REGION OF THE ELBOW. 291 



the artery to reach its inner side. This vein is encountered as soon as the skin is 

 divided, hence care is necessary to avoid wounding it. It should be displaced to the 

 inner side along with a filament of the cutaneous nerve if this is present. The inci- 

 sion is then deepened through the upper portion of the bicipital fascia and the artery 

 found beneath, lying in loose fatty tissue and accompanied by two venae comites. 

 The median nerve lies to the inner side but may be sufficiently removed not to be 

 exposed. The needle is passed from the inner towards the outer side (Fig. 301). 



Collateral Circulation. On the outer side the profunda (superior) anastomoses 

 with the interosseous recurrent (a branch of the posterior interosseous) and radial 

 recurrent. On the inner side the superior ulnar collateral (inferior profunda) and 

 inferior ulnar collateral (anastomotica magna) anastomose with the anterior and 

 posterior ulnar recurrent arteries (Fig. 302). 



DISLOCATIONS OF THE ELBOW. 



In dislocation of the elbow the bones of the forearm are most commonly displaced 

 backward. More rarely they may be partially displaced either inwardly or outwardly 

 and with or without an accompanying backward displacement. The lateral ligaments 



External condyle 

 of humerus 



Head of radius 



Olecranon 

 FIG. 303. Posterior luxation of the elbow; surface view of the outer side. 



are strong, the anterior and posterior weak. The formation of the bones permits 

 anteroposterior movement and resists lateral movement; hence the frequency of 

 anteroposterior and the rarity of lateral luxations. To understand and recognize these 

 dislocations and distinguish between them and fractures requires a knowledge of the 

 shape of the bones, the position of the articulations, and especially of the relations 

 and significance of the various bony prominences, in other words, surface anatomy. 

 In doubtful cases compare the normal with the injured elbow. 



Backward Dislocation of the Elbow. In backward dislocation the radius 

 and ulna are pushed backward and the lower end of the humerus comes forward. It 

 is most commonly caused by falls on the outstretched hand and not by direct injury 

 to the elbow. 



On the cadaver hyperextension with or even without a slight twisting readily 

 produces the displacement. 



The internal and external lateral ligaments are torn loose from their respective 

 condyles and the anterior ligament is ruptured. The posterior ligament is stretched 



