

THE META( 



227 





surface articulates with the hamate by a smooth, concave, oblong facet, which 

 occupies its posterior and superior parts; it is rough in front, for the attachment 

 of an interosseous ligament. 



Articulations. The capitate articulates with seven bones : the navicular and lunate proximally, 

 the second, third, and fourth metacarpals distally, the lesser multangular on the radial side, and 

 the hamate on the ulnar side. 



The Hamate Bone (os hamatum; unciform bone) (Fig. 228). The hamate bone 

 may be readily distinguished by its wedge-shaped form, and the hook-like process 

 which projects from its volar surface. It is situated at the medial and lower angle 

 of the carpus, with its base downward, resting on the fourth and fifth metacarpal 

 bones, and its apex directed upward and laterahvard. The superior surface, the 

 apex of the wedge, is narrow, convex, smooth, and articulates with the lunate. 

 The inferior surface articulates with the fourth and fifth metacarpal bones, by 

 concave facets which are separated by a ridge. The dorsal surface is triangular 

 and rough for ligamentous attachment. The volar surface presents, at its lower 

 and ulnaf side, a curved, hook-like process, the hamulus, directed forward and 

 laterahvard. This process gives attachment, by its apex, to the transverse carpal 

 ligament and the Flexor carpi ulnaris; by its medial surface to the Flexor brevis 

 and Opponens digiti quinti; its lateral side is grooved for the passage of the Flexor 

 tendons into the palm of the hand. It is one of the four eminences on the front 

 of the carpus to which the transverse carpal ligament of the wrist is attached; 

 the others being the pisiform medially, the oblique ridge of the greater multangular 

 a ad the tubercle of the navicular laterally. The medial surface articulates with 

 the triangular bone by an oblong facet, cut obliquely from above, downward 

 and medial ward. The lateral surface articulates with the capitate by its upper 

 and posterior part, the remaining portion being rough, for the attachment of 

 ligaments. 



Articulations. The hamate articulates with five bones: the lunate proximally, the fourth 

 i ad fifth metacarpals distally, the triangular medially, the capitate laterally. 



The Metacarpus. 



The metacarpus consists of five cylindrical bones which are numbered from the 

 iteral side (ossa metacarpalia I-V) ; each consists of a body and tw T o extremities. 



Common Characteristics of the Metacarpal Bones. The Body (corpus; shaft). 

 '.Tie body is prismoid in form, and curved, so as to be convex in the longitudinal 

 irection behind, concave in front. It presents three surfaces: medial, lateral, 

 nd dorsal. The medial and lateral surfaces are concave, for the attachment of 

 he Interossei, and separated from one another by a prominent anterior ridge. 

 ?he dorsal surface presents in its distal two-thirds a smooth, triangular, flattened 

 Tea which is covered in the fresh state, by the tendons of the Extensor muscles. 

 This surface is bounded by two lines, which commence in small tubercles situated 

 n either side of the digital extremity, and, passing upward, converge and meet 

 ome distance above the center of the bone and form a ridge which runs along the 

 :st of the dorsal surface to the carpal extremity. This ridge separates two 

 .oping surfaces for the attachment of the Interossei dorsales. To the tubercles 

 in the digital extremities are attached the collateral ligaments of the metacarpo- 

 )halangeal joints. 



The Base or Carpal Extremity (basis) is of a cuboidal form, and broader behind 

 an in front: it articulates with the carpus, and with the adjoining metacarpal 

 >ones; its dorsal and volar surfaces are rough, for the attachment of ligaments. 



The Head or Digital Extremity (capitulum) presents an oblong surface markedly 

 convex from before backward, less so transversely, and flattened from side to side; 

 it articulates with the proximal phalanx. It is broader, and extends farther up- 



