Stiffness of the infraspinatus and the teres minor muscles during shoulder external rotation: An in-vitro and in-vivo shear wave elastography study

• Published in: Clinical biomechanics (Bristol) 2021-05, Vol.85, p.105328-105328, Article 105328
• Main Authors: Yuri, Takuma, Trevino, Jose H., Hatta, Taku, Kiyoshige, Yoshiro, Jacobs, Philip M., Giambini, Hugo
• Format: Article
• Language: English
• Subjects: Excursion; Infraspinatus; Shear-wave elastography; Sub-regions; Teres minor
• ISSN: 0268-0033; 1879-1271
• DOI: 10.1016/j.clinbiomech.2021.105328

A better understanding of the morphological and functional differences in the anatomical sub-regions of the rotator cuff muscles is critical so that appropriate surgical and rehabilitation methodologies can be implemented in patients with shoulder-related injuries. The purpose of the current study was to develop a comprehensive imaging protocol using shear-wave elastography for the infraspinatus and teres minor muscles, and investigate differences in elastic properties of three distinct infraspinatus muscle sub-regions and of the teres minor muscle. First, we developed a protocol for probe positioning for both muscles using three cadaveric shoulders. Second, we evaluated in-vivo elastic properties [passive and active stiffness (kPa)] and excursion (mm) outcomes from these muscles during shoulder external rotation. Elastic properties were significantly different among the infraspinatus muscle sub-regions and teres minor muscle. Passive stiffness decreased with increasing rotation angles except for the middle sub-region of the infraspinatus muscle which showed a decreased up to mid-range followed by an increment towards the end-range. Overall, active stiffness of the infraspinatus muscle and teres minor muscle decreased with increasing rotation angles, while that of the middle sub-region increased up to mid-range, and decreased at the end-range. Distinct characteristics of the infraspinatus and teres minor muscles, and more importantly, of the individual sub-regions within the infraspinatus muscle call for an in-depth analysis of their morphological and functional differences. Special attention should be put into these sub-regions when performing surgical and rehabilitation procedures for patients with shoulder-related injuries. •Shear wave elastography measurements of the infraspinatus and teres minor muscles.•Muscle regions show distinct active and passive stiffness with external rotation.•Muscle regions show distinct passive excursions during external rotation.•Shoulder muscle regions should be considered during surgery and rehabilitation.