SESAMOID BOXKX 



257 



whole of the tarsal bones, except the posterior part of the os calcis. A thin slice is sawed from 

 the tibia and fibula, including the two malleoli. The sawed surface of the os calcis is then turned 

 up and united to the similar surface of the tibia. (4) Subastragaloid amputation: removal of the 

 foot below the astragalus through the joint between it and the os calcis. This operation has been 

 modified by Hancock, who leaves the posterior third of the os calcis and turns it up against the 

 denuded surface of the astragalus. This latter operation is of doubtful utility and is rarely 

 performed, (o) Chopart's or mediotarsal: removal of the anterior part of the foot with all the 

 tarsal bones except the os calcis and astragalus; disarticulation being effected through the astrag- 

 aloscaphoid and calcaneocuboid joints. (6) Lisfranc's amputation of the anterior part of the foot 

 through the tarsometatarsal joints. This was modified by Hey, who disarticulated through 

 the joints of the four outer metatarsal bones with the tarsus, and sawed off the projecting internal 

 cuneiform; and by Skey, who sawed off the base of the second metatarsal bone and disarticulated 

 the others. 



The bones of the tarsus occasionally require removal individually. This is especially the 

 case with the astragalus and os calcis for disease limited to the one bone, or again the astragalus 

 may require excision in cases of subastragaloid dislocation. In cases of inveterate talipes the 

 head of the astragalus and greater process of the os calcis is often removed, sometimes the scaphoid 

 is also taken out. Finally, Mikulicz and Watson have devised operations for the removal of 

 more extensive portions of the tarsus. Mikulicz's operation consists in the removal of the 

 os calcis and astragalus, along with the articular surfaces of the tibia and fibula, and also of the 

 scaphoid and cuboid. The remaining portion of the tarsus is then brought into contact with 

 the sawed surfaces of the tibia and fibula, and fixed there. The result is a position of the short- 

 ened foot resembling talipes equinus. Watson's operation is adapted to those cases where the 

 disease is confined to the anterior tarsal bones. By two lateral incisions he saws through the 

 bases of the metatarsal bones in front and opens up the joints between the scaphoid and astrag- 

 alus, and the cuboid and os calcis, and removes the intervening bones. 



Fractures of the metatarsal bones and phalanges are nearly always due to direct violence, and 

 in many cases the injury is the result of severe crushing accidents, necessitating amputation. 

 The metatarsal bones, and especially the metatarsal bone of the great toe are frequently dis- 

 eased, either in tuberculous subjects or in perforating 'ulcer of the foot. 



Sesamoid Bones (Ossa Sesamoidea) (Figs. 211, 212). 



These are small rounded masses, cartilaginous in early life, osseous in the adult, 

 which are developed in those tendons which exert a great amount of pressure upon 



FIG. 211 Sesamoid bones of the hand, 

 and CharpyJ 



(Poirier 



17 



FIG. 212. Sesamoid bones of the foot. 

 (Poirier and Charpy.) 



