500 A MANUAL OF ANATOMY 



fibrous canal ; (3) the internal vena comes, posterior tibial artery, 

 external vena comes, and posterior tibial nerve, all occupying a 

 second fibro-osseous canal ; (in cases of an early division of the 

 posterior tibial nerve into external and internal plantar nerves 

 these two nerves are found in this canal, the internal on the inner 

 side of the internal vena comes, and the external on the outer side 

 of the external vena comes) ; (4) the tendon of the flexor longus 

 hallucis, occupying the third fibro-osseous canal, and lying in the 

 groove at the outer part of the posterior border of the lower end of 

 the tibia. Each of the three tendons mentioned is invested by a 

 special synovial sheath. The internal annular ligament is pierced 

 by the calcaneo-plantar branch of the posterior tibial nerve and 

 the internal calcaneal branch of the posterior tibial artery. 



The anterior annular ligament is composed of two divisions. 

 One division is situated on the front of the leg above the ankle- 



Tibialis Amicus Li 



Extensor Proprius Hallucis 



Tibialis Posticus 

 Flexor Longus Digitorum 



_. Flexor Longus Hallucis 



Fig. 241. — The Synovial Sheaths at the Ankle (Internal View) 

 (after L. Testut's 'Anatomie Humaine'). 



joint, and is called the superior anterior annular ligament. The 

 other division lies in front of the bend of the ankle, and is 

 called the inferior anterior annular ligament, anterior annular 

 ligament proper, or lambdoid ligament. 



The superior anterior annular ligament is a broad band extending 

 transversely between the anterior borders of the tibia and fibula, 

 and measuring about 2 inches from above downwards. Imme- 

 diately beyond it the deep fascia is exceedingly thin. The 

 structures passing beneath it, in order from within outwards, are 

 (i) tibialis anticus, (2) extensor proprius hallucis, (3) internal vena 

 2omes, (4) anterior tibial artery, (5) external vena comes, (6) anterior 

 tibial nerve, (7) extensor longus digitorum, and (8) peroneus 

 tertius. These structures occupy one common compartment, thCj 

 tibialis anticus tendon alone being surrounded by a synovial sheath. 



