Prototype 3‐D Model of the Musculotendinous Architecture of Infraspinatus

Muscle architecture, the arrangement of fibre bundles within the muscle volume, has important functional implications. Previous studies of infraspinatus (IS) muscle architecture have focused on dissection and photography of the superficial muscle layers rather than a volumetric analysis. The aim of this study was to develop a methodology to quantify the architectural parameters of the fibre bundles throughout the volume of IS. As a prototype, one formalin‐embalmed cadaveric specimen was used. The IS was exposed and each fibre bundle was meticulously dissected and digitized from end to end. The digitized data was imported and a 3D model of the fibre bundle architecture, as in situ , was constructed in Autodesk ® Maya ® 2012. Architectural parameters including fibre bundle length (FBL), pennation angle (PA), and physiological cross sectional area (PCSA) were computed. Based on the architectural parameters, muscular partitioning was determined. This technique successfully captured IS architecture throughout its volume. The IS was found to consist of 2 architecturally distinct regions, superior and inferior. The average measures for the superior and inferior regions were respectively: FBL 115.3mm; PA 22.2 ° ; PCSA 180.3mm 2 and FBL 84.9 mm; PA 15.9 ° ; PCSA 550.5 mm 2 . The results suggest that there is muscular partitioning of the IS. This methodology will form the basis of a continuing study to understand detailed IS architecture at the fibre bundle level.