To investigate the muscle activity patterns of the glenohumeral joint during internal rotation both with the arm at 0° and 90° of abduction using 2-deoxy-2-[18F] fluoro-d-glucose (FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI).
Materials and methods
Six healthy male volunteers underwent PET examination after performing active glenohumeral internal rotation exercise using an elastic band both with the arm at 0° and 90° of abduction. As a control, PET scan under resting condition was also performed. The exercise was performed before and after 18 fluorodeoxyglucose injection. Each PET image was fused to the corresponding MRI to identify each muscle. The standardized uptake value (SUV) of each muscle was compared between the two arm positions.
With the arm at 0° of abduction, the SUV increased significantly after exercise both in the middle and inferior 1/3 of the subscapularis, which were significantly higher than that of the superior 1/3 of the subscapularis (P < 0.05). The SUV of the inferior 1/3 of the subscapularis was significantly higher at 90° of abduction than at 0° of abduction and was significantly higher than that of the superior 1/3 at 90° of abduction (P < 0.01). The SUV after exercise in the inferior infraspinatus and teres minor increased.
The middle and inferior parts of the subscapularis are the main shoulder internal rotators in 0° of abduction, whereas the inferior part of the subscapularis is the main internal rotator in 90° of abduction.
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The authors wish to thank Dr. Toshihiko Fujimoto, Dr. Kotaro Hiraoka, and Dr. Kazuyoshi Baba for their technical assistance as well as the entire staff at the Cyclotron and Radioisotope Center, Tohoku University, for their support and collaboration.
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The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
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Matsuzawa, G., Sano, H., Yamamoto, N. et al. Muscle activities during shoulder internal rotation differ in arm position: a preliminary quantitative analysis using positron emission tomography. Skeletal Radiol 49, 1839–1847 (2020). https://doi.org/10.1007/s00256-020-03490-0