Application of an image-based weighted measure of skeletal bending stiffness to great ape mandibles
Version of Record online: 4 APR 2006
Copyright © 2006 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 131, Issue 2, pages 243–251, October 2006
How to Cite
Bhatavadekar, N. B., Daegling, D. J. and Rapoff, A. J. (2006), Application of an image-based weighted measure of skeletal bending stiffness to great ape mandibles. Am. J. Phys. Anthropol., 131: 243–251. doi: 10.1002/ajpa.20397
- Issue online: 23 AUG 2006
- Version of Record online: 4 APR 2006
- Manuscript Accepted: 9 NOV 2005
- Manuscript Received: 11 MAR 2005
- bone density;
- computed tomography;
- image analysis;
- moment of inertia
Traditional measures of structural stiffness in the primate skeleton do not consider the heterogeneous material stiffness distribution of bone. This assumption of homogeneity introduces an unknown degree of error in estimating stiffness in skeletal elements. Measures of weighted stiffness can be developed by including heterogeneous grayscale variations evident in computed tomographic (CT) images. Since gray scale correlates with material stiffness, the distribution of bone quality and quantity can be simultaneously considered. We developed weighted measures of bending resistance and applied these to CT images at three locations along the mandibular corpus in the hominoids Gorilla, Pongo, and Pan. We calculated the traditional (unweighted) moment of inertia for comparison to our weighted measure, which weighs each pixel by its gray-scale value. This weighing results in assignment of reduced moment of inertia values to sections of reduced density. Our weighted and unweighted moments differ by up to 22%. These differences are not consistent among sections, however, such that they cannot be calculated by simple correction of unweighted moments. The effect of this result is that the rank ordering of individual sections within species changes if weighted moments are considered. These results suggest that the use of weighted moments may spur different interpretations of comparative data sets that rely on stiffness measures as estimates of biomechanical competence. Am J Phys Anthropol 131:243–251, 2006. © 2006 Wiley-Liss, Inc.