Anderson and Montesano classification of occipital condyle fractures

Last revised by Francis Deng ◉ on 18 Jan 2022

Citation, DOI, disclosures and article data

Citation:

Hacking C, Deng F, Anderson and Montesano classification of occipital condyle fractures. Reference article, Radiopaedia.org (Accessed on 05 Jun 2023) https://doi.org/10.53347/rID-87202

DOI:

https://doi.org/10.53347/rID-87202

Permalink:

https://radiopaedia.org/articles/87202

rID:

87202

Article created:

23 Feb 2021, Craig Hacking ◉ ◈

Disclosures:

At the time the article was created Craig Hacking had no recorded disclosures.

View Craig Hacking's current disclosures

Last revised:

18 Jan 2022, Francis Deng ◉

Disclosures:

At the time the article was last revised Francis Deng had no recorded disclosures.

View Francis Deng's current disclosures

Revisions:

8 times, by 2 contributors - see full revision history and disclosures

Systems:

Head & Neck, Musculoskeletal, Spine, Trauma

Sections:

Classifications

Synonyms:

Anderson-Montesano classification of occipital condyle fractures

The Anderson and Montesano classification is a widely used system for describing occipital condyle fractures. It divides injuries into three types based on morphology and mechanism of injury ^1-5.

type I: impacted type occipital condyle fracture
- morphology: comminution of the condyle with minimal or no displacement of fragments into the foramen magnum
- mechanism: axial loading of the skull onto the atlas
- stability: stable because the tectorial membrane and contralateral alar ligament are intact (the ipsilateral alar ligament may be functionally inadequate)
type II: basilar skull type occipital condyle fracture
- morphology: condyle fracture that extends outside of the condyle to elsewhere in the posterior base of skull
- mechanism: direct blow to the lower skull
- stability: stable because the tectorial membrane and alar ligaments are intact
type III: avulsion type occipital condyle fracture
- morphology: small inferomedial occipital condyle fracture fragment displaced toward the odontoid tip
- mechanism: rotation and/or contralateral bending
- stability: potentially unstable due to loading of the contralateral alar ligament and tectorial membrane

Epidemiology

A range of incidences of the Anderson and Montesano types amongst all occipital condyle fractures has been reported ^2,4,6:

type I: 3-13%
type II: 22-54%
type III: 33-75%

History and etymology

The classification was described in 1988 by American orthopedic surgeons Paul A. Anderson and Pasquale X. Montesano on the basis of 6 patients diagnosed by conventional anterior posterior polytomography or CT with coronal reconstructions ¹.