Research Papers

The Use of External Transducers for Estimating Bone Strain at the Distal Tibia During Impact Activity

[+] Author and Article Information
W. Brent Edwards1

Department of Kinesiology, Iowa State University, Ames, IA 50011edwards9@iastate.edu

Erin D. Ward

 Central Iowa Foot Clinic, Perry, IA 50220

Stacey A. Meardon, Timothy R. Derrick

Department of Kinesiology, Iowa State University, Ames, IA 50011


Corresponding author.

J Biomech Eng 131(5), 051009 (Apr 14, 2009) (6 pages) doi:10.1115/1.3118762 History: Received July 19, 2007; Revised January 02, 2009; Published April 14, 2009

Noninvasive methods for monitoring the in vivo loading environment of human bone are needed to determine osteogenic loading patterns that reduce the potential for bone injury. The purpose of this study was to determine whether the vertical ground reaction impact force (impact force) and leg acceleration could be used to estimate internal bone strain at the distal tibia during impact activity. Impact loading was delivered to the heels of human-cadaveric lower extremities. The effects of impact mass and contact velocity on peak bone strain, impact force, leg acceleration, and computed impact force (legaccelerationimpactmass) were investigated. Regression analysis was used to predict bone strain from six different models. Apart from leg acceleration, all variables responded to impact loading similarly. Increasing impact mass resulted in increased bone strain, impact force, and computed impact force, but decreased leg acceleration. The best models for bone strain prediction included impact force and tibial cross-sectional area (R2=0.94), computed impact force and tibial cross-sectional area (R2=0.84), and leg acceleration and tibial cross-sectional area (R2=0.73). Results demonstrate that when attempting to estimate bone strain from external transducers some measure of bone strength must be considered. Although it is not recommended that the prediction equations developed in this study be used to predict bone strain in vivo, the strong relationship between bone strain, impact force, and computed impact force suggested that force platforms and leg accelerometers can be used for a surrogate measure of bone strain.

Copyright © 2009 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 3

Actual bone strain versus predicted bone strain for the six regression models. The dashed line at 45 deg represents a theoretical line of perfect prediction.

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Figure 2

Typical impact force, leg acceleration, and bone strain profiles during impact. The bone strain profile has a negative value indicating a compressive strain.

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Figure 1

Impact tester and instrumentation



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