Topographical anatomy of the foot

Layered structure of the dorsum of the foot

The skin of the dorsal surface of the foot is thin and highly mobile. Beneath it lies loose subcutaneous tissue, which is practically devoid of dense adipose tissue, making it a frequent and easy site for edematous fluid accumulation.

A robust vascular network forms in the subcutaneous layer. Distally, the dorsal venous arch (arcus venosus dorsalis pedis) is located, collecting blood from the intermetatarsal spaces and anastomosing with the dorsal venous network. Outflow from the arch proceeds via two main trunks:

• Small saphenous vein (v. saphena parva) runs along the lateral margin of the foot.
• Great saphenous vein (v. saphena magna) passes to the anterior surface of the medial malleolus.

Deeper than the superficial veins lie the nerves providing skin sensation. The medial margin of the foot up to its midpoint is innervated by the saphenous nerve (n. saphenus), while the lateral margin and the fifth toe are innervated by the sural nerve (n. suralis). The main surface of the dorsum is supplied by branches of the superficial fibular nerve (n. fibularis superficialis), which gives off the medial and intermediate dorsal cutaneous nerves. An exception is the first interdigital space, which is supplied by the deep fibular nerve (n. fibularis profundus).

Structure and fascial spaces of the sole

Unlike the dorsum, the skin of the sole is thickened and relatively immobile, especially in areas of highest load: the calcaneal tuberosity, the heads of the metatarsal bones, and along the lateral margin. Connective tissue septa firmly attach it to the underlying plantar aponeurosis. The subcutaneous tissue here has a pronounced cellular structure, is dense, and in the region of the joints or heel can reach a thickness of 1.0–1.5 cm. On the plantar surface of the toes, the subcutaneous tissue is also well developed and forms characteristic "pads".

Important fascial spaces are formed between the muscle layers of the sole:

1. Superficial fascial space is located between the first and second muscle layers. It is here that the lateral and medial neurovascular bundles pass from the calcaneal canal to the metatarsus.
2. Deep fascial space is situated deeper, separating the second and third muscle layers.

The projection of the neurovascular bundles onto the skin has clear landmarks. The medial bundle is projected along a line from the midpoint of the inner half of the sole to the first interdigital space. The lateral bundle runs from the midpoint of the width of the sole to the fourth interdigital space.

Topography of muscles and tendons

The muscular apparatus and tendons form complex syntopic relationships. Of particular note is the tendon of the flexor hallucis longus (m. flexor hallucis longus). In the medial retromalleolar region, it lies most deeply and posteriorly. Moving distally, it crosses the tendon of the flexor digitorum longus (m. flexor digitorum longus), and emerges anteriorly at the medial margin of the sole. Its synovial sheath descends lower than the sheaths of adjacent muscles and may communicate with the ankle joint cavity via a weak spot in the posterior capsule.

In the metatarsal region, the layers are arranged as follows (from the plantar aponeurosis inwards):

• Tendons of the flexor digitorum brevis (m. flexor digitorum brevis).
• Tendon of the flexor digitorum longus, dividing into slips to the toes. From these slips originate the lumbrical muscles (mm. lumbricales), which pass dorsally to the dorsal aponeurosis of digits II–V.
• Deepest of all lie the oblique and transverse heads of the adductor hallucis muscle (m. adductor hallucis).

At the tarsal level, the fourth layer forms the tendon of the fibularis longus muscle (m. fibularis longus), which is enclosed within the fibers of the long plantar ligament (lig. plantare longum) and passes toward the medial cuneiform and the base of the first metatarsal bone.

Surgical anatomy of the Lisfranc joint

The tarsometatarsal joints (artt. tarsometatarsales), or Lisfranc's joint, connect the bones of the second row of the tarsus (the three cuneiforms and the cuboid) with the metatarsal bones. The joint is reinforced by dorsal and plantar ligaments.

In operative surgery, the medial interosseous cuneometatarsal ligament (lig. cuneometatarsalia interossea mediale), stretched between the medial cuneiform bone and the base of the second metatarsal bone, is of critical importance. This ligament is known as the "key of the Lisfranc joint". Only after its complete transection does the joint space open widely, allowing unhindered disarticulation of the distal foot.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Detailed course of the medial and lateral plantar nerves
• Syntopy of flexor tendons in the region of the medial malleolus
• Structure and functions of the long plantar ligament
• Topography of the metatarsophalangeal joints
• Anatomical prerequisites for the spread of purulent processes in the foot

Other topics in the "Lower Limb" section

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