Case

32 year old right handed man presents with right thumb pain after a mechanical fall from standing onto steps.  While falling, his outstretched thumb caught on a step.  He denies other injury.  On exam, he has pain and swelling at the thumb MCP joint.  There is a palpable lump on the ulnar side of the base of his thumb.  He has full ROM and intact strength in the affected digit.

What are the next steps in this patient’s management?

Epidemiology

• Most commonly occur in athletes when a force causes thumb abduction
• Skiing accidents in which the thumb is abutted against a fixed pole are the prototypical injury
• More common in males with a ratio of 3:2
• Complete ulnar collateral ligament tears can occur by non-sport related falls, motor vehicle crashes in which the hands are on the steering wheel, or bicycle injuries from handlebars

UCL anatomy

• Runs from middle of metacarpal head to the volar aspect of the proximal phalanx
• Provides structural strength to the thumb
• Resists valgus load to thumb

Mechanism of Injury

• Hyper-extension or abduction of the thumb causes the UCL to avulse from the proximal    phalanx
• Acute injuries result in a complete or partial tear of the ligament
• Avulsion fractures of proximal phalanx may or may not be present

Clinical Presentation

• Acute injuries present with pain and swelling of the base of the thumb
• Chronic injuries, also known as Gamekeeper’s thumb, present with loss of strength of the   thumb and deformity

Traditionally, this injury was originally described in people who manually and repetitively sacrificed small game by breaking the animal’s neck.

Exam

• Cornerstone of diagnosis
• Goal of exam is to evaluate joint stability
• Valgus stress of the MCP joint reveals increased laxity
• Test in both neutral position and with MCP joint fully flexed.  Fully flexing the joint isolates the UCL from the volar plate, which can provide additional stability
• Angulation of >35 degrees, or a difference of >15 degrees between hands signifies a        positive test.
• In partial tears, the loss of a distinct endpoint while stressing may be noted

Stener lesion

Occurs when the proximal end of the completely torn ligament is pulled from its normal location deep to the abductor aponeurosis and then fails to reduce itself properly, remaining superficial to the aponeurosis   

• Present in up to 50% of complete UCL tears.
• Exam may note a palpable lump
• Surgical intervention is required
• Stressing the MCP has NOT been shown to cause a Stener lesion where one did not already exist.
• Pinch grip may be reduced in both acute and chronic injuries

ED Evaluation

• Plain films to evaluate for avulsion fracture of proximal phalanx
• Stener lesion will not be evident of plain films
• Ultrasound has not been fully validated in diagnosis UCL tears
• MRI is not cost effective in the ED, but may be obtained in follow-up in consultation with a hand surgeon

ED Management

• Thumb spica is hallmark of ED management, allowing for immobilization of thumb MCP joint
• If joint deemed unstable, follow-up within 1 week to a hand surgeon is advised to allow for surgical planning.  A delay in surgery can cause contracture of the UCL and increases  likelihood of chronic instability
• For stable injuries, non-urgent follow-up within 4 weeks is recommended.

Faculty Reviewer: Dr. Kristina McAteer

References

• Germano, T.  Falls on the Out-Stretched Hand and Other Traumatic Injuries of the Hand and Wrist: Part II.  Emergency Medicine Reports:  The Practical Journal for Emergency Physicians.  Volume 28, Number 18.  August 20, 2007.
• Gammons, M et al.  Ulnar collateral ligament injury (gamekeeper's or skier's thumb).  Retrieved from UpToDate.com.  Accessed 4/21/2018.
• Richard, JR.  Gamekeeper’s Thumb:  Ulnar Collateral Ligament Injury.  Am Fam Physician.  19