THE POSTEKIOB, TIBIAL AKTEEY. 953 



Relations. Anterior. It is in contact anteriorly, and proximo-distally, with the 

 tibialis posterior, the flexor digitorum longus, the posterior surface of the tibia, and the 

 posterior ligament of the ankle-joint. 



Posterior. The artery is crossed about 37 mm. (an inch and a half) distal to its origin 

 by the tibial nerve. Elsewhere it is in contact with the intermuscular fascia which 

 binds down the deep layer of muscles. More superficially the proximal half of the artery 

 is covered by the fleshy parts of the soleus and gastrocnemius muscles, between which is 

 the plantaris ; the distal half of the artery is much nearer the surface, and is covered 

 only by skin and fasciae, except at its termination, where it lies deep to the laciniate 

 ligament. 



Lateral and Medial. The artery is accompanied by two vense comites, one on each side. 

 The tibial nerve lies at first on the medial side of the vessel, then crosses posterior to it, 

 and is continued distally on its lateral side. In the most distal part of its course the artery 

 is separated from the medial malleolus by the tendons of the tibialis posterior and the flexor 

 digitorum longus, whilst the tendon of the flexor hallucis longus lies postero- lateral to it. 



Branches. The posterior tibial gives off numerous branches, the largest of which, 

 the peroneal, forms one of the chief arteries of the leg. The branches include 



(1) Large muscular branches which are distributed to the soleus, the tibialis 

 posterior, the flexor digitorum longus, and the flexor hallucis longus. They anastomose 

 with the deep sural branches of the popliteal artery and the lower medial genicular artery. 



(2) A fibular branch passes laterally, to the neck of the fibula, where it anastomoses 

 with the inferior lateral genicular and the deep sural arteries, and supplies the adjacent 

 muscles. 



(3) The peroneal artery (Fig. 781) is the largest branch of the posterior tibial.- It 

 arises about 25 mm. (an inch) below the distal border of the popliteus, curves laterally 

 across the proximal part of the tibialis posterior to the medial crest of the fibula, 

 along which "it passes to the distal part of the interosseous space. About 25 mm. (an 

 inch) proximal to the ankle-joint it gives off a perforating branch and then passes, 

 posterior to the tibio-fibular syndesmosis and lateral malleolus, to the lateral side of 

 the heel and the foot. It supplies the ankle, the tibio-fibular syndesmosis, and the 

 talo-calcanean joint, and anastomoses with the medial calcanean branch of the lateral 

 plantar artery, and with the tarsal and arcuate branches of the dorsalis pedis. 



As the peroneal artery passes laterally from its origin it lies posterior to the tibialis 

 posterior, and is covered posteriorly by the deep intermuscular fascia and by the soleus. 

 As it descends along the medial crest of the fibula it lies in a fibrous canal 

 between the tibialis posterior in front and the flexor hallucis longus behind. The 

 peroneal artery is accompanied by two vense comites, and is crossed anteriorly and 

 posteriorly by communicating branches between them. 



Branches. (a) Muscular branches are distributed to the soleus, tibialis posterior, flexor 

 hallucis longus, and the peroneal muscles. Some pass through the interosseous membrane and 

 supply the anterior muscles of the leg. 



(6) A nutrient branch enters the nutrient foramen of the fibula. 



(c) A communicating branch, passes across the back of the distal end of the shaft of the tibia, 

 about 25 mm. (an inch) above the tibio-fibular syndesmosis, to anastomose with the posterior 

 tibial artery. 



(d) The perforating branch passes forwards at the junction of the distal border of the inter- 

 osseous membrane and the interosseous tibio-fibular ligament, and runs, in front of the ankle, 

 to the dorsum of the foot, where it anastomoses with the lateral malleolar branch of the anterior 

 tibial artery and with the tarsal branch of the dorsalis pedis ; it also supplies branches to the 

 tibio-fibular syndesmosis, to the ankle-joint, and to the peronaeus tertius. 



(4) The nutrient branch, the largest of the nutrient group of arteries to long 

 bones, springs from the proximal part of the posterior tibial, pierces the tibialis 

 posterior, and enters the nutrient foramen on the posterior surface of the tibia. In the 

 interior of the bone it divides into proximal and distal branches, the former passing 

 towards the proximal extremity of the bone, and the latter towards the distal extremity. 

 Before entering the tibia the nutrient artery gives small muscular branches. 



(5) A communicating branch unites the posterior tibial to the peroneal artery 

 about 25 mm. (an inch) above the tibio-fibular syndesmosis. It passes posterior to the 

 shaft of the tibia and anterior to the flexor hallucis longus. 



(6) Cutaneous branches are distributed to the skin of the medial and posterior part 

 of the leg. 



(7) A posterior medial malleolar branch is distributed to the medial surface of the 

 medial malleolus, anastomosing with a corresponding branch of the anterior tibial artery. 



