What is the best imaging study for suspected compartment syndrome with trauma in the leg?

Compartment Syndrome: Clinical Diagnosis Without Routine Imaging

Compartment syndrome is a clinical diagnosis that does not require imaging studies for confirmation—diagnosis relies on clinical examination combined with intracompartmental pressure measurement when the diagnosis is uncertain. 1

Primary Diagnostic Approach

Clinical Examination is the Gold Standard

• The diagnosis of compartment syndrome is fundamentally clinical, with imaging playing no role in the acute diagnostic workup 1
• The most sensitive clinical symptom is severe pain, particularly pain with passive stretching of muscles in the affected compartment 1, 2
• Look for the "four P's": pain, pain with passive stretch, paresthesia, and paresis—these are the actionable early signs 1
• Pulselessness and pallor are late signs indicating irreversible tissue damage has already begun and should never be awaited before intervention 1, 3

When Clinical Examination is Reliable

• In alert, cooperative patients without neurological impairment, serial clinical examination every 30 minutes to 1 hour during the first 24 hours is the recommended diagnostic approach 1
• Document the presence of: spontaneous pain, pain with passive muscle stretching, compartment tension on palpation, paresthesia, and motor weakness 1

Intracompartmental Pressure Measurement

When to Measure Pressure

Pressure measurement should be performed when:

• The clinical diagnosis is uncertain or equivocal 1
• The patient cannot cooperate with serial examination (sedated, altered mental status, neurologically impaired) 1
• The patient has peripheral neuropathy or diabetic neuropathy where pain perception is unreliable 1

Diagnostic Thresholds

• Absolute compartment pressure ≥30 mmHg suggests compartment syndrome but should not be used in isolation 1, 4
• The differential pressure (diastolic blood pressure minus compartment pressure) <30 mmHg is the most recognized threshold for intervention when combined with clinical signs 1, 2
• When combined with clinical findings, this approach has 94% sensitivity and 98% specificity 1

Critical Pitfall: Pressure Measurement Technique

• Using an 18-gauge needle can overestimate compartment pressure by up to 18 mmHg, leading to unnecessary fasciotomies—use a slit catheter or side-ported needle instead 4
• Never rely solely on pressure measurements without clinical correlation—the absence of clinical signs is more accurate in excluding compartment syndrome than their presence is in confirming it 1, 4

Why Imaging is Not Indicated

No Role for Standard Imaging Modalities

• Radiography, CT, MRI, ultrasound, and bone scan have no role in diagnosing compartment syndrome 1
• These modalities may be appropriate for evaluating the underlying traumatic injury (fracture assessment, soft tissue injury) but do not diagnose or exclude compartment syndrome 1

Imaging for Associated Injuries Only

• Plain radiographs are indicated to evaluate for fractures in leg trauma 1
• CT may be useful in polytrauma patients for comprehensive fracture assessment 1
• However, these imaging studies address the traumatic injury itself, not the compartment syndrome 1

Management Algorithm

When compartment syndrome is diagnosed (clinically or by pressure measurement with clinical correlation):

1. Immediate fasciotomy of all involved compartments is required—delays result in irreversible muscle necrosis and nerve damage 3, 5, 2
2. Fasciotomy must be performed before definitive fracture fixation 3
3. The leg has four compartments that typically require decompression via lateral and medial incisions (or single lateral approach in fracture cases) 5, 2

Time-Critical Nature

• Fasciotomy performed before development of myoneural deficits prevents ischemic sequelae 6
• Only 7% of patients had postoperative deficits when fasciotomy was performed early (average 16 hours after injury), and both had preoperative deficits 6

Special Considerations

High-Risk Scenarios Requiring Vigilance

• Tibial shaft fractures (highest risk) 1
• Crush injuries 1
• Vascular injuries with reperfusion 1
• Hypotensive patients (can tolerate less compartment pressure elevation) 1

Monitoring in High-Risk Patients

• Continuous pressure monitoring may be the safest approach when serial examination is unreliable 1
• However, recognize that even this approach may miss some cases by definition 4

The bottom line: Do not order imaging studies to diagnose compartment syndrome. Make the diagnosis clinically, confirm with pressure measurement only when uncertain, and proceed immediately to fasciotomy when diagnosed.