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1468 CLINICAL AND TOPOGRAPHICAL ANATOMY 



ARCHES OF THE FOOT 



These are two — the longitudinal and the transverse. 



(A) Longitudinal arch (fig. 1181). — This is by far the most important. Ex- 

 tent : From the heel to the heads of the metatarsal bones. The toes do not add 

 much to the strength and elasticity of the foot. (Humphry.) They enlarge its 

 area and adapt it to inequalities of the ground, are useful in climbing, and in 

 giving an impulse to the step before the foot is taken from the ground, in the third 

 stage of walking. Two pillars. — The late Professor Humphry laid stress on the 

 important differences between these two: — (1) Posterior pillar: This consists of 

 the calcaneus and hinder part of the talus, viz., only two bones in order to secure 

 solidity, and to enable the calf-muscles to act directly upon the heel, Avithout any 

 of that loss of power which would be brought about by many moving joint-sur- 

 faces. (2) Anterior pillar: Here there are many bones and joints to provide (a) 

 elastic springiness, and (6) width. This anterior pillar may again be divided into 

 two: (a) A medial pillar, very elastic, consisting of the talus, navicular, three 

 cuneiforms, and three medial metatarsals. (6) A lateral, formed by the cuboids 

 and two lateral metatarsals. This is stronger and less elastic, and tends to but- 

 tress up the medial pillar. Keystone : This is represented by the summit of the 

 trochlear surface of the talus. 



It differs from the keystones in ordinary arches in the following important particulars 

 (Humphry) : (a) in not being wedge-shaped; (b) in not being so placed as to support and receive 

 support from the two halves of the arch: in front the talus does fulfil this condition by fitting 

 into the navicular; behind, it overlaps the calcaneus without at all supporting it; (c) this arch 

 and the support of its keystone largely depend on ligaments and tendons; (d) it is a mobile 

 keystone: to give it chances of shifting its pressure, and so obtaining rest, its equilibrium is not 

 always maintained in one position. 



(B) Transverse arch (fig. 1179). — This is best marked about the centre of the 

 foot, at the instep, along the tarso-metatarsal joints. This, as well as the longitu- 

 dinal arch, yields in walking, and so gives elasticity and spring. 



Uses of the arches. — (1) They give combined elasticity and strength to the tread. Thus 

 they give firmness, free quickness, and dignity, both in standing and walking, instead of what 

 we see in their absence, viz., the lameness of an artificial limb, and the shuffling or hobbling 

 which goes with tight boots, deformed toes, flat-foot, bunions, corns, etc.; (2) they protect the 

 plantar vessels, nerves, and muscles; (3) they add to man's height; (4) they make his gait a per- 

 fect combination of plantigrade and digitigrade, as is seen in man's walking, when he uses first 

 the heel, then all the foot, and then the toes. (Humphry.) 



Maintenance of the arch. — (1) Plantar fascia. — This is (a) a binding tie between the pillars 

 of the longitudinal arch; (6) it protects the structures beneath; (c) it is a self-regulating ligament 

 and protection. Thus, having a quantity of muscular tissue attached to its upper and back 

 part, is constantly responds by the contraction of this, to the amount of any pressure made upon 

 the foot. (2) Plantar calcaneo-navicular ligament. — This is a thick tie-plate of fibro-cartil- 

 aginous tissue, partly elastic, hence called the 'spring-ligament,' attached to the anterior margin 

 of the sustentaculum tali and under surface of navicular. It is thickest at its medial side, where 

 it blends with the anterior part of the deltoid ligament, and below, where the tibialis posterior, 

 passing into the sole, is in contact with the ligament and gives much support to the head of the 

 talus and the navicular, while it assists the power and spring of this ligament {vide infra). The 

 dropping of the talus and navicular and their projection on the medial side in flat-foot are largely 

 due to the giving way of the above ligament. (3) Calcaneo-cuboid ligaments, (o) Long; 

 ih) short. — These ligaments are the main support of the lateral, firm, and less elastic part of the 

 longitudinal arch. (4) Tibialis posterior.^The reason of this muscle having so many insertions 

 below is to brace together tiie tar.sal bones, and to prevent their separation when, in treading, 

 the elastic anterior pillar tends to widen out. Of these numerous offsets, that to the navicular 

 is the most important. Thus it strengthens the calcaneo-navicular ligament by blending with 

 it, and thus supports the arch at a trying time. By coming into action when the heel is raised, 

 this tendon helf)s the calcaneo-navicular ligament to support the head of the talus, and to main- 

 tain the arch of the foot when the weight of the body is thrown forward on to the instep. In 

 other word.s, the tibialis posterior comes into play j ust when the heaviest of its duties is devolving 

 upon this ligament, viz., when the heel is being raised, and the body-weight is being tlirown 

 over the instep on to the oi)poHite foot. (.5) Peroneus longus. — This raises the lateral pillar, 

 and steadies the lateral side of the arch. Further, by its strong process attached to the first 

 metatarsal bone, it keei)s the great toe strapped down firmly against the ground; thus, keeping 

 down the anterior pillar of the longitudinal arcli, if, aids the firmness of the tread. (Humphry.) 

 (6) Tibialis anterior. — This braces up the keystone of the arch. Thus, by keeping up the first 

 cuneiform, it maintains the navicular, and so indirectly the talus in situ. 



Fig. 1172 will remind the reader of the arrangement of the superficial lym- 

 phatics of the lower extremity. These follow chiefly the saphenous veins, and 

 enter the inguinal nodes, except those from the lateral aspect of the heel which 



