common peroneal nerves superior to the popliteal fossa. Damage to it might
result in deficits in both plantar flexion and dorsiflexion. The femoral nerve
(answer b)innervates the quadriceps muscles of the anterior thigh. Dam-
age to it would impair flexion of the thigh at the hip.
492.The answer is b.(Moore and Dalley, pp 672–674.)The saphenous
nerve accompanies the great saphenous vein along the medial aspect of the
leg and foot as far as the great toe. The medial femoral cutaneous nerve
(answer a)innervates the dorsal aspect of the leg. The superficial fibular
nerve (answer c)innervates the central portion of the dorsum of the foot.
The sural cutaneous nerve (answer d)innervates the lateral aspect of the
foot. The medial and lateral plantar branches of the tibial nerve (answer e)
supply the sole of the foot.
493.The answer is b.(Moore and Dalley, pp 639, 670–671.)The dorsal
pedal artery, a continuation of the anterior tibial artery, passes onto the dor-
sum of the foot between the tendons of the extensor hallucis longus and
extensor digitorum longus muscles. The dorsal pedal pulse may be pal-
pated here before the artery passes beneath the extensor hallucis brevis
muscle. The posterior tibial artery passes behind the medial malleolus,
where the posterior tibial pulse is normally palpable. None of the other
answers(answers a, c, d, and e)are correct.
494.The answer is b.(Moore and Dalley, pp 444–445.)The sacral hiatus is
used to gain access to the sacral epidural or extradural space, often to pro-
vide caudal epidural anesthesia during childbirth. Because CSF is retained
by the arachnoid and dural membranes, which terminate at about S2, the
CSF is too cranial to be reached from the sacral hiatus. The needle passed
through the posterior notanterior(answer a)sacrococcygeal ligament. The
posterior sacral foramina allow the exit of sacral spinal nerve (dorsal rami),
notCSF(answer e).The filum terminale externa (answer d)is rarely dam-
aged during the procedure. Bacteria (answer c)are notan issue.
495.The answer is d.(Moore and Dalley, pp 492–493.)The fifth lumbar
vertebra has shifted anteriorly on top of the sacrum. This condition could
also be described as subluxation of the L5 vertebra on the sacrum. Spondy-
lolisthesis is often due to a fracture of the pars interarticularis, that portion
of the vertebra arch, which forms the superior and inferior facet joints. This
Extremities and Spine Answers 601