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Severe pain under a new cast
A 24-year-old man had a closed tibial shaft fracture placed in a long-leg cast 6 hours ago. He now has severe, worsening pain in his leg despite IV opioids.
Step 1 of 4
What is the most likely diagnosis?
Correct answer: A
Pain out of proportion to the injury after a tibial fracture (the most common cause) is acute compartment syndrome until proven otherwise (see compartments of the leg).
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A
Pain out of proportion to the injury after a tibial fracture (the most common cause) is acute compartment syndrome until proven otherwise (see compartments of the leg).
Step 2 of 4
Which examination finding is one of the earliest signs?
Correct answer: B
Pain on passive stretch and pain out of proportion are the earliest signs. Pulselessness and paralysis are late — pulses are usually present.
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B
Pain on passive stretch and pain out of proportion are the earliest signs. Pulselessness and paralysis are late — pulses are usually present.
Step 3 of 4
He has numbness of the first web space of the foot, and plantarflexing his toes is agony.
Which compartment is most involved?
Correct answer: C
Plantarflexing the toes stretches the anterior compartment muscles, and the deep fibular nerve in that compartment supplies the first web space. The anterior compartment is the one most often affected.
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C
Plantarflexing the toes stretches the anterior compartment muscles, and the deep fibular nerve in that compartment supplies the first web space. The anterior compartment is the one most often affected.
Step 4 of 4
What is the definitive management?
Correct answer: D
Remove casts and dressings, keep the limb at heart level (not elevated), and perform an emergency four-compartment fasciotomy. If the diagnosis is uncertain, a delta pressure (diastolic minus compartment pressure) below 30 mm Hg supports fasciotomy.
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D
Remove casts and dressings, keep the limb at heart level (not elevated), and perform an emergency four-compartment fasciotomy. If the diagnosis is uncertain, a delta pressure (diastolic minus compartment pressure) below 30 mm Hg supports fasciotomy.
Key points
- Pain out of proportion + pain on passive stretch → compartment syndrome; pulses are often still present.
- First web space numbness = deep fibular nerve = anterior compartment.
- Treat with emergency fasciotomy; delta pressure < 30 mm Hg if measured.