Glenohumeral relationship in maximum elevation.
OBJECTIVE
The purpose of this study was to clarify rotational relationships between the anatomical landmarks of the glenohumeral joint in maximum elevation.


METHODS
Twenty-five healthy volunteers (20 men, 5 women; mean age, 31 years) held the arm in maximum elevation in an open MRI system. In each three-dimensionally computer-generated image, elevation angle of the humerus in the plane of elevation was measured, based on the glenoid and the scapular planes. Using the equator set on the head surface by the plane parallel to the humeral axis, involving the head center and the bicipital groove, glenoid location and rotational relationships were investigated.


RESULTS
The elevation angle was 102° ± 9° in the plane 7° ± 8° anterior to the scapular plane, and axial rotation was fixed with the glenoidal long axis parallel to the equator (within 2°). Each glenoid center located on antero-superior portion of the humeral head, and the direction from the top of the head to its location was the same as that of the shaft tilting, indicating the glenoid only translated without rotation after reaching the top of the head on the equator.


CONCLUSIONS
Before reaching maximum elevation, the glenohumeral joint would be locked in axial rotation. The position when the glenoid is on the top of the humeral head with the humeral shaft perpendicular to the glenoid is considered to be essentially the final position of elevation, above which the glenohumeral joint only translates without axial rotation even if the humerus is more elevated.
Nobuhara Hospital and Institute of Biomechanics, 720 Haze, Issaicho, Tatsunoshi, Hyogo, 679-4017, Japan, inuhiro123@yahoo.co.jp.
Hiroaki
H
Inui
Katsuya
K
Nobuhara
D000328:Adult; D059925:Anatomic Landmarks; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D016059:Range of Motion, Articular; D012399:Rotation; D012540:Scapula / Q000033:anatomy & histology; D012785:Shoulder Joint / Q000033:anatomy & histology*