

SURFACE MARKINGS OF THE UPPER EXTREMITY 1331 



the radius to the radial side of the wrist-joint, whence it is continued on to 

 the dorsal surface of the thumb as a ridge best marked when the thumb is 

 extended. 



The tendons of most of the Extensor muscles can be seen and felt on the back 

 of the wrist. Laterally is the oblique ridge produced by the Extensor pollicis 

 longus. The Extensor carpi radialis longus is scarcely palpable, but the Extensor 

 carpi radialis brevis can be identified as a vertical ridge emerging from under the 

 ulnar border of the tendon of the Extensor pollicis longus when the wrist is extended. 

 Medial to this the Extensor tendons of the fingers can be felt, the Extensor digiti 

 quinti proprius being separated from the tendons of the Extensor digitorum 

 communis by a slight furrow. 



The muscles of the hand are principally concerned, as regards surface form, in 

 producing the thenar and hypothenar eminences, and cannot be individually dis- 

 tinguished ; the thenar eminence, on the radial side, is larger and rounder than the 

 hypothenar, which is a long narrow elevation along the ulnar side of the palm. 

 When the Palmaris brevis is in action it produces a wrinkling of the skin over the 

 hypothenar eminence and a dimple on the ulnar border. On the back of the hand 

 the Interossei dorsales give rise to elongated swellings between the metacarpal 

 bones; the first forms a prominent fusiform bulging when the thumb is adducted, 

 the others are not so marked. 



Arteries. Above the middle of the clavicle the pulsation of the subclavian artery 

 can be detected by pressing downward, backward, and medialward against the 

 first rib. The pulsation of the axillary artery as it crosses the second rib can be 

 felt below the middle of the clavicle just medial to the coracoid process; along the 

 lateral wall of the axilla the course of the artery can be easily followed close to the 

 medial border of Coracobrachialis. The brachial artery can be recognized in practi- 

 cally the whole of its extent, along the medial margin of the Biceps; in the upper 

 two-thirds of the arm it lies medial to the humerus, but in the lower third is more 

 directly on the front of the bone. Over the lower end of the radius, between the 

 styloid process and Flexor carpi radialis, a portion of the radial artery is superficial 

 and is used clinically for observations on the pulse. 



Veins. The superficial veins of the upper extremity are easily rendered visible 

 by compressing the proximal trunks; their arrangement is described on pages 660 

 to 662. 



Nerves. The uppermost trunks of the brachial plexus are palpable for a short 

 distance above the clavicle as they emerge from under the lateral border of Sterno- 

 cleidomastoideus; the larger nerves derived from the plexus can be rolled under the 

 finger against the lateral axillary wall but cannot be identified. The ulnar nerve 

 can be detected in the groove behind the medial epicondyle of the humerus. 



SURFACE MARKINGS OF THE UPPER EXTREMITY. 



Bony Landmarks. The bony landmarks as described above are so readily avail- 

 able for surface recognition that no special measurements are required to indicate 

 them. It may be noted, however, that the medial angle of the scapula is applied 

 to the second rib, while the inferior angle lies against the seventh. The intertuber- 

 cular groove of the humerus is vertically below the acromioclavicular joint when 

 the arm hangs by the side with the palm of the hand forward. 



Articulations. The acromioclavicular joint is situated in a plane passing sagit- 

 tally through the middle line of the front of the arm. The line of the elbow-joint 

 is not straight; the radiohumeral portion is practically at right angles to the long 

 axis of the humerus and is situated about 2 cm. distal to the lateral epicondyle; 

 the ulnohumeral portion is oblique, and its medial end is about 2.5 cm. distal to the 

 medial epicondyle. The position of the wrist-joint can be indicated by drawing a 





