FIBULA. 



123 



Fig. 60.' 



downwards beyond the articular surface of the tibia, forming the externa* 

 malleolus. Its external side presents a rough and triangular surface, which 

 is subcutaneous. Upon the internal surface is a smooth triangular facet, 

 to articulate with the astragalus ; and a rough depression, for the attach- 

 ment of the interosseous ligament. The anterior border is thin and sharp ; 

 and the posterior, broad and grooved, for the tendons of the peronei 

 muscles. 



To place the bone in its proper position, and ascertain 

 to which leg it belongs, let the inferior or flattened ex- 

 tremity be directed downwards, and the narrow border 

 of the malleolus forwards ; the triangular subcutaneous 

 surface will then point to the side corresponding with the 

 limb of which the bone should form a part. 



The shaft of the fibula is prismoid, and presents three 

 surfaces; external, internal, and posterior; and three 

 borders. The external surface is the broadest of the 

 three ; it commences upon the anterior part of the bone 

 above, and curves around it so as to terminate upon its 

 posterior side below. This surface is completely occu- 

 pied by the two peronei muscles. The internal surface 

 commences on the side of the superior articular surface, 

 and terminates below, by narrowing to a ridge, which is 

 continuous with the anterior border of the malleolus. It 

 is marked along its middle by the interosseous ridge, 

 which is lost above and below in the inner border of the 

 bone. The posterior surface is twisted like the external; 

 it commences above on the posterior side of the bone, 

 and terminates below on its internal side; at about the 

 middle of this surface is the nutritious foramen, which is 

 directed downwards. 



The internal border commences superiorly in common 

 with the interosseous ridge, and bifurcates inferiorly into 

 two lines, which bound the triangular subcutaneous surface of the external 

 malleolus. The external border begins at the base of the styloid process 

 upon the head of the fibula, and winds around the bone, following the di- 

 rection of the corresponding surface. The posterior border is sharp and 

 prominent, and is lost inferiorly in the interosseous ridge. 



Development. By three centres ; one for the shaft, and one for each 

 extremity. Ossification commences in the shaft soon after its appearance 

 in the tibia; at birth >the extremities are cartilaginous, an ossific deposit 



* The tibia and fibula of the right leg articulated and seen from behind. 1. The ar- 

 ticular depression for the external condyle of the femur. 2. The articular depression 

 for the internal condyLe ; the prominence between the two numbers is the spinous pro- 

 cess. 3. The fossa and groove for the insertion of the tendon of the semim^mbranosus 

 muscle. 4. The popliteal plane, for the support of the popliteus muscie. 0. The po- 

 pliteal line. 6. The nutritious foramen. 7. The surface of the shaft upon which the 

 flexor longus digitorum muscle rests. 8. The broad groove on the back part of the innei 

 malleolus, for the tendons of the flexor longus digitorum and tibialis posticus. 9. The 

 groove for the tendon of the flexor longus pollicis. 10. The shaft of the fibula. The 

 flexor longus pollicis muscle lies upon this surface of the bone ; its superior limit being 

 marked by the oblique line immediately above the number. 11. The styloid process on 

 the head of the fibula for the attachment of the tendon of the biceps rrusele. 12. The 

 subcutaneous surface of the lower part of the shaft of the fibula. 13. The external 

 malleolus formed by the lower extremity of the fibula. 14. The groove upon the po- 

 terior part of the external malleolus for the tendons of the peronei muscles. 



