DOI:10.2214/AJR.07.3251
AJR 2008; 190:1481-1486
© American Roentgen Ray Society
Pubic Ramus Radiolucencies in Infants: The Good, the Bad, and the Indeterminate
Jeannette M. Perez-Rossello1,
Susan A. Connolly1,2,
Alice W. Newton1,2,
Michael Thomason3,
Carole Jenny4,
Naomi F. Sugar5 and
Paul K. Kleinman1
1 Department of Radiology, Children's Hospital Boston, 300 Longwood Ave., Boston
MA 02115.
2 Department of Radiology, Massachusetts General Hospital, Boston MA.
3 Department of Radiology Services, Greenville Memorial Medical Center,
Greenville SC.
4 Child Protection Program, Hasbro Children's Hospital, Providence RI.
5 Department of Pediatrics, Harborview Medical Center, Seattle WA.
Received October 2, 2007;
accepted after revision December 13, 2007.
Address correspondence to J. M. Perez-Rossello
(jeannette.perez-rossello{at}childrens.harvard.edu).
Abstract
OBJECTIVE. The purpose of this study was to examine imaging findings
that differentiate inflicted injuries from developmental variants of the
superior pubic ramus in healthy and abused infants.
CONCLUSION. A superior pubic ramus fracture and a developmental
variant can be difficult to differentiate radiographically. A smoothly
marginated vertical radiolucency of the superior pubic ramus detected without
other features suggesting infant abuse should not be interpreted as a
fracture.
Keywords: child abuse • fractures • infants • pelvis • pubic bone
Introduction
Infant abuse can result in life-threatening injuries. A rigorous
approach to skeletal imaging is essential in optimizing detection. Certain
findings, such as rib fractures and classic metaphyseal lesions, have high
specificity for abuse. Other radiographic findings are less specific, and care
must be taken to avoid an inappropriate diagnosis of abuse. Pelvic fractures
in the absence of severe accidental trauma should raise strong suspicion of
maltreatment.
Most cases of pelvic injury described in the literature fall into two
groups: injuries to infants, in which the findings tend to be subtle, and
injuries to toddlers and older children, in which massive blunt trauma, sexual
abuse, or both are implicated
[1-8].
Injuries to older children tend to be gross and varied in location, whereas
findings in infants typically involve the superior pubic ramus. In 1956,
Caffey and Madell [9] detailed
the anatomic variants in ossification of the superior pubic ramus in infancy
(Fig. 1). On conventional
radiographs, these normal anatomic variants can be indistinguishable from a
fracture. The purpose of this article is to examine the imaging findings that
enable critical differentiation between inflicted injuries and developmental
variants of the superior pubic rami in abused and nonabused infants.
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Fig. 1 —Drawing shows multiple ossification centers of superior pubic
rami (arrows) as described by Caffey and Madell. (Reprinted with
permission from Caffey J, Madell SH. Ossification of the pubic bones at birth.
Radiology 1956; 67:346-350
[9])
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Materials and Methods
A vertical radiolucency through the superior pubic ramus was found in 14
infants at five institutions. In seven infants, the radiolucency was
identified during evaluations for suspected physical abuse. A review of
teaching case files disclosed an additional six instances of a similar
radiolucency discovered incidentally during an evaluation for assorted
nontraumatic indications. In the case of the 14th infant, viral myocarditis
and a superior pubic ramus radiolucency were detected on post-mortem
radiographs, and the region was inspected at autopsy. The medical records were
reviewed to obtain demographic information, clinical history, and outcome data
on each infant. The images were reviewed jointly by two board-certified
pediatric radiologists (30 and 5 years of experience), who in consensus
characterized the radiolucency in the superior pubic ramus and identified any
associated skeletal injuries.
The criterion for a developmental variant of the superior pubic ramus was
based on Caffey and Madell's original description
[9]. This criterion was the
presence of a single or double radiolucent strip with or without marginal
sclerosis passing vertically through the approximate center of the superior
pubic ramus. The criteria for fracture were oblique irregular superior pubic
ramus radiolucency with surrounding sclerosis, displacement of fragments, and
presence of other fractures involving the pelvis or hips. All other superior
pubic ramus radiolucencies were considered indeterminate. The diagnosis of
abuse was based on the presence of multiple high-specificity fractures, such
as classic metaphyseal lesions and rib fractures, and intracranial injuries
commonly seen with abuse, particularly subdural hematoma. The institutional
review board approved this retrospective review. The study was HIPAA
compliant, and informed consent was not required.
Results
Clinical, imaging, and outcome data on the 14 cases reviewed are summarized
in Table 1. In four (29%) of
the cases the findings were classified as normal variants, in three (21%) as
fractures, and in seven (50%) as indeterminate. The mean age of the seven
abused infants was 3 months (range, 1.5-7 months). All seven infants had
injury patterns highly specific for infant abuse. Five (71%) of the infants
had multiple rib fractures, and all seven had classic metaphyseal lesions.
Three (43%) of the infants had subdural hematomas associated with retinal
hemorrhages. The pubic ramus radiolucencies were bilateral in two (29%) of the
patients and unilateral on the left in five (71%).
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Fig. 2A —1.5-month-old abused male infant with normal variants (case
1). Oblique (A) and anteroposterior (B) radiographs of pelvis
reveal regular, sharply marginated vertical radiolucencies (arrows)
in both superior pubic rami.
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Fig. 2B —1.5-month-old abused male infant with normal variants (case
1). Oblique (A) and anteroposterior (B) radiographs of pelvis
reveal regular, sharply marginated vertical radiolucencies (arrows)
in both superior pubic rami.
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Three (43%) of the abused infants had superior pubic ramus radiolucencies
consistent with developmental variants (Figs.
2A,
2B,
3, and
4); three (43%) had findings
consistent with fractures (Figs.
5,
6, and
7); and one (14%) had
indeterminate findings (Figs.
8A and
8B). The infant in case 1 had
bi-lateral smoothly marginated vertical radiolucencies in the superior pubic
rami. Further evaluation of the pubic rami showed no radionuclide uptake on
bone scan and no abnormal signal intensity on MRI. Despite the history of
abuse, the bilaterality and imaging characteristics of the radiolucencies were
most consistent with normal anatomic variants (Figs.
2A and
2B). The infants in cases 2 and
3 had two vertical radiolucencies in the left superior pubic ramus consistent
with multiple ossification centers present in the setting of abuse
(Fig. 3). The infants in cases
4 and 5 had irregular oblique radiolucencies in the superior pubic ramus
consistent with fractures (Figs.
5 and
6). They also had additional
evidence of substantial injury to the pelvis and hips. The infant in case 4
had a Salter-Harris type II fracture of the right proximal femur, and the
infant in case 5 had a bilateral proximal femoral classic metaphyseal lesion.
The infant in case 6 also had an oblique radiolucency of the left superior
pubic ramus with separation of the osseous margins consistent with a fracture
(Fig. 7) and a classic
metaphyseal lesion of the ipsilateral distal tibia. The infant in case 7 had a
radiolucency in the left superior pubic ramus and increased sclerosis on
follow-up radiography. Although this pattern was suggestive of a fracture, a
developmental variant could not be completely ruled out; hence the finding was
indeterminate (Figs. 8A and
8B).
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Fig. 4 —5-month-old female infant with normal variants (case 14).
Postmortem anteroposterior radiograph of pelvis shows radiolucency with
marginal sclerosis (arrow) in left superior pubic ramus. Autopsy
showed no evidence of trauma to superior pubic ramus.
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Fig. 5 —3-month-old abused male infant with fractures (case 4).
Anteroposterior radiograph of pelvis shows bilateral irregular oblique
superior pubic ramus radiolucencies with marginal sclerosis (arrows)
consistent with fractures. Healing Salter-Harris type II injury to right
proximal femur is evident.
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Fig. 6 —2.5-month-old abused female infant with fracture (case 5).
Anteroposterior radiograph of pelvis shows oblique radiolucency with marginal
sclerosis (black arrow) in left superior pubic ramus consistent with
fracture. Bilateral proximal femoral classic metaphyseal lesions (white
arrows) and right proximal femoral subperiosteal new bone formation
(arrowhead) are evident.
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Fig. 7 —1.5-month-old abused male infant with fracture (case 6).
Anteroposterior radiograph of pelvis shows oblique radiolucency in left
superior pubic ramus consistent with fracture. Superior fracture margins are
slightly displaced (arrow).
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Fig. 8A —3-month-old abused female infant with indeterminate findings
(case 7). Initial (A) and 2-week follow-up (B) anteroposterior
radiographs of left hemipelvis show vertical radiolucency with increased
sclerosis (arrow) on follow-up image.
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Fig. 8B —3-month-old abused female infant with indeterminate findings
(case 7). Initial (A) and 2-week follow-up (B) anteroposterior
radiographs of left hemipelvis show vertical radiolucency with increased
sclerosis (arrow) on follow-up image.
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A radiolucency in the superior pubic ramus was found incidentally in three
infants, prompting further evaluation. The infant in case 8 underwent imaging
of the chest and abdomen for evaluation of a cough. A radiolucency in the left
superior pubic ramus with marginal sclerosis was identified. A normal skeletal
survey was performed, and findings of a social service evaluation did not
support abuse. The infant in case 9 had been treated for right hip dysplasia
in a harness. A radiograph performed when the infant was 5 months old showed
radiolucency in a widened left superior pubic ramus
(Fig. 9). A bone scan showed
increased uptake in the left superior pubic ramus but no other abnormalities.
The infant in case 10 presented with clinical findings of intussusception, and
a mildly sclerotic superior pubic ramus radiolucency was found on an abdominal
radiograph (Fig. 10). Findings
of a skeletal survey were normal, and air reduction of the intussusception was
successful. The findings in cases 8-10 were indeterminate.
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Fig. 9 —5-month-old female infant with indeterminate findings
undergoing evaluation for hip dysplasia (case 9). Anteroposterior radiograph
of pelvis reveals vertical radiolucency (arrow) in left superior
pubic ramus that completely resolved on follow-up images. Left superior pubic
ramus is wider than right.
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Fig. 10 —8.5-month-old male infant with indeterminate findings and
intussusception (case 10). Anteroposterior radiograph of pelvis shows vertical
radiolucency with marginal sclerosis (arrow) in left superior pubic
ramus.
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Vertical radiolucencies in the superior pubic ramus of three otherwise
healthy infants (cases 11-13) were found incidentally during voiding
cystourethrography (case 12) and upper gastrointestinal evaluation (cases 10
and 13). These indeterminate findings were considered unlikely to represent
fractures, and no further evaluation was performed. Finally, the infant in
case 14 experienced cardiopulmonary arrest secondary to viral myocarditis.
Postmortem radiography revealed a left superior pubic ramus vertical
radiolucency with adjacent sclerosis and no other fractures
(Fig. 4). At autopsy, no
hemorrhage or palpable abnormality in the region of the pubic bones was found.
On the basis of the imaging characteristics and no other evidence of trauma at
autopsy, the superior pubic ramus radiolucency was considered to represent a
normal variant.
Discussion
In 1956, Caffey and Madell
[9] reviewed the pelvic
radiographs of 1,286 infants and described the ossification patterns of the
superior pubic ramus. In that series, 1.8% of the infants had double and
occasionally triple ossification centers. Curiously, this distinctive normal
variant has received scant mention in the literature
[10]. Our findings draw
attention to this variant and illustrate the difficulties in differentiating
it from a pelvic fracture. On radiographs the ossification centers are
separated by a smoothly marginated vertical radiolucency in the midportion of
the superior pubic ramus. As ossification progresses, radiographs reveal
marginal sclerosis, and the radiolucent zone gradually ossifies, mimicking a
healing fracture. The ossification centers eventually fuse with no residual
evidence of a radiolucent line. The age at closure in the study by Caffey and
Madell was variable, in some cases as early as 5 months and in others as late
as 1 year.
Six patients in our series had follow-up radiographs that showed maturation
or resolution of the radiolucency. In the two cases in which the finding was
incidental, prompting follow-up, the degree of sclerosis associated with the
lesion was modest. In three of the abused infants, initial or follow-up
imaging showed substantial sclerosis around the pubic defects, suggesting
healing fracture in two infants and indeterminate findings in one. In one
abused infant in whom the finding was a normal variant, there was no change in
the radiolucencies on follow-up. However, because marginal sclerosis can be
seen around a maturing variant or an indeterminate radiolucency, confident
differentiation cannot be made on the basis of this finding alone.
Although it often plays a role in the evaluation of infant abuse, skeletal
scintigraphy did not prove particularly useful in the four infants in our
study who underwent scanning. In one abused infant with bilateral superior
pubic ramus radiolucencies, no corresponding radiotracer uptake was present,
suggesting a normal variant. In an abused infant with bilateral defects, only
mild bilateral symmetric uptake in the pubic rami was detected. However, in
one infant with incidentally detected radiolucency in the pubic bone, there
was corresponding radiotracer uptake. Although this uptake can indicate a
healing fracture, increased radiotracer activity associated with a fusing
ossification center may also explain the finding. Moreover, increased
radionuclide uptake can occur with the active mineralization that precedes
normal growth plate closure, such as at the ischiopubic synchondrosis
[11]. Thus the presence of
increased uptake as found in our cases was an indeterminate finding.
Is there a radiographic finding that enables reliable differentiation of a
fracture from a normal variant? The normal patterns described by Caffey and
Madell [9] consisted of a
smoothly marginated vertical radiolucency coursing at a right angle to the
long axis of the superior pubic ramus. In our study, when bi-lateral, the
findings were relatively symmetric. In instances in which the findings were
incidental, all of the radiolucencies were vertical. In three cases of abuse,
the vertical bands were smoothly marginated, and in two a double radiolucency
pattern was consistent with normal variants. In three abused infants, the
defects were obliquely oriented with respect to the long axis of the pubic
ramus. Callus formation was evident along the superior and inferior margins of
the radiolucencies, consistent with healing fractures. Two of these abused
infants had hip fractures.
Fifty percent of our cases lacked the diagnostic features of either
fracture or normal variant as described by Caffey and Madell
[9] and were not confidently
classified. It is notable that in the three cases in which the incidentally
identified superior pubic ramus radiolucencies prompted further evaluation
(skeletal survey in two cases, bone scan in one case), no skeletal
abnormalities were found. Although the findings in these cases were
indeterminate, the absence of other evidence of osseous injury strongly
suggests that these superior pubic ramus radiolucencies were normal
variants.
The principal limitation of the study was its retrospective method and use
of a heterogeneous study group of cases drawn from five institutions. Imaging
protocols were not standardized, and follow-up was not always possible. This
approach, however, did allow review of a sizable number of cases with and
without other features of abuse from which reasonable conclusions could be
drawn.
Three of the infants in our study who had incidental findings of vertical
radiolucencies in the superior pubic ramus underwent unnecessary imaging
evaluation for other fractures. In one of these cases, child protection and
department of social services referrals were made because abuse was suspected.
In the cases of the seven abused infants, the diagnosis of abuse was
unaffected by the pelvic finding. From a forensic point of view, how-ever, it
is essential that physicians accurately characterize all pertinent findings in
cases of suspected child abuse to facilitate appropriate consideration in all
legal proceedings.
The normal developmental variant of the superior pubic ramus originally
described by Caffey and Madell
[9] is often difficult to
differentiate from a fracture on radiographs. The most reliable indicators of
osseous injury are a fracture line that courses at an obliquity to the long
axis of the superior pubic ramus, extensive callus, displacement of osseous
fragments, and evidence of additional injuries around the pelvis. A smoothly
marginated vertical radiolucency of the superior pubic ramus in an infant who
has no clinical or other imaging signs suggesting trauma should not be
interpreted as a fracture. More-over, the presence of marginal sclerosis does
not exclude a variant, even in the context of other evidence of abuse.
Acknowledgments
We are grateful to Rhonda Johnson and Nancy Drinan for their suggestions
and in-sightful comments.
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Abstract
Introduction
