of the surgical neck may rupture the posterior circumflex humeral vessels,
causing either the compression of the axillary nerve or transection of the
same nerve. Injury to this nerve causes weakness (paresis) or paralysis of the
deltoid and teres minor muscles. The nerve supply to the other muscles
mentioned are shown in parentheses: subscapularis [upper and lower sub-
scapular nerves; (answer a)]; pectoralis major [medial and lateral pectoral
nerves; (answer b)]; teres major [lower subscapular nerve; (answer c)];
and supraspinatus [suprascapular nerve; (answer e)].
462.The answer is c. (Moore and Dalley, p 646.)The common fibular
(peroneal) nerve wraps around the fibular shaft just distal to its proximal
head. This places it close to the skin, where it is easily damaged. The com-
mon fibular nerve then divides into the deep fibular nerve, which inner-
vates the anterior compartment leg muscles and the superficial fibular
nerve, which innervates the lateral compartment leg muscles. Both of these
nerves also have cutaneous distribution as well. The inability to dorsiflex the
ankle and evert the foot is consistent with the boy’s clinical presentation.
The sciatic (answer a)and obturator (answer e)nerves are in the thigh.
The deep fibular nerve (answer c)is also involved, but does notexplain all
the boy’s findings. The tibial nerve (answer b)runs more medial through
the popliteal fossa, thus is notinvolved.
463.The answer is e.(Moore and Dalley, pp 794–795.)Each of the mus-
cles listed (answers a, b, c, and d)above is innervated by the deep branch
of the radial nerve or its terminal portion, the posterior interosseus nerve.
The deep radial nerve passes between the deep and superficial layers of the
supinator muscle and lies on a bare area of the radius where it may be com-
pressed by action of the supinator or damaged by a fracture of the radius.
464.The answer is b.(Moore and Dalley, pp 729–730.)The horizontal
direction of the fibers of the clavicular head of the pectoralis major muscle
draws the humerus medially and causes the distal fragment of the bone to
sublux. The sternal head of this muscle also has the effect of pulling the arm
medially, an effect that is normally offset by the strut-like action of the clav-
icle. The pectoralis minor muscle (answer c)is a much smaller muscle and
would be the second best answer. The deltoid (answer a)muscle would
notcause inferior subluxation. The subclavian artery (answer d)and the
592 Anatomy, Histology, and Cell Biology