described by the BOTMP manual (Bruininks 1978). Results
are reported as raw point scores (number of points achieved).
The BOTMP manual reports test­retest reliability for the
Running Speed and Agility subtest of r=0.78, and for the
Balance subtest of r=0.56 (Bruininks 1978).
Figure 1: Flexible supramalleolar orthosis.
Table I: History and maturation effect test results (shoes only
Dependent variable
BOTMP Balance subtest
GMFM Standing dimension
GMFM Walking, Running, and Jumping
BOTMP, Bruininks-Oseretsky Test of Motor Proficiency; GMFM, Gross
Motor Function Measure;
Greenhouse-Geisser adjusted values.
Table II: Results of repeated measures ANOVA
Dependent variable
GMFM Standing
GMFM Walking, Running, Jumping
BOTMP Balance
Session for `shoes only'
Session for `shoes+SMOs'
Condition at second session
Condition at third session
GMFM, Gross Motor Function Measure; BOTMP, Bruininks-
Oseretsky Test of Motor Proficiency; SMOs, supramalleolar
significant at p=0.05.
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The flexible SMO used in this study was made from a hybrid
plastic (Fig. 1), and is different from other flexible SMOs in
that it is thinner and has a shorter footplate (approximately
three-quarters length). This orthosis is thought to use com-
pression to promote midline positioning and enhance joint
receptor function, as opposed to the more traditional concept
of wedging the foot into a neutral position through posting of
the footplate. It can also be fabricated from girth, length, and
width measurements, thus eliminating the need for a cast mold
of the child's foot. This orthosis was chosen for this study
because it was specifically designed for use by children with
hypotonia, whereas other SMOs are used by children with
either high or low tone.
This study used a repeated measures design with three testing
sessions over a 10-week period. Testing was done either in the
child's home or in a clinic. At the initial meeting, children were
measured for the orthoses by using the tools and protocol
established by the SMO manufacturer (Midwest Orthotic and
Technology Center, South Bend, Indiana). Passive ROM mea-
surements for ankle dorsiflexion, knee hyperextension, and
elbow hyperextension were taken, using the standard posi-
tions and protocol described in Norkin and White (1995). The
children were then tested with the BOTMP (if older than 4
years 6 months) and the GMFM in random order, in the `shoes
only' condition.
Approximately 2 to 3 weeks later, the children were first test-
ed in their shoes only. Then the children were fitted with their
SMOs and were allowed to walk around the testing area until
they felt comfortable enough in the orthoses to proceed with
the selected GMFM and BOTMP tests. Parents were instructed
as follows: how to apply the orthoses correctly and monitor
skin integrity; that their child should wear the SMOs 8 hours
per day, every day until the final testing session after approxi-
mately 6 weeks; to discontinue use of the SMOs and call the
author if their child experienced any problems with the
orthoses; and to continue with their current daily routine,
including physical therapy and recreational activities. Adher-
ence with the SMO-wearing schedule was monitored by having
parents complete a daily log sheet.
After approximately 6 weeks of wearing the SMOs, the
children returned for a final testing session. The child was
first tested in the `shoes+SMOs' condition, then the SMOs
were removed and the child was tested in the `shoes only'
condition. Parents were asked to hand in the daily log sheet
and instructed on how to determine when the orthosis no
longer fitted their child.
Most participants were unable to run fast enough to obtain
a score on the BOTMP Running Speed and Agility subtest.
This created a large floor effect for this variable; therefore, it
was not considered to be a useful measure for the purposes of
this study and was eliminated from further analysis.
Data analysis
Statistical analysis was done with SPSS (version 10.0). Statistical
significance was set at p=0.05 for all tests. First, data were
examined for normality, then the GMFM and BOTMP scores
from the `shoes only' condition in each of the three sessions
were compared for maturation and history effects by using a
one-way repeated measures analysis of variance (ANOVA).
A two-way repeated measures ANOVA was used to look for
differences within participants over time (second and third
sessions) and across conditions (wearing `shoes only' or
`shoes+ SMOs') for both GMFM dimensions and the BOTMP
Balance subtest. Significant interactions between time and
condition were explored with tests of simple main effects by
using a Bonferroni correction of alpha.
To explore the contribution of joint laxity to the findings,
the more lax group was analyzed separately from the less lax
group, and they were compared for age and amount of time
the orthoses were worn. Mean difference in scores attributed
to the orthotic intervention (third session `shoes+SMOs'
minus the second session `shoes only') between the two groups
was calculated for each dependent variable and compared by
using independent t-tests.
Individual responses to the orthoses were explored by cal-
culating a `total response' score for each child. This score was
obtained by first converting the BOTMP scores to a percentage
of points available so they would be on the same scale as the
Developmental Medicine & Child Neurology 2004, 46: 406­411
GMFM Standing (%)
Session 3
Session 3
Session 2
Figure 2: Gross Motor Function Measure (GMFM) Standing
dimension results. Numbers in boxes represent mean change
with supramalleolar orthoses (SMOs) intervention at each
, shoes+SMOs; , shoes only. Condition
significant at p=0.001.
umping (%)
Session 2
Figure 3: Gross Motor Function Measure (GMFM) Walking,
Running, and Jumping dimension results. Numbers in
boxes represent mean change with supramalleolar
orthoses (SMOs) intervention at each session.
, shoes +
, shoes only. Condition significant at p=0.0001.
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GMFM scores. Then the per cent change attributable to the
orthoses (third session `shoes+SMOs' minus second session
`shoes only') was calculated for each of the three dependent vari-
ables and summed, indicating the percentage point improve-
ment (or decline) in function experienced by each child.
For this study, test­retest reliability intraclass correlation coeffi-
cients for each dependent variable for the first and second
testing sessions (2 to 3 weeks) were as follows: 0.67 for the
Standing dimension, 0.93 for the Walking, Running, and
Jumping dimension of the GMFM, and 0.81 for the Balance
subtest of the BOTMP.
The 14 children wore the SMOs for an average of 5.68 hours
per day (SD 1.96) for a mean of 49.07 days (SD 8.45). Table I
indicates that there was no significant difference in the depen-
dent variables in the `shoes only' condition across the three
testing sessions.
For both GMFM dimensions, significant differences were
found between orthotic conditions but not between testing
sessions (Table II; Figs. 2, 3), and there was no significant inter-
action between conditions and sessions. For the BOTMP
Balance subtest, a significant interaction between condition
and sessions (p=0,039) required exploration of simple main
effects (Table II; Fig. 4). This analysis showed that the SMOs
offered a mean improvement of 0.64 points over the `shoes
only' at the second session, and a larger effect with a mean
improvement of 2.64 points by the third session.
Overall, the group that was more lax scored lower on all
dependent measures compared with the less lax group (Fig. 5).
When the two groups were compared for age and amount of
time the SMOs were worn, they were significantly different
only in age (t=2.18, p=0.05). The more lax group had a mean
age of 5 years 2 months whereas the less lax group had a mean
age of 6 years 6 months. Mean difference attributed to the
orthotic intervention was not significantly different between
the two groups on any variable (GMFM Standing, p=0.271;
GMFM Walking, Running, and Jumping, p=0.210; BOTMP
Balance p=1).
Individual `total response' scores showed that percentage
point changes ranged from ­2.6 to 32.5% (Table III). Seven of
the 14 children improved by at least 8 percentage points, and
four children improved from 2 to 4 percentage points.
This study supports the hypothesis that flexible SMOs have a
positive effect on measures of postural stability in children
with Down syndrome. Because the data from the three `shoes
only' conditions (Table I) were not significantly different, the
changes seen in this study were unlikely to be a result of matu-
ration or outside activity. Significant changes in performance
were detected immediately and after 7 weeks by the two GMFM
dimensions, and by the end of the study for the BOTMP
Balance subtest. The skills in the GMFM Standing dimension
required less postural stability and were more likely to have
already been mastered. The GMFM Walking, Running, and
Jumping dimension tested skills that were more challenging,
and the BOTMP Balance subtest tested skills that were the
most difficult and complex. Thus the tendency was that
when the task was more challenging, more time was needed
for significant improvement to be seen. The trend in this
study is supported by Palisano et al. (2001), who also noted
that more time is required to learn movements that are more
complex and thus require greater motor control and limb
Children with Down syndrome with greater joint laxity did
not show a greater treatment effect with the flexible SMOs.
Even though the more lax group scored lower on all depen-
dent measures, the magnitude of change attributed to the
Orthoses and Balance in Children with Down Syndrome Kathy Martin
TMP Balance (point score)
Session 2
Session 3
Figure 4: Bruininks-Oseretsky Test of Motor Proficiency
(BOTMP) Balance subtest results. Numbers in boxes represent
mean change with supramalleolar orthoses (SMOs)
intervention at each session.
, shoes+ SMOs; , shoes
only. Interaction significant at p=0.039. Condition at
session 3 significant at p=0.027.
er cent score
GMFM-S shoes
GMFM-WRJ shoes
TMP shoes
Figure 5: Comparison of mean scores when grouped by
laxity category. Sessions labelled `shoes' are session 2,
sessions labelled `SMOs' are session 3. GMFM-S, Gross
Motor Function Measure, Standing dimension; GMFM-WRJ,
Gross Motor Function Measure, Walking, Running, and
Jumping dimension; BOTMP, Bruininks-Oseretsky Test
of Motor Proficiency; SMOs, supramalleolar orthoses;
, more lax;
, less lax.
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orthotic intervention was similar between groups. These
findings are consistent with two previous studies that have
attempted to examine the impact of joint laxity on children
with Down syndrome (MacNeill-Shea and Mezzomo 1985,
Livingstone and Hirst 1986). Both of these studies conclud-
ed that the orthopaedic and motor skill problems commonly
seen in children with Down syndrome were related to hypo-
tonia but not joint laxity.
For the GMFM Standing dimension, the mean improvement in
score seen with the orthoses of approximately 2 percentage
points could mean completing a floor to stand transition with-
out support, or an increase of single leg balance by as much as 7
seconds (Russell et al. 1993). For the GMFM Walking, Running,
and Jumping dimension, the mean improvement with orthoses
of approximately 3 percentage points could mean stepping
over a tall obstacle independently, running with control versus
walking quickly, being able to hop on one foot at least three
times, or being able to consistently go up or down stairs reci-
procally versus a step-to-step pattern (Russell et al. 1993).
For the BOTMP Balance subtest the mean improvement with
orthoses of 17% could reflect a 2- to 3-fold increase in single-
leg standing balance or the ability to take two to three times
as many steps on a balance beam (Bruininks 1978). All of
these changes seem to be clinically important, particularly in
enabling school-aged children with Down syndrome to
more readily keep up with their peers.
The rate of change in this study also seems notable. Two
studies have reported that improvement in gross motor skills
occurred at a slower rate in children with Down syndrome
over the age of 3 years (Russell et al. 1998, Palisano et al.
2001). Yet in this study, significant improvement in postural
stability was found within minutes for less complex skills and
within 7 weeks of intervention with flexible SMOs for more
challenging skills.
The question of how and why a flexible orthosis produces an
improvement in the postural stability of children with Down
syndrome has not been answered. Biomechanical and neuro-
logical explanations have been offered in previous literature
on orthoses. Orner et al. (1994) proposed that orthoses create
an improved biomechanical alignment that allows muscles to
work in a more appropriate length­tension relationship. The
orthosis in this study is flexible and does not hold the subtalar
joint rigidly in neutral, thus small increments of movement
around midline are allowed while preventing fixation in an
abnormal position or movements into the extreme end
range of pronation. Because of the movement allowed,
Hylton (1989) has hypothesized that flexible orthoses pro-
vide improved and more consistent proprioceptive feed-
back, which in turns improves control of movement.
The trimlines of the SMO are also different from tradition-
al styles in that they are proximal to the first metatarsal head
and just distal to the fifth metatarsal head, which is thought
to decrease the forefoot abduction that often occurs with
pronation. Another feature of the orthosis in this study is its
lack of full-length footplate which, combined with its flexibil-
ity, allows the development of normal ankle strategies in
response to balance perturbations and development of
jumping skills. Traditional orthoses with a full-length rigid
footplate may inhibit the graded shifting of weight that
occurs with an ankle-strategy balance response. Shumway-
Cook and Woollacott (1985) have recommended that treat-
ment to improve the postural control of children with Down
syndrome should focus on assisting development and refine-
ment of postural synergies. The flexible SMO used in this study
would seem to be consistent with accomplishing that goal.
One limitation of this study was that participants were all chil-
dren with Down syndrome between the ages of 3 years 6
months and 8 years; thus the results should not be generalized
to children with other disorders or those who are outside this
age range. This study did not limit any outside activities that
may have contributed to the development of postural stability
during the study period. Half of the participants were tested
in their homes, thus the testing environment also varied.
Another limitation of the study was the participants' cognitive
understanding and ability to follow verbal directions for com-
plex skills, such as walking between 2 lines on the floor.
Finally, the analysis of influence of joint laxity lacked reliability
analysis and justification from previous literature. However,
given the lack of a definitive method for grading joint laxity, the
method used in this study offered preliminary information
about an interesting clinical question.
The study could be broadened to include children with a diag-
nosis of hypotonia of any origin. Also, the age range could be
lowered to look at the effect of orthoses on development of
independent gait. Finally, many different types of orthotic
devices are commercially available; a comparison of this SMO
with other types with different features would help clinicians
choose the orthoses that would most benefit their patients.
Developmental Medicine & Child Neurology 2004, 46: 406­411
Table III: Individual total response scores with orthotic
Total change
Overall percentage point change = session 3 `shoes+SMOs' minus
session 2 `shoes only'. BOTMP Bruininks-Oseretsky Test of Motor
Proficiency; GMFM, Gross Motor Function Measure; WRJ, Walking,
Running, and Jumping dimension.
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Orthoses and Balance in Children with Down Syndrome Kathy Martin
Improvements in the postural stability of children with Down
syndrome, aged 3 years 6 months to 8 years, were seen with the
use of a flexible SMO. Immediate and longer-term improve-
ments were noted in skills that were less complex; more com-
plex skills showed significant improvement by the end of the
7-week intervention period. Although the children with more
lax joints scored lower on all dependent measures across all
conditions, there was no difference in response to the orthoses
between the groups with more or less joint laxity. Results of the
current study show that improvement in postural stability of
children with Down syndrome is possible through relatively
short-term use of flexible SMOs. These results suggest that
clinicians should consider the use of flexible SMOs for school-
age children with Down syndrome as a way of improving their
overall functional mobility.
DOI: 10.1017/S0012162204000659
Accepted for publication 8th December 2003.
This study was undertaken in partial fulfillment of the requirements
of the Doctor of Health Science degree at the University of
Indianapolis. I thank Elizabeth Domholdt PT EdD, Susan Harris PT
EdD, and David Chapman PT EdD for their advice and guidance
throughout the study and for their thoughtful review of the
manuscript, and Clyde Killian for his assistance with statistical
analysis. I also thank Bernie Veldman BOC Orthotist and the
Midwest Orthotic and Technology Center in South Bend, Indiana,
USA, for providing the SureStep orthoses used in this study.
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List of abbreviations
Bruininks-Oseretsky Test of Motor Performance
Gross Motor Function Measure
Supramalleolar orthosis