This is a 4 year old female who presents to the 
emergency department with a forearm injury after falling 
off the jungle gym (playground bars) at the park.  Her 
mother noted that her forearm was deformed and she 
was complaining of persistent pain.  She denies trauma 
or pain elsewhere.
     Her past medical history is unremarkable.
     Exam:  VS are normal.  She is alert and comfortable 
in no distress.  HEENT unremarkable.  Chest and 
abdomen unremarkable.  There is a modest deformity 
of her left mid-forearm.  Tenderness is noted in the area 
of the deformity.  Her wrist and hand are non-tender.  
No bruising is noted.  Her pulses are good and 
sensation is intact.  She moves her fingers well.  Her 
elbow and humerus are non-tender.
     Radiographs of her left forearm are obtained.

View forearm radiographs.


     Although there is an obvious deformity of her 
forearm on exam, no fracture is evident here.  Her 
elbow does not demonstrate a joint effusion and her 
radial head is of normal contour and is well aligned with 
the capitellum (refer to Case 18 of Volume 2, Test Your 
Skill In Reading Pediatric Elbows).
     Note the curvature of the ulna which is excessive.  
This represents a "bowing fracture" of the ulna.  Bowing 
fractures usually occur in the forearm.  This is a 
bending deformity without a grossly visible fracture in 
the tubular structure of the bone.  Microfractures are 
present on microscopy, but only the bowing is 
appreciable on plain radiographs.  Reduction of a 
bowing fracture requires a lot of force, thus it should be 
done under general anesthesia. 
     Failure to recognize a bowing fracture of the 
forearm results in limited supination and pronation.  
Periosteal reaction on later radiographs may not occur 
with bowing fractures so this cannot be used as a 
criterion to rule out an earlier fracture.
     A comparison view of the other extremity may be 
useful in identifying the bowing fracture.


View comparison of the other forearm.


     This comparison view shows the normal 
configuration of the unaffected right radius and ulna on 
the right image.  Comparing this with her affected left 
forearm (left image), it is easier to appreciate the 
bowing deformity of the ulna.  However, note that the 
two are not very different since the bowing of the left 
ulna is not severe.

Arrows point to the bowing deformity of the ulna.




Examine the left forearm in isolation.
See if you can appreciate the bowing deformity of the ulna.


In this case, the clinical appearance of a
deformed forearm is highly indicative of a
fracture.  If radiographs fail to confirm the presence 
of an obvious fracture, consider the possibility of a 
bowing fracture.


References
     Diaphysis (Chapter 16).  In:  Harris JH, Harris WH, 
Novelline RA.  The Radiology of Emergency Medicine, 
third edition.  1993, Baltimore, MD, Williams & Wilkins, 
pp. 1059-1061.