The effect of heel-pad thickness and loading protocol on measured heel-pad stiffness and a standardized protocol for inter-subject comparability

Spears, Iain R.; Miller-Young, Janice

doi:10.1016/j.clinbiomech.2005.09.017

Cited by 39 publications

(37 citation statements)

References 12 publications

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“…For example, it was reported that the stiffness of the heel pad of humans using in vitro method is almost six times higher compared to the stiffness measured during in vivo tests, while the absorbed energy ratio is about three times lower using the in vitro method [40]. This can be explained by the indications that structural factors such as heel pad thickness and geometry of the calcaneus have a significant influence on the heel pad mechanical behaviour [3,23,56]. Aerts et al [40] compared the energy dissipation and stiffness of the soft tissue in an amputated leg and in an isolated heel pad.…”

Section: Plantar Soft Tissue Stiffness and Measurement Methodsmentioning

confidence: 84%

Viscoelasticity in Foot-Ground Interaction

Naemi¹,

Behforootan²,

Chatzistergos³

et al. 2016

Viscoelastic and Viscoplastic Materials

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Mechanical properties of the plantar soft tissue, which acts as the interface between the skeleton and the ground, play an important role in distributing the force underneath the foot and in influencing the load transfer to the entire body during weight-bearing activities. Hence, understanding the mechanical behaviour of the plantar soft tissue and the mathematical equations that govern such behaviour can have important applications in investigating the effect of disease and injuries on soft tissue function. The plantar soft tissue of the foot shows a viscoelastic behaviour, where the reaction force is not only dependent on the amount of deformation but also influenced by the deformation rate. This chapter provides an insight into the mechanical behaviour of plantar soft tissue during loading with specific emphasis on heel pad, which is the first point of contact during normal gait. Furthermore, the methods of assessing the mechanical behaviour including the in vitro/in situ and in vivo are discussed, and examples of creep, stress relaxation, rate dependency and hysteresis behaviour of the heel pad are shown. In addition, the viscoelastic models that represent the mechanical behaviour of the plantar soft tissue under load along with the equations that govern this behaviour are elaborated and discussed.

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Section: Plantar Soft Tissue Stiffness and Measurement Methodsmentioning

confidence: 84%

Viscoelasticity in Foot-Ground Interaction

Naemi¹,

Behforootan²,

Chatzistergos³

et al. 2016

Viscoelastic and Viscoplastic Materials

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“…There is an increasing awareness that pathological conditions such as plantar heel pain or diabetic foot are associated with changes in the mechanical behaviour of plantar soft tissue (Hsu et al, 2007(Hsu et al, , 2000(Hsu et al, , 2002Klaesner et al, 2002;Spears and Miller-Young, 2006;Zheng YP, Choi YK et al, 2000). Therefore, quantifying the mechanical properties of plantar soft tissue has been an exciting and evolving topic for the past few years.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed existing results based on in vivo investigations vary significantly between studies even in the case of populations with no-known musculoskeletal pathology or diabetes (Spears and Miller-Young, 2006). This scattering of results can significantly compromise the value of ultrasound indentation data in comparative studies between different populations.…”

Section: Introductionmentioning

confidence: 99%

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A clinically applicable non-invasive method to quantitatively assess the visco-hyperelastic properties of human heel pad, implications for assessing the risk of mechanical trauma

Behforootan

Chatzistergos

Chockalingam

et al. 2017

Journal of the Mechanical Behavior of Biomedical Materials

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Cite this article as: Sara Behforootan, Panagiotis E. Chatzistergos, Nachiappan Chockalingam and Roozbeh Naemi, A clinically applicable non-invasive method to quantitatively assess the visco-hyperelastic properties of human heel pad with implications for assessing the risk of mechanical trauma, Journal of the Mechanical Behavior of Biomedical Materials, http://dx.doi.org/10.1016Materials, http://dx.doi.org/10. /j.jmbbm.2017 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Purpose: To develop a clinically viable non-invasive method of assessing the mechanical properties of the heel pad. Furthermore the effect of non-linear mechanical behaviour of the heel pad on its ability to uniformly distribute foot-ground contact loads in light of the effect of overloading is also investigated. Methods:An automated custom device for ultrasound indentation was developed along with custom algorithms for the automated subject specific modeling of heel pad. Non-time-dependent and time-dependent material properties were inverse engineered from results from quasistatic indentation and stress relaxation test respectively. The validity of the calculated coefficients was assessed for five healthy participants. The implications of altered mechanical properties on the heel pad's ability to uniformly distribute plantar loading were also investigated in a parametric analysis. Results:The subject specific heel pad models with coefficients calculated based on quasi-static indentation and stress relaxation were able to accurately simulate dynamic indentation.Average error in the predicted forces for maximum deformation was only 6.6 ± 4.0%. When the inverse engineered coefficients were used to simulate the first instance of heel strike the error in terms of peak plantar pressure was 27%. The parametric analysis indicated that the heel pad's ability to uniformly distribute plantar loads is influenced both by its overall deformability and by its stress/ strain behaviour. When overall deformability stays constant, changes in stress/strain behaviour leading to a more "linear" mechanical behaviour appear to improve the heel pad's ability to uniformly distribute plantar loading. Conclusions:The developed technique can accurately assess the visco-hyperelastic behaviour of heel pad. It was observed that specific change in stress-strain behaviour can enhance/weaken the heel pad's ability to uniformly distribute plantar loading that will increase/decrease the risk for overloading and trauma.

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“…Heel pain is common and its pathology is predominantly mechanical (Thomas et al 2010). Body weight, compressibility index and the thickness of the PFP are recognized as factors that are relevant to heel pain (Prichasuk, 1994;Yi et al 2011), although how precisely those factors contribute to the foot pathology is still a subject of debate (Spears & Miller-Young, 2006). Persistent heel pain appears in patients older than 40 and is associated with reduced elasticity of heel pad (Ozdemir et al 2004).…”

Section: Introductionmentioning

confidence: 99%

A stereologic study of the plantar fat pad in young and aged rats

Molligan

Schon

2013

Journal of Anatomy

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Plantar fat pad (PFP) is a tissue structure that absorbs the initial impact of walking and running and ultimately bears body weight at standing. This study was designed to quantify the histomorphological changes of the PFP in aged rats. The most medial PFP was dissected from the hind feet of young rats (4 months old, n = 6) and aged rats (24 months old, n = 6). Histological structure and cellular senescence of PFP were analyzed stereologically and histomorphometrically. Immunohistochemistry of matrix metalloproteinase 9 (MMP9) was also performed on PFP tissue sections. Compared with young rats, the thickness of epidermis, dermis and septa of the PFP were significantly reduced in the aged rats. The total volume of adipose tissue in the PFP of aged rats was only about 65% of that in the young rats. The microvascular density and the number of fat pad units (FPU), a cluster of adipocytes enclosed by elastin septa, in the PFP were unchanged in the aged rats. In the aged rats, the number of adipocytes per FPU was reduced but the number of simple adipocyte clusters, without surrounding septa, was increased. The shift of the types of adipocyte clusters in the aged PFP was accompanied by degradation of elastin fibers and increased expression of MMP9. In conclusion, the PFP, particularly the elastic septa, degenerates significantly in aged rats and this may contribute to the pathology of PFP-related diseases.

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The effect of heel-pad thickness and loading protocol on measured heel-pad stiffness and a standardized protocol for inter-subject comparability

Cited by 39 publications

References 12 publications

Viscoelasticity in Foot-Ground Interaction

Viscoelasticity in Foot-Ground Interaction

A clinically applicable non-invasive method to quantitatively assess the visco-hyperelastic properties of human heel pad, implications for assessing the risk of mechanical trauma

A stereologic study of the plantar fat pad in young and aged rats

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