160 THE UPPER EXTREMITY 



where they complete the distal surface of the radio-carpal 

 joint. 



The members of the distal row of carpal bones are 

 bound together by three dorsal, three volar, and three inter- 

 osseous ligaments which pass transversely between the adjacent 

 bones. The interosseous ligament between the os capitatum 

 and the os hamatum is very strong ; that between the os 

 capitatum and the os multangulum minus is weak and not 

 uncommonly absent. 



At present the interosseous ligaments between the bones of the distal row 

 are hidden from view, but they can be studied when the transverse part of 

 the intercarpal joint is opened. 



The transverse part of the intercarpal joint lies between 

 the proximal and distal rows of carpal bones. The two rows 

 of bones are bound together by a capsular ligament which is 

 attached to the volar and dorsal surfaces and the medial and 

 lateral borders of each row. The lateral and medial parts 

 of the capsule are sometimes spoken of as the lateral and 

 medial ligaments of the transverse carpal joint. The volar 

 and dorsal parts of the capsule are strengthened by numerous 

 bands of fibres. The bands on the dorsal surface are irregular 

 in number and strength, but those on the volar surface are 

 better marked and, for the most part, they radiate from the 

 os capitatum to the surrounding bones forming the ligamentum 

 carpi radiatum. One of the bands of this ligament passes 

 from the os capitatum to the styloid process of the radius and 

 blends with the radial collateral ligament of the radio-carpal 

 joint. 



Articular Surfaces. The individual bones of the upper 

 row and the individual bones of the lower row articulate with 

 each other by flat surfaces. In the transverse part of the 

 intercarpal articulation the proximal parts of the os capitatum 

 and the os hamatum form a high convexity which fits into a 

 concavity formed by the distal surfaces of the os triquetrum 

 and os lunatum and the distal part of the medial surface 

 of the naviculare of the proximal rows; and the convex 

 distal surface of the os naviculare is received into a concavity 

 formed by the proximal surfaces of the greater and lesser 

 multangular bones. The two opposed surfaces of the trans- 

 verse part of the joint are, therefore, concavo-convex from 

 side to side, and adapted one to the other. 



