THE DEEP PERONEAL NERVE 1015 



lateral side, and the extensor digitorum longus on the medial side. It gives off 

 muscular and cutaneous branches in its descent, and at the junction of the middle 

 and lower thirds of the leg it pierces the deep fascia and divides into a medial 

 and a lateral branch (fig. 773). 



Muscular branches are given off from the superficial peroneal to the peroneus 

 longus and peroneus brevis before the nerve pierces the deep fascia. 



Cutaneous branches pass from the trunk of the superficial peroneal to the 

 skin of the lower part of the front of the leg. 



The medial dorsal cutaneous (internal cruciate branch of the superficial 

 peroneal), passes downward and medial ward across the transverse and the cru- 

 ciate (anterior annular) ligament of the ankle and subdivides into two branches. 

 The medial branch passes to the medial side of the great toe; it also supplies twigs 

 to the skin of the medial side of the foot, and it anastomoses with the deep saphen- 

 ous nerve and with the medial terminal branch of the deep peroneal (anterior 

 tibial) nerve. The lateral branch passes to the base of the cleft between the second 

 and third toes and divides into two dorsal digital branches which supply the 

 adjacent sides of the cleft. 



The lateral branch (intermediate dorsal cutaneous) of the superficial peroneal, 

 in separating from the medial, crosses in front of the cruciate ligament and divides 

 into two dorsal digital branches, which pass beneath the dorsal venous arch. 

 The medial of these branches supplies the adjacent sides of the third and fourth 

 toes (fig. 773). The lateral branch communicates with the sural (external saphen- 

 ous) nerve and is distributed to the adjacent sides of the fourth and fifth toes. 

 This latter branch is frequently replaced by the sural nerve. 



(3) The deep peroneal (anterior tibial) nerve springs from the end of the 

 common peroneal (external popliteal) nerve between the peroneus longus muscle 

 and the neck of the fibula. It passes forward and medialward through the upper 

 part of the origin of the extensor digitorum longus, to the interval between that 

 muscle and the tibialis anterior; then it descends, in the anterior compartment of 

 the leg, to the ankle, where it divides into a medial and a lateral terminal 

 branch (fig. 773). 



In the upper part of the leg the deep peroneal nerve lies between the extensor digitorum lon- 

 gus and tibialis anterior and lateral to the anterior tibial artery. In the middle of the leg it is in 

 front of the artery and between the extensor hallucis longus and tibiahs anterior; then it crosses 

 beneath the extensor hallucis, and in the lower third of the leg it is again to the lateral side of 

 the artery, but between the extensor haUucis longus and the extensor digitorum longus. 



Branches furnished from the trunk of the deep peroneal are muscular, articu- 

 lar, and terminal. 



The muscular branches supply the tibialis anterior, extensor digitorum 

 longus, extensor hallucis longus, and peroneus tertius. 



Articular filaments are given to the ankle-joint and the inferior tibio-fibular 

 articulation. 



Terminal branches.^ — The medial terminal branch passes downward along 

 the side of the dorsalis pedis artery and divides into two dorsal digital branches 

 which supply the adjacent sides of the first and second toes. It also gives fila- 

 ments to the periosteum of the adjacent bones, to the metatarso-phalangeal and 

 interphalangeal articulations, a twig to the dorsal interosseous muscle of the 

 first space, and a perforating twig which connects with the lateral plantar nerve. 

 The lateral terminal branch passes lateralward, beneath the extensor digitorum 

 brevis, and it ends in a gangliform enlargement from which branches are dis- 

 tributed to the extensor digitorum brevis, the tarsal joints, and to the three lateral 

 intermetatarsal spaces. The latter branches supply the neighbouring bones, 

 periosteum, and joints. They give off perforating twigs, which pass through the 

 spaces and anastomose with branches of the lateral plantar nerve, and the 

 most medial also gives a twig to the second dorsal interosseous muscle. 



