REGION OF THE ANKLE. 



149 





living subject, when the individual attempts to 

 flex the foot or extend the toes, these tendons 

 will not only form an unseemly projection 

 upon the instep, but also the accuracy and per- 

 fection of these motions will be much im- 

 paired. Upon the lateral parts of the region, 

 the fascia is so intimately united to the peri- 

 osteum, that it is almost impossible to separate 

 them from each other, and hence some have 

 denied its existence here. Behind both mal- 

 leoli, it becomes however again very distinct, 

 forming in both situations a band similar to 

 that which we have just seen upon the instep. 

 The internal annular ligament arising from 

 the posterior edge of the inner malleolus 

 passes backwards to the os calcis; it is 

 thrown like a bridge across that deep gutter 

 which divides the heel and ankle from each 

 other, and it is destined like the anterior liga- 

 ment to form a covering to the tendons and 

 other parts which pass through this region. 

 Like the anterior, the internal ligament also 

 consists of two layers closely united to each 

 other. To express more distinctly the me- 

 chanical disposition of these layers, we may 

 say that the bridge formed by the internal 

 annular ligament consists of two arches ; 

 through the anterior arch are transmitted the 

 tibialis posticus and the flexor digitorum 

 longus tendons, wrapped each in its own 

 synovial theca : the posterior arch is occupied 

 with the posterior tibial vessels and nerves, 

 and the tendon of the flexor longus pollicis 

 muscle. Having thus safely conducted these 

 important organs, the superficial layer of the 

 ligament fixes itself into the os calcis, while 

 the deep one passes backwards and upwards 

 to become continuous with the deep fascia of 

 the leg. Behind the external malleolus, the 

 fascia forms another but less remarkable liga- 

 ment, which Blandin calls the " external an- 

 nular:" this passes from the fibula to the 

 astragalus, and forms with the posterior edge 

 of the malleolus a deep osseo-fibrous canal for 

 the transmission of the peroneus longus and 

 brevis tendons. 



At the back part of this region, the fascia is 

 also found covering the great tendo Achillis ; 

 this tendon also, like the smaller ones we have 

 just spoken of, is not merely covered super- 

 ficially, but is contained within a sheath, 

 formed by the splitting of the fascia into two 

 layers : the posterior layer we may regard as 

 the continued fascia itself; the deep one passes 

 in front of the tendon, and if we trace this up- 

 wards, we shall find it becoming ultimately 

 continuous with the deep fascia of the leg. An 

 acquaintance with the disposition and structure 

 of the fascia we have thus described, will en- 

 able the surgical anatomist, in almost every in- 

 stance, to explain the time, situation, and pro- 

 gress of abscesses occurring in this region: he 

 will at once comprehend that three distinct 

 sorts of abscess may form here : one in the 

 subcutaneous tissue, and which being super- 

 ficial to the fascia can hardly penetrate deeply 

 toward the joint ; another, occurring between 

 the two layers of that membrane, in those 

 situations \\herc it splits to include the ten- 



dons ; such an abscess will have little tendency 

 to point in front, being bound down by the 

 superficial layer of the fascia, or to penetrate 

 deeply for a similar reason ; but to its free 

 passage upwards or downwards in the course 

 of the tendons, little or no obstacle is presented. 

 Lastly, matter may accumulate under both 

 layers of the fascia, where its deep position and 

 close confinement render it alike dangerous, and 

 of difficult detection. 



4. The next stratum is perhaps less entitled 

 to that name than those we have hitherto 

 described. Instead of forming, like them, a 

 general investment for the whole region, it 

 consists of several distinct and independent or- 

 gans scattered irregularly about the joint : we 

 shall enumerate them in the order in which we 

 propose to treat of them, viz., tendons, mus- 

 cles, arteries, veins, lymphatics, and nerves. 



a. Tendons. Upon the instep we find no 

 fewer than seven tendons passing towards the 

 foot : the internal is the largest of all, it is that 

 of the tibialis anticus running obliquely for- 

 wards and inwards to the inner cuneiform bone. 

 Close upon its outer side is the tendon of the 

 extensor pollicis; still more outwards we meet 

 with the four tendons of the extensor digitorum 

 longus, and most externally of all, or nearest 

 to the outer ankle, that of the peroneus tertius. 

 We need not revert to the subject of the fibrous 

 sheaths furnished to these tendons by the fascia 

 or annular ligament; but we should here care- 

 fully observe, that both sheaths and tendons are 

 completely lined by a synovial apparatus. He 

 who is at all acquainted with the general patho- 

 logy of synovial membrane will understand why 

 it is that effusions so frequently form about the 

 instep ; why adhesion of the opposite walls of 

 these synovial sheaths will almost destroy the 

 power of extending the toes and of flexing the 

 foot ; and, lastly, he cannot but draw the im- 

 portant practical deduction, that in operations 

 about the instep we should avoid, if possible, 

 cutting into these synovial sacs. 



Behind the inner malleolus we meet with 

 three tendons, that of the tibialis posticus 

 most anterior, and in close connexion with the 

 posterior surface of the malleolus internus; that 

 of the flexor digiterum longus a little further 

 back; and still more posterior, and at a little 

 distance from the others, the tendon of the 

 flexor pollicis longus. These are included, as 

 we have already explained, in fibrous sheaths 

 formed by the internal annular ligament, each 

 sheath and tendon having its own synovial 

 lining. We may here observe a good anatomical 

 reason, why inflammation affecting the sheath 

 of the flexor digitorum will, cateris paribus, 

 be more likely to prove dangerous than that of 

 the tibialis posticus : for, as the synovial sheaths 

 of the former extend along the whole sole of the 

 foot, little or no obstacle is presented to the 

 disease extending itself into that region : whereas 

 the tendon of the tibialis being inserted, not 

 upon the sole, but rather upon the inner edge 

 of the foot, its synovial membrane forms here 

 a cul-de-sac, no doubt presenting some obsta- 

 cle to the inflammation extending beyond this 

 point. Behind the outer rmilledlus there exists 



