A 7-year-old boy presents to the emergency department after a fall on an outstretched hand (FOOSH) while playing. Radiographs confirm a supracondylar fracture of the humerus. Which of the following is the most common mechanism of injury in supracondylar fractures of the humerus?

## Mechanism of Supracondylar Fracture **Key Point:** Fall on outstretched hand (FOOSH) with the elbow in extension is the most common mechanism of injury in supracondylar fractures, accounting for approximately 90% of cases. ### Biomechanics When a child falls with the arm outstretched and the elbow extended, the force is transmitted through the wrist and forearm to the distal humerus. The supracondylar region, being the weakest point of the humerus in children (due to the presence of the supratrochlear ossification center and relative weakness of the bone at this junction), fractures first. ### Age Group Affected - **Peak incidence:** 5–8 years of age - **Reason:** Relatively weak supracondylar bone in this age group; ossification centers not yet fully fused ### Classification Context The Gartland classification divides supracondylar fractures by displacement: | Type | Displacement | Frequency | |------|--------------|----------| | Type I | Minimal/non-displaced | ~50% | | Type II | Posterior angulation, intact posterior cortex | ~35% | | Type III | Complete displacement, no cortical contact | ~15% | **High-Yield:** Type II and III fractures are the ones requiring urgent reduction due to risk of neurovascular compromise. ### Clinical Pearl The FOOSH mechanism with elbow extension is so common that if a child presents with a supracondylar fracture from a different mechanism (direct blow, flexion injury), one should suspect non-accidental trauma or an underlying bone pathology. **Warning:** Flexion injuries and direct blows are rare causes and should raise suspicion for abuse or pathological fractures.