Dynamic stability of glenohumeral joint during scapular plane elevation

To investigate the muscle-controlled dynamic stability of the glenohumeral joint through X-ray fluoroscopy in active and passive shoulder elevation in scapular plane. Sixty healthy volunteers were collected in this study, including 23 men and 37 women, with an average age of 28.4 years. Passive and active shoulder elevation in scapular plane were observed under X-ray imaging. In 18 subjects, X-ray films were taken when the shoulder elevated in scapular plane from 0 degree to 150 degrees with a 30 degrees interval at each stage in both active and passive movements. The angles between the pivot of the humerus and the glenoid surface (GHA) during the active and passive motion were calculated and analyzed. Manual examination was also applied in the same manner. The pivot of the humerus had a tendency to be vertically closer to the glenoid surface in the active elevation than in the passive elevation. The differences of GHA between the active and passive motion at 0 degree, 30 degrees, 60 degrees, 90 degrees, 120 degrees and 150 degrees elevation were 4.55 degrees +/- 0.37 degree, 5.44 degrees +/- 1.16 degrees, 6.50 degrees +/- 1.50 degrees, 4.94 degrees +/- 0.82 degree, 4.50 degrees +/- 0.40 degree and 1.44 degrees +/- 0.68 degree, respectively. Manual examination found the angle between the scapula and the humerus tended to be larger in the active motion than in the passive motion. The active coordination of the muscles around the shoulder is beneficial to the dynamic stability of the glenohumeral joint.