PRACTICAL CONSIDERATIONS : THE FOOT BONES. 437 



prevent fracture. The bones of the posterior pillar are broken in both ways. In 

 falls the astragalus is apt to break about its neck, — the weakest portion ; or if the 

 foot is strongly dorsiflexed, the anterior articular edge of the tibia may act as a 

 wedge and split it across. The os calcis may be broken between the astragalus and 

 the ground, — compression fracture ; or it may be broken behind the insertion of the 

 inferior calcaneo-scaphoid ligament, the anterior arch being flattened by the fall, but 

 the ligament resisting rupture. A few cases of fracture of the sustentaculum tali have 

 been reported, the foot having been in forcible inversion, the lesser process (susten- 

 taculum) being broken off against the edge of the astragalus. In each case this was 

 followed by eversion and sinking of the inner border of the foot (valgus), the support 

 given by the internal articulating surface to the astragalus having been removed. 



Of the metatarsal bones, the first, although the strongest, is most frequently broken 

 because it carries so large a proportion of the body weight and because it receives an 

 undue share of the violence in falls associated with eversion of the foot. The fifth 

 comes next in frequency because of its exposed position on the outer side of the foot 

 and the added violence in cases of inversion. 



Dislocation of separate bones, especially of the astragalus, is rare. It is always 

 the result of the application of considerable crushing force, is usually associated with 

 other injuries, and is influenced but little by anatomical factors. 



Disease of the bones of the foot, and especially tuberculous disease of the tarsus, 

 is common because of : (i) the frequency of traumatism ; (2) the exposure to cold 

 and damp and the scanty protection afforded by the superjacent tissues; (3) the 

 remoteness from the centre of circulation and the dependent position of the part, 

 both favoring congestions ; (4) the preponderance of cancellous tissue in the bones ; 

 and (5) the difficulty in securing perfect rest, especially after minor injuries, which 

 are those most often followed by tuberculous osteitis. It affects most frequently those 

 bones that bear most of the weight of the body, — the os calcis, the head of the 

 astragalus, and the base of the first metatarsal. It is more likely to remain localized 

 when situated in the os calcis or in the hinder part of the astragalus ; in the anterior 

 portions of the tarsus the number and complexity of the synovial cavities (often 

 intercommunicating) tend to prolong and to spread the disease. In disease of the 

 tarsal bones — excepting the astragalus, to which no muscle is attached — the tendon 

 sheaths in the vicinity may be involved by direct extension from the periosteum. 



Any metatarsal bone may be involved in cases of ' ' perforating ulcer, ' ' the situa- 

 tion of the latter being determined usually by the degree of pressure upon the sole in 

 cases in which anaesthesia is already present ; hence the frequency with which the first 

 metatarsal is involved in this disease. 



Excisioji of the separate bones has frequently been performed, especially of the 

 astragalus and os calcis. 



Landmarks. — On the inner side of the foot can be felt : (a) the ridge between 

 the inner and posterior surfaces of the os calcis ; (<5) the tubercle of the os calcis ; (r) 

 the sustentaculum tali, one inch directly below the tip of the malleolus ; (^) from one- 

 half to three-quarters of an inch in front of the latter the head of the astragalus, very 

 noticeable in flat-foot ; (<?) from one-half to three-quarters of an inch more anterior 

 the prominent tuberosity of the scaphoid, the space between it and the sustentaculum 

 being filled by the inferior calcaneo-scaphoid ligament and the tibialis posticus tendon ; 

 from the tuberosity the tendon may be traced to the back of the inner malleolus ; 

 (/) the internal cuneiform ; (^) the base (one and a half inches in front of the 

 scaphoid tuberosity), the shaft, and the expanded head of the first metatarsal ; (>%) 

 the base of the first phalanx with the internal sesamoid bones just beneath ; {i) the 

 phalanges. 



On the outer side are to be felt : (a) the ridge between the outer and posterior 

 surfaces of the os calcis ; (<5) the external tubercle of the os calcis ; (^) the peroneal 

 tubercle, three-quarters of an inch below and a little in front of the tip of the external 

 malleolus, lying between the long and short peroneal tendons ; (^) the external 

 surfaces of the os calcis and (when the foot is inverted) the edge of its anterior 

 extremity, lying just above the cuboid ; («?) the prominent base of the fifth metatarsal 

 (about two and a half inches in front of the malleolus), the shaft, and the expanded 

 head of that bone ; (/") the phalanges. 



