Bilateral Directional Assymetry in the Human Clavicle

Abstract

This study investigates bilateral directional asymmetry (BDA) in the human clavicle using the McCormick Collection, a documented autopsy sample from 1986–98 autopsies in East Tennessee (n=1125). BDA has been examined extensively in the human skeleton, especially limb bones. Most of these studies rely on comparisons of metric measurements typically used in skeletal analyses. While most of these measurements are thought to reflect mechanically relevant morphologies, these dimensions may not reflect the most morphologically asymmetrical areas. In an effort to holistically address BDA, this study examines standard metric measurements on the entire sample, conducts a curvature analysis of the medial axis on a subset (n=33) of 3D models developed from CT scans using statistical atlases, and examines the average surface‐to‐surface differences of this subset of modeled clavicles. In males and females, mean length of the left clavicle is significantly greater than the right (α=.05). Furthermore, maximum midshaft diameter is significantly greater in the right clavicle than in the left. All p‐values are more significant in males than in females. Shape analyses indicate that magnitudes of greatest difference between the left and right surface models occur at muscle attachment sites. These preliminary results point to a strong biomechanical influence on BDA in the human clavicle in both sexes, particularly males.