90 



TOPOGRAPHICAL ANATOMY OF 



The joint capsule (capsula articularis) has the customary attachment 

 to the articular margins of the two bones that enter into the forma- 

 tion of the joint. The dorsal part of the capsule is the strongest, and 

 is supported by the tendon of the common extensor muscle. On each 

 side it is connected with a collateral ligament; and behind, where it is 

 thin, the straight sesamoidean ligament, the volar ligaments, and the 

 insertion of the superficial flexor tendon afford support. 



Fourth metacarpal bone. 



M. extensor digitorum communis. 



M. extensor digiti quinti. 



-.Third metacarpal bone. 



Lis. collaterale laterale. 



M. interosseus. 



Lis. sesamoideum laterale. 



Lig. sesamoideum rectum. — 

 Lig. sesamoideum obliquum. - — 



Ligamenta volaria £_ 



M. flexor digitorum sublimis. -V. \M ^\ v 



Lig. collaterale laterale 



Lig. sesamoideum collaterale laterale. 



-Second phalanx. 



. Lig. collaterale 

 laterale. 



Third phalanx. 



Fig. 63. — The Tendons and Ligaments of the Lateral Aspect of the Digit. 



The short, but very strong, collateral ligaments (ligamentum 

 collaterale mediale : laterale) are attached to the sides of the distal 

 extremity of the first phalanx and to the adjoining parts of the 

 second phalanx. 



There are four volar ligaments (ligamenta volaria), all of which arise 

 from the posterior (volar) surface of the first phalanx, about the middle 

 of this bone and close to the attachment of the oblique sesamoidean 

 ligament. The two central ligaments join the glenoidal fibro-cartilage 

 of the second phalanx, where they blend with the straight sesamoidean 

 ligament and the insertion of the superficial flexor tendon. The most 

 medial and most lateral of the four ligaments are attached to the 

 proximal end of the second phalanx. 



