256 SPECIAL ANATOMY OF THE SKELETON 



of the first phalanx of the great toe. Immediately beneath the base of this phalanx, the internal 

 sesamoid bone is to be felt. Lastly, the expanded ends of the bones forming the last joint of 

 the great toe are to be felt. On the outer side of the foot the most posterior bony point is the 

 external tubercle of the os calcis, with the ridge separating the posterior from the outer surface 

 of the bone. In front of this the greater part of the external surface of the os calcis is subcu- 

 taneous; on it, below and in front of the external malleolus, may be felt the peroneal spine when 

 this is present. Farther forward, the base of the fifth metatarsal bone forms a prominent and 

 well-defined landmark, and in front of this the shaft of the bone, with its expanded head, and 

 the base of the first phalanx may be defined. The sole of the foot is almost entirely covered 

 by soft parts, so that but few bony parts are to be made out, and these somewhat obscurely. 

 The hinder part of the under surface of the os calcis and the heads of the metatarsal bones, 

 with the exception of the first, which is concealed by the sesamoid bones, may be recognized. 



Applied Anatomy. Considering the injuries to which the foot is subjected, it is surpris- 

 ing how seldom the tarsal bones are fractured. This is no doubt due to the fact that the tarsus 

 is composed of a number of bones, articulated by a considerable extent of surface and joined 

 together by very strong ligaments, which serve to mitigate the intensity of violence applied to this 

 part of the body. When fracture does occur, these bones, being composed for the most part 

 of a soft cancellous structure, covered only by a thin shell of compact tissue, are often extensively 

 comminuted, especially as most of the fractures are produced by direct violence. As the bones 

 have only a very scanty amount of soft parts over them, fractures are very often compound, and 

 amputation is frequently necessary. 



FIFTH 

 MCTATARSAL 



EXTERNAL 

 CUNEIFORM 



FIRST 

 METATARSAL 



FIG. 209. Line of Chopart's amputation. FIG. 210. Line of Lisfranc's amputation. 



(Poirier.) (Poirier.) 



When fracture occurs in the anterior group of tarsal bones, it is almost invariably the result 

 of direct violence; but fractures of the posterior group, that is, of the calcaneum and astragalus, 

 are most frequently produced by falls from a height on to the feet; though fracture of the os 

 calcis may be caused by direct violence or by muscular action. The posterior part of the bone, 

 that is, the part behind the articular surfaces, is almost always the seat of the fracture, though 

 some few cases of fracture of the sustentaculum tali and of vertical fracture between the two 

 articulating facets have been recorded. The neck of the astragalus, being the weakest 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 

 congenital equinovarus, 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 

 scaphoid. The tarsal bones are peculiarly liable to become the seat of tuberculous caries, and this 

 condition may arise after comparatively 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 situated 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 structures suffering from 

 similar injuries in some other parts of the body. Caries of the calcaneus 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 are as follows: (1) Syme's amputation at the ankle-joint by a heel- 

 flap, with the removal of the malleoli and 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 



