THE SHOULDER. 7 _ 



side, covered by the edge of the deltoid muscle, may be felt the coracoid process. This is situated 

 slightly to the outer side of the groove, between the pectoralis major and the deltoid, which contains 

 the cephalic vein and widens out as it passes up toward that portion of the clavicle which is more 

 or less free from muscular attachments. In this situation is the injraclavicular fossa, the region 

 for ligating the first portion of the axillary artery. In lean individuals the sharp margin of the 

 costocoracoid ligament may be palpated in this fossa as it runs toward the coracoid process. At 

 the acromial end of the clavicle is the acromiodavicular articulation, which feels like a short 

 narrow groove running in a sagittal direction. The parts which have been named should be 

 palpated in normal individuals, so that the changed relations present in dislocations of the 

 shoulder-joint may be recognized with certainty. 



The Anterior Region of the Shoulder. After dividing the skin, the platysma, the ends of 

 the supraclavicular nerves, and the thin fascia covering the groove between the pectoralis major 

 and the deltoid, we may easily find the cephalic vein, which runs upward from the external 

 bicipital groove accompanied by the humeral branch of the acromiothoracic artery (see page 95); 

 it passes inward above the tendon of the pectoralis minor, perforates the costocoracoid membrane, 

 and empties into the axillary vein. If the deep fascia is removed, the narrow space between the 

 upper border of the pectoralis minor and the subdavius muscle is exposed. The pectoralis minor 

 arises from the outer surfaces of the second to the fifth ribs and is inserted into the coracoid 

 process; the subdavius arises from the junction of the first rib with its cartilage and is inserted 

 into the under surface of the acromial extremity of the clavicle (see Fig. 28). If we follow the 

 cephalic vein, we come to the axillary vein. To the outer side of this vein are the cords of the 

 brachial plexus, and between these two structures and somewhat posteriorly is the axillary artery 

 just after it has passed over the first rib. This is the usual situation for the ligation of this vessel. 

 In order to expose the artery the plexus must be displaced outward and the vein inward. The 

 structures endangered are the acromiothoracic artery (acromial, thoracic, and descending 

 branches)-, and the anterior thoracic nerves which supply the pectoralis major and minor muscles. 

 An independent thoracic branch (the superior thoracic) is occasionally given off by the axillary 

 artery. The vessels and nerves pass beneath the clavicle, the position of the artery corresponding 

 to about the middle of the bone. The relation of the vessels and nerves to the clavicle explains 

 the fact that in fractures of this bone they may be more or less lacerated or compressed by the 

 downward displacement of the acromial fragment. [Laceration or compression of the nerves 

 and vessels following fractures is much less frequent than might be supposed, owing to the fact 

 that the subdavius muscle acts as a cushion. ED.] The plexus is more frequently involved in 

 these injuries than are the vessels. As the nerve-trunks are nearest to the shoulder-joint, they 

 are the first structures to be compressed in the subcoracoid dislocation, in which the head of the 

 humerus is drawn inward and presses them against the ribs. This dislocation may also injure 

 the circumflex nerve (see page 75 and Fig. 30) which runs around the surgical neck of the humerus. 

 A corresponding compression of the vessels and nerves may also be observed in those fractures of 

 the surgical neck of the humerus in which the upper end of the lower fragment is so frequently 

 displaced inward and the arm is held in a position of abduction. As the vessels are situated at a 

 greater distance from the head of the humerus, they are less likely to be involved than are the 



nerves. 



