AO classification of distal femur fractures

Last revised by Andrea Molinari on 26 Feb 2024

Citation, DOI, disclosures and article data

Citation:

Murphy A, Molinari A, Ng J, AO classification of distal femur fractures. Reference article, Radiopaedia.org (Accessed on 16 Apr 2024) https://doi.org/10.53347/rID-94057

DOI:

https://doi.org/10.53347/rID-94057

Permalink:

https://radiopaedia.org/articles/94057

rID:

94057

Article created:

17 Oct 2021, Andrew Murphy ◉

Disclosures:

At the time the article was created Andrew Murphy had no recorded disclosures.

View Andrew Murphy's current disclosures

Last revised:

26 Feb 2024, Andrea Molinari ◉

Disclosures:

At the time the article was last revised Andrea Molinari had no financial relationships to ineligible companies to disclose.

View Andrea Molinari's current disclosures

Revisions:

4 times, by 3 contributors - see full revision history and disclosures

Systems:

Musculoskeletal

Sections:

Classifications

Synonyms:

AO classification of distal femoral fractures
OTA classification of distal femoral fractures

The AO classification of distal femoral fractures is one of the commonly used fracture classification systems in orthopedics.

Each long bone has a single number with the parts of the bone denoted numerically, the proximal end is 1, diaphysis is 2, and the distal end is 3.

The distal femur system's prefix is 33, indicating it is the femur (3) and the distal portion of the femur (3).

The AO classification divides the distal femoral fractures into three groups, A, B and C with complexity and severity increasing 1.

type A: extra-articular
- A1: avulsion
- A2: simple
- A3: wedge or multifragmentary
  - A3.1 intact wedge
  - A3.2 fragmentary wedge
type B: partial articular, the fracture is involving one part of the articular surface, yet the rest of the joint is still attached to the metaphysis and diaphysis
- B1: lateral sagittal
  - B1.1 through the notch
  - B1.2 through load-bearing lateral condyle
  - B1.3 sagittal fragmentary
- B2: medial sagittal
  - B2.1 through the notch
  - B2.2 through load-bearing medial condyle
  - B2.3 sagittal fragmentary
- B3: frontal/coronal
  - B3.1 anterior and lateral flake fracture
  - B3.2 unicondylar posterior
  - B3.3 bicondylar posterior
type C: complete articular, the fracture is distributing the joint surface and separated from the diaphysis
- C1: simple articular
  - C1.1 above transcondylar axis
  - C1.3 through or below transcondylar axis
- C2: simple articular with a fragmentary metaphyseal component
  - C2.1 intact metaphyseal wedge
  - C2.1 fragmentary metaphyseal wedge
- C3: multifragmentary articular
  - C3.1 simple metaphyseal
  - C3.2 wedge metaphyseal
  - C3.3 metaphysio-diaphyseal multifragmentary