PIVSPWIScoliosis .pdf

Nom original: PIVSPWIScoliosis.pdfTitre: Postural Imbalance and Vibratory Sensitivity in Patients With Idiopathic Scoliosis: Implications for TreatmentAuteur: Nancy N. Byl, Susan Holland, Anne Jurek, Serena S. Hu

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Postural Imbalance and Vibratory Sensitivity in
Patients With Idiopathic ~coliosis:implications
for Treatment
N. Byl, PhD, PT'
Susan Holland, BS, M P T 2
Anne jurek, BS, M P T ~
Serena S. Hu, MD4
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diopathic scoliosis occurs in
2-4% of the population. It
affects females disproportionately more than males and
comprises 70% of all cases of
scoliosis (10,12). Idiopathic scoliosis
is classified as a structural scoliosis,
even though there can be no bony
abnormalities of the vertebral bodies
(23). Multifactorial etiologies based
on heredity, musculoskeletal, and
neurological factors have been proposed (6,23-25,29,31,37,48).
It has been suggested that a sexlinked autosomal gene factor may
create a mild central nervous system
abnormality that predisposes an adolescent to idiopathic scoliosis (5).
Associated risk factors during adolescence, such as maturity of the epiphyses at the onset of the curve, rapid
bone growth, or extensive bone
growth, appear to influence curve
severity and progression. Sensory
problems (eg., position sense, vibration) may also be important risk factors (14,28,32,42). For example, several investigators report that damage
to the posterior column at the level
of the dorsal root or in the thoracic
cord induces scoliosis in animals (22,
26,33,34,47). Abnormalities in postural righting (25) signaled by poor
integrative balance responses in sensory-challenged conditions (7,8,3639,46), decreased muscle spindle or

Sporadic research reports of decreased proprioception and balance problems have been
reported in subjects with idiopathic scoliosis, yet these sensory motor deficits have not been addressed
in conservative clinical management programs. The purpose of this study was to compare both balance
reactions and vibratory sensitivity (as an estimate of proprioception) in patients with idiopathic scoliosis
(N = 24) and age-matched controls (N = 24). Balance was measured by the ability to pass a series of
simple static and complex sensorychallenged balance tasks. Vibratory thresholds were measured with
the Bio-Thesiometer at the cervical spine, wrist, and foot. Compared with age-matched controls,
regardless of curve severity or spinal hsion, the subjects with idiopathic scoliosis had similar simple
static balance responses when the somatosensory system was stable (with or without vision or head
turning), but they were significantly more likely to fail the complex, sensorychallenged balance tasks
when the somatosensory system was challenged by an unstable position of the feet, particularly when
the eyes were closed. The vibratory thresholds were similar in subjects with scoliosis and their agematched controls, but individuals with moderate to severe scoliosis P-25") had significantly higher
vibratory thresholds than those with mild curves. These findings suggest there may be problems with
postural righting in patients with idiopathic scoliosis, particularly when the balance task challenges the
vestibular pathways. Although vibration sensitivity did not distinguish normal healthy individuals from
individuals with idiopathic scoliosis, those with more severe scoliotic curves appear to have a high
threshold to vibration. These balance and vibratory differences could either be interpreted as etiologic
risk factors or as consequences of spinal asymmetry. In either case, given that curves can continue to
progress even into the adult years, improving the ability to right the body with gravity could help
maintain the balance of the spine despite st~ctvralasymmetry.

Key Words: idiopathic scoliosis, balance reactions, proprioception


Professor; Chair, University of California, San Francisco, San Francisco State University, Graduate Program
in Physical Therapy, San Francisco, CA; Director, University of California, San Francisco, Graduate Program
in Physical Therapy, School of Medicine, Box 0736, 374 Parnassus #lo!, San Francisco, CA 94143-0736
Staff Physical Therapist, BAK Physical Therapy and Rehabilitation Services, Redwood City, CA
Staff Physical Therapist, Department of Physical Medicine and Rehabilitation, California Pacific Medical
Center, San Francisco, CA
Associate Professor, Department of Orthopaedics, University of California, San Francisco, Schwl of
Medicine, San Francisco, CA
Ms. Holland and Ms. jurek completed this study in partial fulfillment of the master's degree in physical
therapy, University of California, San Francisco, San Francisco, CA.
This study was funded in part by the Physical Therapy Fund of the California Chapter of the American
Physical Therapy Association.


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tendon stretch receptor responses
(49). abnormal labyrinthine function
(18,31), or dysfunction in proprioceptive sensation (3,4,15,40) have
also been reported in this subject
From a mechanical perspective,
the spine is a flexible column of vertebral bodies linked structurally and
functionally together by connective
tissue (ligaments, discs, and fascia)
and muscle. This column is constantly subjected to the forces of gravity. Through complicated, interactive,
automatic, and voluntary systems, the
trunk must constantly right itself with
gravity, maintain stability during
movement, and provide a reliable
foundation from which the extremities can work. Postural righting reactions depend on the integration of
information from the visual system,
the somatosensory system, and the
integrative vestibular system (vestibulo-spinal, vestibulocerebellar, and
the vestibulo-occular pathways) (2,13,
17). Visual fixation provides a powerful orientation to environmental u p
rightness, but when the eyes are
closed, righting with gravity is more
dependent on the sensory system
(touch receptors, joint receptors,
muscle afTerents, golgi tendon organs) and the vestibular system (labyrinth, vestibular nuclei, and integrative pathways) (2,30).
Initial treatment of idiopathic
scoliosis is observation. When the
curve reaches 30°, conservative treatment, including bracing (40,42),
electrical stimulation (43), and exercise, is introduced (8,9). Optimistically, these conservative strategies can
maintain fitness, general flexibility,
strength, and tone and may contrib
Ute to maintaining or slowing curve
progression. However, conservative
treatment does not usually correct
the problems with alignment (10,12,
23). When the curve progresses to
40" or more, surgery may be considered. Although surgical fusion improves alignment and structurally stabilizes the spine (eg., the application
of rods or fusion), disabling back
JOSFT 0 Volume 26 Number 2 August 1997

pain, cosmetic deformity, and cardiopulmonary compromise may still result in the adult years (6,12,16,24,31,
Balance and proprioception are
not routinely measured in patients
with idiopathic scoliosis, neither
when the curvature is detected nor
during the observational or postoperative years. Thus, it is difficult to
know whether reported problems in
balance and position sense are a consequence of the scoliotic spinal asymmetry or etiologic risk factors that
facilitate the development of the scoliosis. In order to develop new intervention strategies by physical therapists, more evidence is needed to
confirm the presence of dysfunction
in position sense and postural righting in patients with idiopathic scoliosis.
With a heterogeneous group of
subjects with idiopathic scoliosis, the
purpose of this study was to investigate the relationship between scoliosis, righting reactions (as measured
by complex balance responses), and
position sense (estimated by vibration
thresholds on defined body landmarks). This study closes a gap in the
literature by measuring: 1) both balance and vibration in patients with
idiopathic scoliosis and healthy agematched controls and 2) correlating
curve severity, vibratory threshold,
and postural imbalance.

A convenience sample of 48 females between the ages of 10 and 55
years consented to participate in this
study. Twenty-four of the subjects had
idiopathic scoliosis (mean age = 33.3
years; median age = 35.5 years) and
were recruited from the Spine Clinic
at the Medical Center of the University of California, San Francisco
(UCSF), San Francisco, CA. All of the
patients were being followed by an
orthopaedic surgeon. Patients with
congenital deformities, structural de-


fects of the spinal vertebra, neuromusculoskeletal diseases other than
idiopathic scoliosis, a history of
chronic ear infections, dizziness, or
vertigo were excluded. Patients who
were 6 months postsurgical fusion
were eligible to participate.
In the 24 subjects with idiopathic
scoliosis, the magnitude of the primary spinal curves ranged from 10 to
60". Ten subjects had curves greater
than 25" and 11 had curves between
10 and 25". Only three subjects had
curves between 25 and 40". Radiologi-

The primary spinal
curves ranged from

cal records for three of the subjects
were unavailable. Surgical spine fusion
had been performed on eight subjects
(all with curves greater than 40").
Seven subjects, who were managed
conservatively, were wearing a brace.
The 24 age-matched, female control subjects (mean age = 33.3 years;
median age = 34.5 years) were recruited from the faculty and students
of the University of California, San
Francisco and San Francisco State
University (SFSU), or were friends or
relatives of students and faculty in
the Graduate Program in Physical
Therapy. Subjects were excluded if
they had any history of neurologic
disorders, chronic sinusitis, ear infections, vestibular or proprioceptive
problems, falls, chronic ankle sprains,
or scoliosis.
This study was approved by the
UCSF Committee on Human Research. Each subject (or parent)
signed a consent form prior to beginning the study.

Testing was performed by two
graduate students from the UCSF/
SFSU Graduate Program in Physical

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Therapy. Patients with scoliosis were
tested in the clinic, while control s u b
jects were tested at home or in the
physical therapy laboratory. The balance test protocol applied in this
study was modified from the balance
series originated by Nashner et al
(30) and reported by By1 and Gray
(8) and Byl and Sinnott (9).
A total of eight tests was administered. Simple static balance was assessed with the subject standing on a
stable support surface with the feet in
a stable position (feet side by side),
the eyes open or blindfolded, and
the head still (tests 1 and 2) or turning (tests 3 and 4). Complex balance
was tested under two primary sensory
conditions: I) the somatosensory system destabilized by placing the feet
in an unstable, tandem romberg position (tests 5 and 6) or 2) the somatosensory system destablized by a single
foot stance (tests 7 and 8). In both
conditions, vestibular righting reactions were further challenged by removing vision with blindfolding (18).
The test series was administered in
the same order for each subject. Previous work indicated that the subjects
did not improve performance with
practice (8,9). Subjects with idiopathic scoliosis were tested unbraced.
The seven subjects who were wearing
braces had been instructed to wear
the brace 24 hours a day, but most
did not wear it to sleep at night or
when they were playing sports. Thus,
they were not unfamiliar with the
unbraced state.
The one-footed balance tests
were timed for 10 seconds and the
other six balance tests were timed for
30 seconds. The total testing time
took approximately 15 minutes per
subject and could be carried out in
the clinic during the subject's regular
physician visit or at home (controls).
During testing, the examiner kept
the arms open to surround and protect the subject but not to touch the
subject. The subject's response was
graded as pass or fail. The test was
noted as failed if a subject swayed
outside the base of support and

stepped off to the side, swayed into
the examiner's arms, or grabbed
onto a nearby object before the
timed test was completed.
Vibratory testing required a p
proximately 15 minutes per subject.
It was performed using an electronic
tuning fork, the Bio-Thesiometer
(Biomedical Instrument Company,
Newbury, CT) (26,27,45). This is an
electronic instrument that vibrates at
a constant frequency of 120 Hz. The
amplitude of the vibration can be
increased in proportion to the square
of the applied voltage. The 1.2cm
round vibrator button was placed on
a bony prominence by the examiner.
The voltage was slowly increased
from zero until the subject perceived
the vibration. Once the voltage was
recorded, it was converted into vibratory amplitude via the conversion
table provided by the manufacturer.
This instrument has been used for
vibratory testing in other studies of
patients with idiopathic scoliosis (45).
For vibratory testing, subjects
were seated on a table or a treatment
plinth located in a quiet room. The
subject's feet were allowed to swing
freely. The stimulator was placed on
the following bony prominences:
I) first metatarsal phalangeal joint
(right and left); 2) ulnar styloid
(right and left); and 3) the spinous
process of the seventh cervical vertebra. Three trials were performed at
each test site. Testing was initiated on
the right or left side based on random assignment. For each trial, the
voltage was slowly increased from
zero until the subject perceived the
vibration. This voltage was recorded.
To prevent bias during testing, neither the subjects nor the examiner
could see the voltage meter.
Variability in the measurement of
vibration thresholds has been reported by McInness et al (27). The
reliability (reproducibility) of the BioThesiometer measurements are impacted by a number of variables that
affect all sensory testing: I) difficulty
standardizing the contact pressure of
the vibrator; 2) subjectivity of per-

ceived thresholds by the subject;
3) reproducibility of the readings
from the meter; 4) steadiness of the
vibrator button during testing; 5) tissue damping on perceived threshold;
6) reproducibility of test site placement; and 7) subject attention to the
stimulus. Sensory testing can also be
confounded by subject attention as
well as the size, speed, and force of
the stimulus (41). However, there was
no good alternative to this test since
other measurements of position sense
are equally variable.

Research Design and Data Analysis
This was a descriptive study using
matched pairs. As the primary analysis, two families of dependent variables were tested: I) multiple vestibulo-spinal balance responses and
2) vibratory thresholds. The dependent variable for the balance tests was
the proportion of subjects passing
the test. The z test for proportional
differences was used to determine if
balance performance differed between controls and subjects with idiopathic scoliosis. No differe~ceswere
expected in the stable, static positions when the somatosensory input
was stable. The differences were expected in the complex, sensorychallenged tests, specifically when the
somatosensory system was unstable.
All tests for balance were two-tailed
and the critical value was set at p <
0.0125 to control for the experimentwise error of running four tests on
the same dependent variable. For
vibratory threshold, three test trials
were taken with the two most similar
measurements taken from each test
site selected for data analysis. The
measurements for the right and left
were combined for each site and
tested for significance between the
control and the idiopathic scoliosis
groups. Three paired Student t tests
were applied to measure the significance of differences in vibratory sensitivity. A two-tailed test was used with
the critical value set at p < 0.0167 to
control for multiple testing on the
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same dependent variable. In both
There were two general null hycases, it was felt to be more imporpotheses for the primary analysis:
A descriptive summary of the balI ) there will be no significant differtant to control for the Type I error
responses of all the subjects is
(rejecting the null hypothesis when it ences between healthy controls and
in Table 1. In the most minsubjects with idiopathic scoliosis on:
should have been accepted) even
conditions (stable
a) sensory-challenged balance tests or
though such control increases the
somatosensory input, with or without
6) vibratory thresholds. For the secrisk of a Type I1 error (accepting the
vision, and with or without head
ondary analyses, the null hypotheses
null hypothesis when it should have
turning), 100% of the subjects passed
were: 2) there will be no significant
been rejected).
the tests. However, on the complex
differences between those with modThe secondary data analysis fobalance tests, compared with conerate-severe curves and those with
cused on the differences in balance
trols, a significantly lower proportion
mild curves in terms of: a) the reand vibration threshold for those
subjects with idiopathic scoliosis
sensorychalwith moderatesevere curves (25" or
the complex, sensorychal6
more; 10 subjects) and those with
tests when vision and somatothreshold.
mild curves (less than 25"; 11 s u b
inputs were challenged simulwas:
jects). The 25" angle was selected as
The differences were
the critical curve because approxivibration
both for the tandem foot
mately 50% was below this curve anspine
< 0.0003) and the single
gulation and 50% was above this
(p < 0.0001). There
limit. The z test of proportional differences was applied to evaluate the
significance of differences in the balProportion Passing the Test
ance response between the two
Subjects With
groups, with the critical value set at
z Value (p)
p < 0.025 to control for multiple testScoliosis
( N = 24)
IN = 24)
ing in two of the complex sensorychallenged balance positions where
Simple static balance tests
T& 1 : Stable surface, stable feet
z = 0.0; not significant
at least some of the subjects passed
the test [test 5 (tandem romberg position of feet with head turning and
Test 2: Stable surface, stable feet
z = 0.0; not significant
eyes open) and the average of tests 7
(both feet together), eyes closed
and 8 (single foot stance, right and
Test 3: Stable surface, stable feet
z = 0.0; not significant
left, eyes closed)]. The Student t test
(both feet together), eyes open,
was applied to analyze the differences
head turning
in the vibratory threshold. All tests
were twetailed, with the critical value
Test 4: Stable surface, stable feet
z = 0.0; not significant
(both feet together), eyes
set at 0.0167 to control for multiple
closed, head turning
testing (three tests).
The tertiary analysis evaluated
Complex static balance tests
the relationship between vibratory
Test 5: Unstable foot position
(positioned in tandem), eyes
thresholds and complex balance reopen, head turning
sponses. The point biserial correlation coefficient was used to deterTest 6: Unstable foot position
mine the relationship between the
(positioned in tandem), eyes
vibratory threshold measured at the
closed, head turning
spine (C7) and whether the subject
Test 7: Unstable foot position
z = 2.05; not significant
passed or failed the four complex
(positioned on only right foot),
balance tests (two tandem romberg
eyes closed, head still
tests and the two one-footed balance
Test 8: Unstable foot position
tests). These correlations were tested
(positioned on only left foot),
for significance using the z test for a
eyes closed, head still
single correlation coeff~cientat p <
Critical value (tour comparisonsl: z = 2.17; p < 0.0125.
0.0125 to control for multiple testing
on the same dependent variable.
TABLE 1. Summary of the results of the balance tests.
JOSPT Volume 26 Number 2 August 1997






rmpwwn r.='"R (70)
S u b i j Wth Idiopathic S c o l i i
<2S0 cum
IN = 11)

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Complex balance teds
Stable surface, unstable feet
(positioned in tandem),
eyes open, head turning
(test 5)


Stable surface, unstable feet
(positioned in tandem),
eyes closed, head turning
(test 6)


Stable surface, unstable feet
(positioned on one foot,
right and left averaged),
eyes closed, head still
(tests 7 and 8)


(N = 10)

z Valw Siificancc


4.00;not significant


0;not significant


-1.45;not significant


Critical value ior two paired contrasts: t = 2.06; p 5 0.025.
Note: Three subjects did not have data in the chart on curve severity. One of the three passed test 5, and two did
not pass tests 7 and 8.

TABLE 2. Dynamic balance responses and severity of curve (degrees).

The vibratory test responses for
each group are summarized in Table
3. In both groups, there was a wide
range of variability in the measurement of vibratory threshold. There
were no significant differences between subjects with idiopathic scoliosis and the controls at any test site;
however, those with moderate-severe
scoliotic curves had significantly
higher vibratory thresholds than
those with mild curves (see Figure).
Thus, hypothesis l b must be ac-

were no significant differences between the balance responses in the
sensorychallenged conditions for
subjects with mild curves compared
to those with moderate to severe
curves. (Table 2). Thus, hypothesis
l a must be rejected and 2a accepted.
Subjects with idiopathic scoliosis did
not perform as well as controls on
complex, vestibularly challenged balance tests, but their performance was
not altered by the severity of the



(N = 24)

Site of measurement
Metatarsal phahgeal
Average rightneft
Ulnar styloid
Average rightneft
C7 spinous process

t value (p)






0.1 7


Not significant
Not significant
Not significant

0.1 6



0.1 7

Not significant
Not significant
Not significant
Not significant

< 0.0167 for three comparisons.

TABLE 3. Vibratory thresholds (micrometen)'.

(N = 24)


Critical value Student t test: t,, = 2.13; p

cepted and 2b rejected. There were
no significant differences in vibratory
threshold between subjects with scoliosis and the healthy controls, but
those with moderatesevere curves
had higher vibratory thresholds than
those with mild curves.
The correlations between the vibration threshold at the spine and
the complex balance responses are
summarized in Table 4. There were
no significant correlations between
performance on the complex balance

When the
somatosensory, visual,
and vestibular systems
were challenged
subjects with
idiopathic scoliosis
were more likely
to fail.
tests and vibratory threshold as measured at the seventh cervical vertebra.

In this study, both normal s u b
jects and those with idiopathic scoliosis were able to pass all of the simple,
static balance tests. When the somatosensory, visual, and vestibular systems
were challenged simultaneously, s u b
jects with idiopathic scoliosis were
more likely to fail the complex balance tests than age-matched controls.
Normal subjects and those with idiopathic scoliosis demonstrated similar
vibratory thresholds, but within the
group with idiopathic scoliosis, those
with more severe curves had higher
vibratory thresholds than those with
mild curves. There was no correlation
between performance on the comVolume 26 Number 2 August 1997 JOSPT



longitudinal studies measuring complex, sensorychallenged balance responses and position sense from the
onset of idiopathic scoliosis during
adolescence through adulthood.

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Balance Dysfunction and Scoliosis
The results of this study are similar to those reported by Yamada et al
(46), Sahlstrand and Petruson (35),
Sahlstrand and Lidstrom (36). Sahlstrand et al, (37,38), Herman and
MacEwen (18), By1 and Gray (9), and
Gregoric et al (15). These researchers reported that subjects with idiopathic scoliosis had difficulty passing
Less than 25 degrees
More than 25 degrees
the sensorychallenged balance tests,
but they performed as well as, if not
Curve Severlty
better, than controls on the simple
FIGURE. Vibratory threshold and severity of curve, patients with idiopathic scoliosis. Critical value, pair-wise
comparison of vibratory threshold by curve severity: !,= 2.37 (p < 0.0167).1 = Metacarpalphalangealjoint, static balance tests.
Adler et al (1) reported that subt = 3.542 (p < 0.0011; 1 = Ulnar styloid, t = 4.428 (p < 0.0002); = Cervical vertebra (7), t = 2.501 (p <
jects with idiopathic scoliosis had reduced body sway compared with normal
subjects across all tests used in
plex balance tests and vibratory
normal righting responses to gravity?
Interestingly, Adler et a1
3) Are balance problems a conse(1)
that subjects with scolioThese findings raise some interquence of structural spinal asymmetry
body sway than ageesting questions: I) Is it possible that
which persists, to some extent, even
However, this difthe structural asymmetry of the spine after a spinal fusion? and 4) Do probference
degrades the accuracy of joint posilems with balance predispose the
different than controls when predicttion sense as estimated by sensitivity
spine to idiopathic scoliosis or does
able anterior-posterior oscillations
to vibration? 2) Do patients with i d i e idiopathic scoliosis lead to problems
generated from the movement
pathic scoliosis have an underlying
in balance? The answers to these
support surface (eyes open or
vestibular imbalance that prevents
questions will only be provided from
closed). Further, subjects with progressive curves performed the balance
tests with significantly less body
Complex Balance Test
sway than those with nonprogressive
curves. Thus, Adler et al concluded
Test 5 ( N = 24): Stable support surface,
- 1.076
unstable feet (positioned in tandem),
that those with idiopathic scoliosis
eyes open, head turning
demonstrated more well-adapted
righting reactions than age-matched
Test 6 ( N = 24): Stable support surface,
unstable feet (positioned in tandem),
The findings by Adler et al were
eyes closed, head turning
different than what was observed in
Test 7 (N = 24): Stable support surface,
the study reported here. However,
unstable feet (positioned on only right
none of the balance conditions in
foot), eyes closed, head still
the Adler et al study (1) challenged
medial-lateral stability nor did they
Test 8 (N = 24): Stable support surface,
unstable feet (positioned on only left
challenge righting reactions when the
foot), eyes closed, head still
vestibular system, the somatosensory
system, and vision were perturbed
* All subjects rded.
NS = Not significant.
simultaneously. It is conceivable that
Critical value: t,, = t 2.24 (p < 0.0125).
mild perturbations of the somatosenTABLE 4. Correlation between vibration threshold and complex balance tests.
sory system with a predictable, consis-

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tently moving platform as reported
by Adler et al (1) were not sufficiently challenging to produce measureable differences between subject
groups. However, another interpretation of the findings might be that the
subjects had reduced balance reactions, demonstrating a resistance to
movement because they might meet
their limits of stability and lose control, similar to the protective rigidity
observed in a patient with vertigo
who avoids movement to protect
against becoming symptomatic (17,
The foot positions used in this
study (heel to toe and single foot)
tested medial/lateral forces on righting. Since scoliosis is a lateral deviation of the spine, it seemed logical to
challenge this directional component. However, the tandem romberg
foot position and the single foot
stance also stress position sensitivity
and stability of the ankle. Subjects
with a history of chronic ankle
sprains were excluded from the
study; however, those with pronated
feet were not specifically excluded
from either the control or the idiopathic scoliosis groups. It is conceivable that some of the medial/lateral
instability in balance could have been
attributed to foot pronation (20). On
the other hand, the destabilizing effects of pronated feet were present in
both the normal subjects as well as
those with idiopathic scoliosis. In future studies, this variable should be
Idiopathic scoliosis is classified as
one of the structural deformities of
the spine; however, if there are any
structural defects in the vertebral
bodies or the ribs, then the scoliosis
cannot be classified as idiopathic. In
other words, the spinal asymmetry
resulting from the lateral bending
and the rotation of the spine associated with scoliosis is not due to a
structural defect of the bones. The
question remains: does poor integrative vestibular balance increase the
risk for the development of spinal
alignment problems or is poor inte-

grative vestibular balance a consequence of scoliotic, spinal asymmetry? It is possible that structural
instability of the spine from scoliosis
could make postural righting against
gravity more difficult (eg., an increase in the amount of sway, a limitation in the cone of stability, a tendency to fall following a smaller than
normal perturbation or challenge). If
the spinal stability and asymmetry is
improved by a surgical fusion (6,14),
should balance responses improve or
could the postsurgical limitations in
flexibility and change in joint proprioception actually worsen balance?
These questions can only be answered if balance assessments were
done routinely as part of primary pediatric care, both before the onset of
idiopathic scoliosis, during the scoliosis observation period, during the
progression of the curve, and then
after surgical stabilization.
In a previous study, complex balance responses were more impaired
in the subjects with severe scoliotic
curvatures (8). In this current study,
the ability to pass the complex balance tests was slightly but not significantly worse in those with the more
severe curves. Thus, it is yet inconclusive whether subjects with idiopathic
scoliosis with problems of vestibular
imbalance are at a higher risk for
developing progressive spinal asymmetry. However, it is clear that all
individuals with vestibular imbalance
do not develop idiopathic scoliosis
and all of the patients with idiopathic
scoliosis do not have vestibular balance problems. Conceivably, prob
lems with vestibular imbalance could
increase the risk for developing progressive, idiopathic scoliosis in individuals with an autosomal recessive
gene for scoliosis (5). Similarly, other
physical factors such as muscle imbalance, muscle weakness, and hypermobility of the spine could also increase
the risk for developing clinical scoliosis in individuals who have the gene
for scoliosis as well as increase the
risk for curve progression in those

who have already been diagnosed
with idiopathic scoliosis.

Vibratory Sensation Threshold
This study did not find any significant differences in vibratory sensitivity in subjects with idiopathic scoliosis
compared with age-matched controls.
It is possible that the vibratory threshold does provide a very sensitive estimate of joint position sense. On the
other hand, those with more severe
curves had a significantly higher vibratory threshold than those with
mild curves. This either suggests that
joint position dysfunction is more
likely to be a problem in patients
with severe spinal curves or that the
sensitivity of the measurement of vibratory threshold is increased when
estimated in a population of patients
with significant spinal curvatures.
Wyatt and Barrack (45) and Barrack et a1 (4) reported that adoles
cents with idiopathic scoliosis were
more sensitive to vibratory sensation
on bony prominences of the upper
and lower extremities compared with
age-matched controls. They concluded there was a lesion in the posterior column pathway at a level
proximal to the thoracic cord, either
in the cervical cord or the brain
stem. Using the Bio-Thesiometer,
McInnes et a1 (27) reported that subjects with idiopathic scoliosis had significantly higher vibratory thresholds
(less sensitive) at the metacarpophalangeal joint than controls.
While the findings of Wyatt and
Barrack (45). Barrack et a1 (4), and
McInnes et a1 (27) seem contradictory, they both represent abnormal
responses which could interfere with
normal righting responses. The significant difference in vibratory
threshold for the subjects with mild
curves compared to those with moderate to severe curves suggests that
severe curves may be more likely to
alter joint position sense than mild
curves. However, if altered sensitivity
to vibration is a specific consequence
of severe spinal asymmetry, then it is
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not clear why the vibratory thresholds patients with idiopathic scoliosis have
As part of a conservative managewere also elevated in the extremities.
integrative vestibular balance p r o h
ment program, therapists should evalThis finding suggests that altered sen- lems. Whether these problems are a
uate postural righting reactions and
sitivity to vibration as an estimate of
result of stress from spinal asymmetry proprioception in patients with idioproprioception may be more general- or whether they represent a risk facpathic scoliosis. Dysfunction identified should be addressed in treatized in nature and not specific to the tor for developing a more severe
ment, consistent with recommended
spine. In order to determine if the
curve is yet unclear. However, theravestibular rehabilitation programs. It
sense of joint position is a risk factor
peutic exercises aimed at improving
would be important for therapists to
for the development of idiopathic
joint position sense and integrative
scoliosis or the progression of the
balance responses could improve pos- collaborate across sites to document
whether the integration of vestibular
curve severity in those with idiopathic tural righting reactions and possibly
scoliosis, then joint position sense
decrease the stress on the spine. Spe- exercises into traditional conservative
treatment programs improves poswould need to be monitored over the cific, repetitive, attended bombardtural righting reactions and miniment of the somatosensory and veslife span.
mizes the progression of spinal asymtibular systems may improve orienThe authors expected balance
metry and pain in patients with
tation in space. This approach to
and vibratory threshold to be correidiopathic scoliosis.
sensory stimulation is consistent with
lated since both factors could be the
the principles of neuroplasticity. Conconsequence of severe spinal asymtrolled sensory stimulation has been
metry. The lack of a correlation sugSUMMARY
effectively applied to the treatment of
gests that decreased balance and
This study provides evidence to
poor proprioception are independent patients with vestibular problems like
a correlation between balvertigo, dizziness, imbalance, and falls
risk factors in idiopathic scoliosis.
position sense, and idio(7,l l,l7,19-21,34,39).
particularly in s u b
Retrospective studies on vestibuStudy Constraints
and progressive
lar rehabilitation programs indicate
of whether the
The most important limitations
that 85% of patients with chronic
balance reof this study were that: I) it included
vestibular dysfunction gain partial
are consea small number of subjects; 2) data
relief of their symptoms and 30%
scoliwere not gathered longitudinally over may be completely cured following
time; 3) proprioception was meavestibular rehabilitation programs
ated and treated when present as
sured indirectly with vibration;
(21,34). Activities include dynamic
part of a conservative management
4) strength and flexibility were not
activities like swinging, rocking, turnprogram for patients with idiopathic
measured; and 5) a parametric twoing in circles, walking on unstable
way analysis of variance could not be
surfaces, head turning, and changing
done (because balance was measured of positions during attended condion a nominal scale). Thus, it was not
tions which are visually challenged.
possible to statistically confirm an
For patients with idiopathic scoliosis,
1 . Adler N, Bleck EE, Rinsky LA, Young
interaction between curve severity,
additional activities which challenge
W : Balance reactions and eye-hand covibratory threshold, and balance.
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4. Barrack RL, Wyatt MP, Whitecloud TS,
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thresholds to vibration and 2) some
gression and severity?
Moe's Textbook of Scoliosis and Other
JOSPT Volume 26 Number 2 August 1997

Journal of Orthopaedic & Sports Physical Therapy®
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Copyright © 1997 Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.



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