Limbs : Upper Limb 



95 



subcutaneous area, in relation with which are a couple of small subcutaneous bursae. 

 Its inner side has rough markings for the internal lateral ligament and, behind and 

 below these, the attachment of the fibrous arch that carries the origin of Flexor carpi 

 ulnaris from the inner condyle to reach the inner margin of the subcutaneous area, 

 and thus to pass to the subcutaneous border. Externally is a definite ridge for the 

 external lateral ligament, and behind this a slightly hollowed surface for the upper 

 part of the Anconeus insertion. 



Coronoid. Cartilage covering upper 

 surface is continuous with that in lesser 

 sigmoid notch. Front surface (Fig. 75) is 

 an elongated triangular area, with a rough 

 tuberosity for tendon of Brachialis anticus, 

 above this an occasional bursal area, then 

 marking for anterior capsular fibres, then a 

 marginal synovial area. The inner and 

 outer margins afford attachments to struc- 

 tures as shown in Fig. 75. The ulnar 

 artery crosses the lower part of the inner 

 margin, running off the Brachialis anticus 

 in a downward, inward, and backward direc- 

 tion on to the Flexor profundus ; it there- 

 fore passes here deep to the deep head of 

 Pronator teres, which separates it from the 

 median nerve (Figs. 76 and 77). 



Below the lesser sigmoid cavity is a 

 triangular hollow area : articulate the two 

 bones and rotate the radius, and it be- 

 comes clear that the tubercle of this bone 

 with its attached tendon requires the room 

 afforded by this hollow to enable it to rotate. 

 There is no space here for the attachment of 

 muscles, so the ulnar origin of Supinator 

 brevis is by thin aponeurosis from the back 

 margin only of this area : a few muscle fibres 

 may arise, however, just in front of this. 



The head has really two articular sur- 

 faces which are continuous, a lower one for 

 the triangular fibro -cartilage, and a circumferential one for the radius : owing to the 

 extent of movement of the radius, this last surface is on two aspects of the head. When 

 the hand is pronated, the postero-lateral articular surface on the ulna causes the pro- 

 minence visible on the inner part of the back of the wrist (Fig. 74). 



The capsular fibres are lax and make little marking on the bone. The fibro- 

 cartilage is fastened by fibrous bands to the depression on the outer side of the base of 

 the styloid process : external to this the head of the bone is articular. The styloid 

 process has the internal lateral ligament of the wrist attached to it : as this is almost 

 in the line of the axis of rotation, the ligament does not interfere with pronation and 

 supination. 



In mid-foetal life the styloid process articulates with the cuneiform bone in the carpus, but this 

 connection has become ligamentous at birth. 



FIG. 74. The axis round which the radius turns 

 is seen to pass through the head of that 

 bone above, and through the head of the 

 ulna below ; these two points are the 

 centres of the circles of which the circum- 

 ferences of the heads are segments. Thus 

 the radius rotates in the small sigmoid 

 cavity of ulna above but moves round that 

 bone below. Observe that in pronation the 

 part of the head of the ulna which projects 

 behind is covered by the radius in supina- 

 tion. 



