THE UPPER LIMB 



403 



Radius 



Uloa 



The internal lateral ligament is a strong, round cord, which 

 extends from the tip of the styloid process of the uhia to the cunei- 

 form and pisiform bones. 



The synovial membrane lines the internal surface of the capside 

 and the upper surfaces of the interosseous hgaments on either side 

 of the semilunar. In cases where the triangular libro-cartilage is 

 perforated it is continuous with the sjTiovial membrane of the in- 

 ferior radio-ulnar joint, 

 but it is distinct from 

 that of the carpal articu- 

 lations. 



Muscular Relations 

 — A nterior. — From with- 

 in outwards, the flexor 

 carpi ulnaris, flexor pro- 

 fundus digitorum, flexor 

 longus pollicis, and flexor 

 carpi radialis. Posterior. 

 — From within outwards, 

 the extensor carpi ulnaris, 

 extensor minimi digiti, 

 extensor communis digi- 

 tormn with the extensor 

 indicis, extensor longus 

 pollicis, extensor carpi 

 radialis brevior, and ex- 

 tensor carpi radialis 

 longior. External. — The 

 extensor ossis metacarpi 

 pollicis and extensor 

 brevis pollicis. 



Arterial Supply. — The anterior and posterior carpal retia. 



Nerve-supply. — The median, ulnar, and posterior interosseous, 

 nerves. 



Movements. — Six movements are allowed, namely, palmar flexion, dorsal 

 flexion, ulnar flexion or adduction, radial flexion or abduction, extension, and 

 circumduction. In all forms of flexion an angle is produced between the 

 hand and forearm. Extension is straightening, so as to efface the angle 

 produced by flexion. Clrcumdactlon is a combination of all the foregoing 

 movements occurring in alternate succession. Adduction is more extensive 

 than abduction, the stj'loid process of the radius limiting the latter move- 

 ment. When the hand is in line with the forearm, the scaphoid division 

 of the carpal articular surface of the radius articulates with the scaphoid bone, 

 and the semilunar di\'ision of the carpal articular surface of the radius, together 

 with the triangular fibro-cartilage, articulates with the semilunar bone, the 

 fleeted part of the upper surface of the cuneiform being in contact with the 

 ; mer portion of the capsule. When, however, the hand is adducted — that is 



>_ say, flexed in an inward direction — the faceted part of the upper surface 

 of the cuneiform articulates with the triangular fibro-cartilage, the semilunar 

 bone partially articulates with the scaphoid surface of the radius, and the 

 scaphoid bone partially articulates with the outer portion of the capsule. 



^»«i^ 



^ J" 



FlG. 



217A. — Radio-carpal and Carpal 

 Synovial Membranes. 



i 



