Different scapular kinematics in healthy subjects during arm elevation and lowering: glenohumeral and scapulothoracic patterns.
OBJECTIVE
The scapulothoracic (ST) joint affects glenohumeral (GH) joint function. We observed 3-dimensional scapular motions during arm elevation and lowering to identify the scapulohumeral rhythm in healthy subjects and to compare it between the dominant and nondominant arms.


METHODS
Twenty-one healthy subjects participated in this study. Participants randomly elevated and lowered the arms in the scapular plane, and data were recorded by a computerized 3-dimensional motion analyzer at each 10 degrees increment.


RESULTS
Of the 42 shoulders, 21 showed a greater ratio of GH motion relative to ST motion whereas the other 21 showed a smaller ratio of GH motion relative to ST motion. The angle of upward rotation of the scapula showed a statistically significant difference between both types. The mean maximum angles of upward rotation, posterior tilting, and internal rotation were 36.2 degrees +/- 7.0 degrees , 38.7 degrees +/- 5.7 degrees , and 36.8 degrees +/- 12.2 degrees , respectively. No significant difference was found in angles of 3 scapular rotations between the dominant and nondominant arms.


CONCLUSIONS
These results indicate that there are 2 distinctly different scapulohumeral rhythms in healthy subjects but without a significant difference between dominant and nondominant arms. These findings should be referred to when one is interpreting kinematics in a variety of shoulder disorders.
Yano
Yuichiro
Y
Department of Orthopaedic Surgery, Dokkyo Medical University, Tochigi, Japan. y-yano@koriyama-h-coop.or.jp
Hamada
Junichiro
J
Tamai
Kazuya
K
Yoshizaki
Kunio
K
Sahara
Ryo
R
Fujiwara
Takayuki
T
Nohara
Yutaka
Y
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D034941:Upper Extremity / Q000502:physiology; D055815:Young Adult