v2c18

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 nursemaid'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

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.

Interpretation of Case F
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

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.