Surgical Anatomy Part 46

G. The popliteal vein joined by the short saphena vein.

H. The middle branch of the sciatic nerve.

I. The outer (peronaeal) branch of the sciatic nerve.

K. The posterior tibial nerve continued from the middle branch of the sciatic, and extending to K, behind the inner ankle.

L. The posterior (short) saphena vein.

M M. The fascia covering the gastrocnemius muscle.

N. The short (posterior) saphena nerve, formed by the union of branches from the peronaeal and posterior tibial nerves.

O. The posterior tibial artery appearing from beneath the soleus muscle in the lower part of the leg.

P. The soleus muscle joining the tendo Achillis.

Q. The tendon of the flexor longus communis digitorum muscle.

R. The tendon of the flexor longus pollicis muscle.

S. The tendon of the peronaeus longus muscle.

T. The peronaeus brevis muscle.

U U. The internal annular ligament binding down the vessels, nerves, and tendons in the hollow behind the inner ankle.

V V. The tendo Achillis.

W. The tendon of the tibialis posticus muscle.

X. The venae comites of the posterior tibial artery.

PLATE 66.

A C D E F G H I indicate the same parts as in Plate 65.

B. The inner condyle of the femur.

K. The plantaris muscle lying upon the popliteal artery.

L. The popliteus muscle.

M M M. The tibia.

N N. The fibula.

O O. The posterior tibial artery.

P. The peronaeal artery.

Q R S T U V W. The parts shown in Plate 65.

X. The astragalus.

[Ill.u.s.tration: Left leg, showing muscles, blood vessels and other internal organs.]

Plates 65, 66

COMMENTARY ON PLATES 67 & 68.

THE SURGICAL DISSECTION OF THE ANTERIOR CRURAL REGION, THE ANKLES, AND THE FOOT.

Beneath the integuments and subcutaneous adipose tissue on the fore part of the leg and foot, the fascia H H, Plate 67, Figure 2, is to be seen stretched over the muscles and sending processes between them, thus encasing each of these in a special sheath.

The fascia is here of considerable density. It is attached on the inner side of the leg to the spine of the tibia, D, Plate 67, Figure 2, and on the outer side it pa.s.ses over the peronaeal muscles to those forming the calf. Between the extensor communis digitorum, B b, and the peronaeus longus, F, it sends in a strong process to be attached to the fibula, E.

In front of the ankle joint, the fascia is increased in density, const.i.tuting a band (anterior annular ligament) which extends between the malleoli, forms sheaths for the several extensor tendons, and binds these down in front of the joint. From the lower border of the annular ligament, the fascia is continued over the dorsum of the foot, forming sheaths for the tendons and muscles of this part. Behind the inner malleolus, d, Plate 67, Figure 1, the fascia attached to this process and to the inner side of the os calcis appears as the internal annular ligament, which being broad and strong, forms a kind of arch, beneath which in special sheaths the flexor tendons, and the posterior tibial vessel and nerve, pa.s.s to the sole of the foot. On tracing the fascia from the front to the back of the leg, it will be seen to divide into two layers--superficial and deep; the former pa.s.ses over the muscles of the calf and their common tendon (tendo Achillis) to which it adheres, while the latter pa.s.ses between these muscles and the deep flexors. The deep layer is that which immediately overlies the posterior tibial and peronaeal vessels and nerves. While exposing the fascia on the forepart of the leg and dorsum of the foot, we meet with the musculo-cutaneous branch of the peronaeal nerve, which pierces the fascia at about the middle of the limb, and descends superficially in a direction between the fibula, and the extensor longus digitorum muscle, and after dividing into branches a little above the outer ankle, these traverse in two groups the dorsum of the foot, to be distributed to the integuments of the five toes. On the inner side of the tibia, D, Plate 67, Figure 1, will be seen the internal or long saphena vein, B B, which commencing by numerous branches on the dorsal surface of the foot ascends in front of the inner ankle, d, to gain the inner side of the leg, after which it ascends behind the inner side of the knee and thigh, till it terminates at the saphenous opening, where it joins the femoral vein. In its course along the lower part of the thigh, the leg and the foot, this vein is closely accompanied by the long saphenous nerve, derived from the anterior crural, and also by a group of lymphatics.

By removing the fascia from the front of the leg and foot, we expose the several muscles and tendons which are situated in these parts. In the upper part of the leg the tibialis anticus, A, Plate 67, Figure 2, and extensor-communis muscle, B, are adherent to the fascia which covers them, and to the intermuscular septum which divides them. In the lower part of the leg where these muscles and the extensor pollicis, C, terminate in tendons, a b c, they are readily separable from one another. The tibialis anticus lies along the outer side of the tibia, from which, and from the head of the fibula and interosseous ligament, it arises tendinous and fleshy. This muscle is superficial in its whole length; its tendon commencing about the middle of the leg, pa.s.ses in a separate loose sheath of the annular ligament in front of the inner ankle, to be inserted into the inner side of the cuneiform bone and base of the metatarsal bone of the great toe. The extensor communis digitorum lies close to the outer side of the anterior tibial muscle, and arises from the upper three-fourths of the fibula, from the interosseous ligament and intermuscular septum. At the lower part of the leg, this muscle ends in three or four flat tendons, which pa.s.s through a ring of the annular ligament, and extending forwards, b b b b, over the dorsum of the foot, become inserted into the four outer toes. The peronaeus tertius or anterior, is that part of the common extensor muscle which is inserted into the base of the fifth metatarsal bone. On separating the anterior tibial and common extensor muscles, we find the extensor pollicis, C c, which, concealed between the two, arises from the middle of the fibula, and the interosseous ligament; its tendon pa.s.ses beneath the annular ligament in front of the ankle joint, and after traversing the inner part of the dorsum of the foot, becomes inserted into the three phalanges of the great toe. Beneath the tendons of the extensor communis on the instep, will be seen the extensor digitorum brevis, K K, lying in an oblique direction, between the upper and outer part of the os calcis, from which it arises, and the four inner toes, into each of which it is inserted by a small flat tendon, which joins the corresponding tendon of the long common extensor.

The anterior tibial artery, L, Plate 67, Figure 2, extends from the upper part of the interosseous ligament which it perforates, to the bend of the ankle, whence it is continued over the dorsum of the foot. In the upper third of the leg, the anterior tibial artery lies deeply situated between the tibialis anticus, and flexor communis muscles. Here it will be found, close in front of the interosseous ligament, at about an inch and-a-half in depth from the anterior surface, and removed from the spine of the tibia at an interval equal to the width of the tibialis anticus muscle. In its course down the leg, the vessel pa.s.ses obliquely from a point close to the inner side of the neck of the fibula, to midway between the ankles. In its descent, it becomes gradually more superficial. In the middle of the leg, the vessel pa.s.ses between the extensor longus pollicis, and the tibialis anticus muscles. Above, beneath, and below the annular ligament, this artery will be found to pa.s.s midway between the extensor pollicis tendon, and those of the extensor communis, and to hold the same relation to these parts in traversing the dorsum of the foot, till it gains the interval between the two inner metatarsal bones, where it divides into two branches, one of which pa.s.ses forwards in the first interdigital s.p.a.ce, while the other sinks between the bones, to inosculate with the plantar arteries.

The innermost tendon of the short common extensor crosses in front of the dorsal artery of the foot near its termination. Between the ankle and the first interosseous s.p.a.ce the artery lies comparatively superficial, being here covered only by the skin and fascia and cellular membrane. Two veins accompany the anterior tibial artery and its continuation on the dorsum of the foot. The anterior tibial nerve, a branch of the peronaeal, joins the outer side of the artery, about the middle of the leg, and accompanies it closely in this position, till both have pa.s.sed beneath the annular ligament. On the dorsum of the foot the nerve will be found to the inner side of the artery.

The branches of the anterior tibial artery are articular and muscular.

From its upper end arises the recurrent branch which anastomoses in front of the knee with the articular branches of the popliteal artery.

Near the ankle, arise on either side of the vessel two malleolar branches, internal and external, the former communicating with branches of the posterior tibial, the latter with those of the peronaeal.

Numerous muscular branches arise, at short intervals, from the vessel in its pa.s.sage down the leg. Tarsal, metatarsal, and small digital branches spring from the dorsal artery of the foot. The anterior tibial artery is rarely found to deviate from its usual course; in some cases it appears of less or of greater size than usual. When this vessel appears deficient, its place is usually supplied by some branch of the peronaeal or posterior tibial, which pierces the interosseous ligament from behind.

The anterior tibial artery when requiring a ligature to be applied to it in any part of its course, may be exposed by an incision, extending for three or four inches, (more or less, according to the depth of the vessel) along the outer border of the tibialis anticus muscle. The fibrous septum between this muscle and the extensor communis, will serve as a guide to the vessel in the upper third of the leg, where it lies deeply on the interosseous ligament. In the middle of the leg, the vessel is to be sought for between the anterior tibial and extensor longus pollicis muscles. In the lower part of the leg, and on the dorsum of the foot, it will be found between the extensor longus pollicis, and extensor communis tendons, the former being taken as a guide for the incision. In pa.s.sing the ligature around this vessel at either of these situations, care is required to avoid including the venae comites and the accompanying nerve.

The sole of the foot is covered by a hard and thick integument, beneath which will be seen a large quant.i.ty of granulated adipose tissue so intersected by bands of fibrous structure as to form a firm, but elastic cushion, in the situations particularly of the heel and joints of the toes. On removing this structure, we expose the plantar fascia, B, Plate 68, Figure 1, extending from the os calcis, A, to the toes. This fascia is remarkably strong, especially its middle and outer parts, which serve to retain the arched form of the foot, and thereby to protect the plantar structures from superinc.u.mbent pressure during the erect posture. The superficial plantar muscles become exposed on removing the plantar fascia, to which they adhere. In the centre will be seen the thick fleshy flexor digitorum brevis muscle, B, arising from the inferior part of the os calcis, and pa.s.sing forwards to divide into four small tendons, b b b b, for the four outer toes. On the inner side of the foot appears the abductor pollicis, D, arising from the inner side of the os calcis and internal annular ligament, and pa.s.sing to be inserted with the flexor pollicis brevis, H, into the sesamoid bones and base of the first phalanx of the great toe. On the external border of the foot is situated the abductor minimi digiti, C, arising from the outer side of the os calcis, and pa.s.sing to be inserted with the flexor brevis minimi digiti into the base of the first phalanx of the little toe. When the flexor brevis digitorum muscle is removed, the plantar arteries, L M, and nerves, are brought partially into view; and by further dividing the abductor pollicis, D, their continuity with the posterior tibial artery and nerves, K L, Plate 67, Figure 1, behind the inner ankle may be seen.

The plantar branches of the posterior tibial artery are the internal and external, both of which are deeply placed between the superficial and deep plantar muscles. The internal plantar artery is much the smaller of the two. The external plantar artery, L, Plate 68, Figure 1, is large, and seems to be the proper continuation of the posterior tibial. It corresponds, in the foot, to the deep palmar arch in the hand. Placed at first between the origin of the abductor pollicis and the calcaneum, the external plantar artery pa.s.ses outwards between the short common flexor, B, and the flexor accessorius, E, to gain the inner borders of the muscles of the little toe; from this place it curves deeply inwards between the tendons of the long common flexor of the toes, F f f, and the tarso-metatarsal joints, to gain the outer side of the first metatarsal bone, H, Plate 68, Figure 2. In this course it is covered in its posterior half by the flexor brevis digitorum, and in its anterior half by this muscle, together with the tendons of the long flexor, F, Plate 68, Figure 1, of the toes and the lumbricales muscles, i i i i.

From the external plantar artery are derived the princ.i.p.al branches for supplying the structures in the sole of the foot. The internal plantar nerve divides into four branches, for the supply of the four inner toes, to which they pa.s.s between the superficial and deep flexors. The external plantar nerve, pa.s.sing along the inner side of the corresponding artery, sends branches to supply the outer toe and adjacent side of the next, and then pa.s.ses, with the artery, between the deep common flexor tendon and the metatarsus, to be distributed to the deep plantar muscles.

The posterior tibial artery may be tied behind the inner ankle, on being laid bare in the following way:--A curved incision (the concavity forwards) of two inches in length, is to be made midway between the tendo Achillis and the ankle. The skin and superficial fascia having been divided, we expose the inner annular ligament, which will be found enclosing the vessels and nerve in a ca.n.a.l distinct from that of the tendons. Their fibrous sheath having been slit open, the artery will be seen between the venae comites, and with the nerve, in general, behind it.

When any of the arteries of the leg or the foot are wounded, and the haemorrhage cannot be commanded by compression, it will be necessary to search for the divided ends of the vessel in the wound, and to apply a ligature to both. The expediency of this measure must become fully apparent when we consider the frequent anastomoses existing between the collateral branches of the crural arteries, and that a ligature applied to any one of these above the seat of injury will not arrest the recurrent circulation through the vessels of the foot.

DESCRIPTION OF PLATES 67 & 68.

PLATE 67.

FIGURE 1.

A. The tendon of the tibialis anticus muscle.