SCID 242 -quiz 6 - Leg And Foot

1. Your patient was struck by a car's bumper as she crossed the street, and her fibular neck is broken. After the bone has healed, she has "foot drop", i. e. she cannot dorsiflex her foot, and so it flops onto the ground during walking. Denervation (paralysis) of which of the following muscles would be associated with foot drop?

Fibularis longus

Tibialis posterior

Fibularis brevis

Tibialis anterior

Popliteus

Tibialis anterior is the major dorsiflexer of the foot--if it is damaged, you will observe foot drop. It is found in the anterior compartment and is innervated by the deep fibular nerve. This patient probably damaged her common fibular nerve in the accident.

Explanation

Tibialis anterior is the major dorsiflexer of the foot--if it is damaged, you will observe foot drop. It is found in the anterior compartment and is innervated by the deep fibular nerve. This patient probably damaged her common fibular nerve in the accident.

2. A patient with a fracture to the left upper tibia was treated with a plaster cast. A few days later he started to develop progressive numbness over the dorsum of the foot and weakness in dorsiflexion. The cast was quickly changed and the signs were attributed to nerve compression. The compressed nerve was most likely the: ___________

Tibial

Common fibular

Sciatic

Obturator

Femoral

The common fibular nerve must have been compressed in the cast. You can figure this out by thinking about the two branches of the common fibular nerve. The first branch is the deep fibular nerve which innervates the anterior compartment of the leg and is responsible for dorsiflexion of the foot. The second branch, the superficial fibular nerve, innervates the lateral (everter) compartment and provides cutaneous innervation to the dorsum of the foot.

Explanation

The common fibular nerve must have been compressed in the cast. You can figure this out by thinking about the two branches of the common fibular nerve. The first branch is the deep fibular nerve which innervates the anterior compartment of the leg and is responsible for dorsiflexion of the foot. The second branch, the superficial fibular nerve, innervates the lateral (everter) compartment and provides cutaneous innervation to the dorsum of the foot.

3. A pedestrian is struck by a car, and his fibular neck is fractured. There is no indication of foot drop, but he cannot evert his foot and the top of his foot is numb. This apparent nerve lesion would affect which of the following muscles?

Tibialis posterior

Tibialis anterior

Fibularis tertius

Fibularis longus

Adductor hallucis

A fracture of the fibular neck commonly causes an injury to the common fibular nerve, which has two branches: the deep fibular nerve and the superficial fibular nerve. The superficial fibular nerve, however, innervates the lateral compartment of the leg which allows for eversion. It also provides cutaneous sensation to the dorsum of the foot. An injury to this nerve fits with the patient's symptoms. The superficial fibular nerve innervates fibularis longus and brevis, so D is your answer.

Explanation

A fracture of the fibular neck commonly causes an injury to the common fibular nerve, which has two branches: the deep fibular nerve and the superficial fibular nerve. The superficial fibular nerve, however, innervates the lateral compartment of the leg which allows for eversion. It also provides cutaneous sensation to the dorsum of the foot. An injury to this nerve fits with the patient's symptoms. The superficial fibular nerve innervates fibularis longus and brevis, so D is your answer.

4. A player is kicked on the front of his leg during a soccer game, and a large bruise develops. A hematoma deep to the crural fascia can create extreme pressure within the anterior compartment of the leg, compressing structures within it. The most likely finding resulting from this anterior compartment syndrome is: _____

Numbness on the dorsum of the foot

Inability to evert the foot

Inability to invert the foot

Foot drop

Inability to plantarflex the foot

Anterior compartment syndrome leads to foot drop due to the compression of the deep fibular nerve. Since the deep fibular nerve innervates tibialis anterior, an important dorsiflexer, injuring this nerve will impair dorsiflexion and cause the foot to drop.

Explanation

Anterior compartment syndrome leads to foot drop due to the compression of the deep fibular nerve. Since the deep fibular nerve innervates tibialis anterior, an important dorsiflexer, injuring this nerve will impair dorsiflexion and cause the foot to drop.

5. A car strikes a pedestrian on the lateral side of her leg. Following the accident, she has "foot drop". Her foot hangs loosely in plantar flexion when she raises it off the ground. She can still invert her foot, but cannot evert it. She can flex but not extend her toes. Which nerve is most likely to have been crushed in her accident?

Superficial fibular

Common fibular

Tibial

Medial plantar

Sciatic

All of these symptoms are consistent with damage to the common fibular nerve, whose branches, the deep and superficial fibular nerves, innervate the anterior and lateral compartments. The anterior compartment is important for dorsiflexion. The loss of eversion suggests that the lateral, everter compartment has been damaged--it is innervated by the superficial fibular nerve.

Explanation

All of these symptoms are consistent with damage to the common fibular nerve, whose branches, the deep and superficial fibular nerves, innervate the anterior and lateral compartments. The anterior compartment is important for dorsiflexion. The loss of eversion suggests that the lateral, everter compartment has been damaged--it is innervated by the superficial fibular nerve.

6. The most usual site for feeling the pulsations of the dorsalis pedis artery in the foot is: ______

Just behind the medial malleolus

Just lateral to the tendon of extensor hallucis longus

Behind the tendon of fibularis tertius muscle

In the second dorsal metatarsal space

Just behind the lateral malleolus.

The dorsalis pedis artery is the continuation of the anterior tibial artery. As the artery crosses into the foot, it lies just lateral to the tendon of extensor hallucis longus, so that's where you would feel a pulse.

Explanation

The dorsalis pedis artery is the continuation of the anterior tibial artery. As the artery crosses into the foot, it lies just lateral to the tendon of extensor hallucis longus, so that's where you would feel a pulse.

7. A worker falls from a height and lands on his feet. Radiographs reveal a fracture of the sustentaculum tali. The muscle passing immediately beneath it that would be adversely affected is the: ___________

Fibularis longus

Flexor digitorum longus

Flexor hallucis longus

Tibialis anterior

Tibialis posterior

The sustentaculum tali is a shelf-like, medial projection of the calcaneus, which supports the talus. The tendon of flexor hallucius longus passes under sustentaculum tali, creating a groove in the bone. So, if the sustenaculum tali was fractured, the tendon of flexor hallucis longus would be displaced from its usual position and the muscle would be affected.

Explanation

The sustentaculum tali is a shelf-like, medial projection of the calcaneus, which supports the talus. The tendon of flexor hallucius longus passes under sustentaculum tali, creating a groove in the bone. So, if the sustenaculum tali was fractured, the tendon of flexor hallucis longus would be displaced from its usual position and the muscle would be affected.

8. While walking barefoot on the beach in Pattaya following final exams, a medical student steps on a sharp shell which punctures the sole of her foot. She notices that she can no longer spread her toes apart (without using her hands, that is). Which nerve must have been injured?

Deep fibular

Lateral plantar

Medial plantar

Sural

Tibial

This medical student is unable to abduct her toes--this must mean that her dorsal interosseus muscles are denervated. These dorsal interosseus muscles are innervated by the deep branch of the lateral plantar nerve, so this must be the nerve that was damaged.

Explanation

This medical student is unable to abduct her toes--this must mean that her dorsal interosseus muscles are denervated. These dorsal interosseus muscles are innervated by the deep branch of the lateral plantar nerve, so this must be the nerve that was damaged.

9. A patient has been diagnosed with bone cancer in the fibula that necessitates its removal. Which of the following muscles would be least affected following removal of the fibula?

Biceps femoris

Extensor digitorum longus

Flexor digitorum longus

Flexor hallucis longus

Peroneus tertius

Flexor digitorum longus is the most medial muscle in the deep posterior compartment of the leg. This means that it takes origin from the middle half of the posterior surface of the tibia and is not attached to the fibula in any way.

Explanation

Flexor digitorum longus is the most medial muscle in the deep posterior compartment of the leg. This means that it takes origin from the middle half of the posterior surface of the tibia and is not attached to the fibula in any way.

10. A patient has stepped on a board with a long nail sticking up from it, and the nail penetrated the patient's foot between the bases of the first and second metatarsals. What artery is most likely injured at this location?

Arcuate

Deep plantar

Dorsalis pedis

Lateral plantar

Medial plantar

The deep plantar artery is a branch of dorsalis pedis, the major artery supplying blood to the dorsum of the foot. The deep plantar artery dives from the dorsum of the foot to the sole of the foot between the two heads of the dorsal interosseous muscle between the first and second toes. It then unites with the lateral plantar artery to form the plantar arterial arch.

Explanation

The deep plantar artery is a branch of dorsalis pedis, the major artery supplying blood to the dorsum of the foot. The deep plantar artery dives from the dorsum of the foot to the sole of the foot between the two heads of the dorsal interosseous muscle between the first and second toes. It then unites with the lateral plantar artery to form the plantar arterial arch.