THE SHOULDER-GIRDLE. 



245 



The signs and symptoms will vary much, according to the position of the head, 

 and a positive diagnosis may be impossible. A thorough knowledge of the surface 

 anatomy is essential in these cases and a careful comparison should be made with the 

 opposite healthy shoulder. Impaction sometimes occurs, and is said to be most 

 often of the upper fragment into the lower, sometimes splitting it and detaching to a 

 certain extent one of the tuberosities. Sometimes it is the lower fragment which is 

 impacted into the upper. 



Fractures through the Tuberosities. Like the former these are often 

 accompanied by luxation, especially if one or both of the tuberosities is detached. 

 These fractures are frequently blended with fracture through the anatomical neck. In 

 this fracture, however, the influence of the muscles is to be remembered. The supra- 

 spinatus, infraspinatus, and teres minor insert into the greater tuberosity, and the sub- 

 scapularis into the lesser. The line of fracture may pass 

 through their insertions and the displacement may be slight. 



The upper fragment is, however, liable to be tilted out- 

 ward by the contraction of the supraspinatus muscle, which 

 is attached to the upper portion of the upper fragment, while 

 there is no muscle attached below to counteract it. In this 

 case the shaft of the humerus is drawn up and out by the 

 deltoid and is felt beneath the acromion process. There is 

 but little rotatory displacement of the upper fragment because 

 the subscapularis anteriorly is neutralized by the infraspinatus 

 and teres minor posteriorly. 



In those instances in which there is not much displace- 

 ment of the upper fragment, the lower one may be drawn 

 inward and forward by the action of the muscles of the ax- 

 illary folds. 



Fractures detaching the tuberosities are almost always 

 accompanied by luxation. If the greater tuberosity alone is 

 detached, it is drawn up beneath the acromion by the supra- 

 spinatus. 



In all these fractures the subsequent disability is often 

 great and the prognosis is unfavorable. They are amongst 

 the hardest in the body to correctly diagnose. They are 

 treated sometimes with a shoulder-cap and sometimes with the arm in the abducted 

 position while the patient is kept in bed. Epiphyseal separation will be alluded to 

 farther on. 



Fractures of the Surgical Neck. These are the most common fractures 

 of the humerus. The surgical neck of the humerus is usually denned as the portion 

 between the lower part of the tuberosities and the upper edge of the tendons of the 

 pectoralis major and latissimus dorsi muscles. Often, however, the tendons of these 

 two muscles continue almost or quite up to the tuberosities, hence there is little or 

 no interval here and the line of fracture then passes through the upper part of these 

 tendons. 



The fractures occur both from direct and indirect violence and the direction of 

 the force has probably something to do with the displacement of the fragments. 



Displacement. It can readily be seen that if a blow is received on the humerus 

 below the tuberosities while the arm is in a somewhat abducted position the head will 

 be supported by the glenoid process (head) of the scapula and the bone will be 

 fractured through the surgical neck and driven in towards the body, and, as the 

 scapula is supported posteriorly, the movable lower fragment is displaced anteriorly. 

 After the fracture has occurred, and possibly in some cases aided by the peculiar 

 direction of the fracturing force, the lower fragment is drawn upward by the muscles 

 running from one side of the fracture to the other. These are the deltoid, biceps, 

 coracobrachialis, and the long head of the triceps. The typical displacement is 

 for the upper fragment to be abducted and some say rotated out this latter is not 

 without doubt. The lower fragment is certainly in front and to the inside of its 

 normal position. 



The abduction of the upper fragment is due to the unresisted action of the supra- 

 spinatus muscle. The subscapularis in front and the teres minor and infraspinatus 



FIG. 260. Fracture through 

 the anatomical neck of the hu- 

 merus. 



