The foot must be arranged with the Plantar surface uppermost. In an entire body this will best be done by turning- the subject on the face, flexing the knee, and supporting the leg with blocks.
1. Along the median line of the foot from the Os Calcis to the root of the third toe.
2. Transverse incisions from the anterior and posterior ends of this, to the inner and outer borders of the foot and heel respectively. Reflect the flaps inwards and outwards, and expose the superficial fascia. Clear it away, dissecting out at the same time—
1. The Superficial Transverse ligament, across the roots of the toes in the rudimentary web of the foot.
2. The Lumbricales muscles, with the Digital vessels and nerves in the intervals of the Plantar fascia.
3. The Plantar Cutaneous branches of the Posterior Tibial artery, vein, and nerve, in the hollow of the heel.
4. At short distances from the inner and outer borders of the foot along the furrows of the internal and external intermuscular septa, some small unnamed arteries and nerves derived from the Internal and External Plantar, respectively.
5. At the clefts of the toes, the Digital vessels and nerves will be found issuing from between the processes of the Plantar fascia and passing beneath the Superficial Transverse ligament; those to the inner side of the first and the outer side of the fifth toes, however, perforate further back than the rest. The origin of these vessels and nerves is not now traceable.
6. When the superficial fascia or fat is completely removed, the preceding vessels and nerves will be displayed, and the Plantar fascia. This will be found to be made up of three portions: a central, thick and triangular, with its apex at the heel, and its base cut into five processes, one for each toe; and two lateral portions which are thin and unimportant, except that there is a strong process on the outer side between the Os Calcis and the base of the fifth Metatarsal bone.
Remove now the Plantar fascia, by a longitudinal incision along the median line, and a transverse one at the Os Calcis. Reflect it forwards ; in doing this two septal processes, one on each side of the Flexor brevis digitorum muscle, will be found. The Digital vessels and nerves and the Lumbricales muscles are to be preserved, the rest of the above-mentioned structures will be removed. There will now be displayed—
1. The Abductor pollicis muscle, along the inner border of the foot.
2. The Flexor brevis digitorum muscle, along the centre of the foot. It is found to be giving off four tendons, one to each of the four outer toes, these are seen entering their corresponding sheaths, which reach for a short distance into the foot.
3. The Lumbricales muscles are seen in the intervals of the tendons of the Flexor brevis digitorum muscle. The innermost one is on the Tibial side of the tendon to the first toe, the others are in the intervals of the tendons; they pass to the Tibial side of the first Phalanges.
4. The Abductor minimi digiti muscle, along the outer border of the foot.
5. The tendon of the Plexor longus pollicis muscle in part, on the outer side of the Abductor pollicis muscle.
6. Small portions of the insertions of the Flexor brevis pollicis muscle, into the inner and outer sides of the base of the Metatarsal Phalanx of the great toe.
7. A small part of the Flexor brevis minimi digiti muscle at its insertion into the first Phalanx, lying on the inner side of the Abductor minimi digiti muscle.
8. The Internal Plantar artery and vein, in the anterior part of its course emerging from beneath the Abductor pollicis. Different accounts of the ending of this artery are given. According to Gray and Quain, it terminates by running along the inner side of the great toe. Ellis's description is that it gives off four branches, the innermost of which runs to the inner side of the great toe, the outer three dip down in the first, second, and third interosseous spaces to join the Digital branches of the Deep Plantar arch. I believe that both accounts are true in different cases.
9. The External Plantar artery and vein, in a small part of their course. They are seen at the anterior and outer part of the foot, between the Abductor minimi digiti muscle and the outer border of the Flexor brevis digitorum muscle. The branch to the outer surface of the little toe is visible.
10. The Internal Plantar nerve, emerging with the corresponding artery from beneath the Abductor pollicis, and dividing in front into four Digital branches which lie upon the tendons of the Flexor brevis digitorum, one undivided for the inner side of the great toe, the others bifurcating at the clefts of the toes to supply the contiguous sides of the first and second, second and third, and third and fourth. In this dissection they are only seen as far as the bifurcation. By separating the Abductor pollicis from the Flexor brevis digitorum posteriorly, branches may be traced from the trunk of the Internal Plantar nerve to these muscles. The innermost Digital offset will be found supplying the Flexor brevis pollicis muscle, the next two the two innermost Lumbricales muscles, and the outermost communicates with the inner of the two Digital branches from the Superficial division of the External Plantar nerve.
11. The Superficial branch of the External Plantar nerve, appearing between the Abductor minimi digiti and the Flexor brevis digitorum muscles, a little anterior to the base of the fifth Metatarsal bone. It is seen dividing into two Digital branches, one undivided for the outer side of the little toe, the other bifurcated for the contiguous sides of this toe and the next.