Elbow ossification

Elbow ossification occurs at the six elbow ossification centerscentres in a reproducible order. Being familiar with the order of ossification of the elbow is important in not mistaking an epicondylar fracture for a normal ossification centercentre. 

Appearance

Order

The order of appearances of the elbow ossification centres is highly reliable and in most individuals, is consistent: capitellum, radial head, internal (medial) epicondyle, trochlea, olecranon and external (lateral) epicondyle.

The order of "I" and "T" are most important to remember; the trochlea ossification centercentre should not appear before the internal (medial) epicondyle ossification centre. If you can see a trochlea but no internal epicondyle, then you need to look very hard for the avulsed ossification centre. 

Age

Two counting methods are taught to help remember the ages at which the ossification centres appear: 1-3-5-7-9-11 (simple) and 1-5-7-10-10-11 (more accurate).

• capitellum: 1 year

• radial head: 3 years

• internal epicondyle: 5 years

• trochlea: 7 years

• olecranon: 9 years

• external epicondyle: 11 years

Therefore, if the trochlear centre is present, but there is no medial epicondyle then you are most likely looking at a medial epicondylar fracture where the ossification centre has been avulsed and displaced. This is extremely important since these injuries should be seen by an orthopaedic surgeon and internally fixed.

Variation

Exceptions have been described in the literature to the usual sequence of appearance of elbow ossification centerscentres and recognizedrecognised as normal variants ². This can occur in up to a quarter of children with incidence much more common in girls.

Video tutorial

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