DOI:10.2214/AJR.07.3304
AJR 2008; 190:W240-W241
© American Roentgen Ray Society
Vertebral Pseudolesion on Lateral Chest Radiograph
Ian Hammond1,
Adnan Sheikh1,
Pasteur Rasuli1 and
Carolina A. Souza1
1 All authors: Department of Radiology and Diagnostic Imaging, The Ottawa
Hospital, 501 Smyth Rd., Ottawa, ON, Canada K1H 8L6.
Received October 14, 2007;
accepted after revision October 29, 2007.
Address correspondence to A. Sheikh
(asheikh{at}ottawahospital.on.ca).
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Abstract
OBJECTIVE. The purpose of this study was to describe and explain the
basis for the lateral chest radiographic finding of a pseudolesion simulating
a sclerotic vertebral lesion.
CONCLUSION. Superimposition of the scapula on the upper thoracic
spine causes a vertebral pseudolesion that simulates a sclerotic lesion.
Keywords: chest radiography • pseudolesion • scapula
Introduction
Because of anatomic variations or superimposition of normal structures to
form a composite opacity that mimics a lesion, normal anatomic structures can
simulate pathologic processes on plain radiographs. As stated by Keats and
Anderson [1],
"overdiagnosis of a normal variation as evidence of pathology may be
more serious than omission, and may lead to needless and harmful
therapy." We describe a pseudolesion occasionally seen on lateral chest
radiographs of the upper thoracic spine that results from a particular
position of the scapula at radiographic exposure. This vertebral pseudolesion
can be misinterpreted as a sclerotic lesion of a vertebral body and has not
been described in the literature, to our knowledge.
Case Report
The lateral chest radiograph of a 57-year-old woman with breast cancer
showed an apparently sclerotic lesion in the T3 vertebral body suggestive of
osteoblastic metastasis. No relevant abnormality was seen on the corresponding
frontal view (Figs. 1A and
1B). A whole-body nuclear bone
scan showed no abnormalities in the thoracic spine suggesting metastatic
disease. Additional cases of suspicious sclerotic lesion at this location were
seen by the radiologists involved in this study in the following months and
were of particular concern in patients with known malignancy. To explain the
origin of this pseudolesion, we observed the motion of the shoulder girdle in
the lateral projection of a fluoroscopic examination of a healthy 60-year-old
volunteer. The vertebral pseudolesion was reproduced and appeared to be
secondary to superimposition of the scapula over the vertebral body
(Fig. 2). Bilateral
disarticulated scapulae and a thoracic spine were positioned, and radiographs
were obtained with the scapula in different projections to determine the
anatomic basis for the vertebral pseudolesion (Figs.
3A and
3B).
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Fig. 1B —57-year-old woman with breast cancer. Frontal chest
radiograph shows no abnormality at level of upper thoracic spine. Metallic
clips from previous axillary nodal dissection are evident.
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Fig. 2 —60-year-old healthy male volunteer. Target fluoroscopic image
in lateral projection shows concave portion of superimposed scapula (thick
arrow) is immediately posterior to anterior margin of vertebral body
(thin arrow).
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Fig. 3A —Disarticulated scapulae and thoracic spine of skeleton
positioned to reproduce vertebral pseudolesion. Schematic (A) and
radiograph (B) show concavity of scapular neck as it leads to scapular
spine is responsible for arcuate line that forms anterior margin of vertebral
pseudolesion (shading, A). Projection of magnified scapula (B)
enhances pseudolesion causing apparent sclerosis. A = nonmagnified scapula,
Gle = glenoid process, Cor = coracoid process, Acr = acromion of scapula.
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Fig. 3B —Disarticulated scapulae and thoracic spine of skeleton
positioned to reproduce vertebral pseudolesion. Schematic (A) and
radiograph (B) show concavity of scapular neck as it leads to scapular
spine is responsible for arcuate line that forms anterior margin of vertebral
pseudolesion (shading, A). Projection of magnified scapula (B)
enhances pseudolesion causing apparent sclerosis. A = nonmagnified scapula,
Gle = glenoid process, Cor = coracoid process, Acr = acromion of scapula.
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The inferior concave portion of the scapular spine (scapular neck) produced
the arcuate line that formed the anterior margin of the vertebral
pseudolesion. The feature that enhanced the visual impression of vertebral
sclerosis was the slightly concave anterior aspect of the structure, which
projected over the normal anterior margin of the vertebral body. Close
examination revealed that this arcuate margin lay in a position slightly
posterior to the true anterior surface of the vertebral body.
Discussion
A normal scapula is known to produce findings on chest radiographs that can
be mistaken for disease
[2–5].
Scapular motion, which has been shown to be a complex of three separate
motions, contributes significantly to shoulder mobility
[6]. When patients are
positioned for lateral chest radiographs, the humerus is typically abducted
and flexed forward, and the scapula is projected anterolaterally. Our
fluoroscopic observations of scapular motion in the lateral view confirmed
that at a certain point during humeral elevation, the scapula projects over
the thoracic spine and may cause the vertebral pseudolesion. The inferior
concave portion of the scapular spine (scapular neck) produces the arcuate
line that forms the anterior margin of the vertebral pseudolesion.
This pseudolesion is a relatively common finding on lateral chest
radiographs, but the exact incidence is unknown. In most cases, the scapular
density projects over the posterior aspect of the vertebral body and does not
cause confusion. Occasionally, the positioning of the scapula projecting over
the vertebral body results in increased opacity that simulates sclerosis.
Comparison with the corresponding spinal level on the posteroanterior view may
be enough to confirm normalcy. Misinterpretation can be particularly harmful
to patients with known malignancy, in whom metastatic disease would be
considered and lead to unnecessary diagnostic examinations. Radiologists
should be able to recognize a vertebral pseudolesion and prevent unnecessary
costs and radiation exposure.
Acknowledgments
We thank Vincent Gareau, Jordan Menzies, and the other radiology
technologists at the Ottawa Hospital for their help.
References
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Abstract
Introduction
