3D Muscle Architecture of the Pectoral Muscles of European Starling (Sturnus vulgaris)

S.P. Sullivan, F.R. McGechie, K.M. Middleton, C.M. Holliday - Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, USA;

Avian flight is achieved through a number of modifications to the body, including the pectoral girdle (…). Muscle architecture is a critical variable in determining the biomechanical function of the vertebrate musculoskeletal system; however, accurate three-dimensional (3D) understanding of muscle architecture has been historically difficult to acquire. Here, we present a musculoskeletal model of a European starling (Sturnus vulgaris) pectoral girdle generated from iodine contrast-enhanced micro-computed-tomography (CT) data and 3D fiber tracking analysis. We used a template-based fiber-tracking algorithm to reconstruct muscle fibers in 3D based on grayscale differences in CT images, which allowed us to estimate fascicle lengths, pennation angles, muscle volumes, and physiological cross-sectional area. (…) digital fiber tracking offers numerous advantages over gross-dissection methods, most importantly, the ability to visualize and quantify entire muscles in three-dimensions, yielding a much more accurate estimation of whole muscle architecture.

How Amira-Avizo Software is used

All microCT images were imported as .tiff files into Avizo 9.4 for segmentation. (…) We used the Avizo 9 extension, Xfiber, to reconstruct shoulder muscle architecture from the contrast-enhanced CT data (…) We digitally reconstructed starling pectoral and shoulder musculature with an emphasis on the use of Avizo Xfiber to model muscle architecture from DiceCT data. We found that Xfiber’s template-based fiber-tracking algorithm produced plausible models of muscle architecture, comparable to dissection-based methods, despite our specimen’s storage history.