

THE CARPUS 



an oval facet, for articulation with the pisiform; its lateral part is rough for liga- 

 mentous attachment. The lateral surface, the base of the pyramid, is marked by a 

 flat, quadrilateral facet, for articulation with the lunate. The medial surface, 

 the summit of the pyramid, is pointed and roughened, for the attachment of the 

 ulnar collateral ligament of the wrist. 



Ar^culations. The triangular articulates with three bones: the lunate laterally, the pisiform 

 in front, the hamate distally; and with the triangular articular disk which separates it from the 

 lower end of the ulna. 



The Pisiform Bone (os pisiforme) (Fig. 224). The pisiform bone may be known 

 by its small size, and by its presenting a single articular facet. It is situated on a 

 plane anterior to the other carpal bones and is spheroidal in form. Its dorsal 

 surface presents a smooth, oval facet, for articulation with the triangular: this facet 

 approaches the superior, but not the inferior border of the bone. The volar surface 

 is rounded and rough, and gives attachment to the transverse carpal ligament, 

 and to the Flexor carpi ulnaris and Abductor digiti quinti. The lateral and medial 

 surfaces are also rough, the former being concave, the latter usually convex. 



Articulation. The pisiform articulates with one bone, the triangular. 



Bones of the Distal Row (lower row}. The Greater Multangular Bone (os mul- 

 iangulum majus; trapezium) (Fig. 225). The greater multangular bone may be 

 distinguished by a deep groove on its volar surface. It is situated at the radial 

 side of the carpus, between the navicular and the first metacarpal bone. The 

 superior surface is directed upward and medialward; medially it is smooth, and 

 articulates with the navicular ; laterally it is rough and continuous with the lateral 

 surface. The inferior surface is oval, concave from side to side, convex from before 

 backward, so as to form a saddle-shaped surface for articulation with the base 



For lesser 

 multangular 



Groove 



For navicular 



lor 2nd 

 metacarpal 



Ridge 



FIG. 225. The left greater multangular bone. 



For lesser 

 multangular 



For '2nd metacarpal 



)f the first metacarpal bone. The dorsal surface is rough. The volar surface is 

 larrow and rough. At its upper part is a deep groove, running from above obliquely 

 lownward and medialward; it transmits the tendon of the Flexor carpi radialis, 

 and is bounded laterally by an oblique ridge. This surface gives origin to the 

 Opponens pollicis and to the Abductor and Flexor pollicis brevis; it also affords 

 attachment to the transverse carpal ligament. The lateral surface is broad and 

 rough, for the attachment of ligaments. The medial surface presents two facets; 

 the upper, large and concave, articulates with the lesser multangular; the lower, 

 small and oval, with the base of the second metacarpal. 



Articulations. The greater multangular articulates with four bones : the navicular proximally, 

 the first metacarpal distally, and the lesser multangular and second metacarpal medially. 



The Lesser Multangular Bone (os multangulum minus; trapezoid bone) (Fig. 226). 

 -The lesser multangular is the smallest bone in the distal row. It may be known 

 by its wedge-shaped form, the broad end of the wedge constituting the dorsal, 

 the narrow end the volar surface; and by its having four articular facets touching 

 ich other, and separated by sharp edges. The superior surface, quadrilateral, 

 15 



