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

A 32-year-old right-hand-dominant paramedic attends a GP-led urgent treatment centre 3 hours after trying to catch a heavy equipment case as it fell. Her right thumb was forcibly abducted and extended at the metacarpophalangeal (MCP) joint. There is swelling and maximal tenderness over the ulnar aspect of the thumb MCP joint. There is no wound, deformity or neurovascular deficit. True anteroposterior and lateral thumb radiographs show no fracture, avulsion fragment or dislocation. Following adequate local anaesthesia, valgus stress testing of the MCP joint in both extension and flexion demonstrates substantially greater opening than the contralateral thumb, with no firm endpoint. What is the most appropriate management today?

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

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Correct answer: B — Apply a thumb-spica splint and arrange urgent same-day discussion with the hand or plastics service

Explanation lettering: D = shown as B · E = shown as D · B = 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 localised to the ulnar MCP joint, and—crucially—testing after analgesia shows marked valgus laxity without a firm endpoint. A normal radiograph excludes neither complete UCL rupture nor a Stener lesion. She requires thumb-spica immobilisation and urgent same-day hand/plastics assessment, where exploration/repair versus further imaging can be determined. Delaying specialist assessment for ultrasound is inappropriate because ultrasound may be falsely negative and should not replace urgent referral in a clinically complete rupture. A is appropriate for a stable grade I injury, where pain is present but instability is absent. B is attractive because ultrasound can help when the diagnosis is uncertain, but this examination already establishes complete instability. C suits grade I–II UCL injury, where some laxity is present but a firm endpoint remains. E would risk persistent MCP instability and impaired pinch grip in a complete ligament rupture.

Reference: How manage Hand injuries and infections in the ED – Draft 2 (September 2023) — https://www.rightdecisions.scot.nhs.uk/media/3bcjfknw/2023-09-sjh-ed-hand-guidance.pdf Hand Injuries Document (26 November 2025) — https://www.rightdecisions.scot.nhs.uk/media/jujp5l25/hand-injuries-dec-24.pdf