While many fractures in children are overt and easily recognized, others are subtle and often overlooked. Radiologists are less likely to miss such fractures if they know what these fractures look like and where they occur. This article presents the imaging findings and the use of comparative imaging views to help to eliminate missed fractures.
is a Professor of Radiology and Pediatrics and Director of
Pediatric Radiology at the University of Texas Medical Branch,
Long bone fractures are very common in infants and children, and
while many are overt and easily recognized, others are subtle and
often overlooked. However, radiologists are less likely to miss
these fractures if they know what these fractures look like and
where they occur. In addition, using comparative imaging views
further enhances the ability to detect these fractures so that
virtually none of them will be missed.
In assessing the involved extremity for a fracture, it is
important to assess the soft tissues (for swelling), the fat pads
(for joint fluid and edema), and then the bones. When comparative
views are used, edema is detected more readily and abnormalities of
the various fat pads occurring around the joints are well
visualized. A detailed discussion of these fat pads is beyond the
scope of this presentation; nonetheless, they are important,
because abnormality of the fat pads may indicate a bony injury.
Types of fractures
There are five basic types of fractures in infants and children,
all of which are often very subtle: 1) epiphyseal-metaphyseal
(Salter-Harris) injuries, 2) buckle (torus) fractures, 3) hairline
fractures, 4) plastic bending fractures, and 5) avulsion
In regard to epiphyseal-metaphyseal fractures, the most commonly
missed of these are the Salter-Harris I and II injuries, in which
there is minimal or no displacement of the epiphysis (Figures 1A
and B). These fractures, although most common in infants and
younger children, also occur in older children and adolescents
before the epiphyseal line has been completely obliterated (Figures
1C and D). Epiphyseal-metaphyseal fractures occur most frequently
in the wrist and ankle, with the knee and shoulder the next most
Buckle fractures also are common and result from axial loading
on an extremity (ie, falling on an outstretched arm). There are two
types of buckle fractures: the classic buckle fracture, in which
there is outward buckling of the cortex (Figures 2A and B); and the
angled buckle fracture, in which the cortex is merely angled
(Figure 2C). In the classic buckle fracture, axial loading is
almost pure and the resultant forces are distributed evenly across
the metaphysis. As a result, the trabeculae are crushed along the
fracture line (sclerosis) and the cortices at either end bulge
outwardly. In some cases, bilateral cortical bulging occurs, while
in other cases bulging is unilateral. With the angled buckle
fracture, in addition to axial loading, some other force (ie,
varus, valgus, hyperextension or hyperflexion) is also at play.
This other force tends to lateralize the forces across the
metaphysis, and rather than an outward cortical buckling fracture
occurring, an angled buckle fracture of the cortex occurs on one
side (Figure 2C). As opposed to the other type of buckle fracture,
which occurs a short distance from the epiphyseal line, the angled
buckle fracture occurs adjacent to the epiphyseal line. If forces
that produce the angled buckle fracture are more severe, a frank
Salter-Harris type II fracture results. Buckle fractures in general
most frequently occur in the wrist, ankle, and elbow. Thereafter,
they occur around the knee and the shoulder but much less
In the elbow, angled buckle fractures commonly occur in the
proximal radius (Figures 3A and B), while in the wrist they
commonly occur in the distal radius (Figures 3C and D). The most
prominent forces at play in elbow angled buckle fractures are axial
loading and valgus forces. In the wrist, the forces consist of
axial loading and hyperextension. Therefore, in the wrist, a buckle
fracture occurs posteriorly through the radius, while in the elbow
it occurs laterally. In the wrist, if hyperflexion is the other
force, an angled buckle fracture occurs anteriorly.
Another angled buckle fracture of the elbow occurs through the
distal humerus and can be quite subtle.
This fracture occurs both posteriorly (axial loading and
hyperflexion), and laterally from associated varus forces (Figure
4). The posterior angled fracture can also be detected with the
anterior humeral line.
This line is designed to pass along the anterior cortex of the
humerus and then intersect the capitellum. Normally it intersects
the capitellum through its posterior third, but when a plastic
bending-buckle fracture of the distal humerus occurs, the line
intersects the capitellum more anteriorly (Figures 4A and B).
Angled buckle fractures may also occur through the distal femur
with hyperextension of the knee, but they are much less common.
However, a special buckle fracture through the upper tibia occurs
with hyperextension of the knee. This type has recently has been
reported as another toddler's fracture.
With hyperextension forces applied to the upper tibia, there is
buckling of the anterior cortex and, at the same time, increased
concavity of the normal notch for the tibial tubercle (Figure 5).
In some cases, there is a visible associated transverse hairline
fracture and/or minimal cortical buckling manifest on the
anterioposterior view (see Figure 9). Finally, another commonly
missed buckle fracture occurs through the base of the first
metatarsal as a bunkbed fracture
Hairline fractures in infants and children also occur, but,
again, are more likely to occur at certain sites. In this regard,
the most common hairline fracture is the toddler's fracture.
In these cases there is a tibial spiral fracture involving the
tibial metaphysis and diaphysis, but only portions of the fracture
are seen on any given view. The findings with this fracture are
notoriously subtle (Figure 7). Other hairline fractures occur
through the ulna, both transverse and linear (Figure 8). The
tranverse fractures result from direct forces applied to the
posterior ulna, while the linear fractures result from twisting
forces exerted on the ulna as it is locked into the trochlear notch
These linear fractures are extremely subtle (Figures 8C and D).
Hairline fractures in the form of longitudal spiral fractures also
occur in the small bones of the hands and feet. In addition, subtle
transverse hairline fractures occur as part of the hyperextension
upper-tibial toddler's fracture
Plastic bending fractures most commonly occur in the forearm,
involving the radius and ulna.
They are "cousins" of the greenstick fracture, and often both
fractures are present in a single extremity (Figure 10). Once
again, comparative views are essential for detection of these
fractures (Figure 11). After the radius and ulna, the most common
locations for a bending fracture are in the clavicle (Figure 12)
Finally, a few avulsion injuries should be considered. An
assortment of avulsion fractures can be seen in the younger child
and infant, despite the fact that avulsion fractures usually occur
around the hip in older children and adolescents. One of the most
commonly missed fractures of this type is the small avulsion
fracture that occurs off of the coronoid process of the ulna
(Figure 13A). This fracture is usually seen on the lateral view.
Medial epicondylar avulsion fractures may also be subtle (Figure
13B), and lateral condylar fractures may be extremely subtle
(Figure 13C). In such instances, nothing more than a small sliver
of cortex may be visible, minimally avulsed off of the humeral
metaphysis (Figure 13D).
Childhood fractures are a common occurrence. Most are overt and
are easily detected. However, many are subtle and can be
overlooked. The key to avoiding missing these fractures is to know
where they occur and what they look like.