UCL Injury

ANATOMY

Illustration by Dr. Lisa Bryski

The UCL has a proper and accessory collateral ligament. It is the primary restraint against valgus forces to the first MCP joint in flexion and extension.¹

CLASSIC PRESENTATION

Patients will have a history of trauma with pain and difficulty with movement of the thumb. They'll have ecchymosis, edema and tenderness at the ulnar aspect first MCP and may have a weak pincer grasp.

The classic mechanism is hyperabduction/acute valgus and hyperextension forces to the first MCP. Occurs with fall on outstretched hand or grasping an object during a fall.¹

The acute injury is classically noted in skiers. The term "Gamekeepers thumb" refers to chronic instability. Historically, gamekeepers sustained chronic valgus strain when breaking rabbit necks.³

Diagnosis

X-rays to rule out avulsion fractures or joint subluxation should be done. Following that, a UCL stress test should be performed.

Tip: Examine the normal side first before the injured side to assess for baseline laxity (some patients have very lax joints, especially females).

To stress the UCL:

Stabilize the metacarpal
Stress the metacarpal joint with the joint in 45 degrees of flexion to test laxity of the ulnar collateral ligament

*Stressing the MCPJ with the joint in extension tests laxity of the accessory collateral ligament

A complete UCL tear lacks a firm endpoint. Laxity may denote a accessory or primary tear.¹

Clinical Pearl: Injection of 1-2ml of lidocaine into the MCP increases clinical accuracy of the test from 28% to 98%.⁵

COMPLICATION: STener Lesion

When a complete UCL tear displaces proximally and lies superficial to the overlying adductor aponeurosis (refer to the illustration by Dr. Lisa Bryski), this is called a Stener Lesion.

This is a very rare complication of UCL injuries.

Stener lesions are an absolute indication for operation. Ligament healing is impaired due to transpositon of the adductor fascia within the UCL, resulting in ulnar laxity regardless of the period of immobilization.

Treatment

The MCP is immobilized in a thumb spica with mild flexion, slight ulnar deviation, and the interphalangeal joint free.

Patients should follow up with a hand specialist for surgical consideration or continue 4-6 week immobilisation.¹

References

1. Smerjit Singh Madan, M., Dinker R Pai, M., Avneet Kaur, M., Dixit, R., & MD. (2014). Injury to Ulnar Collteral Ligament of Thumb. Orthopaedic Surgery, 1-7.

2. Vykoukal, J. (2020). Sprained Thumb Overview. Retrieved from https://www.vivehealth.com/blogs/resources/sprained-thumb-pain

3. Campbell, C. S. (1955). Gamekeeper's thumb. The Journal of bone and joint surgery. British volume, 37(1), 148-149.

4. File:Valgus stress.gif. (2011, March 19). Physiopedia,. Retrieved 21:03, September 4, 2020 from https://www.physio-pedia.com/index.php?title=File:Valgus_stress.gif&oldid=29404.

5. Cooper, J., Johnstone, A., Hider, P., & Ardagh, M. (2005). Local anaesthetic infiltration increases the accuracy of assessment of ulnar collateral ligament injuries. Emergency Medicine Australasia, 132-136.

6. Kawanishi, Yohei & Oka, Kunihiro & Tanaka, Hiroyuki & Sugamoto, Kazuomi & Murase, Tsuyoshi. (2017). In Vivo Scaphoid Motion During Thumb and Forearm Motion in Casts for Scaphoid Fractures. The Journal of hand surgery. 42. 10.1016/j.jhsa.2017.03.008.

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