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Updated: Sep 19, 2025
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Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography
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Association Between Shoulder Morphological Changes and Glenohumeral Maximum External Rotation During Late Cocking
Makoto Takahashi1,2, Hirotaka Mutsuzaki3,4, Koji Iwamoto5
1Department of Physical Therapy, School of Health Sciences, Japan University of Health Sciences, Saitama, Japan.
Orthopaedic Journal of Sports Medicine
|June 19, 2025
Summary
Excessive external rotation in throwing athletes is linked to shoulder joint changes. This study found a significant association between maximum external rotation and quantified morphological shoulder joint changes, like %PGHD and %AOI.
Area of Science:
- Orthopedic biomechanics
- Sports medicine
- Radiological anatomy
Background:
- Excessive external rotation of the glenohumeral joint during the late cocking phase of throwing is implicated in internal impingement.
- The precise relationship between maximum external rotation (MER) and quantified shoulder joint morphological changes remains unclear.
Purpose of the Study:
- To investigate the association between glenohumeral MER and quantified morphological changes in the throwing shoulder.
Main Methods:
- Fifteen male baseball players underwent open magnetic resonance imaging to measure posterior glenohumeral distance and impingement area.
- Percent posterior glenohumeral distance (%PGHD) and percent area of impingement (%AOI) were calculated by comparing throwing to non-throwing shoulders.
- A 3-dimensional motion analysis system measured the glenohumeral MER angle.
Main Results:
- Glenohumeral MER angle demonstrated a significant association with %PGHD (β = 0.685, P = .005).
- Glenohumeral MER angle was also significantly associated with %AOI (β = 0.754, P = .001).
Conclusions:
- The study concludes that the glenohumeral MER angle is associated with %PGHD and %AOI, reflecting morphological shoulder joint alterations.
- Understanding excessive external rotation during the throwing motion is crucial for comprehending morphological changes and preventing throwing-related injuries.
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