Understanding residual limb volume loss - utilising a physical model (Manikin)

Jia Lizhang1, Kerry Coleman2, Magnus Gislason2, Lüder Mosler3, and Arjan Buis1

1. NCPO, Department of Bioengineering, University of Strathclyde Glasgow, UK

2. Department of Mechanical and Aerospace Engineering, University of Strathclyde Glasgow, UK

3. Otto Bock HealthCare GmbH

Introduction - Hypothesis

It is suggested that vacuum-assisted suspension systems retard limb volume reduction in part through improving fluid inflow into the residual limb so that it better balances with fluid outflow.

This study investigated if it is it physically possible to manage volume changes in a controlled environment.

Introduction - Background

Volume loss of the residual limb can;•cause discomfort, pain, and loss of prosthetic fit; •affect the delivery of shear stresses to the weight bearing structure ‘the skeleton’; •affect suspension and the limb’s pistoning in the socket during ambulation;•In addition, volume fluctuation varies greatly among individuals as a function of comorbidities, prosthesis fit, activity level, etc.

Methods A Physical Model of a Transtibial Residual Limb & Experimental Tests in Instron

Right: The physical model tested in Instron MachineLeft: The physical model structure

Results –

Results – -200N~35N 30 cycles experimental results

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Results – -200N~35N one cycle FE Modelling (no vacuum)

Left: one cycle displacement in one second Right: FE modelling interface pressure distribution

Results – Comparison of experiments & FE modelling (no vacuum)

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Results – -700N~35N 30 cycles experiments results

Discussion

• Limited evidence exists regarding the management of limb volume, and the evidence available focuses on adults with trans-tibial amputation.

• It is essential to understand what is physically happening under controlled conditions and this study is a first attempt to do so.

• Furthermore, the development of a Finite-Element model informed by empirical and clinical tests created a valuable understanding what is physiological possible and what not.

Conclusions• Application of a vacuum to the socket/liner

interface considerably reduces pistoning in the physical model

• Consistent displacement result was found on the physical model experimental tests and the FE model

• Reduction of volume loss could not be replicated in the physical model

• A clinical-significant-study is recommended.

Acknowledgements

Ms Katika SamaneeienDr Philip Riches Bioengineering University of Strathclyde Glasgow

Mr Schönemeier Mark Otto Bock HealthCare GmbH