OF THE CARPUS. 357 



forated by numerous apertures for the passage of vessels, and is in relation, in 

 front, with the tendons of the Flexor profundus digitorum and Flexor longus pol- 

 licis : behind, with the synovial membrane of the wrist-joint. 



The Posterior Ligament (Fig. 249), less thick and strong than the anterior, is 

 attache'!, above, to the posterior border of the lower end of the radius ; its fibres 

 obliquely downward and inward, to be attached to the dorsal surface of the 

 scaphoid, semilunar, and cuneiform bones, being continuous with those of the 

 dorsal carpal ligaments. This ligament is in relation, behind, with the extensor 

 tendons of the fingers ; in front, with the synovial membrane of the wrist. 



The Synovial Membrane (Fig. 251) lines the inner surface of the ligaments 

 above described, extending from the lower end of the radius and interarticular 

 fibro-cartilage above to the articular surfaces of the carpal bones below. It is 

 and lax. and presents numerous folds, especially behind. 



Relations. The wrist-joint is covered in front by the flexor and behind by the 

 extensor tendons ; it is also in relation with the radial and ulnar arteries. 



The Arii- 1- i i' .* supplying the joint are the anterior and posterior carpal branches 

 of the radial and ulriar, the anterior and posterior interosseous. and some ascending 

 branches from the deep palmar arch. 



The X> /' .- are derived from the ulnar and posterior interosseous. 



Actions. The movements permitted in this joint are flexion, extension, abduc- 

 tion, adduction, and circumduction. Its actions will be further studied with those 

 of the carpus, with which they are combined. 



Surface Form. The line of the radio-carpal joint is on a level with the apex of the styloid 

 the ulna. 



Surgical Anatomy .-j-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 strung ligaments. The slight movement which takes place between the several bones 



- tu break the jars that result from falls or blows on the hand. Dislocation backward, 

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

 is liable to be mistaken i'or it. The diagnosis can be easily made out by observing the 

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

 styloid prix-oss of the radius is on a lower level f. e. nearer the ground when the arm hangs by 

 the >ide. than that of the ulna, and the same would be the case in dislocation. In Colles' frac- 

 ture, 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 arising 

 in the rheumatic or pya?mic state. When the synovial sac is distended with fluid, the swelling 

 (test on the dorsal aspect of the wrist, showing 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 

 tubercular, and often leads to similar disease in the synovial sheaths of adjacent tendons and of ' 

 the intercarpal joints. The disease, therefore, when progressive, often leads to necrosis of the 

 carpal bones, and the result is often unsatisfactory. 



VIII. Articulations of the Carpus. 

 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 BOXES. 



These are arthrodial joints. The ligaments connecting the scaphoid, semilunar, 

 and cuneiform bones are 



Dorsal. Palmar. 



Two Interosseous. 



The Dorsal Ligaments are placed transversely behind the bones of the first 



row ; they connect the scaphoid and semilunar and the semilunar and cuneiform. 



The Palmar Ligaments connect the sea] hoid and semilunar and the semilunar 



