Acromial types

Last revised by Mohammad Taghi Niknejad ◉ on 11 Jun 2024

Citation, DOI, disclosures and article data

Citation:

Gaillard F, Niknejad M, Sharma R, et al. Acromial types. Reference article, Radiopaedia.org (Accessed on 18 Mar 2025) https://doi.org/10.53347/rID-842

DOI:

https://doi.org/10.53347/rID-842

Permalink:

https://radiopaedia.org/articles/842?embed_domain=hackmd.io%25252f%252540yipuafecsl2jsu8smr5njq%25252fbnjhjgjghjghjghfavicon.icofavicon.ico

rID:

842

Article created:

2 May 2008, Frank Gaillard ◉ ◈

Disclosures:

At the time the article was created Frank Gaillard had no recorded disclosures.

View Frank Gaillard's current disclosures

Last revised:

11 Jun 2024, Mohammad Taghi Niknejad ◉

Disclosures:

At the time the article was last revised Mohammad Taghi Niknejad had no financial relationships to ineligible companies to disclose.

View Mohammad Taghi Niknejad's current disclosures

Revisions:

30 times, by 18 contributors - see full revision history and disclosures

Systems:

Musculoskeletal

Sections:

Anatomy

Synonyms:

Acromion types
Types of the acromion
Bigliani classification of acromion types
Bigliani classification of acromion morphology
Bigliani classification

Acromial types were initially divided into three types (known as the Bigliani classification) ³, to which a fourth has been added ². These classifications are used as a standardised way of describing the acromion and predicting to a degree the incidence of impingement.

Classification

This classification was initially proposed by Bigliani et al. in 1986 on outlet view radiographs and later modified by Kitay et al. ⁷ and Vanarthos et al. in 1995, which remains the most widely accepted classification at the time of writing (2022).

Acromial morphology is variable on sagittal oblique MRI, depending on the slice position. A slice position just lateral to the acromioclavicular joint (no joint capsule or acromioclavicular ligament visible) is considered the single best slice ⁸.

Acromion morphology (types) are based on sagittal oblique MRI:

flat inferiorly (12%) ⁶
curved (56%)
- parallel to the humeral head with a concave undersurface
- down-sloping in the middle-third of the acromion ⁸
- considered the most common type ³
hooked (29%)
- most anterior portion of the acromion has a hooked shape
- down-sloping in the anterior-third of the acromion ⁸
- associated with increased incidence of shoulder impingement
convex (upturned) (3%)
- most recent classification of acromion process shape
- the undersurface of the acromion is convex near the distal end ⁴
- no convincing correlation between a type 4 acromion and impingement syndrome exists ^4,5