A 32-year-old man presents to the emergency department 6 hours after a crush injury to his right leg trapped under a fallen concrete slab at a construction site. Clinical examination reveals severe pain out of proportion to physical findings, pain on passive stretch of foot muscles, and tense compartments. Which is the most common site of compartment syndrome in lower limb crush injuries?

## Compartment Syndrome in Lower Limb Crush Injuries **Key Point:** The anterior compartment of the leg is the most common site of compartment syndrome in lower limb trauma, accounting for approximately 40–50% of cases. ### Why the Anterior Compartment? 1. **Anatomical vulnerability:** The anterior compartment is bounded by the tibia medially, fibula laterally, and the anterior and posterior intermuscular septa. It is a relatively tight, unyielding compartment with limited room for swelling. 2. **Muscle mass and vascularity:** Contains the tibialis anterior, extensor hallucis longus, and extensor digitorum longus — muscles prone to edema and rhabdomyolysis after crush injury. 3. **Pressure dynamics:** Swelling in this compartment rapidly elevates intracompartmental pressure due to its rigid fascial boundaries. ### Comparative Frequency of Compartment Syndrome Sites (Lower Limb) | Compartment | Frequency | Key Features | |---|---|---| | Anterior | 40–50% | Most common; tibialis anterior involved | | Posterior (superficial) | 20–30% | Gastrocnemius, soleus | | Posterior (deep) | 15–20% | Tibialis posterior, flexor digitorum | | Lateral | 10–15% | Peroneal muscles; least common | **High-Yield:** In crush injuries, the anterior compartment is affected first and most severely because it has the highest metabolic demand and least compliance. **Clinical Pearl:** Pain on passive dorsiflexion (stretch of anterior compartment muscles) is the most sensitive early sign of anterior compartment syndrome. ### Pathophysiology in Crush Injury 1. Direct muscle trauma → myonecrosis and rhabdomyolysis 2. Inflammatory edema and fluid extravasation into compartment 3. Intracompartmental pressure rises above capillary perfusion pressure (~30 mmHg) 4. Ischemia → further muscle necrosis → positive feedback loop 5. Fasciotomy required within 6–8 hours to prevent irreversible damage **Warning:** Delay in diagnosis and fasciotomy leads to permanent contracture (Volkmann's ischemic contracture), loss of function, and systemic complications (acute kidney injury from myoglobinuria).