Thumb UCL injury: MRI and schematic diagram

Skier's thumb. A 21-year-old man presented with pain and instability of the thumb after a skiing accident.

(A) Coronal T2-weighted fat saturated MR image through the first metacarpophalangeal joint shows a tear of the ulnar collateral ligament (arrow), displaced under the aponeurotic hood of the adductor pollicis (Stener lesion).

(B) Mechanism of injury: normal ulnar collateral ligament (arrow).

(C) Abduction injury: The ulnar collateral ligament is ruptured at the metacarpal insertion (arrow).

(D) Postreduction Stener lesion: The ruptured ulnar collateral ligament is displaced under the aponeurotic hood (arrow) (compare with image A—MRI study).