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Acute compartment syndrome of the lower leg — MSRA MCQ

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HardAnkle and FootAcute compartment syndrome of the lower legMSRA

A 34-year-old man attends an urgent treatment centre 7 hours after closed reduction of a bimalleolar ankle fracture. He was discharged from the emergency department in a circumferential below-knee fibreglass cast. During the past 3 hours he has developed rapidly increasing, severe pain in the lower leg despite paracetamol, ibuprofen and oral morphine. He describes a tight, bursting sensation and new tingling over the dorsum of the foot. The cast feels tight. The anterolateral lower-leg compartment is tense, and passive movement of the toes markedly worsens the pain. The toes are warm with capillary refill of 2 seconds; dorsalis pedis pulse is palpable. What is the most appropriate immediate management?

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

Reveal the answer and explanation

Correct answer: D — Split the cast and all undercast layers to the skin immediately, then arrange emergency orthopaedic assessment

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

This is suspected acute compartment syndrome of the lower leg. The decisive features are escalating pain disproportionate to the injury despite opioid analgesia, a tense compartment, pain on passive toe movement and evolving paraesthesia after application of a circumferential cast. A palpable pulse and preserved capillary refill do not exclude compartment syndrome: vascular compromise and pulselessness are late findings. The cast and every undercast layer must be split down to the skin immediately to remove external constriction, while emergency orthopaedic assessment is arranged. Acute compartment syndrome is a time-critical surgical emergency; definitive management may require fasciotomy. A is inappropriate because analgesic escalation and high elevation delay decompression; marked elevation may further reduce perfusion pressure. C is initially plausible in an immobilised patient with leg pain, but DVT does not explain a tense compartment and severe pain on passive stretch. D may be appropriate for suspected loss of reduction, but imaging must not delay treatment of suspected compartment syndrome. E is inappropriate because pressure measurement can assist diagnostic uncertainty in hospital, but should not delay urgent decompression measures and orthopaedic escalation when the clinical suspicion is high.

Reference: Compartment syndrome (Reviewed 4 January 2025) — https://www.rightdecisions.scot.nhs.uk/south-east-scotland-major-trauma-guidelines/orthopaedicsplastics/compartment-syndrome/ Compartment syndrome (Last reviewed 9 February 2023) — https://www.nhs.uk/conditions/compartment-syndrome/