244 APPLIED ANATOMY. 



Fracture Through the Body. The scapula has attached to its under surface 

 the subscapularis muscle, along its posterior border is the serratus anterior (magnus) 

 and rhomboids, to its dorsum and edge below the spine are attached the infraspina- 

 tus, teres minor, and teres major muscles. These are covered by a strong, tough 

 fascia which dips between them to be attached to the bone. 



Bearing these facts in mind it is readily appreciated why in many of these 

 fractures, which usually traverse the bone below its spine from the axillary to the 

 vertebral border, the displacement is slight, and why healing occurs with some 

 appreciable deformity but with little disability. 



If, however, the fracture is low down, breaking off the lower angle, then the teres 

 major and lower portion of the serratus anterior (magnus) muscles displace the frag- 

 ment toward the axilla, and this is to be borne in mind in treating the injury. 



Fracture of the acromion process is more rare than would be expected. 

 It is the result of direct violence, and the displacement and disability resulting from 

 the injury are slight. The acromion is covered by a dense fibrous expansion from 

 the trapezius above and the deltoid below, and these prevent a wide separation of 

 the fragments. 



Fracture of the coracoid process is also rare and may occur from muscular 

 contraction or direct violence, as in luxation of the shoulder. It might be thought 

 that owing to the action of the pectoralis minor, coracobrachialis, and short head of 

 the biceps muscles, which are attached to it, it would be widely displaced, but this 

 is not so, for the conoid and trapezoid ligaments still hold it in place. 



Fractures through the surgical neck are not common. They pass down 

 through the suprascapular notch and across the glenoid process or head, in front of the 

 base of the spine and behind and parallel with the glenoid fossa. The tendency of 

 the outer fragment to be dragged down by the weight of the arm is resisted by the 

 coraco-acromial and coracoclavicular (conoid and trapezoid) ligaments as well as by 

 the inferior transverse ligament, which runs from one fragment to the other from 

 the base of the spine, on the posterior surface, to the edge of the glenoid cavity. 

 These ligaments all remain intact. 



Fracture through the glenoid process, chipping off a greater or less por- 

 tion of the articular surface, is rarely diagnosed. It occurs sometimes in cases of 

 luxation. The long head of the triceps muscle may be fastened to the detached frag- 

 ment and is liable to pull it downward and therefore some interference with the func- 

 tions of the joint would be apt to remain and prevent complete recovery. 



FRACTURES OF THE UPPER END OF THE HUMERUS. 



Fractures of the upper end of the humerus may occur through the anatomical 

 neck, through the tuberosities, detaching one or both, and through the surgical neck 

 just below the tuberosities. These fractures are frequently associated with luxation 

 of the head of the bone. 



Fracture through the Anatomical Neck. This occurs as the result of direct 

 violence and most often, though not always, in old people. The line of fracture does 

 not always follow exactly the line of the anatomical neck, but may embrace a portion 

 of the tuberosities. The fracture may or may not be an entirely intracapsular one. 

 The capsule in its upper or outer portion is thickened at its humeral end by more or 

 less blending with the tendons of the muscles which pass over it. The capsule at this 

 point is attached to the anatomical neck almost or quite up to the articular surface. 

 On the under side to the contrary it passes about a centimetre below the articular 

 surface and doubles back to be attached somewhat closer to it (see Fig. 266, page 253). 



In consequence of this arrangement, a fracture which follows the anatomical neck 

 would be within the joint below and just outside of it above. As a matter of fact, 

 some of these fractures are intra- and some partly extracapsular. This influences the 

 amount and character of the displacement and the course of healing. If the fracture 

 is entirely intracapsular, bony union may not occur, as no callus may be thrown out 

 by the upper fragment and atrophy of the fragment may ensue. The fragment is 

 apt to be much displaced, being tilted and lying to the inner side anteriorly. 

 Sometimes it is entirely extruded from the joint. In one case we have seen it lodged 

 in front under the anterior axillary fold. 



