perometer (400t) measurement of lower limb volume: an investigation of criterion validity cathy...
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![Page 1: Perometer (400T) measurement of lower limb volume: An investigation of criterion validity Cathy Bulley, Fiona Coutts, Andrew Grainger Queen Margaret University,](https://reader035.vdocument.in/reader035/viewer/2022062314/56649de55503460f94add7eb/html5/thumbnails/1.jpg)
Perometer (400T) measurement of lower limb volume:
An investigation of criterion validity
Cathy Bulley, Fiona Coutts, Andrew Grainger Queen Margaret University, Edinburgh, UK
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Background
• Various musculoskeletal conditions limb volume
• Limb volume – outcome measuresFluid displacementGeometric calculations from limb
circumferences using tape measure Perometer – optoelectronic imaging device;
limb shape and volume (Pero-System GmbH)
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Current Methods
• Fluid displacement: limb submerged in water, measurement of fluid displacedinconvenientunhygienicpoor reliabilityno information on
shape
• Geometric calculations from limb circumferences using tape measure frequently used
clinicallynon-standard
protocolsreliability issues
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Circumferential Measurement• Limb circumference at specified
points on limb – quick, simple• Lack of agreement on measurement
points – specific anatomical landmarks or regular intervals e.g. 3 or 4 cm (Karges et al, 2003)
• Geometric formulae to estimate volume of different segments summed
• Different formulae used (e.g. disc model, truncated cone model)
• Reliability issues: e.g. tape measure tension (Brorson, 2000)
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Perometer (Pero-System GmbH)
optoelectronic imaging device
limb shape and volume
quick, easy
Base plate
Frame
Track
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Perometer estimation of limb volume
Positioned every 2.54 mm
Positioned every 1.27 mm
Diameter measurements every 4.7 mm
Summed volume of elliptical discs
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• Perometer – gold standard? • Face validity• Lack of standardised protocol and research
• Criterion Validity:
This study compared lower limb volume measured using :
Geometric calculation from limb circumferences (Tape measure Disc model method, Man et al, 2004)
Perometer (400T: upright model)
Purpose
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Standardised Protocol• Development of a
standardised protocolLimb position on the
base plate, and degree of rotation
Lower limb landmarks – standardised proportion of the limb for volume measurement
Greater trochanter
65% Femur
Lateral epicondyle
Lateral Malleolus
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Validity Study
• Ethical approval: Physiotherapy Ethics Sub-Committee, QMU.
• 30 healthy volunteers: 22 F, 8Mmean age: 26mean height: 67.2 cmmean weight 171.0 kg.Exclusion criteria: relevant past medical history
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Protocol 1• Participants requested to avoid vigorous exercise /alcohol consumption 24 hr before testing and avoid food / drink intake 1 hr before testing
• 15 minute rest period with limb elevated to 90°
• Standardised limb reference marks
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Protocol 2
• Standardised limb reference marks
• Standardised positioning of limb in Perometer frame – use of spirit level
• Three Perometer measurements• Tape measurements at 3 cm
intervals• Assessor blinded to limb volume
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Limb volume estimation
• Perometer: Volumes in ml calculated between two reference marks in perometer computer software
• Tape measurements: Disc model method (Man et al, 2004) in ml (1ml = 1 cm3)
Σ (C²/4π) x h
C = circumference of disc
h = height of disc
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Statistical Analysis
• Shapiro-Wilk: Normality of distribution
• Parametric inferential statistics: ICC (3,1) Limits of agreement (Bland & Altman, 1986)
between two limb volume estimates
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Results• Perometer limb
volume (x of 3)
= 8560 ml• Normal distribution
p=0.268
• Circumferential limb volume
= 8717 ml• Normal distribution
p=0.602
Difference 157 ml
• ICC (3,1): good association (0.952, p<0.001)
• Poor agreement 15.67% variation between estimates:
95% of Perometer estimates will be:
between 519 ml (6.01%) more and 834 ml (-9.66%) less than circumferential estimates
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Bland-Altman LOA for Perometer and Cicumferential Measure
-840
-740
-640
-540
-440
-340
-240
-140
-40
60
160
260
360
460
560
660
760
6000 7000 8000 9000 10000 11000 12000
Average limb volumes by Perometer and Circumferential Measure (ml)
Dif
fere
nce
s in
mea
n v
olu
mes
of
Per
om
eter
an
d C
ircu
mfe
ren
tial
M
easu
re (
ml)
Mean + 2 S.D. 519.19 mls
Mean -157.48 mls
Mean - 2 S.D. -834.25 mls
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Conclusions• Poor agreement – measurement methods
are not interchangeable Perometer – greater face validity Circumferential – more clinically feasible
• Results do not indicate accuracy of either method
• 21 / 30 data sets – overestimation by circumferential method
• More work is needed to determine accuracy
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Acknowledgements
MSc pre registration Physiotherapy students:
• Nicola Dinsmore
• Georgina Enderson
• MaryAnne Geraghty
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Sponsors:
School of Health Sciences, Queen Margaret University, Edinburgh
Centre for Integrated Healthcare Research, Edinburgh
THANK YOU
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References• Bland J, Altman D (1986) Statistical methods for
assessing agreement between two methods of clinical measurement. The Lancet 8: 307-310
• Brorson H (2000) Liposuction gives complete reduction of chronic large arm lymphoedema after breast cancer. Acta Oncologica 39: 407-420
• Karges J, Mark B, Stikeleather S et al (2003) Concurrent validity of upper-extremity volume estimates. Physical Therapy 83: 134-145
• Man I, Markland K, Morrissey M (2004) The validity and reliability of the Perometer in evaluating human knee volume. Clinical Physiology and Functional Imaging 24: 352-358