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Technical Briefs

# The Contribution of the Perichondrium to the Structural Mechanical Behavior of the Costal-Cartilage

[+] Author and Article Information
Jason L. Forman

Center for Applied Biomechanics, University of Virginia, 1011 Linden Avenue, Charlottesville, VA 22902jlf3m@virginia.edu

Eduardo del Pozo de Dios

European Center for Injury Prevention, University of Navarra School of Medicine, Irunlarrea 1 (Investigation Building 2290), 31008 Pamplona, Navarra, Spainedelpozod@unav.es

Carlos Arregui Dalmases

European Center for Injury Prevention, University of Navarra School of Medicine, Irunlarrea 1 (Investigation Building 2290), 31008 Pamplona, Navarra, Spaincarlosarregui@unav.es

Richard W. Kent

Center for Applied Biomechanics, University of Virginia, 1011 Linden Avenue, Charlottesville, VA 22902rwk3c@virginia.edu

J Biomech Eng 132(9), 094501 (Aug 26, 2010) (5 pages) doi:10.1115/1.4001976 History: Received January 11, 2010; Revised May 24, 2010; Posted June 14, 2010; Published August 26, 2010; Online August 26, 2010

## Abstract

The costal-cartilage in the human ribcage is a composite structure consisting of a cartilage substance surrounded by a fibrous, tendonlike perichondrium. Current computational models of the human ribcage represent the costal-cartilage as a homogeneous material, with no consideration for the mechanical contributions of the perichondrium. This study sought to investigate the role of the perichondrium in the structural mechanical behavior of the costal-cartilage. Twenty-two specimens of postmortem human costal-cartilage were subjected to cantileveredlike loading both with the perichondrium intact and with the perichondrium removed. The test method was chosen to approximate the cartilage loading that occurs when a concentrated, posteriorly directed load is applied to the midsternum. The removal of the perichondrium resulted in a statistically significant (two-tailed Student’s t-test, $p≤0.05$) decrease of approximately 47% (95% C.I. of 35–58%) in the peak anterior-posterior reaction forces generated during the tests. When tested with the perichondrium removed, the specimens also exhibited failure in the cartilage substance in the regions that experienced tension from bending. These results suggest that the perichondrium does contribute significantly to the stiffness and strength of the costal-cartilage structure under this type loading, and should be accounted for in computational models of the thorax and ribcage.

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## Figures

Figure 5

An illustration of the typical failure that occurred in the tests with the perichondrium removed. Top: A specimen tested with the perichondrium intact (shown with the sternum displaced). Bottom: The same specimen tested with the perichondrium removed.

Figure 4

Average normalized peak forces (with 95% confidence intervals). A value of one indicates no difference between the initial, perichondrium-intact tests and either the repeated or the perichondrium-removed tests. The asterisk indicates an average value significantly different than 1 (p<0.05).

Figure 3

Illustration of the orientation of the specimen and the directions of the applied displacement and the measured reaction force

Figure 2

Pictures of a typical specimen installed in the test fixture. Top: specimen installed prior to loading. Bottom: the same specimen with the sternum displaced posteriorly.

Figure 1

Images of the costal-cartilage with the perichondrium intact (top left), the costal-cartilage with the perichondrium removed (top right), and a view of the thickness of the perichondrium (bottom)

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