Subject Specific Optimisation of the Stiffness of Footwear Material for Maximum Plantar Pressure Reduction

Panagiotis E Chatzistergos,Aoife Healy,Peter Gerth,Roozbeh Naemi,Nachiappan Chockalingam

doi:10.1007/s10439-017-1826-4

Panagiotis E Chatzistergos, Aoife Healy + Show 3 more

Open Access

https://doi.org/10.1007/s10439-017-1826-4

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Abstract

Current selection of cushioning materials for therapeutic footwear and orthoses is based on empirical and anecdotal evidence. The aim of this investigation is to assess the biomechanical properties of carefully selected cushioning materials and to establish the basis for patient-specific material optimisation. For this purpose, bespoke cushioning materials with qualitatively similar mechanical behaviour but different stiffness were produced. Healthy volunteers were asked to stand and walk on materials with varying stiffness and their capacity for pressure reduction was assessed. Mechanical testing using a surrogate heel model was employed to investigate the effect of loading on optimum stiffness. Results indicated that optimising the stiffness of cushioning materials improved pressure reduction during standing and walking by at least 16 and 19% respectively. Moreover, the optimum stiffness was strongly correlated to body mass (BM) and body mass index (BMI), with stiffer materials needed in the case of people with higher BM or BMI. Mechanical testing confirmed that optimum stiffness increases with the magnitude of compressive loading. For the first time, this study provides quantitative data to support the importance of stiffness optimisation in cushioning materials and sets the basis for methods to inform optimum material selection in the clinic.

Highlights

IntroductionThe redistribution of plantar loads to reduce plantar pressure is one of the main therapeutic objectives forEven though careful selection of stiffness of cushioning materials is highlighted as an imperative factor in order to achieve maximum pressure reduction, currently no set method exists to inform this selection process. material selection in the clinic is solely based on empirical or anecdotal evidence and no clear guidelines are available to enable healthcare professionals, working in the area of diabetic foot care, to decide whether a specific material is adequately ‘‘soft’’ or ‘‘stiff’’ on a patient specific basis.In this context, a recent numerical analysis aimed to shed light on the optimisation of stiffness of cushioning materials to minimise plantar pressure and to assess the effect of various patient specific parameters on optimum stiffness. the parameters that were investigated in this study were: (a) plantar soft tissue stiffness (b) plantar soft tissue thickness and (c) the magnitude of plantar loads
Even though careful selection of stiffness of cushioning materials is highlighted as an imperative factor in order to achieve maximum pressure reduction,6,9,20 currently no set method exists to inform this selection process
Comparison with the two commercial materials indicates that the range of stiffness of the bespoke polyurethane (BPU) materials is relevant to what is currently used in therapeutic footwear

Summary

Introduction

The redistribution of plantar loads to reduce plantar pressure is one of the main therapeutic objectives forEven though careful selection of stiffness of cushioning materials is highlighted as an imperative factor in order to achieve maximum pressure reduction, currently no set method exists to inform this selection process. material selection in the clinic is solely based on empirical or anecdotal evidence and no clear guidelines are available to enable healthcare professionals, working in the area of diabetic foot care, to decide whether a specific material is adequately ‘‘soft’’ or ‘‘stiff’’ on a patient specific basis.In this context, a recent numerical analysis aimed to shed light on the optimisation of stiffness of cushioning materials to minimise plantar pressure and to assess the effect of various patient specific parameters on optimum stiffness. the parameters that were investigated in this study were: (a) plantar soft tissue stiffness (b) plantar soft tissue thickness and (c) the magnitude of plantar loads. Material selection in the clinic is solely based on empirical or anecdotal evidence and no clear guidelines are available to enable healthcare professionals, working in the area of diabetic foot care, to decide whether a specific material is adequately ‘‘soft’’ or ‘‘stiff’’ on a patient specific basis In this context, a recent numerical analysis aimed to shed light on the optimisation of stiffness of cushioning materials to minimise plantar pressure and to assess the effect of various patient specific parameters on optimum stiffness.. Optimum insole stiffness appeared not to be affected by the stiffness or by the thickness of plantar soft tissue These findings highlighted patient specific loading as a possible critical factor to inform the selection of cushioning material stiffness.

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