What is the shoulder pad sign and what does it have to do with this case?

This is a 52-year-old with a swollen shoulder. What is the shoulder pad sign? What’s your diagnosis for this case?

Coronal water-weighted

The shoulder pad sign is associated with clinical shoulder swelling bilaterally in amyloid arthropathy of the shoulders. This is not amyloid. It is synovial chondromatosis of the subdeltoid bursa. There are primary and secondary varieties. The secondary type usually occurs with chronic inflammation of osteoarthritis. The primary type most likely results from a mutation, and, unlike the secondary type, may dedifferentiate into a malignant chondrosarcoma on rare occasions.

Synovial chondromatosis is one of the synovial metaplasias. The others include:

  • Synovial osteochondromatosis
  • Villonodular synovitis
    • Focal
    • Diffuse
  • Pigmented villonodular synovitis
    • Focal (also called focal giant cell tumor of tendon sheath)
    • Diffuse
  • Lipoma arborescens
  • Synovial hemangiomatosis

For more shoulder case review, head to MRI Online.

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