5 20 



SURGICAL APPLIED ANATOMY. [Chap. xxm. 



pushed outwai'ds, 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 inches above the 



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

 of the Lower End of the Fibula. 



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

 ment ; e, internal lateral ligament ; B, fracture of fibula due to evcrsion 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 levef 



