THE REGION OF THE ANKLE AND FOOT 491 



fragments in fair position. It is important that the injury 

 should be recognised since flat-foot may result unless proper 

 treatment is carried out. When the fragments have been moulded 

 into position, the foot is put up at right angles and slightly 

 inverted. 



Fracture of the sustentaculum tali and avulsion of the postero- 

 superior part of the calcaneus are rare injuries (Fig. 146). 



In the examination of radiograms of the tarsus, the presence 

 of the calcanean epiphysis and the occasional os trigonum 

 (p. 489) must be borne in mind. 



Fractures of the metatarsals are difficult to recognise as the 

 oedema may be considerable, and there is little or no displace- 

 ment, owing to the way in which the bones are bound together 

 in the transverse arch of the foot. The prominent base of the 

 fifth metatarsal may be fractured when the patient falls heavily 

 on the inverted foot (Jones). 



The Deep Fascia of the sole of the foot is termed the plantar aponeurosis. 

 Like the palmar aponeurosis (p. 82), it consists of a strong central and two 

 weak collateral parts. The central portion is attached posteriorly to the 

 calcanean tuberosity, and anteriorly it divides into five slips, which are 

 connected to the fibrous flexor sheaths of the toes (cf. palm of hand, p. 83). 

 It is the central portion of the plantar aponeurosis, which normally helps to 

 support the longitudinal arch of the foot, and it is much shortened in pes 

 cavus and in some of the varieties of talipes. 



The weak, medial part of the plantar aponeurosis covers the abductor 

 hallucis, which extends from the calcanean tuberosity to the medial side of 

 the base of the first phalanx of the hallux. 



Owing to the density of the central part of the plantar aponeurosis, 

 swelling first becomes apparent on the dorsum of the foot in inflammatory 

 conditions of the sole or of the articulations (cf. palm of hand, p. 82). 



The small muscles of the sole of the foot are of less importance than the 

 corresponding muscles in the palm of the hand, as the foot is primarily 

 required to be a stable support for the body weight, and the movements of 

 the individual toes, therefore, are of less consequence. 



The medial plantar nerve (L. 4, 5, and S. i) arises from the tibial nerve 

 under cover of the laciniate ligament (p. 471), and runs forwards with the 

 medial plantar artery. It corresponds to the median nerve in the palm of 

 the hand, and, though it supplies few muscles, it supplies a large cutaneous 

 area, including the plantar aspects of the medial three toes and the tibial 

 side of the fourth toe. 



The lateral plantar nerve (S. i and 2) corresponds to the ulnar nerve in 

 the palm of the hand (p. 85). It arises from the tibial nerve under cover 

 of the laciniate ligament, and accompanies the lateral plantar artery and the 

 plantar arch. It supplies most of the muscles of the sole, the skin of the 

 lateral part of the sole, and the plantar aspects of the fifth toe and the fibular 

 side of the fourth toe 



At the distal border of the laciniate ligament the posterior tibial artery 

 divides into the lateral and medial plantar arteries. The medial plantar, 

 which is usually a small vessel, passes forwards between the abductor hallucis 



