A Three-Dimensional Analysis of Bilateral Directional Asymmetry in the Human Clavicle

• NCJ Number: 255362
• Journal: American Journal of Physical Anthropology Volume: 149 Issue: 4 Dated: 2012 Pages: 547-559
• Author(s): E. E. Abdel Fatah; N. R. Shirley; M. R. Mahfouz; B. M. Auerbach
• Date Published: 2012
• Length: 13 pages
• Grant Number(s): 2007-DN-BX-0004
• Agencies: NIJ-Sponsored
• Award: Determination of Age and Sex from the Human Clavicle: A Geometric Morphometric Approach

Annotation

This study presents a novel three‐dimensional analysis that uses statistical atlases and automated measurements to assess diaphyseal morphology of the clavicle and its relationship to muscle asymmetry. 

Abstract

A sample of 505 individuals (285 males, 220 females) from the William McCormick Clavicle Collection was CT scanned, segmented, and added to a statistical bone atlas that captures correspondence between homologous points on the bone surfaces. Muscle attachment sites were localized on the atlas and then propagated across the entire population. Cross‐sectional contours were extracted at 5-percent increments along the entire bone, as well as at muscle attachment sites and the clavicle waist; maximum and minimum dimensions of each cross‐sectional contour were calculated. In addition, the entire three‐dimensional surface was examined for asymmetry by analyzing the magnitude and directional differences between homologous points across all bone surfaces in the dataset. These results confirm the existing studies on clavicle asymmetry, namely that the left clavicle is longer than the right, but the right is more robust than the left; however, the patterns of asymmetry are sexually dimorphic. Males are significantly asymmetric in all dimensions and at muscle and ligament attachment sites (P < 0.05); whereas female asymmetry is more variable. The authors hypothesize that this is related to absolute and relative differences in male muscle strength compared to females; however, an area with no muscle attachments on the posterior midshaft was significantly asymmetric in both sexes. The authors suggest that this is a curvature difference caused by opposing muscle actions at the medial and lateral ends of the bone. (publisher abstract modified)