TBL8 - Ankle and Foot

Question 1

Identify the talus, calcaneus, the calcaneal tuberosity and sustentacular tali, the navicular and cuboid bones, and three cuneiform bones. Understand the 7 bones constitute the tarsal bones; and observe the metatarsal bones and phalanges

Answer 1

Look at figure

Question 2

How does the tibia transmit body weight from the knee to the foot? What are two articulations of the ankle joint? What are the two main movements of the ankle joint?

Answer 2

1) By articulating with the talus bone, the tibia transmits body weight from the knee to the foot
2) The ankle joint includes articulations of the superior aspect of the talus with the tibial medial malleolus and fibular lateral malleolus
3) Dorsiflexion of the ankle is produced by the muscles in the anterior compartment of the leg
4) Plantarflexion of the ankle is produced by the muscles in the posterior compartment of the leg

Question 3

What are the 3 lateral ligaments of the ankle joint? What is the function of the medial ligament?

Answer 3

1) Anterior talofibular ligament, a flat, weak band that extends anteromedially from the lateral malleolus to the neck of the talus
2) Posterior talofibular ligament, a thick, fairly strong band that runs horizontally medially and slightly posteriorly from the malleolar fossa to the lateral tubercle of the talus
3) Calcaneofibular ligament, a round cord that passes postero-inferiorly from the tip of the lateral malleolus to the lateral surface of the calcaneus
4) The strong medial (aka deltoid) ligament attaches the medial malleolus of the tibia to the talus, calcaneus, and navicular bone

Question 4

Why is a Pott fracture-dislocation of the ankle erroneously called a trimalleolar fracture?

Answer 4

A Pott fracture–dislocation of the ankle occurs when the foot is forcibly everted. This action pulls on the extremely strong medial ligament, often tearing off the medial malleolus. The talus then moves laterally, shearing off the lateral malleolus or, more commonly, breaking the fibula superior to the tibiofibular syndesmosis. If the tibia is carried anteriorly, the posterior margin of the distal end of the tibia is also sheared off by the talus, producing a “trimalleolar fracture.” In applying this term to this injury, the entire distal end of the tibia is erroneously considered to be a “malleolus.”

Question 5

Why are ankle sprains almost always inversion injuries and which ligaments of the ankle joint are frequently torn?

Answer 5

1) A sprained ankle is nearly always an inversion injury, involving twisting of the weight-bearing plantarflexed foot. The person steps on an uneven surface and the foot is forcibly inverted
2) Lateral ligament sprains, the anterior talofibular ligament, and the calcaneofibular ligament may be torn

Question 6

What does the anatomical subtalar joint represent? What is the surgical subtalar joint part of? What is the function of the subtalar joint?

Answer 6

1) The anatomical subtalar joint represents the single talocalcaneal articulation
2) The surgical subtalar joint is the talocalcaneal part of the compound talocalcaneonavicular joint
3) The subtalar joint enables inversion and eversion of the foot
4) The subtalar joint transmits the weight of the body to the calcaneus, the largest and strongest bone of the foot that transmits the weight to the ground

Question 7

Why are comminuted fractures of the calcaneus usually disabling?

Answer 7

1) A hard fall onto the heel, from a ladder for example, may fracture the calcaneus into several pieces, producing a comminuted fracture
2) A calcaneal fracture is usually disabling because it disrupts the subtalar (talocalcaneal) joint, where the talus articulates with the calcaneus

Question 8

How are the tarsal and metatarsal bones arranged? What is the function of the arches?

Answer 8

1) The tarsal and metatarsal bones are arranged in a higher medial longitudinal arch and a flatter lateral longitudinal arch with a single transverse arch between them
2) The arches are springboards to assist the flexor hallucis longus in propelling the foot off the ground during walking, running, and jumping

Question 9

What is the function of the plantar calcaneonavicular ligament? What is the function of the tibialis posterior and flexor digitorum longus?

Answer 9

1) The plantar calcaneonavicular ligament (aka spring ligament) provides important passive support to the medial longitudinal arch
2) The tendons of the tibialis posterior and flexor digitorum longus provide active support to the medial arch

Question 10

How is the plantar aponeurosis formed? What is its function?

Answer 10

1) The deep fascia of the sole of the foot (aka plantar fascia) is thickened centrally to form the plantar aponeurosis
2) It functions as a superficial ligament that assists passive support of the medial arch by the spring ligament

Question 11

What causes acquired flatfeet and how do they differ from rigid flatfeet?

Answer 11

1) Rigid flatfeet with a history that goes back to childhood are likely to result from a bone deformity (such as a fusion of adjacent tarsal bones)
2) Acquired flatfeet (“fallen arches”) are likely to be secondary to dysfunction of the tibialis posterior (dynamic arch support) owing to trauma, degeneration with age, or denervation

Question 12

When is pain from this inflammatory condition most severe, when does it dissipate, and how is it exacerbated?

Answer 12

1) Inflammation of the plantar fasci —plantar fasciitis— is often caused by an overuse mechanism
2) The pain is often most severe after sitting, and when beginning to walk in the morning
3) It usually dissipates after 5–10 minutes of activity and often recurs again following rest
4) Point tenderness is located at the proximal attachment of the aponeurosis to the medial tubercle of the calcaneus and on the medial surface of this bone. The pain increases with passive extension of the great toe and may be further exacerbated by dorsiflexion of the ankle and/or weightbearing

Question 13

What does the tibial nerve bifurcate into? What is the function of these branches?

Answer 13

1) Posterior to the medial malleolus, the tibial nerve bifurcates into the medial and lateral plantar nerves
2) The nerves provide somatic sensory function to the respective halves of the plantar surface of the foot

Question 14

What is the function of the superficial fibular nerve? What does it innervate? What does the deep fibular nerve innervate?

Answer 14

1) The superficial fibular nerve is sensory to the lateral side of the ankle
2) It continues distally to innervate the dorsum of the foot
3) The deep fibular nerve innervates the skin between the 1st (big) and 2nd toes

Question 15

What is the sural nerve formed by? What is its function? Where does the terminal portion of the saphenous nerve lie? What is its function?

Answer 15

1) The sural nerve is formed by branches from the tibial and common fibular (peroneal) nerves
2) The sural nerve provides sensory function to the lateral side of the foot
3) The terminal portion of the saphenous nerve resides anterior to the medial malleolus
4) The saphenous nerve continues distally to provide sensory innervation to the medial side of the foot

Question 16

Why can injury of the sciatic nerve in the gluteal region cause loss of sensation from the foot?

Answer 16

1) The sciatic nerve runs inferolaterally under cover of the gluteus maximus, midway between the greater trochanter and ischial tuberosity. The nerve rests on the ischium and then passes posterior to the obturator internus, quadratus femoris, and adductor magnus muscles
2) The sciatic nerve supplies no structures in the gluteal region. It supplies the posterior thigh muscles, all leg and foot muscles, and the skin of most of the leg and foot. It also supplies the articular branches to all joints of the lower limb

Question 17

Where does the posterior tibial artery travel and what does it bifurcate into? What do these arteries supply?

Answer 17

1) The posterior tibial artery courses posterior to the medial malleolus and bifurcates into the medial and lateral plantar arteries
2) The arteries supply the respective halves of the sole of the foot

Question 18

What do lymph vessels of the medial foot join with? What does this result in?

Answer 18

1) Lymph vessels from the medial foot join those following the great saphenous vein
2) Thus, lymph from the medial half of the foot drains into the superficial inguinal lymph nodes

Question 19

What do lymph vessels of the lateral foot join with? What does this result in?

Answer 19

1) Lymph vessels from the lateral foot join those following the small saphenous vein
2) Thus, lymph from the lateral half of the foot drains into the popliteal lymph nodes