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Research Papers

Load Transfer Mechanism for Different Metatarsal Geometries: A Finite Element Study

[+] Author and Article Information
J. M. García-Aznar, J. Bayod, A. Rosas, M. Doblaré

Group of Structural Mechanics and Materials Modelling, Aragón Institute of Engineering Research (I3A), University of Zaragoza, Zaragoza 50018, Spain; Centro de Investigación Biomédica en red en Bioingeniería, Biomateriales y Medicina (CIBER-BBN) María de Luna, 11. CEEI-Módulo 3, Zaragoza 50018, Spain

R. Larrainzar, R. García-Bógalo, L. F. Llanos

 Servicio de Traumatología I, Hospital Universitario 12 de Octubre, Madrid 28026, Spain

J Biomech Eng 131(2), 021011 (Dec 10, 2008) (7 pages) doi:10.1115/1.3005174 History: Received October 24, 2007; Revised July 16, 2008; Published December 10, 2008

The load transfer mechanism across the skeleton of the human foot is very important to understand its biomechanical function. In this work, we develop several computational models to compare the biomechanical response of different metatarsal geometries. Finite element 3D simulations of feet reconstructed from computer tomography (CT) scans were used to evaluate the stress/strain distributions during the stance posture. The numerical predictions for pathological and healthy foot geometries present different load transfer mechanisms that can provide a biomechanical explanation of why some metatarsal geometrical configurations cause different foot skeletal stresses. The most significant result in all cases was a reduction between 20% and 30% of the peak load supported by the first metatarsal. Therefore, we conclude that a clearly unloaded first metatarsal, overloading the rest, is a risk factor to induce metatarsalgia.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

FE mesh of one metatarsal in which cortical (left) and trabecular (right) bones are distinguished

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Figure 2

FE model reconstruction of the foot: (a) frontal view, (b) lateral low view of the ligaments plantar fascia and deep and superficial LPL, (c) top view, and (d) low view

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Figure 3

F1 corresponds to the force applied at the talus, while F2 is the force at the Achilles’ heel

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Figure 4

Measurements and angles of the foot geometry in the different cases analyzed: (1) initial case, (2) parabola 8deg of Maestro (5,1), (3) symptomatic 12deg, and (4) symptomatic 8deg

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Figure 5

Deformed shape of the foot (amplification factor of 20) in dark and original geometry of the foot in light gray: (left) distinguishing between cortical and trabecular bones and (right) bone modeled as a homogeneous material

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Figure 6

Maximum principal stress distribution: (left) homogeneous material and (right) piecewise homogeneous material distinguishing between cortical and trabecular bones

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Figure 7

Maximum principal stress distribution in the foot bones corresponding to the parabola (MP8) of Maestro (5,1)

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Figure 8

Maximum principal stress distribution in the foot bones corresponding to symptomatic feet (S12) and (S8)

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Figure 9

Formula of Maestro (5,1) by permission of L. S. Baruk

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