124 



CARPAL ARTICULATIONS. 



Fig. 56.* 



membrane, which forms a duplicature between the radius and ulna, 

 and is called the membrana sacciformis. By its lower surface it 

 enters into the articulation of the wrist-joint. 



Actions. The movements taking place between the radius and 

 the ulna, are the rotation of the former upon the latter ; rotation 

 forwards being termed pronation, and rotation backwards supina- 

 tion. In these movements the head of the radius turns upon its 

 own axis, within the orbicular ligament and the lesser sigmoid 

 notch of the ulna ; while inferiorly the radius presents a con- 

 cavity which moves upon the rounded head of the ulna. The 



movements of the radius are chiefly 

 limited by the anterior and posterior in- 

 ferior ligaments, hence these are not un- 

 frequently ruptured in great muscular 

 efforts. 



7. Wrist Joint. The wrist is a gingly- 

 moid articulation; the articular surfaces 

 entering into its formation being the ra- 

 dius and under surface of the triangular 

 fibro-cartilage above, and the rounded 

 surfaces of the scaphoid, semilunar, and 

 cuneiform bone below ; its ligaments are 

 four in number, 



Anterior, 

 Posterior, 

 Internal lateral, 

 External lateral. 



The anterior ligament is a broad and 

 membranous layer consisting of three fas- 

 ciculi, which pass between the lower part 

 of the radius, and the scaphoid, semilu- 

 nar, and cuneiform bones. 



The posterior ligament, also thin and 



loose, passes between the posterior surface of the radius, and the 

 posterior surface of the semilunar and cuneiform bones. 



* The ligaments of the anterior aspect of the wrist and hand. 1. The lower part 

 of the interosseous membrane. 2. The anterior inferior radio-ulnar ligament. 3. The 

 anterior ligament of the wrist joint. 4. Its external lateral ligament. 5. Its internal 

 lateral ligament. 6. The palmar ligaments of the carpus. 7. The pisiform bone, 

 with its ligaments. 8. The ligaments connecting the second range of carpal bones 

 with the metacarpal, and the metacarpal witli each other. 9. The capsular ligament 

 of the carpo-metacarpal articulation of the thumb. 10. Anterior ligament of the meta- 

 carpo-phalangeal articulation of the thumb. 11. One of the lateral ligaments of that 

 articulation. 12. Anterior ligament of the metacarpo-phalangeal articulation of the 

 index finger; these ligaments have been removed in the other fingers. 13. Lateral 

 ligaments of the same articulation; the corresponding ligaments are 'seen in the 

 other articulations. 14. Transverse ligament connecting the heads of the metacarpal 

 bones of the index and middle fingers ; the same ligament is seen between the other 

 fingers.* 15. Anterior and one lateral ligament of the phalangeal articulation of the 

 thumb. 16. Anterior and lateral ligaments of the phalangeal articulations of the 

 index finger ; the anterior ligaments are removed in the other fingers. 



