Internal rotation deficits affect scapular positioning in baseball players.
BACKGROUND
Anecdotal evidence suggests an association between glenohumeral internal rotation deficits (GIRD) and scapular dysfunction, an observable alteration in the normal position or motion of the scapula in relation to the thoracic cage.


OBJECTIVE
We therefore hypothesized players with GIRD (15 degrees or greater) will have decreased dominant arm scapular upward rotation and increased scapular protraction compared with baseball players with GIRD (14 degrees or less).


METHODS
We studied 43 baseball players with no current shoulder or elbow symptoms; 22 had GIRD 15 degrees or greater and 21 had GIRD 14 degrees or less. We measured glenohumeral internal rotation supine with the scapula stabilized. Scapular upward rotation was tested at rest; 60 degrees , 90 degrees , and 120 degrees abduction in the scapular plane; and scapular protraction at 0 degrees , hands on hips, and 90 degrees abduction in the scapular plane.


RESULTS
The GIRD (15 degrees or greater) group had less scapular upward rotation at 60 degrees (3.58), 90 degrees (5.01), and 120 degrees (2.63) in the dominant arm. Scapular protraction at 90 degrees (0.88 cm) also was greater in the dominant arm of the GIRD (15 degrees or greater) group.


CONCLUSIONS
Baseball players with more GIRD have alterations to the position and motion of their scapula. A dual goal of minimizing GIRD and strengthening the scapular stabilizers may be warranted in this population.


METHODS
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Thomas
Stephen J
SJ
University of Delaware, 807 Waters Edge Drive, Newark, DE 19702, USA. sjthomas@udel.edu
Swanik
Kathleen A
KA
Swanik
Charles B
CB
Kelly
John D
JD
D000293:Adolescent; D056352:Athletes; D001484:Baseball; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D007839:Functional Laterality; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D016059:Range of Motion, Articular; D012540:Scapula / Q000503:physiopathology*; D012785:Shoulder Joint / Q000503:physiopathology*; D055815:Young Adult