THE BONES OF THE UPPER LIMB l8g 



surface covered by cartilage, and divided by a vertical curved 

 ridge into an external part, called the capitellura, and an internal, 

 called the trochlea. Above the capitellum in front there is a rough 

 transverse depression, called the radial fossa. Above the trochlea 

 in front is the coronoid fossa, and above it posteriorly is the olecranon 

 fossa. 



The internal epicondyle {epitrochlea) is very prominent, and is 

 directed inwards and slightly backwards. Its lower part and the 

 adjacent portions of its anterior and posterior aspects give attach- 

 ment to the internal lateral ligament of the elbow- joint. Its anterior 

 aspect gives origin to the cormnon tendon of the superficial head of 

 the pronator radii teres, flexor carpi radialis, palmaris longus, part 

 of the flexor sublimis digitorum, and one head' of the flexor carpi 

 ulnaris. Behind the internal epicondyle, close to the trochlea, is the 

 ulnar groove, through which the ulnar ner\^e passes. 



The external epicondyle is much less prominent than the internal. 

 Anteriorly it gives origin to the common tendon of the extensor 

 carpi radialis brevior, extensor communis digitorum, extensor minimi 

 digiti, extensor carpi ulnaris, and supinator radii brevis. Posteriorly 

 it presents an impression for the anconeus, and inferiorly a depres- 

 sion near the capiteUmn for the external lateral ligament of the 

 elbow-joint. 



The capitellum mainly takes the form of a rounded eminence. 

 It is limited to the anterior and inferior aspects of the bone, and 

 articulates with the cup-shaped depression on the head of the 

 radius. Internal to the rounded portion there is a groove for the 

 play of the inner convex part on the head of the radius. The 

 radial fossa receives the anterior margin of the head of the radius 

 in complete flexion of the elbow-joint. 



The trochlea is puUey-shaped, and turns completely round from 

 the front to the back of the bone, becoming rather broader pos- 

 teriorly. It is concave from side to side, and convex from before 

 backwards. The internal border is more prominent and thicker 

 than the external, and extends lower down. As viewed from 

 before, the borders are inclined do\vnwards and slightly inwards, 

 but posteriorly they incline upwards and slightly outwards, and so 

 the trochlea is here brought into the centre of the bone. The 

 trochlea articulates with the great sigmoid cavity of the ulna. The 

 coronoid fossa receives the coronoid process of the ulna in flexion 

 of the elbow- joint, and the anterior ligament is attached just above 

 it. The olecranon fossa, much larger than the coronoid, receives the 

 olecranon process of the ulna in extension of the joint, and its margins 

 give attachment to the posterior ligament. The portion of bone 

 which separates the two fossae is thin, and is sometimes perforated 

 by a foramen, called the supratrochlear foramen. 



In the vicinity of the lower extremity there are numerous nutrient 

 foramina for branches of the superior and inferior profunda and 

 anastomotica magna of the brachial, radial and ulnar recurrent, 

 and interosseous recurrent, arteries. 



