The elbow x-rays show a displaced fracture of the medial epicondyle and an elbow effusion in this skeletally immature patient.

The medial epicondyle avulsion fracture –

• Occurs between ages 9-14 years.
• The apophysis serves as origin of the ulnar collateral ligament & common flexor tendons of the forearm.
• Common in the setting of elbow dislocations. However, can manifest in adolescent throwers from extreme valgus force used.
• The avulsed fragment usually displaces anteriorly and inferiorly. Some avulsions may be only displaced minimally and hence may radiologically remain occult. Significant soft tissue swelling may be the only prominent sign.
• Always scrutinize missing ossification centers on elbow x-rays (CRITOE). If the trochlea, olecranon and external epicondyle ossification centers are present, one should be able to visualize the medial epicondyle ossification center.
• All cases should be referred to the specialist for further management. Clinically, carefully examine the patient for ulnar nerve entrapment features.

The above patient underwent surgical fixation of the avulsed apophysis.

Reference: https://pubs.rsna.org/doi/pdf/10.1148/radiol.2017161175