478 SURGICAL APPLIED ANATOMY. [Chap. xxm. 



is fractured from one to three inches above the 

 malleolus, the inferior tibio - fibular ligaments are 

 entirely lacerated, or the portion of the tibia to 

 which they are attached is torn away, and remains 

 connected with the lower fragment of the fibula. 

 The foot is dislocated horizontally outwards, and is 

 drawn upwards, the extent of the upward displace- 

 ment depending upon the height at which the fibula 

 breaks. 



In the inward luxation the external lateral liga- 

 ment is torn or the tip of the outer malleolus dragged 

 away, the deltoid ligament is intact, but the internal 

 malleolus is commonly broken by the violence with 

 which the astragalus is brought into contact with it. 

 That bone itself may be broken, and is in any case 

 rotated laterally, so that the foot is inverted, and its 

 inner border much raised. In all forms of this dis- 

 location, whether simple or complicated, the inferior 

 tibio-fibular ligament remains intact. 



2. The antero-posterior dislocations Backwards ; 

 forwards. These injuries are brought about by great 

 force applied to the foot while the leg is fixed, or 

 more commonly by sudden arrest of the foot during 

 some violent impulse given to the body, as on jumping 

 from a carriage when in motion. In the luxation 

 backwards the astragalus is displaced behind the tibia, 

 while the articular surface of the latter bone rests 

 upon the scaphoid and cuneiform bones. The anterior 

 and posterior ligaments are entirely torn, and a great 

 part also of the two lateral bands. The fibula is 

 broken some two or three inches above the malleolus, 

 and there is usually a fracture also of the inner 

 malleolus. 



The luxation forwards is of extreme rarity. In 

 the few reported cases one or both malleoli were 

 broken. 11. W. Smith believes that the dislocation is 

 never complete. 



