A 28-year-old male presents to the emergency department 6 hours after a crush injury to his left leg sustained in a motor vehicle accident. On examination, the leg is swollen and tense. He complains of severe pain out of proportion to the clinical findings, especially on passive dorsiflexion of the foot. Sensation over the dorsum of the foot is intact. Pedal pulses are palpable bilaterally. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis: Acute Compartment Syndrome **Key Point:** Compartment syndrome is a surgical emergency characterized by increased pressure within a closed fascial space, compromising tissue perfusion and function. Early recognition and intervention are critical to prevent irreversible tissue damage and loss of limb function. ### Pathophysiology In this case, the crush injury has caused soft tissue trauma and edema within the anterior compartment of the leg. The rigid fascial boundaries prevent expansion, leading to: 1. Increased intracompartmental pressure 2. Decreased capillary perfusion pressure 3. Ischemia of muscle and nerve tissue 4. Risk of rhabdomyolysis, acute kidney injury, and permanent disability ### Classic Clinical Features ("5 P's" — though pain and pressure are earliest) | Feature | Timing | Significance | |---------|--------|---------------| | **Pain out of proportion** | Early (within 6–8 hours) | Most sensitive early sign | | **Pain on passive stretch** | Early | Highly specific for compartment syndrome | | **Paresthesias** | Later (8–12 hours) | Nerve ischemia | | **Pallor** | Late | Indicates severe ischemia | | **Pulselessness** | Very late | Sign of irreversible damage | | **Paralysis** | Very late | Permanent if not intervened | **High-Yield:** Intact pulses and normal sensation do NOT exclude compartment syndrome. Vascular compromise and neurologic deficit are LATE findings; by then, irreversible muscle necrosis has begun. ### Diagnostic Approach **Clinical diagnosis** is based on: - High-risk mechanism (crush, fracture, tight cast, rhabdomyolysis) - Pain out of proportion to injury - Pain on passive stretch of muscles in the affected compartment - Tense, swollen compartment **Intracompartmental pressure measurement** is indicated when: - Clinical suspicion is high but not absolutely certain - Patient is unconscious or unreliable historian - Multiple compartments may be involved - Borderline clinical presentation **Fasciotomy threshold:** Pressure ≥30 mmHg absolute, or within 30 mmHg of diastolic BP ("delta P ≤ 30"), mandates urgent surgical decompression. ### Why This Patient Needs Pressure Measurement and Fasciotomy The patient has: - Crush injury (high-risk mechanism) - Severe pain out of proportion (6 hours post-injury) - Pain on passive dorsiflexion (stretch of anterior compartment muscles) - Tense leg swelling - Intact pulses and sensation (does NOT rule out early compartment syndrome) **Clinical Pearl:** The presence of normal neurovascular exam in the first 6–8 hours does NOT exclude compartment syndrome. Waiting for late signs (paresthesia, pallor, pulselessness, paralysis) results in permanent disability or amputation. ### Management Algorithm ```mermaid flowchart TD A[Crush injury / fracture / tight cast]:::outcome --> B{High clinical suspicion<br/>for compartment syndrome?}:::decision B -->|Yes: pain out of proportion<br/>+ pain on passive stretch| C[Measure intracompartmental pressure]:::action B -->|No clear signs| D[Observe closely, repeat exam q1h]:::action C --> E{Pressure ≥30 mmHg<br/>or ≤30 mmHg from diastolic?}:::decision E -->|Yes| F[Urgent fasciotomy]:::urgent E -->|No, but high suspicion| G[Repeat pressure in 1–2 hours<br/>or proceed to fasciotomy if clinical worsening]:::action F --> H[Prevent rhabdomyolysis complications]:::outcome D --> I{Worsening pain<br/>or new neurologic signs?}:::decision I -->|Yes| C I -->|No| J[Discharge with strict follow-up]:::action ``` **Tip:** In NEET PG exams, if the stem describes pain out of proportion + pain on passive stretch + high-risk mechanism, the answer is almost always "measure pressure and fasciotomize if elevated." Do NOT wait for late signs. ### Why Other Options Are Wrong **Option 1 (Antibiotics and observation):** Compartment syndrome is a mechanical emergency, not an infection. Antibiotics are irrelevant. Observation alone allows irreversible ischemic damage to progress. **Option 4 (Ice, elevation, NSAIDs):** These are appropriate for simple contusion or mild swelling, NOT for compartment syndrome. Elevation may worsen compartment pressure by reducing perfusion gradient. Waiting 12 hours for imaging is catastrophic — by then, muscle necrosis is established. [cite:Rockwood & Green's Fractures in Adults 9e Ch 1; Campbell's Operative Orthopaedics 13e Ch 48]