Supra-acetabular fossa

Last revised by Daniel J Bell on 6 May 2024

Citation, DOI, disclosures and article data

Citation:

Dixon A, Bell D, Knipe H, et al. Supra-acetabular fossa. Reference article, Radiopaedia.org (Accessed on 11 May 2024) https://doi.org/10.53347/rID-24422

DOI:

https://doi.org/10.53347/rID-24422

Permalink:

https://radiopaedia.org/articles/24422

rID:

24422

Article created:

14 Aug 2013, Andrew Dixon ◉

Disclosures:

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

View Andrew Dixon's current disclosures

Last revised:

6 May 2024, Daniel J Bell ◉

Disclosures:

At the time the article was last revised Daniel J Bell had no financial relationships to ineligible companies to disclose.

View Daniel J Bell's current disclosures

Revisions:

9 times, by 7 contributors - see full revision history and disclosures

Systems:

Musculoskeletal

Sections:

Anatomy

Tags:

hip, acetabulum, anatomic variant, anatomy, refs

Synonyms:

Pseudodefect of acetabular cartilage
Supra-acetabular fossae
Supra-acetabular fossas

A supra-acetabular fossa (plural: fossae), also known as pseudodefect of acetabular cartilage, is an anatomic variant whereby a focal defect is evident within the subchondral bone of the acetabular roof. It is seen in as many as 10% of hips and is typically located at the 12 o'clock position both in the coronal and sagittal planes.¹

While it can at first appear like an osteochondral defect on imaging studies, at arthroscopy or on 3 T MRI, cartilage can be seen to overlie the subchondral bone. Unlike an acquired osteochondral defect, a supra-acetabular fossa does not induce any adjacent marrow reaction or symptoms.

A type 1 fossa is one where hyaline cartilage incompletely fills the depth of the fossa and hence contrast or fluid is seen within. A type 2 fossa is one that is completely filled with cartilage and, therefore, is not directly identifiable on arthroscopy or arthrography.¹

A study in 2012 confirmed arthroscopically that all supra-acetabular fossae were covered by cartilage. Of all hips studied, 1.6% had type 1 and 8% had type 2 supra-acetabular fossae. This study also suggested that there may be evolution with aging from type 1 to type 2 as cartilage remodeling occurs.¹