AO classification of proximal humerus fractures:

• A: extra-articular unifocal fracture
  • A1: extra-articular unifocal tuberosity fracture
  • A2: extra-articular unifocal nondisplaced metaphyseal fracture
  • A3: extra-articular unifocal displaced metaphyseal fracture
• B: extra-articular bifocal fracture
  • B1: extra-articular bifocal fracture with impacted metaphysis
  • B2: extra-articular bifocal fracture without impacted metaphysis
  • B3: extra-articular bifocal fracture with dislocated glenohumeral joint
• C: articular (anatomical neck fracture)
  • C1: minimally displaced
  • C2: markedly displaced
  • C3: dislocated