Orthopedic Trauma — Diagnosis of Acute Compartment Syndrome
A 24-year-old man is brought in 4 hours after a motorcycle crash with a closed fracture of the left tibial shaft. He has severe leg pain out of proportion to the injury despite opioids, a tense swollen calf, and marked pain on passive stretch of the toes. Dorsalis pedis pulse is palpable. Which investigation most directly confirms the suspected diagnosis?
- A.Magnetic resonance imaging of the leg
- B.Plain radiograph of the tibia and fibula
- C.Intracompartmental pressure measurementCorrect
- D.Arterial duplex ultrasound of the leg
Explanation
Severe pain beyond what the fracture explains, pain on passive stretch of the muscles in the compartment and a tense calf after a tibial shaft fracture point to acute compartment syndrome. It remains primarily a clinical diagnosis, and a patient with these unequivocal findings should go straight to fasciotomy; testing must never delay theatre. When objective confirmation is wanted, or the examination is unreliable because the patient is sedated, intubated, intoxicated or has a nerve injury, the only test that measures the problem itself is direct intracompartmental pressure measurement with a needle or slit catheter. A delta pressure, diastolic blood pressure minus compartment pressure, of 30 mm Hg or less supports the diagnosis and the need for decompression; an absolute pressure above about 30 mm Hg is the older threshold. A palpable distal pulse does not exclude the condition, because tissue pressure that kills muscle is still far below arterial pressure, and loss of pulses is a late sign. Imaging shows the fracture or vessel flow but cannot quantify tissue pressure, so it neither confirms nor excludes compartment syndrome.
Why each option
- A.
- Magnetic resonance imaging may show muscle oedema, but it is slow, does not quantify compartment pressure and would dangerously delay fasciotomy.
- B.
- A plain radiograph characterises the fracture but gives no information about tissue pressure or muscle perfusion within the compartment.
- C.
- Correct. Direct needle or catheter pressure measurement, using a delta pressure of 30 mm Hg or less, objectively confirms compartment syndrome.
- D.
- Duplex ultrasound assesses arterial flow, which is usually preserved in compartment syndrome because distal pulses are lost only very late.
Reference: BOAST — Diagnosis and Management of Compartment Syndrome of the Limbs (British Orthopaedic Association, 2014); AAOS Clinical Practice Guideline — Management of Acute Compartment Syndrome 2018; UpToDate — Acute compartment syndrome of the extremities
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