386 THE INFERIOR EXTREMITY 



The trunk and branches of the relatively small medial plantar 

 artery accompany the trunk and branches of the medial plantar 

 nerve, and must be cleaned as the nerve and its branches are 

 dissected out of the surrounding fascia. 



When the medial plantar vessels and nerves have been dis- 

 played, cut down into the interval between the flexor digitorum 

 brevis and the abductor digiti quinti, behind the pi ejecting base 

 of the metatarsal bone of the fifth toe, and secure the trunk of 

 the lateral plantar nerve, before it divides into its superficial and 

 deep divisions, and the accompanying lateral plantar artery 

 which lies lateral to the nerve. As the nerve passes forwards 

 it divides into a superficial and a deep branch, at the level of the 

 base of the fifth metatarsal bone and, at the same level, the lateral 

 plantar artery, accompanied by the deep branch of the nerve, 

 turns medially and deeply to become the plantar arterial arch. 

 Follow the superficial division of the nerve forwards, and secure 



(1) the muscular branches which it gives to the flexor digiti 

 quinti brevis, and the interossei of the fourth interosseous space ; 



(2) its two digital branches, one to the lateral side of the little toe, 

 and one which divides to supply the adjacent sides of the fourth 

 and fifth toes ; the latter is connected, by a communicating twig, 

 with the fourth digital branch of the medial plantar nerve. Clean 

 also the arteries which accompany the nerves. Now divide 

 the muscular belly of the flexor digitorum brevis, transversely, 

 at the middle of its length ; turn the posterior part backwards, 

 and define its attachments to the medial and lateral processes 

 of the calcaneus ; throw the anterior part forwards towards the 

 toes where its tendons enter the flexor sheaths, which will be 

 examined later. Next detach the abductor hallucis from the 

 medial process of the calcaneus, but not from the laciniate 

 ligament, and turn it medially. The structures now exposed 

 are (i) the first parts of the lateral plantar vessels and 

 nerve, and their branches ; (2) deep to the vessels and nerve, 

 the quadratus plantae ; (3) posteriorly, between the two heads 

 of the quadratus plantae, the posterior part of the long plantar 

 ligament ; (4) medial to the quadratus plantae the tendon of 

 the flexor digitorum longus dividing, anteriorly, into four 

 slips from which the lumbrical muscles arise; (5) medial to 

 the flexor longus digitorum a further portion of the tendon 

 of the flexor hallucis longus lying between the two heads of 

 the flexor hallucis brevis (Figs. 170, 171). 



Clean, first, the lateral plantar nerve and its muscular branches. 

 The first branch is the branch to the abductor digiti quinti. It 

 lies far back, close to the processes of the calcaneus. The 

 branch to the quadratus plantae is a little further forward. In 

 addition there are a number of cutaneous branches which become 

 superficial along the interval between the abductor digiti quinti 

 and the flexor digitorum brevis. Next clean the lateral plantar 

 artery and follow its medial calcanean branch to the posterior 

 part of the interval between the flexor digitorum brevis and the 

 abductor hallucis where it becomes superficial. It is distributed 

 to the fat and skin of the heel. After the vessels and nerves are 

 cleaned clean the muscles and tendons. 



M. Flexor Digitorum Brevis. The short flexor of the 

 toes arises from the medial process of the calcaneus, from 



