necrosis of the head will occur because the only remaining blood supply to
the head (through the ligamentum teres) is inadequate to sustain it. The
nearer the fracture to the femoral head, the more likely the disruption of the
retinacular blood supply. None of the other answers are correct.
479.The answer is e.(Moore and Dalley, pp 585–586.)The lateral femoral
cutaneous nerve passes beneath the inguinal ligament just medial to the
anterior superior iliac spine. It innervates the lateral aspect of the thigh.
The iliohypogastric nerve (answer c)innervates a portion of the gluteal,
inguinal, and pubic regions. The ilioinguinal nerve (answer d)and the
femoral branch of the genitofemoral nerve (answer a)supply the upper
portions of the anterior thigh. The sensory distribution of the femoral
nerve (answer b)innervates the anterior thigh and medial leg.
480.The answer is b.(Moore and Dalley, pp 334, 337–339.)Flexion of the
thigh would be least affected. The lesion involves the common iliac artery
just proximal to its division into the internal and external iliac branches.
Blood flow would be compromised to the external iliac artery and its
downstream branches including the femoral, deep femoral, popliteal, tib-
ial, fibular, and plantar arteries. Blood flow would also be diminished to
branches of the internal iliac artery, including gluteal (answer a)and vis-
ceral arteries. One of the most powerful flexors of the thigh is the psoas
muscle, which originates from the lumbar vertebrae and receives most of
its blood from the aorta and common iliac artery and thus would be unaf-
fected by the lesion. All functions more distal to the blockage would likely
be affected [thus not (answers c, d, and e)].
481.The answer is b. (Moore and Dalley, pp 695–699.)The excess ability
to displace a flexed leg anteriorly is the anterior drawer sign, used to test for
disruption of the anterior cruciate ligament (ACL) tear. If the ACL is torn,
when the knee is flexed, the cranial part of the leg may be pulled forward
excessively. If the posterior cruciate ligament, structure 12 were torn, then
(answer awould have been correct). Excess ability to displace the ankle
medially(answer c)or laterally (answer d)would arise if the lateral and
medial collateral knee ligaments were torn, respectively. The other numbered
structures are as follows: 1, femur; 2, tibia; 8, patella; 9, anterior cruciate lig-
ament; 10, popliteal artery and vein; 11, head of the gastrocnemius muscle;
and 12, posterior cruciate ligament.
Extremities and Spine Answers 597