Medial epicondyle avulsion

Q: What is the diagnosis? show answer

A: Medial epicondylar avulsion with the apophysis displaced into the joint.

Q: How does knowledge of the order in which the centers of ossification of the elbow appear help in this case? show answer

A: In this case, the trochlea and external (lateral) epicondyle ossification centres are clearly seen (appear at ~10-11 years). As such the internal (medial) epicondyle ossification centre should be present (appears at ~7 years). As it is not visible, it must be sought, and not mistaken for another centre.

Q: What mnemonic is frequently used to help in this endeavour? And at what ages do each center appear at? show answer

A: CRITOE (C = capitellum (1 year); R = radial head (5 years); I = internal (medial) epicondyle (7 years); T = trochlea (10 years); O = olecranon (10 years); E = external (lateral) epicondyle (11 years).

Q: What other elbow injury is associated with medial epicondylar avulsion? show answer

A: Posterolateral elbow dislocation, which may spontaneously reduce prior to clinical assessment or imaging.

Q: In addition to elbow dislocation (in which the ulnar collateral ligament is responsible for avulsing the apophysis) what other mechanisms is frequently responsible? show answer

A: Fall on an outstretched arm, with the elbow and wrist extended. The sudden traction / contraction of the flexor pronator muscle group which attaches to the apophysis, rips it off. A direct blow is a rare cause.