thoracoacromial trunk (answer e)are blood vessels just below the broken
clavicle and are at risk of being injured.
465.The answer is d. (Moore and Dalley, pp 729–730.)Subclavian vein.
Because large and important neurovascular structures pass between the
clavicle and first rib, including the subclavian artery and vein, clavicular
fractures may rarely produce life-threatening bleeding into the pleural cavity.
The subscapular artery (answer a)and lateral thoracic artery (answer c)are
both branches off the lateral one-third of the axillary artery, so notlikely
injured. The thoracocervical trunk (answer e)is medial to the first rib,
thus is also notlikely to be threatened by clavicular fracture. The brachio-
cephalic artery (answer a)is too medial to be damaged. The cephalic vein
(answer b)is superficial and lateral, thus normally notinvolved in clavic-
ular fractures.
466.The answer is b.(Moore and Dalley, p 736.)Colles’ fracture is a
compression/displacement of the distal end (within 2 to 3 cm) of the radius
resulting a classic dinner fork deformity [thus not (answers a and c)].
Colles’ fracture also may involve the distal portion of the ulna (sometimes
just the ulnar styloid process) if osteoporosis is present or if the forces are
sufficient. It has been estimated that Colles’ fractures represent up to 80%
of fractures of the radius bone. While falling on an outstretched hand can
result in scaphoid fractures (answer c),they rarely occur at the same time
as a distal radial fracture. Fractures of the trapezium bone (answer d)are
relatively rare.
467.The answer is c.(Moore and Dalley, pp 870–871.)Lunate. The lunate
bone tends to dislocate anteriorly into the transverse carpal arch, thereby
entrapping the tendons of the extrinsic digital flexors and compressing the
median nerve, producing symptoms of carpal tunnel syndrome (thenar weak-
ness and paresthesia over the lateral 2.5 fingers). The capitate (answer a)is
frequently fractured, but does nottend to dislocate into the carpal arch. The
hamate(answer b)provides an anchor for the transverse carpal liga-
ment and is, therefore, located lateral to the carpal tunnel. The scaphoid
(navicular) bone (answers d and e)has a tendency to fracture but does not
dislocate into the carpal tunnel. This is a relatively uncommon cause of
Carpal tunnel syndrome, but is called “carpal dislocation.”
Extremities and Spine Answers 593