482.The answer is a.(Moore and Dalley, p 576.)The calcaneus is the most
frequently broken of the tarsal bones. The weight of the body is transmitted
down the tibia and onto the talus, which acts as a wedge cracking the calca-
neus inferiorly. Unfortunately, this fracture normally involves the cartilagi-
nous articular surface, complicating the healing process, increasing the
likelihood of developing an arthritic subtalar joint. These fractures often
must be held together with screws or plates for optimal healing. Since the
pain was bilateral, and only the calcaneus is bilateral across the heel, none
of the other bones (answers b, c, d, and e)listed are possible sites of frac-
ture. The distal end of the tibia (answer c)would have carried the bulk of
the force, but the pain location is inconsistent with a distal tibial fracture.
483.The answer is c.(Moore and Dalley, pp 653, 694.)To unscrew a knee
from its locked and slightly hyperextended position, the popliteus muscle
contracts and causes medial rotation of the tibia or, if the foot is planted,
lateral rotation of the femur. This movement frees the medial femoral
condyle from its posterior position on the tibial condylar surface. The
quadriceps femoris (answer d)then relaxes, and knee flexion occurs by
contraction of the hamstring muscles (answer b),assisted by the short
head of the biceps femoris, sartorius (answer e),gracilis, and gastrocne-
mius muscles (answer a).
- The answer is b.(Moore and Dalley, pp 624–625.)Perforating
branches of the deep femoral artery are the principal blood supply to the
posterior thigh. The other arteries supply anterior (answer d),medial
(answer c),and gluteal (answer a)regions of the thigh.
485.The answer is d.(Moore and Dalley, pp 643, 646.)Compression of
the common fibular (peroneal) nerve would affect all muscles innervated
by this nerve, including tibialis anterior, peroneus longus, and extensor
digitorum longus. Loss of dorsiflexion and eversion is usually complete.
The extensors of the knee joint [(answer a)quadriceps femoris] are supplied
by the femoral nerve, whereas the flexors of the knee joint [(answer c)the
hamstrings and gracilis] are supplied by the tibial nerve and obturator
nerve, respectively. The gastrocnemius and soleus muscles are the principal
plantar flexors of the foot (answer b)and are innervated by the tibial
nerve. The popliteus is the prime medial rotator of the tibia (answer e)and
is also innervated by the tibial nerve.
598 Anatomy, Histology, and Cell Biology