A patient with a closed tibial shaft fracture develops compartment syndrome 6 hours after immobilization in a backslab. The measured compartment pressure is 38 mmHg, and the patient's diastolic BP is 65 mmHg. The absolute compartment pressure threshold for fasciotomy in this context is reached. Which formula and threshold confirms the indication for fasciotomy?

• A Delta pressure (diastolic BP − compartment pressure) < 30 mmHg ✓
• B Absolute compartment pressure > 40 mmHg regardless of blood pressure
• C Compartment pressure > 20 mmHg with clinical signs alone, regardless of delta pressure
• D Compartment pressure > 60 mmHg

Explanation

The most clinically validated threshold for fasciotomy is the delta pressure (ΔP) = diastolic BP − compartment pressure < 30 mmHg. In this patient: ΔP = 65 − 38 = 27 mmHg < 30 mmHg — fasciotomy is indicated. Whitesides' absolute pressure threshold of >30 mmHg within 30 mmHg of diastolic is equivalent. An absolute threshold of >30 mmHg alone (or >40 mmHg) is used in some guidelines but ΔP is more sensitive in hypotensive patients, as a low pressure is more dangerous when perfusion pressure is already reduced. Clinical signs (pain with passive stretch, tense compartment) support but the ΔP formula guides the decision.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.