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

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

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.

Keywords: Biomechanics; Clinical management; Diabetic foot; In vivo testing; Insole; Orthotic devices; Polyurethane foam; Pressure measurement; Shoe.

Figures

Figure 1
Figure 1
Stress (kPa)/strain (unitless) graphs for the bespoke polyurethane foam materials (BPU01-10) (a) and the two commercially ones (Poron®4000, AstroShock®) that were used as reference (b).
Figure 2
Figure 2
Testing set-up for investigating the effect of loading on the ability of cushioning materials to uniformly distribute plantar loads using a 3D printed heel model.
Figure 3
Figure 3
The relationship between externally applied net force and resulted peak pressure between the 3D printed heel model and different BPU materials. Results for three loading cycles are presented in each case. The 5th order polynomials that were fitted to the data are also shown.
Figure 4
Figure 4
The testing set-up (Top) and average pressure that was achieved by each material (bottom) during standing (left) and walking (right). Pressure reduction is averaged over ten participants.

References

    1. Ahroni JH, Boyko EJ, Forsberg RC. Clinical correlates of plantar pressure among diabetic veterans. Diabetes Care. 1999;22:965–972. doi: 10.2337/diacare.22.6.965.
    1. Arnold JB, Causby R, Pod GD, Jones S. The impact of increasing body mass on peak and mean plantar pressure in asymptomatic adult subjects during walking. Diabet. Foot Ankle. 2010
    1. Arts MLJ, Bus SA. Twelve steps per foot are recommended for valid and reliable in-shoe plantar pressure data in neuropathic diabetic patients wearing custom made footwear. Clin. Biomech. 2011;26:880–884. doi: 10.1016/j.clinbiomech.2011.05.001.
    1. Bishara AJ, Hittner JB. Testing the significance of a correlation with nonnormal data: comparison of Pearson, Spearman, transformation, and resampling approaches. Psychol. Methods. 2012;17:399–417. doi: 10.1037/a0028087.
    1. Bus SA, Maas M, de Lange A, Michels RPJ, Levi M. Elevated plantar pressures in neuropathic diabetic patients with claw/hammer toe deformity. J. Biomech. 2005;38:1918–1925. doi: 10.1016/j.jbiomech.2004.07.034.
    1. Campbell GJ, McLure M, Newell EN. Compressive behavior after simulated service conditions of some foamed materials intended as orthotic shoe insoles. J. Rehabil. Res. Dev. 1984;21:57–65.
    1. Cavanagh PR, Sims DS, Sanders LJ. Body mass is a poor predictor of peak plantar pressure in diabetic men. Diabetes Care. 1991;14:750–755. doi: 10.2337/diacare.14.8.750.
    1. Chatzistergos PE, Naemi R, Chockalingam N. A method for subject-specific modelling and optimisation of the cushioning properties of insole materials used in diabetic footwear. Med. Eng. Phys. 2015;37:531–538. doi: 10.1016/j.medengphy.2015.03.009.
    1. Cheung JT-M, Zhang M. Parametric design of pressure-relieving foot orthosis using statistics-based finite element method. Med. Eng. Phys. 2008;30:269–277. doi: 10.1016/j.medengphy.2007.05.002.
    1. De Clercq D, Aerts P, Kunnen M. The mechanical characteristics of the human heel pad during foot strike in running: an in vivo cineradiographic study. J. Biomech. 1994;27:1213–1222. doi: 10.1016/0021-9290(94)90275-5.
    1. Good P. Permutation, Parametric and Bootstrap Tests of Hypotheses. New York: Springer-Verlag; 2005.
    1. Healy A, Dunning DN, Chockalingam N. Materials used for footwear orthoses: a review. Footwear Sci. 2010;2:93–110. doi: 10.1080/19424280.2010.486045.
    1. Healy A, Naemi R, Chockalingam N. The effectiveness of footwear and other removable off-loading devices in the treatment of diabetic foot ulcers: a systematic review. Curr. Diabetes Rev. 2014;10:215–230. doi: 10.2174/1573399810666140918121438.
    1. Lo WT, Yick KL, Ng SP, Yip J. New methods for evaluating physical and thermal comfort properties of orthotic materials used in insoles for patients with diabetes. J. Rehabil. Res. Dev. 2014;51:311–324. doi: 10.1682/JRRD.2013.01.0012.
    1. Nicolopoulos CS, Black J, Anderson EG. Foot orthoses materials. Foot. 2000;10:1–3. doi: 10.1054/foot.1999.0531.
    1. Paton J, Glasser S, Collings R, Marsden J. Getting the right balance: insole design alters the static balance of people with diabetes and neuropathy. J. Foot Ankle Res. 2016;9:40. doi: 10.1186/s13047-016-0172-3.
    1. Petre MT, Erdemir A, Cavanagh PR. Determination of elastomeric foam parameters for simulations of complex loading. Comput. Methods Biomech. Biomed. Eng. 2006;9:231–242. doi: 10.1080/10255840600747620.
    1. Pirozzi K, McGuire J, Meyr AJ. Effect of variable body mass on plantar foot pressure and off-loading device efficacy. J. Foot Ankle Surg. 2014;53:588–597. doi: 10.1053/j.jfas.2014.02.005.
    1. Sadeghi H, Allard P, Prince F, Labelle H. Symmetry and limb dominance in able-bodied gait: a review. Gait. Posture. 2000;12:34–45. doi: 10.1016/S0966-6362(00)00070-9.
    1. Shurr D, Cook TM. Methods, materials, and mechanics. In: Shurr D, Cook TM, editors. Prosthetics & Orthotics. Upper Saddle River: Prentice Hall; 1990. pp. 17–29.
    1. Sun P, Wei H, Chen C, Wu C, Kao H, Cheng C. Effects of varying material properties on the load deformation characteristics of heel cushions. Med. Eng. Phys. 2008;30:687–692. doi: 10.1016/j.medengphy.2007.07.010.
    1. Wafai L, Zayegh A, Woulfe J, Aziz SM, Begg R. Identification of foot pathologies based on plantar pressure asymmetry. Sensors (Basel). 2015;15:20392–20408. doi: 10.3390/s150820392.
    1. Wit B, De Clercq D, Lenoir M. The effect of varying midsole hardness on impact forces and foot motion during foot contact in running. J. Appl. Biomech. 1995;11:395–406. doi: 10.1123/jab.11.4.395.

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