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ARTICULATION OF THE WRIST. 



The orbicular ligament is a firm band 

 Fig. 57.* several lines in breadth, which surrounds 

 the head of the radius, and is attached by 

 each end to the extremities of the lesser sig- 

 moid cavity. It is strongest behind where it 

 receives the external lateral ligament. On its 

 inner surface it is lined by a process of syno- 

 vial membrane from the elbow joint. When 

 this ligament is ruptured, as often occurs in 

 children, the head of the radius readily slips 

 from its place. 



There are also some ligamentous bands, 

 which run upon the front and back parts of 

 the joint to strengthen it, which are called 

 Anterior and Posterior accessory ligaments. 

 They are broad thin membranous layers 

 placed on the outer surface of the synovial 

 membrane, and are both attached to the hume- 

 rus above, and upon the sides to the lateral 

 ligaments : below the posterior is attached to 

 the olecranon ; the anterior to the coronoid process of the 

 ulna and to the lateral ligament. Within the synovial mem- 

 brane, in the upper margins of the depressions for the olecranon 

 and coronoid processes of the ulna, are the adipose substances 

 usually found in joints. 



Articulation of the Wrist. 



The structure of the wrist is particularly complex, because it consists of three 

 articulations, which are contiguous to each other, viz. That of the ulna and 

 radius; of the radius and first row of carpal bones, radio-carpal; and of the 

 first and second row of carpal bones with each other, middle carpal joint. 



An oblong convex head is formed by the upper surfaces of 

 the scaphoides and lunare, and a portion of the upper surface 



* External view of the elbow joint. 1. Humerus. 2. Ulna. 3. Radius. 4. 

 The external lateral ligament inserted below into the orbicular ligament. 6. 

 The posterior extremity of the orbicular or coronary ligament, spreading out at 

 its insertion into the ulna. 7. The anterior ligament, scarcely seen in this view 

 of the articulation. 8. The posterior ligament, thrown into folds by the exten- 

 sion of the joint. 





