A patient with a closed diaphyseal tibial fracture is being managed in a below-knee cast. On day 3, the patient complains of pain on passive extension of the toes that is disproportionate to the injury. Compartment pressure is measured at 38 mmHg with a diastolic BP of 80 mmHg. What is the delta pressure (ΔP) and should fasciotomy be performed?

• A ΔP = 42 mmHg; fasciotomy is NOT indicated (threshold is ΔP <30 mmHg)
• B ΔP = 42 mmHg; fasciotomy IS indicated because ΔP is below 30 mmHg threshold ✓
• C ΔP = 38 mmHg; fasciotomy NOT indicated because absolute pressure is not >40 mmHg
• D ΔP = 38 mmHg; fasciotomy IS indicated based solely on the absolute compartment pressure

Explanation

Delta pressure (ΔP) = diastolic BP – compartment pressure = 80 – 38 = 42 mmHg. Fasciotomy is indicated when ΔP is ≤30 mmHg (not ≤40 mmHg, which is the older absolute pressure threshold). A ΔP of 42 mmHg is above 30 but the clinical signs—pain on passive stretch, tense compartment—are equally important; however, the 42 mmHg ΔP itself does not mandate fasciotomy by the <30 mmHg criterion. Option B is the distractor here: ΔP of 42 mmHg means fasciotomy is NOT indicated by the <30 criterion. Option A is therefore correct: ΔP is 42 and fasciotomy is not mandated by that measurement alone. The correct answer is A.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.