Sole of foot

Question 1

Outline the plantar aponeurosis.

Answer 1

• The plantar aponeurosis (fascia) is composed of dense collagen fibres arranged mainly longitudinally.
• It arises posteriorly from the medial process of the calcaneus and fans out over the sole.
• It divides into five bands, one for each toe.
• Just distal to the metatarsal heads, these bands are connected by transverse fibres, the superficial transverse metatarsal ligament.
• The digital slips bifurcate for the passage of the flexor tendons and are inserted around the edges of the fibrous flexor sheaths and into the deep transverse metatarsal ligaments that unite the plantar ligaments of adjacent metatarsophalangeal joints. * From each edge of the plantar aponeurosis a septum penetrates the sole, separating the flexor digitorum brevis from the abductors of big and little toes.
• The septa are attached to the first and fifth metatarsal bones.
• The abductors of the big and little toes, lying along the margins of the sole, are covered by deep fascia that is much thinner than the central plantar aponeurosis.

Question 2

Outline the muscle groups of the toe.

Answer 2

• The muscles of the sole are arranged in four layers. * The superficial layer consists of three short muscles that cover the sole, beneath the plantar aponeurosis.
• The second layer consists of long tendons to the digits, and their connections.
• The third layer consists of the short muscles of the great and little toes; it is confined to the metatarsal region of the foot.
• The fourth layer consists of both plantar and dorsal interossei and it includes also the tendons of peroneus longus and tibialis posterior.
• The segmental nerve supply of all the muscles is essentially S2.

Question 3

What are the 3 muscles of the first layer of the sole?

Answer 3

• Flexor digitorum brevis
• Abductor hallucis
• Abductor digiti minimi

Question 4

Flexor digitorum brevis:
* Origin
* Insertion
* Nerve supply
* Action

Answer 4

• Origin - medial process of the calcaneus and the deep surface of the central part of the plantar aponeurosis.
• Insertion - divides into 4 tendons which pass to the lateral 4 toes. Inserts into the side of the middle phalanx.
• Nerve supply - medial plantar nerve.
• Action - Flex toes with equal effect in any position of the ankle joint.

Question 5

Abductor hallucis:
* Origin
* Insertion
* Nerve supply
* Action

Answer 5

• Origin - medial process of the calcaneus and from the flexor retinaculum.
• Insertion - medial side of the base of the proximal phalanx of the great toe.
• Nerve supply - medial plantar nerve.
• Action - abducts the great toe.

Question 6

Abductor digiti minimi:
* Origin
* Insertion
* Nerve supply
* Action

Answer 6

• Origin - the medial and lateral processes of the calcaneus, deep to the origin of flexor digitorum brevis.
• Insertion - lateral base of the proximal phalanx of the 5th toe and the tubercle of the 5th metatarsal bone.
• Nerve supply - branch from the main trunk of the lateral plantar nerve.
• Action - abducts the little toe.

Question 7

What are the components of the second layer of the sole?

Answer 7

• Tendon of flexor hallucis longus
• Tendon of flexor digitorum longus
• Flexor accesorius (quadratus plantae)
• Lumbricals

Consists of the long flexor tendons and their connection in the sole.

Question 8

Flexor accesorius (quadratus plantae):
* Origin
* Insertion
* Nerve supply
* Action

Answer 8

• Origin - arises by a large medial head from the medial surface of the calcaneus and by a small lateral head that arises from the lateral border of the plantar surface of the calcaneus.
• Insertion - into the tendon of flexor digitorum longus as it subdivides into tendons for the digits.
• Nerve supply - by the main trunk of the lateral plantar nerve.
• Action - by pulling on the tendons of flexor digitorum longus, it provides a means of flexing the lateral 4 toes in any position of the ankle joint. It also straightens the pull of the long flexor tendons on the toes.

Question 9

Lumbricals:
* Origin
* Insertion
* Nerve supply
* Action

Answer 9

• Origin - arise from the tendons of flexor digitorum longus and pass forward on the medial (big toe) sides of the metatarsophalangeal joints of the lateral 4 toes.
• Insertion - Their tendons lie on the plantar surfaces of the deep transverse ligament of the metatarsal heads and pass dorsally to be inserted into the extensor expansions.
• Nerve supply - as in the hand, a lumbrical supplied by the medial plantar (cf. median) nerve is unicipital; one supplied by the lateral plantar (cf. ulnar) nerve is bicipital. In the foot, only the 1st lumbrical is supplied by the medial plantar nerve; it arises by a single head from its own tendon.
  The lateral 3 lumbricals are supplied by the lateral plantar nerve (deep branch) and each arises by 2 heads from the adjoining sides of the tendon.
• Action - maintain extension of the digits at the interphalangeal joints while the flexor digitorum longus tendons are flexing the toes, so that in walking and running, the toes do not buckle under.

Question 10

What are the 3 muscles of the third layer of the sole.

Answer 10

• Flexor hallucis brevis
• Adductor hallucis
• Flexor digiti minimi brevis

Question 11

Flexor hallucis brevis:
* Origin
* Insertion
* Nerve supply
* Action

Answer 11

• Origin - cuboid, the lateral cuneiform and the tendon of tibialis posterior.
• Insertion - the belly of the muscle splits into 2 parts which are inserted, each by way of a sesamoid bone, into the medial and lateral sides of the base of the plantar surface of the proximal phalanx of the great toe.
  The medial insertion blends with that of abductor hallucis, the lateral with that of adductor hallucis.
• Nerve supply - medial plantar nerve.
• Action - flex the proximal phalanx of the big toe.

Question 12

Adductor hallucis:
* Origin
* Insertion
* Nerve supply
* Action

Answer 12

• Origin - Large oblique head - arises anterior to flexor hallucis brevis, from the long plantar ligament where it roofs over the peroneus longus tendon, and from the bases of the 2nd, 3rd and 4th metatarsal bones.
  Slender transverse head - no bony origin, it arises from the deep transverse ligament and from the plantar ligaments of the lateral 4 MTPJ.
• Insertion - The 2 heads unite in a short tendon which is inserted with the latera insertion of flexor hallucis brevis into the lateral side of the plantar surface of the base of the proximal phalanx of the big toe.
• Nerve supply - deep branch of the lateral plantar nerve.
• Action - draws the big toe towards the axis of the metatarsus and assists in maintaining the transverse arch.

Question 13

Flexor digiti minimi brevis:
* Origin
* Insertion
* Nerve supply
* Action

Answer 13

• Origin - base of the 5th metatarsal bone and the adjoining fibrous sheath of peroneus longus.
• Insertion - base of the proximal phalanx medial to insertion of abductor digiti minimi.
• Nerve supply - superficial branch of the lateral plantar nerve.
• Action - assist in flexing the little toe.

Question 14

What are the components of the fourth layer of the sole?

Answer 14

The fourth layer of muscles consists of the interossei in the intermetatarsal spaces. The tendons of tibialis posterior and peroneus longus, lying deeply against the undersurface of the tarsus, are conveniently included in this layer.