The piece of pie sign refers to an abnormal triangular appearance of the lunate on a PA image of the wrist representing either lunate dislocation or perilunate dislocation 1,2. A lateral image will help differentiate whether there is lunate or perilunate dislocation, with lunate dislocation demonstrating a spilled teacup sign. This is largely due to disruption of Gilula arcs and disruption of the spaces between the proximal and distal carpal bones.
- 1. Bridgeforth G, Cherf J. Lippincott's Primary Care Musculoskeletal Radiology. Lippincott Williams & Wilkins. (2010) ISBN:0781793777. Read it at Google Books - Find it at Amazon
- 2. Newberry JA, Garmel GM. Image diagnosis: perilunate and lunate dislocations. Perm J. 2012;16 (1): 70-1. - Free text at pubmed - Pubmed citation