Paediatric elbow

Published on 01/04/2015 by admin

Filed under Radiology

Last modified 01/04/2015

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Paediatric elbow

The standard radiographs

AP in full extension.

Lateral with 90 degrees of flexion.

Abbreviations

CRITOL: Capitellum, Radial head, Internal epicondyle, Trochlea, Olecranon, Lateral epicondyle.

Anatomy

AP view—child age 9 or 10 years

image

AP and lateral: the CRITOL sequence

CRITOL: the sequence in which the ossified centres appear

At birth the ends of the radius, ulna and humerus are lumps of cartilage, and not visible on a radiograph. The large, seemingly empty, cartilage filled gap between the distal humerus and the radius and the ulna is normal.

From 6 months to 12 years the cartilaginous secondary centres begin to ossify. There are six ossification centres. Four belong to the humerus, one to the radius, and one to the ulna. Gradually the humeral centres ossify, enlarge, and coalesce. Eventually each of the fully ossified epiphyses fuses to the shaft of its particular bone.

Medial epicondyle—normal anatomy

Is the medial epicondyle slightly displaced/avulsed? A common dilemma.

Clinical impact guidelines: the I in CRITOL

The ossification centre for the internal (ie medial) epicondyle is the point of attachment of the forearm flexor muscles. Vigorous muscle contraction may avulse this centre (see p. 105). The most common injury mechanism is a fall on an outstretched hand. Avulsions also occur in children who are involved in throwing sports, hence the term “little leaguer’s elbow”.

When a major displacement of the internal epicondyle occurs the bone can become trapped within the elbow joint. This is a well recognised complication of a dislocated elbow, occurring in 50% of cases following an elbow subluxation or dislocation. A major avulsion is easy to overlook when an elbow has been transiently dislocated and then reduces spontaneously5,6 because the detached epicondyle may, on the AP radiograph, be mistaken for the normally positioned trochlear ossification centre (p. 105).

I before T. Though the CRITOL sequence may vary slightly there is a constant: the trochlear (T) centre always ossifies after the internal epicondyle. Therefore apply this rule: if the trochlear centre (T) is visible then there must be an ossified internal epicondyle (I) visible somewhere on the radiograph. If the internal epicondyle is not seen in its normal position then suspect that it is trapped within the joint.