252 



OSTEOLOGY. 



APEX CAPITULI 

 FACET FOR TIBIA. 

 HEAD- 



NECK. 



INTEROSSEOUS CREST 



NUTRIENT FORAMEN 



(in this case directed 



proximal ly) 



INTEROSSEOUS 

 CREST" 



ROUGH SURFACE 

 FOR INTER- 

 OSSEOUS" 



LIGAMENT 



FACET FOR TALUS 



LATERAL 

 MALLEOLUS 



FIG. 252. RIGHT FIBULA AS 

 SEEN FROM THE MEDIAL SIDE. 



The anterior part of the medial 

 surface is coloured ]olue ; the 

 posterior part of the medial 

 surface is coloured red. 



anterior crest. If the bone is held in the position which 

 it normally occupies in the leg, it will be noticed that 

 the lateral surface of the distal extremity is limited in 

 front and behind by two lines, which converge 

 and enclose between them a triangular subcutaneous area 

 which lies immediately proximal to the lateral malleolus. 

 From the summit of the triangle so formed a well- 

 defined ridge may be traced along the front of the body to 

 reach the anterior aspect of the head. This is the anterior 

 crest. 



The interosseous crest, so named because the inter- 

 osseous membrane is -attached to it, is the ridge which 

 lies just medial to the anterior crest, or towards the 

 tibial side on the anterior aspect of the bone. It is not 

 so prominent as the anterior crest, and it extends from 

 the neck of the bone to the apex of a rough triangular 

 impression that lies proximal to the articular surface 

 on the medial aspect of the distal end. The interval 

 between the anterior and interosseous crests is the 

 anterior part of the medial surface. This interval is, as 

 a rule, of considerable width in the distal half of the 

 bone, but the two crests tend to run much closer 

 together proximally; indeed, it is not uncommon to 

 find that they coalesce to form a single crest. 



The posterior part of the medial surface is the 

 elongated area behind the proximal three-fourths or 

 four-fifths of the interosseous crest. It is limited 

 posteriorly by the medial crest, a sharp, salient ridge, 

 which commences at the medial margin of the posterior 

 aspect of the head, but does not reach the distal end of 

 the bone ; for the distal end of the medial crest curves 

 forwards and joins the interosseous crest about three or 

 four inches from the distal extremity of the body ; 

 therefore, the posterior part of the medial surface is not 

 represented in the distal part of the body. On the 

 proximal third of this surface there is frequently found 

 an oblique ridge which begins near the interosseous 

 crest at the level of the neck and extends distally and 

 backwards to join the medial crest. When the proximal 

 part of the medial crest is indistinct this ridge may be 

 mistaken for it. 



The lateral surface, which is separated from the 

 medial surface by the anterior crest, is often hollowed 

 out in its middle part, and it is twisted, so that its 

 proximal part is directed somewhat forwards, while its 

 distal part turns backwards and becomes continuous 

 distally with the broad, shallow groove which occupies 

 the posterior surface of the lateral malleolus. The 

 lateral surface is limited posteriorly and separated from 

 the posterior surface of the body by the lateral crest, 

 which is usually sharp and well defined except at its 

 extremities, where it tends to become smooth and 

 rounded. Its proximal end joins the head distal to and 

 in front of the apex capituli, and terminates distally at 

 a point just proximal to the pit on the medial surface 

 of the distal extremity. In its proximal third or 

 fourth the lateral crest is often rough where fibres oi 

 the soleus muscle arise from it. 



The posterior surface forms the remainder of the 



