What are the diagnostic criteria for compartment syndrome?

How to Diagnose Compartment Syndrome

Compartment syndrome is diagnosed primarily through clinical examination based on pain out of proportion to injury and pain with passive muscle stretch, with compartment pressure measurement reserved only for cases where clinical diagnosis remains uncertain, particularly in obtunded, sedated, or uncooperative patients. 1

Primary Clinical Diagnostic Criteria

The diagnosis relies on recognizing the "four P's" in at-risk patients:

• Pain out of proportion to injury is the earliest and most reliable warning sign of acute compartment syndrome 2, 1
• Pain with passive stretch of the affected muscle compartment is considered the most sensitive early sign 2, 1
• Paresthesia (sensory changes) indicates nerve ischemia within the compartment 1
• Paresis (motor deficits) is a late sign indicating significant tissue damage 1

Critical caveat: Pulselessness and pallor are too late signs that often reflect irreversible compartment syndrome when present 2. Never wait for these findings to make the diagnosis.

Understanding Diagnostic Limitations

Clinical examination has important performance characteristics that must be understood:

• Severe pain alone provides only approximately 25% positive predictive value for compartment syndrome 1
• When both severe pain AND pain on passive stretch are present, positive predictive value increases to 68% 1
• When pain, pain on passive stretch, AND paralysis are all present, positive predictive value reaches 93%, but paralysis indicates irreversible muscle ischemia may have already occurred 1
• Clinical signs have low sensitivity but high negative predictive value - meaning their absence is more useful for ruling out compartment syndrome than their presence is for ruling it in 2
• Palpation alone is unreliable (sensitivity 54%, specificity 76% in children) 1

When to Measure Compartment Pressure

Measure compartment pressures only if clinical diagnosis remains in doubt, particularly in obtunded, sedated, confused, or uncooperative patients who cannot report pain. 1

Pressure Measurement Technique and Thresholds:

• Use traditional needle manometry, multiparameter monitors, or dedicated transducer-tipped intracompartmental pressure monitors 1
• Fasciotomy is indicated when:
  • Absolute compartment pressure ≥30 mmHg, OR
  • Differential pressure (diastolic blood pressure minus compartment pressure) ≤30 mmHg 1
• The differential pressure threshold is the most recognized cut-off for intervention in current practice 1

Important technical consideration: Using an 18-gauge needle can overestimate compartment pressure by up to 18 mmHg compared to a slit catheter or side-ported needle, potentially leading to unnecessary fasciotomies 3

Monitoring Protocol for High-Risk Patients

In patients with severe limb trauma presenting one or more risk factors (fracture, crush injury, hemorrhagic injury, reperfusion of ischemic lesion, hypotension), investigate repetitively every 30 minutes to 1 hour during the first 24 hours for the presence of clinical signs 2:

• Spontaneous pain or pain with passive flexion/extension
• Increasing tension/firmness of the compartment
• Paresthesia
• Paresis
• Rising compartment pressure measurements (if monitoring)

High-Risk Populations Requiring Heightened Surveillance

• Young men under 35 years with tibial fractures 1, 4
• Tibial shaft fractures (highest risk at approximately 4-5% incidence) 4
• Crush injuries or high-energy trauma 1, 4
• Vascular injuries requiring revascularization 1, 4
• Burns 1
• Patients on anticoagulation 1, 4

Role of Imaging (Limited)

Do not order imaging studies that delay surgical intervention. 1

• Plain X-rays should not be used to rule out compartment syndrome and are frequently normal 1
• CT has higher sensitivity than plain radiography, showing fat stranding, fluid collections, and fascial thickening, but should not delay treatment 1
• Ultrasound has no established role in acute compartment syndrome diagnosis 1

Immediate Management When Compartment Syndrome is Suspected

1. Remove all constricting dressings, casts, or splints immediately 1
2. Position the limb at heart level (not elevated, as elevation can further decrease perfusion pressure) 1
3. Arrange urgent surgical consultation for fasciotomy without delay 1
4. Measure compartment pressures only if diagnosis remains in doubt 1

Special Considerations for Obtunded Patients

In sedated, obtunded, or unconscious patients where clinical signs cannot be elicited:

• Direct compartment pressure measurement is indicated 1, 5
• Continuous compartment pressure monitoring may be considered in high-risk patients 1
• Maintain an even higher index of suspicion, as these patients are at risk for delayed diagnosis 5
• Document any physical examination changes carefully and frequently 5

Critical Pitfalls to Avoid

• Never wait for pulselessness, pallor, or paralysis - these indicate irreversible damage 2, 1
• Never rely solely on palpation for diagnosis 1
• Never rely solely on pressure measurements without clinical correlation - no single sign or investigation is guaranteed to diagnose or exclude compartment syndrome 3
• Never elevate the limb excessively when compartment syndrome is suspected, as this worsens perfusion 1
• Never miss compartment syndrome in patients without fractures - it can occur with soft tissue injuries alone 1