REGIONS OF THE LEG. 



131 



tendo Achillis, of which it completes the 

 fibrous canal, formed posteriorly by the super- 

 ficial layer; the other remains applied over the 

 posterior surface of the deep muscles, and both 

 arrive at the heel. 



In its inferior third, this aponeurosis thus 

 circumscribes three spaces. One is filled by 

 the tendon of the muscles of the calf. The se- 

 cond incloses the flexor muscles of the toes, 

 and the vessels. The third, which separates 

 the two others, lies between the tendo Achillis 

 and the posterior surface of the last-named 

 muscles. The latter is remarkable, from being 

 filled with fat and fibrous filaments, interlaced 

 in various directions.* 



We have, for convenience of description, de- 

 tailed the anatomy of the superficial parts of 

 the leg, without particular reference to the re- 

 gional divisions, which become more defined, 

 distinct, and practical as we investigate the re- 

 lations of the deeper seated parts, and to which 

 we shall therefore now limit ourselves. 



In the anterior region, comprising all those 

 muscles which rest upon the tibio-fibular fossa, 

 we find, on dissecting the fascia from the upper 

 part, only two muscles exposed, viz. the tibialis 

 anticus and extensor communis digitorum. 

 Lower down, we see in addition the extensor 

 proprius pollicis coming out between the two 

 last, and theperoneus tertius a slip of the outer 

 side of the extensor communis. These four 

 are, as it were, bound down in a canal, formed 

 anteriorly by the aponeurosis, posteriorly by 

 the tibia, fibula, and interosseous ligament. 

 The direction of the tibialis anticus, its size, 

 and boundaries should be borne in mind, as 

 these form the surest guide for cutting down 

 upon the anterior tibial artery. This muscle is 

 of a prismatic form, tapering downwards, and 

 its outer edge is indicated externally by a 

 sulcus in the integuments made more apparent 

 by extension of the foot. It is found more ac- 

 curately by tracing a line from the middle of 

 the space between the crest of the tibia 

 and the fibula to the middle of the instep ; and 

 here, between this muscle and the extensor 

 communis, the artery runs. The external mus- 

 cles are the peronei longus and brevis ; they 

 are enveloped in a sheath of the aponeurosis, 

 and are applied, for some extent, to the exter- 

 nal surface of the fibula. They are completely 

 separated from the extensors and from all the 

 muscles of the posterior region by the two apo- 

 neurotic septa attached to the anterior and 

 posterior edges of the bone. The adherence of 

 the muscular fibres continuing until just above 

 the outer malleolus, a transverse section, in the 

 two superior thirds, does not entirely destroy 

 their action upon the foot, while, lower down, 

 it would render abduction almost impossible. 

 We have not heard of an instance of the entire 

 rupture of any of these muscles, nor is it an 

 accident likely to occur, as they are not, from 

 their situation, likely to be called upon for any 

 very great exertion of power; but these muscles 

 are occasionally liable to the accidental rupture 



* See Velpeau's Anatomy of Regions, translated 

 by Hancock. 



of some of their fibres, a circumstance attended 

 with much more pain and distress in moving 

 than the apparently slight nature of the accident 

 might lead us to expect. We have had lately 

 a case of this kind under our care, where the 

 suffering and the injury to the movements of 

 the foot were so great as at first to lead us to 

 suspect a much more serious extent of injury 

 than really existed. It was occasioned by at- 

 tempting to push along a sack of corn with 

 both knees, both feet being on the ground, and 

 the heels raised, while the upper part of the 

 sack was held in the arms. 



The only artery of importance in this region 

 is the anterior tibial. It commences from the 

 trunk of the popliteal nearly at right angles, 

 traverses the opening in the upper part of the 

 interosseous ligament, close to the neck of the 

 fibula, and below the head of the tibia. The 

 angular curve which the artery makes at this 

 part of its course, according to M. Kibes, ac- 

 counts for the great retraction of it after ampu- 

 tation of the leg.* It descends upon the inter- 

 osseous ligament, in the direction of a line 

 drawn from the middle of the space between 

 the head of the fibula and the crest of the 

 tibia, to the middle of the instep. Through 

 the upper part of its course it lies upon the in- 

 teiosseous ligament; as it descends it gradually 

 advances upon the tibia, and runs upon the 

 anterior surface of this bone through its lower 

 third. It is found at the upper third of the 

 leg, between the tibialis anticus and extensor 

 communis digitorum; in the middle third, its 

 course is between the tibialis anticus and the 

 extensor longus pollicis, and about four inches 

 above the ankle-joint it passes obliquely under 

 the tendon of this last muscle, and then is 

 found between its tendon and that of the ex- 

 tensor communis. It runs between two veins 

 through its whole course. The nerve is on its 

 outer side above ; in front in the middle; and 

 internal below. An extensible but resistant 

 cellular sheath unites the whole. It is evident, 

 that in the upper part of its course the artery 

 will be found much deeper than at the lower, 

 when it is lying among the tendons, but in the 

 living subject the natural state of tension of the 

 muscles keeps these tendons more elevated 

 than after death, and we shall consequently find 

 the artery, even in this situation, deeper than 

 from dissection we might have been led to an- 

 ticipate. The surgeon will find little difficulty 

 in discovering this artery when it is required to 

 be tied. The marks for his guidance are clear, 

 and the situation of the vessel on the whole 

 pretty uniform ; but owing to the depth of its 

 situation above, and to the immediate vicinity 

 of the veins and nerve, some difficulty will be 

 experienced in excluding these from the liga- 

 ture. The only branch from it of any surgical 

 importance is the recurrent tibial. This arises 

 just after the trunk has passed through the in- 

 terosseous ligament, and passes upwaids in nu- 

 merous branches to the parts below and to the 

 outer side of the knee-joint, anastomosing freely 

 with the inferior external articular artery. These 



* See Velpeau's Anatomy of Regions, p. 473. 



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