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What is your diagnosis?

The patient is diagnosed with an ulnar collateral ligament (UCL) rupture of the thumb with an associated avulsion fracture. This injury occurs most frequently due to hyperabduction and valgus stressing of the 1st digit [1]. 

• Pearl: This acute injury is often referred to as “Skier’s Thumb”. A chronic injury to the UCL is often referred to as “Gamekeeper’s Thumb”. 

How is it diagnosed?

This diagnosis is largely based on clinical history and exam. An XR should be obtained to evaluate for an associated avulsion fracture (Image 1). On exam, valgus stressing of the 1st MCP joint will reveal instability and tenderness on the ulnar aspect of the thumb. Laxity that is greater than 15º difference when compared to the contralateral side suggests UCL injury [2].

• Pearl: An ultrasound can be used to aid in diagnosis by identifying laxity and tears with dynamic testing as well as associated fractures (Image 2).

Image 2. Case courtesy of Dr Maulik S Patel, Radiopaedia.org, rID: 50840

What is your management in the ED? What is your disposition?

In the ED, patients should be placed in a thumb spica splint and referred to a hand surgeon for outpatient followup. For complete tears, surgery is usually required to maintain stability and pinch strength [3].

• Pearl: The UCL plays a large role in pinch strength [4]. Test this by having the patient hold onto a piece of paper. If they are unable to hold onto the paper when you try to tear it away, it usually means that they will require surgery. 

When do you consult Orthopedics?

As long as other emergent conditions have been ruled out, patients can safely follow up outpatient with their thumb immobilized in the thumb spica splint.