450 HUMAN ANATOMY. 



first cuneiform and the joint behind and before it, the first metatarsal and perhaps 

 the inner sesamoid come in order. A very moderate swelHng obscures most of these 

 points. On the outer side the joint between the calcaneum and the cuboid can be 

 found. A httle in front of this is the tuberosity of the fifth metatarsal, the only dis- 

 tinct landmark on the outer side. The general dorsal outline of the tarsal bones is 

 to be recognized, but only under favorable circumstances. The dorsal surfaces of 

 the metatarsals are distinct.' The joint between the astragalus and calcaneum behind 

 and the scaphoid and cuboid in front is sinuous : convex forward at the inner part 

 and tending to concavity at the outer, the two ends of the line being nearly in the 

 same transverse plane. The tarso- metatarsal joint is very oblique, running from 

 within outward and backward. It is repeatedly irregular, the chief interruption of 

 the direction being at the mortise of the second metatarsal between the inner and 

 outer cuneiforms. The joints of the first phalanges with the metatarsal bones are 

 about 2.5 centimetres behind the web of the toes. 



PRACTICAL CONSIDERATIONS. 



The Ankle-joint. — Uncomplicated dislocations, inward or outward, are almost 

 unknown because of (a) the close lateral approximation of the malleoli, which are held 

 to the sides of the astragalus by the strong inferior tibio-fibular ligaments ; {b) the 

 further support of the lateral ligaments, especially the inner ; and, (r) to a very 

 minor extent, the wavy outline of the upper surface of the astragalus, which slightly 

 resists sidewise movements. 



Lateral dislocations are accordingly almost always associated with fracture of 

 one or other of the bones of the leg, and have been sufificiently described in that 

 connection (page 395). They are incomplete. In addition to the inward or out- 

 ward movement of the astragalus it undergoes a partial rotation on an antero-posterior 

 axis, so that its tibial surface points obhquely upward in a direction opposite to that 

 of the displacement. 



Reduction is easy and the after-treatment is that appropriate to the fracture. 



Backward dix'AoQ.dXxon's, of the astragalus — i.e., of the foot (which are etiologically 

 forward dislocations of the tibia) — are resisted by (a) the shape of the upper articular 

 surface of the astragalus, which is about one-fourth narrower behind than in front ; 

 ((5) the corresponding shape of the irregular arch in which the astragalus rests ; (f) 

 the outward slope from behind forward of the lateral facets of the astragalus ; (^d) the 

 lower level of the posterior as compared with the anterior articular edge of the tibia ; 

 and (<?) the reinforcement of the posterior ligament by the tendon of the flexor longus 

 hallucis. If it were not for thise provisions, the frequency with which, in alighting on 

 the ground in running or jumping, the foot is fixed and the tibia is driven forward 

 against the weak anterior ligament would render these luxations much more common. 

 An even more powerful leverage is produced in the same direction when, the foot 

 being fixed, a fall backward thrusts the lower end of the tibia forward. As it is, the 

 backward far exceed in frequency the forward luxations because, although the above- 

 mentioned anatomical factors favor the latter, the weight of the body is scarcely 

 ever brought upon the limb in such a direction and with such force as to induce 

 them (Humphry). 



In backward luxation the tibia rests upon the scaphoid and cuneiform, the 

 anterior ligament is ruptured, and the posterior and lateral ligaments are lacerated. 

 The foot is shortened from the lower anterior edge of the tibia to the web of the great 

 toe, the heel is lengthened, the tendo Achillis describes a marked curve backward, 

 and the depressions on either side of it are exaggerated. 



Sprains of the ankle, on account of its position, where, in lateral twists, it can 

 receive through the leverage of the whole lower extremity the weight of the entire 

 body, are more common than of any other joint. 



This force is nearly always applied through eversion or inversion (abduction or 

 adduction) of the foot, usually the former, and the injury consists in laceration of the 

 fibres of a lateral ligament with strain of some of the tendons in relation to the 

 malleoli, and bruising and pinching of loose synovial membrane. More rarely 

 extreme dorsiflexion will injure the posterior ligament and the posterior portions of 



