354 



THE ARTICULATIONS. 



the body by the little dimple on the back of the forearm which indicates the position of the head 

 of the radius. 



Surgical Anatomy. Dislocation of the head of the radius alone is not an uncommon 

 accident, and occurs most frequently in young persons from falls on the hand when the forearm 

 is extended and supinated, the head of the bone being displaced forward. It is attended by 

 rupture of the orbicular ligament. 



2. MIDDLE RADIO-ULNAR ARTICULATION. 



The interval between the shafts of the radius and ulna is occupied by two 

 ligaments. 



Oblique. Interosseous. 



The Oblique or Round Ligament (Fig. 245) is a small, flattened fibrous band 

 which extends obliquely downward and outward from the tubercle of the ulna at 

 the base of the coronoid process to the radius a little below the bicipital tuberosity. 

 Its fibres run in the opposite direction to those of the interosseous ligament, and 

 it appears to be placed as a substitute for it in the upper part of the interosseous 

 interval. This ligament is sometimes wanting. 



The Interosseous Membrane is a broad and thin plane of fibrous tissue descending 

 obliquely downward and inward, from the interosseous ridge on the radius to that 



Inferior radio-ulnar 

 articulation. 



Wrist-joint. 



Carpal articulations. 



po-metacarpal 

 articulations. 



FIG. 248. Ligaments of wrist and hand. Anterior view. 



on the ulna. It is deficient above, commencing about an inch beneath the tubercle 

 of the radius ; is broader in the middle than at either extremity ; and presents an 

 oval aperture just above its lower margin for the passage of the anterior inter- 

 osseous vessels to the back of the forearm. This ligament serves to connect the 

 bones and to increase the extent of surface for the attachment of the deep muscles. 

 Between its upper border and the oblique ligament an interval exists through 

 which the posterior interosseous vessels pass. Two or three fibrous bands are 

 occasionally found on the posterior surface of this membrane which descend 

 obliquely from the ulna toward the radius, and which have consequently a direc- 

 tion contrary to that of the other fibres. It is in relation, in front, by its upper 

 three-fourths with the Flexor longus pollicis on the outer side, and with the 

 Flexor profundus digitorum on the inner, lying upon the interval between which 

 are the anterior interosseous vessels and nerve ; by its lower fourth, with the 

 Pronator quadratus ; behind, with the Supinator brevis, Extensor ossis metacarpi 



