A 6-year-old boy presents to the emergency department after a fall on outstretched hand (FOOSH). Lateral elbow X-ray shows a displaced distal humeral fragment with an elevated triangular lucency posterior to the distal humerus, marked as **D** in the diagram. The posterior cortex is completely broken. What is the most appropriate immediate management after confirming neurovascular status and performing closed reduction?

Explanation

## Why Percutaneous K-wire fixation (CRPP) with 2 lateral pins and above-elbow cast for 4-6 weeks is right The elevated triangular lucency posterior to the distal humerus marked as **D** is the posterior fat pad sign ("sail sign"), indicating hemarthrosis from an occult or visible fracture. In this case, the completely broken posterior cortex indicates a Gartland Grade III supracondylar humerus fracture — the most common pediatric elbow fracture (peak age 3–10 years). Gartland III fractures (completely displaced with both cortices broken) require urgent closed reduction followed by percutaneous K-wire fixation (CRPP) with typically 2 lateral pins to maintain reduction and prevent complications like cubitus varus (gunstock deformity). The limb is then immobilized in an above-elbow cast for 4–6 weeks. This approach restores alignment, prevents malunion, and allows early mobilization once pins are removed (Gray's Anatomy 42e Ch 47; Apley 10e). ## Why each distractor is wrong - **Collar and cuff splint with early range of motion exercises**: This is appropriate only for Gartland Grade I (undisplaced) fractures. A completely displaced Grade III fracture requires operative fixation to prevent malunion and cubitus varus deformity. - **Open reduction and internal fixation with plate and screw fixation**: ORIF is reserved for irreducible fractures, neurovascular compromise not resolving with reduction, or failed closed reduction. Closed reduction with percutaneous pinning is the standard first-line approach for Gartland III fractures in children. - **Immobilization in 90° flexion for 3 weeks without operative intervention**: This conservative approach is only suitable for Gartland Grade I fractures. Grade III fractures are completely unstable and will malunite without operative fixation. **High-Yield:** Posterior fat pad sign (sail sign) on lateral elbow X-ray = hemarthrosis = occult or visible fracture; Gartland Grade III supracondylar fracture = urgent closed reduction + percutaneous K-wire fixation (CRPP), not conservative treatment. [cite: Gray's Anatomy 42e Ch 47; Apley 10e]