42 THE SUPERIOR EXTREMITY 



through the brachialis in front and the triceps behind, provided 

 that the muscles are relaxed by supporting the elbow. 



Fractures of the Humerus. Some reference must be 

 made to the common sites of fracture of the humeral shaft on 

 account of the displacement of the fragments. Although the 

 displacements may be due primarily to the direction of the 

 force causing the fracture, ultimately they are due to the action 

 of the muscles attached to the fragments. 



Fractures may occur : 



1. Through the Anatomical Neck (p. 23). 



2. Through the Surgical Neck. The proximal fragment 

 is slightly abducted by the supra-spinatus, but is not rotated, 

 as the lateral rotators attached to the greater tubercle are 

 opposed by the subscapularis on the lesser tubercle. The 

 distal fragment is drawn proximally by the triceps, the biceps, 

 and the deltoid, and medially by the muscles inserted into the 

 intertubercular sulcus (bicipital groove). 



3. Immediately Proximal to the Insertion of the Deltoid. 

 The proximal fragment is adducted by the latissimus 

 dorsi, the pectoralis major, and the teres major. The distal 

 fragment is drawn proximally by the deltoid, the triceps, and 

 the biceps. 



4. Distal to the Insertion of the Deltoid. The proximal 

 fragment tends to be abducted by the deltoid. The distal 

 fragment is drawn proximally and somewhat medially by the 

 biceps and the triceps, which act through the elbow-joint. 



5. Proximal to the Epicondyles (p. 63). The distal 

 fragment is usually drawn proximally behind the proximal 

 fragment by the biceps and the triceps. The distal end of the 

 proximal fragment may perforate the brachialis and injure the 

 brachial artery. 



The Musculo-cutaneous nerve, on leaving the axillary 

 artery (p. 33), supplies the coraco-brachialis and then pierces it. 

 It runs distally between the biceps in front and the brachialis 

 behind, supplying both muscles, and emerges at the elbow at 

 the lateral side of the tendon of the biceps (p. 47). The results 

 of injury to this nerve are detailed on p. 102. 



The Brachial Artery is the direct continuation of the 

 axillary. It begins at the lower border of the teres major and 

 ends in the cubital fossa (p. 45), half an inch distal to the 

 mid -point of the line joining the two epicondyles, where it 

 divides into the radial and ulnar arteries. 



