A 44M with no PMH slipped and fell on his hand while playing with his kids in the park. He has swelling and pain over thumb MCP joint that is exacerbated by movement. The xray of his thumb is above, what is your diagnosis?

This injury is known as skier’s thumb. The mechanism is a forced radial deviation of the thumb which causes injury to ulnar collateral ligament (UCL). This pattern of injury can also occur when someone falls onto their thumb, or when a thumb is stuck and forced into abduction and hyperextension. Of note, gamekeeper’s thumb is associated with repetitive injury or trauma, while skier’s is an acute trauma.

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On exam, patient’s will have tenderness over the MCP joint (worse on the ulnar side) and swelling. MCP joint may not be able to fully flex to 90degrees and pinch grip (of thumb and first finger) may be diminished.

An xray may demonstrate an avulsion fracture, but can be normal. If xray is normal, stress testing can be applied to the MCP to assess for increased laxity. The provider will stabilize the metacarpal with one hand, while the other hand will apply radial stress to the proximal phalanx. This is performed in both full extension and 30 degree flexion. More than 40 degrees of laxity indicates complete UCL tear.

In the emergency department, we should apply a thumb spica splint and refer to ortho. Generally these injuries are non-operative, but surgery should be considered if the bony fragment is more than 2mm displaced or involves more than 10-20% of articular surface or there is concern for complete UCL tear.

Sources: Davenport M, Sotereanos DG. Chapter 265. Injuries to the Hand and Digits. In: Tintinalli JE, Stapczynski J, Ma O, Cline DM, Cydulka RK, Meckler GD, T. eds.Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7e. New York, NY: McGraw-Hill; 2011