A 28-year-old male presents with acute compartment syndrome of the forearm following a supracondylar fracture of the humerus sustained 4 hours ago. Which is the most common cause of compartment syndrome in the upper limb?

Explanation

## Most Common Cause of Upper Limb Compartment Syndrome **Key Point:** Supracondylar fracture of the humerus is the most common cause of compartment syndrome in the upper limb, particularly in children and young adults. ### Why Supracondylar Fracture? 1. **High incidence of fracture:** Supracondylar fractures account for 50–60% of all pediatric elbow fractures and are the most frequent elbow injury in children. 2. **Mechanism of compartment syndrome:** - Direct trauma and displacement of fracture fragments - Soft tissue crush and hemorrhage into the anterior compartment of the forearm - Swelling and edema in the tight fascial compartments of the forearm - Brachial artery injury or compression (occurs in 5–10% of supracondylar fractures) 3. **Anatomical factors:** The forearm has tight, unyielding fascial compartments (volar and dorsal), making it vulnerable to pressure elevation after trauma. ### Comparative Causes of Upper Limb Compartment Syndrome | Cause | Frequency | Clinical Context | |---|---|---| | Supracondylar fracture | 40–50% | Most common; pediatric trauma | | Crush injury | 15–25% | Industrial, motor vehicle accidents | | Tight cast/dressing | 10–15% | Iatrogenic; post-fracture immobilization | | Arterial injury/puncture | 5–10% | Vascular trauma, cannulation complications | | Rhabdomyolysis | 5–10% | Exertion, crush, statins, toxins | **High-Yield:** In children presenting with supracondylar fracture, compartment syndrome can develop within hours; clinical suspicion must be high, and early fasciotomy may be life-limb saving. **Clinical Pearl:** The "5 P's" of compartment syndrome — Pain (out of proportion), Pressure (tense compartment), Paresthesia, Pallor, Pulselessness — are late findings. Pain with passive stretch is the earliest and most sensitive sign. ### Pathophysiology in Supracondylar Fracture ```mermaid flowchart TD A[Supracondylar fracture]:::outcome --> B[Direct soft tissue trauma<br/>Brachial artery injury]:::outcome B --> C[Hemorrhage into forearm<br/>compartments]:::outcome C --> D[Edema and inflammation]:::outcome D --> E[Intracompartmental pressure rises]:::outcome E --> F{Pressure > 30 mmHg?}:::decision F -->|Yes| G[Ischemia of muscles<br/>and nerves]:::urgent G --> H[Fasciotomy required<br/>within 6-8 hours]:::action F -->|No| I[Observation and<br/>serial assessment]:::action ``` **Warning:** Pulselessness does NOT rule out compartment syndrome; a palpable pulse can coexist with elevated compartment pressure. Diagnosis is clinical (pain out of proportion) and confirmed by compartment pressure measurement (>30 mmHg absolute or within 30 mmHg of diastolic BP).