Heel skin stiffness effect on the hind foot biomechanics during heel strike

Gu, Yaodong<sup>1,2</sup>; Li, Jianshe<sup>1</sup>; Ren, Xuejun<sup>2</sup>; Lake, Mark J.<sup>3</sup>; Zeng, Yanjun<sup>4</sup>

Affiliations

¹Human Movement Research Center, Zhejiang College of Sports, Zhejiang, China

²School of Engineering, Liverpool John Moores University, Liverpool, UK

³School of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK

⁴Biomedical Engineering Center, Beijing University of Technology, Beijing, China

Abstract and keywords

Background: The human heel pad is a complex biological structure consisting of the fat pad and the skin. The mechanical properties of the skin layer are of significant importance to the load-bearing function of the heel pad and human locomotion. The condition of the heel skin is also directly associated with some medical conditions such as heel ulcers that may become a site for the skin breakdown, which is the most common precursor to lower extremity amputation among persons with diabetes. It is essential to develop a detailed understanding of the properties of the heel skin layer and its effect on hind foot biomechanics during heel strike.

Objectives: This work aims to gain a better insight into the biomechanical behaviour of the heel skin layer through a combined experimental and numerical study. The main objective is to characterise the biomechanical responses of the hind foot system during heel strike with potential variation of the skin stiffness based on a subject-specific finite element (FE) model and biomechanical testing.

Methods: A three-dimensional (3D) FE model of the human hind foot incorporating a separate heel skin layer was developed based on subject-specific medical images. An inverse FE analysis of the in vivo indentation test was carried out to study the nonlinear material property of the heel skin. The FE model was then used to study the deformation of the hind foot during heel strike in comparison with the plantar pressure measurement results and to establish the effects of stiffness of the heel skin on the stress and pressure distributions.

Results: The FE foot model with subject-specific heel skin properties was successfully used to predict the deformation of the hind foot during heel strike, and the results showed good agreements with biomechanical pressure measurements. The results showed that the high pressure and stress in the heel skin appeared in the centre region during a heel strike. Heel skin stiffness sensitivity studies showed that an increase in the skin stiffness had a limited effect on the stress and contact pressure of the hind foot bones, but caused a slight increase in the skin stresses, while skin softening caused a decrease in the peak plantar pressure and its distribution pattern changed. In addition, the results also suggest that skin softening may cause a higher stress level in the bones and ligaments.

Conclusion: The nonlinear parameter of the heel skin has been successfully predicted from in vivo indentation tests based on a subject-specific FE model. Skin properties' sensitivity tests clearly showed that the stiffness of the heel skin could have a direct effect on the biomechanics of the hind foot. The results suggest that individuals with a pathologically stiffened heel skin could exert an increase in the heel pressure, which may potentially lead to skin breakdown or ulcer.

Keywords: heel pad skin; properties; plantar pressure; heel strike; ulcer

Links

DOI: 10.1111/j.1600-0846.2010.00425.x

PubMed: 20636997

WoS: 000279452600006

History

Accepted: 2010-01-23

Online: 2010-04-14

Cited Works (9)

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Cited By (4)

Year	Entry
2017	Butz K, Spurlock C, Roy R, Bell C, Barrett P, Ward A, Xiao X, Shirley A, Welch C, Liste K. Development of the CAVEMAN human body model: validation of lower extremity sub-injurious response to vertical accelerative loading. Stapp Car Crash J. November 2017;61:175-209. SAE 2017-22-0006.
2016	Morales-Orcajo E, Bayod J, Barbosa de Las Casas E. Computational foot modeling: scope and applications. Arch Comput Methods Eng. September 2016;23(3):389-416.
2012	Chokhandre S, Halloran JP, van den Bogert AJ, Erdemir A. A three-dimensional inverse finite element analysis of the heel pad. J Biomech Eng. March 2012;134(3):031002.
2012	Fontanella CG, Matteoli S, Carniel EL, Wilhjelm JE, Virga A, Corvi A, Natali AN. Investigation on the load-displacement curves of a human healthy heel pad: in vivo compression data compared to numerical results. Med Eng Phys. November 2012;34(9):1253-1259.