Blunt Shoulder Trauma: Fracture, Glenohumeral Dislocation, or Acromioclavicular Separation?
Radiology Cases in Pediatric Emergency Medicine
Volume 4, Case 13
Alson S. Inaba, MD
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
An 18-year old surfer presents to the Emergency
Department complaining of right upper shoulder pain.
He states that the tip of another surfer's board struck
him on the top of his shoulder while he was paddling
out to catch a wave. He immediately felt a pop when
the surfboard struck his shoulder and states that he had
difficulty paddling back to shore secondary to the pain.
He denies any other trauma to his head, neck or chest.
He also denies any paresthesias of his left hand.
Upon presentation to the ED, he prefers to hold his
right arm adducted against his body. Inspection of the
right shoulder region is only significant for superficial
abrasions and mild erythema over the superior aspect
of the shoulder joint without any obvious swelling or
View his shoulder.
The angle (contour) of the right shoulder appears
symmetric when compared to the left shoulder (i.e.,
there is no obvious drooping of the affected shoulder).
There is no fullness or tenderness in the deltopectoral
groove. There is no tenderness over the humeral head
or neck. With the right arm in the adducted position, he
is able to fully internally and externally rotate the right
arm without any exacerbation of the shoulder pain.
Palpation of the clavicle does not reveal any crepitus or
obvious fractures. His distal neurovascular examination
a) What is the most likely diagnosis based on the
above history and clinical examination?
b) What radiographic view(s) would you obtain to
confirm your clinical diagnosis?
Based on the mechanism of injury and the clinical
examination, the most likely diagnosis would be an
acromioclavicular separation. To radiographically
confirm this diagnosis, an AP view of the affected
shoulder (specifically looking at the acromioclavicular
and coracoclavicular joints) is obtained.
View shoulder radiograph.
a) What is your radiologic diagnosis?
b) Would you classify this type of acromioclavicular
injury as a type I, type II or type III acromioclavicular
c) How should this type of injury be treated?
In order to thoroughly understand the clinical
assessment, radiographic evaluation and treatment of
acromioclavicular separations, one must first have a
very clear understanding of the anatomy of this region
of the shoulder.
View shoulder anatomy.
The function of the acromioclavicular (AC) joint is to
elevate and abduct the arm. Although the term "AC
separation" refers solely to the AC ligament, stability of
the shoulder joint is actually dependent upon two
ligaments; the AC ligament and the coracoclavicular
(CC) ligament. The AC ligament anchors the distal tip
of the clavicle to the acromion process of the scapula.
The CC ligament consists of two separate ligaments
which anchor the distal clavicle to the coracoid process
of the scapula. The degree of injury to this CC ligament
largely determines the classification of AC separation
The two most common mechanisms which cause
AC separations are either direct trauma to the point of
the shoulder (i.e., a direct blow to the AC joint region,
as in the case of our patient) or secondary to falling and
landing on the deltoid region with the arm in the
adducted position. An indirect mechanism which can
also produce an AC separation is when force is
indirectly transmitted to the AC joint secondary to a fall
on the outstretched hand.
The physical examination of a patient with an AC
separation will depend upon the degree of AC
separation. If there is no accompanying dislocation of
the glenohumeral joint, one would not expect to see the
typical signs of an anterior shoulder dislocation (i.e.,
asymmetric contour of the shoulder, fullness with
tenderness in the deltopectoral groove, exacerbation of
pain with external rotation, etc.). The majority of
patients with AC separations will have some degree of
tenderness directly over the AC joint. However, with
severe AC separations (type III), the normal AC joint
prominence may be exaggerated. This exaggeration of
the AC joint prominence is secondary to the upward
displacement of the distal tip of the clavicle and the
downward pull of the shoulder (caused by the weight of
the arm) and the loss of the integrity of the suspending
Although the term "AC injuries" refers to the AC
ligament, the classification and treatment of "AC
injuries" are dependent upon the degree of injury of
both the AC and CC ligaments.
Type I (or first-degree) AC separation:
This degree of AC injury (typically referred to as an
AC "sprain") involves an incomplete tear of the AC
ligament. Because this tear is incomplete and the CC
ligament remains intact, the radiographs are normal
EVEN WITH stress views (i.e., no radiologic evidence
Type II (or second-degree) AC separation:
View the diagram of a type II injury.
This degree of AC injury involves a subluxation of
the AC joint (secondary to a partial or complete tear of
the AC ligament). As with type I injuries, the CC
ligament also remains intact with type II AC
separations. The subluxation of the AC joint (i.e.,
widening of the AC joint space as compared to the
unaffected side) may or may not be evident on the
routine shoulder radiographs (AP erect view).
Therefore, when a type II AC separation is clinically
suspected and the routine radiographs are within
normal limits, stress views can be obtained. These AP
stress views are obtained (in the erect position) with
weights (5-15 pounds or 2-7 kg) suspended by the
patient's wrist (Do not have the patient hold the
weights). This stress view will bring out any degree of
AC joint subluxation that was not evident on the initial
routine radiographs. Subluxation of the AC joint is
radiologically confirmed if the AC joint appears wider on
the stress view (as compared to the routine nonstress
views) and/or if the inferior border of the distal tip of the
clavicle is not in alignment with the inferior border of the
View this alignment of the inferior border of the clavicle
and the inferior border of the acromion process.
With type II separations, this malalignment of the
inferior borders of the distal clavicle and acromion
process should not be more than half the diameter of
the clavicle. Separation of the distal clavicle by more
than one-half of its diameter from the acromion process
indicates a type III AC injury.
Type III (or third-degree) AC separation:
View the diagram of a type III injury.
This type of injury involves a complete tear of both
the AC and CC ligaments which then results in a
complete dislocation of the AC joint. Clinically, type III
injuries will present with an exaggeration of the normal
AC prominence secondary to the upward displacement
of the distal tip of the clavicle and the downward pull of
the shoulder (caused by the weight of the arm) and the
loss of the integrity of the suspending CC ligament. If a
type III injury is clinically suspected, the AP view of the
shoulder should be obtained in the erect position to
allow the weight of the suspended arm to bring out the
classic radiographic findings of a type III separation.
The radiographic findings of a type III AC separation
may not be evident if the AP radiograph of the shoulder
is obtained with the patient in the supine position.
Radiographically type III injuries reveal: a) a widening
of both the AC and CC joint spaces on the routine erect
AP views (as compared to the AC and CC joint spaces
of the unaffected shoulder) and b) the inferior border of
the distal clavicle is clearly malaligned (i.e., separated
by more than one-half the diameter of the clavicle) with
the inferior border of the acromion process [Click on
Align]. When a type III AC separation is confirmed on
the routine AP erect views, stress views with weights
are not necessary.
Treatment & Prognosis of AC separations:
The initial ED treatment of all three types of AC
injuries involves placing the patient in a shoulder
immobilizer with the arm adducted against the chest.
This can be accomplished with any of the commercially
available shoulder immobilizers or by placing the patient
in a sling and swathe immobilizer. Early range of
motion exercises are encouraged for type I injuries.
Type II and type III injuries should be referred to an
orthopedic surgeon for further evaluation and
rehabilitation. Although internal fixation used to be
advocated for the majority of type III injuries, some
authorities are now attempting to treat these types of
injuries with three weeks of immobilization in a
Kenney-Howard sling or other similar shoulder
Post-Case Quiz Questions:
1. Name the two ligaments that make up the AC
2. Describe the two most common mechanisms of
injury that can cause an AC injury
3. The classification of AC separations is dependent
upon the integrity of the coracoclavicular ligament.
True or False?
4. If the line connecting the inferior border of the
distal clavicle to the inferior border of the acromion
process is malaligned, this is by definition a type III AC
separation. True or False?
5. Stress views are always required to
radiographically confirm the diagnosis of a type III AC
separation. True or False?
Shoulder, including clavicle and scapula. In: Harris
JH, et al. The Radiology of Emergency Medicine, third
edition. Baltimore, Williams & Wilkins, 1993, pp.
The shoulder and upper arm. In: Simon RR,
Koenigsknecht SJ. Emergency Orthopedics: The
Extremities, third edition. Norwalk, CT, Appleton &
Lange, 1995, pp. 387-389.
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Web Page Author:
Loren Yamamoto, MD, MPH
Associate Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine