An 8-year-old girl is brought to the orthopaedic clinic 3 days after sustaining a supracondylar fracture of the humerus treated with closed reduction and posterior backslab immobilization in the emergency department. On review, she complains of pain in the hand and the parents report that her fingers appear swollen and slightly blue. Examination reveals a tense compartment in the forearm, pain on passive extension of fingers, and diminished sensation in the radial nerve distribution. X-rays show the fracture is well-reduced and aligned. What is the most likely diagnosis and the most appropriate next step?

Explanation

## Acute Compartment Syndrome Following Supracondylar Fracture ### Clinical Presentation Recognition This child presents with the **classic pentad of compartment syndrome** 3 days post-injury: | Finding | Clinical Significance | |---------|----------------------| | Tense, swollen forearm compartment | Increased intracompartmental pressure | | Pain out of proportion to injury | Early sign of ischaemia | | Pain on passive finger extension | Pathognomonic for compartment syndrome | | Swollen, blue fingers | Venous congestion and impending ischaemia | | Diminished sensation (radial nerve) | Nerve ischaemia from pressure | **High-Yield:** The **pain on passive stretch of muscles in the affected compartment** is the most sensitive and earliest clinical sign of compartment syndrome. Do not wait for pulselessness, paralysis, or paresthesias—these are late findings. ### Why This Is NOT the Other Diagnoses **Key Point:** Volkmann's contracture is the **end-stage sequela** of untreated compartment syndrome (fibrosis and muscle death). It develops over weeks to months, not acutely. The current presentation is **acute compartment syndrome**, not chronic contracture. ### Pathophysiology of Compartment Syndrome in Supracondylar Fractures ```mermaid flowchart TD A[Supracondylar fracture + swelling]:::outcome --> B[Increased pressure in forearm compartments]:::outcome B --> C{Pressure exceeds capillary perfusion pressure<br/>~30-40 mmHg?}:::decision C -->|Yes| D[Muscle and nerve ischaemia]:::urgent D --> E[Pain on passive stretch]:::outcome D --> F[Sensory/motor loss]:::outcome E --> G[Emergency fasciotomy]:::action G --> H[Salvage muscle function]:::outcome C -->|No| I[Observation with elevation<br/>and analgesia]:::action ``` **Clinical Pearl:** Compartment syndrome is a **surgical emergency**. The window for salvage is narrow (4–6 hours of ischaemia causes irreversible muscle necrosis). Fasciotomy must be performed urgently to prevent Volkmann's contracture, which is a devastating permanent disability. ### Diagnostic Confirmation (if clinical diagnosis is uncertain) - **Compartment pressure measurement:** >30 mmHg absolute or within 30 mmHg of diastolic BP is diagnostic. - **Clinical diagnosis alone is sufficient** if signs are clear (pain on passive stretch + tense compartment + neurological changes). - **Do NOT delay fasciotomy** while awaiting imaging or pressure measurement. ### Surgical Management 1. **Emergency fasciotomy** of the affected compartments (usually volar and dorsal forearm compartments). 2. Performed through longitudinal incisions to decompress the compartments. 3. Wounds are left open initially and closed after swelling subsides (delayed primary closure or skin grafting). 4. The fracture is typically stabilized with percutaneous pinning once the acute emergency is managed. **Mnemonic:** **"6 P's of Compartment Syndrome"** — Pain (out of proportion), Pressure (tense compartment), Paresthesias, Pallor, Pulselessness, Paralysis. **Pain and Pressure are earliest; Pulselessness and Paralysis are late.** [cite:Campbell's Operative Orthopaedics 13e Ch 53; Rockwood & Green's Fractures in Adults 9e Ch 11]