Multiple images of navicular disorientation with dislocation of the scapholunate joint. The scaphoid bone, seen along it long axis, has a ringed cortex appearance. The cortical ring sign is a sign of scapholunate dislocation, and it was first described in 1970 in a young patient with bilateral dislocation of the carpal naviculars. This sign, also known as the signet-ring sign, is caused by the abnormal orientation of the scaphoid.
Reference
Crittenden JJ, Jones DM, Santarelli AG: Bilateral rotational dislocation of the carpal navicular. Radiology 1970, 94:629-630.
