AJR 2005; 184:969-974
© American Roentgen Ray Society
High-Resolution Sonography of the Rib: Can Fracture and Metastasis Be Differentiated?
Sang Hyun Paik1,
Myung Jin Chung2,
Jai Soung Park1,
Jin Mo Goo3 and
Jung-Gi Im3
1 Department of Radiology, Soonchunhyang University, Bucheon Hospital,
Gyeonggido, Korea.
2 Department of Radiology and Imaging Science, Sungkyunkwan University School od
Medicine, Samsung Medical Center, 50 Ilwon-dong, Kangnam-gu, Seoul
135–710, Korea.
3 Department of Radiology, Seoul National University College of Medicine, Seoul,
Korea.
Received April 7, 2004;
accepted after revision July 28, 2004.
Address correspondence to M. J. Chung
(chungmj{at}smc.samsung.co.kr).
Abstract
OBJECTIVE. Our aim was to evaluate whether high-resolution
sonography can provide additional information concerning rib lesions compared
with radiography or bone scintigraphy.
MATERIALS AND METHODS. Fifty-eight patients with high-uptake rib
lesions seen on bone scintigraphy were selected. Radiography and rib
high-resolution sonography were performed on these patients. High-resolution
sonography was performed using a linear 5–12 MHz transducer. By means of
clinical history, histopathologic examination, and follow-up observation,
these patients were classified into rib fracture (n = 37), rib
metastasis (n = 18), or unknown (n = 3) groups.
High-resolution sonography images of the 55 proven cases were reviewed for the
presence of five representative findings: cortical disruption, callus
formation, cortical deformity, mass, or bone destruction. The frequencies of
these findings were compared between the groups with fracture and
metastasis.
RESULTS. Rib lesions were matched by bone scintigraphy and
high-resolution sonography in 53 (96%) of 55 patients and by bone scintigraphy
and plain radiography in 23 (42%) of 55 patients. High-resolution sonography
revealed 17 (94%) of 18 patients with metastasis and 36 (97%) of 37 patients
with rib fractures. Metastatic lesions were seen as mass formation (n
= 13) and irregular bone destruction (n = 7) on high-resolution
sonography. Fracture was seen as cortical disruption with or without hematoma
(n = 17), callus formation (n = 9), or cortical deformity,
such as angling or stepping (n = 12).
CONCLUSION. High-resolution sonography of the ribs is a useful
method of characterizing rib lesions in patients who have hot-uptake lesions
on bone scintigraphy.
Introduction
Most physicians believe that sonography has limited use in chest disease.
Bone and air are physical disruptions to this technique because of the
absorption of sonography energy by bony structures and total reflection by air
[1–3].
Although the bony thorax and the presence of air in the lungs limit the
application of sonography, chest wall lesions can be depicted
[1]. Approximately 6–8%
of the time, malignant bone disease appears as a single focus rather than as
multiple foci on bone scintigraphy
[4]. The location of a solitary
bone abnormality on bone scintigraphy has a bearing on the probability that it
represents malignant disease
[5]. Among patients with a
known primary tumor, 17% of rib lesions and 80% of vertebral lesions revealed
on bone scintigraphy are malignant
[5]. In older patients or
patients in poor general condition, rib or costochondral fractures are easily
produced by minor trauma such as coughing, exercise, and nonrecalled
contusion. At the site of a single rib uptake on bone scintigraphy, it is very
difficult to differentiate metastasis and fracture either clinically or on
radiography.
We evaluated whether high-resolution sonography can give more information
concerning rib lesions than radiography or bone scintigraphy.
Materials and Methods
Between January 2002 and December 2002, 58 consecutive patients (35 men and
23 women; 22–88 years old; mean, 60.6 years old) who showed hot-uptake
rib lesions on radionuclide bone scintigraphy were included in this study.
Twenty-seven patients with malignancy, 17 patients with trauma history, and 14
patients with unexplained chest pain were included. Primary malignant lesions
(n = 27) were the following: lung cancer (n = 11),
hepatocellular carcinoma (n = 3), stomach cancer (n = 3),
breast cancer (n = 5), colon cancer (n = 2),
cholangiocarcinoma (n = 1), multiple myeloma (n = 1), and
laryngeal cancer (n = 1). Plain chest radiography and high-resolution
sonography were performed on these patients.
Chest radiography was performed in the anteroposterior and both oblique
lateral positions, with a computed radiographic imaging system (FCR-5000,
Fuji). Imaging plates 35 x 43 cm (ST-VN; Fuji), with a matrix
of 1,760 x 2,140 x 10 bits and a pixel size of 0.2 mm were used.
The radiograph was produced using the settings of 66 kVp, 200 mA, 35 msec, and
a 100-cm focus-detector distance. An antiscatter grid was included, and the
X-ray beam was collimated onto the patient's chest. The chest radiography
images were reviewed for the presence of three representative findings:
osteolytic bone destruction, osteoblastic change, or cortical disruption.
High-resolution sonography was performed with a 5-12–MHz linear array
sonography unit (ATL HDI 3000 and 5000; Philips Medical Systems). The
high-resolution sonography of the ribs and costal cartilage in the most
painful area was performed with the transducer aligned transversely (i.e.,
parallel to the long axis of the rib). The patients were then turned to a
lateral decubitus position. Thereafter, the entire length of each rib in the
affected area and above and below the rib was scanned from the costosternal to
the costovertebral junction. The high-resolution sonograms were reviewed for
the presence of five representative findings: cortical disruption (focal
interruption of the echogenic cortical line), callus formation (echogenic dump
with posterior shadow), cortical deformity (changed shape of echogenic
cortical line such as angulation or stepping), bone destruction (amorphous
irregular loss of cortical line), or mass.
Rib metastases were confirmed by percutaneous needle biopsy in four
patients. Other patients were confirmed as having rib fracture or rib
metastasis by consideration of clinical history and by follow-up observation
for more than 1 year. The frequencies of matched findings by the use of
high-resolution sonography were compared between the groups of fracture and
metastasis patients.
Results
Fifty-five patients were confirmed as having rib fracture (n = 37)
or rib metastasis (n = 18) by clinical history, histopathologic
examination, and follow-up observation. Three patients with unknown final
diagnosis were excluded. Eleven patients with history of malignancy showed a
solitary hot-uptake lesion on bone scintigraphy. Among them, six patients were
confirmed to have rib metastasis and other five were confirmed to have rib
fractures.
Rib lesions were matched on bone scintigraphy and high-resolution
sonography in 53 (96%) of 55 patients and on bone scintigraphy and radiography
in 23 (42%) of 55 patients (p < 0.001, McNemar test).
High-resolution sonography revealed 17 (94%) of 18 patients with metastasis
and 36 (97%) of 37 patients with rib fractures. Chest radiography revealed
seven (39%) of 18 patients with metastasis and 16 (43%) of 37 patients with
rib fractures. Chest radiography of patients with metastasis (n = 18)
revealed osteolytic bone destruction (n = 6; 33%), osteoblastic bone
change (n = 1; 6%) or a negative result (n = 11; 61%). Chest
radiography of patients with a fracture (n = 37) revealed cortical
disruption (n = 16; 43%) or a negative result (n = 21; 57%)
(Table 1). On high-resolution
sonography, metastases were seen as mass formation (n = 13) and
irregular bone destruction (n = 7) (Figs.
1A,
1B,
1C, and
1D). Fracture was seen as
cortical disruption with or without hematoma (n = 17), callus
formation (n = 9), or cortical deformity, such as angling or stepping
(n = 12) (Figs. 2A,
2B,
2C,
3A,
3B,
3C,
3D, and
Table 2). No finding was
observed on high-resolution sonography in metastasis (n = 1) (Figs.
4A,
4B, and
4C) and fracture (n =
1).
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Fig. 2C. —43-year-old man with trauma 10 days previously and confirmed
traumatic rib fracture. Sonogram shows cortical disruption (arrow)
and hematoma formation (arrowheads) on transverse and longitudinal
scans.
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Fig. 3C. —61-year-old woman with breast cancer and acute right chest pain.
Sonogram shows cortical disruption (arrow) with subtle hematoma
formation at 1 cm proximal to costochondral junction (arrowhead) on
panoramic view.
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Fig. 3D. —61-year-old woman with breast cancer and acute right chest pain.
Bone window setting of axial CT scan obtained 6 months after C shows
subtle sclerosis and angulation at costochondral junction of right seventh
rib, at which rib fracture was suspected (solid arrow), compared with
contralateral costochondral junction (open arrow). At close
observation, hot-uptake rib lesion on bone scintigraphy was confirmed to be
incidental rib fracture.
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Fig. 4C. —43-year-old man with colon cancer and multiple bone metastases. On
rib sonogram, no lesion is visualized. When metastatic lesion involves only
bone marrow, bone cortex can be intact. Sonography cannot transmit through
intact bony cortex. Thus, if there are multiple increased uptakes of
radionuclide on scintigraphy and negative results on rib sonography,
metastatic lesion is suggested.
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Discussion
The subjective clinical impression of the presence of a fracture is not a
reliable indication of fracture. In only 29% of cases in a previous study was
a fracture shown to be present, yet the clinician's subjective estimate of
fracture in all patients was 66%
[6].
High-resolution sonography can detect a fracture in six times as many
patients as radiography and will detect 10 times more fractures than
radiography [7]. Wischhofer et
al. [8] detected a fracture on
sonography in 16 of 21 subjects with suspected rib fracture and normal
findings on chest radiography. Subsequent bone scintigraphy in 11 of these
patients confirmed fractures in all of them and showed 14 additional
fractures. The anterior costochondral junction of the rib cage was the most
frequent fracture site, causing minor trauma in old or cachexic patients.
Therefore, care had to be taken in studying lesions around the anterior
costochondral junction of patients with known malignancy. Malghem et al.
[9] reported that costal
cartilage fracture was recognized by visualizing focal interruption in the
relatively high costal cartilage density on CT or in the linear echogenic
anterior margin of the hypoechogenic cartilages on sonography. CT findings of
costal cartilage fracture were significant displacement of the adjacent
segment, soft-tissue swelling, calcifications surrounding the fracture sites,
and a thin area with gas density within the cartilage cleft. On sonography,
the cartilage was less echogenic than the adjacent muscle and was delineated
by a thin echogenic anterior margin. Thus, sonography may be useful in
patients with unexplained chest pain and no history of trauma, in whom a
cough, fracture, or other missed fracture is suspected clinically, although
the chest radiography shows no findings indicating a fracture.
On sonography, the patient indicates the site of pain and the examiner
obtains a crosssectional image of the region in two planes, with the image
closely following the course of the ribs. Some typical sonography findings of
rib fracture are gap, step, dislocation, hematoma, and minimal concomitant
pleural effusion or even pneumothorax
[1]. Minute dislocation and
fissures are visible at the traumatized point by a reverberation artifact,
known as the so-called "light-house phenomenon" or "chimney
phenomenon" [10]. In the
first 2–3 weeks after rib fractures, an increased number of small echoes
may be observed in the fracture space and then later by small acoustic shadows
appear corresponding to calcifications. Finally, after a few months, only a
small bump in the space line of the rib indicates the remaining callus
[11].
If bone scintigraphy showed an increased uptake in the rib cage and
sonographic findings for the rib were negative, traumatic fracture could be
ruled out. This suggests metastasis, which requires further evaluation. If
bone scintigraphy showed single or multiple increased uptake lesions in the
ribs of patients with malignancies, the determination of benign or metastatic
lesions became difficult. Most patients with malignancies are old and in poor
general condition. These patients often have fragile ribs, easily damaged by
minor trauma such as a cough or stretching. Radiographs are not sensitive
enough in these situations because osteopenia can mask the fracture and an
elevated diaphragm causes a poorly delineated rib margin. In these cases,
sonography is superior for a number of reasons, such as approach,
magnification, high resolution, and use of the Doppler method. High-resolution
sonography characterizes hot-uptake rib lesions on bone scintigraphy and can
differentiate a benign simple fracture or metastatic pathologic fracture.
There were several limitations in this study. First, the sonography
approach was limited at the area of the lateral arc of the first to fourth rib
because of shielding by the humerus and scapula. The evaluation of the
costovertebral joint was also limited. Second, there is a possibility of
misdiagnosing a pathologic fracture with minimal cortical destruction due to
metastasis as an osteoporotic fracture. In this study, we experienced a
patient who had multiple myeloma and showed multiple rib lesions suggesting
pathologic fracture. Unfortunately, he was not confirmed to have metastasis
and was excluded from the analysis.
In conclusion, high-resolution sonography of the rib is a useful method in
detecting and characterizing rib lesions in those patients who have hot-uptake
lesions revealed on bone scintigraphy. Thus, we recommend high-resolution
sonography in patients with underlying primary malignancy but with uncertain
possibility of rib metastasis.
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Abstract
Introduction
