170 anatomy in a nutshell. 



The Fibula. 



The word fibula means clasp or pin. It is also called the peroneal bone, 

 and Lies almost parallel with the tibia. It is not quite as long as the tibia, but 

 extends to a Lower Level. Its main purpose is to give elasticity to the leg. 



1 1- upper expanded portion is called the head, which is prolonged upward 

 at its posterior part into the styloid process. The inner surface of the head 

 and styloid process has a facet which looks upward, inward, and forward to 

 articulate with the tibia. This styloid processgives attachment to the Biceps. 

 The Soleus muscle is attached behind and the Peroneus longus is attached in 

 front. The neck is the constricted part below the head. The lower extremity 

 extends into the external malleolus which is lower than the internal malleolus. 

 .Man i- the only animal in which this is true. It articulates with the astragalus 

 internally, and behind there is a depression for the posterior fasciculus of the 

 external lateral ligament. There is a slight groove posteriorly for the Peroneus 

 longus and brevis. This extremity is convex and subcutaneous externally. 



The shaft has four surfaces which are anterior, internal, posterior, and 

 external; and it has four borders which are antero-external, antero-in- 

 ternal, postero-external, and postero-internal. To its anterior surface 

 are attached the Extensor proprius hallucis, Extensor longus digitorum, and 

 Peroneus tertius. This surface is broad and grooved below but narrow above. 

 The internal surface is grooved for the Tibialis posticus. The posterior surface 

 has attached to its upper third the Soleus, below this the Flexor longus hallucis. 

 The nutrient canal is on this surface and is directed downward. The Peroneus 

 brevis and longus are attached to the external surface, which is directed out- 

 ward above and backward below. 



The antero-external border is between the peroneal muscles and the ex- 

 tensor muscles, and extends from the front of the head of the fibula to the ex- 

 ternal malleolus, where it divides to embrace a triangular subcutaneous sur- 

 face. The antero-internal border, called interosseous ridge, gives attachment to 

 the interosseous membrane and separates the extensor muscles in front from 

 the Tibialis posticus behind. It lies parallel with the antero-external border 

 in it- upper third. It ends below just above the articular facet. The pos- 

 tero-external border separate- the peroneal muscles from theflexor muscles. It 

 commences a1 the base of the styloid process and ends below in the posterior 

 border of the external malleolus. This is not a straight line for at first it is 

 directed outward, then backward, then inward. The postero-internal border, 

 called the oblique line, commences above the inner side of the heads and ends 

 below in the lower one-fourth of the bone where it joins the interosseous ridge, 

 or antero-internal border. 



lb > Supply. The fibula receives the nutrient artery of its shaft from 



the peroneal branch of the posterior tibial. The head is nourished by branches 

 from the inferior external articular branch of the popliteal artery, and the 

 malleolus i- supplied mainly by the peroneal and external malleolar arteries. 



Ossification. From three centers. The center for the shaft appears 

 in the eighth week of intra-uterine life. The center for the proximal extremity 



