Applied Surgical Anatomy of the FootOverview
Surgery of the foot often is undertaken to correct bony abnormalities. All the bones of the foot can be approached dorsally; dorsal approaches usually are better than plantar approaches for two major reasons:
The critical neurovascular structures in the forepart of the foot all are on the plantar side of the metatarsal bones, so they remain protected.
Dorsal incisions avoid cutting through the specialized weight-bearing skin of the sole of the foot.
In pathologic situations in which abnormal skin lies over bones that protrude (e.g., metatarsalgia), a plantar approach may have to be used and the abnormal skin excised.
Although the dorsal anatomy is the critical surgical anatomy of the foot, the plantar anatomy includes its key neurovascular structures. Knowledge of the latter allows the surgeon to explore wounds in the sole of the foot, which do not mimic any described surgical approach. For these reasons, the anatomy of the sole of the foot also is described in the following section.
Anatomy of the Dorsum of the Foot
The skin of the dorsum of the foot is comparatively thin and loose. Distally, the lines of cleavage (also called relaxed skin tension lines, especially by plastic and aesthetic surgeons) run roughly transversely. The loose skin, which facilitates retraction, accounts for the enormous amount of dorsal swelling that can occur after foot trauma.
Nerve Supply
Branches of three cutaneous nerves run right under the skin of the dorsum of the foot: the medial side houses the branches of the saphenous nerve; most of the dorsum of the foot is supplied by the dorsal cutaneous branches of the superficial peroneal nerve; and the lateral side of the foot is supplied by the sural nerve.
The first web space is supplied by branches of the deep peroneal nerve. Numbness in the first web space is the earliest sign of a deep peroneal nerve lesion in the anterior compartment of the leg (see Figs. 25-5, 36-1, 45-2, and 46-1).
Superficial Veins
The veins are arranged in a dorsal venous arch. The medial side drains into the long saphenous vein; the lateral side drains into the short saphenous vein. Superficial veins, of course, must be on the dorsum of the foot, because they would collapse under the force of ordinary weight bearing if they were on the sole.
Tendons
Two sets of tendons lie immediately deep to the cutaneous nerves: those of the extensor digitorum longus and extensor digitorum brevis muscles and those of the extensor hallucis longus and extensor hallucis brevis muscles. The extensor digitorum tendons insert into the dorsal extensor expansion of the lateral four toes, an arrangement that is identical to that in the fingers. Frequently, these tendons cross-communicate in the forepart of the foot. The great toe, similar to the thumb, has no dorsal extensor expansion (see Fig. 25-5).
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