Abstract
The aim of this study was to estimate the function of the rotator cuff and scapulothoracic joint roentogenographically and electromyographically in patients with loose shoulder. Ten patients with inferior instability were examined in this study. Eight of 10 patients had symptoms. In these 8 patients, Scapula-45 radiographs with the arm at the side revealed inferior displacement of the humeral head and slightly upward migration of the humeral head at 45 degrees elevation. Although radiographs taken with the arm at the side also revealed inferior displacement of the humeral head in 2 patients without symptoms, radiographs at 45 degrees elevation revealed good adaptation of the humeral head to the glenoid fossa. Inferior inclination of the scapula was seen with the arm at the side in 10 patients. Although the scapula rotated upward at 45 degrees elevation in 2 patients, the scapula did not rotate upward in symptomatic patients. In IEMG study, the ratio of supraspinatus muscle activity to deltoid activity remained almost stationary irrespective of load in 2 patients without symptoms at 45 degrees elevation.
