Comprehensive 3D Architecture of the Adult Human Trapezius: A Cadaveric Study
Authors: Stiver Mikaela L , Käärid Kaija , Kumbhare Dinesh , Agur Anne 
Published: June 2021

Musculoaponeurotic architecture describes the 3D arrangement of the contractile and connective tissue elements within a muscle, or functional partitions thereof. Without a comprehensive appreciation of these features, the certainty with which clinicians may interpret musculoskeletal imaging, assess pathology, and evaluate recovery associated with these muscles is inherently restricted. Current musculoaponeurotic literature is limited by insufficient fibre bundle (FB) sampling, lack of data regarding connective tissue elements, and 2D measurement approaches for 3D parameters. Morphometrically‐complex muscles, like trapezius, are particularly susceptible to overgeneralization using these approaches. A thorough understanding of the contractile and connective tissues of trapezius may help elucidate the etiology and pathophysiology of musculoskeletal disorders associated with this muscle. Accordingly, the primary objective of this study was to capture, quantify, and model the comprehensive 3D musculoaponeurotic architecture of the adult human trapezius muscle from cadaveric data.Ten trapezius muscles from five lightly embalmed cadavers (3F, 2M; ages 64–85 years) were meticulously dissected for this study. Contractile tissue elements were serially digitized in situ at the FB level with a MicroScribe® G digitizer and modelled in Autodesk® Maya®. The surfaces of connective tissue elements (i.e. aponeuroses) were digitized in a grid pattern and integrated into 3D musculoaponeurotic models. Architectural parameters, including FB length, pennation angle, and physiological cross‐sectional area (PCSA), were quantified for the whole muscle and each functional partition (ascending, transverse, and descending).Each trapezius muscle included a minimum of 1000 FBs. Preliminary data analyses reveal consistent patterns of relative mean FB length (ascending = descending > transverse), range of FB lengths (ascending > descending > transverse), and PCSA (transverse > ascending > descending). FBs throughout the muscle volume span between independent medial and lateral aponeuroses, resulting in extensive regions of musculoaponeurotic junction. Aponeuroses are notably substantial in the medial transverse and lateral ascending partitions, while the clavicular attachment of the descending partition had minimal connective tissue present.This study presents a comprehensive 3D model of the adult human trapezius that provides a foundation for improved longitudinal assessment of pathology and continuing clinical education. Future studies will use these data to guide in vivo imaging and functional electromyographic studies investigating musculoskeletal disorders associated with trapezius, such as myofascial pain syndrome.Support or Funding InformationSponsored by a Vanier Canada Graduate Scholarship from CIHR and an Educational Advancement Stipend from the University Health Network.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.