A 35-year-old woman is admitted to the orthopedic ward 18 hours after sustaining a tibia fracture treated with intramedullary nailing. She complains of severe pain in the leg that is not relieved by opioid analgesics. On examination, the leg is markedly swollen and tense. Passive dorsiflexion and plantarflexion of the foot elicit severe pain. She has normal pedal pulses and intact sensation. Compartment pressure measurement shows 65 mmHg in the anterior compartment (normal <12 mmHg). What is the most likely complication, and what is the next step?

Explanation

## Acute Compartment Syndrome: Diagnosis by Compartment Pressure ### Compartment Pressure Interpretation **Key Point:** Compartment syndrome is confirmed when compartment pressure exceeds critical thresholds. The absolute pressure threshold and the delta pressure (mean arterial pressure minus compartment pressure) both guide management. ### Pressure Criteria for Compartment Syndrome | Criterion | Threshold | Clinical Action | |-----------|-----------|------------------| | **Absolute pressure** | ≥30 mmHg (or ≥45 mmHg in some guidelines) | High suspicion; fasciotomy if clinical signs present | | **Delta pressure** (MAP − CP) | <30 mmHg | Fasciotomy indicated | | **Normal compartment pressure** | <12 mmHg | Baseline reference | ### Why This Patient Meets Criteria **High-Yield:** This patient has: 1. **Clinical signs:** Pain out of proportion, pain on passive stretch (dorsi- and plantarflexion), tense swollen compartment 2. **Compartment pressure:** 65 mmHg (well above the 30–45 mmHg threshold) 3. **Timing:** 18 hours post-injury (within the critical window for tissue salvage) 4. **Intact neurovascular exam:** Early stage; late findings (paresthesia, paralysis, absent pulses) indicate irreversible damage **Clinical Pearl:** The combination of clinical signs + elevated compartment pressure is diagnostic. Fasciotomy must be performed immediately to prevent irreversible muscle necrosis and systemic complications (rhabdomyolysis, hyperkalemia, acute kidney injury). ### Why Other Options Are Incorrect **Rhabdomyolysis (Option B):** - Rhabdomyolysis is a *consequence* of untreated compartment syndrome (muscle necrosis → myoglobin release → dark urine, hyperkalemia, AKI), not the primary diagnosis. - While fluid resuscitation is part of rhabdo management, it does NOT address the underlying compartment pressure problem. - The elevated compartment pressure must be relieved surgically first. **DVT (Option C):** - DVT presents with unilateral leg swelling and pain, but compartment pressure is normal. - Duplex ultrasound would not show elevated compartment pressure. - The tense, firm compartment and severe pain on passive stretch are not typical of DVT. **Arterial Insufficiency (Option D):** - Arterial insufficiency presents with absent or diminished pulses, cool extremity, and mottled skin. - This patient has intact pedal pulses and normal sensation (early-stage compartment syndrome). - Angiography is not indicated; the problem is not arterial occlusion but elevated tissue pressure. ### Fasciotomy Technique and Timing ```mermaid flowchart TD A[Tibia fracture + severe pain + tense compartment]:::outcome --> B{Compartment pressure?}:::decision B -->|≥30-45 mmHg| C[Acute compartment syndrome confirmed]:::outcome C --> D[IMMEDIATE fasciotomy]:::urgent D --> E[Anterolateral incision: expose anterior & lateral compartments]:::action D --> F[Separate medial incision if deep/superficial posterior involved]:::action E --> G[Leave fascia open; plan delayed closure at 48-72 hrs]:::action G --> H[Prevent rhabdo, AKI, permanent disability]:::action ``` **Mnemonic:** **ACP** = Absolute Compartment Pressure ≥30–45 mmHg + Clinical signs (pain out of proportion, pain on passive stretch) + Prompt fasciotomy = Prevention of complications. **Warning:** Do NOT delay fasciotomy waiting for: - Rhabdo to develop (it will if you wait) - Duplex ultrasound (not indicated) - Angiography (not indicated) - Late signs like paralysis or absent pulses (by then, damage is irreversible) [cite:Rockwood & Green's Fractures in Adults Ch 1; Campbell's Operative Orthopaedics Ch 57]