The Lower Extremity and Pelvis 



169 



The centres in the tibia precede those in the fibula. 

 Tibia : Shaft, seventh week ; 



Upper end, just after birth ; 

 Lower end, second year. 

 Fibula : Shaft, eighth week ; 



Upper end, third year ; 

 Lower end, second year. 



The lower ends fuse with the shaft a few years after puberty in the tibia and 

 about twenty-one in the. fibula. The proximal end is fused before twenty-four : in 

 the tibia occasionally as early as nineteen or 

 twenty. 



The upper epiphysis in the tibia includes 

 (Fig. 131) the upper half of the tubercle : in 

 this there is occasionally an additional 

 centre, appearing about twelve or thirteen 

 and joining the epiphysis as a rule. 



THE FOOT. 



The skeleton of the foot, like that of 

 the hand, consists of a closely articulated 

 number of irregular bones, the tarsus, 

 carrying five long bones, the metatarsus, 

 which in their turn support the phalanges of 

 the free digits (Fig. 138). 



THE TARSUS This comprises seven 

 bones, of which one, the astragalus or talus, 

 articulates with the bones of the leg and 

 rests below on the os calcis or calcaneum, 

 which makes the projection of the heel. 

 The astragalus ends in front in a rounded 

 head, which, being directed somewhat in- 

 wards as well as forwards, tends to project 

 over the inner side of the front end of the 

 os calcis, and the latter bone has a 

 projection here to support it, hence termed the sustentaculum tali. 



These two bones are the largest in the tarsus and form its hinder part : their 

 anterior extremities, nearly on the same level, are joined at the mid-tarsal joint with the 

 front part of the tarsus. 



The head of the astragalus articulates with the scaphoid or navicular, and this 

 has the three cuneiform bones against its anterior surface. The cuneiforms are inner, 

 middle and outer, and support the inner three metatarsals. 



The anterior end of the calcaneum has the cuboid articulating with it, and this 

 carries on its front aspect the two outer metatarsals. 



We see, then, that the astragalus is continuous with the chain of bones on the inner 

 side of the foot, scaphoid, cuneiforms and metatarsals, while the os calcis, cuboid, and 

 outer two metatarsals form a chain of bones that lies outside and rather below the 

 others. 



FIG. 138. Semidiagrammatic dorsal view of 

 right foot bones. 



