254 



HUMAN ANATOMY. 



Fig. 273. 



Lines of fracture of the scapula. 



by a synchondrosis. The possibihty of its detachment by excessive action of the 

 latissimus dorsi has been mentioned, but no case of traumatic separation has been 

 recorded. 



Fracture is rare, in spite of the thinness of much of the bone, because of its 

 mobility, the adaptation of its curves to the underlying thoracic surface, the elasticity 

 and compressibility of that surface, the thickness ^of the muscles that cover the 

 scapula and of those that lie beneath it, the fragility of the clavicle (which by frac- 

 turing often saves the scapula), and the great range of 

 movement and corresponding weakness of the shoulder- 

 joint, which, in like manner, by undergoing luxation, 

 prevents the force of the traumatism from reaching the 

 scapula. 



Fracture of the body and of the inferior angle from 

 indirect violence has been reported in a few cases. The 

 arms were fixed, and strong traction was being exer- 

 cised in more than one case. It seems probable that 

 the bone breaks between the opposing forces of the 

 rhomboids and trapezius on the one hand, and the 

 teres muscles, the subscapulars, and the infraspinatus 

 on the other. 



The most common fracture is that of the body, 

 usually running transversely or obliquely through the 

 subspinous fossa. The attachments of the subscapu- 

 laris beneath and of the infraspinatus above usually 

 prevent any marked displacement. There is pain on 

 lifting the arm to a horizontal position, because, in order 

 that the deltoid may be able to do this, the acromion 

 must become a fixed point, and that necessitates the contraction of the rhomboids 

 and other muscles whose function it is, aided by the leverage afforded by the pro- 

 longation of the scapula downward, to fix the blade of the scapula when the deltoid 

 is in action. 



Superficial ecchymosis is rare on account of the dense infraspinous fascia which 

 prevents the effused blood from reaching the surface. 



Fracture of the acromion is attended with slight flattening of the tip of the 

 shoulder, the weight of the arm, acting through the deltoid, dragging the frag- 

 ment downward. There may be the usual symptoms of preternatural mobility, 

 crepitus, etc. 



Fracture of the coracoid is rare. Before the age of seventeen it may be an 

 epiphyseal separation. Displacement is not common, as the downward pull of the 

 pectoralis minor, short head of the biceps, and coraco-brachialis (page 590) is 

 effectually resisted by the coraco-acromial and coraco-clavicular ligaments. Crepitus 

 and preternatural* mobility may possibly be recognized by sinking the fingers into 

 the interval between the deltoid and pectoral muscles. The coracoid will be found 

 just beneath the inner deltoid margin. 



Fractures of the neck of the scapula include, in surgical language, those which 

 begin at the suprascapular notch and run to the axillary border of the bone detach- 

 ing the glenoid cavity and the coracoid process. There is no instance of fracture of 

 the anatomical neck, — the constricted part supporting the glenoid cavity. The 

 fragment, with the arm, will drop downward, away from the acromion. This puts 

 the deltoid on the stretch and causes flattening of the shoulder. There will be a 

 depression beneath the edge of the acromion. The arm will be increased in length. 

 These symptoms (which will occur only if the coraco-acromial and coraco-clavicular 

 ligaments are torn) are also found in subglenoid luxation of the humerus (page 583); 

 but in the fracture, the presence of crepitus, the downward displacement of the 

 coracoid, the ready disappearance of the deformity on pushing the head of the 

 humerus upward, its prompt reappearance when the arm is allowed to hang by the 

 side, and the ease with which the hand may be placed on the opposite shoulder 

 serve clearly to denote the character of the accident. 



Excision of the scapula itself is not uncommonly indicated on account of malig- 



