Part 67

The sole of the foot is covered by a hard and thick integument, beneath which will be seen a large quantity 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 superincumbent 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 passing 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 passing 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 passing 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 passes 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 principal 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 pass between the superficial and deep flexors. The external plantar nerve, passing along the inner side of the corresponding artery, sends branches to supply the outer toe and adjacent side of the next, and then passes, 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 canal 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.

B B. The long saphena vein.

C C. The tendon of the tibialis posticus muscle.

D. The tibia; d, the inner malleolus.

E E. The tendon of the flexor longus digitorum muscle.

F. The gastrocnemius muscle; f, the tendo Achillis.

G. The soleus muscle.

H. The tendon of the plantaris muscle.

I I. The venae comites.

K K. The posterior tibial artery.

L L. The posterior tibial nerve.

FIGURE 2.

A. The tibialis anticus muscle; a, its tendon.

B. The extensor longus digitorum muscle; b b b b, its four tendons.

C C. The extensor longus pollicis muscle.

D D. The tibia.

E. The fibula; e, the outer malleolus.

F F. The tendon of the peronaeus longus muscle.

G G. The peronaeus brevis muscle; i, the peronaeus tertius.

H H. The fascia.

K. The extensor brevis digitorum muscle; k k, its tendons.

L L. The anterior tibial artery and nerve descending to the dorsum of the foot.