Volume 6, Case 16
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
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.