REGION OF THE WRIST. 335 



flexor and extensor carpi ulnaris adducts the hand and contraction of the flexor carpi 

 radialis and extensor carpi radialis longior and brevior, aided by the short extensor 

 of the thumb and extensor ossis metacarpi pollicis, abducts the hand. 



In the affection known as wrist-drop all the extensor muscles are paralyzed. It is 

 due to injury, usually from pressure on the radial (musculospiral) nerve, either in the 

 groove of the humerus or in the axilla. Although there are a number of synovial 

 bursae around the joint in connection with the tendons none communicate with it. 



Muscles. The flexor tendons cover the wrist anteriorly and the extensors 

 posteriorly. With the flexor group we may consider the pronator quadratus. A 

 third or radial group comprises the extensor carpi radialis longior and brevior and 

 the brachioradialis. 



Anteriorly. The tendons on the front of the wrist occupy four different planes 

 or levels. The most superficial layer embraces the flexor carpi radialis, the palmaris 

 longus, and the flexor carpi ulnaris. Of these three the palmaris longus is the 

 nearest to the skin as it inserts in the palmar fascia in front of the annular ligament. 

 The flexor carpi radialis slips under the upper portion of the annular ligament to 

 insert into the base of the second metacarpal bone. The flexor carpi ulnaris inserts 



Flexor carpi ulnaris tendon 

 Deep layer of the deep fascia 



Superficial layer of the deep fascia / / u] nar artery 

 Anterior annular ligament / / / / Ulnar nerve 



Median nerve 

 Flexor sublimis tendons 



Tendon of palmaris longus I I I Radial artery 

 Superficial layer of deep fascia / Styloid process of radius 

 Flexor carpi radialis 



FIG. 345. Dissection showing the fascias of the anterior portion of the wrist. The superficial layer is 

 continuous with the palmaris longus muscle and palmar fascia; the deep layer is continuous with the anterior 

 annular ligament. 



into the pisiform bone and continues onward to the base of the fifth metacarpal bone 

 and the unciform process of the unciform bone. 



The second layer of tendons is composed of the four tendons of the flexor sub- 

 limis digitorum. They fill the space between the palmaris longus and the flexor 

 carpi ulnaris. 



The third layer is composed of the four tendons of the flexor profundus digito- 

 rum toward the ulnar side and the flexor longus pollicis toward the radial side. 



The fourth and last layer is formed by the pronator quadratus. This lies directly 

 on the bones and covers their lower fourth. 



It is sometimes necessary to divide these tendons in cases of contraction of the 

 wrist, hence the desirability of being able to recognize and locate them. 



The Deep Fascia and Anterior Annular Ligament. The deep fascia cov- 

 ering the anterior muscles of the forearm is comparatively thin. As it approaches the 

 wrist it divides into two layers. The superficial layer is thin and runs over the 

 tendons of the palmaris longus and flexor carpi radialis muscles and the ulnar artery 

 and nerve. It is continuous below with the palmar fascia. To the ulnar side it 

 passes oyer the flexor carpi ulnaris muscle to be continuous with the posterior annular 

 ligament. It is not attached to the ulna, but slides over it as it follows the move- 

 ments of the hand in pronation and supination (Fig. 345). 



