368 THE INFERIOR EXTREMITY 



Dissection. The dissector must now proceed to the dissection 

 of the contents of the three sections of the posterior osteo-fascial 

 compartment, commencing with the superficial section. 



First clean carefully the laciniate ligament, and secure the 

 medial calcanean branches of the posterior tibial artery and of the 

 tibial nerve which pierce it. Note that it is continuous proximally 

 with the deep fascia of the posterior part of the leg, and that distally 

 it gives attachment to the abductor hallucis ; then make a longi- 

 tudinal incision through the deep fascia, down the middle of 

 the back of the leg, from the popliteal region proximally to the 

 calcaneus distally. Turn the two flaps so defined to the medial 

 and lateral sides respectively. Detach the distal end of the 

 medial flap from the ligamentum laciniatum, but do not injure 

 that ligament, and detach the distal end of the lateral flap from 

 the superior peroneal retinaculum, but, if possible^ avoid injury 

 to the retinaculum. Note the attachment of the medial flap 

 to the medial border of the tibia, and the connection of the 

 lateral flap with the posterior fibular septum, by means of which 

 attachment to the lateral crest of the fibula is attained (Figs. 

 152, 155). 



When the connections of the deep fascia have been displayed, 

 make an opening into the mucous sheath of the tendo calcaneus, 

 at one or other border of the tendon, and, by inflation, injection 

 or exploration with a blunt probe, attempt to demonstrate the 

 extent of the sheath, which is somewhat variable. Next clean 

 the gastrocnemius and the tendo calcaneus, and remove the 

 thick pad of fat which lies in front of the tendo calcaneus, and 

 separates it from the first fascial septum of the posterior compart- 

 ment. Now examine the distal portion of the first fascial septum 

 and note the important part it plays in binding down the muscles 

 of the middle section of the compartment, and in the formation 

 of the ligamentum laciniatum. 



If the medial head of the gastrocnemius was not divided 

 when the popliteal fossa was dissected, divide it now, at the 

 level of the knee joint, and turn it laterally ; then clean the sural 

 arteries from the popliteal trunk, and the branches of the tibial 

 nerve which supply the gastrocnemius. Raise the proximal 

 part of the divided muscle, and note the bursa which intervenes 

 between it and the semimembranosus. The bursa usually 

 communicates with a bursa under cover of the semimembranosus 

 which, in its turn, communicates with the cavity of the knee 

 joint. Open the bursa and explore its extent with a blunt probe, 

 if that has not already been done (see p. 309). Next follow the 

 nerve to the soleus, which was found when the popliteal fossa 

 was dissected (see p. 310). It springs from the tibial nerve in 

 the popliteal fossa, on the medial side of the popliteal artery, 

 crosses the posterior surface of the distal part of the artery, 

 passes between the plantaris and the lateral head of the gastro- 

 cnemius, and enters the posterior surface of the soleus. When 

 the nerve to the soleus has been cleaned and followed to its 

 termination, clean the plantaris, and follow its slender tendon 

 to its insertion into the posterior surface of the calcaneus on the 

 medial side of the tendo calcaneus. 



Superficial Muscles. The superficial muscles of the calf 

 of the leg are three in number, viz., the gastrocnemius, the 



