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ABSTRACT
COMPUTERIZED DYNAMIC POSTUROGRAPHY COMPARING THE BERTEC BALANCE ADVANTAGE™ AND NEUROCOM
SMART BALANCE MASTER® IN ASSESSING POSTURAL STABILITY IN HEALTHY ADULTS
Purpose: The purpose of this study is to establish the validity of postural
stability measures between a new computerized dynamic posturography (CDP)
system Bertec™ using an immersive virtual environment to the gold standard sway-
referencing of NeuroCom®. Methods: 50 healthy adults aged 20-69 years old were
tested on the 3 protocols for CDP: Sensory Organization Test (SOT), Motor Control
Test (MCT), and Adaptation Test (ADT). Results: Strong to moderate correlation
values between Bertec™ and NeuroCom® on the SOT's Conditions 1-6 and
Composite and MCT indicating good concurrent validity. Poor correlation values for
ADT toes up and toes down indicating poor concurrent validity. Condition 1, 4, 6 and
SOT composite equilibrium scores were significantly lower in Bertec™ MCT
composite latency scores were significantly longer and ADT toes up and toes down
sway energy scores were significantly higher on Bertec™. All scores indicated less
stability observed on the Bertec™ versus the NeuroCom® The largest clinically
important difference was found in Condition 4 on the SOT and the ADT. Conclusion:
CDP tests of SOT and MCT showed high levels of concurrent validity indicating that
both Bertec™ and NeuroCom® are valid measures of postural stability. With
somatosensory and vestibular ratio scores comparable, it gives clinicians confidence
both devices are reliable in measuring somatosensory and vestibular cues for balance.
Significantly lower vision ratio scores on Bertec™ as compared to NeuroCom®,
suggest the immersive virtual environment of Bertec™ may provide a more sensitive
analysis of visual input into postural stability.
Carolyn Bentley May 2017
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COMPUTERIZED DYNAMIC POSTUROGRAPHY COMPARING
THE BERTEC BALANCE ADVANTAGE™ AND NEUROCOM
SMART BALANCE MASTER® IN ASSESSING POSTURAL
STABILITY IN HEALTHY ADULTS
by
Carolyn Bentley
A project
submitted in partial
fulfillment of the requirements for the degree of
Doctor of Physical Therapy
in the Department of Physical Therapy
College of Health and Human Services
California State University, Fresno
May 2017
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APPROVED
For the Department of Physical Therapy:
We, the undersigned, certify that the project of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the doctoral degree. Carolyn Bentley
Project Author
Peggy Trueblood (Chair) Physical Therapy
Monica Rivera Physical Therapy
Nancy Wubenhorst Physical Therapy
For the University Graduate Committee:
Dean, Division of Graduate Studies
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AUTHORIZATION FOR REPRODUCTION
OF DOCTORAL PROJECT
X I grant permission for the reproduction of this project in part or in
its entirety without further authorization from me, on the
condition that the person or agency requesting reproduction
absorbs the cost and provides proper acknowledgment of
authorship.
Permission to reproduce this project in part or in its entirety must
be obtained from me.
Signature of project author:
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ACKNOWLEDGMENTS
I would like to thank my family including my mother Theresa and brothers
Derek and Kevin for all the support provided. I would also like to thank the Fresno
State Graduate Net Initiative Research Fellowship program for the workshops
provided as well as a travel opportunity. Lastly, I would like to thank my project
chairs for all their help in creating a positive learning environment including Dr.
Peggy Trueblood, Dr. Monica Rivera and Nancy Wubenhorst.
Thank you to everyone who has helped me these past 3 years in pursuing a
Doctor of Physical Therapy degree at California State University, Fresno.
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TABLE OF CONTENTS
Page
LIST OF TABLES ................................................................................................. vii
LIST OF FIGURES ............................................................................................... viii
INTRODUCTION .................................................................................................... 1
METHODS ............................................................................................................... 5
Participants and Enrollment .............................................................................. 5
Testing Procedures ............................................................................................ 5
Data Analysis .................................................................................................... 7
RESULTS ................................................................................................................. 8
Sensory Organization Test & Sensory Ratio Scores ......................................... 9
Motor Control Test .......................................................................................... 10
Adaptation Test ............................................................................................... 10
DISCUSSION ......................................................................................................... 12
Statistical Findings .......................................................................................... 12
Limitations ...................................................................................................... 18
Future Research ............................................................................................... 20
Conclusion ....................................................................................................... 22
REFERENCES ....................................................................................................... 23
TABLES ................................................................................................................. 28
FIGURES ............................................................................................................... 35
APPENDICES ........................................................................................................ 41
APPENDIX A: STANDARDIZED TESTING INSTRUCTIONS ........................ 42
APPENDIX B: CONDITIONS 1-6 OF THE SOT ................................................ 47
APPENDIX C: MOTOR CONTROL TEST.......................................................... 49
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vi vi
APPENDIX D: ADAPTATION TEST .................................................................. 51
APPENDIX E: HEALTH QUESTIONNAIRE ..................................................... 53
APPENDIX F: INFORMED CONSENT ............................................................... 56
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LIST OF TABLES
Page
Table 1: Subject Characteristics ............................................................................. 29
Table 2: Pearson's Correlation Coefficients for SOT, MCT & ADT ..................... 30
Table 3: Equilibrium Scores for SOT Conditions 1, 2, 3 and 4 across Age Groups ...................................................................................................... 31
Table 4: Equilibrium Scores for SOT Conditions 5, 6 and Composite Score Across Age Groups .................................................................................. 32
Table 5: Somatosensory, Vision, Vestibular & Preference Ratio Scores across Age Groups .............................................................................................. 33
Table 6: MCT Latency and ADT Toes Up & Down Trial 1 and 5 Sway Energy Difference Across Age Groups ................................................................ 34
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LIST OF FIGURES
Page
Figure 1: Bertec™ Balance AdvantageTM (a) and NeuroCom® Equitest (b) ........ 36
Figure 2: Pearson's Correlation coefficient for Bertec™ and NeuroCom® for SOT conditions 1-6 and SOT composite. ............................................... 36
Figure 3: SOT conditions 1-6, composite equilibrium score for all subjects ......... 37
Figure 4: SOT composite equilibrium score across age groups ............................. 37
Figure 5: MCT latency composite scores comparing age groups .......................... 38
Figure 6: MCT composite latency scores across age groups ................................. 38
Figure 7: ADT toes up & down sway energy for the mean difference between Trials 1 and 5 ..................................................................................... 39
Figure 8: ADT toes up sway energy across age groups ......................................... 39
Figure 9: ADT toes down sway energy across age groups .................................... 40
Figure 10: Condition 4 equilibrium scores for Trials 1-3. ..................................... 40
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INTRODUCTION
Balance or dizziness impairments are common in the adult population1. It
has been estimated that 40% of the population in the United States will experience
some form of balance or dizziness impairment over the course of a lifetime1.
Falling can be a direct consequence of dizziness and balance impairments
especially in people over 65 years of age compounded by other neurologic deficits
and chronic medical problems2,3. Falls are the leading cause of death and injury in
patients that are 65 years and older resulting in direct medical costs over $31
billion annually2,3. More than 2.8 million older adults are treated in the emergency
department for fall injuries each year4. Therefore, it is important to seek valid and
reliable postural control stability measures that identify individuals with functional
impairments and those that may be at increased risk for falls.
Postural stability is a person’s ability to correctly perceive their
environment through peripheral sensory systems and maintain their upright stance.
The brain relies on the sensory input from the somatosensory, visual and
vestibular systems in order to maintain the body's center of gravity over its base of
support. When these 3 sensory systems are affected they relay altered information
to the brain and the individual is unable to organize the sensory input correctly.
This results in postural instability with difficulty in controlling their body's sway
leading to falls and imbalance5,6. Postural instability has been shown to be a high
predicting factor of a patient’s fall risk in both computerized and non-
computerized measurements5,6. There are a multitude of reliable and valid methods
to subjectively and objectively measure postural stability.
Current postural control and fall risk assessment techniques include Berg
Balance test, Modified Clinical Test of Sensory Interaction and Balance
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(mCTSIB), Timed Up and Go, Functional Reach, among others7-10. Although
these tests are valid and easily conducted in the clinical setting, they have potential
drawbacks including variability in test performance, biases in the subjective nature
of the scoring system and decreased sensitivity to small changes11,12.
Computerized Dynamic Posturography (CDP) was developed to diminish these
drawbacks by providing a consistent quantitative postural control assessment11,12.
Computerized Dynamic Posturography is a computerized device used to
quantify an individual’s postural control through the movement of the body’s
center of gravity using dynamometric platforms12. It is an integral component in
the diagnostic workup of balance impairments to help identify the underlying
sensory and motor control impairments12,13. Developed in the 1980s, NeuroCom®
International provided the EquiTest system involving the Sensory Organization
test (SOT), Motor Control test (MCT) and Adaptation test (ADT)14 (Figure 1).
This system is the gold-standard assessment technique used to quantify and
differentiate the sensory, motor, and central adaptive impairments in balance
control through postural sway-referencing. Sway-referencing refers to tilting of the
support surface and/or visual surround to directly follow the patient’s anterior to
posterior body sway. This effectively eliminates the subject’s use of visual and
proprioceptive information for orientation thereby creating a sensory conflict
situation. This is performed to quantify vestibular balance control and to stress the
adaptive response of the central nervous system in order to diagnostically
determine balance impairments15.
NeuroCom® has been extensively studied utilizing the SOT which
performs a set of 6 postural sway examinations identifying visual, balance and
vestibular impairments. A SOT composite score is then compiled, providing a
baseline objective measurement of postural stability. The SOT composite score
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has been found to be a valid assessment in healthy older adults, as well as a wide
array of pathologies peripheral neuropathy, people with Parkinson's Disease,
Multiple Sclerosis among other neurological and musculoskeletal disorders.16-18
More recently the Bertec Balance AdvantageTM a dynamic CDP utilizing
an immersive virtual environment in a specially modified dome was created to
objectively identify postural instability (Figure 1). The incorporation of the static
and dynamic properties of the optic surround, a series of concentric ovals leading
to a grey oval shape creates the perception of a tunnel with no definable end or
horizon. This has the ability to enhance the visual stimulus for postural control in
order to evaluate and provide interventions that closely reflect conditions found in
the physical world19,20. The computer interactive display technology of Bertec™
as opposed to sway-referencing, creates an environment where the subjects will be
completely engaged in a virtual surround, therefore their responses to the images
will be similar to those in the real world. This strong immersive environment the
subject experiences is needed in order to engage and interact with the higher level
processes of the central nervous system that influence postural control19,21. As
complex visual environments are difficult to reproduce in the clinical setting, the
immersive virtual environment creates a real life scenario to accurately identify
impairments of balance and provide for enhanced balance training.
While sway-referencing CDP has been studied extensively with balance
assessment, there are limited studies available incorporating the effectiveness of
assessing postural control in an immersive virtual environment. Furthermore, there
are no published quantitative comparisons between Bertec™ and NeuroCom®20.
Given these factors, this study examines Bertec™ CDP system incorporating an
immersive virtual environment projected in a specially modified dome and
comparing this data with the sway-referencing used by EquiTest systems
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developed by NeuroCom®Incorporated. The purpose of this study is to validate
the ability of Bertec Balance AdvantageTM to assess postural control as compared
to the gold-standard NeuroCom® Equitest. The null hypothesis is that there will
be no differences between the immersive virtual environment of Bertec™ and
sway-referencing of NeuroCom® in any of the 6 conditions. The alternative
hypothesis is that the 2 devices will be comparable for all tests with the exception
of Conditions 3 and 6 of the SOT, when visual conflict is utilized. During
Conditions 3 and 6 of the SOT, the alternative hypothesis is that the equilibrium
scores will be significantly lower in the Bertec™ as compared to the NeuroCom®
due to the stronger visual stimulus of an immersive virtual environment in
Bertec™ in the 2 conditions. The final alternative hypothesis is that the MCT and
ADT toes up and toes down will be comparable between Bertec™ and
NeuroCom® as the visual surround is static.
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METHODS
Participants and Enrollment
Fifty healthy adults (33 females and 17 males) were voluntarily recruited
through flyers, emails and oral communication. The subjects were stratified into 5
age groups with an N of 10 for each group. Group 1 (20-29 years), group 2 (30-39
years), group 3 (40-49 years), group 4 (50-59 years) and group 5 (60-69 years)
(Table 1).
The study was approved by the California State University, Fresno
Committee on the Protection of Human Subjects. An informed consent, a Medical
Research Patient’s Bill of Rights and a subjective history were obtained from all
subjects.
Inclusion criteria were healthy adults aged 20-69 years old with the
exclusion criteria of: 1) dizziness, inner ear, or other balance or vestibular
disorder; 2) closed or open head injury resulting in any neurological symptoms; 3)
cervical injury; 4) assistive device use or inability to stand for 20 minutes; 5)
visual impairment; 6) concussion with complaints of headache and/or other
symptoms; 7) diabetes; 8) peripheral vascular disease; 9) any significant lower
extremity joint disorder or injury that would interfere with balance, and/or 10)
persistent motion sickness/sensitivity.
If the subject did not respond to these criteria, he or she was eligible for the
study. The details of the study were described, written informed consent was
obtained and subjects were free to withdraw from the study at any time.
Testing Procedures
The subjects were provided standardized instructions prior to the start of
each test condition (Appendix A). Testing was completed in a quiet room, the
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subject was fit with an appropriate-sized restraining harness and the investigator
remained in close proximity in case they lost their balance. The subject was tested
barefoot without shoes and socks. The investigator aligned the subject’s feet
according to predetermine guidelines22. The malleoli were aligned with the
horizontal line on the force plate and the lateral calcaneus was aligned with the
size line according to the subject’s height. The angular alignments of the feet were
positioned for patient comfort. Measurements were taken of the feet placement
from the calcaneus to the end of the platform, to ensure correct alignment of the
feet if a fall were to occur. Correct foot alignment was monitored and maintained
throughout testing.
The subject underwent testing on the 2 computerized systems, each using 3
different tests to measure balance: SOT, MCT and ADT. The subject first
performed testing on the Bertec™ system (Figure 1) by Researcher 1, followed by
a 15 minute rest, then NeuroCom® (Figure 1) testing by Researcher 2. Researcher
1 completed all Bertec™ testing, and Researcher 2 completed all NeuroCom®
testing.
The Sensory Organization Test (SOT) measured the subject's center of
gravity during 3 trials of 6 conditions. Condition 1: eyes open, fixed environment.
Condition 2: eyes closed in fixed environment. Condition 3: eyes open, fixed
platform, moving visual environment. Condition 4: eyes open, moving platform,
fixed visual environment. Condition 5: eyes closed, moving platform, fixed visual
environment. Condition 6: eyes open, moving platform and visual environment
(Appendix B).
Sensory analysis ratios are calculations provided through the 6 conditions
of the SOT. Somatosensory analysis ratio is Condition 2 divided by Condition 1.
Visual analysis ratio is Condition 4 divided by Condition 1. Vestibular analysis
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ratio is Condition 5 divided by Condition 1. Preference analysis ratio is sum of
Condition 3 and 6 divided by the sum of Condition 2 and 5.
The Motor Control Test (MCT) measured the subject’s reaction time in 3
trials of 6 conditions. Condition 1: small translation forward. Condition 2: medium
translation forward. Condition 3: large translation forward. Condition 4: small
transition backward. Condition 5: medium transition backward. Condition 6: large
transition backward. Data was only analyzed for the MCT composite of medium
and large translations (Appendix C).
The Adaptation Test (ADT) measured the subject’s center of gravity and
reaction time in 5 trials of 2 conditions. Condition 1: Platform moved in toes up
direction. Condition 2: platform moved in toes down direction. Data were
analyzed for the difference of trial 1 and 5 for both toes up and toes down
(Appendix D).
Data Analysis
Data was entered in the IBM SPSS Version 24 System. Pearson Product
Correlations (r) were used to determine the strength of the relationship of Bertec™
and NeuroCom®. An r-value larger than .75 was considered good, .50 - .75 as
moderate and less than .50 as a poor correlation23. Repeated measures analysis of
variance (ANOVA) were used to analyze the differences between Bertec™ and
NeuroCom®. Data was analyzed for all 50 subjects and across each age group
including the composite and average of 3 trials of the 6 conditions of the SOT,
sensory ratio scores, composite MCT scores and ADT differences of trials 1 and 5.
A 2 x 5 factor analysis, 2-way utilized for comparison of devices and 5-way for
differences of age groups. A p-value less than .05 was considered significant.
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RESULTS
A total of 56 subjects were tested, however, 6 subjects were excluded from
our analysis due to not meeting the inclusion criteria. The 6 subjects that were
excluded had 1) a history of a recent concussion with residual symptoms (2/6); 2)
ACL surgical procedure (2/6); 3) cervical fusion with metal plate in the ankle (1/6)
and 4) a prior non-specified lower back surgery (1/6). One subject included in the
40-49 years old had a concussion 10 years prior due to skiing injury however they
were not excluded as they had no residual symptoms nor other significant medical
history. Two subjects in the 30-39 years old had prior knee arthroscopy due to
meniscal involvement, however, the surgery was noninvasive and occurred more
than 3 years prior with no subjective knee complaints and therefore not excluded.
Although 17/50 subjects had reported visual impairments they were all corrected
with glasses. 10/50 subjects indicated they had motion sickness sometime during
their life, however it was not considered significant to interfere with testing as
none of them had symptoms. 23/50 subjects reported a prior lower extremity (LE)
injury and/or surgical intervention including stress fracture, knee arthroscopy,
hysterectomy, caesarian section and appendectomy, however they were not
considered significant. 18/50 subjects reported use of over the counter and/or
prescription drugs. Subjects ranged from taking 0 to 4 medications with 1 person
on 4 prescribed medications. The over the counter drugs included vitamins,
analgesics and allergy medications. Prescription medications include
bronchodilators, gastrointestinal disorders, thyroid involvement, cholesterol,
hypertension, diuretics and hormonal treatment. Dosages and medication time
lines of the subjects were unknown, however it was considered not significant to
interfere with testing as most were over the counter type medications and there
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were no reports of any symptoms of dizziness or impaired balance prior or during
testing. Table 1 describes the characteristics of the 50 subjects included for the
analysis. See Appendix E for the health questionnaire used in the study, and
Appendix F for the informed consent.
Sensory Organization Test & Sensory Ratio Scores
There was a strong positive correlation between Bertec™ and NeuroCom®
SOT Composite scores (r=.81, N=50, p<.001). Conditions 2, 4, 5 and 6 were
moderately correlated (r=.65, p<.001; r=.57, p<.001; r=.61, p<.001; r=.65, p<.001
respectively), whereas, Conditions 1 and 3 were poorly correlated (r=.34, p<.02;
r=.40, p<.001; respectively) (Figure 2) Vision and vestibular ratio scores were
moderately correlated (r=.53, p<.001; r=.60, p<.001; respectively). Somatosensory
and preference ratio scores were poorly correlated (r=.34, p<.02; r=.09, p<.56;
respectively) (Table 2).
There was a significantly lower mean average in the SOT Composite
equilibrium (EQ) score for Bertec™ as compared to NeuroCom® for all subjects
(75.36 ± 6.05, 79.28 ± 5.31 respectively, p<.001) (Figure 3). When individual
conditions were compared, EQ scores were significantly lower on Bertec™ as
compared to the NeuroCom® in Conditions 1,4 and 6 (mean differences were 2-13
points), with Condition 4 showing the greatest mean difference (mean EQ score
71.92 vs 84.89, for Bertec™ and NeuroCom® respectively). Condition 2 was
slightly higher on the Bertec™ (92.08 and 91.15, p<.001) and Condition 3 and 5
were not significantly different (p<.61, p<.44 respectively) (Table 3 and 4).
Consistent with these findings the calculated visual and preferences ratio scores
were also significantly lower (mean EQ score difference of 12.31 and 4.95
respectively). The somatosensory ratio score was slightly higher on the Bertec™
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as compared to the NeuroCom® (mean EQ score 99.40 vs 96.38, p<.001).
Whereas, the vestibular ratio score was not significantly different between
Bertec™ and NeuroCom® (p<.07) (Table 5).
The significant differences found between Bertec™ and NeuroCom® on
SOT conditions, composite and sensory ratio scores were found to not differ
between age groups. The p-value for between-subject age-groups were greater
than .05 for all the above testing scenarios indicating no significant difference
(Figure 4). Therefore the post-hoc Tukey Honest Significant Difference (HSD)
was not analyzed.
Motor Control Test
The MCT composite latency score had a good correlation between devices
(r=0.67, p<.001) (Table 2). There was a significantly slower latency on the MCT
composite score on Bertec™ as compared to the NeuroCom® for all subjects
(mean difference of 3.2 msec p<.001) (Figure 5, Table 6). The p-value for within-
systems was found to be significant with a p-value of .004. The between-subjects
age groups were not significant with a p-value of .083. However, there was an
interaction for system and age group (p=.046) indicating the difference in devices
was dependent on age groups (Figure 6, Table 5). Overall larger mean differences
were found in the younger groups (age 20-29 and 30-39) compared to the older
groups (age 50-59 and 60-69) (6-7 msec vs 1-3 msec).
Adaptation Test
There was a poor correlation between ADT toes up and toes down Trial 1
and 5 difference between Bertec™ and NeuroCom® (r =.08, p<.57; r=.09, p<.54)
(Table 2). The toes up average differences of Trial 1 and 5, Bertec™ sway energy
differed by 21.84 while NeuroCom® differed by 8.66. In toes down average
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differences of Trial 1 and 5, Bertec sway energy differed by 24.90 while
NeuroCom® differed by 9.90 (Figure 7, Table 6). There was a significantly
greater sway energy score indicating less stability in the Trial 1 and 5 difference of
ADT toes up and toes down sway energy scores for Bertec™ as compared to
NeuroCom® for all subjects (Sway energy scores differed by 13.18 and 15.00
points, p<.001,p <.00; respectively). The toes up between-subjects age groups and
the interaction between device and age group had a p-value of >.05 indicating the
differences in devices was not dependent on the 5 age groups (Figure 8). The toes
down between age groups p-value of .719 indicates there is no difference in age
groups. (Figure 9, Table 5).
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DISCUSSION
Statistical Findings
The Bertec Balance AdvantageTM system has high concurrent validity in
association with the gold-standard NeuroCom® Equitest. Both the MCT and SOT
composite and conditions 2, 4, 5 and 6 exhibited moderate to good correlation
(Figure 2). ADT toes up and toes down test had poor correlations and therefore
determined to have poor concurrent validity. The strong to moderate correlations
of SOT and MCT indicate that both the Bertec™ and NeuroCom® are comparable
and valid measures of postural stability.
A clinical important difference is indicated by a greater than 8 point change
in the SOT Composite, greater than a 5 point change in SOT Conditions 1-2, a
greater than 10 point change in Conditions 3-6, a greater than 10 msec difference
in MCT Composite and a greater than 10 sway energy in ADT24. This study was
able to accept parts of the null hypothesis indicating there is a clinical difference
between the 2 CDP systems of Bertec™ and NeuroCom®. Condition 3 was not
statistically nor clinically different and Condition 6 not clinically different,
rejecting the alternative hypothesis that those conditions with a dynamic
immersive virtual environment in Bertec would show the greatest differences. The
alternative hypothesis indicating MCT was comparable between devices was
accepted as the 3.2 msec difference is not clinically relevant. The alternative
hypothesis indicating ADT was comparable between devices was rejected as there
were large statistical differences between the 2 systems with Bertec™ having
larger sway energy differences, suggesting less stability. This prospective study
and results was able to add to the psychometrics of these devices.
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Although the CDP devices exhibited statistically significant differences in
SOT composite, Conditions 1, 2, 4 and 6, MCT the differences were very small
and therefore the clinical interpretation would still be the same for each device.
The only clinical significant difference was found in Condition 4 and the visual
ratio score of the SOT and ADT toes up and toes down.
These results do not support the hypothesis that the immersive virtual
environment of Bertec™ provides a differing balance analysis than the sway-
referencing system of NeuroCom® during Conditions 3 and 6. Bertec™
equilibrium means are similar to NeuroCom® in analyzing vestibular and
somatosensory cues for balance but differ when analyzing visual cues. It can be
proposed that Bertec™ is comparable to NeuroCom® in analyzing vestibular and
somatosensory postural control but may be able to detect more subtle postural
abnormalities especially those related to visually sensitive deficits.
Sensory Organization Test
Overall the SOT composite scores were considered not clinically relevant
as Bertec™ had a score of only 4 points lower than NeuroCom®, this was found
to be consistent across all age groups (Figure 4). Wrisley et al. found that a
composite score of 8 points or greater would indicate change from rehabilitation24.
This concludes that the SOT composite scores are comparable between both
devices.
Conditions 1 and 2 are baseline measurements of static standing of eyes
open and eyes closed. Both of these conditions only differed by 1-2 points
indicating no clinically significant findings. This is important to conclude that both
devices are comparable in baseline measurements of postural control.
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The lower value on Condition 3 in the Bertec™ was not statistically
significant compared to NeuroCom®. To further clarify, Condition 3 provides a
conflicting visual stimulus in which the individual has to rely on their
somatosensory input. In a sensory weighted environment with a stable surface, the
normal individual relies 70% on their somatosensory input, 20% on vestibular and
10% on vision25. Due to this very high somatosensory input and low visual input,
both the Bertec™ and NeuroCom® produce similar results25. Therefore these
findings suggest the immersive virtual environment provided in the Bertec™ is
comparable to the sway referencing in NeuroCom®.
The greatest change was observed between Bertec™ and NeuroCom® was
during Condition 4 (71.92 vs 84.89 mean EQ scores). Condition 4 is eyes open
dynamic support surface where an individual is unable to use their somatosensory
system and needs to rely on vision for balance. Initially looking at the 3 trials of
Condition 4, subjects scored on average 21 points lower on Bertec™ for Trial 1,
while Trial 2 and 3 only differed by 11 and 7 points. To determine if the difference
seen in Condition 4 is due to the lower score on Trial 1 score as subjects need a
period to learn and adapt, the average of Trials 2 and 3 were analyzed. When
comparing the average of Trials 2 and 3, Bertec™ continued to be statistically
significantly lower (p<.05) by 9 points (Figure 6). This indicates that although
there was a large disparity on Trial 1, it did not affect the overall equilibrium score
of Condition 4. Another explanation for the increase challenge during Condition 4
could be that Bertec™, as compared to NeuroCom® provides no compensatory
visual strategy. For example, there is no visual cue in the Bertec™ since it is an
immersive virtual environment, whereas in the NeuroCom®, individuals can
reference to the horizon and images in the scene, the colorful scenario and/or the
computer monitor. Therefore, people with visual impairments in Condition 4
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would more likely be identified using the Bertec™ as opposed to NeuroCom®.
Although both devices provide different visual conflicts depending on the
surround there are no significant differences between devices in assessing
vestibular cues for balance.
Condition 5 has a dynamic support and eyes closed therefore eliminating
the immersive virtual environment. As there is no visual stimulus to provoke the
individual, this tests the use of the vestibular system. It has been previously shown
in people susceptible to seasickness had poor results in Condition 5 and vestibular
ratio scores, indicating they may be more dependent on somatosensory and visual
input to maintain balance26. As both devices are comparable in analyzing postural
cues, with the more challenging visual environment in Bertec™ it may have
greater accuracy at identifying persons with motion sensitivity or more subtle
visual dependency impairments. As both devices are similar in Condition 5, this
can conclude that Bertec and Neurocom are comparable in assessing vestibular
cues for postural control.
Although Condition 6 was significantly lower in the Bertec™, the mean
differences was relatively small (61.39 vs 67.05 mean EQ scores). Condition 6
eyes open dynamic support and surround was considered statistically different
between the devices but not clinically different as they only differed by 6 points.
This condition aims to test the preference of sensory system use by providing
altering visual and somatosensory cues. Preference indicates the amount to which
the subject relies on visual information to maintain balance even if conflicting
visual cues are provided27. The Condition 6 findings help to conclude that the
immersive virtual environment of Bertec seems to be comparable to sway-
referencing on NeuroCom®.
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Sensory Ratio Scores
The somatosensory ratio is a ratio of Condition 2 to 1 indicating no clinical
difference as they only differed by 3 points (99.40 vs 96.38 EQ). This is consistent
with Condition 2 and 1 equilibrium scores and helps to conclude the devices are
comparable in assessment of somatosensory cues.
The contrast in the device's visual array coincides with the visual ratio score
large difference of 12 points. Visual ratio score is the ratio of Condition 4 to 1 and
found to be clinically lower on Bertec™ (77.42 vs 89.73 mean EQ scores). This
coincides with Condition 4 indicating Bertec may be more sensitive in assessing
visual cues for balance.
The vestibular ratio score of Condition 5 to 1 also was not statistically and
not clinically different agreeing with the Condition 5 results (71.16 vs 68.71 EQ).
This finding is important as clinicians can be confident the 2 posturography
systems are similar in assessing vestibular cues for postural control.
The preference ratio between the devices differed by 5 points and
determined to not be clinically relevant as they differed by less than 10 points
(96.50 vs 101.45 EQ scores). This is a calculated ratio comparing conditions 3
and 6 to 2 and 5 which was also statistically different (p<0.05). This coincides
with the differences in equilibrium scores Condition 6 on the 2 devices as not
clinically relevant.
Motor Control Test
The Motor Control test (MCT) provides a composite score utilizing the
medium and large forward and backward translations. This attempts to mimic a
real-life environment by assessing how quickly a subject can recover from
unexpected external perturbations. The composite scores were strongly correlated
between Bertec™ and NeuroCom® for both forward and backward translations.
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The MCT latency scores were statistically slower on Bertec™ for both
forward and backward perturbations and the composite score had an insignificant
clinical change of 3.2 msec as it is less than a 10 msec difference (Figure 7). This
significant difference can be due to the higher sampling rate of Bertec™ at 1000
Hz as compared to 100 Hz on NeuroCom®28,29. As NeuroCom® samples at a 10
msec resolution, and only valid up to a 10 msec difference. It was also found that
individuals with bilateral vestibular loss had normal MCT latencies and it was not
influenced by vision30. This supports the immersive virtual environment of
Bertec™ does not influence the MCT results and we can conclude this test is
comparable between devices.
Adaptation Test
The Adaptation test (ADT) examines a patient’s ability to adapt and sustain
proper balance with minimal sway when exposed to equivalent surface
irregularities. A normal response involves the subject expending a decreasing
effort to return to the center of gravity following subsequent rapid changes to the
surface secondary to adaptation. This is measured by the amount of anterior-
posterior sway after a toes up and toes down perturbation, referred to as sway
energy.
The poor correlation values provides poor concurrent validity, indicating
both systems are poorly comparable in assessing the ability to adapt. The
significantly higher average sway energy scores on Bertec™ as compared to the
NeuroCom® for both toes up and toes down suggests less stability. This
significant difference can be due to the higher sampling rate of Bertec™ at 1000
Hz as compared to 100 Hz on NeuroCom®28,29. As NeuroCom® samples at a 10
point resolution, and only valid up to a 10 point difference, the ADT scores
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difference of 13.18 and 15 sway energy scores indicate a large clinically different
results. While the platform is moving 5 times in 1 direction there are many factors
influencing the results including reliance on visual cues of which the Bertec™
does not provide, ankle ROM, strength and biomechanical alignment. In the 50
subjects utilized 48% had a form of musculoskeletal involvement, of which
Bertec's™ higher sampling rate may be more sensitive to pick up subtle
impairments. It is important for this test to have concurrent validity as a decrease
performance in the toes up direction has a direct correlation into the frequency of
falls31.
Limitations
This current study had several limitations. The 50 person overall sample
size is effective, however 10 in each group is considered a small sample size. As
the smaller sample size creates a bias this can alter the results when comparing
between the 5 age groups.
Another limitation was the testing procedure. Subjects were recruited
through a sample of convenience and were tested on the Bertec™ prior to the
NeuroCom® introducing a possible order bias and a learning effect. As subjects
had better stability on all tests on NeuroCom®, this could possibly be due to a
learning effect as it is no longer a novel experience (Figure 1). However a one-
sample t-test comparing published normative data for the SOT Composite using
the NeuroCom® were compared to our results. The results suggests our subject’s
SOT Composite scores were not affected by the previous tests on the Bertec™
(p<.810) which may eliminate the effect of testing order bias as a factor29. Also the
largest difference was found in Condition 4, a study by Wrisley et al. found that
repeated administration of the SOT had significant learning effects in Condition 4,
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however if you look at the raw equilibrium score of Condition 4 from session 1 to
2 there was only a 1.5 point increase24. The large difference of 12 points on
Condition 4 can help eliminate the testing order bias and indicates a true
difference between devices.
Although both researchers were not blinded, it was attempted to eliminate
subjective bias and/or tester scoring differences by using one researcher per
device. CDP aids in eliminating this bias by providing good test-retest reliability
and minimizes inter-rater variability11,12.
Another possible limitation is the variability of subject characteristics in our
sample. Overall 56 subjects were tested, 50 of which made the inclusion criteria. 6
subjects were excluded due to not meeting our inclusion criteria. Of the 50
subjects included, 33 were female and 17 were male, age range of 24-69 years old
with an average age of 44 years old. 7 out of 10 60-69 year olds were on at least 1
prescribed medication. There was a wide range of medications listed some of
which have the possible side effects of imbalance and dizziness. It is difficult to
find elder adults with no medications as 87.7% of community-dwelling adults
aged 62-85 years old are on at least 1 medication32. To minimize this effect we
ensured each subject did not have any subjective complaints of dizziness from any
of their medications or throughout testing. Another confounding factor was 24 out
of 50 subjects reported prior surgeries. Surgeries were considered benign and
included appendectomy, caesarian section, wisdom teeth removal, face lift,
tonsillectomy, cholecystectomy, shoulder arthroscopy and hysterectomy. These
surgeries were deemed to not affect the lower extremities nor balance and were
performed a minimum of a year prior with no complaints the day of testing. 13
subjects reported motion sickness which included air, sea, car and motion. None of
these subjects reported any sickness throughout testing on both machines and
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therefore were not excluded. People with motion sensitivity have more difficulty
using vision for balance and could possibly be an explanation for people having
more difficulty with Condition 4. However, when we compared subjects with and
without a report of motion sensitivity there was no significant difference in the
equilibrium scores on Condition 4 for Bertec™ or NeuroCom®. 18 subjects had
reported visual impairments that were all corrected with glasses. From the variety
of subjects although considered healthy as they met the inclusion criteria can pose
a limitation to the collected data (Table 1).
Future Research
This prospective study helped to add to the psychometrics by determining
concurrent validity and correlation between the Bertec™ and NeuroCom® CDP
analysis. Clinicians can be confident when performing CDP in the new Bertec™
system, as test results are comparable to that found with the NeuroCom® Equitest
system. Normative values for Bertec™ are reported in a separate paper. Future
research using the Bertec™ with patient populations will be important to further
identify the usefulness of this system for testing postural stability.
The gold-standard NeuroCom® has been extensively used to detect balance
deficits, and help to assess abnormal conditions. It is also used in the treatment of
vestibular rehabilitation, traumatic brain injury including a sports-related
concussion and neurological diseases including multiple sclerosis and Parkinson's
disease16,18. In contrast, Bertec'sTM spherical dome immerses the subject and
provides a visually provoking environment. Similar to this dome, it been shown
people with mal de debarquement syndrome can significantly improve their
function by utilizing an optokinetic stimulator to readapt the vestibulo-ocular
reflex33. This prior knowledge and the findings of this study indicate that Bertec™
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may be most sensitive in detecting postural instability and more specifically visual
cues for balance. Future research needs to be conducted on Bertec'sTM ability to
detect subtle postural changes. One day post-concussive subjects demonstrated a
decline in postural stability using the NeuroCom® including a significant decline
in SOT composite score, visual and vestibular ratio scores34. With Bertec™ being
comparable in vestibular ratio scores but more sensitive in assessing visual ratio
scores with Condition 4, future research needs to determine if the immersive
visual environment is more sensitive for return-to-play assessment post-
concussion. As a concussion can affect both visual and vestibular inputs, it was
suggested that vision may play an important role in weakening the vestibulo-
ocular reflex and influence an individual's balance and vestibular system34,35. It is
important to further determine how individuals with visual impairments can
impact vestibular balance and develop improved fall prevention strategies for
those with inadequate visual inputs.
As this research helps to add to the current literature of the effectiveness
and increased sensitivity of an optic environment, future research should continue
to determine treatment options and its advantages. Research should be towards a
more clinical and treatment relevance by determining if Bertec™ can differentiate
between fallers and non-fallers to better determine the magnitude of a person's fall
risk. As individuals age they rely more on their visual environment, therefore it
will be important for future research to determine the sensitivity and specificity of
the quality of visual input on balance in the elderly population.
The findings of this study help to determine the concurrent validity of
Bertec™, it is now important to determine the predictive validity. Predictive
validity is important to establish to determine if the Bertec™ is valid day-to-day in
order to utilize it for pre and post-test intervention measures. As the CDP devices
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and NeuroCom® provides extensive objective data it helps to reduce the bias of
low inter and intra rater reliability. Future research can establish more
psychometrics including inter and intra-rater reliability.
Conclusion
The Bertec™ and NeuroCom® composite test scores were correlated for
SOT, MCT and during CDP assessment in healthy adults aged 20-69 years old.
Overall, the Bertec™ system was more challenging for subjects during all 3 CDP
tests, however vestibular, somatosensory and preference ratio scores were
comparable between the 2 systems, as there were no clinical differences. This
concludes that Bertec™ and NeuroCom® are valid measures of balance giving
clinicians confidence they are comparable for postural control measures. However,
visual ratio scores were significantly lower when tested with the Bertec™ system.
This could prove that Bertec™ may provide a more sensitive test for subjects with
poor use of vision during balance such as people with motion sensitivity or post
concussion or mild TBI.
Page 34
REFERENCES
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posturography BR. Clin Neurophysiol. 2008 Nov; 119(11):2424-36.
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12. Mancini M, Horak FB. The relevance of clinical balance assessment tools
to differentiate balance deficits. Eur J Phys Rehab Med. 2010;46(2):239-
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13. Faraldo-Garcia A, Santos-Perez S, Crujeiras R, Labella-Caballero T, &
Soto-Varela A. Comparative study of computerized dynamic posturography
and the SwayStar system in healthy subjects. Acta Oto-Laryngologica.
2012; 132: 271-276.
14. Ferber-Viart C, Ionescu E, Morlet T, Froehlich P, & Dubreuil C. Balance in
healthy individuals assessed with Equitest: Maturation and normative data
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1041-1046.
15. Computerized Dynamic Posturography. NatusR Balance & Mobility.
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dynamic-posturography/cdp-protocols/. Accessed October 11, 2016.
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et al. (2005) Bilateral subthalamic nucleus stimulation improves balance
control in Parkinson's disease. J Neurol Neurosurg Psychiatry 76(6): 780–
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17. Reid VA, Adbulhadi H, Black KR, Kerrigan C, Cros D (2002) Using
posturography to detect unsteadiness in 13 patients with peripheral
neuropathy: a pilot study. Neurol Clin Neurophysiol 2002 (4) 2–8
18. Whitney, S. L., Marchetti, G. F., et al. (2006). "The relationship between
falls history and computerized dynamic posturography in persons with
balance and vestibular disorders." Arch Phys Med Rehab. 87(3): 402-407.
19. Keshner E, & Kenyon R. Postural and spatial orientation driven by virtual
reality. Stud Health Technol Inform. 2009; 145: 209-228.
20. Pickerill M & Harter R. Validity and Reliability of Limits of Stability
Testing: A Comparison of 2 Postural Stability Evaluation Devices. J Athl
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21. Sadowski W, Stanney K. Prescence in Virtual Environments. Handbook of
Virtual Enviornments: Design, Implementation and Applications. London:
Lawrence Erlbaum Associates, Inc; 2002; 791-806.
22. Bertec Workbook Program Documentation. 2014.
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23. Portney L, Watkins M. Foundations of Clinical Research: Applications to
Practice. Upper Saddle River, N.J: Pearson/Prentice Hall; 2009.
24. Wrisley, D. M., Stephens, M. J., et al. (2007). "Learning effects of
repetitive administrations of the sensory organization test in healthy young
adults." Arch Phys Med Rehab. 88(8): 1049-1054
25. Peterka, R. and P. Loughlin (2004). "Dynamic regulation of sensorimotor
integration in human postural control." J Neurophysiol 91.
26. Shalal B, Nachum Z, Spitzer O, Ben-David J, Duchman H, Podoshin, L et
al. Computerized dynamic posturography and seasickness susceptibility.
Laryngoscope. 1999; 109(12): 1996-2000.
27. Pickett T, Radfar-Baublitz L, McDonald S, Walker W, & Cifu D.
Objectively assessing balance deficits after TBI: Role of computerized
posturography. JRRD. 2007; 44(7): 983-990.
28. Digital Acquire 4: Program Documentation. Bertec Balance Manual.
Website.
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Published Jan 2013. Accessed Jan 2017.
29. Designed for the Clinical Researcher. NeuroCom® Clinical Research
System (CRS). NeuroCom® Manual. Website.
http://www.natus.com/documents/014320A_lo-res_for%20web.pdf
Published 2014. Accessed Jan 2017.
30. Schupert C, Black F, Horak F, Nashner L. Coordination of the head and
body in response to support surface translations in normals and patients
with bilaterally reduced vestibular function. Posture and Gait:
Development, Adaptation and Modulation. 1988: 281-289.
31. Paquette C, Franzen E, & Horak Fay. More falls in cerebellar ataxia when
standing on a slow up-moving tilt of the support surface. Cerebellum. 2016;
15(3): 336-342.
32. Qato D, Wilder J, Schumm L, Gillet V, & Alexander G. Changes in
Prescription and Over-the-Counter Medication and Dietary Supplement
Use Among Older Adults in the United States, 2005 vs 2011. JAMA Intern
Med. 2016; 176 (4): 473-82.
33. Dai M, Cohen B, Smouha E, & Cho C. Readaptation of the vestibulo-ocular
reflex relives the mal de debarquement syndrome. Frontr Neurol. 2014.
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34. Guskiewicz KM, Ross SE, Marshall SW. Postural Stability and
Neuropsychological Deficits After Concussion in Collegiate Athletes. J
Athl Train. 2001;36(3):263-273.
35. Willis J, Vitale S, & Agrawal Y. Visual impairments, uncorrected refractive
error, and objectively measured balance in the United States. JAMA
Ophthalmol. 2013; 131(8): 1049-1056.
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Table 1: Subject Characteristics
*% indicates the percentage of subjects who indicated 'Yes' on the health
questionnaire form seen in Appendix E.
Past Medical History Subjects (n=50)
(%)*
Age 44.10 ± 14.33
Males (17) 34 %
Females (33) 66 %
Dizziness 6 %
Visual Impairments 34 %
Motion Sickness 20 %
Concussion > 10 yrs 2 %
Consumed Alcohol in Past
12 Hours <1 Glass
4 %
Medications 36 %
History of Surgeries 48 %
Appendectomy 8 %
Hysterectomy 16 %
Caesarian Section 8 %
Orthopedic Problems
Cervical Injury 2%
LE Injury 14 %
Knee Arthroscopy 10%
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Table 2: Pearson's Correlation Coefficients for SOT, MCT & ADT
r-value p-value
Condition 1 .34 .020
Condition 2 .65 .001
Condition 3 .40 .001
Condition 4 .57 .001
Condition 5 .61 .001
Condition 6 .65 .001
SOT Composite .81 .001
Somatosensory Ratio Score .34 .020
Vision Ratio Score .53 .001
Vestibular Ratio Score .60 .001
Preference Ratio Score .09 .560
MCT Composite .67 .001
ADT Toes Up Difference .08 .570
ADT Toes Down Difference .09 .540
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Table 3: Equilibrium Scores for SOT Conditions 1, 2, 3 and 4 across Age Groups
Age
Groups
Bertec™ NeuroCom® Bertec™ NeuroCom® Bertec™ NeuroCom® Bertec™ NeuroCom®
Condition 1 Condition 2 Condition 3 Condition 4
Mean ± sd Mean ± sd Mean ± sd Mean ± sd
20-29 92.46 ± 2.20 94.73 ± 2.01 92.97 ± 1.32 92.70 ± 1.69 91.70 ± 1.67 92.10 ± 2.61 76.64 ± 5.60 87.47 ± 5.79
30-39 93.38 ± 1.74 95.43 ± 1.16 92.83 ± 2.18 91.60 ± 2.46 92.10 ± 2.30 92.47 ± 2.02 73.13 ± 9.68 84.07 ± 7.77
40-49 92.27 ± 1.89 94.57 ± 1.56 92.30 ± 1.09 90.50 ± 2.88 90.10 ± 4.48 91.57 ± 1.30 70.67 ± 11.30 85.13 ± 5.76
50-59 92.98 ± 1.48 94.07 ± 1.81 90.50 ± 2.43 90.17 ± 2.56 89.03 ± 4.19 89.53 ± 4.07 68.77 ± 9.50 83.90 ± 7.85
60-69 92.33 ± 1.67 94.10 ± 1.14 91.80 ± 1.93 90.77 ± 2.05 91.36 ± 2.85 89.93 ± 3.62 70.40 ± 5.56 83.87 ±3.82
All Ages 92.68 ± 1.79 94.58 ± 1.59 92.08 ± 2.00 91.15 ± 2.51 90.86 ± 3.35 91.12 ± 3.03 71.92 ± 8.74 84.89 ± 6.26
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Table 4: Equilibrium Scores for SOT Conditions 5, 6 and Composite Score Across Age Groups
Age
Groups
Bertec™ NeuroCom® Bertec™ NeuroCom® Bertec™ NeuroCom®
Condition 5 Condition 6 SOT Composite
Mean ± sd Mean ± sd Mean ± sd
20-29 70.50 ± 10.52 68.80 ± 11.12 68.50 ± 9.45 74.83 ± 10.23 79.18 ± 4.67 82.60 ± 5.21
30-39 67.10 ± 11.30 68.23 ± 9.21 60.47 ± 13.17 69.77 ± 10.78 76.05 ± 7.06 80.70 ± 5.60
40-49 62.86 ± 10.47 63.93 ± 9.86 54.17 ± 9.60 60.50 ± 10.36 72.58 ± 6.09 77.70 ± 4.27
50-59 63.93 ± 9.38 64.33 ± 8.65 61.50 ± 9.86 65.47 ± 14.24 73.85 ± 6.62 78.20 ± 6.60
60-69 65.27 ± 8.41 59.63 ± 8.38 62.33 ± 10.23 64.70 ± 7.18 75.12 ± 4.32 77.20 ± 3.19
All Ages 65.93 ± 10.02 64.99 ± 9.70 61.39 ± 11.12 67.05 ± 11.46 75.36 ± 6.05 79.28 ± 5.31
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Table 5: Somatosensory, Vision, Vestibular & Preference Ratio Scores across Age Groups
Age
Groups
Bertec™ NeuroCom® Bertec™ NeuroCom Bertec™ NeuroCom® Bertec™ NeuroCom®
Somatosensory Vision Vestibular Preference
Mean ± sd Mean ± sd Mean ± sd Mean ± sd
20-29 100.60 ± 2.55 97.89 ± 2.52 82.90 ± 5.36 92.31 ± 5.34 76.5 ± 11.60 72.68 ± 11.91 98.30 ± 6.62 103.61 ± 7.50
30-39 99.40 ± 2.17 95.98 ± 2.15 78.40 ± 9.37 88.10 ± 8.15 71.90 ± 11.51 71.50 ± 9.55 95.40 ± 4.45 101.49 ± 3.48
40-49 100.10 ± 1.79 95.71 ± 2.84 75.80 ± 13.31 90.03 ± 5.99 68.10 ± 10.59 67.68 ± 10.95 93.30 ± 5.62 98.84 ± 8.22
50-59 97.40 ± 2.12 95.87 ± 3.09 73.80 ± 9.22 89.14 ± 7.56 68.70 ± 9.33 68.34 ± 8.64 97.50 ± 4.09 100.34 ± 9.01
60-69 99.50 ± 1.35 96.48 ± 2.70 76.20 ± 5.33 89.10 ± 3.26 70.60 ± 8.77 63.35 ± 8.66 98.00 ± 4.74 102.95 ± 5.64
All Ages 99.40 ± 2.24 96.38 ± 2.69 77.42 ± 9.20 89.73 ± 6.21 71.16 ± 10.44 68.71 ± 10.16 96.50 ± 5.32 101.45 ± 6.98
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Table 6: MCT Latency and ADT Toes Up & Down Trial 1 and 5 Sway Energy Difference Across Age Groups
Age
Groups
Bertec™ NeuroCom® Bertec™ NeuroCom® Bertec™ NeuroCom®
MCT Composite ADT Toes Up Difference ADT Toes Down Difference
Mean ± sd Mean ± sd Mean ± sd
20-29 130.50 ± 5.91 123.80 ± 8.43 30.00 ± 25.64 11.10 ± 21.71 17.50 ± 7.69 8.20 ± 23.66
30-39 125.50 ± 3.89 119.60 ± 9.79 24.10 ± 43.67 2.90 ± 10.02 26.10 ± 18.30 10.20 ± 21.19
40-49 132.80 ± 7.51 128.00 ± 7.06 21.60 ± 24.38 8.50 ± 10.07 37.70 ± 17.30 3.30 ± 24.24
50-59 130.90 ± 8.18 133.50 ± 15.44 11.30 ± 31.77 6.80 ± 25.54 23.50 ± 26.71 20.70 ± 14.40
60-69 128.20 ± 7.21 127.00 ± 8.51 22.20 ± 36.58 14.00 ± 13.07 19.70 ± 31.04 7.10 ± 25.40
All Ages 129.58 ± 6.92 126.38 ± 10.89 21.84 ± 32.38 8.66 ± 17.01 24.90 ± 22.05 9.90 ± 22.02
Page 46
36
a) b)
Figure 1: Bertec™ Balance AdvantageTM (a) and NeuroCom® Equitest (b)
Figure 2: Pearson's Correlation coefficient for Bertec™ and NeuroCom® for
SOT conditions 1-6 and SOT composite.
Note: Moderate to good positive r-values for SOT Conditions 2, 4-6. Asterisk
indicates p<.05.
0
0.2
0.4
0.6
0.8
1
Cond 1* Cond 2* Cond 3* Cond 4 * Cond 5* Cond 6* SOT
Comp*
Pea
rso
n P
rod
uct
Co
rrel
ati
on
(r) Pearson Product Coefficient for SOT
Bertec vs Neurocom
Linear (Bertec vs
Neurocom)
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Figure 3: SOT conditions 1-6, composite equilibrium score for all subjects
(N=50).
Note: The scores for Conditions 1, 4, and 6 of Bertec™ were significantly lower
compared to NeuroCom® with Condition 4 having the greatest 12.97 point mean
difference.
Figure 4: SOT composite equilibrium score across age groups
0
20
40
60
80
100
120
Cond 1* Cond 2* Cond 3 Cond 4* Cond 5 Cond 6* SOT
Comp*
Eq
uil
ibri
um
Sco
res
SOT Condition 1-6 Equilibrium Scores
Bertec
Neurocom
66
68
70
72
74
76
78
80
82
84
20-29 30-39 40-49 50-59 60-69 All Ages
Co
mp
osi
te E
qu
ilib
riu
m S
core
SOT Composite Score Across Age Groups
Bertec
Neurocom
Page 48
38
Figure 5: MCT latency composite scores comparing age groups
Note: The MCT composite latency scores were significantly slower on Bertec™
by 3.2 msec for all age groups.
Figure 6: MCT composite latency scores across age groups
-40
10
60
110
160
20-29 30-39 40-49 50-59 60-69 All AgesCo
mp
osi
te L
ate
ncy
(m
sec)
Age Group
MCT Composite Latency Across Age
Groups
Bertec
Neurocom
110
115
120
125
130
135
20-29 30-39 40-49 50-59 60-69 All Ages
La
ten
cy S
core
s (m
sec)
MCT Latency Scores
Bertec
Neurocom
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39
Figure 7: ADT toes up & down sway energy for the mean difference between
Trials 1 and 5.
Note: The ADT Toes Up and Toes Down sway energy scores were slower and had
significantly larger differences on Bertec™ as compared to NeuroCom®. Error
bars indicated 1 sd.
Figure 8: ADT toes up sway energy across age groups
-20
-10
0
10
20
30
40
50
60
Toes Up* Toes Down*
Sw
ay
En
erg
yADT Sway Energy Mean Difference
Bertec
Neurocom
0
5
10
15
20
25
30
35
20-29 30-39 40-49 50-59 60-69 All Ages
Sw
ay
En
erg
y
ADT Toes Up Sway Energy Across Age
Groups
Bertec
Neurocom
Page 50
40
Figure 9: ADT toes down sway energy across age groups
Figure 10: Condition 4 equilibrium scores for Trials 1-3.
Note the greater difference between devices during Trial 1 as compared to Trials 2
and 3 and equilibrium score.
0
50
100
Trial 1 Trial 2 Trial 3 Average
Eq
uil
ibri
um
Sco
res
Condition 4
Trials of Condition 4 Equilibrium
Score
Bertec
Neurocom
0
10
20
30
40
20-29 30-39 40-49 50-59 60-69 All Ages
Sw
ay
En
erg
y
ADT Toes Up Sway Energy Across Age
Groups
Bertec
Neurocom
Page 52
APPENDIX A: STANDARDIZED TESTING INSTRUCTIONS
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43 43
SOT
We will be testing your balance during different conditions of eyes open,
eyes closed and with the floor moving or a visual stimulus.
You will be notified of the condition beforehand.
You will perform each condition 3 times.
As part of the test, I won’t be able to talk to you.
1) This first condition is with your eyes open with nothing moving.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
-Testing...
-Testing Complete
2) This condition is with your eyes closed with nothing moving.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
-State: "Close your Eyes." "Testing"
-Once trial completed state 'Trial completed, open your eyes.'
3) This condition is eyes open with a visual stimulus.
-Your task is to stand with your arms to your side, stay as steady as you can.
-Are you Ready?
-Testing.
-Testing Complete
4) This condition is eyes open with the floor moving.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
-Testing.
-Testing Complete.
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5) This condition is eyes closed with the floor moving.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
-State: "Close your Eyes." "Testing"
-Once trial completed state 'Testing complete, open your eyes.'
6) This condition is eyes open with the floor and surrounding moving.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
- Testing.
-This test is completed, would you like a break before the next test?
MCT
This is called a Motor Control Test
The platform will move backwards or forwards 3 times and will increase in
increments from small, medium to large.
1) The platform will move backwards 3 times of small intensity.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
- Testing Complete.
2) The platform will move backwards 3 times of medium intensity.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
- Testing.
-Testing Complete
3) The platform will move backwards 3 times of large intensity.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
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- Testing.
-Testing Complete.
1) The platform will now move forwards 3 times of small intensity.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
-Testing.
-Testing Complete
2) The platform will move forwards 3 times of medium intensity.
-Your task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
- Testing.
- Testing Complete
3) The platform will move forwards 3 times of large intensity.
-You task is to stand with your arms to your side stay as steady as you can.
-Are you Ready?
- Testing.
-Testing complete
-This test is completed, would you like a break before the next test?
ADT
This is called an Adaptation Test. The platform will move in a toes up and
toes down direction.
As part of the test, I can't tell you when the movements will happen.
1) You will feel the platform move in a toes up direction several times.
-You task is to stand with your arms to your side stay as steady as you can.
-Are you ready?
- Testing.
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-Testing Complete
2) You will now feel the platform move in a toes down direction several times.
-You task is to stand with your arms to your side stay as steady as you can.
-Are you ready?
- Testing
-Your testing is now completed. (Thank subject for their participation.
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APPENDIX B: CONDITIONS 1-6 OF THE SOT
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APPENDIX C: MOTOR CONTROL TEST
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APPENDIX D: ADAPTATION TEST
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APPENDIX E: HEALTH QUESTIONNAIRE
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Subject Health Questionnaire:
1. Have you experienced dizziness or been diagnosed with inner ear or any other
balance or vestibular disorder?
[ ] Yes [ ] No
If Yes, please explain________________________________________________
2. Have you a prior head injury, open or closed?
[ ] Yes [ ] No
If Yes, please explain ________________________________________________
3. Have you had any prior cervical injury?
[ ] Yes [ ] No
4. Do you currently use an assistive device (e.g cane)?
[ ] Yes [ ] No
5. Are you able to stand unsupported for a minimum of 20 minutes?
[ ] Yes [ ] No
6. Do you have any visual impairments?
[ ] Yes [ ] No
If Yes, please explain ________________________________________________
7. Have you had a concussion after which you experienced headaches and/or other
symptoms?
[ ] Yes [ ] No
If Yes, please explain ________________________________________________
8. Have you been diagnosed with diabetes?
[ ] Yes [ ] No
9. Have you been diagnosed with peripheral vascular disease?
[ ] Yes [ ] No
10. Have you had any significant lower extremity joint disorder or injury?
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[ ] Yes [ ] No
If Yes, please explain ________________________________________________
11. Have you experienced any motion sickness or sensitivity?
[ ] Yes [ ] No
12. History of any neurological disease?
[ ] Yes [ ] No
13. Any history of surgeries?
[ ] Yes [ ] No
If Yes, please explain ________________________________________________
14. Any recent illnesses or ear infections?
[ ] Yes [ ] No
If Yes, please explain ________________________________________________
15. Have you consumed any alcohol in the past 12 hours?
[ ] Yes [ ] No
16. Please list (or provide) your current prescribed and/or over-the-counter
medications._________________________________________________
I, _____________________________, confirm that the above information is true
to my knowledge.
_______________________ _______________________
Participant Date
_______________________ _______________________
Witness to Signature Date
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APPENDIX F: INFORMED CONSENT
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I.D.#
FRESNO STATE PHYSICAL THERAPY DEPARTMENT
PARTICIPANT CONSENT FORM
Project Title: Computerized Posturography using the Bertec in Healthy Adults
Principal Investigator: Peggy R. Trueblood, PhD, PT
Professor and Chair
Department of Physical Therapy
Co-Investigators: Marcia Thompson, DSc, DPT
Assistant Professor
Department of Physical Therapy
Leslie Zarrinkhameh, PT, DPT, GCS
Lecturer, Department of Physical Therapy
Toni Tyner, MHL, PT
Assistant Professor, Department of Physical Therapy
Student Investigators: Carolyn Bentley, SPT
Christian Lopez, SPT
PURPOSE OF RESEARCH
I have been informed that the overall purposes of this project are to collect normative data on a new
posturography system that measures a person’s balance and to compare this system to the gold standard
system, also measuring your balance or postural control. More specifically, we will 1) collect normative
data using the Bertec Computerized Dynamic Posturography (CDP) system using virtual reality with
images projected in a specially modified dome and 2) compare this data with the sway-referencing used by
EquiTest systems developed by NeuroCom International. The images used in the Bertec system are
controlled by the system’s computer and move in correspondence to your postural sway detected by a force
plate that you will stand on during the protocols. The image is concentric ovals leading to a grey oval
shape, creating the perception of a tunnel with no definable end or horizon during the Sensory Organization
test. In the case of the EquiTest system by NeuroCom, the dome is referenced by your postural sway on the
forceplate.
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I acknowledge that my participation is voluntary and will include a 60 minute collection period
(approximately 30 minutes with each system). The project will be conducted in McLane 104 and 111, the
Department of Physical Therapy at California State University, Fresno.
CRITERIA FOR PARTICIPATION
I am eligible to participate in this study if I meet the following criteria: 1) age 20-59 years old without any
significant medical history or known neurological or musculoskeletal disorder/impairment that can impact
my balance. I am aware that I will be ineligible to participate in this study if I do not meet the criteria
noted above and/or have a prior history of any of the following: 1) dizziness, inner ear, or other balance or
vestibular disorder, 2) closed or open head injury, 3) cervical injury, 4) assistive device use or inability to
stand for 20 minutes, 5) visual impairment (worse than 20/40 with corrective lenses), 6) concussion after
which I experienced headaches and/or other symptoms, 7) diabetes, 8) peripheral vascular disease, 9) any
significant lower extremity joint disorder or injury, 10) motion sickness/sensitivity.
PROCEDURE
I am aware that I will be:
1) Screened using a questionnaire to determine my eligibility before testing.
2) If eligible for testing, my name will be entered as a code name, eg Fresno 101, 102, etc into the
computerized systems that test your balance
3) My age, sex, height information will be entered in the systems. These parameters are used to
determine proper foot placement.
4) I will be provided standard instructions prior to the start of each test condition including the start
of each test. During the recordings, I will maintain a steady standing position.
5) I will be tested on two different computerized systems, each using 3 different tests to measure
balance: Sensory Organization Test (SOT); Adaptation Test (ADT) and the Motor Control Test
(MCT).
6) I will be tested without shoes. The investigator will align my feet properly at the beginning of the
tests.
7) I am allowed to rest as often as necessary throughout the testing.
8) During some of the tests the support surface and or the visual surround may move gently during
some of the recording trials. My task will be to remain as steady as possible. The investigator will
inform me when this may occur.
9) During all of the testing, I will be in a restraining harness and the investigator will remain in close
proximity in case I lose my balance.
10) The entire session will take approximately 30 minutes on each system. I will have a 15 minute rest
period between testing on the two balance systems.
11) I will first perform all of the standing balance tests on the Bertec System in the following order:
a) First, I will complete the Sensory Organization Test (SOT) This balance test systematically tests
our three sensory systems: vision, vestibular or inner ear, and somatosensory or our sensation of
our feet. During the SOT, I will complete 3, 20 second trials of six different test conditions (18
total trials) during the Sensory Organization Test. I will be allowed to rest between conditions as
needed. The order of testing is as follows:
i. Eyes open with a fixed (i.e. not moving) surface and visual surround
i. Eyes closed with a fixed surface
ii. Eyes open with a fixed surface
iii. Eyes open with a fixed surface and sway-referenced (i.e., moving) visual
surround
iv. Eyes open with a sway-referenced surface and fixed visual surround
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v. Eyes closed with a sway-referenced surface
vi. Eyes open with a sway-referenced surface and visual surroundings.
b) Next I will perform the Motor Control Test (MCT). This test is designed to assess my ability to
recover automatically from external perturbations or slight movements under my feet. The scale of
the movement is based on my height. This test will also include six different conditions, 3 trials
each, which are as follows:
i. Backward translation, small
ii. Backward translation, medium
iii. Backward translation, large
iv. Forward translation, small
v. Forward translation, medium
vi. Forward translation, large
c) The final test I will perform is known as the Adaptation test (ADT). This test measures my ability
to counteract a movement of the surface that I am standing on in a toes up or toes down direction.
I will be given 5 trials of each condition (toes up and toes down).
12) I will have a 15 minute rest period before repeating these tests on the NeuroCom System.
BENEFITS
I understand that there is no benefit in my participation in this project except to have my balance tested on
two different, but similar computerized systems. My participation will add to the normative database for a
new computerized balance system on the market and will help determine if there are differences in the
balance scores as compared to the gold standard system already in use.
RISKS AND DISCOMFORTS
Risks associated with the balance tests are minimal. I am aware that participation in this project may lead to
fatigue or dizziness. To avoid this, rest breaks will be allowed. I understand that there is a possibility that I
may lose my balance at times during the assessments. To prevent a fall or loss of balance, I will wear a
safety harness for all testing and will be guarded by trained investigators.
CONFIDENTIALITY
I understand that the findings of this study will be kept confidential and will be stored in a secure location.
Should the data be used for publication in medical literature or for teaching purposes, I understand that only
the investigators will know my identity and I will not be identified by my name in any publication. I
further understand that photographs and videotapes will be used only with my written permission.
REQUEST FOR MORE INFORMATION
I understand that I have the right to ask and have answered questions concerning this study at any time. Dr.
Peggy Trueblood, the principal investigator, is available to answer my questions or concerns at 278-3008. I
will receive a copy of this consent form to refer to for further reading or clarification if needed.
REFUSAL OR WITHDRAWAL OF PARTICIPATION
I understand that my participation is voluntary and that I may refuse to participate or withdraw consent and
discontinue participation in this study at any time. I also understand that the investigators may terminate
my participation in this study at any time after they have explained the reasons for doing so.
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INJURY STATEMENT
I understand that in the event of any physical injury resulting from my participation in this study, my
physician will be notified and treatment will be available at my own expense. There will be no form of
legal or monetary compensation available from the California State University, Fresno, my referring
physician, or the above listed investigators.
I have explained to ______________________________ the purpose of this study, the procedures, and the
possible risks and benefits to the best of my ability.
______________________________ ______________________
Investigator Date
CONSENT
I confirm that the investigators have explained to me the purpose of the project, interview process,
screening, and procedures that I will undergo. I also understand the possible risks and benefits that I may
experience as a result of this study. The procedures for this research have been reviewed and approved by
California State University, Fresno, Committee on Protection of Human Subjects. I have read and
understand this consent form. Therefore, I agree to give my consent to participate as a subject in this
project.
______________________________ ______________________
Participant Date
______________________________ ______________________
Witness to Signature Date
I do/do not authorize the taking of photographs or videotapes of myself for either publication or use as
educational materials.
_____________________________ ______________________
Participant Date
_____________________________ ______________________
Witness to Signature Date
I.D.#
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MEDICAL RESEARCH PATIENT’S BILL OF RIGHTS
California law requires that any person asked to take part as a subject in research involving a medical
experiment, or any person asked to consent to such participation on behalf of another, is entitled to receive
the following list of rights written in a language in which the person is fluent. This list includes the right
to:
1. Be informed of the nature and purpose of the experiment.
2. Be given an explanation of the procedures to be followed in the medical experiment and any drug or
device to be utilized.
3. Be given a description of any attendant discomforts and risks reasonably to be expected from the
experiment.
4. Be given an explanation of any benefits to the subject reasonably to be expected from the experiment,
if applicable.
5. Be given a disclosure of any appropriate alternative procedures, drugs, or devices that might be
advantageous to the subject, and their relative risks and benefits.
6. Be informed of the avenues of medical treatment, if any, available to the subject after the experiment if
complications should arise.
7. Be given an opportunity to ask any questions concerning the experiment or the procedures involved.
8. Be instructed that consent to participate in the medical experiment may be withdrawn at any time and
the subject may discontinue participation in the medical experiment without prejudice.
9. Be given a copy of the signed and dated written consent form.
10. Be given the opportunity to decide to consent or not to consent to a medical experiment without the
intervention of any element of force, fraud, deceit, duress, coercion, or undue influence on the
subject’s decision.