Download 1. A worker falls from a height and lands on his feet. Radiographs

1. 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
2. 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
3. A deep laceration, 2 cm in length, immediately posterior to the
medial malleolus, may injure any of the following EXCEPT:
fibular artery
tibial nerve
tendon of tibialis posterior m.
tendon of flexor digitorum longus m.
tendon of flexor hallucis longus m.
4. A soldier complains of foot pain following a 50 mile hike. Upon
examination, the physician diagnoses tendonitis of the fibularis
longus tendon. Because the tenderness is located deeply on the
sole of the foot, it appears that the irritation occurred where the
tendon lies against bone, covered by a structure called the:
long plantar ligament
plantar aponeurosis
short plantar ligament
spring ligament
tendon of tibialis posterior
5. A construction worker lacerates the dorsum of his foot just below
his ankle. Profuse bleeding that occurs would result from cutting
which vessel?
small saphenous vein
dorsalis pedis artery
medial plantar artery
anterior tibial artery
fibular artery
6. Compression of the lateral plantar nerve as it passes between the
flexor digitorum brevis and quadratus plantae could result in
weakness of any of the following actions EXCEPT:
abduction of the great toe
adduction of the middle toe
abduction of the little toe
adduction of the great toe
abduction of the middle toe
7. Pain may result from friction of the tendon of which muscle that
passes deep to the anterior fibers of the long plantar ligament.
tibialis posterior
flexor hallucis longus
fibularis longus
tibialis anterior
flexor hallucis brevis
8. A construction worker steps on a board with a nail in it. The nail
pierces the sole of his boot and enters his foot 2 cm anterior to his
calcaneal tuberosity, at the middle of the width of his foot. Before
reaching bone, the nail would pass through, in order:
Skin, calcaneometatarsal ligament, flexor digitorum brevis,
quadratus plantae, long plantar ligament
Skin, plantar aponeurosis, flexor digitorum brevis, quadratus
plantae, long plantar ligament
Skin, plantar aponeurosis, flexor digitorum brevis, tendons of
the flexor digitorum longus, long plantar ligament
Skin, plantar aponeurosis, quadratus plantae, flexor digitorum
brevis, long plantar ligament
Skin,transverse metatarsal ligament, flexor digitorum brevis,
quadratus plantae, long plantar ligament
9. In an accident involving farm machinery, a farmer recieves a cut
on the dorsum of his ankle. As you inspect the wound and test for
functional and sensory deficits, you find that no tendons have been
cut, but the dorsalis pedis artery and the accompanying nerve
have been cut. You would expect to find:
club foot
foot drop
inability to extend the big toe
numbness between the first and second toes
weakness in inversion of the foot
10.
While walking barefoot on the beach in Florida 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
11.
A medical student goes for a swim while on vacation in
Florida after final exams. A barracuda bites his foot, severing an
artery on the dorsum of his foot just below his ankle. Which artery
has been severed?
Anterior tibial
Deep fibular
Deep plantar
Dorsalis pedis
12.
Dorsal metatarsal
The lateral plantar nerve is a branch of which nerve?
Deep fibular
Femoral
Saphenous
Sural
Tibial
13.
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.
14.
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
Obturator
Sciatic
Femoral
Common fibular
15.
A long distance runner complained of swelling and pain of
his shin. At physical examination, skin testing showed normal
cutaneous sensation of the leg. However, muscular strength tests
showed marked weakness of dorsiflexion and impaired inversion
of the foot. Which nerve serves the muscles involved?
common fibular
deep fibular
sciatic
superficial fibular
tibial
16.
While at the beach in Florida after final exams, a medical
student steps on a stingray, which responds by stinging her in the
ankle. The stinger pierces the skin, subcutaneous tissue, and
flexor retinaculum of the ankle. Which other structure passing
under the retinaculum may be injured?
Tibial nerve
Tibialis anterior
Quadratus plantae
Anterior tibial artery
Plantar arterial arch
17.
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
18.
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
19.
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
20.
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
21.
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?
common fibular
tibial
superficial fibular
medial plantar
sciatic
1. The correct answer is:
flexor hallucis longus
The tendon of flexor hallucius longus passes under sustentaculum tali,
creating a groove in the bone. The sustentaculum tali is a shelf-like,
medial projection of the calcaneus, which supports the talus. 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. The fibularis longus tendon enters the foot on the lateral side. It
grooves the cuboid bone and travels deep to the long plantar ligament to
insert on the medial cuneiform bone. The tendon of flexor digitorum
longus crosses onto the plantar surface anterior to sustentaculum tali
and eventually divides into 4 tendons that insert into the bases of the
distal phalanges of digits 2-5. The tendon from tibialis anterior crosses
the dorsal side of the foot and inserts on the medial surface of the first
cuneiform and the first metatarsal. Finally, the tibialis posterior tendon
crosses under the foot on the medial side, anterior to both flexor hallucis
longus and flexor digitorum longus. It inserts on navicular, the medial
cuneiform, and metatarsals 2-4. So, you should not see any of these
other tendons associated with sustenaculum tali.
2. The correct answer is:
deep plantar artery
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.
The arcuate artery is on the dorsum of the foot. It would be unlikely to
injure this artery from the plantar surface. The medial plantar artery is
also on the medial side of the foot and it does distribute to the area
where the injury occured. However, the medial plantar artery supplies
blood to the superficial plantar surface of the foot, and the scenario in
the question points to an injury that would disturb deep structures in the
foot. So, deep plantar artery is the best answer.
3. The correct answer is:
Fibular artery
The flexor retinaculum is immediately posterior to the medial malleolus.
So, any of the tendons or structures coming from the posterior
compartment and crossing under flexor retinaculum to the plantar
surface of the foot might be injured. The fibular artery is a branch of the
posterior tibial artery that delivers blood to the lateral compartment of the
leg. It does not cross into the foot, and it is nowhere near the medial
malleolus. So that's your answer.
All of the other listed structures are coming from the posterior, flexor
compartment--these structures are all organized behind the flexor
retinaculum in a very characteristic way. From anterior to posterior the
structures are: tendon of Tibialis posterior, tendon of flexor Digitorum
longus, posterior tibial Artery (and vein), tibial Nerve, and tendon of
flexor Hallucis longus. So, T, D, A, N, H equals Tom, Dick, ANd Harry.
This is an important relationship to remember!
4. The correct answer is:
long plantar ligament
Remember: the fibularis longus tendon enters the foot on the lateral
side, then arches across the foot to insert on the medial cuneiform and
the base of the first metatarsal. The long plantar ligament lies directly
over this tendon. The long plantar ligament is a deep structure that
connects calcaneus with cuboid and the bases of the lateral three
metatarsals. If the fibularis longus tendon was inflamed, the long plantar
ligament might also be affected.
The plantar aponeurosis is a very superficial structure that covers and
protects the sole of the entire foot--it is not closely associated with deep
structures like the long plantar ligament. The short plantar ligament (also
called the calcaneocuboid ligament) connects calcaneus and cuboid.
The spring ligament connects sustantaculum tali with the inferior surface
of navicular. Finally, the tendon of tibialis posterior enters the foot after
traveling posterior to the medial malleolus and inserts on navicular, the
medial cuneiform, and metatarsals 2-4.
5. The correct answer is:
dorsalis pedis
The dorsalis pedis is an extension of the anterior tibial artery that
supplies the dorsal aspect of the foot. (The name change occurs at the
level of the ankle, so that's why this isn't the anterior tibial artery.)
Dorsalis pedis travels on the dorsum of the foot, slightly toward the
medial side, and it would be the artery most likely damaged by this
injury. The lesser saphenous vein forms from the dorsal venous arch of
the foot. It travels on the lateral side of the foot, and, at the ankle,
passes posterior to the lateral malleolus. So, the lesser saphenous vein
would not be traveling on the dorsum of the foot by the time it reached
the ankle. The medial plantar artery is not found on the dorsum of the
foot; it would not be damaged by this injury. Finally, the fibular artery is a
branch of the posterior tibial artery. It supplies the lateral compartment of
the leg and does not send blood to the foot.
6. The correct answer is:
abduction of the great toe
The medial plantar nerve innervates abductor hallucis, so this muscle
would be saved if the lateral plantar nerve was disrupted. The muscles
responsible for all the rest of the actions listed are innervated by the
lateral plantar nerve, or its branch, the deep lateral plantar nerve:
Adduction of the middle toe: plantar interosseus muscles (deep branch);
Abduction of the little toe: abductor digiti minimi (lateral plantar);
Adduction of the great toe: adductor hallucis (deep branch); Abduction of
the middle toe: third dorsal interosseus muscle (deep branch).
7. The correct answer is:
fibularis longus
Remember: fibularis longus runs from the lateral side of the foot across
the entire sole of the foot, traveling deep to the long plantar ligament.
The friction between these two closely related structures may lead to
discomfort. The tendon of tibialis posterior crosses behind the medial
malleolus and enters the plantar surface of the foot on the medial side,
inserting on navicular, the medial cuneiform, and metatarsals 2-4. The
tendon of flexor digitorum longus travels posterior to the medial
malleolus, and inserts on the bases of the distal phalanges of digits. The
tendon of flexor hallucius longus also crosses behind the medial
malleolus, travels under sustentaculum tali, and inserts on the base of
the distal phalanx of the first toe. Finally, tibialis anterior does not really
cross onto the plantar surface. It travels across the dorsum of the foot,
and its tendon inserts on the medial surface of the medial cuneiform and
the first metatarsal.
8. The correct answer is: Skin, plantar aponeurosis, flexor digitorum
brevis, quadratus plantae, long plantar ligament
2 cm anterior to the calcaneal tuberosity, the nail would pass through
skin, the plantar aponeurosis, flexor digitorum brevis (a superficial
muscle), quadratus plantae (a deeper muscle), and the long plantar
ligament. See the pictures in Netter plates 496-500 to get a better idea
of this. The calcaneometatarsal ligament is the lateral band of the
plantar aponeurosis--it is on the lateral part of the foot, and would not be
found at the "middle of the width of his foot." Tendons of flexor digitorum
longus are found far anterior in the foot--not just 2 cm anterior to the
calcaneal tuberosity. The transverse metatarsal ligaments are also found
far anterior in the foot, at the distal ends of the metatarsals.
9.
The correct answer is:
numbness between the first and second toes
The nerve running with the dorsalis pedis artery is the deep fibular
nerve. This nerve innervates the anterior compartment of the leg and the
extensors on the dorsum of the foot. At the point where it was cut, the
nerve had already given off all its branches to the anterior compartment
of the leg. So, the farmer should still be able to dorsiflex his foot
(preventing foot drop), and all of the muscles that invert his foot should
be intact. Although extensor hallucis brevis (on the dorsum of the foot)
has been denervated, extensor hallucis longus is in the anterior
compartment of the leg, and that muscle should still be able to extend
the great toe. However, the deep fibular nerve would have been cut
before it could supply fibers to the area of cutaneous innervation
between the first and second toe. So, there would be numbness in that
area of skin.
Club foot is a congenital anomaly which refers to a foot that has been
twisted out of position. In cases of club foot, the foot is inverted, the
ankle is plantarflexed, and the forefoot is adducted.
10. The correct answer is:
lateral plantar
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. The medial
plantar nerve innervates muscles on the plantar surface of the foot,
including abductor hallucis, flexor hallucis brevis, and flexor digitorum
brevis. None of these muscles are responsible for abducting the toes.
As far as the other nerves go... you should know that the lateral and
medial plantar nerves are the branches of the tibial nerve that continue
to the plantar surface of the foot. However, the tibial nerve proper
innervates the posterior compartment of the leg, allowing for
plantarflexion of the foot. The deep fibular nerve is the nerve that
innervates the anterior compartment of the leg--it also continues to the
dorsum of the foot and innervates extensor hallucis brevis and extensor
digitorum brevis. Finally, note that the sural nerve provides cutaneous
innervation to the skin of the posterior surface of the lower leg and the
skin of the lateral side of the foot--it is not a motor nerve.
11. The correct answer is:
Dorsalis pedis
The dorsalis pedis is a continuation of the anterior tibial artery--the name
change here occurs at the level of the ankle. Since the artery on the
dorsum of the foot was cut just below the ankle, dorsalis pedis must
have been the vessel that was injured. The deep plantar artery is a
branch of dorsalis pedis--it supplies the deep foot, and reaches this area
by passing through a space between the first and second metatarsals on
the dorsum of the foot. The dorsal metatarsal arteries are small arteries
that come off of the arcuate artery and travel to the individual digits.
They supply the dorsum of digits, excluding the distal phalangeal
segment. There is no such thing as a deep fibular artery, but it sounds
good.
12. The correct answer is:
Tibial nerve
The lateral and medial plantar nerves are both branches of the tibial
nerve. These branches continue to the plantar surface of the foot,
innervating the muscles on the plantar surface of the foot and providing
cutaneous innervation to the skin of the sole. The deep fibular nerve
innervates the anterior compartment of the leg, the muscles on the
dorsum of the foot, and provides sensory innervation to the web of skin
between the first and second toe. The femoral nerve innervates the
anterior (quadriceps) compartment of the thigh, which allows for
extension at the knee. The saphenous nerve is a branch of the femoral
nerve that travels with the great saphenous vein; it provides cutaneous
innervation to the skin of the medial side of the leg and medial side of
the foot. The sural nerve is a cutaneous nerve that provides sensory
innervation to the skin of the posterior surface of the lower leg and the
skin of the lateral side of the foot.
13. The correct answer is:
hallucius longus muscle
Just lateral to the tendon of extensor
The dorsalis pedis artery is the continuation of the anterior tibial artery
which continues on to the dorsum of the foot. The name change from
anterior tibial to dorsalis pedis occurs at the level of the ankle. 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. See Netter Plate
513 for a picture.
The pulse of the posterior tibial artery, which comes from the posterior
compartment of the leg, might be felt behind the medial malleolus. The
pulse of the fibular artery might be felt behind the lateral malleolus, but
that pulse would be very weak. There are no special pulses associated
with the tendon of fibularis tertius or the second dorsal metatarsal space.
14. The correct answer is:
Common fibular
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. The combination of symptoms (impaired dorsiflexion
and a loss of cutaneous sensation on the dorsum of the foot) suggests
that both nerves are injured. So the common fibular nerve, which both
nerves branch from, must be the structure that was damaged.
The tibial nerve innervates the posterior compartment of the leg--an
injury to this nerve would result in an inability to plantarflex the foot. The
obturator nerve innervates the medial compartment of the thigh--damage
to this nerve would impair adduction of the hip. The sciatic nerve
branches to the tibial and common fibular nerve--an injury to this nerve
would result in a great motor and sensory deficit in the leg and thigh.
Finally, the femoral nerve innervates the anterior compartment of the
thigh--damage to this nerve would denervate the quadriceps and impair
extension at the knee.
15. The correct answer is:
deep fibular nerve
The deep fibular nerve provides motor innervaton to the anterior
compartment of the leg. This compartment contains tibialis anterior, a
muscle that allows for dorsiflexion and inversion of the foot. If a patient is
unable to dorsiflex the ankle, he or she will have foot drop. When the
deep fibular nerve is damaged, cutaneous sensation to the leg and foot
is normal, except for the loss of sensation on the web of skin between
the first and second toe. This is the only place were the deep fibular
nerve supplies cutaneous innervation. This patient probably has anterior
compartment syndrome, which occurs when the muscles in the anterior
compartment of the leg swell and press on the bone or fascial lining.
Eventually, this swelling can compress the deep fibular nerve, leading to
foot drop, or the anterior tibial artery, stopping blood flow to the dorsum
of the foot.
Injuries to the common fibular nerve often occur after fibular fracture
because the common fibular nerve wraps around the neck of the fibula.
If this nerve was injured, you would see the same symptom of foot drop,
but it would be accompanied by a loss of cutaneous sensation to the
anterolateral aspect of the leg and dorsum of the foot. The sciatic nerve
branches to form the common fibular and tibial nerve. An injury to this
nerve would damage all of the compartments in the leg. The superficial
fibular nerve innervates the lateral compartment of the leg, which everts
the foot. It also provides cutaneous sensation to the distal third of the
anterior leg and the dorsum of the foot, so an injury here would lead to a
significant loss of cutaneous sensation. Finally, the tibial nerve
innervates the posterior compartment of the leg. An injury to this nerve
would impair plantarflexion of the foot.
16. The correct answer is:
Tibial nerve
The flexor retinaculum is immediately posterior to the medial malleolus.
The structures which pass under the flexor retinaculum are coming from
the posterior compartment of the leg to enter the foot. These tendons,
vessels, and nerve are all organized behind the flexor retinaculum in a
very characteristic way. From anterior to posterior the structures are:
tendon of Tibialis posterior, tendon of flexor Digitorum longus, posterior
tibial Artery (and vein), tibial Nerve, and tendon of flexor Hallucis longus.
Tom, Dick, ANd Harry! Out of all the answer choices, the tibial nerve is
the only one which lies behind the flexor retinaculum, so that's your
answer.
Tibialis anterior is in the anterior compartment of the leg--its tendon just
crosses under the extensor retinaculum to enter the dorsum of the foot.
The anterior tibial artery is also in the anterior compartment of the leg. It
crosses the ankle under the extensor retinaculum and enters the dorsum
of the foot as dorsalis pedis. Quadratus plantae is a deep muscle of the
plantar surface of the foot--it insures that the tendons from flexor
digitorum longus flex the toes properly. The plantar arterial arch is a
structure that supplies blood to the deep foot. None of these other
structures are associated with the flexor retinaculum.
17.
The correct answer is:
tibialis anterior
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. This nerve wraps around the neck
of the fibula before giving off its two branches: the deep fibular nerve
and the superficial fibular nerve. You might hypothesize that this patient
would also have a loss of cutaneous sensation on the distal third of the
anterior leg and the dorsum of the foot, since those are the areas that
receive cutaneous innervation from the superficial fibular nerve.
None of the other muscles listed are dorsiflexers. Fibularis longus and
brevis evert and plantarflex the foot; tibialis posterior plantarflexes and
inverts the foot; popliteus flexes and rotates the leg medially so that the
knee can unlock.
18. The correct answer is:
fibularis longus
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. However, this case isn't as simple. If the
common fibular nerve was damaged, the deep fibular nerve would also
be impaired. This would mean that the anterior compartment of the leg
would be denervated, and the patient would suffer from foot drop. But
that's not happening here, so you know that the common fibular nerve
must be intact. 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.
Tibialis anterior and fibularis tertius are both muscles in the anterior
compartment of the leg--they are innervated by the deep fibular nerve.
You should know that this compartment of the leg is intact because there
is no foot drop. Tibialis posterior is innervated by the tibial nerve--this
nerve was not involved in the accident. Finally, adductor hallucis is a foot
muscle innervated by the deep branch of the lateral plantar nerve, which
is a branch of the tibial nerve.
19. The correct answer is:
flexor digitorum longus
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. Biceps femoris inserts on the head of the fibula and the
lateral condyle of the tibia. Extensor digitorum longus is a muscle on the
lateral side of the anterior compartment of the leg. This means that it
takes origin from the fibula, and would be affected by its removal. Flexor
hallucis longus is the most lateral muscle in the posterior compartment,
so it originates from the fibula, too. Finally, fibularis (peroneus) longus
and brevis, the two muscles of the lateral compartment, both take origin
from the fibula.
20. The correct answer is:
foot drop
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. Numbness on the
dorsum of the foot would suggest an injury to the superficial fibular
nerve. An inability to evert the foot might also be due to an injury to the
superficial fibular nerve, since that nerve supplies the lateral, everter
compartment. Damage to the deep fibular nerve might also impair
inversion since that is an action of tibialis anterior, but this would be a
more subtle finding. Also, remember that tibialis posterior is also an
inverter, so that muscle might be able to compensate for the injury to the
anterior compartment. Finally, an inability to plantarflex the foot would
stem from damage to the tibial nerve and the posterior compartment.
21. The correct answer is:
common fibular
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. When the tibialis anterior of
this compartment is denervated, you will see foot drop. This
compartment also contains extensor hallucis longus and extensor
digitorum longus. These muscles and their brevis counterparts on the
dorsum of the foot (which are also innervated by the deep fibular nerve)
are responsible for extending the toes. Since this function is also lost, it
is clear that the injury has affected the deep fibular nerve. Finally, the
loss of eversion suggests that the lateral, everter compartment has been
damaged--it is innervated by the superficial fibular nerve.
If the injury was only to the superficial fibular nerve, you would not
expect foot drop or difficulty extending the toes. Instead, the main
symptom would be a loss of cutaneous sensation over the distal third of
the leg and the dorsum of the foot. An injury to the tibial nerve would
lead to problems with plantarflexion due to denervation of the posterior
compartment. The medial plantar nerve innervates structures in the foot
and would not produce these symptoms. Finally, the sciatic nerve gives
rise to the tibial and common fibular nerves. An injury to the sciatic nerve
would lead to deficits in all the compartments of the leg.