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Complete ulnar collateral ligament rupture of the thumb MCP joint (grade III skier's thumb) — MSRA MCQ

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ModerateSoft Tissue InjuryComplete ulnar collateral ligament rupture of the thumb MCP joint (grade III skier's thumb)MSRA

A 32-year-old right-hand-dominant rugby player attends a GP-led urgent treatment centre 3 hours after his left thumb was forcibly abducted and extended when it caught in an opponent’s shirt. He has immediate swelling and focal tenderness over the ulnar aspect of the thumb metacarpophalangeal (MCP) joint. There is no wound or neurovascular deficit. True anteroposterior and lateral thumb radiographs show no fracture, avulsion fragment or dislocation. After local anaesthetic infiltration, valgus stress testing demonstrates substantially increased MCP joint opening compared with the opposite side in both flexion and extension, with no definite end point. What is the most appropriate management now?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Apply thumb-spica immobilisation and arrange urgent hand or plastic surgical assessment today

Explanation lettering: E = shown as C · C = shown as E

This is a grade III ulnar collateral ligament (UCL) injury of the thumb MCP joint: the mechanism is forced thumb abduction/extension, tenderness is maximal over the UCL, and stress testing after adequate analgesia shows instability without an end point. Normal radiographs do not exclude a complete ligament rupture. Grade III UCL injury requires thumb-spica immobilisation and urgent discussion with hand/plastic surgery, because exploration and repair may be required and imaging may be considered to assess for a Stener lesion. A is appropriate for a grade II injury, where there is some laxity but a definite end point is retained. C is plausible because ultrasound can help identify a Stener lesion, but it should not delay urgent specialist assessment in a clinically complete rupture; the hand service should determine whether imaging or operative exploration is required. D provides inadequate stabilisation for a potentially unstable thumb MCP joint. E is inappropriate initially because unprotected movement risks persistent instability, weak pinch grip and impaired hand function.

Reference: How manage Hand injuries and infections in the ED – September 2023 (September 2023) — https://rightdecisions.scot.nhs.uk/media/3bcjfknw/2023-09-sjh-ed-hand-guidance.pdf