Glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation in throwing.
BACKGROUND
Because a majority of throwing injuries occur near the maximum external rotation (MER) of the throwing shoulder, sports medicine practitioners and researchers have paid special attention to the shoulder kinematics at the MER in throwing. However, little is known about the individual kinematics of the glenohumeral, scapulothoracic, and thoracic joints at the MER. Purpose To demonstrate the glenohumeral, scapulothoracic, and thoracic joint movements and their contribution to the MER in throwing for baseball players.


METHODS
Descriptive laboratory study.


METHODS
We collected throwing motion data for 20 collegiate baseball players by using 3 high-speed cameras and established 3-dimensional coordinates of each landmark with a direct linear translation method. We then obtained the MER of the shoulder complex, the external rotation angle of the glenohumeral joint, the posterior tipping angle of the scapula, and the thoracic extension angles at the MER in throwing.


RESULTS
The mean (+/- standard deviation) value of the MER was 144.2 degrees +/- 11.0 degrees . The mean (+/- standard deviation) values of the glenohumeral external rotation, the scapular posterior tipping, and the thoracic extension angles at the MER were 105.7 degrees +/- 15.5 degrees , 23.5 degrees +/- 13.9 degrees , and 8.9 degrees +/- 7.3 degrees , respectively.


CONCLUSIONS
Our results indicate that not only the glenohumeral joint movement but also the scapular and thoracic movements make major contributions to the MER angle.


CONCLUSIONS
To better understand the pathomechanics of the shoulder complex in throwing, we need to take into account the individual contributions of the glenohumeral, scapulothoracic, and thoracic extension movements to the MER.
Miyashita
Koji
K
Research Institute of Life and Health Sciences, Chubu University, Matsumoto-cho 1200, Kasugai City, Aichi, Japan 487-8501. kmiyashita@isc.chubu.ac.jp
Kobayashi
Hirokazu
H
Koshida
Sentaro
S
Urabe
Yukio
Y
D001484:Baseball; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D009068:Movement / Q000502:physiology; D010781:Photography; D016059:Range of Motion, Articular / Q000502:physiology*; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D013909:Thorax / Q000502:physiology*; D055815:Young Adult