Dislocations of the head of the humerus. (Erichsen.)
Fig. 342
Relation of circumflex nerve to the head of the humerus, explaining mechanism of deltoid paralysis. (Marion.)
For convenience of description, and in the order of their frequency, shoulder dislocations are referred to as anterior, downward, posterior, and possibly upward, when combined with acromial fracture. Anterior displacements vary in degree, so that they are described as subcoracoid or subclavicular. Complete displacement in this direction can only occur through a rent in the anterior portion of the capsule, while the subclavicular muscle is pushed away or torn. The nearer the head of the bone rests to the sternum the greater the amount of laceration of the capsule, while its posterior portion is either stretched tightly or torn. In aggravated cases the tendon of the biceps is also torn out of its groove ([Figs. 341], [343] and [344]).
Fig. 343
Subclavicular dislocation. (Lejars.)
Fig. 344
