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Background

Perometer (400T) measurement of lower limb volume: An investigation of criterion validity Cathy Bulley , Fiona Coutts, Andrew Grainger Queen Margaret University, Edinburgh, UK. Background. Various musculoskeletal conditions  limb volume Limb volume – outcome measures Fluid displacement

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Background

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  1. Perometer (400T) measurement of lower limb volume: An investigation of criterion validity Cathy Bulley, Fiona Coutts, Andrew Grainger Queen Margaret University, Edinburgh, UK

  2. Background • Various musculoskeletal conditions  limb volume • Limb volume – outcome measures • Fluid displacement • Geometric calculations from limb circumferences using tape measure • Perometer – optoelectronic imaging device; limb shape and volume (Pero-System GmbH)

  3. Fluid displacement: limb submerged in water, measurement of fluid displaced inconvenient unhygienic poor reliability no information on shape Geometric calculations from limb circumferences using tape measure frequently used clinically non-standard protocols reliability issues Current Methods

  4. 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)

  5. Perometer (Pero-System GmbH) • optoelectronic imaging device • limb shape and volume • quick, easy Track Frame Base plate

  6. Perometer estimation of limb volume Positioned every 2.54 mm Diameter measurements every 4.7 mm Positioned every 1.27 mm Summed volume of elliptical discs

  7. Purpose • 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)

  8. Standardised Protocol Greater trochanter • Development of a standardised protocol • Limb position on the base plate, and degree of rotation • Lower limb landmarks – standardised proportion of the limb for volume measurement 65% Femur Lateral epicondyle Lateral Malleolus

  9. Validity Study • Ethical approval: Physiotherapy Ethics Sub-Committee, QMU. • 30 healthy volunteers: • 22 F, 8M • mean age: 26 • mean height: 67.2 cm • mean weight 171.0 kg. • Exclusion criteria: relevant past medical history

  10. 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

  11. 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

  12. 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

  13. Statistical Analysis • Shapiro-Wilk: Normality of distribution • Parametric inferential statistics: • ICC (3,1) • Limits of agreement (Bland & Altman, 1986) between two limb volume estimates

  14. Perometer limb volume (x of 3) = 8560 ml Normal distribution p=0.268 Circumferential limb volume = 8717 ml Normal distribution p=0.602 Results 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

  15. 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

  16. Acknowledgements MSc pre registration Physiotherapy students: • Nicola Dinsmore • Georgina Enderson • MaryAnne Geraghty

  17. THANK YOU Sponsors: School of Health Sciences, Queen Margaret University, Edinburgh Centre for Integrated Healthcare Research, Edinburgh

  18. 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

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