Complete palmar dislocation of the lunate in rheumatoid arthritis. Avascularity without avascular changes.

We report a case of complete palmar dislocation of the lunate in a rheumatoid patient. X-rays showed a normal bone structure of the lunate without sclerosis or collapse and on MRI an almost normal signal intensity was found. The lunate was removed. Histological examination showed complete necrosis of both marrow and bone cells, and tetracycline labelling showed no fluorescence. This case illustrates that neither X-ray nor magnetic resonance imaging (MRI) can detect complete bone necrosis. When X-ray or MRI changes do occur, these are indications of cellular events following some degree of spontaneous revascularization.