474 THE INFERIOR EXTREMITY 



peronsei are retained in place by the inferior retinaculum (p. 471), 

 and each possesses a synovial sheath, which is continuous 

 proximally with the common sheath. 



The brevis is inserted into the dorsal aspect of the tuberosity 

 of the fifth metatarsal, and its synovial sheath reaches almost 

 to the insertion. The longus enters the groove on the plantar 

 surface of the cuboid and crosses the sole of the foot obliquely 

 to be inserted into the lateral side of the base of the first 

 metatarsal and the adjoining part of the medial cuneiform (Fig. 

 147). In the foot the peronaeus longus is very deeply placed, 

 and it is surrounded by a synovial sheath which may or may 

 not be continuous with the sheath which encloses it on the 

 lateral aspect of the ankle. 



Both muscles act as extensors and evertors of the foot, and 

 they are supplied by the superficial peroneal (musculo-cutaneous) 

 nerve (L. 4, 5, and S. i). 



The tendon sheaths of the peronsei are sometimes the site of 

 tuberculous disease, and it is important that the condition 

 should be recognised at an early stage. Otherwise the disease 

 may spread along the sheath of the longus into the sole of the 

 foot and infect the tarsal joints. Good exposure is obtained 

 by a lateral J -shaped incision from behind the lateral malleolus 

 to the base of the fifth metatarsal. To ensure the complete 

 removal of the disease, the retinacula must be divided and 

 their synovial lining dissected away. Thereafter the retinacula 

 should be reunited over the replaced tendons. 



The Posterior Compartment of the Leg. The muscles 

 of the posterior compartment consist of a superficial and a deep 

 group. The superficial group comprises the gastrocnemius, 

 the plantaris, and the soleus, while the deep group comprises 

 the flexor hallucis longus, the tibialis posterior, and the flexor 

 digitorum longus. 



The Gastrocnemius arises from the distal part of the femur by two heads 

 of origin, which are inserted into a common tendon, half-way down the leg. 

 The Soleus, which lies under cover of the preceding muscle, arises from the 

 proximal part of the posterior surface of the fibula and by a linear origin from 

 the popliteal line and the medial border of the tibia. These two muscles 

 together constitute the Triceps Surse, and their tendons unite to form the 

 tendo calcaneus (Achillis), which is inserted into the middle part of the posterior 

 surface of the calcaneus. A small bursa is interposed between the tendon 

 and the upper part of the posterior surface of the bone. It sometimes becomes 

 inflamed after excessive walking, and it may be affected in gout or gonorrhoeal 

 rheumatism. 



The Plantaris, which arises close to the lateral head of the gastrocnemius, 



