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Bony mallet finger — MSRA MCQ

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ModerateSoft Tissue InjuryBony mallet fingerMSRA

A 24-year-old right-hand-dominant amateur cricketer attends a GP-led urgent treatment centre 2 hours after a cricket ball struck the tip of his left ring finger. The distal interphalangeal (DIP) joint was forcibly flexed. He has pain, swelling and a 25-degree extensor lag at the DIP joint. The skin is intact and there is no neurovascular deficit. True anteroposterior and lateral radiographs show a displaced dorsal avulsion fragment from the base of the distal phalanx involving approximately 35% of the DIP articular surface. The DIP joint remains congruent, with no volar subluxation. What is the most appropriate management now?

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Correct answer: E — Apply a mallet splint, obtain a repeat radiograph in the splint, and make an urgent hand/plastics referral for consideration of fixation

This is a bony mallet injury: forced DIP flexion has avulsed the terminal extensor tendon insertion with a dorsal fragment from the distal phalanx. The decisive feature is that the fragment involves approximately 35% of the articular surface. UK NHS emergency hand guidance advises splintage, repeat radiography in the splint and hand/plastics referral for consideration of internal fixation when a bony mallet involves more than 30% of the articular surface. The absence of volar DIP subluxation does not remove this referral indication. Option D would be appropriate for a smaller, stable bony mallet injury involving less than 30% of the articular surface. Option A is the usual duration for a soft-tissue mallet injury, in which there is terminal extensor tendon disruption without an avulsion fracture. Neighbour strapping in D does not maintain DIP extension and is inappropriate for an extensor mechanism injury. Option B positions the DIP joint incorrectly: a mallet splint should maintain the DIP joint in extension while allowing movement at the proximal interphalangeal joint.

Reference: How manage Hand injuries and infections in the ED (September 2023) — https://www.rightdecisions.scot.nhs.uk/media/3bcjfknw/2023-09-sjh-ed-hand-guidance.pdf Mallet finger (Reviewed 2 August 2023) — https://www.nhs.uk/conditions/mallet-finger/