FEACTUEES OF THE TIBIA AND FIBULA. 99 



the leg occur very frequently. Both bones may be broken by 

 direct violence, when the fracture will occur in each at the same 

 level. The fracture is then usually transverse, and the amount 

 of displacement but little. 



Fracture of the tibia alone by indirect violence is rare on 

 account of the fact that the fibula is a slender light bone, and if 

 the weight of the body is thrown upon it, after a fracture of the 

 tibia, it also snaps, breaking as a rule at its weakest point, in 

 its upper fourth. 



On the other hand fracture of the fibula alone is extremely 

 common, and generally due to direct violence, the fracture taking 

 place at the spot to which the violence is applied. The fibula in 

 its natural condition, when pressed by the fingers of one hand 

 applied above and the fingers of the other hand applied below, 

 bows towards the tibia, a definite spring being experienced. In 

 order to obtain this practical demonstration of the continuity of 

 the fibula, it is necessary to remember that the fingers must 

 rest definitely upon the bone, and that the fibula is placed in a 

 position which is distinctly posterior to that which it is some- 

 times thought to occupy. When the bone is broken the spring 

 is lost. There is little if any displacement of the fragments, 

 owing to the unbroken tibia acting as a splint. There may, 

 however, be an extensive extravasation of blood, due to laceration 

 of the peroneal artery or one of its branches, which lie in close 

 apposition to the bone. 



That part of the external malleolus which lies below and 

 posterior to the facet for the astragalus is weakened by the 

 presence of the groove which lodges the middle and posterior 

 bands of the external lateral ligament of the ankle. Consequently 

 this part of the fibula may be detached by direct violence or 

 sudden twists of the foot which drag upon the ligamentous 

 fasiculi. 



Fracture of the tibia and fibula with outward partial dislocation 

 of the ankle (Pott's fracture}. In order to understand the pro- 

 duction of this lesion, which is in reality a fracture-dislocation, it 

 should be remembered that it is nearly always due to a strong 



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