The flexor digitorum longus and tibialis posterior lie on the posterior aspect of the interosseous membrane and tibia. Flexor hallucis longus lies on the posterior border of the fibula.
The posterolateral approach to the tibia is useful to expose the middle two thirds of the tibia, and is often used when the anterior and anterior medial approaches are limited by skin issues. It is useful for plating of fractures and treatment of nonunions including bone grafting because it allows for soft tissue coverage of a bone that is otherwise subcutaneous.
The superficial internervous plane lies between the gastrocnemius/soleus (tibial nerve) and peroneal muscles (superficial peroneal nerve). The deep dissection involves detaching FHL and soleus from the posterior border of the fibula and then dissecting medially to separate the posterior tibialis off the the posterior surface of the interosseous membrane and the posterior tibialis and flexor digitorum longus off the posterior surface of the tibia.
Illustration A shows a cross section of the surgical approach.
Crenshaw A Jr: Surgical techniques and approaches , in Canale T (ed): Campbell’s Operative Orthopaedics ed 9. St. Louis, MO, Mosby, 1998, pp 56-58