Technical Briefs

An Elaborate Data Set Characterizing the Mechanical Response of the Foot

[+] Author and Article Information
Ahmet Erdemir1

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195; Computational Biomodeling Core, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195erdemira@ccf.org

Pavana A. Sirimamilla

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195; Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106

Jason P. Halloran, Antonie J. van den Bogert

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195



Corresponding author.

J Biomech Eng 131(9), 094502 (Aug 05, 2009) (6 pages) doi:10.1115/1.3148474 History: Received March 13, 2009; Revised April 29, 2009; Published August 05, 2009

Mechanical properties of the foot are responsible for its normal function and play a role in various clinical problems. Specifically, we are interested in quantification of foot mechanical properties to assist the development of computational models for movement analysis and detailed simulations of tissue deformation. Current available data are specific to a foot region and the loading scenarios are limited to a single direction. A data set that incorporates regional response, to quantify individual function of foot components, as well as the overall response, to illustrate their combined operation, does not exist. Furthermore, the combined three-dimensional loading scenarios while measuring the complete three-dimensional deformation response are lacking. When combined with an anatomical image data set, development of anatomically realistic and mechanically validated models becomes possible. Therefore, the goal of this study was to record and disseminate the mechanical response of a foot specimen, supported by imaging data. Robotic testing was conducted at the rear foot, forefoot, metatarsal heads, and the foot as a whole. Complex foot deformations were induced by single mode loading, e.g., compression, and combined loading, e.g., compression and shear. Small and large indenters were used for heel and metatarsal head loading, an elevated platform was utilized to isolate the rear foot and forefoot, and a full platform compressed the whole foot. Three-dimensional tool movements and reaction loads were recorded simultaneously. Computed tomography scans of the same specimen were collected for anatomical reconstruction a priori. The three-dimensional mechanical response of the specimen was nonlinear and viscoelastic. A low stiffness region was observed starting with contact between the tool and foot regions, increasing with loading. Loading and unloading responses portrayed hysteresis. Loading range ensured capturing the toe and linear regions of the load deformation curves for the dominant loading direction, with the rates approximating those of walking. A large data set was successfully obtained to characterize the overall and the regional mechanical responses of an intact foot specimen under single and combined loads. Medical imaging complemented the mechanical testing data to establish the potential relationship between the anatomical architecture and mechanical responses and to further develop foot models that are mechanically realistic and anatomically consistent. This combined data set has been documented and disseminated in the public domain to promote future development in foot biomechanics.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

(a) The foot specimen used for mechanical testing and anatomical imaging. (b) A cross-sectional image at the level of mid metatarsals as obtained from computed tomography. ((c) and (d)) Volumetric reconstruction of computed tomography scans for the foot boundary and the bones.

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Figure 2

(a) Experimental setup illustrating assembly of all testing components and the foot, with their associated right-handed coordinate systems (R: robot; P: platform; T: tool; L: load cell; M: Microscribe three-dimensional digitizer (Immersion Corp., San Jose, CA)). (b) Anatomical landmarks digitized on the foot in relation to load cell coordinate system. This coordinate system was used to report foot loading and tool movement data.

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Figure 3

Time history of foot loading and tool movements presented in the load cell coordinate system. Loading corresponds to reaction forces and moments recorded at the origin of the load cell coordinate system. Kinematics describes the position and orientation of the tool coordinate system relative to the load cell coordinate system. (a) Rear foot compression and shear using the elevated platform. (b) Indentation of the second metatarsal head region using a small indenter (12.7 mm diameter).

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Figure 4

Reaction forces against tool position. This representation of data from rear foot compression and shear, as applied by the elevated platform, points out the nonlinear nature of foot deformation characteristics. Hysteresis is noticeable as illustrated by the differences in loading and unloading patterns. Tool movement in the shear direction was applied at a fixed tool position in the compression direction. Reaction moments and tool orientation were not shown since tool orientation was kept constant during the test. All data were represented in the load cell coordinate system.

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Figure 5

Tool trajectories overlayed on volumetric reconstruction of computed tomography data. Paths of the large indenter (25.4 mm diameter) during rear foot compression and shear and the small indenter (12.7 mm diameter) during compression of the first metatarsal head region are illustrated. Registration between mechanical testing data and computed tomography scans was accomplished using anatomical landmarks measured during robotic testing and extracted from images as well.



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