4#2 SURGICAL APPLIED ANATOMY. [Chap. xxm. 



the astragalus and cuboid, or from the former bone 

 alone. 



Subastragaloid dislocations of the foot. 



In these lesions, which are not very uncommon, the 

 astragalus remains in position between the tibia and 

 fibula, while the rest of the foot is dislocated below 

 that bone. The luxation, therefore, concerns the 

 calcaneo-astragaloid and astragalo-scaphoid joints. 

 The foot may be displaced either forwards, backwards, 

 or laterally. The forward dislocation is extremely 

 rare, and the lateral luxations are nearly always 

 oblique. In the most usual displacement the foot is 

 dislocated outwards or inwards, and is at the same 

 time carried backwards. These luxations are often 

 compound, especially when lateral. They are, as a 

 rule, incomplete as regards the calcaneo-astragaloid 

 joint, while, on the other hand, the displacement of 

 the astragalus from the scaphoid is in nearly every 

 instance complete. In all cases the interosseous liga- 

 ment between the os calcis and astragalus must be 

 torn, and there will also be more or less laceration of 

 the astragalo-scaphoid ligament, and of one or both 

 of the lateral bands of the ankle joint. The malleoli 

 are very often fractured. 



It is only necessary to notice 'in any detail the two 

 lateral luxations, as being the only common forms. 

 In the inward dislocation the foot is inverted, its 

 inner border is raised, is shortened; and rendered 

 concave, while its outer border is lengthened and 

 made convex. The deformity much resembles that of 

 talipes varus. The head of the astragalus with the 

 outer malleolus form a projection at the outer aspect of 

 the foot, while below them a deep hollow exists. The 

 inner border of the os calcis is very prominent at the 

 internal side of the limb, while the inner malleolus is 

 buried in the hollow left by the displacement of that 

 bone. The calcaneum and scaphoid are approximated. 



