Codman (1934) proposed the concept of dividing the proximal humerus into four fracture segments.

It roughly divides the proximal humerus into four parts: the anatomical head, greater tuberosity, lesser tuberosity, and humeral shaft epiphysis, based on the line of closure of the epiphysis. All different types of fractures are the result of various combinations of these four segments.

Codman's concept of dividing the fracture segments into four parts laid the foundation for the internationally recognized Neer classification system.