Scallop sign - rheumatoid arthritis

Case contributed by Samir Benoudina
Diagnosis certain

Presentation

A known case of rheumatoid arthritis.

Patient Data

Age: 40 years
Gender: Female
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Info

In addition to the erosive changes and periarticular osteoporosis routinely seen in rheumatoid arthritis, there is an erosion of the radial side of the distal radioulnar joint; known as the "scallop sign".

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Info

Erosion of the radial side of the DRUJ; the scallop sign.

Case Discussion

The scallop sign is the term used to describe the scooped-out appearance of the sigmoid notch of the distal radius that results from synovial proliferation and bone erosion of the distal radioulnar joint. It is characterized by a sclerotic border indicating slow development.

According to Freiberg et al, the scallop sign correlates with a high risk for extensor tendon rupture 1.

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