Mapping Tissue Properties in Trapezius with Ultrasound Shear Wave Elastography: A Pilot Study
Authors: Stiver Mikaela Liis , Agur Anne M. R. , Mirjalili S. Ali 
Published: April 2020

Ultrasound shear wave elastography (SWE) is a relatively new technology in the field of sonography. Even more so, research into musculoskeletal applications of SWE is in its infancy. Despite challenges concerning the anisotropic nature of muscle tissue, the literature suggests that SWE is a promising medium with which to examine patterns of tissue properties in morphometrically complex muscles, like trapezius. Tissue properties can provide valuable insights into muscle function and dysfunction. In our laboratory, we have characterized and quantified the comprehensive architecture of the cadaveric trapezius at the fascicular level throughout the muscle volume. These 3D anatomic data are essential for improving current B‐mode ultrasound protocols and making necessary modifications for SWE compatibility.The primary aim of this study was to test a novel SWE‐adapted ultrasound protocol for trapezius—targeting regions of contractile and connective tissues—and establish baseline patterns of tissue properties throughout the muscle.Twenty healthy adults (10F, 10M) with no history of back or neck injury, surgery, or chronic pain participated in the pilot study. We performed all imaging using the Siemens ACUSON™ S3000 ultrasound system, equipped with Virtual Touch™ IQ for SWE, and a 4–9 MHz linear array transducer (9L4, Siemens Healthcare). B‐mode and SWE images were captured in both seated and prone positions from each functional partition of trapezius: descending, transverse, and ascending. We collected shear wave speed (SWS) values from regions of interest corresponding to contractile and connective tissues on each elastogram and co‐registered them with 3D models of trapezius rendered from cadaveric data. SWS data will also be analysed with respect to participant sex, age, height, weight, and hand dominance.Preliminary results show marked differences in SWS between regions of contractile and connective tissues in trapezius, consistent with the structural patterns observed during cadaveric dissection and modeling. Of particular interest were areas in the transverse and ascending partitions with extensive regions of musculoaponeurotic junction: we observed a gradual increase in SWS of up to 200% between contractile tissue and connective tissue across the musculoaponeurotic junction. Tissue properties in the descending partition of trapezius were challenging to characterize due to substantial changes in fascicle direction, limited muscle thickness, and proximity to underlying bone.To the best of our knowledge, this study is the first to investigate patterns of soft tissue stiffness in the healthy adult trapezius, including both contractile and connective tissues. These data, in combination with the novel SWS‐adapted ultrasound protocol, offer a strong foundation on which to conduct future studies of individuals with musculoskeletal disorder in trapezius.Support or Funding InformationSupported by a Vanier Canada Graduate Scholarship and a Michael Smith Foreign Study Supplement from the Canadian Institutes of Health Research (CIHR).