SOLE OF THE FOOT 385 



( Tendon of flexor digitorum longus. 



c j i I Ouadratus plantse. 



Second layer. umbrical ^^ 



\ Tendon of flexor hallucis longus. 



( Flexor hallucis brevis. 

 Third layer. -j Adductor hallucis, oblique and transverse heads. 



( Flexor digiti quinti brevis. 



( Interosseous muscles. 

 Fourth layer. -j Tendon of peronseus longus. 



I Tendon of tibialis posterior. 



Dissection. Separate the lateral and medial portions of 

 the plantar aponeurosis from the subjacent muscles. Whilst 

 that is being done great care must be taken to avoid injury to 

 the digital branch from the lateral plantar nerve to the lateral 

 side of the little toe, and the digital branch of the medial plantar 

 nerve and the digital artery to the medial side of the great toe. 

 To avoid injuring those structures seize a reflected portion of 

 the intermediate part of the plantar aponeurosis and cut, hori- 

 zontally through the septum which dips deeply from it at the 

 side of the flexor digitorum brevis, lateral or medial side as the 

 case may be, then keep the edge of the scalpel playing closely 

 against the deep part of the aponeurosis from which the septum 

 springs. Difficulty will be experienced in the posterior part of the 

 foot, where the deep surface of each piece of the aponeurosis gives 

 origin to fibres of the subjacent muscle. The muscular fibres 

 must be detached and the posterior ends of the two pieces of 

 aponeurosis must be separated from the calcaneus. 



When the reflection of the medial and lateral parts of the 

 aponeurosis is completed the following structures are exposed. 

 Medially, the abductor hallucis and the digital artery and nerve 

 to the medial side of the great toe. Laterally, the abductor digiti 

 quinti and the digital artery and nerve to the lateral side of the little 

 toe. In the intermediate area, the flexor digitorum brevis and its 

 four terminal tendons, and the tendon of the flexor hallucis longus 

 will be found, with the digital vessels and nerves and the lumbri- 

 cal muscles in the intervals between the flexor tendons ; whilst 

 deep to the tendon of the flexor hallucis longus, part of the flexor 

 hallucis brevis is visible, and between the abductor digiti quinti 

 and the flexor digitorum brevis the flexor digiti quinti brevis and 

 the interossei in the fourth space can be seen. 



When the structures mentioned have been identified cut 

 down into the posterior part of the interval between the abductor 

 hallucis and the flexor digitorum brevis, immediately in front 

 of the medial process of the calcaneus, and secure the posterior 

 parts of the medial and lateral plantar nerves and arteries ; then 

 follow the medial plantar nerve forwards and secure first the 

 branches which it gives to the abductor hallucis and the flexor 

 digitorum brevis, and then its four terminal digital branches. 

 As the first digital branch, that to the medial side of the great 

 toe, is followed it will be found to give a twig to the flexor hallucis 

 brevis, whilst the second digital branch, which supplies the 

 adjacent sides of the first and second toes, gives a twig to the 

 first lumbrical muscle, and the fourth digital branch is connected 

 by a communicating strand with the medial digital branch of 

 the lateral plantar nerve. 

 VOL. I 25 



