AJR 2002; 178:413-418
© American Roentgen Ray Society
Elbow Effusions in Trauma in Adults and Children
Is There an Occult Fracture?
Nancy M. Major1 and
Steven T. Crawford1,2
1
Department of Radiology, Duke University Medical Center, Erwin Rd., Box 3808,
Durham, NC 27710.
2
Present address: Mallinckrodt Institute of Radiology, 510 S. Kingshighway
Blvd., St. Louis, MO 63110.
Received July 3, 2001;
accepted after revision August 21, 2001.
Address correspondence to N. M. Major.
Abstract
OBJECTIVE. The purpose of this study was to evaluate whether a
detectable abnormality was present on MR imaging without a visible fracture on
conventional radiography in the setting of trauma. A recent retrospective
study based on the presence or absence of periosteal reaction on follow-up
radiographs concluded that fractures were not always present. The
discrepancies in the literature over the usefulness of joint effusions as an
indicator of fracture caused us to evaluate whether fractures were present
more often than identified by conventional radiography. To do this, we used MR
imaging.
MATERIALS AND METHODS. Thirteen consecutive patients (age range,
4-80 years; seven children and six adults), whose posttrauma elbow radiographs
showed an effusion but no fracture, underwent screening MR imaging.
RESULTS. All patients showed bone marrow edema. Four of the seven
children had fractures on screening MR imaging, and all adults had some
identifiable fractures.
CONCLUSION. Preliminary data using screening MR imaging suggests
that an occult fracture usually is present in the setting of effusion without
radiographically visualized fracture.
Introduction
Elbow effusions are seen on lateral radiographs by the presence of the fat
pad sign. This was first described by Norell in 1954
[1]. These fat pads can be
elevated by the presence of fluid in the joint caused by an acute
fracture.
We wondered how often an occult fracture was present. For years, residents
were taught that elbow effusions without a visible fracture are synonymous
with an occult fracture in the setting of trauma. Indeed, multiple articles
have indicated a strong relationship between an occult fracture and a joint
effusion
[2,3,4,5].
In 1984, Swischuk et al. [6]
disputed this association, and more recently, the relationship between an
occult fracture and a joint effusion has come into question in a retrospective
study based on the presence or absence of periosteal reaction on follow-up
radiographs [7]. Here, the
authors found a prevalence of only 15% and 17%, respectively. A recent
prospective study, again based on follow-up radiographs, showed that 76% of
patients had evidence of a fracture
[8]. With this wide variation
of data, the usefulness of the posterior fat pad sign has come into question.
The purpose of our study is to evaluate the presence of an occult fracture
using screening MR imaging as the standard for fracture detection in both the
pediatric and adult populations.
Materials and Methods
Thirteen consecutive patients (seven children and six adults) were imaged
prospectively over a 5-month interval. The age range was 4-80 years. The
patients were selected consecutively and included in the study when
posttraumatic elbow radiographs from the emergency department showed an
effusion but no visible fracture. The patients underwent screening MR imaging.
The radiographs obtained in the emergency department consisted of frontal and
lateral views and a radial head view of the elbow obtained in the standard
fashion. The emergency department radiology resident, a senior radiology
resident, and a musculoskeletal radiologist reviewed the radiographs. A
patient was included in the study when an effusion was present but no fracture
was identified by any of the three radiologists. The mean time between the
injury and the MR imaging was 3 days (range, 0-6 days). MR imaging was
performed using a 1.5-T Signa scanner (General Electric Medical Systems,
Milwaukee, WI), and a flexible coil (send-receive) T2-weighted fast spin-echo
image with fat suppression (TR/effective TE, 3500/65; slice thickness, 4 mm;
interslice gap, 0.4 mm; excitations, 2; matrix, 256 x 192) was obtained
in the coronal plane (parallel to the epicondyles). The field of view included
the distal humerus to the proximal radius and ulna. In one patient, an
additional T1-weighted coronal image (TR/TE, 600/13) was obtained
inadvertently. Routine elbow MR imaging was not used because the purpose of
the study was to assess the presence of an injury. We felt this could be
addressed quickly with a marrow-sensitive sequence. The musculoskeletal
radiologists and the senior resident reviewed the MR images in consensus. A
fracture was defined by the presence of focal linear low signal intensity
surrounded by high signal intensity or disruption of the cortex. A contusion
was defined as high signal intensity without a visible fracture line.
Results
All patients were noted to have a joint effusion on MR imaging. Of the
pediatric patients, two showed Salter-Harris Type III fractures of the
epicondyle; one, Salter-Harris Type I fracture of the medial epicondyle (Fig.
1A,1B,1C);
one, radial head fracture (Fig.
2A,2B,2C);
and three, bone contusions—one of the lateral epicondyle, one of the
radial head, and one in the supracondylar area
(Table 1). Therefore, 57% of
the pediatric patients studied had a fracture that was only seen as an
effusion on the initial radiographs. But all (100%) had a detectable injury as
evidenced by bone marrow edema.
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Fig. 1C. —5-year-old girl with fracture of medial epicondyle. Coronal
fast spin-echo fat-suppressed T2-weighted MR image (TR/effective TE, 3500/65)
shows high signal intensity in trochlea compatible with contusion (large
arrow). Patient also has physeal injury that corresponds to Salter-Harris
Type I fracture as shown by focus of high signal intensity seen along physis
(small arrows).
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Fig. 2B. —10-year-old girl with radial head fracture. Coronal fast
spin-echo fat-suppressed T2-weighted MR image (TR/effective TE, 3500/65) shows
radial head fracture as evidenced by cortical disruption (arrow) and
surrounding bone marrow edema.
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Three of the six adult patients had osteochondral fractures, two in the
capitellum (Fig.
3A,3B),
and the third in the radial head (Fig.
4A,4B,4C).
Two of these patients showed a loose body in the joint. The remaining adult
patients showed a radial head fracture (Fig.
5A,5B)
and a nondisplaced medial epicondyle avulsion and a coronoid process fracture
with considerable extensor tendon complex injury from lateral epicondyle that
required additional therapy (Fig.
6A,6B)
(Table 1). All of the adult
patients had radiographically occult fractures as seen by MR imaging.
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Fig. 3B. —80-year-old man with osteochondral fracture in capitellum.
Coronal fast spin-echo fat-suppressed T2-weighted MR image (TR/effective TE,
3500/65) shows focal cartilage defect in capitellum with underlying marrow
high signal intensity, consistent with osteochondral fracture
(arrow). Defect should not be confused with
"pseudodefect" of capitellum because abnormality is too anterior,
and high signal intensity present around lesion would not be seen. Note
remainder of images determined high signal intensity in radial shaft to be
residual red marrow.
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Fig. 4B. —34-year-old man with osteochondral fracture in radial head.
T1-weighted coronal spin-echo MR image (TR/TE, 600/13) shows focal cartilage
defect in radial head with surrounding marrow T1 shortening consistent with
osteochondral fracture (arrow).
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Fig. 4C. —34-year-old man with osteochondral fracture in radial head.
Coronal fast spin-echo fat-suppressed T2-weighted MR image (TR/effective TE,
3500/65) shows loose body in joint space from previously described
osteochondral defect (arrow). Bone marrow edema is present in radial
head.
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Fig. 5B. —26-year-old man with radial head fracture. Coronal fast
spin-echo fat-suppressed T2-weighted MR image (TR/effective TE, 3500/65)
reveals radial head fracture shown by linear low signal intensity involving
medial cortex of radial head (arrows) surrounded by bone marrow
edema. High signal intensity in proximal ulna represents partial volume
averaging with joint fluid.
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Fig. 6A. —65-year-old man with nondisplaced medial epicondyle avulsion
and coronoid process fracture with extensor tendon complex injury from lateral
epicondyle. Anteroposterior radiograph shows no evidence of fracture.
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Fig. 6B. —65-year-old man with nondisplaced medial epicondyle avulsion
and coronoid process fracture with extensor tendon complex injury from lateral
epicondyle. Coronal fast spin-echo fat-suppressed T2-weighted MR image
(TR/effective TE, 3500/65) shows high signal at olecranon process (small
arrow). In addition, bone marrow edema is seen in lateral epicondyle
(large arrow). Common tendon of wrist-hand extensor-supinator complex
has been avulsed from its origin (curved arrow).
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Ten (77%) of the 13 patients had fractures that were present on the MR
image that were not seen on the initial radiographs. Thirteen of the 13
patients showed bone marrow edema indicative of an injury.
Discussion
For many years, the fat pad sign has been used as an indication of an
occult fracture. The posterior fat pad sign has been reported as a reliable
sign of an elbow joint effusion
[1,2,3,
5]. However, the presumed
incidence of a fracture has varied widely in both the radiologic and
orthopedic literature. Numerous studies have evaluated for fractures
retrospectively, using conventional radiographic follow-up to determine the
presence of a fracture
[6,7,8,9,10,11].
Our goal was to determine the presence of an injury versus a fracture of the
elbow using the gold standard of a marrow-sensitive sequence (fast spin-echo
with fat suppression) after identifying a joint effusion on conventional
radiography without a visible fracture noted by any of the three
radiologists.
We chose fast spin-echo with fat suppression as the sequence because of the
increased conspicuity of bone marrow edema seen with this sequence. We found
that four pediatric patients and six adult patients had fractures seen on the
MR images that were not seen on the initial radiographs. Ten (77%) of the 13
patients had fractures that were seen on the MR imaging follow-up, and all
patients had bone marrow edema. In other words, all patients had an abnormal
finding to explain the presence of a joint effusion. In retrospect, the
results of the MR imaging follow-up confirmed that none of the fractures were
identified on the radiographs.
One explanation for the higher incidence of fracture in our study compared
with other reports is that the sensitivity of MR imaging is much greater than
that of conventional radiography. The discrepancy between the initial studies
[2,3,4]
that stated a high incidence of occult fracture and the more recent studies
that dispute this claim [2,
7,
9,
10] has been previously
discussed [8] and is likely due
to improvements in radiographic technique, which allows better detection of
the fractures. Only a single layer of periosteum is within the joint capsule
that can produce periosteal reaction at the edge of the joint. Therefore,
periosteal reaction can be difficult to identify on conventional radiographs,
making conventional radiography less sensitive than MR imaging for an accurate
diagnosis.
The current treatment for occult fractures about the elbow is posterior
splinting. Two of the patients (15%) in our study, both adults, required
surgery instead of posterior splinting
[12]. One patient required
repair of the extensor tendon complex and another required removal of a loose
body after an osteochondral fracture. Neither of these abnormalities was
suspected on conventional radiography. The findings at surgery were consistent
with the findings on MR imaging. The two patients with osteochondral lesions
had no history of prior elbow trauma. The osteochondral lesions were felt to
be acute, given the presentation of trauma and the findings of edema and a
loose body. The remainder of the patients did well with conservative treatment
(posterior splinting). Previous reports have stated that even if a fracture
was present on follow-up radiographs, the clinical treatment was not altered
[12].
Griffith et al. [13]
revealed a variety of bone and soft-tissue injuries in the pediatric
population with MR imaging. Despite the information provided by the study, no
change in treatment or clinical outcome occurred. We have the same conclusion
in our pediatric population, although our study included a smaller number of
patients.
Shortcomings of our study include the small number of patients. The design
of this study was to investigate whether an abnormality exists when an elbow
joint effusion is present in the setting of trauma and to refute the idea by
Donnelly et al. [7]. Our study
was not designed to separate the pediatric population from the adult
population but rather to see what abnormalities might exist within each. The
screening protocol chosen was to enable detection of fractures and bone marrow
edema that would indicate injury. An additional shortcoming was the use of a
three-view conventional radiographic series to evaluate the elbow. Although
this is routine at our institution, four views are often obtained at other
institutions. Perhaps a fracture would be evident on the additional view.
In reviewing our data, children can have both supracondylar injuries (which
are usually felt to be the likely site of the abnormality) and radial head
injuries. Similarly, adults can sustain injuries to any of the bony structures
about the elbow joint (radial head is most often suspected). Although most
patients will be treated with a posterior splint and will go on to full
recovery, the presence of an osteochondral defect and possible loose body or
ligamentous injury may be the cause of continued pain or accelerated
degenerative changes if unrecognized.
In conclusion, our investigation using MR imaging, rather than previous
studies using findings on follow-up radiography, suggests that an occult
fracture usually is present in the setting of effusion without
radiographically visualized fracture. Indeed, all of the imaged patients had
intraarticular injury, which confirms the traditional teaching that occult
fractures or injuries are present.
Acknowledgments
We thank Mirjana Cudic for her assistance with preparation of this
manuscript.
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Abstract
Introduction
