What is the best imaging modality for diagnosing compartment syndrome in a patient with a history of trauma, considering factors such as age, medical history, and mechanism of injury?

Imaging for Compartment Syndrome

Compartment syndrome is a clinical diagnosis that does not require imaging for confirmation, and imaging should never delay emergency fasciotomy when clinical suspicion is high. 1, 2

Primary Diagnostic Approach

Clinical Diagnosis is Paramount

• Compartment syndrome must be diagnosed clinically based on physical examination findings, with imaging playing no role in acute decision-making for fasciotomy. 2, 3
• The diagnosis relies on pain out of proportion to injury (earliest sign), pain with passive muscle stretching (most sensitive early sign), paresthesias, paresis, and a tense compartment. 1, 2
• Do not wait for imaging or late signs (pulselessness, pallor, paralysis) as these indicate irreversible arterial occlusion and tissue damage. 1, 2

Compartment Pressure Measurement (Not Imaging)

• When clinical diagnosis is uncertain (obtunded, confused, or pediatric patients), measure compartment pressures directly rather than obtaining imaging. 1
• Fasciotomy is indicated when pressures are ≥30 mmHg in normotensive patients or differential pressure (diastolic BP minus compartment pressure) <30 mmHg. 1

Limited Role of Imaging Modalities

MRI: Only for Ambiguous or Chronic Cases

• MRI has no role in acute compartment syndrome where clinical suspicion warrants immediate fasciotomy. 3
• MRI may help in clinically ambiguous cases by showing swollen compartments with loss of normal muscle architecture on T1-weighted images and bright areas on T2-weighted sequences that enhance with gadolinium. 4
• For chronic exertional compartment syndrome, post-exercise MRI shows a 27.5% increase in T2-weighted signal intensity in affected compartments compared to 7.6% in normal controls. 5
• MRI can identify which specific compartments are affected to guide selective fasciotomy, but this is relevant only after the decision to operate has been made. 4

CT: For Associated Trauma, Not Compartment Syndrome Diagnosis

• CT has no direct role in diagnosing compartment syndrome itself. 6
• In polytrauma patients with suspected compartment syndrome, contrast-enhanced CT of the chest, abdomen, and pelvis may be indicated to evaluate for associated injuries (fractures, vascular injuries, solid organ trauma). 6
• CT can demonstrate fractures and vascular injuries that are risk factors for compartment syndrome development, but cannot diagnose the compartment syndrome itself. 1, 7

Plain Radiography: Only for Associated Fractures

• Plain radiographs cannot diagnose compartment syndrome but may identify associated tibial shaft fractures (highest risk fracture for compartment syndrome). 1
• Trauma series radiographs (chest and pelvis) are appropriate for initial polytrauma evaluation but do not assess compartment pressures. 6

Ultrasound: No Role

• Ultrasound has no established role in diagnosing compartment syndrome. 6
• FAST examination is used for trauma triage but cannot evaluate compartment pressures or muscle ischemia. 6

Critical Management Priorities

Immediate Actions Without Imaging

• Remove all constricting dressings, casts, or bandages immediately when compartment syndrome is suspected. 1
• Position the limb at heart level—avoid elevation as this reduces perfusion pressure. 1
• Obtain immediate orthopedic surgery consultation without waiting for any imaging studies. 1

High-Risk Scenarios Requiring Heightened Vigilance

• Tibial shaft fractures (4-5% develop compartment syndrome), especially in young males under 35 years. 1
• Vascular injury combined with fractures creates particularly high risk requiring monitoring every 30-60 minutes for 24 hours. 1
• Crush injuries, hemorrhagic injuries, reperfusion after ischemia, and patients on anticoagulation. 1, 8

Common Pitfalls to Avoid

• Never delay fasciotomy to obtain imaging studies when clinical diagnosis is evident—time beyond 6-8 hours significantly increases irreversible damage. 1, 2
• Do not rely on preserved pulses to exclude compartment syndrome—pulses remain intact until late arterial occlusion occurs. 2, 9
• Imaging cannot exclude compartment syndrome; a negative or normal imaging study does not rule out the diagnosis when clinical suspicion remains high. 3