TFCC, DRUJ Instability, and Ulnar Variance on MRI and CT

In ulnar-sided wrist pain, a TFCC lesion and distal radioulnar joint instability are not the same finding. MRI depicts the disc, foveal and styloid attachments, and associated bone and tendon abnormalities. CT helps assess radius-ulna alignment, particularly with contralateral and standardized forearm-position comparisons.

DRUJ translation changes with forearm rotation, and small side-to-side differences occur in asymptomatic people. Do not diagnose subluxation from one axial image. Joint surfaces, sigmoid-notch morphology, clinical instability, and standardized positioning must be considered together.

Assessment framework

• Measure ulnar variance on an appropriately positioned neutral-rotation PA radiograph.
• Inspect the TFCC central disc and foveal and styloid attachments.
• Assess DRUJ fluid, synovium, and distal ulnar marrow.
• Review the extensor carpi ulnaris groove, subsheath, and tendon.
• On CT, compare both sides in matched pronation, neutral, and supination positions.

What the report should contain

• State whether a tear is central or peripheral and which surface it reaches.
• Call out loss of the foveal attachment specifically.
• Look for lunate and triquetral chondral or marrow findings of ulnar impaction.
• Interpret DRUJ alignment with position and the contralateral side.
• Record prior surgery and hardware artifact as technical limitations.

Common errors

• Calling TFCC signal a full-thickness tear by itself.
• Measuring ulnar variance on an oblique radiograph.
• Reporting normal rotational translation as pathologic subluxation.

Example report wording

Example impression: Fluid-signal separation is present at the foveal TFCC attachment with a distal radioulnar joint effusion. The central disc remains intact. On neutral-position CT, dorsal translation of the ulnar head is greater than on the contralateral side. In the presence of clinical instability, the findings support DRUJ instability related to a foveal TFCC tear.

Use the distal radioulnar joint anatomy guide for the underlying bone and ligament landmarks.

References

1. European Radiology. Consensus statements on imaging of DRUJ instability and TFCC injuries. Source (opens in a new tab)
2. RadioGraphics. Distal Radioulnar Joint: Normal Anatomy and Imaging of Common Disorders. Source (opens in a new tab)

Clinical note: This material is for radiology education. Do not generate an automatic diagnosis or management decision without checking guideline scope, patient factors, and local policy.