Case 50

5 yo male with no significant PMH c/o right elbow pain s/p fall 4 hrs PTA.  Pt was running, slipped, and fell on outstretched hands.  He refuses to move his right arm, holding it in slight flexion and supination. He was sent in by an outside urgent care center for a possible nursemaids's elbow.

Prior to attempts at reduction or X-Ray studies, you get an ultrasound and note the following images.

L elbow - sagittal view

L elbow - sagittal view

R elbow - sagittal view

R elbow - sagittal view

The pt also gets taken for XRs.

lateral XR

lateral XR

QUESTIONS:

  1. What is the “Sail Sign” and why is it useful in assess elbow X rays?
  2. What is a posterior fat pad sign?
  3. What probe is used for evaluation of fractures in the pediatric patient?
  4. What are the ultrasound findings seen above that are abnormal and what do these findings indicate?
  5. Is ultrasound more or less sensitive than XR for elbow fractures?

ANSWERS:

  1. The anterior fat pad of the distal humerus may be normal or if large may be abnormal ("sail sign"). It indicates the presence of an elbow joint effusion, which elevates the fat pad.  Elevation of the anterior fat pad usually heralds the presence of an intra-articular fracture. In children, the most common cause of a raised elbow fat pad is a supracondylar fracture. Where a fat pad is raised and no fracture is demonstrated, an occult fracture should be suspected.

  2. The visualisation of a lucent crescent of fat located in olecranon fossa on true lateral view of elbow joint. It indicates an elbow joint effusion and is particularly helpful in occult non-displaced fractures because a posterior fat pad is always abnormal.

  3. The high frequency linear probe should be used for the evaluation of a fracture in a pediatric patient.

  4. You should ultrasound the humerus/olecranon in the following planes.

Normal ultrasound images on the left.  Abnormal ultrasound findings on the right.

Normal ultrasound images on the left.  Abnormal ultrasound findings on the right.

If an effusion is noted above the olecranon (equivalent to posterior effusion seen on x-ray), that is a strong indication that patient has a fracture.

5.  The ultrasound may be more sensitive than XR for detecting a posterior effusion. An example of posterior effusion from our above patient: