Perilunate Dislocation

The perilunate dislocation results from a backwards fall on an extended hand which disrupts the scaphoid ligaments. The capitate is dorsally located relative to the lunate. The lunate bone maintains its normal relationship with the radius.
A PA radiograph of the wrist. This demonstrates the abnormal relationship between the scaphoid and lunate bones.

B Lateral radiograph of the wrist. This shows the normal relationship of the lunate relative to the radius but there is dorsal displacement of the capitate bone.

Links to online textbooks

Wheeless' Orthopedics: discussion of perilunate dislocations

References:

Niazi TB: Volar perilunate dislocation of the carpus: a case report and elucidation of its mechanism of occurrence Injury. 1996 Apr;27(3):209-11. [See related articles]
Meldon SW, Hargarten SW: Ligamentous injuries of the wrist J Emerg Med. 1995 Mar-Apr;13(2):217-25. [See related articles]

A	PA radiograph of the wrist. This demonstrates the abnormal relationship between the scaphoid and lunate bones.
B	Lateral radiograph of the wrist. This shows the normal relationship of the lunate relative to the radius but there is dorsal displacement of the capitate bone.