hyperextension load on the elbow The extension supracondylar fracture accounts for 95% of these injuries and is often described using the Gartland classification system ( Table 111.5 ) Less commonly, a direct fall onto the flexed elbow results in an anterior displacement of the distal fragment The FOOSH mechanism causes the ulna and triceps muscles to exert an unopposed force on the distal humerus, causing failure of the anterior periosteum and, in more severe injuries, extending to and through the posterior cortex This progression results in a posterior displacement of the condylar complex Displacement of the fracture increases the risk of injury to the brachial artery and the median, radial, and ulnar nerves as the neurovascular bundles are stretched and/or disrupted Obesity in childhood and adolescence reduces bone mineral density with an increased propensity for fractures This can be associated with more complex supracondylar humeral fractures, preoperative and postoperative nerve palsies, and postoperative complications FIGURE 111.15 A: Anteroposterior radiograph of a normal elbow of a child B: Normal lateral radiograph Clinical Considerations Clinical recognition A child with a supracondylar fracture often presents to the ED holding the arm straight in pronation and refusing to use the arm or flex at the elbow Supracondylar fractures occur most commonly between and 10 years