Causes / typical injury mechanism: Proximal humerus fractures involve the epiphysis, physis (growth plate), and/or metaphysis above the shaft of the humerus, close to the shoulder joint. Proximal humerus fracture patterns vary based on patient age and mechanism of injury. Pediatric fractures of the proximal humerus most commonly arise from sports injuries, motor vehicle accidents, and falls with direct or indirect trauma to the shoulder. In neonates, these fractures can result from rotation or hyperextension of the upper extremity during passage through the birth canal. In children aged younger than 2 years with normal bone density, metaphyseal humeral fractures can occur in cases of child abuse.

Classic history and presentation: The injury typically presents as severe pain, swelling, and functional impairment of the arm and shoulder. Physical findings may sometimes be limited to tenderness and mild swelling. For severely displaced fractures affecting nearby structures such as the axillary nerve, decreased sensation over the lateral shoulder and loss of deltoid muscle function may be seen.

Prevalence: Proximal humerus fractures in children account for approximately 2% of all pediatric fractures.

• Age – Peak incidence is between the ages of 11 and 15 years. Physeal fractures are more common in adolescents due to rapid growth and relative weakening of the physeal region compared to adjacent bone, whereas metaphyseal fractures are more common before adolescence.
• Sex / gender – These upper arm injuries occur 3-4 times more often in males than in females.

Risk factors: Risk factors include participation in high-contact sports such as football, rugby, and hockey, or activities involving fall risks from heights (eg, gymnastics, trampoline, downhill skiing, snowboarding). Vaginal delivery, breech presentation, prolonged labor, and macrosomia can predispose neonates to proximal humerus fractures resulting from birth trauma.

Grade / classification system:
Neer-Horowitz classification of pediatric proximal humerus fractures

• Grade 1: displacement less than 5 mm
• Grade 2: displacement less than one-third of shaft width
• Grade 3: displacement one-third to two-thirds of shaft width
• Grade 4: displacement more than two-thirds of shaft width