162 THE SKELETON 



The Pisiform 



The pisiform [os pisiforme] (fig. 193), the smallest of the carpal bones, is in 

 many of its characters a complete contrast to the rest of the series. It deviates 

 from the general type in its shape, size, position, use, and development. Forming 

 a rounded bony nodule with the long axis directed vertically, it is situated on a 

 plane in front of the other bones of the carpus. 



Fig. 193. — The Left Pisiform. 



For triquetral- 



On the dorsal surface is a single articular facet for the triquetral which reaches to the upper 

 end of the bone, but leaves a free non-articular portion below. The volar surface, rough and 

 rounded, gives attachment to the transverse carpal ligament, Wve flexor carpi ulnaris, the ab- 

 ductor quinti digiti, the piso-metacarpal and the piso-hamate ligaments. The median and lateral 

 surfaces are also rough and the lateral presents a shallow groove for the ulnar artery. It is 

 usually considered that the pisiform is a sesamoid bone developed in the tendon of the flexor 

 carpi ulnaris, though by some writers it is regarded as part of a rudimentary digit. 



The Greater Multangular 



The greater multangular [os multangulum majus] or trapezium (fig. 194), 

 situated between the navicular and first metacarpal, is oblong in form with the 

 lower angle prolonged downward and medially. 



Fig. 194. — The Left Greater Multangular. 



"3^ m ^^^ ridge 



For navicular 7% 'jJ is>«iPr- Vk , ^ • j- i- 



V I ' '^^^ ^^S Groove for flexor carpi radialis 



For lesser multangular Wl-i'fJ^^^^^ 



flfW/^ —For first metacarpal 



For second metacarpal — ^^ \aL/ 



The superior surface is concave and directed upward and medially for articulation with the 

 lateral of the two facets on the distal surface of the navicular, and on the inferior surface is a 

 saddle-shaped facet for the base of the first metacarpal. The volar surface presents a prominent 

 ridge with a deep groove on its medial side which transmits the tendon of Wxe. flexor carpi radialis. 

 The ridge gives attachment to the transverse carpal ligament, the abductor pollicis brevis, the 

 opponens pollicis, and occasionally a tendinous slip of insertion of the abductor pollicis longus. 

 The dorsal and lateral surfaces are rough for ligaments. The medial surface is divided into 

 two parts by a horizontal ridge. The upper and larger portion is concave and articulates with 

 the lesser multangular; the lower — a small flat facet on the projecting lower angle — articulates 

 with the base of the second metarcarpal. 



Articulations. — With the navicular above, first metacarpal below, the lesser multangular 

 and second metacarpal on the medial side. 



The Lesser Multangular 



The lesser multangular [os multangulum minus] or trapezoid (fig. 195), the 

 smallest of the bones in the distal row, is somewhat wedge-shaped, with the 

 broader end dorsally and the narrow end ventrally. 



¥iG. 195. — The Left Lesser Multangular. 



Volar surface. 

 For greater multangular 

 For second metacarpal 



The superior surface is marked by a small, quadrilateral, concave facet, for the media 

 of the two facets on the lower surface; of the navicular. Tin; inferior surface is convex from side 

 to aide and concave from before backward, forming a saddle-shaped articular surface for the 

 base of the second metacarpal. ( )f the volar and dorsal surfaces, the former is narrow and rough, 



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