Test your knowledge: abnormal finding in hip radiograph
Is there something you would not expect in this radiological picture of the hip joint and that can be classified as abnormal?
(Image taken from: openi.nlm.nih.gov)
The abnormal radiological finding is an os acetabula and it can cause long lasting hip pain. It is an ossicle located at the acetabular rim, first described by Ponseti in 1978 as a secondary ossification center of the acetabulum. In some patients, the os acetabula remains unfused even in adulthood, resulting in an os acetabuli.
Distinguishing between an os acetabuli and a fracture is important, since some authors consider this to be a fatigue fracture due to overload. Differentiation of diagnosis has to be done by radiographic evaluation.
Below some other differential diagnoses that could be found at the acatebular rim and may be misdiagnosed:
- Unfused secondary ossification center;
- Fatigue fracture due to stress overload (FAI morphology);
- Acute acetabular rim fracture (Trauma);
- Ossification of the labrum;
- Fractured rim osteophyte;
- Adhesed loose body to the acetabular rim.
Click here to read more into hip radiology in a free available textbook chapter! (> From: Domb & Botser. Loose bodies: Tips and pearls. Springer science; 2012)