A 9 year old male fell off a slide and landed on his 
outstretched left arm.  He now presents to the ED with 
pain in his left forearm and elbow.  There is no history 
of head trauma.  He denies having a headache, and 
there is no nausea or vomiting.  His past medical 
history is unremarkable.
     Exam:  Vital signs T37, P76, R20, BP110/73.  He  
is alert and oriented but in obvious discomfort 
secondary to left arm pain.  Pupils are equal and 
reactive.  His left clavicle, shoulder and humerus are 
nontender.  His left hand and wrist (including the 
anatomic snuffbox) are also nontender.  He is tender 
over the proximal aspect of his left forearm.  He is 
unable to flex, extend, supinate, or pronate at his left 
elbow.  He is able to move all his fingers well.  Distally, 
he is neurovascularly intact.  Capillary refill time is 2 
seconds.  Radiographs of his left forearm and elbow 
were obtained.

View forearm radiographs.


View elbow radiographs.

     There is an obvious mid-shaft ulnar fracture.  Do you 
see anything else wrong with the radiographs?  Look at 
the radiographs again.
     The radial head should point at the capitellum in all 
views.  A line drawn down the long axis of the radius 
(radial head) should intersect the capitellum in all views.  
Review Case 12 (Radiographic Examination of the 
Elbow) for further discussion on the radiocapitellar line.
     In this case, the line drawn down the long axis of the 
radius does not intersect the capitellum.  This indicates 
that the radial head is dislocated.  In this case, there is 
an anterior dislocation of the radius.  There is a 
prominent anterior fat pad visible, which is probably 
within normal limits.  No posterior fat pad sign is seen.
     The patient was taken to the OR for closed 
reduction under general anesthesia.

Teaching points and Discussion.
     1.  In 1814, Monteggia first described the 
combination of proximal ulnar fracture with anterior 
dislocation of the radial head.  The Monteggia 
fracture-dislocation now includes several different types 
of ulnar fractures with radial head dislocation.  In 
children, the classic form of Monteggia's injury is 
uncommon.  Monteggia fracture-dislocation comprises 
2% of all elbow fractures in children.
     2.  Monteggia's injury can easily be overlooked.  In 
general, isolated ulnar fractures are very rare.  With any 
type of ulnar fracture, it is important to have 
radiographs of both the forearm as well as the elbow 
joint.  Recognition of a Monteggia's injury is critical 
because if the radial head is not reduced, it could lead 
to permanent disability.
     3.  The most common mechanism of injury in 
children is hyperextension at the elbow joint.  This 
results in fracture of the ulna with anterior angulation 
and an anterior dislocation of the radial head.  Another 
mechanism is hyperpronation of the forearm with a fall 
on an outstretched hand.  The annular ligament is either 
torn or is displaced over the radial head.
     4.  On examination, there may be tenderness, 
swelling, and deformity at the site of the ulnar fracture.  
This can sometimes distract the examiner from noticing 
injury at the elbow.  The dislocation of the radial head 
may often be palpated.  With any obvious forearm 
deformity, it is important to examine the elbow and wrist 
for injury also.  The presence or absence of tenderness 
on palpation of the radial head should be noted.
     5.  Radiographs of the forearm, elbow, and wrist 
should be obtained.  Always remember to include the 
joint above and below the site of injury.  It is important 
to have a true lateral of the elbow along with the 
anteroposterior view.  A line drawn through the long 
axis of the radius should pass through the center of the 
capitellum in all views.  With radial head dislocation, this 
line does not intersect the center of the capitellum.
     6.  The ulnar fracture in Monteggia's injury is most 
often at the proximal to middle third of the ulna.  
Sometimes the fractureis not complete; there may be 
a greenstick fracture or even bowing of the ulna 
associated with the radial head dislocation.  The radial 
head dislocation may be anterior, posterior, or lateral.
 
View another example:  Lateral view.


AP view.

     The lateral view shows a large anterior fat pad and a 
small posterior fat pad indicating a joint effusion.  You 
may have to adjust the contrast and brightness controls 
on your monitor to appreciate this.  There is a tiny 
cortical angle noted on the inferior margin of the radial 
head metaphysis where it crosses the ulna, indicating a 
subtle radial head fracture.  The radius is NOT pointing 
directly at the capitellum.  This indicates dislocation of 
the radial head.  The AP view is more of an oblique 
view.  It shows a fracture of the olecranon.  The radial 
head metaphysis shows a sharper cortical angle, 
making the radial head fracture more obvious.  This is a 
very subtle example of a Monteggia injury (ulna fracture 
with radial head dislocation).  Although the radial head 
fracture is not necessarily part of the Monteggia injury, 
the same forces resulting in radial head dislocation 
probably caused the radial head fracture as well.
     7.  Do not splint or cast a Monteggia's injury and 
discharge from the ED.  This requires an immediate 
orthopedic referral.  The radial head dislocation must be 
reduced by an orthopedic surgeon as soon as possible.  
In most pediatric cases, a closed reduction under 
general anesthesia can be done.  Sometimes open 
reduction of the radial head  dislocation and internal 
fixation of the ulnar fracture are required.  With early 
recognition and treatment, there is usually a good 
long-term result.
     8.  The posterior interosseous branch of the radial 
nerve is the most commonly injured nerve associated 
with Monteggia's injury.  This nerve injury is usually 
self-limited and resolves.  This nerve innervates the 
deep extensor muscles (extensor digitorum, the 
extensor digiti minimi, the extensor carpi unlaris, and 
the extensor indicis).
     9.  Complications of Monteggia's injury include 
recurrent dislocation of the radial head, persistent 
subluxation of the radial head, nerve injuries, and 
limitation of elbow range of motion.

References
     1.  Joffe M.  Monteggia's fracture and radial head 
dislocation.  In:  Barkin RM (ed).  Pediatric Emergency 
Medicine Concepts and Clinical Practice.  Chicago, 
Mosby Year Book, 1992, pp. 353-354.
     2.  Bachman D, Santora S.  Orthopedic Trauma.  In:  
Fleisher GR, Ludwig S (eds).  Textbook of Pediatric 
Emergency Medicine, third edition.  Baltimore, Williams 
and Wilkins, 1993, pp. 1260-1261.
     3.  Letts RM.  Monteggia and Galeazzi Fractures.  
In:  Letts RM (ed).  Management of Pediatric Fractures.  
New York, Churchill Livingstone, 1994,  pp. 295-313.
     4.  Lincoln TL, Mubarak SJ.  Isolated Traumatic
Radial-Head Dislocation.  Journal of Pediatric
Orthopedics 1994;14:454-457.