AO classification of proximal humeral fractures

Last revised by Dr Joachim Feger on 21 Jul 2022

The AO/OTA classification together with the Neer classification is one of the most frequently used systems for classifying proximal humeral fractures. Like fractures in other bone segments, proximal humeral fractures are divided into three groups subject to the severity and complexity of the respective injury 1

In accordance with the Neer classification, the proximal humerus is divided into different parts and both the surgical neck and the anatomical neck form essential landmarks in the classification:

  • humeral head with the articular surface
  • metaphysis with greater tuberosity and lesser tuberosity
  • humeral shaft or proximal diaphysis

 The new AO/OTA 2018 classification compendium has replaced the old classification from 2007 2,3:

  • type A: extraarticular unifocal or 2-part proximal humeral end segment fracture
    • A1: unifocal tuberosity fracture
      • A1.1 greater tuberosity fracture
      • A1.2 lesser tuberosity fracture
    • A2: surgical neck fracture
      • A2.1 simple surgical neck fracture
      • A2.2 wedge fracture of the surgical neck 
      • A2.3 multifragmentary surgical neck fracture
    • A3: unifocal vertical metaphyseal extraarticular fracture
  • type B: extraarticular bifocal or 3-part proximal humeral end segment fracture
    • B1: extraarticular bifocal 3-part fracture surgical neck fracture *
      • B1.1 surgical neck with greater tuberosity fracture
      • B1.2 surgical neck with lesser tuberosity fracture
  • type C: multifocal, 4-part or articular proximal humeral end segment fracture
    • C1: anatomical neck fracture
      • C1.1 valgus impacted anatomical neck fracture**
      • C1.3 isolated anatomical wedge fracture
    • C3: anatomical neck with metaphyseal fracture
      • C3.1 multifragmentary metaphyseal segment but with an intact articular surface
      • C3.2 multifragmentary metaphyseal segment and fractured articular surface ***
      • C3.3 multifragmentary metaphyseal segment, articular fracture and diaphyseal extension ***

*  applies for an intact or fragmentary wedge but this should be specified

** applies for the greater tuberosity, the lesser tuberosity or both tuberosities

*** applies for simple or multifragmentary articular fractures

The AO/OTA classification seems to be slightly less reliable and reproducible than the Neer classification but is ascribed a substantial descriptive power. It also seems to simplify the coding process 2.

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