OSTEOLOGY 



the attachment of the anterior fibers of the deltoid ligament of the ankle-joint; 

 its posterior border presents a broad groove, the malleolar sulcus, directed obliquely 

 downward and medialward, and occasionally double; this sulcus lodges the tendons 

 of the Tibialis posterior and Flexor digitorum longus. The summit of the medial 

 malleolus is marked by a rough depression behind, for the attachment of the 

 deltoid ligament. 



Structure. The structure of the tibia is like that of the other long bones. The compact wall 

 of the body is thickest at the junction of the middle and lower thirds of the bone. 



Ossification. The tibia is ossified from three centers (Figs. 260, 261): one for the body and 

 one for either extremity. Ossification begins in the center of the body, about the seventh week 

 of fetal life, and gradually extends toward the extremities. The center for the upper epiphysis 

 appears before or shortly after birth; it is flattened in form, and has a thin tongue-shaped process 

 in front, which forms the tuberosity (Fig. 260) ; that for the lower epiphysis appears in the second 

 year. The lower epiphysis joins the body at about the eighteenth, and the upper one joins about 

 the twentieth year. Two additional centers occasionally exist, one for the tongue-shaped process 

 of the upper epiphysis, which forms the tuberosity, and one for the medial malleolus. 



The Fibula (Calf Bone). 



The fibula (Figs. 258, 259) is placed on the lateral side of the tibia, with which 

 it is connected above and below. It is the smaller of the two bones, and, in 

 proportion to its length, the most slender of all the long bones. Its upper 

 extremity is small, placed toward the back of the head of the tibia, below the level 

 of the knee-joint, and excluded from the formation of this joint. Its lower extremity 

 inclines a little forward, so as to be on a plane anterior to that of the upper end; 

 it projects below the tibia, and forms the lateral part of the ankle-joint. The 

 bone has a body and two extremities. 



The Upper Extremity or Head (capitulum fibulae; proximal extremity}. The 

 upper extremity is of an irregular quadrate form, presenting above a flattened 

 articular surface, directed upward, forward, and medialward, for articulation with 

 a corresponding surface on the lateral condyle of the tibia. On the lateral side 

 is a thick and rough prominence continued behind into a pointed eminence, the 

 apex (styloid process}, which projects upward from the posterior part of the head. 

 The prominence, at its upper and lateral part, gives attachment to the tendon of 

 the Biceps femoris and to the fibular collateral ligament of the knee-joint, the liga- 

 ment dividing the tendon into two parts. The remaining part of the circumference 

 of the head is rough, for the attachment of muscles and ligaments. It presents in 

 front a tubercle for the origin of the upper and anterior fibers of the Peronseus 

 longus, and a surface for the attachment of the anterior ligament of the head; 

 and behind, another tubercle, for the attachment of the posterior ligament of the 

 head and the origin of the upper fibers of the Soleus. 



The Body or Shaft (corpus fibulae). The body presents four borders the 

 antero-lateral, the antero-medial, the postero-lateral, and the postero-medial ; and 

 four surfaces anterior, posterior, medial, and lateral. 



Borders. The antero-lateral border begins above in front of the head, runs ver- 

 tically downward to a little below the middle of the bone, and then curving some- 

 what lateralward, bifurcates so as to embrace a triangular subcutaneous surface 

 immediately above the lateral malleolus. This border gives attachment to an 

 intermuscular septum, which separates the Extensor muscles on the anterior 

 surface of the leg from the Peronsei longus and brevis on the lateral surface. 



The antero-medial border, or interosseous crest, is situated close to the medial 

 side of the preceding, and runs nearly parallel with it in the upper third of its 

 extent, but diverges from it in the lower two-thirds. It begins above just beneath 

 the head of the bone (sometimes it is quite indistinct for about 2.5 cm. below the 

 head), and ends at the apex of a rough triangular surface immediately above the 



