A 39-year-old female presents to the emergency department with right thumb pain after falling in a skiing accident. On exam, there is mild swelling and tenderness on the ulnar aspect of the 1st MCP joint. Additionally, there is laxity with valgus stressing of the 1st MCP joint. An x-ray is obtained and shown above (Image 1. Provided by Alex Tomesch, MD).
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 .
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”.
This diagnosis is largely based on clinical history and exam. An X-ray 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 .
Pearl: An ultrasound can be used to aid in diagnosis by identifying laxity and tears with dynamic testing as well as an associated fracture (Image 2).
Image 2. Case courtesy of Dr. Maulik S Patel, Radiopaedia.org, rID: 50840
In the ED, patients should be placed in a thumb spica splint and referred to a hand surgeon for outpatient follow-up. For complete tears, surgery is usually required to maintain stability and pinch strength .
Pearl: The UCL plays a large role in pinch strength . 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.
Resources & References:
Need a refresher on the anatomy of UCL ligaments and examination techniques? Be sure to check out Dr. Lin’s excellent clinical tip post!
Ritting AW, Baldwin PC, Rodner CM. Ulnar Collateral Ligament Injury of the Thumb Metacarpophalangeal Joint. Clinical Journal of Sport Medicine. 2010;20(2):106-112. PMID: 20215892
Mahajan M, Rhemrev SJ. Rupture of the ulnar collateral ligament of the thumb – a review. Int J Emerg Med. 2013;6:31. PMID: 23938194
Selsky A, Ilyas A. Thumb Ulnar Collateral Ligament Tear Repair. JOMI. Published online 2020.