Crescent sign
In
radiographs that is associated with avascular necrosis.[1][2][3] It usually occurs later in the disease, in stage III of the four-stage Ficat classification system.[1] It appears as a curved subchondral radiolucent line that is often found on the proximal femoral or humeral head.[1] Usually, this sign indicates a high likelihood of collapse of the affected bone.[1] The crescent sign may be best seen in an abducted (frog-legged) position.[1][4]
The crescent sign is caused by the
trabeculae.[1] When the trabeculae experience stress leading to microfractures and collapse, the crescent sign appears.[1]
The crescent sign may be seen with other bone diseases, such as shear fractures.[1]
References
- ^ PMID 11012446.
- ^ PMID 4058896.
- PMID 14048829.
- ^ "Rheumatology Image Bank: Avascular Necrosis, Crescent Sign: Ficat Stage III, Hip". Retrieved 26 June 2012.