Chap, xxiii.] THE ANKLE AND FOOT. 519 



upper surface of the astragalus from that of the 

 tibia, but rather is one or other edge of the former 

 bone brought in contact with the horizontal articular 

 surface of the latter. Although much deformity is 

 produced, the actual separation of the foot from the 

 leg is not considerable. In some rare cases a true 

 lateral dislocation in the horizontal direction has been 

 met with. 



These injuries are due to sudden and violent 

 twistings of the foot, and are in nearly every instance 

 associated with fractures of the tibia or fibula. The 

 luxation outwards is due to forcible eversion of the 

 foot, the luxation inwards to violent inversion. 



It is of interest, in the first place, to note the re- 

 lation of the Jibula to injuries at the ankle-joint, 

 especially as a fracture of the lower end of the 

 shaft of that bone may follow alike upon both 

 inversion and eversion of the foot The lower three 

 or four inches of the fibula may be considered to 

 form a lever of the first kind (Fig. 54, A). The fulcrum 

 is at the inferior tibio-fibular articulation, one arm of 

 the lever is the malleolus below that joint, while the 

 other arm may be regarded as formed by the lower 

 two or three inches of the shaft of the bone, Now 

 the lower ends of the tibia and fibula are bound 

 together by very powerful ligaments, viz., the anterior 

 and posterior tibio-fibular, the transverse, and the 

 inferior interosseous. I would venture to parti- 

 cularly insist that in no ordinary lesion about the 

 ankle, whether fracture or dislocation, do these liga- 

 ments give way. If they should yield, then an 

 anomalous form of fracture or luxation will be pro- 

 duced. In forcible eversion of the foot, the internal 

 lateral ligament becomes stretched and tears, the 

 astragalus is rotated laterally beneath the tibio- 

 fibular arch and is brought into violent contact with 

 the end, qf the qu^er malleolus. This process is 



