What is the recommended imaging modality for compartment syndrome?

Imaging for Compartment Syndrome

Compartment syndrome diagnosis is primarily clinical, with imaging playing a supportive role when the diagnosis is uncertain or in clinically ambiguous cases.

Clinical Diagnosis - The Gold Standard

• Compartment syndrome is diagnosed primarily through clinical assessment, which should include evaluation of:

  • Pain (disproportionate to injury, especially on passive stretching)
  • Paresthesia (sensory changes in nerve distribution of affected compartment)
  • Paresis (weakness in muscles of affected compartment)
  • Tension/firmness of the compartment
  • Compartment pressure measurements (>30 mmHg or differential pressure [diastolic BP - compartment pressure] <30 mmHg) 1

• Late signs (often indicating irreversible damage):

  • Pallor
  • Pulselessness
  • Paralysis 1

Imaging Modalities

MRI

• MRI is the most valuable imaging modality for compartment syndrome when clinical diagnosis is uncertain 2
• Findings include:
  • Swollen compartments with loss of normal muscle architecture on T1-weighted images
  • Increased signal intensity on T2-weighted images
  • Enhancement after gadolinium administration
  • In chronic exertional compartment syndrome, post-exercise T2 signal intensity increases by approximately 27.5% in affected compartments 3

Ultrasound

• May be useful in unstable patients to differentiate simple cellulitis from necrotizing fasciitis, which can present similarly to compartment syndrome 1
• Can detect diffuse subcutaneous thickening and fluid accumulation along deep fascial layers

CT Scan

• Limited role in acute compartment syndrome diagnosis
• May be useful to rule out other causes of limb pain or swelling

Plain Radiography

• Not recommended for diagnosis of compartment syndrome 1
• May show indirect signs like fractures that could predispose to compartment syndrome

Important Considerations

1. Do not delay treatment for imaging: Imaging studies should never delay surgical consultation and intervention if compartment syndrome is clinically suspected 1

2. Monitoring after revascularization: In patients with acute limb ischemia, monitoring for compartment syndrome after revascularization is recommended, with fasciotomy if detected 1

3. Risk factors: Be vigilant for compartment syndrome in patients with:

   • Fractures
   • Crush injuries
   • Hemorrhagic injuries
   • Reperfusion of ischemic lesions
   • Hypotension 1

4. Laboratory markers: Monitor for rhabdomyolysis with:

   • Creatine phosphokinase (CPK) levels
   • Myoglobin levels
   • Potassium levels 1

Clinical Pathway

1. For suspected compartment syndrome:

   • Perform thorough clinical assessment (pain, paresthesia, paresis, tension)
   • Measure compartment pressures if available
   • If diagnosis is clear clinically → immediate fasciotomy without imaging
   • If diagnosis is uncertain → consider MRI to confirm diagnosis and identify affected compartments 2

2. For chronic exertional compartment syndrome:

   • MRI before and after exercise showing >20% increase in T2 signal intensity in affected compartments can support diagnosis 3

Pitfalls to Avoid

• Relying solely on imaging when clinical signs are present
• Delaying fasciotomy to obtain imaging studies
• Missing compartment syndrome in sedated or unconscious patients (requires more vigilant monitoring)
• Focusing only on one compartment when multiple may be affected

MRI can help identify which compartments are affected and allow for selective fasciotomy, but should not delay treatment when clinical diagnosis is clear 2.