334 Emergency Medicine
296.The answer is a.(Simon and Koenigsknecht, p 143.)The blood sup-
ply to the scaphoid normally penetrates the cortex at the distal aspect of the
bone. Therefore, there is no direct blood supply to the proximal portion
of the bone, which predisposes this fragment to avascular necrosis and
delayed union. The more proximal the fracture is in scaphoid injuries, the
greater the likelihood of developing vascular necrosis.
297.The answer is c.(Rosen, pp 592-602.) This patient has an anterior
shoulder dislocation.The glenohumeral joint is the most commonly dis-
located joint in the body, mainly because of the lack of bony stability and
its wide range of motion. Anterior dislocations account for 95% to 97% of
cases and are most commonly seen in younger, athletic males and geriatric
females. It usually happens by way of an indirect force that involves an
abduction plus extension plus external rotation injury. Directly, it may
occur as a result of a posterior blow that forces the humeral head out of the
glenoid rim anteriorly. Radiographs obtained must include an axillary view
to determine positioning of the humeral head. Patients usually present in
severe pain, holding the affected arm with the contralateral hand in slight
abduction. The lateral acromial process is prominent giving the shoulder a
full or squared-off appearance. Patients typically cannot internally rotate
their shoulder. Axillary nerve injuriescan occur in up to 54% of anterior
dislocations; however, these are neuropraxic in nature and tend to resolve
on their own. Following the C5/C6 dermatome distribution, patients have
a loss of sensation over the lateral aspect of the deltoid with decreased mus-
cle contraction with abduction. After proper muscle relaxation with con-
scious sedation or intra-articular injection, closed reduction may be
attempted using a variety of methods. After reduction, it is imperative to
repeat a neurovascular examination and obtain confirmatory radiographs.
Acromioclavicular joint sprains (a) occur primarily in men and
account for 25% of all dislocations. However, the mechanism of injury pri-
marily involves a fall or direct blow to the adducted arm causing a down-
ward and medial thrust to the scapula.
Posterior dislocations (b and e)are rare owing to the scapular angle on
the thoracic ribs. They are seen, however, in convulsive seizures where the
large internal rotator muscles overpower the weaker external rotators and
cause the dislocation. Median nerve injuries (d)mainly involve weakness in
the first three finger flexors. Ulnar nerve injuries (e)mainly involve weak-
ness in the interossei muscles of the hand and paresthesias along the fifth
digit.