344 THE INFERIOR EXTREMITY 



the fibula, and in most cases is continuous with the extensor 

 digitorum longus. The anterior tibial vessels and the deep 

 peroneal nerve (O.T. anterior tibial] proceed distally in this 

 compartment. At first they are deeply placed, but as they 

 approach the ankle they come nearer to the surface. 



Dissection. To expose the anterior tibial vessels and the 

 deep peroneal nerve in their entire course on the front of the 

 leg, the tibialis anterior and the extensor digitorum longus must 

 be separated from each other, along the line of a strong inter- 

 muscular septum which dips backwards between them, and 

 affords a surface of origin to each. The knife should be carried 

 proximally along the plane of this septum. If the peronaeus 

 tertius muscle is drawn aside, the perforating branch of the 

 peroneal artery will be seen piercing the interosseous membrane. 

 It is a small artery which descends upon the distal end of the 

 fibula. As the structures in the anterior crural compartment 

 are being exposed and cleaned, the dissector should, at the same 

 time, carry on the dissection of the dorsum of the foot. There 

 the tendons of the mus 3les on the front of the leg must be followed 

 to their insertions, then the tendons of the extensor digitorum 

 longus must bfi pulled aside in order that the extensor hallucis 

 brevis and the extensor digitorum brevis, which lie deep to the 

 tendons of the long extensor of the toes, may be cleaned and 

 their tendons followed to their terminations. The dorsalis 

 pedis artery, which is the continuation of the anterior tibial 

 artery, and the deep peroneal nerve, and their branches, must 

 also be cleaned and followed to their terminations. 



M. Tibialis Anterior (O.T. Tibialis Anticus). The tibialis 

 anterior is a powerful muscle, which takes origin from the 

 distal part of the lateral condyle of the tibia, and from the 

 proximal half of the lateral surface of its body (Fig. 154, p. 343). 

 It derives many fibres also from the deep fascia which covers 

 it, from the fascial septum between it and the extensor digi- 

 torum longus, and from the portion of the interosseous 

 membrane on which it rests. In other words, it springs from 

 the structures which form the walls of the medial portion of 

 the osteo-fascial compartment in which it lies. 1 A strong 

 tendon issues from its fleshy belly in the distal third of the 

 leg, and this reaches the dorsum of the foot by passing 



1 To understand the attachments of the muscles of the leg, it is necessary 

 to bear in mind that the interosseous membrane, which stretches across the 

 interval between the two bones of the leg, and thus extends the surface of 

 origin for these muscles, is attached to the interosseous crest of the tibia (i.e. 

 between its lateral and posterior surfaces) and to the interosseous crest of the 

 fibula. The interosseous crest of the fibula traverses the medial surface of 

 that bone, and divides it into an anterior and a posterior part. The anterior 

 part gives origin to the extensor muscles and the posterior part to the tibialis 

 posterior. 



