A 2-year-old boy is lifted suddenly by his right hand while playing. He immediately refuses to use the arm, which is held slightly flexed and pronated against his body. Radiographs are normal. The injury involves which structure?

• A Rupture of the ulnar collateral ligament of the elbow
• B Avulsion of the medial epicondyle apophysis
• C Subluxation of the radial head through the annular ligament ✓
• D Dislocation of the superior radio-ulnar joint

Explanation

This is pulled elbow (nursemaid's elbow). In young children the annular ligament is lax and not yet firmly bound to the radial neck, so traction with the forearm pronated allows the radial head to slip partly out beneath it. Reduction by supination and flexion gives immediate relief. Medial epicondylar avulsion follows valgus stress in older children, and true dislocation of the proximal radio-ulnar joint is rare and traumatic.

Reference: Snell's Clinical Anatomy by Regions, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.