Elbow Ossification Centers in a Child
Radiology Cases in Pediatric Emergency Medicine
Volume 1, Case 11
Alson S. Inaba, MD
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
     A 7 year old male presents to the ED with isolated 
right elbow pain three hours after falling on his 
out-stretched right arm while roller blading.  The patient 
did not sustain any other trauma to his head, neck or 
trunk.  He has not complained of any numbness or 
tingling in his right hand post-injury.
     Exam:  The right upper extremity from the clavicle to 
the tip of the fingers is atraumatic in appearance 
without any obvious angulation or swelling.  The patient 
exhibits full range of motion about the shoulder and 
wrist.  There is no tenderness over the anatomic 
"snuffbox" region.  The elbow has no obvious swelling, 
and the elbow circumference (of the affected arm) is 
equal to the elbow circumference of the non-affected 
arm.  There is very mild, diffuse tenderness about the 
right elbow (without any specific point tenderness).  He 
has no pain with active elbow flexion, extension, 
supination, or pronation.  Although you clinically do not 
suspect any fracture of the right elbow region, the 
patient's mother is very anxious and demands an x-ray 
of her son's elbow.  Radiographs of the right elbow are 

View elbow radiographs.

     1)  How many ossification centers are present in this 
radiograph and what are the names of these 
ossification centers?
     2)  Are the ossification centers in their correct 
(expected) anatomic positions?
     3)  Are there any fractures present in this 
radiograph, and if so where?

Discussion & Teaching Points:
     1)  There are 6 ossification centers around the elbow 
joint.  These ossification centers all appear at different 
ages and they all fuse to the adjacent bones at various 
ages.  It is not clinically important to memorize the 
specific ages of when these ossification centers appear 
or fuse.  However, it is clinically important to realize that 
the ossification centers always appear in a specific 
sequence.  The mnemonic of the order of appearance 
of the individual ossification centers is C-R-I-T-O-E:   
Capitellum, Radial head, Internal (medial) epicondyle, 
Trochlea, Olecranon, External (lateral) epicondyle.  
Remember that the anatomic position of the body 
places the upper extremities in external rotation 
(supination at the elbows) such that the antecubital 
fossa faces anteriorly.  Thus, the external epicondyle is 
on the radial side of the elbow, while the internal 
epicondyle is on the ulnar side of the elbow.
     The ages at which these ossification centers appear 
are highly variable, but as a general guide, remember 
1-3-5-7-9-11 years.  Note that our patient in this case is 
7 years old but all six ossification centers are present.  
This illustrates that this age sequence is just a guide 
since the age ranges are highly variable.

Review elbow diagram.

     2)  Knowing the C-R-I-T-O-E mnemonic is helpful in 
determining whether a small piece of bone about the 
elbow joint represents an avulsion fragment or an 
ossification center.  The ossification centers always 
appear in the order specified in the mnemonic 
     3)  Example:  If you see only three accessory bony 
fragments about an elbow joint, these bony pieces 
should be in the areas of the capitellum, radial head 
and the internal (medial) epicondyle.  If one of the three 
bony fragments is in the area where you would expect 
to see the external epicondyle, then that piece actually 
represents an avulsion fracture of the distal, lateral 
humerus, rather than a normal external epicondyle.
     4)  Whenever evaluating an injured extremity, the 
most important aspect of the examination is to assess 
the neurovascular integrity of the affected extremity.
     5)  Always remember to palpate the entire extremity 
(including the clavicles) in all children who present after 
falling on the out-stretched arm.
     6)  Always remember to document whether or not 
the patient who has fallen on the out-stretched hand 
has any tenderness over the anatomic "snuffbox" 
(scaphoid bone).  Any patient with tenderness over the 
scaphoid (navicular) bone must be treated (splinted with 
orthopedic referral) as an occult scaphoid fracture 
until proven otherwise (even if the initial scaphoid 
views do not reveal any evidence of a fracture).  Refer
to Case 14 (A Hand Contusion) for more details.

     Radiographic Findings:   No evidence of
elbow effusion.  Normal anterior humeral line
and a normal radiocapitellar line.  (Refer to Case 
12, Radiographic Examination of the Elbow, to learn 
how to assess elbow effusions and how to measure the 
anterior humeral and radiocapitellar lines).  All six 
ossification centers are present in their expected 
anatomic positions.
     Overall radiographic interpretation:  Normal right 
elbow with normal ossification centers. 

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Web Page Author:
Loren Yamamoto, MD, MPH
Associate Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine