Download The Abduction External Rotation (ABER) View for MRI of the

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The Abduction External Rotation (ABER) View
for MRI of the Shoulder
Jaideep J. Iyengar, MD; Keith R. Burnett, MD; Wesley M. Nottage, MD
The ABER view is an excellent tool for detecting subtle
soft tissue pathology of the anteroinferior labrum and
rotator cuff and is strongly advocated for all contrastenhanced imaging of the shoulder.
S
houlder magnetic resonance imaging (MRI) is
the gold standard imaging
modality for evaluating soft
tissue in the shoulder joint.
The abduction external rotation (ABER) view has been
discussed in the literature as
an excellent tool beyond the
conventional 3 sequences
(coronal, sagittal, and axial)
for accurately assessing anteroinferior labral detachment
and both partial- and fullthickness tears of the rotator
cuff tendons.1-5 Placing the
arm in an abducted and externally rotated position tensions
the anteroinferior glenohumeral ligament and labrum. If
a labral detachment is present,
contrast solution defines the
defect. Likewise, abduction
and external rotation of the
arm releases tension on the
cuff relative to the normal coronal view obtained with the
arm in adduction. As a result,
subtle articular-sided partial
thickness flap tears will not lie
Drs Iyengar and Nottage are from The Sports Clinic Orthopaedic Medical Associates, Inc, Laguna Hills, and Dr Burnett is from Laguna Niguel
MRI, Inc, Laguna Niguel, California.
Drs Iyengar, Burnett, and Nottage have no relevant financial relationships to disclose.
The authors thank Arif Ali, MD, Eric M. Price, MD, Gen Marayama,
MD, and Anthony Stauffer, MD, for their preliminary work on this article,
and Phil Pador, MRI technician, for his assistance in providing the images
for the article.
Correspondence should be addressed to: Keith R. Burnett, MD, Laguna
Niguel MRI, Inc, 25500 Rancho Niguel Rd, Ste 140, Laguna Niguel, CA
92677 ([email protected]).
doi: 10.3928/01477447-20100625-17
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ORTHO0810Iyengar.indd 562
apposed to the adjacent intact
fibers of the remaining rotator
cuff nor be effaced against the
humeral head, and intra-articular or intravenous contrast
can enhance visualization of
the tear.6 In addition, tears
with a horizontal component
are identified and characterized with increased sensitivity
with the ABER view.4
The ABER view is a modified axial view. Because the
orientation of the ABER view
differs from the traditional
images that orthopedists are
accustomed to viewing, its interpretation can be confusing
for those with limited or no
experience. Furthermore, the
execution of the ABER view
can be a challenge for the technologist unfamiliar with its
use. This article addresses the
method by which the ABER
technique is performed and the
regional anatomy that can be
seen on these MRI scans.
TECHNIQUE
Orthopedists consider 90⬚
of abduction and 90⬚ of external rotation the position of
apprehension. However, most
1
Figure 1: ABER positioning. Note that
the classically used ABER position
for arthrography is not the true 90⬚90⬚ position that orthopedists would
typically consider to be the position
of abduction and external rotation.
conventional bore-style MRI
scanners do not allow for the
shoulder to be placed in this
position. The narrow confines
of a closed tube usually necessitate use of the more commonly performed position for
the ABER view with the arm
abducted and the hand tucked
beneath the patient’s head, so
as to lessen the mediolateral
dimension of the patient’s upper torso (Figure 1).
Settings
The ABER scout views are
first obtained by acquiring images along a plane parallel to
the long axis of the humerus
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2
3
4A
Figure 2: ABER scout view. Note the orientation is parallel to the humeral shaft and perpendicular to the glenohumeral
articulation. Figure 3: Classic ABER view of a normal shoulder. Because the arm is externally rotated, the expanse of the
supraspinatus footprint insertion assumes a posterior position (white arrow). Abbreviations: G, glenoid; H, humerus;
L, labrum. Figure 4: Saline arthrogram ABER view with T2 fat-saturation technique. The appearance is similar to a
T1-weighted image with contrast (A). A low-field MRI ABER view with no fat separation. Note the rotator cable, seen
on this image as the lump in the center of the rotator cuff undersurface (B). Figure 5: ABER is a modified axial view. It
is important to realize that anterior structures (ie, coracoid process) are in the lower left quadrant and posterior structures are in the upper right quadrant. Note the long head of the biceps tendon (white arrow) posteriorly as it traverses
down the humerus. Abbreviations: C, coracoid; G, glenoid; H, humerus.
(Figure 2). Once the orientation is set with respect to the
shaft of the humerus, the plane
with respect to the scapula
is determined. The position
of the patient’s arm can vary
based on size, flexibility, and
comfort.
The ABER plane is chosen so that a stack of images
are obtained at right angles to
the glenohumeral articulation,
extending between the supraglenoid tubercle and axillary
recess. If the patient assumed
a 90⬚-90⬚ position of the arm,
as might be obtained in a vertical field open-sided scanner,
the images of the glenoid and
scapula would be much the
same as those seen in true
axial imaging. However, most
ABER views result in unique
representations of scapular
bony landmarks, each of which
is a variation of a true axial
image of the scapula. This occurs because the orientation
is based on the humeral shaft
rather than the scapula.
The ABER sequence, like
all magnetic resonance arthrographic sequences, is gener-
ally obtained as T1-weighted
to enhance the definition of
injected contrast, which appears white (Figure 3). Further
definition is provided by the
use of a method that includes
suppression of fat signal in the
bone marrow and soft tissue
around the joint. At magnetic
fields ⬎1 T, this requires spectral fat saturation; at magnetic
fields ⬍1 T, a special form of
fat separation is used. Typically, both of these techniques are
lumped together under the rubric of fat suppression. Acquisition parameters for both high
and low field are relatively
similar with the exception of
applying either fat saturation
or fat separation techniques as
appropriate based on the magnet strength. Although technically different approaches, the
output is nearly equivalent.
Should the patient be allergic to gadolinium or suffer
from renal failure, one may
alternatively achieve capsular
distention and sufficient fluid
contrast with intra-articular saline solution. If so, the ABER
view is not precluded and im-
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ages can be obtained with a
T2-weighted sequence and fat
saturation (Figure 4).
Interpretation
Conventional axial MRIs
are oriented such that posterior
structures are displayed toward
the lower edge of the frame,
and anterior structures are
in the superior margin of the
frame, irrespective of which
shoulder is scanned. However,
the ABER view rotates the image 90⬚. The ABER view is a
glenohumeral view that is essentially axial to the scapula
but coronal to the humerus.
Therefore, the anterior structures of the humerus (ie, long
head of the biceps tendon) are
rotated to the superior glenoid
and the cuff is rotated posteriorly, adjacent to the scapular
spine (Figure 5).
To avoid confusion and enhance ease of interpretation,
we recommend adoption of the
following convention for display of all ABER sequences.
The scapular spine is always
displayed to the viewer’s right,
placing the rotator cuff also on
4B
5
the right, the anterior glenoid
on the left, and the shaft of the
humerus toward the top. This
display protocol will maximize consistent recognition of
anatomic structures and pathological lesions, especially of
the rotator cuff and labrum,
independent of which side is
imaged.
The ABER view can enhance interpretive and diagnostic accuracy for several types
of pathology in the shoulder.
The ABER series can be a useful adjunct in the diagnosis of
articular-sided partial thickness and full thickness rotator
cuff tears (Figure 6A). A recent
meta-analysis comparing the
relative accuracies of magnetic
resonance arthrography, conventional MRI, and ultrasound
in diagnosing rotator cuff tears
concluded that magnetic resonance arthrography had superior sensitivity and specificity
in diagnosing both full- and
partial-thickness tears than the
other 2 modalities.7
Similarly, labral pathology
can be difficult to assess on
physical examination and/or
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6A
8A
conventional MRI sequences.
The ABER series improves
visualization of labral tears in
younger patients, especially
of the posterior superior labrum and superior labral anterior posterior (SLAP) tears
in throwing athletes, as well
as Bankart lesions associated
with shoulder dislocations or
instability events (Figure 6B).
In many cases, lesions found
on the ABER views are not
present on conventional coronal or axial MRI sequences
and would have otherwise been
missed (Figure 7). The ABER
sequence is particularly useful
in the case of partial-thickness rotator cuff tears, where
diagnostic accuracy continues
to present a challenge for conventional MRI or even ultrasound (Figure 8).
DISCUSSION
Despite the clear diagnostic
advantages of the ABER sequence, adoption has not been
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6B
8B
ubiquitous.8,9 This fact is confirmed by the informal polling
of our sports medicine fellows
and the attendees and faculty
at a yearly international conference exclusively devoted to
shoulder surgery (K. Burnett,
oral communication, 20052008). While the issue has not
been systematically investigated, we postulate several responsible factors. Adding the
sequence prolongs examination
time by approximately 25%
(including positioning), potentially detracting from time
available to other patient needs
and decreasing efficient use of
limited scanner resources.
Also, the ABER positioning is uncomfortable for some
patients and can detract from
the patient’s perception of the
testing experience. For a few
patients, typically those with
a history of multiple shoulder
dislocations, the positioning
itself may be intolerable due
to apprehension. Nevertheless,
7A
7B
Figure 6: Undersurface partial-thickness tears and full-thickness supraspinatus tears are well visualized with an image in the middle of the ABER series
(contrast extending into the tendon defect, white arrow) (A). Inferior image
in the ABER series is useful for visualizing any labral pathology (depicting a
posterior labral lesion, white arrow), including Bankart lesions when present
(B). Figure 7: Conventional axial MRI shows only a poorly defined anterior
labral abnormality (A). ABER view clearly demonstrates the labral pathology
that otherwise could have been easily missed (white arrow) (B). Figure 8:
Conventional coronal MRI in this patient demonstrated no evidence of rotator
cuff tear (A). However, ABER view showed a typical partial-thickness rotator
cuff tear with articular-sided flap and delamination propagation that otherwise
would have been overlooked (white arrow) (B).
the ABER noncompliance rate
for all MRI remains low, but is
likely between 1% and 3% (K.
Burnett, oral communication,
2003-2009). Busy departments
may not wish to add time to
their scans, and low-volume
facilities may not be able to
cope with the complexities required to perform, display, or
interpret the images with care
and competence.
Recent publications have
highlighted circumstances that
favor either adding the ABER
sequence or even substituting the ABER sequence for a
conventional series. There are
advocates for the indirect magnetic resonance arthrogram
(intravenous as opposed to
intra-articular injection).6 Although this examination has its
own limitations and interpretive pitfalls, adding the ABER
sequence has been reported to
enhance sensitivity and specificity for the diagnosis of partial- and full-thickness cuff
tears. The ABER view should
be considered mandatory when
indirect magnetic resonance
arthrograms are used.6
There may also be situations where patients cannot
tolerate much imaging time
(eg, claustrophobia, restless
leg syndrome, or mild dementia) and a full conventional
arthrogram is out of the question. For these patients, a recent article has highlighted
the feasibility and accuracy of
substituting 1 ABER sequence
for the entire conventional arthrogram as a reasonable and
accurate alternative for the diagnosis of rotator cuff tears.8
CONCLUSION
The ABER view is an excellent tool for detecting subtle soft
tissue pathology of the anteroinferior labrum and rotator cuff. A
standard display format enhances anatomical understanding
and facilitates the teaching of
interpretative principles and pit-
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■ tips & techniques
falls. The ABER sequence is
strongly advocated for all contrast-enhanced imaging of the
shoulder, whether it is intra-articularly or intravenously administered. Surprisingly, the inherent sensitivity and specificity
of ABER qualifies it as a standin for the entire conventional 3plane examination, should circumstances require.
REFERENCES
1. Cvitanic O, Tirman PF, Feller
JF, Bost FW, Minter J, Carroll
KW. Using abduction and external rotation of the shoulder
to increase the sensitivity of
MR arthrography in revealing
tears of the anterior glenoid
labrum. AJR Am J Roentgenol.
1997; 169(3):837-844.
2. Wintzell G, Larsson H, Larsson
S. Indirect MR arthrography of
anterior shoulder instability in
the ABER and the apprehension
test positions: a prospective
comparative study of two different shoulder positions during
MRI using intravenous gadodiamide contrast for enhancement of the joint fluid. Skeletal
Radiol. 1998; 27(9):488-494.
3. Tirman PF, Bost FW, Steinbach
LS, et al. MR arthrographic depiction of tears of the rotator
cuff: benefit of abduction and
external rotation of the arm. Radiology. 1994; 192(3):851-856.
4. Lee SY, Lee JK. Horizontal
component of partial-thickness
tears of rotator cuff: imaging
characteristics and comparison
of ABER view with oblique
coronal view at MR arthrography initial results. Radiology.
2002; 224(2):470-476.
7. de Jesus JO, Parker L, Frangos
AJ, Nazarian LN. Accuracy of
MRI, MR arthrography, and ultrasound in the diagnosis of rotator cuff tears: a meta-analysis.
AJR Am J Roentgenol. 2009;
192(6):1701-1707.
5. Choi JA, Suh SI, Kim BH, et
al. Comparison between conventional MR arthrography and
abduction and external rotation
MR arthrography in revealing
tears of the antero-inferior glenoid labrum. Korean J Radiol.
2001; 2(4):216-221.
8. Schreinemachers SA, van der
Hulst VP, Willems WJ, Bipat S,
van der Woude HJ. Detection
of partial-thickness supraspinatus tendon tears: is a single
direct MR arthrography series
in ABER position as accurate
as conventional MR arthrography? Skeletal Radiol. 2009;
38(10):967-975.
6. Herold T, Bachthaler M, Hamer
OW, et al. Indirect MR arthrography of the shoulder: use of
abduction and external rotation
to detect full- and partial-thickness tears of the supraspinatus tendon. Radiology. 2006;
240(1):152-160.
9. Saleem AM, Lee JK, Novak
LM. Usefulness of the abduction and external rotation views
in shoulder MR arthrography.
AJR Am J Roentgenol. 2008;
191(4):1024-1030.
Section Editor: Steven F. Harwin, MD
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