476 



SURGICAL APPLIED ANATOMY. [Chap. xxm. 



pushed outwards, and acts as one end of a lever. The 

 fulcrum is secured by the unyielding tibio-fibular 

 ligaments, and the fibula breaks at the other end of 

 the lever, a, point some two to three in.ches above the 



Fig. 54. Diagrams to illustrate the Mechanism involved in Fractures 

 of the Lower End of the Fihula. 



A, Parts in normal position; a, tibio-flbular ligaments; b, external lateral liga- 

 ment ; c, internal lateral ligament; B, fracture of fibula due to eversion of 

 foot ; c, fracture of fibula due to inversion of foot. 



end of the bone (Fig. 54, B). In forcible inversion of 

 the foot, the astragalus undergoes a little lateral rota- 

 tion in the opposite direction ; the external lateral 

 ligament is greatly stretched, and tends to drag the 

 end of the outer malleolus inwards. If the liga- 

 ment yields, the case will probably end as a sprained 

 ankle, or pass on to a dislocation inwards of the foot. 

 But, if it remains firm, the end of the fibular lever 



