REGION OF THE WRIST. 339 



Above the wrist on the anterior and outer part can be felt the radius. Its lower 

 2 or 2.5 cm. (i in.) is sharp and prominent -this is the anterior border of the styloid 

 process. On the outer side at its base is the point of insertion of the brachioradialis 

 tendon. Following the bone down on its outer side, at the upper margin of the 

 anatomical snuff-box, one feels the tip of the styloid process, a most important 

 landmark. 



On the outer surface of the radius beginning below between the tip of the styloid 

 process and its sharp anterior border are the extensor ossis metacarpi pollicis and 

 extensor brevis pollicis tendons. They can readily be seen and felt when the thumb 

 is extended as they cross obliquely over the lower end of the radius. The sheaths 

 of these tendons frequently become inflamed from injuries, causing what is termed 

 tenosynovitis. If the hand is laid on the lower portion of the radius of a patient so 

 affected, and he is told to move the thumb, a characteristic creaking can be felt as 

 the tendons move in their inflamed sheaths. 



The edge of the articular surface of the radius can be indistinctly felt from the 

 tip of the styloid process to the edge of the flexor carpi radialis internally and across 

 the back of the wrist in an upwardly curved line toward the ulna. 



On the inner side of the wrist can be felt and seen the prominence made by the 

 head of the ulna. The ulna is subcutaneous and can be followed up the forearm 

 posteriorly its entire length. It is not covered by muscles on its inner border, but 

 on its anterior surface is the flexor carpi ulnaris tendon beneath which is the flexor 

 profundus digitorum, this latter being separated from the bone by the origin of the pro- 

 nator quadratus. If the posterior surface of the ulna is followed downward the styloid 

 process forming its extremity can be distinctly felt, especially if the hand is placed 

 in the supine position and slightly flexed. Overlying the head of the ulna posteriorly 

 is the tendon of the extensor carpi ulnaris muscle going to the base of the fifth meta- 

 carpal bone. This tendon follows the movements of the hand in pronation and 

 supination, but the styloid process of the ulna remains stationary. When the hand is 

 pronated the tendon lies to the anterior side of the styloid process, but when the hand 

 is supinated it lies toward its posterior side. This tendon cannot be readily recognized. 



The inner and posterior surface of the cuneiform bone can be felt immediately 

 below the head of the ulna. Some difficulty may be experienced in distinguishing 

 one from the other; if, however, the hand is abducted and adducted the cuneiform 

 bone can be felt to move while the ulna remains stationary. On the palmar surface 

 of the wrist, immediately below the ulna, can be felt the distinct bony prominence 

 formed by the pisiform bone. The flexor carpi ulnaris inserts into it. 



About 2 to 2. 5 cm. ( i in. ) below and to the radial side of the pisiform bone is 

 the unciform process of the unciform bone. It is best detected by laying the ball of 

 the thumb over the spot and making deep pressure with a rolling motion. On the 

 radial side of the anterior surface, directly in line with the tendon of the flexor carpi 

 radialis, is the prominent tubercle of the navicular (scaphoid) bone; a centimetre 

 farther on, in line with the thumb, is the ridge of the trapezium. The anterior annular 

 ligament is attached to its outer surface about 2.5 cm. (i in. ) below the styloid proc- 

 ess of the radius ; a bony prominence formed by the trapezium marks its junction 

 with the metacarpal bone of the thumb in front. 



The ability to locate the carpometacarpal joint of the thumb is of importance 

 in reference to the diagnosis of fractures and other injuries. On comparing the two 

 styloid processes it will be seen that the styloid process of the radius extends i cm. 

 (f in. ) lower than that of the ulna. This is best observed with the hand in a prone 

 position. Across the front of the wrist there are two transverse lines. The proxi- 

 mal or upper one corresponds with the radiocarpal joint or wrist-joint. The distal or 

 lower one corresponds with the joint between the two rows of carpal bones and 

 marks the upper edge of the anterior annular ligament. 



On the posterior surface of the wrist, one-third of the width of the wrist across 

 from the edge of the radius, can be felt a bony prominence. It is the posterior radial 

 tubercle. If the thumb is extended the tendon of the extensor longus pollicis leads 

 directly to the tubercle and lies along its ulnar border. This tubercle marks the middle 

 of the posterior surface of the radius. The radius passes two-thirds across the wrist 

 and the ulna the other third; by firm pressure the interval between them can be felt. 



