A 32-year-old male presents to the emergency department 6 hours after a motor vehicle accident with a closed fracture of the right femur. On examination, the limb is swollen and tense. Compartment pressure measured at the anterior compartment is 65 mmHg (diastolic blood pressure = 80 mmHg). The patient reports severe pain out of proportion to the clinical findings and pain with passive dorsiflexion of the foot. What is the most appropriate next step in management?

Explanation

## Acute Compartment Syndrome (ACS) — Recognition and Management ### Clinical Presentation This patient demonstrates the classic triad of acute compartment syndrome (ACS): - **Severe pain out of proportion** to the clinical injury - **Pain with passive stretch** of muscles in the affected compartment (passive dorsiflexion = anterior compartment pain) - **Tense, swollen compartment** with elevated pressure ### Compartment Pressure Interpretation **Key Point:** The diagnosis of ACS is based on the **pressure gradient**, not absolute pressure alone. $$\text{Pressure Gradient} = \text{Compartment Pressure} - \text{Diastolic BP}$$ In this case: - Compartment pressure = 65 mmHg - Diastolic BP = 80 mmHg - Gradient = 65 − 80 = −15 mmHg (or effectively, compartment pressure within 30 mmHg of diastolic BP) **High-Yield:** A compartment pressure **≥30 mmHg below diastolic BP** (or ≥45 mmHg absolute in hypotensive patients) is diagnostic of ACS and warrants **immediate fasciotomy**. ### Fasciotomy Indications | Finding | Action | |---------|--------| | Clinical signs + high pressure | Fasciotomy without delay | | Equivocal signs + borderline pressure | Measure pressure serially; fasciotomy if trend worsens | | Pressure gradient ≥30 mmHg below DBP | **Emergency fasciotomy** | | Pain with passive stretch | Strong clinical indicator for fasciotomy | **Clinical Pearl:** ACS is a **surgical emergency**. Delay >6–8 hours from onset leads to irreversible muscle necrosis, contracture, and permanent disability. The "6-hour rule" is a rough guideline, but clinical judgment (pain, pressure gradient) takes precedence. ### Why Fasciotomy Now? 1. **Pressure gradient** is in the critical range (≥30 mmHg below DBP) 2. **Clinical signs** are unequivocal (pain on passive stretch, severe pain out of proportion) 3. **Time-sensitive**: Muscle ischemia becomes irreversible after 6–8 hours 4. **Two-incision fasciotomy** of anterior and lateral compartments is standard for femoral fracture ACS **Mnemonic: "5 P's" of ACS** — **P**ain (out of proportion), **P**ressure (elevated compartment), **P**ain with passive stretch, **P**allor, **P**ulselessness (late sign). The first three are present here. ### Post-Fasciotomy Management - Leave wound open; plan delayed closure or skin grafting in 3–5 days - Manage fracture separately (ORIF vs. external fixation) - Monitor for rhabdomyolysis complications (hyperkalemia, acute kidney injury)