Crescent sign
Inradiology,thecrescent signis a finding on conventionalradiographsthat is associated withavascular 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 curvedsubchondralradiolucentline that is often found on the proximalfemoralorhumeralhead.[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 thenecroticand repair processes that occur during avascular necrosis.[1][2]Osteosclerosisoccurs at a margin where new bone is placed over deadtrabeculae.[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 shearfractures.[1]
References
[edit]- ^abcdefghiPappas, J. N. (2000). "The musculoskeletal crescent sign".Radiology.217(1): 213–214.doi:10.1148/radiology.217.1.r00oc22213.PMID11012446.
- ^abKenzora, J. E.; Glimcher, M. J. (1985). "Pathogenesis of idiopathic osteonecrosis: The ubiquitous crescent sign".The Orthopedic Clinics of North America.16(4): 681–696.doi:10.1016/S0030-5898(20)30435-1.PMID4058896.
- ^Norman, A.; Bullough, P. (1963). "The Radiolucent Crescent Line--An Early Diagnostic Sign of Avascular Necrosis of the Femoral Head".Bulletin of the Hospital for Joint Diseases.24:99–104.PMID14048829.
- ^"Rheumatology Image Bank: Avascular Necrosis, Crescent Sign: Ficat Stage III, Hip".Retrieved26 June2012.