Foot ANA 208 FOOT Ankle the narrowest and

Foot ANA 208

FOOT • Ankle: the narrowest and malleolar parts of the distal leg, proximal to the dorsum and heel of the foot, including the ankle joint. • Foot provides a platform for supporting the body when standing and has an important role in locomotion. • Skeleton of the foot consists of 7 tarsals, 5 metatarsals, and 14 phalanges. • Three anatomical and functional zones: - Hindfoot: talus and calcaneus. - Midfoot: navicular, cuboid, and cuneiforms. - Forefoot: metatarsals and phalanges. The part/region of the foot contacting the floor or ground is the sole. • Part superiorly is the dorsum of the foot or dorsal region of the foot. • Sole of the foot underlying the calcaneus is the heel, and the sole underlying the heads of the medial two metatarsals is the ball of the foot. • Great toe (L. hallux) is also the 1 st toe (digit of foot, and the little toe (L. digitus minimus) is also the 5 th toe. 2

SKIN AND SUBCUTANEOUS TISSUE • Skin of the dorsum of the foot is much thinner and less sensitive than skin on most of the sole. • Skin over the major weight-bearing areas of the sole —the heel is thick. • Fibrous septa—divide this tissue into fat-filled areas, making it a shock-absorbing pad, especially over the heel. • Skin ligaments anchor the skin to the plantar aponeurosis. • Skin of the sole is hairless and sweat glands are numerous 3

DEEP FASCIA OF FOOT • Deep fascia of the dorsum of the foot is thin where it is continuous proximally with the inferior extensor retinaculum. • Deep fascia is continuous with the plantar fascia which has a thick central part and weaker medial and lateral parts. • The thick, central part of the plantar fascia forms the strong plantar aponeurosis, which invests the central plantar muscles. • Plantar fascia holds the parts of the foot together, helps protect the sole from injury and to support the longitudinal arches of the foot. • Longitudinal bundles of the aponeurosis divide into five bands that become continuous with the fibrous digital sheaths that enclose the flexor tendons that pass to the toes. • At the anterior end of the sole, the aponeurosis is reinforced by transverse fibers forming the superficial transverse metatarsal ligament. 4

• In the midfoot and forefoot, vertical intermuscular septa forms the three compartments of the sole: • Medial compartment of the sole: contains the abductor hallucis, flexor hallucis brevis, the tendon of the flexor hallucis longus, and the medial plantar nerve and vessels. • Central compartment of the sole: contains the flexor digitorum brevis, the tendons of the flexor hallucis longus and flexor digitorum longus, quadratus plantae and lumbricals, and the adductor hallucis. The lateral plantar nerve. • Lateral compartment of the sole: contains the abductor and flexor digiti minimi brevis. 5

• Forefoot contains a fourth compartment interosseous compartment of the foot. - Contains the metatarsals, dorsal and plantar interosseous muscles, deep plantar and metatarsal vessels. • A fifth compartment, the dorsal compartment of the foot: contains extensors hallucis brevis and extensor digitorum brevis and neurovascular structures of the dorsum of the foot. 6

Muscles of Foot • 20 individual muscles of the foot: - 14: plantar aspect - 2: dorsal aspect • 4 - intermediate. • Muscles of the sole arranged in four layers within four compartments. • Plantar muscles function as a group during the support phase of stance, maintaining the arches of the foot. - They resist forces that tend to reduce the longitudinal arch as weight is received at 7

• The muscles of the foot are of little importance individually. Note that the: • Plantar interossei ADduct (PAD) and arise from a single metatarsal as unipennate muscles. • Dorsal interossei ABduct (DAB) and arise from two metatarsals as bipennate muscles. 8

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• Two neurovascular planes between the muscle layers of the sole of the foot: - a superficial one between the 1 st and the 2 nd muscular layers - a deep one between the 3 rd and the 4 th muscular layers. • Tibial nerve divides posterior to the medial malleolus into the medial and lateral plantar nerves. • These nerves supply the intrinsic muscles of the plantar aspect of the foot. • The medial plantar nerve courses within the medial compartment of the sole between the 1 st and 2 nd muscle layers. • the lateral plantar nerve (and artery) run laterally between the muscles of the 1 st and 2 nd layers of plantar muscles. Their deep branches then pass medially between the muscles of the 3 rd and 4 th layers. • Two closely connected muscles on the dorsum of the foot are the extensor digitorum brevis (EDB) and extensor hallucis brevis (EHB). 14

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ARCHES OF FOOT • Foot is composed of bones connected by ligaments and absorb shock. • Tarsal and metatarsal bones are arranged in longitudinal and transverse arches which supports and add to the weightbearing capabilities and resiliency of the foot. • Distribute weight over the foot as shock absorbers and springboards during walking, running, and jumping. • Weight of the body is transmitted to the talus from the tibia, posteriorly to the calcaneus and anteriorly to the “ball of the foot” • Slightly flattened during standing and resume their curvature when body weight is removed. 17

Longitudinal arch of the foot • Medial and lateral parts which act as a unit • Transverse arch of the foot spreads weight in all directions. Medial longitudinal • Higher and more important than the lateral longitudinal arch. • Composed of the calcaneus, talus, navicular, three cuneiforms, and three metatarsals. • The talar head is the keystone • Supported by tibialis anterior and posterior and fibularis longus via their tendons. 18

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Lateral longitudinal arch • Flatter than the medial part of the arch • Rests on the ground during standing. • Made up of the calcaneus, cuboid, and lateral two metatarsals. Transverse arch of the foot • Runs from side to side. • Formed by the cuboid, cuneiforms, and bases of the metatarsals. • Medial and lateral parts of the longitudinal arch serve as pillars for the transverse arch. • Tendons of the fibularis longus and tibialis posterior maintain the curvature of the transverse arch. 20

Integrity of the bony arches of the foot is maintained by: Passive factors: • Shape of the bones • Four layers of fibrous tissue that bowstring the longitudinal arch: v Plantar aponeurosis. v Long plantar ligament. v Plantar calcaneocuboid (short plantar) ligament. v Plantar calcaneonavicular (spring) ligament. Dynamic supports: v Active bracing action of intrinsic muscles of foot (longitudinal arch). v Active and tonic contraction of muscles with long tendons extending into foot: v Flexors hallucis and digitorum longus for the longitudinal arch. v Fibularis longus and tibialis posterior for the transverse arch. 21