Compartment syndrome is a surgical emergency caused by increased pressure within a closed muscle compartment, leading to ischemia and possible irreversible muscle and nerve damage. Clinical diagnosis is paramount, but imaging can support diagnosis, exclude mimics, and assess complications.
📌 Role of Imaging
While clinical exam + compartment pressure measurement are gold standards, imaging is helpful in:
- Equivocal cases.
- Excluding differential diagnoses (fracture, DVT, cellulitis).
- Detecting complications (muscle necrosis, myonecrosis, fasciitis).
🔍 Imaging Modalities
1. Plain Radiograph
- Usually normal.
- Can show underlying cause: fracture, dislocation, penetrating injury.
2. Ultrasound (USG)
- Bedside, rapid, radiation-free.
- Findings:
- Increased echogenicity of muscle.
- Loss of normal fibrillar architecture.
- Muscle herniation through fascial defects.
- Can exclude DVT (common mimic).
- Limitation: Operator dependent.
3. CT
- Detects associated fractures.
- Contrast-enhanced CT may show reduced muscle enhancement, swelling, fascial thickening.
- Useful in trauma settings when MRI not available.
4. MRI (Most Sensitive)
- Best for early diagnosis and extent of injury.
- Findings:
- Muscle swelling and edema → hyperintense on T2/STIR, hypointense on T1.
- Loss of normal fascial planes.
- Compartmental fluid collections.
- Late stage: muscle necrosis (non-enhancing areas after contrast).
- Helps differentiate from cellulitis, necrotizing fasciitis, myositis.
5. Near-Infrared Spectroscopy (Research use)
- Evaluates tissue oxygenation in real time.
- Still experimental, not routine.
📍 Teaching Pearls
- Imaging is supportive—do not delay fasciotomy in clinically suspected cases.
- MRI is most sensitive for muscle ischemia and necrosis.
- USG is a good bedside tool for excluding mimics like DVT.
- Always look for underlying cause: fracture, soft tissue injury, vascular compromise.
Imaging in Compartment Syndrome – Modality Comparison
| Imaging Modality | Key Role | Findings | Limitations |
|---|---|---|---|
| X-ray | Rules out fracture/dislocation | May show fracture, foreign body, gas | Does not show compartment pressure or muscle ischemia |
| Ultrasound (USG) | Rapid, bedside, excludes mimics | Muscle swelling, echogenicity changes, fascial defect, DVT exclusion | Operator dependent, poor for deep compartments |
| CT | Trauma evaluation, bone + soft tissue | Muscle swelling, fascial thickening, reduced enhancement | Less sensitive than MRI for early ischemia |
| MRI | Most sensitive for early diagnosis | T2/STIR hyperintensity (edema), fascial plane loss, non-enhancing necrotic areas | Time-consuming, not always available in emergency |
| Near-Infrared Spectroscopy (NIRS) | Research/experimental | Detects reduced tissue oxygenation | Not widely available, not standard |
✅ Takeaway:
- X-ray → fractures, USG → bedside + exclude DVT, CT → trauma setting, MRI → gold standard for early ischemia/necrosis.
- Imaging should never delay urgent fasciotomy in a strong clinical setting.
