A 32 years old female present’s to ED, c/o sore left thumb after she slipped while mopping the floor causing her thumb to abduct against the mop handle. On examination the thumb is swollen and bruised over the MCP joint, with marked laxity on flexion and extension of the MCP joint. You give the patient analgesia then send them to X-ray to rule out a fracture.
What is the diagnosis?
Injury to ulnar collateral ligament:
- Injury to the ulnar collateral ligament can occur acutely or chronically, and is an easy to miss injury that can lead to chronic instability if not identified and treated early.
- Acute injury known as skier’s thumb occurs due to a fall on outstretched hand with thumb forced into abduction.
- Gamekeeper’s thumb is a chronic lesion which develops from repetitive strain on the UCL.
- The UCL which prevents abnormal opening of the MCPJ of the thumb on the ulnar side is over-stretched and torn, rendering the joint unstable. The ligament on radial side can occasionally suffer a similar injury.
- Injury to the ulnar collateral ligament injury is often associated with an avulsion fracture of the proximal base.
Classification of UCL injuries:
Test is performed by putting stress on the ligament.
- Grade 1 injuries occur when pain is felt on stressing the ligament
- Grade 2 pain and limited degree of laxity
- Grade 3 occurs with marked laxity with no pain on the stressed ligament indicates possible complete rupture.
Emergency Department Assessment:
Clinically can present with:
- Pain, swelling and bruising over MCP joint, acutely this is accompanied with haematoma and inflammation.
- Maximal tenderness on palpation over UCL
- Decreased range-of-movement
- Pinch grip and power are lost, thumb may deviate radially
- Test for sensation and observe for neurovascular compromise
- Local anaesthetic or ring block can assist you to fully test laxity.
- Apply valgus force with the thumb in 30° of flexion. If there is more than 30° laxity or more than 15° more laxity than on the uninjured side, rupture of the UCL is likely.
- Then examine the thumb in full extension with a valgus stress to assess the accessory collateral ligament. If less than 30° valgus laxity, or 15° or less than on the uninjured side, the accessory ligament is intact.
Stress testing of the MCP joint of the thumb in flexion.
Stress testing of the MCP joint in extension.
- Plain X-rays are the initial investigation of choice
- Standard anteroposterior and lateral X-rays of the thumb are used to rule out avulsion fractures
- Ultrasound and MRI are sometimes requested when diagnosis is in doubt, however these test are generally requested after specialist review
- Ultrasound shows a sensitivity and specificity of around 80% and MRI has around 100% for detecting UCL injury.
Emergency Department Management:
- Assess for other injuries
- Provided analgesia, ICE, splint, elevate
- Arrange X-ray to exclude fracture
- Immobilise thumb in a plaster or Paris thumb spica cast for 1 week, then patient can be changed to a thermoplastic thumb spica cast.
- Arrange for early orthopaedic/plastic surgery review for operative Vs conservative management. Currently a very contentious issue and debate continues regarding which UCL injuries require surgical repair.
- As a rule of thumb (pardon the pun) incomplete ligament tears are managed conservatively, and patients with complete tears and avulsion fractures do better managed operatively.
Anderson, D. (2010). Skier’s thumb. Australian Family Physician. 39(8), 575-577. (full text)
Brown , A. & Cadogan, M. (2006). Rupture of the Ulnar Collateral Ligament. Emergency Medicine Emergency and Acute Medicine: Diagnosis and Management. Hodder Arnold: New York.
Foye, P. et.al. (2010). Skier’s Thumb. www.emedicine.medscape.com. (full text)
Purcell, D. (2010). Minor Injuries a clinical guide. Churchill Livingstone: Elsevier.