Test Your Skill In Reading Pediatric Elbows
Radiology Cases in Pediatric Emergency Medicine
Volume 2, Case 18
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
     Pediatric elbow radiographs can be difficult to 
interpret unless one adheres to a methodical means of 
looking for specific abnormalities.  Unlike other long 
bones, bony injuries of the elbow are not obvious.  
However, by following a few simple rules, the 
identification of these injuries need not be difficult.
     In Volume 1 of this text disk, several cases were 
reviewed to illustrate some of the methods to 
radiographically diagnose fractures in the elbow region.  
You may want to review these cases before proceeding 
with the interpretation of the current series of elbow 
radiographs.
     Volume 1, Case 11:  Elbow Ossification Centers in a 
Child.  This case discusses the sequence that elbow 
ossification centers appear.  CRITOE is the mnemonic 
used to remember this sequence:  Capitellum, radial 
head, internal epicondyle, trochlea, olecranon, and 
external epicondyle.
     Volume 1, Case 12:  Radiographic Examination of 
the Elbow - The Hourglass Sign.  This case discusses 
the appearance of fat pads, supracondylar fractures, 
and the importance of obtaining a true lateral film.
     Volume 1, Case 15:  Monteggia's Injury.  This case 
discusses the association of an ulna fracture with a 
radial head dislocation.  The radial head should point 
directly at the capitellum in all views.
     Volume 1, Case 17:  Elbow Sprain in a Child.  This 
case describes the difficulty in appreciating radial head 
fractures.
     Volume 1, Case 19:  Swollen Elbow with a Normal 
X-ray.  This case describes some fractures that are 
difficult to see on conventional views of the elbow.  
When a fracture injury is clinically obvious, but the 
radiographs fail to reveal a fracture, one should still be 
highly suspicious of an occult fracture.

Summary of Elbow Radiographic Examination:
A.  Examine the lateral view first.
     1.  Examine the anterior fat pad.  The presence of 
an anterior fat pad is normal.  It should be small and 
appear to be flat against the anterior surface of the 
humerus.  If it is large or it appears to be triangular in 
shape as if its lower tip is being displaced upwards, this 
indicates the presence of an elbow joint effusion.  Joint 
effusions are highly correlated with visible fractures and 
occult fractures.
     2.  Look for the presence of a posterior fat pad.  A 
lucency posterior to the humerus at the olecranon fossa 
(a posterior fat pad) is always an abnormal sign and 
indicates the presence of an elbow joint effusion.
     3.  Examine the anterior humeral line.  Draw a line 
down the anterior border of the humerus.  This line 
should bisect the capitellum.  If this line fails to bisect 
the capitellum, this indicates the presence of a fracture 
in the supracondylar region displacing the capitellum 
(usually posteriorly) or a Salter-Harris Type I fracture 
between the capitellum and the distal humerus.
     4.  Examine the radial head.  The shape of the radial 
head should show a smooth metaphysis.  Any angles in 
the metaphysis may indicate a radial head fracture.
     5.  Examine the radiocapitellar line.  The radius 
should point directly at the capitellum in all views.  If the 
radius does not point directly at the capitellum, this 
indicates a dislocation of the radial head.
     6.  In conjunction with the AP view, count the 
number of ossification centers seen in the radiographs 
and determine their location to see if any of them are 
appearing out of the CRITOE sequence.
     7.  Examine the olecranon and the remainder of the 
ulna for irregularities in the cortex.  An ossification 
center over the olecranon may resemble a fracture.  
The presence or absence of tenderness over the 
olecranon may help to establish a diagnosis.
     8.  Check for the Hourglass sign.  Look for an 
hourglass or Figure-of-8 shape at the distal humerus.  
The absence of this indicates that the radiograph is 
not a true lateral view of the elbow.  An oblique view of 
the elbow may obscure some of the radiographic 
findings described above.

B.  Examine the AP view.
     1.  Look carefully at the distal humerus for any 
lucencies indicating a supracondylar fracture.  This 
region is highly fracture prone in children.  Fractures in 
this area may be subtle.  Examine the metaphysis for 
any interruption or angles.  Lateral condyle fractures are 
usually small, but result in significant swelling clinically.
     2.  Examine the shape of the radial head as noted 
in item 4 above.
     3.  Examine the radiocapitellar line as noted in item 
5 above.

Clinical Correlation.
     Since radial head fractures are often difficult to 
appreciate radiographically, clinical findings can often 
be helpful in suspecting an occult fracture that is not 
radiographically obvious.  Tenderness over the radial 
head or pain with supination and pronation should raise 
the suspicion of a radial head fracture in children 
without a history indicating a nursemaid's elbow.  A 
swollen elbow is almost always indicative of a fracture.  
If a nursemaids's elbow has been ruled out and the 
child is still not using the arm, this is highly suspicious 
for an occult fracture, though not necessarily in the 
elbow.

Summary Outline:
1.  Anterior fat pad.
2.  Posterior fat pad.
3.  Anterior humeral line.
4.  Radial head contour.
5.  Radiocapitellar line.
6.  Ossification centers.  CRITOE
7.  Hourglass sign.
8.  Distal humerus.
9.  Ulna/Olecranon.
10.  Clinical correlation.

Now try your skill on the case examples.  Use the 
summary outline above to develop a methodical means 
to examine the radiographs.

View Case A.


Interpretation of Case A
     1.  Anterior fat pad:  Very faint, if visible at all.  
     2.  Posterior fat pad:  Present.  Diagnostic of a joint 
effusion.
     3.  Anterior humeral line:  Slightly abnormal.
     4.  Radial head contour:  Probably normal. 
     5.  Radiocapitellar line:  Normal.
     6.  Ossification centers:  Only the capitellum is 
visible.  This is normal.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  Abnormal.  There is a lucency 
through the distal lateral humerus indicative of a lateral 
condyle fracture.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  Lateral Condyle 
fracture.  Potential Salter-Harris Type II.
 

View Case B.


Interpretation of Case B
     1.  Anterior fat pad:  Abnormally large and displaced 
upward and anteriorly.  Diagnostic of a joint effusion.
     2.  Posterior fat pad:  Present.  Diagnostic of a joint 
effusion.
     3.  Anterior humeral line:  Abnormal.  The capitellum 
is clearly posterior to the anterior humeral line.  This 
indicates that there is a supracondylar fracture 
displacing the distal segment posteriorly or a 
Salter-Harris type I fracture between the capitellum and 
humerus displacing the capitellum posteriorly.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Almost normal.  The radial 
head points at the general direction of the capitellum.  
However, a line drawn down the long axis of the radius 
does not precisely intersect the center of the capitellum.  
This is probably due to the displacement of the 
capitellum as noted in item 3 above, rather than a radial 
head dislocation.
     6.  Ossification centers:  Only the capitellum is 
visible.  This is normal.
     7.  Hourglass sign:  Present.  However, note that the 
hourglass is crinkled because of the supracondylar 
fracture.
     8.  Distal humerus:  Abnormal.  The metaphysis of 
the distal humerus on the AP view shows two 
irregularities.  On the right, the smooth contour of the 
distal metaphysis is interrupted by an angle in the 
cortex.  On the left, the smooth contour of the distal 
metaphysis is interrupted by a bulge in the cortex.  Both 
irregularities indicate a supracondylar fracture.  Within 
the body of the distal humerus, it is difficult to 
appreciate any fracture lines.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  Supracondylar fracture.


View Case C.


Interpretation of Case C
     1.  Anterior fat pad:  Not abnormally enlarged.  It is 
fairly small and it lies flat against the anterior humerus.
     2.  Posterior fat pad:  Present.  Diagnostic of a joint 
effusion.
     3.  Anterior humeral line:  Abnormal.  The capitellum 
is clearly posterior to the anterior humeral line.  This 
indicates that there is a supracondylar fracture 
displacing the distal segment posteriorly or a 
Salter-Harris type I fracture between the capitellum and 
humerus displacing the capitellum posteriorly.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  Only the capitellum is 
visible.  This is normal.
     7.  Hourglass sign:  Present.  However, again note 
that the hourglass is crinkled.
     8.  Distal humerus:  Abnormal.  The metaphysis of 
the distal lateral (on the right) humerus on the AP view 
shows a large buckling irregularity of the cortex.  On the 
medial side (left), the smooth contour of the distal 
metaphysis is interrupted by a slight bulge in the cortex.  
Both irregularities indicate a supracondylar fracture.  
The lateral view also shows a fracture of the distal 
humerus with the distal segment angulated 
posteriorly.     
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  Supracondylar fracture.


View Case D.



Interpretation of Case D
     1.  Anterior fat pad:  Difficult to see any fat pad at all.
     2.  Posterior fat pad:  Possibly very faint.  Not 
definite.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Probably normal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The capitellum, radial head, 
and internal epicondyle centers are ossified.  This is 
normal.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  Normal.
     9.  Olecranon/Ulna:  Proximal ulna shows a fracture 
inferiorly on the lateral view.
     Impression:  Olecranon fracture.


View Case E.



Interpretation of Case E
     1.  Anterior fat pad:  Abnormal.  Its shape is 
triangular.  Indicates the presence of a joint effusion.  
     2.  Posterior fat pad:  Present, indicating a joint 
effusion.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The capitellum and radial 
head centers are ossified.  This sequence is normal.
     7.  Hourglass sign:  Absent.  This indicates that the 
lateral view is oblique.  Such a view is not ideal.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  No visible fracture.


View Case F.



Interpretation of Case F
     This case consists of a lateral view only.  An AP 
view was taken of the forearm, but the top was cut off 
through the elbow.
     1.  Anterior fat pad:  Not able to see it.
     2.  Posterior fat pad:  Not able to see one.
     3.  Anterior humeral line:  Not quite perfect.  The 
anterior humeral line intersects the anterior third of the 
capitellum.  This suggests that the capitellum is 
displaced posteriorly.  However, since the capitellum is 
nearly fully ossified, no visible fracture is evident.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Out of alignment.  The 
radius is not pointing at the capitellum, indicating a 
dislocated radial head. 
     6.  Ossification centers:  Not applicable since the 
elbow is nearly fully ossified.
     7.  Hourglass sign:  Present, but not easy to see.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Obvious fracture of the ulna 
shaft and possible fracture of the olecranon.  Such an 
obvious fracture will often dominate the radiograph.  
This overshadows other findings.  This pitfall of missing 
the radial head dislocation is one that should be 
avoided by always examining the radiocapitellar line 
whenever an ulna fracture is noted.
     Impression:  Monteggia Injury (ulna fracture and 
radial head dislocation).


View Case G.



Interpretation of Case G
     1.  Anterior fat pad:  Abnormal.  It is prominent and 
triangular.  Indicates the presence of a joint effusion.  
     2.  Posterior fat pad:  No definite posterior fat pad 
visible.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The capitellum, radial head, 
internal epicondyle, and trochlea centers are ossified.  
This sequence is normal.  Take a good look at the 
trochlea since this ossification center is small and not 
easy to see on most films.  In the AP view, it is located 
between the capitellum and the internal epicondyle.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  No visible fracture.


View Case H.



Interpretation of Case H
     1.  Anterior fat pad:  Not visible.  
     2.  Posterior fat pad:  Present, indicating a joint 
effusion.
     3.  Anterior humeral line:  Not quite normal.  The line 
passess slightly anterior to the center of the capitellum.
     4.  Radial head contour:  Normal on the lateral.  
However, the AP view shows a knob-like radial head.  
The proximal radius also appears to be bent at the 
biceps tuberosity.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The capitellum, radial head, 
and internal epicondyle (barely) centers are ossified.  
This sequence is normal.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  Small, subtle lucency through 
the distal humerus most evident on the left (medial 
side).  No angulation is noted on the lateral view since 
the anterior humeral line bisects the capitellum.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  Supracondylar fracture 
and possible proximal radius fracture


View Case I.


Interpretation of Case I
     1.  Anterior fat pad:  Abnormal.  It resembles a sail 
(the sail sign).  Hemorrhaging into the joint is pushing 
the periarticular fat out of the joint.  
     2.  Posterior fat pad:  Present, indicating a joint 
effusion.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Abnormal, indicating a 
dislocated radial head.  In both views, the radius is not 
pointing directly at the capitellum.
     6.  Ossification centers:  The capitellum is ossified.  
There are tiny ossification sites at the radial head and 
the internal epicondyle.  This sequence is normal.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Distorted.  Olecranon fracture.
     Impression:  Joint effusion.  Monteggia injury.  
Olecranon fracture and radial head dislocation.


View Case J.



Interpretation of Case J
     1.  Anterior fat pad:  Abnormal.  Prominent and 
triangular.  Indicates the presence of a joint effusion.  
     2.  Posterior fat pad:  Present, indicating a joint 
effusion.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  Only the capitellum is 
ossified.  
     7.  Hourglass sign:  Although the lateral view 
appears to be somewhat oblique, an hourglass sign is 
present.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Linear lucency down the center 
of the long axis of the ulna best seen on the  AP view.  
You may need to enlarge to image to see this.
     Impression:  Joint effusion.  Ulna fracture.


View Case K.



Interpretation of Case K
     1.  Anterior fat pad:  Abnormal.  Sail sign 
configuration indicating the presence of a joint effusion.  
     2.  Posterior fat pad:  Present, indicating a joint 
effusion.
     3.  Anterior humeral line:  Not quite normal.  The line 
intersects the posterior portion of the capitellum.
     4.  Radial head contour:  Possibly abnormal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The capitellum and radial 
head centers are ossified.  This sequence is normal.
     7.  Hourglass sign:  Present but somewhat warped.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  No visible fracture 
except for a possible radial head fracture.


View Case L.



Interpretation of Case L
     1.  Anterior fat pad:  Normal.  Flat and adherent to 
the anterior humerus.  
     2.  Posterior fat pad:  Absent.
     3.  Anterior humeral line:  Abnormal.  The anterior 
humeral line does not bisect the capitellum.  This is 
probably not due to displacement of the capitellum.  
This is probably due to poor positioning of the lateral 
view.  This is an oblique view, not a true lateral.
     4.  Radial head contour:  Abnormal.  Note the 
sharp angle to the radial head metaphysis seen on the
AP view, indicating a radial head fracture.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  Only the capitellum is 
     visible.
     7.  Hourglass sign:  Absent.  This indicates that the 
lateral view is oblique.  This accounts for the abnormal 
anterior humeral line.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Radial head fracture.


View Case M.



Interpretation of Case M
     1.  Anterior fat pad:  Prominent, indicating a 
probable joint effusion.  
     2.  Posterior fat pad:  Faint, indicating a joint 
effusion.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Normal.  There is a small 
fragment above the radial head seen on the lateral 
view.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The elbow is nearly fully 
ossified.  The capitellum, radial head, internal 
epicondyle, and trochlea centers are nearly fully 
developed.  The olecranon center is ossified.  Of the 
two fragments on the lateral aspect (left side) of the 
distal humerus, one might be the external epicondyle 
ossification center.  The other is a fracture fragment.  
Both may be fracture fragments.  In this case, the 
CRITOE sequence does not help distinguish a normal 
external epicondyle from a fracture fragment since the 
external epicondyle is the last to appear.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  There are two or three 
fragments that do not represent ossification centers.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  Multiple fracture 
fragments.


View Case N.



Interpretation of Case N
     1.  Anterior fat pad:  Prominent and triangular, 
indicating the presence of a joint effusion.  
     2.  Posterior fat pad:  Present, indicating a joint 
effusion.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Normal.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  Not applicable since this 
elbow is fully ossified.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  No visible fracture.


View Case O.



Interpretation of Case O
     1.  Anterior fat pad:  Abnormal.  Prominent and 
triangular indicating the presence of a joint effusion.  
     2.  Posterior fat pad:  Not visible.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  Abnormal.  On the AP 
view, there is a slight angle in the lateral (left side) 
metaphysis of the radial head.  This slight angle is an 
interruption in the cortex of the radial head metaphysis.
This is only visible on the enlarged view.  It is best seen 
on the oblique view which is not shown here.  The 
oblique view of this patient is presented in Case 17 of 
Volume 1.
     5.  Radiocapitellar line:  Normal. 
     6.  Ossification centers:  The capitellum, radial head, 
internal epicondyle, and olecranon centers are ossified.  
The trochlea is not seen.  This can be considered 
abnormal, but because the trochlea is tiny, it may 
already be fused to the distal humerus.  This sequence 
is probably within normal limits.  The absence of 
tenderness over the olecranon would indicate that this 
ossification center is not a fracture.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Normal.
     Impression:  Joint effusion.  Radial head  fracture.


View Case P.



Interpretation of Case P
     1.  Anterior fat pad:  Very large, indicating the 
presence of a joint effusion.  
     2.  Posterior fat pad:  Probably present.  A soft 
tissue lucency is noted more inferiorly than the usual 
position.
     3.  Anterior humeral line:  Normal.
     4.  Radial head contour:  The AP view of the radial 
head shows a sharp angle interrupting the smooth 
contour of the radial head metaphysis on the lateral 
(left) side.  The radial head contour on the lateral view 
looks normal.
     5.  Radiocapitellar line:  Normal in the AP view, but 
slightly out of alignment in the lateral view, indicating 
a slight radial head dislocation. 
     6.  Ossification centers:  Only the capitellum is 
ossified.
     7.  Hourglass sign:  Present.
     8.  Distal humerus:  No irregularities seen.
     9.  Ulna/Olecranon:  Distorted olecranon on the AP 
view indicating a fracture.  The lateral view looks 
normal.
     Impression:  Joint effusion.  Monteggia injury.  
Radial head fracture and dislocation.  Ulna (olecranon) 
fracture.

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Web Page Author:
Loren Yamamoto, MD, MPH
Associate Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine
loreny@hawaii.edu