Supra-acetabular fossa
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At the time the article was created Andrew Dixon had no recorded disclosures.
View Andrew Dixon's current disclosuresAt 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- 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
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Differential diagnosis
osteochondral defect: symptomatic, marrow reaction, cartilage loss, rare in the acetabulum
-
other acetabular variants
References
- 1. Dietrich TJ, Suter A, Pfirrmann CW et-al. Supraacetabular fossa (pseudodefect of acetabular cartilage): frequency at MR arthrography and comparison of findings at MR arthrography and arthroscopy. Radiology. 2012;263 (2): 484-91. Radiology (full text) - doi:10.1148/radiol.12111397 - Pubmed citation
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