7S ANATOMY IN A NUTSHELL. 



LESSON XVIII. 



The wrist-joint is a condyloid joint (Plate XL) having all movements ex- 

 cept axial rotation. It is formed by the lower head of the radius and the inter- 

 articular fibro-cartilage proximally and the scaphoid, semilunar, and cuneiform 

 bones distally. The ulna docs not go into the joint, being separated by the 

 interarticular fibro-cartilage from the done- of the wrist. 



The ligaments of this joint arc the anterior, posterior, internal lateral, and 

 external lateral which make a capsular ligament. The anterior ligament ex- 

 tend- from the anterior surface of the lower border of the ulna to the front of 

 the interarticular fibro-cartilage, also from the anterior surface of the lower 

 border of the radius and its styloid process, to the palmar surface of the scap- 

 hoid, semilunar, and cuneiform bones distally, some fibers continuing to the c* 

 magnum and the unciform hones. There are some superficial fibers passing 

 from the styloid process ^i the ulna to the semilunar and cuneiform. This 

 ligamenl is pierced by small vessels. The posterior ligament is weaker than the 

 anterior one: it extend- from the posterior surface of the lower part of the radius 

 and the triangular interarticular fibro-cartilage to the posterior surface of the 

 scaphoid, semilunar and cuneiform bones. The internal lateral ligament ex- 

 tends from the tip of the styloid process of the ulna to the inner surface of the 

 cuneiform, by one of its divisions, and to the pisiform and annular ligament by 

 the other. The external lateral ligament extends from the styloid process of 

 the radius to the outer side of the scaphoid, some fibers continuing to the trape- 

 zium and annular ligament. 



A synovial membrane which is very lax and does not communicate with 

 the joint above and below, lines the ligaments of this joint. (Plate XLII.) 



The nerve supply is the ulnar, anterior and posterior interosseous. 



The blood supply is the anterior and posterior interosseous, anterior and 



erior carpal arches, and recurrent branches from the dee]) palmar arch. 



The superior radio-ulnar articulation is a trochoides, and is formed by the 

 head of the radius and the lesser sigmoid cavity of the ulna. Its only liga- 

 menl i- the orbicular, which surrounds the head of the raidus. It is connected 

 io the anterior and posterior borders of the lesser sigmoid cavity, and with it 

 make- a complete ring. It- lower circumference is less than that of the upper, 

 thus holding the head <<\ the radius in position. It blends with all the liga- 

 ments of the elbow, except the internal: the synovial membrane continues with 



that of the elbow. 



The middle radio-ulnar articulation has two ligaments: first, the oblique 

 ..i- round ligament which passes distally and outward from the base of the 

 coronoid process to the bicipital tuberosity of the radius. This ligament is 

 often absent. Second, the interosseous membrane, passing between the two 

 adjacent border- of the radius and ulna: its liber- pass distally and inward. It 

 commences beyond the bicipital tuberosity of the radius and extends almost to 

 the di-tal extremity of the two bones. It affords attachment to the muscles. 

 The anterior interosseous artery passes to the back of the forearm, between the 

 radius and ulna beyondthis membrane. The posterior interosseous vessels pass 



