Choparfs A inputation 



507 



Bones of foot and synovial membranes. The astragalus 



articulates with the os calcis in two places, the interosseous ligament 

 intervening between the facets. Its head fits into the fossa at the 

 back of the scaphoid. The posterior of its two calcanean facets has a 



Synovial membranes of ankle-joint and foot. (Qi'AiN.) . 



synovial membrane of its own, but the membrane which lubricates the 

 anterior lines also the upper surface of the inferior calcaneo-scaphoid 

 ligament, and follows the head of the astragalus into the astragalo- 

 scaphoid joint. 



Excision of the astragalus may be required in the case of caries, in 

 intractable dislocation of the foot, and in infantile paralysis and invete- 

 rate talipes equino-varus (Lund), with the view of keeping the sole 

 flat upon the ground. It is easily accomplished by a free incision 

 across the front of the ankle-joint, the anterior tibial vessels and 

 nerve, and as many of the neighbouring tendons as convenient, being 

 placed aside. The anterior and lateral ligaments of the ankle-joint 

 and the astragalo-scaphoid connection being severed, the bone is 

 1 dug out/ the interosseous astragalo-calcanean ligament having been 

 divided. 



Chopart s amputation. Much of the movement which apparently 

 takes place at the ankle-joint actually occurs between the astragalus 

 and scaphoid, on the inner side, and the os calcis and cuboid on the 

 outer side of the foot. These articulations constitute the transverse 

 or mid-tar sal joint ; the partial removal of the foot, known as Chopart's 

 amputation, is effected through it. In this amputation the flap is first 

 shaped out in the sole, the limits of the flap being the borders of the 

 sole laterally, and the roots of the toes in front. Thus all the soft 

 parts are raised in a thick flap to cover the naked ends of the 



