What is the unusual anatomic variant in this wrist case?

This 29-year-old male presented with a traumatic injury of the left palmar wrist. What anatomic variant seen in this patient must be taken into account?

Ulnar-sided pain in this case can be attributed to:

  • ECU tenosynovitis, tendinosis, and longitudinal partial-thickness tearing (images 3 and 4, arrows).
  • ECU subsheath inflammation (horizontal arrow-image 3).
  • Peripheral TFCC attachment sprain/swelling distal to ulna (image 4).

As for the unusual anatomic variant, this case is an example of an extensor digitorum brevis manus, which is indicated by the arrows in images 1 and 2. For more case review, visit MRI Online.

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