214 THE SKELETON. 



part of the bone, is most frequently fractured, though fractures may occur in any part and 

 almost in any direction, either associated or not with fracture of other bones. 



In cases of club-foot, especially in congenital cases, the bones of the tarsus become altered 

 in shape and size, and displaced from their proper positions. This is especially the case in con- 

 genital equino-varus, in which the astragalus, particularly about the head, becomes twisted and 

 atrophied, and a similar condition may be present in the other bones, more especially the navic- 

 ular. The tarsal bones are peculiarly liable to become the seat of tuberculous caries from com- 

 paratively trivial injuries. There are several reasons to account for this. They are composed 

 of a delicate cancellated structure, surrounded by intricate synovial membranes. They are situ- 

 ated at the farthest point from the central organ of the circulation and exposed to vicissitudes 

 of temperature ; and, moreover, on their dorsal surface are thinly clad with soft parts which 

 have but a scanty blood-supply. And finally, after slight injuries, they are not maintained in a 

 condition of rest to the same extent as similar injuries in some other parts of the body. Caries 

 of the calcaneum or astragalus may remain limited to the one bone for a long period, but when 

 one of the other bones is affected, the remainder frequently become involved, in consequence 

 of the disease spreading through the large and complicated synovial membrane which is more 

 or less common to these bones. 



Amputation of the whole or a part of the foot is frequently required either for injury or 

 disease. The principal amputations areas follow: (1) Syme's : amputation at the ankle-joint 

 by a heel-flap, with removal of the malleoli and sometimes a thin slice from the lower end of 

 the tibia. (2) Roux's: amputation at the ankle-joint by a large internal flap. (3) Pirogoff's 

 amputation : removal of the whole of the tarsal bones, except the posterior part of the os calcis 

 and a thin slice from the tibia and fibula including the two malleoli. The sawn 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. (5) Chopart's or medio-tarsal : removal of the ante- 

 rior part of the foot with all the tarsal bones except the os calcis and astragalus ; disarticula- 

 tion being effected through the joints between the astragalo-scaphoid and calcaneo-cuboid in 

 joints. (6) Lisfranc's : amputation of the anterior part of the foot through the tarso-metatarsal 

 joints. This has been 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, or, as recommended by Mr. Lund, 

 in cases of inveterate talipes. The cuboid has been removed for the same reason by Mr. Solly. 

 But both these two latter operations have fallen very much into disuse, and have been super- 

 seded by resection of a wedge-shaped piece of bone from the outer side of the tarsus. Finally, 

 Mickulicz and Watson have devised operations for the removal of more extensive portions of 

 the tarsus. Mickulicz' 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 sawn surfaces of the tibia 

 and fibula, and fixed there. The result is a position of the shortened 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 astragalus, and the cuboid and 

 os calcis, and removes the intervening bones. 



The metatarsal bones and phalanges are nearly always broken by direct violence, and in the 

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

 The metatarsal bones, and especially that of the great toe, are frequently diseased, either in 

 tubercular subjects or in perforating ulcer of the foot. 



Sesamoid Bones. 



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 

 the parts over which they glide. It is said that they are more commonly found in 

 the male than in the female, and in persons of an active muscular habit than in 

 those who are weak and debilitated. They are invested throughout their whole 

 surface by the fibrous tissue of the tendon in which they are found, excepting upon 

 that side which lies in contact with the part over which they play, where they 

 present a free articular facet. They may be divided into two kinds : those which 

 glide over the articular surfaces of joints, and those which play over the cartilag- 

 inous facets found on the surfaces of certain bones. 



