THE FOREARM AND WRIST 71 



the flexor digitorum profundus. It runs downwards in front 

 of the latter and it is covered by the flexor carpi ulnaris in the 

 proximal two-thirds of the forearm. Distally it again becomes 

 superficial, lying between the most medial tendon of the flexor 

 digitorum sublimis, on the radial side, and the tendon of the 

 flexor carpi ulnaris, on the ulnar side. At the junction of the 

 proximal and middle thirds of the forearm, it becomes associated 

 with the ulnar artery, which lies close to its lateral side through- 

 out the remainder of their course in this region. 



About three inches from the pisiform, the ulnar nerve gives 

 off palmar (p. 82) and dorsal cutaneous branches. The latter 

 passes backwards below the styloid process of the ulna, crosses 

 the medial surface of the os triquetrum (cuneiform) and gains 

 the dorsum of the hand, where it supplies the little finger and 

 the ulnar side of the ring finger (p. 72). This nerve runs some 

 risk of being cut in the ulnar incision for excision of the wrist. 



Ulnar Artery. In ligature of the ulnar artery in its 

 distal two-thirds, the incision should be made in the line of the 

 ulnar nerve. In the middle third, the flexor carpi ulnaris, 

 which overlies it, must be retracted to the medial side. The 

 course of the proximal third is indicated by a line drawn from 

 the termination of the brachial artery (p. 42) to the point 

 where the ulnar artery becomes associated with the ulnar nerve. 

 As it lies deeply under cover of the superficial group of muscles 

 and is crossed close to its origin by the median nerve, the artery 

 is rarely tied in this part of its course. 



Branches. The volar and dorsal ulnar recurrent (p. 44) 

 branches arise near the origin of the ulnar artery. 



The Common Interosseous arises more distally and at once 

 divides into Volar (Anterior) and Dorsal branches. The former 

 runs distally in front of the interosseous membrane and 

 communicates with the volar carpal arch. It pierces the 

 membrane at the proximal border of the pronator quadratus 

 and anastomoses with the dorsal carpal arch and the dorsal 

 interosseous artery. The latter passes backwards proximal to 

 the membrane to supply the extensor muscles, and becomes 

 associated with the dorsal interosseous nerve. 



The Superficial (Radial) Branch of the Radial (Musculo- 

 Spiral) Nerve arises in front of the lateral epicondyle under 

 cover of the brachio-radialis. It approaches the radial artery 

 and lies close to its lateral side in the middle third of the forearm. 

 About 3 1 inches from the styloid process of the radius the 



56 



