Various fracture classification systems were proposed during the first half of the twentieth century. Some were based on the anatomical fracture level, while others on the underlying trauma mechanism deduced from the radiographical pattern. Between 1953 and 1967, Charles Neer collected 300 cases of patients treated under anesthesia at his institution. He developed a classification system by correlating the initial radiographs with intraoperative findings. Neer’s system integrated pathoanatomy and biomechanics in an ordinal system within the framework of Codman’s four-part approach. His work also introduced a definition of displacement still in clinical use today. The AO classification system was published in 1987 and combined a standardized classification of long bone fractures with specific pathoanatomical patterns of the proximal humerus. Both classification systems have been criticized for their lack of agreement within and between observers, lack of ordinality, and inability to provide individualized treatment recommendations and prognosis for each category.