THE SHOULDER-GIRDLE. 



239 



once into place. Bringing the arm forward and upward relaxes the coracobrachialis 

 muscle, while bringing it across the chest in the last step assists the head over the 

 rim of the glenoid cavity and restores the member to its normal position. Prof. 

 H. H. Smith brought the elbow forward before making the external rotation instead 

 of after, as did Kocher. This is probably the better way because persistence in rotat- 

 ing outward when the lesser tuberosity is caught beneath the tense coracobrachialis 

 muscle is one cause of the frequent fracture of the humerus in attempting to carry 



FIG. 252. Kocher's method of reducing dislocation of the shoulder: Second step Keeping the arm in external 

 rotation, raise the elbow until the humerus reaches the vertical line or a little beyond. 



out Kocher's method; another cause is the violent contraction of the muscles holding 

 the upper end of the bone immovable. 



This method can be used without anaesthesia, but it is at times exceedingly pain- 

 ful and savors of cruelty. It is particularly applicable for old and severe cases. It 

 depends for its efficiency on the integrity of the posterior portion of the capsule, if this 

 has been torn loose the method fails and the head simply rotates in sitri. If this 

 latter is the case, reduction can readily be effected by direct traction and manipulation. 



FIG. 253. Kocher's method of reducing dislocation of the shoulder: Third (final) step Rotate the arm inward 

 and place the hand on the opposite shoulder bringing the elbow down on the anterior surface of the chest. 



POSTERIOR DISLOCATIONS OF THE SHOULDER. 



Posterior dislocations are always beneath some portion of the spine of the scapula, 

 hence they have been called subspinous. When the head lies anteriorly under the 

 posterior portion of the acromion process they have been called subacromial. 



Posterior luxations are rare. They occur either when the arm is abducted with 

 strong internal rotation or by direct violence, such as a blow on the anterior portion of 

 the shoulder, which forces the head out of its socket backward. The posterior portion 

 of the capsule is torn and the head lies posterior to the glenoid cavity with its anatomi- 

 cal neck resting on the rim and the lesser tuberosity in the glenoid fossa. The arm 

 is inverted and abduction and rotation impaired. The capsule is ruptured by internal 

 rotation while the arm is in a position of abduction, and then a push sends the head pos- 

 teriorly. We have seen it as a congenital affection resulting from injury in childbirth. 



