Rotation of the scapula and shoulder subluxation in hemiplegia

Inferior subluxation of the shoulder in hemiplegia was measured using a tridimensional (3-D) x-ray technique. This technique gave the true vertical distance separating the apex of the humeral head and the inferior margin of the glenoid cavity. Both shoulders of each subject were evaluated and the difference used as a measure of subluxation. This measure was then compared to the orientation of the scapula relative to the vertical, to the abduction, and to the relative abduction of the arm. Relative abduction is defined as the angle between the humerus and the glenoid fossa. It has been suggested that these factors are associated with inferior subluxation in hemiplegia. Results of this study of 50 volunteer stroke patients indicated that the affected and nonaffected shoulders were different (subluxed) in terms of the vertical position of the humerus vis-à-vis the scapula. The orientation of the glenoid cavities was also different, the subluxed one facing less downward. The angle of abduction of the arm of the affected side was significantly greater than on the nonaffected side, but the relative abduction of the arm was on the same order of magnitude for both sides. There was no significant relationship between the orientation of the scapula and the severity of the subluxation. The abduction of the humerus was weakly (r = .24) related to the subluxation, which partly explained the weak association found between the relative abduction of the arm and the subluxation. It was concluded that the position of the scapula and the relative abduction of the arm cannot be considered important factors in the occurrence of inferior subluxation in hemiplegia.