Anatomy of Foot in a Nutshell

Anatomy of Foot

Intro: Foot print should not be flat

• There are arches associated with the foot that are formed and maintained by muscles and ligaments
• Someone with fallen arches will leave a full flat imprint, means the structure has been compromised.
• Newborn children have a flat footprint because of a developed fat pad that gives the appearance of a flat foot
• Inversion/eversion occurs in the joint (subtalar joint) between Talus and calcaneous, NOT at the ankle.

Skin:

• skin on the plantar surface of the foot is very thick
• there is callous formation on certain areas, especially contact points
• may have 2 cm of callus / skin before encounter first muscle
• between skin and muscle layer, have connective tissue (subcutaneous) which is arranged in bands that connect dermis of skin with deep fascia.
  • Create little compartments / clefts that are filled with fat lobules.
  • These fat filled fibrous compartments are shock absorbers

(514) Plantar surface

• Will encounter thick band of deep fascia from calcaneous
  • Called plantar aponeurosis
  • As it radiates toward toes, it breaks up into fibrous bands that extend to each toe and merge with tendons in that area.
• Along medial / lateral edge of plantar aponeurosis, have extensions that divide foot into medial, intermediate, and lateral compartments
  • These extensions will go deep to attach bone
  • Will restrict infection to only one compartment
  • We don’t really use compartments, we use layers (superficial to deep)
• 4 layers of muscles beneath aponeurosis

First layer: (515)

• Muscles in the foot really are only for holding together the arches and maintaining integrity of the foot rather than work for individual motion.
• 3 Muscles

1. • Abductor Hallucis

1. 1. • Associated with great toe
      • From calcaneous, forms tendon that attaches to great toe

• • • Ties two ends of medial arch together

1. • Abductor digiti minimi

1. 1. • From calcaneous to the little toe
      • Helps maintain lateral arch of the foot

1. • Flexor digitorum brevis

1. 1. • Most prominent of the 3 muscles
      • Has tendons superficial to those of flexor digitorum longus which blend in to them (may fuse or go separately).

Second layer: 516

• 2 Tendons
  • Hallucis longus tendon

• • • Attaches distal phalanx of great toe
    • Long flexor of great toe

1. • Flexor digitorum longus

1. 1. • Enters surface as single structure
      • Divides into 4 slips onto each toe

• Muscles
  • Quadratus Plantae

• • • From calcaneous
    • Inserts onto tendon of flexor digitorum longus (right before 4 way split)
      1. Puts action of flexor into longitudinal plane as opposed to an oblique plane
      2. Needs to attach because the tendon must be held in place to avoid inversion while flexing (because tendon is in oblique plane).

1. • 4 Lumbricals

1. 1. • origin from adjacent sides of flexor digitorum longus tendons
      • inserts on the dorsal surface of the toe on the extensor hood formed by extensor tendon.

• • • Extends interphalangeal joint.

• • • Allows grip by toes on the floor- would normally curl due to forceful nature of flexor digitorum muscles.

• Neurovascular structures appear medially

• • Crossing ankle on medial side (posterior to medial malleolus) is the tibial nerve and posterior tibial artery

• • • They both split into terminal branches.
      1. Each give medial branch- medial plantar artery / nerve
      2. Each give lateral branch- lateral plantar artery / nerve
    • Split occurs just posterior to medial malleolus or as they come into the plantar surface (varies)

1. • Medial plantar nerve supplies 3 ½ toes
   • Lateral plantar nerve gets other 1 ½ toes

Third layer (517)

• 3 muscles
  • Flexor Hallucis brevis

• • • From cuboid bone / other tarsal bones
    • As approaches big toe, it splits into 2 tendons that cross metatarsal / proximal phalanx.
      1. Each tendon associated with each of the 2 sesamoid bones on the “ball of the foot”
      2. sesamoid bones are bones within tendons (within tendon of flexor hallucis brevis)
      3. tendon of flexor hallucis longus passes between the two sesamoid bones

• Flexor Digitimini brevis

1. • Origin from metatarsals
   • Inserts on proximal phalanx of little toe, weak flexor.

• Adductor Hallucis

• • Has 2 heads
    • oblique head (larger) has origin from cuboid
    • transverse head has origin from heads of 4 lateral metatarsals
  • 2 heads unite to insert proximal phalanx of great toe

• • adducts the big toe and ties metatarsals together in weight bearing
    • especially true of transverse head
    • needed to avoid spreading of metatarsals in weight bearing
    • Note: reference point for adduction / abduction in the foot is the second toe.

Fourth layer

• Lateral plantar artery
  • Passes deep to adductor hallucis to form plantar arch

1. 1. • Gives off plantar metatarsal arteries which divide into plantar digital arteries
      • Between first and second toes, the arch sends communication between the metatarsals

• • • This communication is continuous with deep plantar artery from dorsal surface

• Tendons
  • First metatarsal has tuberosity: attachment for

1. 1. • Fibularis Tertias
      • Fibularis Brevis

1. • Fibularis longus

1. 1. • Tendon parts with that of fibularis Brevis
      • Continues deep across plantar surface of foot

• • • Passes deep to long plantar ligament

• • • Attaches base of first metatarsal and median cuneiform bone
    • Thus, it courses lateral to medial for insertion. The pull of this tendon is very effective for eversion.

1. • Tibialis muscles

• • • Tibialis Anterior goes onto dorsum of foot from anterior compartment
      1. Attaches to the first metatarsal / medial cuneiform
      2. Same point as Fibularis longus, but have opposite action
      3. Is for inversion of the foot
  • Tibialis posterior
    • Crosses medial malleolus
    • Most of attachment is on navicular bone tuberosity
    • Sends slips to most other tarsal bones (except calcaneous) and middle 3 metatarsals.
    • Is a muscle for inversion

• Muscles: Interossei
  • Interosseus muscles are on both plantar / dorsal surfaces
  • PAD and DAB still apply (Plantar surface adduct / Dorsal surface abduct)
  • Great toe has it’s own adductor
  • Plantar Interosseus (3)

1. 1. • Toes 3,4,5 need adductor to move toward 2^nd toe
      • On medial side, have plantar interosseus

• • • Thus, have 3 plantar interosseus musles

1. 1. • Take origin from one metatarsal apiece and are thus unipennate

1. • Dorsal Interosseus muscles (4)

1. 1. • Great toe / little toe have their own Abductors
      • Toe 3,4,2 need muscles

• • • 4 dorsal interosseus
      1. One on each side of toe 2
      2. One on lateral side of toes 3,4

1. • These take origin from adjacent sides of metatarsals and are thus bipennate

• Innervation
  • Medial plantar nerve

• • • Broader sensory innervation
    • Less motor innervation
      1. Flexor Hallucis Brevis
      2. Abductor Hallucis
      3. Flexor Digitorum Brevis
      4. #1 Lumbrical

1. • Lateral plantar nerve innervates other muscles

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