DISLOCATIONS OF THE SHOULDEB. 117 



The displacement of the head of the bone inwards will neces- 

 sarily hring about pressure upon the structures lying internal to 

 it. The axillary vein is frequently the first to suffer, and oedema 

 of the limb distally, from obstruction to the return of venous 

 blood, is a common sign. If the compression is great and is 

 maintained too long, there is a possibility of gangrene occurring. 

 It is well also to remember that in dislocations which have 

 remained unreduced for some length of time, adhesions may have 

 formed between the vessels and the protruded head, and there 

 is some likelihood of their being torn in too energetic attempts 

 at reduction. 



Pressure upon the nerves of the brachial plexus gives rise to 

 referred pain, and in some cases paralysis, particularly of the 

 deltoid, as a result of interference with the function of the 

 circumflex nerve. 



In the reduction of this form of dislocation by the common 

 method of manipulation, it is desired first to stretch the opening 

 in the capsule by bringing the elbow to the side and firmly rotat- 

 ing the humerus outwards ; secondly, to bring the head of the bone 

 well under the acromial arch by raising the elbow and carrying 

 it somewhat inwards across the chest. The last step in the mani- 

 pulation, namely rotating the arm suddenly inwards and carry- 

 ing the elbow still further across the chest, will cause the head 

 to slip through the rent in the capsule and over the margin of 

 the glenoid fossa into its natural position. 



There are two other varieties of dislocation of the shoulder. 

 In one the head also leaves the capsule at its unprotected area, 

 namely below and somewhat in front, and rests, hitched as it were, 

 beneath the glenoid fossa : this displacement is in consequence 

 styled sub-glenoid. In this way some lengthening will be observed 

 on the affected side, if a measurement is taken from the acromion 

 process to the external condyle of the humerus. 



In the last variety the head is displaced backwards through a 

 rent in the posterior and lower part of the capsule, and, tearing 

 up the infraspinatus muscle, it comes to lie beneath the spine 

 of the scapula, the dislocation is therefore termed sub-spinous. 



