270 THE ARTICULATIONS 



The three dorsal ligaments (fig. 303) extend transversely and connect the greater with the 

 lesser multangular, the lesser multangular with the capitate, and the capitate with the hamate. 



The three volar ligaments are stronger than the dorsal, and are deeply placed beneath the 

 mass of flexor tendons; they extend transversely between the bones in a similar manner to the 

 dorsal ligaments. 



Three interosseous ligaments connect the bones of the lower row of the carpus together. 

 Two are connected with the capitate, one uniting it with the hamate (fig. 304) and the other 

 binding it to the lesser multangular. The third hgament joins the greater and lesser multangular. 



The synovial membrane is a prolongation of that lining the medio-carpal joint. 



The arterial and nerve -supplies are the same as for the medio-carpal joint. 



(c) The Medio-carpal Joint, or the Union of the Two Rows of the Carpus 



WITH EACH other 



(I) Class. — Diarthrosis. Subdivision. — Arthrodia. 



(II) Class. — Diarthrosis. Subdivision. — Condylarthrosis. 



The inferior surfaces of the bones of the first row are adapted to the superior 

 articular surfaces of the bones of the second row. The line of this articulation is 

 concavo-convex from side to side, and is sometimes described as having the course 

 of a Roman S placed horizontally, co , a resemblance by no means strained, (i) 

 The lateral part of the first row consists of the navicular alone; it is convex, and 

 bears the greater and lesser multangulars. .(ii) Then follows a transversely 

 elongated socket formed bj^ the medial part of the navicular, the lunate, and 

 triquetral, into which are received — (a) the head of the capitate, which articulates 

 with the navicular and lunate; (6) the upper and lateral angle of the hamate, which 

 articulates with the navicular; and (c) the upper convex portion of the medial 

 surface of the hamate, which articulates with the lateral and concave portion of 

 the inferior surface of the triquetral, (iii) The medial part of the inferior sur- 

 face of the triquetral bone is convex, and turned a little backward to fit into the 

 lower portion of the medial surface of the hamate, which is a little concave and 

 turned forward to receive it. The central part, which forms a socket for the capi- 

 tate and hamate, has somewhat the character of a condyloid joint, the capitate 

 and hamate being the condyle, to fit into the cavity formed by the navicular, 

 lunate, and triquetral; the other portions are typically arthrodial. The liga- 

 ments are: — (1) radiate or anterior medio-carpal; (2) posterior medio-carpal; 

 (3) transverse dorsal. 



The radiate, anterior or volar medio-carpal is a ligament of considerable strength, consisting 

 mostly of fibres which radiate from the capitate to the navicular, lunate, and triquetral; some 

 few fibres connect the greater and lesser multangular with the navicular, and others pass between 

 the hamate and triquetral. It is covered over and thickened by fibrous tissue derived from the 

 sheaths of the flexor tendons and the fibres of origin of the small muscles of the thumb and httle 

 finger. 



The posterior or dorsal medio-carpal ligament, consists of fibres passing obliquely from the 

 bones of the first row to those of the second. It is stronger on the ulnar side than on the radial, 

 but is not so strong as the volar ligament. 



The transverse dorsal ligament (fig. 303) is an additional band, well marked and often of 

 considoraljle strength, which passes across the head of the capitate from the navicular to the 

 triquetral bone; besides binding down the head of the capitate, it serves to fix the upper and lat- 

 eral angle of the hamate in the socket formed by the first row. 



The dorsal ligaments, like the volar, are strengthened by a quantity of fibrous tissue belong- 

 ing to the sheaths of the extensor tendons, and by an extension of some of the fibres of the capsule 

 of the wrist. There are no proper collateral medio-carpal hgaments; they are but prolongations 

 of the collateral ligaments of the wrist. 



The synovial membrane (fig. 304) of the carpus is common to all the joints of the carpus, 

 and extends to tlic bases of the four medial metacarpal bones. Thus, besides fining the inter- or 

 medio-carpal joint, it sends two processes upward between the three bones of the first row, and 

 three drnvnward between the contiguous surfaces of the lesser and greater multangular, the lesser 

 multangular and capitate, and capitate and hamate. From these latter, prolongations extend 

 to the four medial carpo-metararpal joints and the three intermetacarpal joints. 



The arterial supply is derived from — (a) the volar and dorsal carpal rami of the radial 

 and ulnar arteries; (h) the carpal l)raiich of the volar interosseous; (c) the recurrent branches 

 from the deep j)almar arch. The t(!rminal twigs of the volar and dorsal interosseous arteries 

 Hupjjly the joint on its dorsal aspect. 



The nerve-supply comes from t h(! ulnar on the ulnar side, the median on the radial side, and 

 the deep branch of the radial (yxjslcrior interosseous) behind. 



Relations. — The relations of this joint are practically the same as those of the radio-carpal 

 joint, except that the flexor carpi ulnaris does not cross the front, the ulnar artery is separated 



