10/10/2011
Quantifying Posture According
to an International Standard
Barbara Crane PhD, PT, ATP
University of Hartford
West Hartford, CT
Objectives
At the end of this session, attendees will be
able to:
1. Describe the technical concepts
presented in ISO 16840-1
2. Understand current activities to
develop methods for clinical
application of this standard
In this workshop…
Review of ISO 16840-1
Clinical Guidelines Development
Tools and methods of measuring
Preliminary Research Results
Discussion/demonstrations
Purpose of this session:
Provide a summary of the critical concepts
in the body and seat measures standard
Identify particular challenges associated
with applying this standard in practice
Describe and discuss work being done re:
clinical application of this standard
Where are we now?
A little history…
ISO 16840-1
Wheelchair seating —
Part 1:
Vocabulary, reference axis convention
and measures for body segments,
posture and postural support surfaces
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10/10/2011
ISO 16840-1
International standard developed in ISO WG11
(TC173/SC1)
Has completed final draft international standard
voting and is now an official International
Standard
Will be revised in the near future
Scope of ISO 16840-1
Define a global coordinate system for
posture description of a wheelchair-seated
person
Posture (body angles) and linear
dimensions of the person
Linear dimensions, locations, and angles
of seated support surfaces
Right hand rule - axes
Global Coordinate
System
Right hand rule in action
Integrated
Measurement
System
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Seated Anatomical Axis System
Support Surface Axis System
Wheelchair Axis System
Compass Rose
measurement convention
The Seated Person
number of body segments
Body Measures
of a Seated Person


minimum needed to define seated posture
define landmarks for each segment
represent each segment by a line
(segment line)
segment line joins chosen body
landmarks
repeat in all three views
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10/10/2011
Body
Landmarks:
sagittal
plane
Body
Landmarks:
frontal
plane
Segments in Sagittal View
Body
Landmarks:
transverse
plane
Absolute Angle Measures orientation of body segments in space
Absolute vs. Relative
Angle Measures
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Relative
Angle
Measures orientation of
the
segments to
each other
In Summary:
ISO 16840-1
specifies an integrated geometric
reference system
defines linear and angular measures in
three planes
specifies standard terminology and
abbreviations for each of the measures
facilitates development of measurement
and recording tools
For the
seated person
it specifies :
For the person’s
support surfaces
it specifies:
body landmarks (~50) and body
segments (~30) to be used
linear body measures to be used (~30)
absolute body segment angles to be
used (~30)
relative body segment angles commonly
used (~10)
16840-1 uses the person’s
wheelchair to:
define the location of the origin (0,0,0c) of
the geometric axis system
(0,0,0c) provides measurement benchmark
across clinical visits
linear measures
location in space
absolute angles in space
relative angles of commonly used
adjacent support surfaces
Implementing the Standard…
Two guidelines to aid implementation


Clinical Application Guide
Glossary of Terms and Definitions
Currently under development!
ISO and RESNA standards working
groups
Hope to publish electronically for easy
access
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10/10/2011
Clinical Application Guide
Sagittal Trunk To Thigh Angle (relative angle):
Locate body landmarks: Locate the greater trochanter
(to approximate the hip joint center), the lateral femoral
condyle, and the acromion process (to approximate the
lateral lower neck point). The standard offers a formula
for calculation of the hip joint center and the lower neck
point if greater measurement precision is required.
Measure the angle: Place the goniometer center over
the greater trochanter. Align the stationary arm along
the sagittal trunk line, pointing towards the acromion.
Align the moveable arm along the sagittal thigh line,
pointing towards the lateral femoral condyle.
Clinical Application Guide
Sagittal Pelvic Angle (absolute angle):
Locate the sagittal pelvic line: Palpate the ASIS and
PSIS and locate the line between the ASIS & PSIS
(referred to as the ASIS-PSIS line). Locate the hip joint
center (or greater trochanter), and then drop a
perpendicular from the ASIS-PSIS line passing through
the greater trochanter. This is the sagittal pelvic line.
Measure angle: Place the goniometer pivot center over
the greater trochanter. Align the stationary arm with the
vertical. Align the moveable arm along the sagittal pelvic
line, or more simply, perpendicular to the ASIS-PSIS
line. Measure the angle created.
Tools – Bubble level for goniometer
Tools - Horizon
Tools - Rysis
Tools – for Photos
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Introduction
Preliminary studies:
Interrater Reliability of Rysis
Landmark Reliability
Validity of Rysis
Science of wheelchair seating


Effects of seated posture




Previous Posture Measures
Seated Postural Control Measure (SPCM)


Originally pediatric based
Largely qualitative
Various Clinical Instruments




Goniometers – standard, bubble
inclinometers, goniometers with bubble levels
Plumb lines
Posture grids
Radiography
Methods
Convenience sample of 19 unimpaired
subjects
Data collected in Human Performance Lab
at the University of Hartford
All subjects provided informed consent and
provided photographic releases
Instrumentation


Optotrak
Rysis photo analysis software
Relies heavily on understanding postures
Need to measure posture to assess results
Comfort
Functional activities
Physiologic function
Mobility
Objectives of the Study
1. Investigate the inter-rater reliability of the
Rysis photo processing method
2. Investigate the validity of the Rysis photo
processing method using the Optotrak 3D motion capture system as a gold
standard
3. Investigate reliability of landmarking for
two pelvis landmarks
Methods – Optotrak (“gold standard”)
Markers on head, trunk, pelvis
3D accuracy to within 0.5 mm
Cardinal planes angles used

actual 3D angles possible
Blinded reliability studies


reference markers on pelvis
optical pointer
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Landmarks Used
Optical pointer
Both eye corners
Right Tragion
Right upper neck point
Base of Nose
Upper Sternal Notch
Lower Sternal Notch
Both ASIS’s
Right PSIS
Right Iliac Crest Point
Photo Processing in Rysis
Statistical Analysis
Results: Landmark reliability
Landmark reliability


Inter and intra-rater reliability
ICC models (3,1) and (2,1)
Intrarater Reliability
Body
Landmark
Interrater Reliability
Medial
/Lateral
Anterior
/Posterior
Superior
/Inferior
Medial/
Lateral
Anterior
/Posterior
Superior
/Inferior
PSIS
0.838
0.989*
0.594
0.397
0.983*
0.216
Iliac Crest
0.952*
0.872
0.803
0.820*
0.738
0.457
Validity of Rysis data


Criterion validity with Optotrak as “gold
standard”
Pearson Product Moment Correlation
Coefficients
Reliability of Rysis photo processing


Inter-rater reliability
ICC
*Represent deviation of the landmark location into the body; lowest ICC value reported
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Rysis processing reliability
Rysis Validity compared with Optotrak
Body Segment Angle
Pearson Correlation Coefficient
Sagittal Pelvic Angle
0.903*
Sagittal Trunk Angle
0.815*
Sagittal Head Angle
0.795*
Frontal Pelvic Angle
0.721*
Frontal Abdominal Angle
0.662*
Frontal Neck Angle
0.541*
Frontal Head Angle
0.482*
Sagittal Sternal Angle
0.417
Frontal Trunk Angle
0.335
Frontal Sternal Angle
0.327
Sagittal Neck Angle
0.268
Sagittal Abdominal Angle
0.072
*Correlation Coefficients Significant at the 0.05 level
Discussion – Validity of Rysis
Pearson Correlation Coefficient


7/12 statistically significant at the 0.05 level
Coefficients ranged from 0.428-0.903
General Discussion
Study presents a limited investigation of
basic psychometric properties
Generally intra-rater reliability higher than
inter-rater
Overall: moderate to excellent validity of
the system when compared with Optotrak
Conclusions
Rysis shows promise for being a good objective
posture measure
Limitations




Small number of subjects
Different palpation techniques used
Visibility of landmarks in Rysis
Subjects required to move to accommodate camera
Future Study


Add third camera view for transverse plane
assessment
Develop and test a more reliable palpation method
References
1. Tyson, S. (2003). A Systematic Review of Methods to
Measure Posture. Physical Therapy Reviews. Volume
8; 45-50.
2. Fife, S. E., Roxborough, L. A., Armstrong, R. W.,
Harris, S. R., Gregson, J. L., & Field, D. (1991).
Development of a clinical measure of postural control
for assessment of adaptive seating in children with
neuromotor disabilities. Physical Therapy, 71(12), 981993.
3. Sprigle, S., Wootten, M., Bresler, M., & Flinn, N.
(2002). Development of a noninvasive measure of
pelvic and hip angles in seated posture. Archives of
Physical Medicine & Rehabilitation, 83(11), 1597.
4. Sciotti, V.M., Mittak, V.L., DiMarco, L., Ford, L.M.,
Plezbert, J., Santipadri, E., Wigglesworth, J., Ball, K.
(2001). Clinical precision of myofascial trigger point
location in the trapezius muscle. Pain. 93, 259-266.
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10/10/2011
Acknowledgements
Questions???
DPT Students involved in this project


Class of 2010: Sarah Hood and Melissa
Abeling
Class of 2011: Leanne Peters, Kelly MorinIrwin, Angela Shivazad and Alicia Lalla
Contact Information:
Barbara Crane:


Barb.crane@cox.net or bcrane@hartford.edu
(860) 768-5371
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