The Neer classification system is useful to characterize proximal humerus fractures and determine the need for emergent orthopedic follow up. Fractures occur at 4 different sites: surgical neck, anatomical neck, greater tuberosity, lesser tuberosity.

One-part fractures include fractures at any of these sites, that are not displaced (> 1cm) or angulated (>45 degrees). One-part fractures account for 80% of all proximal humerus fractures.

A two-part fracture is one displaced or angulated fracture line.

A three-part fracture includes a displaced fracture of the surgical neck plus a displaced fracture of the greater tuberosity (in this case) or lesser tuberosity. 

A four-part fracture includes a displaced surgical neck plus a displaced greater tuberosity and displaced lesser tuberosity.