454.The answer is d.(Moore and Dalley, pp 728, 732–733, 876.)The large
arrows indicate the proximal humeral epiphyseal plate. The young girl was
only 11 and still growing. The epiphyseal plates show up on x-rays as radi-
olucent cartilage and should notbe confused with a fracture. The epiphysis
is located at the anatomic neck of the humerus but is notdiscoid-shaped like
many epiphyseal plates in long bones. This plate is tent-shaped, which is
why it is notclearly visible all the way across the proximal humerus. The
fracture at the anatomic neck of the humerus is marked by the small arrows
(answer a).The glenohumeral joint is more medial (answer b).The joint
space between the proximal humerus and the acromion of the scapula
(answer c)is more superior. The shoulder is notdislocated or separated
(answer e).
455.The answer is b.(Moore and Dalley, pp 778, 819–822.). The patient
has a classic case of carpal tunnel syndrome, in which the median nerve is
compressed as it passes through the carpal tunnel formed by the flexor reti-
naculum in the wrist. Evidence for involvement of the median nerve is
weakness and atrophy of the thenar muscles (abductor pollicis brevis,
opponens pollicis) and lumbricals 1 to 3. Sensory deficits also follow the
distribution of the median nerve. The median nerve enters the hand, along
with the tendons of the superficial and deep digital flexors, through a tun-
nel framed by the carpal bones and the overlying flexor retinaculum.
Symptoms are worse in the early morning and in pregnancy because of
fluid retention, resulting in swelling that entraps the median nerve. Flexing
the wrist for an extended period exaggerates the paresthesia (“Phelan’s”
sign) by increasing pressure on the median nerve.
Neitherthe ulnar nerve (answer c),radial nerve (answer e),nor
radial artery (answer a)passes through the carpal tunnel. The ulnar nerve
supplies the third and fourth lumbricals and only the short adductor of
the thumb. The radial nerve innervates mostly long and short extensors of
the digits and the dorsal aspect of the hand. Proper digital nerves (answer a)
lie distal to the carpal tunnel but are only sensory.
456.The answer is c.(Moore and Dalley, pp 733–734, 779.)Radial nerve at the
distal third of the humerus. The clinical signs and findings in the patient pre-
sented in the question indicate radial nerve damage. The evidence that exten-
sion (triceps brachii muscle) at the elbow appeared normal while supination
appeared weak can be used to localize the lesion. The innervation to the
Extremities and Spine Answers 589