Imaging Case of the Week 101

The following right thumb x-ray is from a 20 year old with pain around the base of the thumb after suffering a fall on his outstretched thumb. What can you observe and what is the significance of the injury?

right thumb x-ray

click to enlarge

[peekaboo_link name=”Answer”]Answer[/peekaboo_link] [peekaboo_content name=”Answer”]

This thumb x-ray shows a fracture through the medial aspect of the base of the proximal phalanx of the thumb; this fracture extends into the MP joint.

This fracture type signifies an injury to the attachment site of the ulnar collateral ligament of the thumb.

skiers thumb

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Ulnar collateral ligament injury of the thumb MP joint:

  • Acute injury is called a Skier’s thumb and a chronic injury, the Gamekeeper’s thumb.
  • Common mechanism is a hyperextension injury to the thumb.
  • Most injuries are ligamentous injuries. Occasionally part of the bone from the base of the proximal phalanx can be avulsed.
  • Examination shows point tenderness +/- swelling on the ulnar aspect of the MP joint of the thumb.
  • Valgus stress testing will determine the integrity of the UCL but an x-ray should be obtained prior to this as a displaced avulsion fracture of the base of the proximal phalanx can be made worse by stress testing.
  • Patients can be discharged from the ED with a thumb spica but need a follow up organised with a hand/ortho specialist within the next few days.
  • Partial tears of the UCL and non-displaced avulsion fractures are treated conservatively.
  • Surgical exploration is indicated for complete UCL tears, displaced avulsion fractures, and fractures of the base of the PP involving over 25% of the articular surface.