Perometer (400T) measurement of lower limb volume:

development of a standardised protocol

Fiona Coutts, Andrew Grainger, Dr Cathy Bulley

Queen Margaret University, Edinburgh, UK

Background

• Various musculoskeletal, oncological or vascular conditions result in increased 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, Wuppertal, Germany)

Purpose

• True repeatable measurement important in monitoring treatment efficacy.

• Perometer (400T) optoelectronic imaging device used to assess limb volume. No protocol has been published to standardise its use.

Study Design

Standardised protocolFoot position

on base plate

(B)

DiurnalVariation

(A)

End point of limb

measurement (C)

Use of software

(D)

Phase 1 Phase 2

Phase 3

Rest Period

(A)

Speed of frame

Movement (C)

Leg position (Rotation) (B)

Phase 1A: Diurnal Variation

• Issue: Does limb volume change through a day?

• Design: n=2, healthy participants. 3 volume measurements @ 3 times per day, between 09.00 and 18.00.

• Results: Volumes averaged and % differences to initial volume were calculated. <2% volume change for each participant.

Tester 1 2

Morning – 1.1% 1.6%Afternoon Morning – 1.8% 1.2%Evening

Phase 1B: Foot position

• Issue: Does the position of the limb on the base plate alter measurement data?

• Design: Cylinder placed in each of the 16 squares marked on the base plate, measured 3 times.

• Results: Four centre squares (A,B,C,D) demonstrated the highest repeatability of measurement. Corner squares (1,2,3,4) lowest repeatability.

A B

D C

3

1 2

4

Phase 1C: End point of limb measurement

• Issue: Standardised landmarks for measurement of volume?

• Design: n=4, frame advanced to comfortable maximum vertical height, leg marked. Calculated as % of length Position 1 to 2 (see below)

• Results: % leg length= 67.6, 69, 79.1, 81.7; 65% of leg length was max. height for vertical frame advancement

Grt Trochanter(1)

65% Femur

Lat Femoral Epicondyle(2)

Lateral Malleolus

Standardised Protocol 1

• Diurnal variation: keep standardised times for repeat visits

• Foot position: maintain foot in the centre of the base plate at all times

• End point of measurement: 65% of distance from lateral femoral Epicondyle to Greater Trochanter

Repeatability after phase1

• n= 30 (22F: 8M) (25.9±3.48yrs, 171.02±6.77cm, 67.32±7.68Kg)

Dominant leg – tested 9 times by a rater on 2 consecutive occasions

ICC (p<0.001) 95% CI

0.99

0.996-0.999

Upper LOA 185.18 ml

Lower LOA -193.81 ml

Range

% variation

378.99ml

4.07%

LOA= Limits of Agreement (Bland & Altman, 1986)

Concerns after phase 1

• Rest period prior to commencement of measurement

• Axial rotation of the limb in the frame

• Speed of Perometer frame movement

= Phase 2

Phase 2A: Rest Period

• Issue: Stasis of limb volume prior to assessment with perometer

• Design: Pre and post rest limb volume at : 2.5, 5,10,12.5,15 mins., n=2 healthy participants

• Results: Volume change variable until 10 minutes of rest. After 10 mins. less variable.

% Difference from pre rest

-0.01

-0.005

0

0.005

0.01

0.015

0.02

2.5 5 10 12.5 15

Minutes of rest

Participant 1

Participant 2

Phase 2B: Leg position

• Issue: Does axial limb rotation cause measurement error?

• Design: Full size mannequin limb positioned 10 increments to internal and external axial rotation (0 - 50°), 3 times.

• Results: Mean of 3 tests on 2 occasions shows little variation, CoV <0.1% in all bar 1 position, <1.2% overall

Mean Volumne in axial rotation (mls)

0

2000

4000

6000

8000

50 40 30 20 10 0 10 20 30 40 50

Ext. Rot. Neutal Int. Rot.

Coefficient of Variation (%)

0.00.2

0.40.60.81.0

1.21.4

50 40 30 20 10 0 10 20 30 40 50

Ext. Rot. Neutral Int. Rot.

Phase 2C: Speed of frame

• Issue: Does speed of movement affect Perometer measurement?

• Design: mannequin limb measured 30 times

Fast speed = 0.37m/s Slow speed = 0.022m/s Controlled by a motor

• Results: Significant differences between slow and fast speeds , (p<0.00001)

Motor

Mean Perometer measures at Slow and Fast speeds (n=30)

6685

6690

6695

6700

6705

6710

6715

6720

6725

1

0.022m/s Speeds 0.37m/s

mls

p<0.00001

Reliability

Results: Session 1 Session 2

Rater 1 9005.53 8993.10 1504.8 1393.9

(p<0.0001) (p<0.0001)

Rater 2 9088.27 9102.10 1417.1 1452.9

(p<0.0001)

Intra- & inter-rater reliability, n= 30, 2 raters, 2 occasions

Phase 3: Use of software

• Issue: Software allows limb measurement length to change in two screens

• Design: A) reliability study using independent measurement of length

B) use of single limb length measures on 2 occasions

• Results: Variability

A): n=30 B): n=10

Rater 1 = 20% Rater 1= 3.8%,Rater 2 = 16.3% Rater 2 = 5.3%

Conclusions

Protocol reliable if:1. 10 min rest period before testing with elevated

leg2. Neutral axial rotation of limb3. Foot placed in centre of base plate4. Constant slow speed is maintained5. Only 1 limb length measurement is taken and

used on repeat visits

Clinical implications

• Use of a standardised protocol will allow reliable data to be collected on repeated basis,

• Monitor efficacy of management of patients with changing limb volume.

Queen Margaret University

Thank You

Acknowledgements

• MSc pre registration Physiotherapy students:

2007 2006

Francis Burgin Nicola Dinsmore

Áine O’Connor Georgina Enderson

MaryAnne Geraghty