A 9-year-old boy with forearm trauma has an anteroposterior radiograph on which a line drawn along the shaft of the radius fails to pass through the centre of the capitulum. This finding is most suggestive of:

• A Supracondylar fracture of the humerus
• B Normal variant of elbow ossification
• C Fracture of the olecranon
• D Dislocation of the radial head accompanying an ulnar shaft fracture ✓

Explanation

The radio-capitellar line, drawn along the longitudinal axis of the proximal radius, must pass through the centre of the capitulum on any view at any age. Failure to do so indicates dislocation of the radial head, classically seen in Monteggia fracture-dislocation where an ulnar shaft fracture accompanies the dislocation. Supracondylar fractures displace the capitulum relative to the anterior humeral line but do not disrupt this relationship.

Reference: Moore's Clinically Oriented Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.