Proximal humerus fractures are the third most common fracture type in individuals older than 65 years, after distal radius and proximal femur fractures. In 1970, Charles Neer described his four-segment classification system [18]. He believed the existing classifications were inadequate for research purposes, as they did not differentiate between injuries of varied severity nor did they group like fractures. The classification systems at that time were based on the mechanism of injury or level of the fracture line, but did not consider many surgically important aspects or pathologic features of injury such as tuberosity displacement. Forty years later, surgeons continue to use Neer’s four-segment fracture classification system for proximal humerus fractures because it is useful in guiding treatment, grouping similar fracture patterns for research purposes, and explaining pathologic features of injury.