Compartment Syndrome
Rising pressure within a closed fascial compartment collapses capillary perfusion long before it occludes major arteries, causing muscle and nerve ischaemia while pulses are still present, and demanding emergency fasciotomy.
In a nutshell
Compartment syndrome is rising pressure within a closed fascial compartment that collapses capillaries and causes muscle and nerve ischaemia at pressures far below arterial occlusion, so distal pulses remain present until very late. It is a clinical diagnosis (pain out of proportion and pain on passive stretch) treated by emergency fasciotomy, not observation.
Classic presentation
Severe pain out of proportion to a limb fracture, worsening despite analgesia, with a tense swollen compartment and severe pain on passive stretch of the digits, but normal distal pulses.
Key points
- Capillaries collapse once compartment pressure approaches diastolic pressure, far below the pressure needed to occlude a major artery: pulses are preserved until very late and cannot be used to exclude the diagnosis.
- Pain out of proportion and pain on passive muscle stretch are the earliest and most reliable signs; pallor, paraesthesia, paralysis and pulselessness are late and unreliable.
- It is fundamentally a clinical diagnosis. Intracompartmental pressure measurement supports but does not replace clinical judgement, especially in an unreliable or unconscious patient.
- Elevation above heart level can reduce perfusion pressure and worsen ischaemia: keep the limb at heart level and remove all constricting dressings or casts immediately.
- The only effective treatment is emergency fasciotomy; delay risks irreversible muscle necrosis, contracture and rhabdomyolysis-induced kidney injury.
First-line investigation
Clinical assessment with serial examination for pain out of proportion and pain on passive stretch; intracompartmental pressure measurement supports the diagnosis when clinical assessment is equivocal.
First-line management
Remove all constrictive dressings or casts immediately and escalate for emergency fasciotomy without waiting for confirmatory investigations if clinical suspicion is high.
Exam traps
- Preserved distal pulses do not exclude compartment syndrome: do not be falsely reassured.
- Elevating the limb above heart level can worsen ischaemia by lowering perfusion pressure; keep it at heart level.
- An escalating analgesia requirement in a fracture patient is a red flag, not just 'bad pain control'.
- Waiting for pallor, paralysis or pulselessness before acting is too late: these are late, unreliable signs.
Educational content pending clinical review. Not medical advice.