Foot

The Foot

Overview of Foot Anatomy

• The foot is divided into several important aspects including the plantar and dorsal sides, each with unique features.

Plantar Aspect

General Orientation

• The plantar aspect is the underside of the foot, also referred to as the ventral or posterior aspect, and the dorsal aspect is the upper side, referred to as the dorsal or anterior aspect.

Cutaneous Distribution

Dorsum of the Foot

• L5, S1, L4 nerve roots are significant in the cutaneous distribution of the dorsum of the foot:

  1. Saphenous nerve: Supplies sensation to the skin on the medial side.

  2. Superficial fibular nerve: Provides sensory innervation to the dorsum of the foot.

  3. Deep fibular nerve: Supplies the skin between the first and second toes.

  4. Dorsal lateral cutaneous nerve: A branch of the sural nerve that helps innervate the foot’s lateral part.

Plantar Aspect

• L5, S1 roots are crucial for the plantar aspect sensory distribution:

  1. Saphenous nerve: Medial plantar surface innervation.

  2. Medial plantar nerve: Supplies the medial side of the foot.

  3. Lateral plantar nerve: Supplies the lateral side of the foot.

  4. Dorsal lateral cutaneous nerve: Innervates the lateral side.

  5. Calcaneal branches of the tibial and sural nerves: Contribute to heel sensation.

Deep Fascia of the Foot

Description

• The deep fascia encloses muscles and tendons, providing structure and support.

• Major components include:

  • Extensor retinacula: Stabilize tendons of the extensor muscles.

  • Superficial fibular and inferior fibular retinacula: Support fibular tendons.

  • Plantar aponeurosis: A thick band of tissue on the plantar aspect, protecting underlying structures.

Muscle Layers in the Plantar Aspect

Layer 1

1. Abductor hallucis

2. Flexor digitorum brevis

3. Abductor digiti minimi

4. Quadratus Plantae

5. Lumbricals

6. Flexor hallucis brevis

7. Adductor hallucis

8. Flexor digiti minimi

• PAD (3) and DAB (4) represent the actions of muscles on toes: PAD (plantar adduction) and DAB (dorsal abduction).

Vascular Plane

• Contains the lateral and medial plantar nerves and arteries.

• Essential vessels include the plantar arch and branches.

Innervation & Spinal Levels

• Medial plantar nerve:

  • Supplies:

    • Abductor hallucis

    • Flexor digitorum brevis

    • Flexor hallucis brevis

  • Spinal levels: S2, S3 (except flexor hallucis brevis: S1, S2).

Specific Muscles Descriptions

Abductor Digiti Minimi

• Origin: Medial/lateral processes of the calcaneal tuberosity, plantar aponeurosis.

• Insertion: Lateral side of the proximal phalanx of the little toe.

• Innervation: Lateral plantar nerve.

• Actions: Abducts and flexes the little toe.

• Spinal levels: S2, S3

Abductor Hallucis

• Origin: Flexor retinaculum, medial calcaneal tuberosity; plantar aponeurosis.

• Insertion: Medial side of the proximal phalanx of the great toe.

• Innervation: Medial plantar nerve.

• Actions: Abducts and flexes the hallux, maintains medial longitudinal arch.

• Spinal levels: S2, S3

Flexor Digitorum Brevis

• Origin: Medial/lateral processes of the calcaneal tuberosity, plantar aponeurosis.

• Innervation: Medial plantar nerve.

• Actions: Flexes the lateral four toes.

• Spinal levels: S2, S3

Superficial Vascular Layer

• Comprised of the following:

  • Medial and lateral plantar nerves and arteries.

  • Common and proper plantar digital nerves.

Neurovascular Plane

• Found between the 1st and 2nd layers of muscles in the plantar aspect.

Second Layer

• Muscles: Lumbricals and Quadratus Plantae.

Quadratus Plantae

• Origin: Plantar surface of the calcaneus, long plantar ligament.

• Insertion: Flexor digitorum longus tendon.

• Innervation: Lateral plantar nerve.

• Action: Realigns the flexor digitorum longus to assist in foot function.

• Spinal levels: S2, S3

Lumbricals

• Origin: Tendons of the flexor digitorum longus.

• Insertion: Dorsal digital expansions.

• Innervation:

  • 1st: medial plantar nerve.

  • 2nd-4th: lateral plantar nerve.

• Action: Flex metatarsophalangeal joint; extend interphalangeal joints.

• Spinal levels: S2, S3

Third Layer

• Muscles: Adductor hallucis, Flexor hallucis brevis, Flexor digiti minimi (brevis).

Adductor Hallucis

• Origin:

  • Transverse head: from plantar metatarsophalangeal ligaments of 3rd-5th toes; deep transverse metatarsal ligament.

  • Oblique head: from bases of 2nd-4th metatarsals and surrounding tissue of fibularis longus.

• Insertion: Common tendon onto the base of the proximal phalanx of the hallux.

• Innervation: Lateral plantar nerve.

• Action: Adducts the hallux, can flex the hallux.

• Spinal levels: S2, S3

Flexor Hallucis Brevis

• Origin: Plantar surface of the cuboid, lateral cuneiform, tendon of tibialis posterior.

• Insertion: Sides of the base of the proximal phalanx of the hallux.

• Innervation: Medial plantar nerve.

• Action: Flexes metatarsophalangeal joint of the great toe.

• Spinal levels: S1, S2

Flexor Digiti Minimi

• Origin: Base of the 5th metatarsal, tendon of tibialis posterior.

• Insertion: Lateral side of the base of the proximal phalanx of the little toe.

• Innervation: Lateral plantar nerve.

• Action: Flexes metatarsophalangeal joint of the little toe.

• Spinal levels: S2, S3

Deep Vascular Layer

• Contains the plantar arch, superficial branch, deep plantar artery, and all key components of plantar muscles including:

  • Adductor hallucis

  • Quadratus plantae

  • Flexor digitorum brevis

Fourth Layer

Muscles

• Adductor muscle:

  • Origin: Each by 2 heads from adjacent sides of metatarsals.

  • Insertion: Dorsal digital expansions of the 2nd-4th toes.

  • Innervation: Lateral plantar nerve.

  • Action: Adducts the 3rd-4th toes; assists lumbricals.

  • Spinal levels: S2, S3

Interossei Muscles

• Origin: Two heads from adjacent sides of metatarsals.

• Insertion: Dorsal digital expansions of the 2nd-4th toes.

• Innervation: Lateral plantar nerve.

• Action: Abducts the 2nd-4th toes; assists lumbricals.

• Spinal Levels: S2, S3

Vascular System of the Foot

• Arteries: Includes medial plantar, lateral plantar, posterior tibial, and common & proper plantar digital arteries.

Dorsum of the Foot

• Muscles:

  1. Extensor hallucis brevis

     • Origin: Dorsal aspect of the calcaneus.

     • Insertion: To the base of the proximal phalanx of the great toe.

  2. Extensor digitorum brevis

     • Origin: Dorsal and lateral aspect of the calcaneus.

     • Insertion: Lateral side of tendons of the extensor digitorum longus for toes 2-4.

  • Innervation: Deep fibular nerve.

  • Spinal levels: L5, S1.

Structures in the Dorsum

• Key components: Superficial fibular nerve, Deep fibular nerve, branches from the dorsal venous arch, Saphenous nerve, and dorsal digital nerves.

Arteries in the Dorsum

• Key arteries include anterior tibial artery, lateral and medial malleolar arteries, dorsalis pedis artery, and deep plantar artery.

Arches of the Foot

Medial Longitudinal Arch

• Formed by the calcaneus, navicular, three cuneiforms, and three medial metatarsals.

Lateral Longitudinal Arch

• Composed of the calcaneus, cuboid, and lateral two metatarsals.

Transverse Arch

• Runs side to side across the foot, involving the cuboid and three cuneiforms.