A new method for quantifying the complexity of muscle attachment sites

Abstract

Muscle attachment site morphology may have valuable use for reconstructing activity patterns in individuals from historic populations or extinct species. The skeletal locations where muscles and tendons attach are morphologically very complex, and variations in this morphology may reflect stresses experienced by these attachment sites as a result of muscular contractions. However, existing methods for assessing attachment site complexity are qualitative and subjective. This article describes a new method for quantifying attachment site complexity in which attachment sites are scanned with a 3D laser scanner and the morphological complexities of their surfaces are quantified using fractal analysis. The method described here documents the complexity at specific transects along six limb attachment sites in adult female sheep (Ovis aries), and variations in complexity within attachment sites are explored. Overall trends indicate that most of the attachment sites examined here are more complex at their peripheries than at their centers, indicating that these sites experience more varied loads at the peripheries of the tendon attachments. Exceptions to this trend are noted and all functional implications are discussed. This method provides the first opportunity to explore variations in morphological complexity within attachment sites. Assuming a relationship between tensile strains and bony morphology exists, this method provides a new tool to explore the strain environments of muscle attachment sites.