84 CLINICAL APPLIED ANATOMY. 



fibres of the sterno-mastoid above, and the clavicular fibres of the 

 pectoralis major below, in conjunction with the costo-clavicular 

 ligament. Owing, however, to the downward displacement of the 

 outer fragment the skin tends to become stretched over the outer 

 end of the inner fragment, which on this account appears as if it 

 were tilted upwards. 



Thus it comes about that the two fragments override one 

 another, the inner surmounting the outer, and a shortening of 

 the long axis of the bone is occasioned. 



In the recumbent posture, the vertical weight of the arm is 

 removed, and thus the downward displacement lost or greatly 

 minimised. In this position the weight of the limb tends 

 to draw the shoulder back, and so to reduce the amount 

 of the inward displacement and of the rotation of the shoulder 

 forwards. 



It is rare for the important structures which lie posterior to 

 the clavicle to be involved in fracture by indirect violence. The 

 subclavian vein, the subclavian artery, the brachial plexus of 

 nerves, the suprascapular vessels, and the dome of the pleura, 

 usually escape injury. In some cases of fracture by direct 

 violence, one or both fragments may be driven against them. 

 It is further rare for a fracture of the clavicle to be an open one. 

 This is owing to the laxity of the tissues superficial to the bones 

 which allow them to slip aside in direct violence, and to stretch 

 over the bony projection in fractures due to indirect violence. 



Fractures of the Scapula. The only fairly common fracture 

 of the scapula is the breaking off of the acromion process, 

 frequently really a separation of the acromial epiphysis which 

 does not coalesce with the rest of the bone until about the age of 

 twenty-two. This fracture is usually the result of direct violence, 

 such as pitching upon the shoulder, or running the shoulder 

 against some unyielding structure. Much displacement is, there- 

 fore, uncommon, and the more so because of the thick fibrous 

 covering of this part of the bone. The deltoid may drag the 

 detached fragment somewhat downwards. 



The coracoid process may be fractured by direct violence, or by 



