174 



THE ARTICULATIONS OF THE UPPER LIMB. 



one at the radial, the other at the ulnar border of the carpus ; the former connects 

 the scaphoid bone with the trapezium, the latter the pyramidal with the unciform. 

 The dorsal ligaments consist of fibres passing in various directions ; the palmar 

 ligaments are chiefly composed of fibres converging towards the os magnum. 



The bones of the first row, the pisiform bone excepted, are united by inter- 

 osseous and by dorsal and palmar ligaments. The interosseous ligaments, placed on 

 the sides of the lunar bone on a level with its superior surface, connect it with the 

 scaphoid and pyramidal bones, thus completing the inferior wall of the radio-carpal 

 joint. The dorsal and pal 'mar ligaments extend transversely on the dorsal and palmar 

 surfaces from the scaphoid bone to the lunar, and from the lunar to the pyramidal. 



The bones of the second row are connected by similar means. The dorsal 

 and palmar ligaments pass transversely between the contiguous bones. The inter ' 



Fig. 201. CORONAL SECTION OP THE INFERIOR RADIO-ULNAR, 



RADIO-CARPAL, INTERCARPAL, AND CARPO-METACARPAL AR- 

 TICULATIONS. (Allen Thomson. ) \ 



1, triangular nbro-cartilage ; 2, placed on the ulna, points 

 to the synovial cavity of the inferior radio-ulnar articulation ; 

 3, external lateral, and 4, internal lateral ligament, and be- 

 tween them the synovial cavity of the wrist ; 5, scaphoid 

 bone ; 6, lunar ; 7, pyramidal ; 8, 8, upper portion, and 8 , 8', 

 lower portion of the general synovial cavity of the intercarpal 

 and carpo-metacarpal articulations ; between 5 and 6, and t> 

 and 7, the interosseous ligaments are seen separating the carpal 

 articular cavity from the wrist-joint ; between the four carpal 

 bones of the lower row, and between the magnum and scaphoid, 

 the interosseous ligaments are also shown ; the upper division 

 of the synorial cavity communicates with the lower between 

 10 and 11, and between 11 and 12; x, marks one of the 

 three interosseous metacarpal ligaments ; 9', separate synovial 

 cavity of the first carpo-metacarpal articulation ; 13, first, and 

 14, fifth metacarpal bone. 



NOTE. It is to be observed that in this figure, and in 

 others of a like kind which represent the joint-cavities, the 

 white or black lines indicating the synovial membranes are, for 



the sake of clearness, generally represented as passing over the surfaces of the articular cartilages, 

 although this is not the case in* nature. These lines therefore must be held to represent merely the 

 whole continuity of the articular or, as they are often called, the synovial surfaces. 



osseous ligaments are generally three (but sometimes only two) in number, a strong 

 ligament being placed between the os magnum and unciform bone, another between 

 the trapezoid and trapezium, and a slender ligament between the os magnum and 

 trapezoid. A small interosseous ligament is also found sometimes between the os- 

 magnum and the scaphoid (fig. 201). 



The synovial cavity of the carpal articulations is extensive and complicated. 

 Passing between the two rows of carpal bones, it sends upwards two processes 

 between the three bones of the first row, and downwards three between the four 

 bones of the second row. It is farther continued below into the inner four carpo- 

 metacarpal and three intermetacarpal articulations. In some rare cases there is- 

 continuity with the synovial cavity of the wrist-joint, by deficiency of one of the 

 interosseous ligaments between the upper carpal bones. 



The pisiform, bone is articulated with the pyramidal bone by a thin fibrous 

 capsule, lined by synovial membrane. Inferiorly, two strong bands descend from 

 it, the pisi-uncinate ligament to the hook of the unciform bone, and the pisi-meta- 

 carpal ligament to the base of the fifth metacarpal, and sometimes also to other 

 metacarpal bones ; superiorly it receives the tendon of the flexor carpi ulnaris 

 muscle. The synovial cavity is usually distinct, but it sometimes communicates with 

 that of the radio-carpal articulation. 



The anterior annular ligament of the wrist is a strong and thick band, 



