204 



THE ARTICULATIONS. 



of tlie inter-, lateral, and inferior sesamoid middle and deep ligaments. An injection of tlie 

 eynovinl capsule brings into relief some features which are interesting, from a surgical point 

 of view. 



This is a perfect hinge-joint, formed by the inferior extremity of the median 

 metacarpal bone on the one part, and the superior extremity of the upper phalanx 

 and sesamoids on the other. 



Articular surfaces. — For the metacarpal bone, there are two lateral condyles 

 and a median antero-posterior eminence ; for the first phalanx, two glenoid 

 cavities and an intermediate groove prolonged posteriorly on the anterior face of 

 the two sesamoids. Divided in this manner into three portions, the digital 

 surface is well constituted for solidity, because the pressure transmitted to this 



region is diminished and 



Fig. 131. 



DETAILS OF THE METACARPO-PHAI.ANGICAL ARTICULATION OF 

 THE HORSK. 



diffused by the natural 

 elasticity of the bands 

 which unite these three 

 pieces to each other. 



Mode, of union. — The 

 means of union may be 

 divided into two cate- 

 gories : 1. Those which 

 join together the several 

 bones of the inferior sur- 

 face. 2. Those which 

 maintain in contact the 

 two opposed articular 

 surfaces. 



A. The firet have re- 

 ceived the generic name 

 of sesamoid ligaments, 

 and are six in number : 

 an intersesamoid ligament, 

 which holds together the 

 -two complementary bones 

 of the digital surface ; 

 three inferior and tu'o 

 lateral sesamoid ligaments, 

 Avhich unite these bones 

 to the first phalanx. 

 a. The intersesamoid ligament is composed of fibro-cartilaginous substance, 

 that appears to be the matrix in which the two sesamoids were developed ; as it 

 is spread around these bones, after being sohdly fixed on their internal face. 

 Behind, this ligament, in common with the posterior face of the sesamoids, forms 

 the channel (Fig. 131, .'')) in which tlie flexor tendons glide. In front, it occupies 

 the bottom of the intersesamoid articular groove. 



h. The inferior sesamoid ligaments, situated at the posterior face of the first 

 phalanx, are distinguished as superficial, middle, and deep. 



The superficial ligammt (Figs. 131, 14 ; 134, 8), the longest of the three, is a 

 narrow band flattened before and behind. It arises from the middle of the 

 fibro-cartilaginous mass which completes, posteriorly, the superior articular surface 

 of the second phalanx, and, shghtly widening, ascends to the base of the sesamoids, 



. Middle inferior sesamoidean 

 ligaments. P First phalanx 

 (posterior face). 1, Inter 

 sesamoidean ligament (pos- 

 terior fnce) ; 2, 2, lateral 

 sesamoidean ligaments ; 3, 

 middle inferior sesamoidean 

 ligament. 



B. Deep inferior sesamoidean 

 ligaments, p. First phalanx : 

 1, Inter-sesamoidean liga- 

 ment; 2, 2, lateral sesa- 

 moidean ligaments; 3, in- 

 ferior deep sesamoidean liga- 

 ment. 



