THE SHOULDER-GIRDLE. 241 



The infraspinatus, teres minor, and sometimes the subscapularis muscles are 

 ruptured and frequently there are accompanying fractures of the tuberosities or some 

 part of the scapula. The head makes a prominence posteriorly and the arm hangs to 

 the side and in a position of inward- rotation. Reduction, if the injury is recent, is 

 likely to be easily effected by pushing the head directly forward into its socket. 



FRACTURES OF THE SHOULDER-GIRDLE AND UPPER END 



OF THE HUMERUS. 



FRACTURES OF THE CLAVICLE. 



Fractures of the clavicle divide with those of the radius the distinction of being 

 the most frequent of any in the body. 



The clavicle is most often broken in its middle third, next in its outer, and, lastly, 

 in its inner third. 



Fracture of the Inner Third of the Clavicle. This is the rarest frac- 

 ture of the clavicle and has its main anatomical interest in relation to the costoclavic- 

 ular ligament. This ligament runs obliquely upward and outward from the upper 

 surface of the cartilage of the first rib to the lower surface of the clavicle, a distance 

 of 2 cm. (i in.). 



Immediately in front of the outer portion of this ligament is the insertion of the 

 tendon of the subclavius muscle. The line of the fracture may be either transverse 

 or oblique; if oblique it follows the same direction as do the fractures of the middle 

 third of the bone, viz. , from above, downward and inward. The displacement of 

 the inner fragment is upward and of the outer fragment downward. The displace- 



FIG. 256. Fracture of the clavicle just outside of the middle, with the customary deformity. 



ment of the inner fragment upward is promoted by the attachment of the clavicular 

 origin of the sternomastoid muscle: it is opposed by the costoclavicular (rhomboid) 

 ligament and to a less extent by the subclavius muscle. 



Fracture of the Middle Third of the Clavicle. The clavicle is most 

 frequently broken in the outer half of its middle third. The bone at this part is most 

 slender; it is here that the anterior curve passes into the posterior; and, finally, it has 

 fewer muscular attachments at this situation. The upper surface has arising from its 

 inner third the clavicular origin of the sternomastoid muscle. Its middle third has 

 no muscular attachments, and on its outer third is the trapezius muscle. On the 

 lower or anterior surface on its inner half is the clavicular origin of the pectoralis 

 major and on its outer third is the deltoid. This leaves the outer half of the middle 

 third free from muscular attachments, with the exception of the subclavius on its 

 under surface. It is through this part of the bone that fractures occur. 



Sometimes in children the line of fracture is transverse, but most often it is 

 oblique and always in the direction from above downward and inward. 



The displacement of the inner fragment is upward, and of the outer fragment 

 downward and inward. This produces the deformity seen in Fig. 256. The inner 

 fragment is pulled up by the clavicular origin of the sternomastoid muscle. The 

 support of the clavicle being gone, the shoulder falls down and in. It is impelled in 

 that direction, first, by the weight of the upper extremity, and, secondly, by the action 

 of the axillary fold muscles, pectoralis major and minor anteriorly and teres major 

 and latissimus dorsi posteriorly, and by the subclavius to some extent. The anterior 

 edge of the scapula rotates inward and its posterior edge tilts outward. 



In this manner overlapping is produced, and measurements of the injured and 

 healthy sides taken from the sternoclavicular to the acromioclavicular joint will 

 show some shortening on the injured side. As the continuity of the shoulder-girdle 

 16 



