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?

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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.

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.

Reference: http://emedicine.medscape.com/article/826399

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