57 



APPLIED ANATOMY. 



Paralysis of the calf muscles is not rare, while that of the deep flexors is less 

 common. The question of paralysis must be studied with reference to each individ- 

 ual case, because the affected muscles are not always completely paralyzed, neither 

 are all the muscles of a group. 



THE ACTION OF THE MUSCLES AS ABDUCTORS AND ADDUCTORS. 



Lateral 



Tibialis anterior 



Extensor longus 

 hallucis 



Extensor longus 

 digitorum 



movements of the foot are comparatively weak when compared with 



those of flexion and extension. They are 

 intended largely to maintain the balance 

 or equilibrium and to adapt the position of 

 the foot to uneven surfaces, etc. Three 

 muscles act very distinctly as abductors ; 

 they are the peroneus longus, brevis, and 

 tertius. Two act as distinct adductors, 

 viz. : the tibialis anterior and the tibialis 

 posterior. 



The muscles of the calf act more as 

 abductors than adductors, because the in- 

 sertion of the tendo calcaneus (Achillis) 

 is not directly behind the ankle-joint but 

 more to its outer side. 



When the foot is deformed in the 

 position of inversion, as in club-foot, the 

 tibialis anterior and posterior are usually 

 contracted, but when in the position of 

 eversion, as in flat-foot, then spasm of the 

 peronei or calf muscles is frequent. 



Plantar flexion of the foot is a far 

 more powerful movement than extension 

 flexion is associated with adduction or in- 

 version and extension with abduction or 

 eversion ; hence it is that inversion is the 

 position of strength and eversion of weak- 

 ness. Feats of strength and agility cannot 

 be performed by those who have markedly 

 everted feet. 



SURFACE ANATOMY OF THE 

 FOOT. 



For the clinician and operator an exact 

 knowledge of surface anatomy is absolutely 

 essential. It can readily be acquired be- 

 cause the various bony points and tendons 

 are usually evident both to touch and sight. 

 Bony Landmarks. There are five 

 prominent bony points : they are the in- 

 ternal and external malleoli, the tubercles 

 of the os calcis and navicular (scaphoid} 

 and the tuberosity of the fifth metatarsal 

 bone. 



The internal malleolus is large and flat 

 and has a somewhat rounded lower edge. 

 It is above and anterior to the external malleolus. Immediately in front of its anterior 

 edge runs the commencement of the long saphenous vein. Around its lower pos- 

 terior border runs the tendon of the tibialis posterior muscle on its way to the tubercle 

 of the scaphoid. 



Peroneus tertius 

 Peroneus brevis 

 Peroneus longus 



PIG. 588. The foot in an abducted or pronated 

 position. 



