ARTICULATIONS OF THE, CARPUS 315 



lunar and cuneiform bones. This ligament is perforated by numerous apertures 

 fer the passage of vessels, and is in relation, in front, with the tendons of the 

 Flexor profundus digitorum and of the Flexor longus pollicis. 



The posterior or dorsal ligament (ligamentum radiocarpeum dorsale) (Fig. 254), 

 thinner and weaker than the anterior, is attached, above, to the posterior border 

 of the lower end of the radius; its fibres pass obliquely downward and inward, to 

 be attached to the dorsal surface of the scaphoid, semilunar, and cuneiform bones, 

 and are continuous with those of the dorsal carpal ligaments. This ligament 

 is in relation, behind, with the Extensor tendons of the ringers. 



Synovial Membrane. The synovial membrane (Fig. 256) lines the inner surface of the 

 ligaments above described, extending from the lower end of the radius and articular disk above 

 to the articular surfaces of the carpal bones below. It is loose and lax, and presents numerous 

 folds, especially behind. 



The arteries supplying the joint are the anterior and posterior carpal branches of the radial 

 and ulnar, the anterior and posterior interosseous, and some ascending branches from the deep 

 palmar arch. 



The nerves are derived from the ulnar and posterior interosseous. 



Movements. The movements permitted in this joint are flexion, extension, abduction, 

 adduction, and circumdudion. Its actions will be further studied with those of the carpus, with 

 which they are combined. 



Surface Form. The line of the radiocarpal joint is on a level with the apex of the styloid 

 process of the ulna. 



Applied Anatomy. The wrist-joint is rarely dislocated, its strength depending mainly upon 

 the numerous strong tendons which surround the articulation. Its security is further pro- 

 vided for by the number of small bones of which the carpus is made up, and which are united 

 by very strong ligaments. The slight movement which takes place between the several bones 

 serves to break the jars that result from falls or blows on the hand. Dislocation backward, 

 which is the more common dislocation, simulates to a considerable extent Colles' fracture of the 

 radius, and is apt to be mistaken for it. The diagnosis can be easily made out by observing 

 the relative position of the styloid processes of the radius and ulna. In the natural condition 

 the styloid process of the radius is on a lower level i. e., nearer the ground when the arm hangs 

 by the side, than that of the ulna, and the same would be the case in dislocation. In Colics' 

 fracture, on the other hand, the styloid process of the radius is on the same or even a higher 

 level than that of the ulna. 



The wrist-joint is occasionally the seat of acute synovitis, the result of traumatism or con- 

 sequent upon rheumatic or pyemic conditions. When the synovial sac is distended with fluid, 

 the swelling is greatest on the dorsal aspect of the wrist, and shows a general fulness, with some 

 bulging between the tendons. The inflammation is prone to extend to the intercarpal joints and 

 to attack also the sheaths of the tendons in the neighborhood. Chronic inflammation of the wrist 

 is generally tuberculous, and often leads to similar disease in the synovial sheaths of adjacent 

 tendons and of the intercarpal joints. The disease, therefore, when progressive, frequently 

 leads to necrosis of the carpal bones, and the result is often unsatisfactory. 



VIII. Articulations of the Carpus (Articulatio Intercarpea) (Figs. 253, 254). 



These articulations may be subdivided into three sets: 



1. The Articulations of the First Row of Carpal Bones. 



2. The Articulations of the Second Row of Carpal Bones. 



3. The Articulations of the Two Rows with each other. 



1. ARTICULATIONS OF THE FIRST Row OF CARPAL BONES 



These are arthrodial joints. The ligaments connecting the scaphoid, semi- 

 lunar, and cuneiform bones are: 



Dorsal. Palmar. 



Two Interosseous. 



